Background of the Invention

Molded plastic parts have become increasingly popular, due at least in significant part to their low production cost. Hence, often, one or more components of an assembly are formed of molded plastic. In assembling a final product it is often necessary to fasten the molded plastic parts to other components to produce the final product.

Current production methods for fastening components to a plastic part of low ductility include forming a threaded recess in the plastic part, which serves as a base, and into which a threaded member or fastener is screwed. This has been found to be undesirable in several respects. The brittle nature of polycarbon and other plastics employed makes it difficult to cut threads in the polycarbon base for receiving the threaded member. During thread formation, the brittle polycarbon base material has been found to crack and chip, often making insertion of the threaded fastener difficult or impossible. Also, the chipping reduces the bearing surface area against which the threads of the fastener bear against the base to preclude the fastener from being pulled out of the base. Thus, the load bearing capacity of the threaded member is significantly reduced.

Due to the aforementioned difficulties associated with pre-threading brittle plastic base materials, other, less desirable, fastening means have been employed. One such alternative fastening means attempted has been to employ a self-threading screw. However, the brittle nature of the plastic base material precludes the formation of a consistent thread therein, with a resultant cracking of the base.

Alternatively, internally threaded metal inserts, have been molded to the base, with the threaded fastener

then screwed into the internal threads of the metal insert. However, due to the inherent incompatibility of metals and plastics, the bond therebetween has been found inadequate to maintain bonding of the metal insert to the plastic base when the metal insert is pulled with significant force. Bonding of the metal insert is attained by providing the metal insert with grooves, ridges or knurls and bringing the base plastic to a flowable state whereby the base plastic flows into the grooves, ridges or knurls of the insert. Accordingly, the strength of the bond is only derived from the base plastic, and limited thereby. Hence, upon imposition of significant forces pulling on the metal insert, the insert is pulled from the base, together with any threaded member screwed into the insert. Additionally, formation of the metal inserts adds considerable expense to the overall production cost.

One method currently employed for fastening components to the base which provides the desired bonding strength is a conventional screw and nut assembly. However, this is undesirable in several respects. Functionally, the screw and nut assembly loosens over time, resulting in a loose connection between components. Also, aesthetically, screw and nut assemblies are undesirable due to the requirement of a provision for accommodating the nut or the nut being exposed on one end of the base, rather than allowing for employment of a blind tapping which provides superior aesthetics. Furthermore, the requirement of the metal nut adds undesirable cost to production.

There is a need for eliminating the driving of a metal fastener into the plastic base. This operation of driving the metal fastener requires assembly time and the use of labor. Overall production efficiency could be obtained by eliminating a tapping of a thread into a plastic base and/or the driving of a fastener into the thread in the plastic base. In its preferred form the

invention allows elimination of the driving of the fastener into the plastic base thereby increasing overall efficiency in mounting components to a plastic base with a metal threaded fastener. Also, there is a need to join together plastic bodies such as two plastic components or a pair of plastic sheets or plates with one or more plastic fasteners. While metal fasteners may be used as above- described, there are times when it is desired not to use metal and still join plastic parts or components together to form a composite of the two joined parts. In such instances, it is preferred that the plastic fastener form a strong, secure connection that will not readily loosen as may a plastic screw that is threaded into the parts to join them together. Preferably, the plastic fastener should bond the two plastic bodies together much in the manner that of an integral bond therebetween.

The present invention is also of particular use to molders of plastic parts, such as molded plastic shells or molded plastic bodies that have cylindrical protrusions or bosses thereon to create an attachment area for a screw or other fastening means to secure one body to another body or to a supporting frame, or to attach other elements to the molded plastic body. For example, in the automotive industry, dashboards are molded from plastic with an exterior shell that has the same outside appearance but on the inside, has different bosses to receive screws or other fasteners to secure different instruments which vary depending on the model and/or the instrument options selected by the purchaser. Currently, the automotive company and the molder have one mold for each of the options; and this may result in twenty or more molds to accommodate each internal change of the bosses or reinforcing thick portions on the plastic shell body which has the same outward appearance. The injection molding of these thick portions or bosses is a time-limiting factor on the molding process

because the time needed for the plastic to solidify before part ejection is usually determined by the thickness of the plastic cross-section, and it takes longer to solidify the thicker bosses than the thin shell cross-section.

Also, in a mold, the boss configuration is the highest wear part of the molding die. A pin which is commonly called a core pin is inserted in the center of the boss to create an attachment area for a screw or other method of attaching the shell. This pin is nominally tapered and must be closely controlled because of the amount of pressure and friction the pin must withstand. The pin is normally the highest wear point of the mold and requires the most rework and replacement. Additionally, strength requirement for the boss may determine what plastic is used for the shell because the strength needed for the bosses used for affixing the shell to another shell or to another part or frame or to mount other elements may outweigh other considerations. That is, the product may be molded with more or larger bosses or higher strength plastic materials than the shell requires in order to provide the strength to the bosses to interconnect the shell with other parts. Additionally, some products that are now molded with integral plastic bosses, e.g., integrated circuit boards or the like, could be made less expensively from plastic flat sheet stock with subsequently attached bosses.

The present invention is of particular use to molders of plastic parts, such as molded plastic shells or bodies, who desire to attach another plastic member to the body and/or to assemblers who desire to attach a first plastic material member to a second plastic material member. The present invention will be described in connection with an illustrated embodiment wherein a hollow, plastic container e.g., made of polyethylene terephthalate (PET) plastic has a thin wall to which it is desired to secure a separate handle e.g., of PET or of

a polycarbonate plastic in the shape of a loop, but is not -limited to these examples. When lifting or pouring liquid from the container, the user may insert his fingers into the loop and grip the outer portion of the loop. When making such containers it may be desirable to be able to use handles of a different thickness or a shape that would be difficult to mold integrally with the container or of a different material than the container material. Some plastics such as PET are most desirable for containers, such as bottles or drinking cups, because of its clarity, crystalline appearance, toughness, etc.; but PET may be a difficult material to which to attach handles when using conventional attaching techniques. The present invention is not limited to PET material because for many other plastic objects, such as for the PET container piece, it is desired to provide a good attachment between the first plastic piece and a second plastic piece such as a handle. While ultrasonic welding of plastic pieces together is well known, the piece shapes are not specifically designed to direct or concentrate the ultrasonic energy to achieve the initial energy direction and concentration to cause a good integral band between the pieces. In these instances, one will find the PET plastic is usually not directly molded into its final shape by an injection molding as are many other containers such as, for example, polyethylene plastic containers. Rather, the PET plastic is first injection molded into a small preform which is then blown into the final enlarged container shape. With such preforms, often it is not economically feasible to have a handle thereon to be blown into a larger size or to attach a separate handle thereto using conventional techniques. Often for larger sizes of PET containers, e.g., a three liter container, it is desirable to attach a handle to this with plastic containers.

The present invention is also directed to applications where, heretofore, one or more plastic

pieces have been secured together by metallic screws and it is desirable to eliminate the metallic screws and to secure the members together using an improved plastic fastening system. In other instances, pieces have been heat staked together and it is desired to replace heat staking of components together with a better plastic system than a heat staking system.

Bolts are typically formed of a metal material with a head at one end and a screw thread on the other. An internally threaded nut formed of a metal material can be mounted on the threaded bolt end. The bolt and nut combination can be used to fasten objects together with the bolt being passed through clearance holes in two or more parts and the nut engaged on the threaded end to draw the parts together.

Such a bolted assembly forms a temporary connec¬ tion in that the nut can be removed from the bolt shank to release the parts. Accordingly, this threaded-type fastener is used to form a connection that can be dis- assembled and reconnected and that must resist tension and shear forces that may be applied to the fastened parts. The nut is tightened on the bolt such that the bolt head and nut exert a clamping force on the parts fastened thereby. The nut must be tightened on the bolt with sufficient torque to produce a pre-load tension in the bolt so that during vibration, the relative stress change is slight with consequent improved fatigue resistance and locking of the nut. The clamping force produced by the pre-loading also increases the friction between the inner bearing surfaces of the members so that shear loads are carried by the friction forces rather than by the bolt. To enhance the pre-load, oftentimes lock washers are used on the bolt shank between the nut and the fastened members. Thus, a temporary bolted connection primarily derives its fastening ability from the amount of torque placed on the nut to clamp the members between the nut

and bolt head. To increase such torque, special torque wrenches and power tools have been developed to apply high levels of torque to the nut as it is screwed on the bolt shank in engagement with an adjacent fastened member. To engage and turn the nut or bolt head with the other clamped in place against removable sockets rotation, wrenches typically have adjustable jaws or use removable sockets and power tools can use socket sleeves which mate with the nut. None of these are particularly satisfactory for assembly operations, especially when the parts being assembled utilize small nuts and bolts for space savings, such as in electronic equipment, where the size requires highly precise positioning and operation of the torquing tool while simultaneously avoiding contact with surrounding components. To apply torque to the nut, the bolt head must be clamped against rotation, again requiring enough room and time for a clamping or holding tool to be employed. In addition, where power tools are incorporated in automated assembly operations, the space required for mechanical power transmission systems for applying torque can be significant.

One important application of the inventive fasteners herein is with printed circuit boards as the use of metallic nuts and bolts in electronic equipment employing printed circuit boards can cause problems as described below. Where the nut and bolt are formed from metal material and are used to secure printed circuit boards in equipment housings, such as to mounting brackets or the like, or where the nut and bolt are used to secure several printed circuit boards in spaced relation to each other in a stack, the board typically has mounting holes drilled in peripheral positions on the board away from the circuit pattern and elements thereon so as not to interfere with the conductor paths of the circuit. This can be a significant limitation on the use of metal fasteners in electronic devices, particularly where space savings are important, as it reduces

flexibility in design of the mounting arrangements for printed circuit boards. The torque required to produce the necessary clamping force and pre-load tension on the bolt to lock the nut thereon can cause the bolt head and nut to damage the protective coatings used on the parts to be fastened. Where the coated parts are metallic, damaged coatings can provide sites for corrosion to begin. With printed circuit boards, their coatings can provide both mechanical support to the connections thereon and environmental protection to the circuitry components and, accordingly, any damage thereto is undesirable.

To improve the durability and strength of fastened connections, assemblies are provided utilizing permanent fasteners, such as rivets and welds, to transfer loads. To permanently assemble parts using rivets, a rivet having a pre-formed head on one end is inserted through aligned holes in two or more parts to be joined and then by impacting and pressing the protruding end, a second head is formed to hold the parts together permanently. Parts can also be permanently fastened by welding where interengaging portions of the parts and/or a filler are heated until they coalesce, with the heat then removed to allow the liquid to solidify to join or weld the parts together. For smaller parts, soldering guns or irons can be used to connect components as on circuit boards. The heat source for welding larger metal parts is typically a welding gun or torch which produces an electric arc or a direct flame. Once such a permanent connection is achieved as by riveting or welding, it is extremely difficult and time consuming for the connection to be broken for disassembly of the parts. With welding, portions of the parts themselves typically will be integrally bonded with each other and/or filler material as with soldering.

Subsequent separation at the welded joint can damage or destroy those portions of the parts that were welded

compromising their integrity to the point that they are no longer useful for theiir desired purpose. Temporary connections produced by conventional screw fasteners are also undesirable in that the threaded nut and bolt assembly can loosen over time, particularly under prolonged exposure to vibration and shear forces resulting in a loose connection between attached components. With computers and printed circuit boards being incorporated into automobiles, aircraft and other industrial equipment, exposure to vibration and shock stresses are not unusual and loosening of the attachments can cause serious problems in the electronic equipment utilized and lead to malfunction of any operating systems they may control. Thus, there is a need for a new fastening method and a fastener which can provide a secure and strong clamping force to attach parts, while also allowing the parts to be readily disassembled from each other. The nut and bolt fastener should be easily and quickly applied to attach parts without having to apply and rely on torque forces to achieve a secure connection. In the application of the fastener, the clamping force exerted by the nut and bolt head preferably should not cause damage to the parts. The fastener should provide a connection similar to that provided by fasteners which permanently attach parts while at the same time allowing the fastener to be removed from the parts so that they can be disassembled in their original state without any damage thereby allowing for their reuse and reassembly, if desired.

Summary of the Invention

In accordance with the present invention, two plastic pieces are joined together by providing energy directing protrusions on a first plastic piece and exerting a force between the protrusions and the second plastic piece and applying ultrasonic energy which is

directed to and concentrates at protrusions to create localized heat to melt them quickly. The plastic of the second piece in forced engagement with the melting protrusion also melts more quickly at the protrusion locations and intermixes with the protrusion plastic. The protrusions project from a face wall on the first piece and the face wall is also melted as is the plastic of the second piece engaged with the melting face wall of the first piece. Thus, the face wall is also melted and intermixed with the plastic of the second piece. The intermixed plastics are allowed to cool and become rigid and thereby integrally bond the first and second pieces together. Usually, the bond is made without the usual bulge or expanded weld area formed because of the pliable nature of the plastics being welded.

In the illustrated embodiment of the invention, the first piece is a container handle which has energy directing, spaced protrusions thereon, usually projecting from a face wall of a boss, having a boss wall. The boss and container outer wall are pushed together with force and ultrasonic energy is applied, and ultrasonic energy is directed to and concentrates the vibrations at the protrusions causing them to heat and to melt initially and causing the container plastic in contact with the protrusions to melt and to intermix with the protrusions. As the protrusions melt at spaced points, then the face wall of the boss moves into engagement with the container wall and the melted plastic face wall and the opposite abutted melted plastic of container flow together and intermix.

In accordance with another embodiment of the present invention, the preferred method provides a first plastic body or member with an opening therein; and inserting one end of a fastener boss into the opening and melting energy directors on the boss to mix with melted plastic from the body, defining the opening in body wall. This will secure the boss to the body and the boss will

project outwardly from the plastic body. An elongated shank on a plastic fastener is inserted into a bore in the plastic boss; and energy directors on the fastener shank are melted and mixed with the plastic of the bore wall of the boss to secure the fastener to the boss. The fastener has its shank inserted through a hole in the second member; and an enlarged portion, such as a fastener head, abuts the second member on a side opposite the side opposite the side abutting the boss thereby securing the second member to the first plastic body. Often the first plastic member will be made of a first material and the second member will be made of material that is difficult to secure to the plastic body.

In the illustrated embodiment of the invention, a plastic container body will have a thin wall of 0.025 inches or less, and the boss projects outwardly from the plastic body and has a bore longer than the thickness of the body to give a longer fused attachment to the fastener. In this illustrated embodiment of the invention, the molded wall is a container body of a first material such as PET plastic, and the second member is either a handle of PET or a polycarbonate plastic that is attached by the plastic bosses and plastic fasteners to the container body wall. In this illustrated embodiment, the handle is a rigid loop having an inner handle attaching portion fastened by several bosses and f steners at spaced locations on the container wall. An outer gripping portion of the handle is parallel to and spaced from the attaching portion to allow the user's fingers to be inserted into the space between gripping and attaching portions. In another illustrated embodiment, the handle is a thin, flexible web loop that has an upper neck portion attached to the container neck, and a lower portion connected by a boss and fastener, secured to a bottom end wall of the container in a recess in the bottom wall.

In each of these described embodiments of the invention, spaced protrusions on the boss integral on the first member, the discrete separate boss, or the fastener serve as energy directors or concentrators for ultrasonic energy applied thereto to cause the protrusions to melt quickly, and to fuse quickly into the surrounding melted plastic of the second plastic member. The preferred method involves the step of forcing the protrusions to have an interference fit with the surrounding plastic wall of the body and boss, respectively. The interference fit and energy director shape direct the ultrasonic energy to concentrate at the protrusions to heat and to melt them quickly for intermingling under pressure from the interference fit. The present invention is useful to secure members that are otherwise considered difficult to fuse to a plastic, such as a PET container and a polycarbonate handle.

In accordance with the present invention, molders of plastic articles will need fewer molds or may operate at a faster molding cycle because projections or bosses may be added later and integrally joined to the article with an intermixing of the plastics of the respective articles and the joined projection or boss. The preferred method comprises the molding of a body or shell and providing holes or wall-defining recesses in the body or shell. The holes or recesses have a predetermined size and shape that is matched by the size and shape of the connecting end of a boss, which is inserted into the hole or recess. The engaged boss and the shell wall defining the recess are brought to a flowable state, e.g., by an ultrasonic welding horn and/or a liquid bonding agent, and then respective plastic materials are intermixed and then solidified to form an integral plastic bond between the boss and the shell.

Of particular advantage is the manufacture of the shells of a different plastic material, e.g., low-

cost or lower strength plastic, than the higher strength and more costly material used for the bosses. The base material of the shell can be manufactured from a lesser expensive molding compound and the insertable boss can be manufactured with a higher grade compound and ultrasonically molded to the shell. This would give the boss the added strength and eliminate the high cost material from the shell. For example, if a product weighs 1.50 lbs. in its molded state and the cost of the molding compound is $1.80 per pound, this results in a total cost of $2.70 per unit. The amount of material used in weight in the bosses is .20 lbs., or $.36 of the total cost; to keep the strength, we manufacture the transferable boss from the same material and reduce the grade of material to a compatible grade but at a cost of $.90 per pound, or a total cost of the shell with insertable boss of $1.53. This would give a savings of $1.17 per unit in material cost. Also, by using high grade material, a filler of glass, fiber, or other compounds, the plastic for the boss may be given added strength. These added materials normally reduce the ductility of the molded shell and reduce the impact strength of the overall shell. In many instances, this would be an improvement by gaining impact on the outer surface of the shell plus torsional strength on the holding fixtures.

Because the thick boss portions no longer are present on the mold part, the cycle time for the molding press may be decreased. The present invention also allows cheaper manufacture of some articles because flat plastic sheet stock may be provided within the walls defining the recesses; and the bosses may be inserted therein, the plastics of the boss and sheet stock flowed together and intermixed, and then solidified to provide an integral interconnection of mixed plastic between the bosses and the plastic sheet. Also, the insertable boss will give

an option of using other fusible methods of creating a plastic steel, as in plastic extrusion, which creates a shape by forcing the plastic compound through a die. This method is very economical but at the present time, is only used to create simple shapes because it is continuous and cannot form protrusions. The insertable boss can be integrally joined to plastic extrusions which would now open an economical high volume, low-cost method of producing a part which could be assembled with other components or to another plastic member.

Preferably, the plastic bosses are formed on their connecting ends with a plurality of small protrusions which liquify and flow and become so integrated with the plastic body that a cut through the plastic boss and body fails to reveal the protrusions or a line of demarcation between the boss and the body, particularly where the same plastic is used for the boss and the body.

A preferred manner of achieving the flowable state is the use of ultrasound to heat the respective plastics to a flowable state at the interface therebetween with the small protrusions rapidly melting and flowing into molten plastic from the adjacent bore wall. The force-fit or compression at the points of the protrusions against the bore wall in the body assists in causing the protrusions to flow into the space between adjacent protrusions and losing their shape and identity. Another preferred manner of joining the boss to a plastic body is by use of a bonding agent such as an acetone, a liquid cyanoacrylate ester, or the like that liquifies the plastic of two abut pieces under pressure or compression.

In accordance with the present invention, a method and/or a plastic nut and bolt combination are provided for fastening parts such as panels and the like with a strong and secure clamping force. The plastic nut and bolt fastener described herein provide a strong and

secure connection similar to that afforded by permanent fasteners while allowing the parts to be quickly disassembled from each other without damage to the parts. As the inventive nut and bolt are formed of a plastic material, the clamping force exerted thereby will normally not damage engaged part bodies, particularly those part bodies formed of materials that are less ductile or harder than the plastic material from which the nut and bolt are fabricated. In addition, since the nut and bolt are plastic, they will not interfere with electrical paths and connections used in electronic equipment, such as the conductor paths formed on printed circuit boards.

More particularly, a bolt and nut formed from a plastic material are provided with the bolt having proxi¬ mate and distal ends and the nut having an interior surface defining a bore. Raised projection members, which serve as ultrasonic energy directors, are formed integrally extending from the nut interior surface into the bore and together define a diameter slightly smaller than the shank diameter. In this manner, an interference fit is provided between the shank and projection members. With the bolt shank inserted through aligned holes in parts to be fastened, the nut can be mounted on the distal end of the bolt shank, as by a force fit, "and slid thereon by exerting an axial force on the nut until the parts are clamped between the bolt head and nut. The raised projection members serve as pointed surfaces that direct and concentrate ultrasonic energy at the pointed ends of the projection to cause the ends to heat quickly and to melt. At the interface formed by the engaged projection members and the bolt shank at the areas engaged with a force fit, than by the use of heat as from an ultrasonic source, the engaged plastic materials of the shank and projections are liquified and then are solidified to form a bond at the interface to secure the nut in place on the shank and thereby provide a good and

secure clamping force to the fastened parts . To separate the parts, a torque force sufficient to break the bond formed between the projections and shank is applied to the nut. The nut can then be removed from the shank and the shank withdrawn from the aligned part holes, thus allowing the parts to be separated in their original state without any damage thereto.

In one form, the bolt shank has its distal end chamfered and the projection members extend axially and have at least one inclined surface. The inclined surfaces of the projections engage and cam against the chamfered bolt distal end as the nut is mounted on the bolt shank. The camming engagement of the projection members with the distal ends of the bolt shank more readily allows the nuts to be mounted on the shank with the interference fit between the projections and the shank surface. One manner in effecting the bond between the projections and bolt shank is to apply a bonding agent such as an acetone, a liquid cyanoacrylate ester, or the like to the projection members. The bonding agent such as cyanoacrylate ester works with application of pressure, such as applied from the press fit of the nut onto the bolt shank. Thus, when the nut is mounted on the shank, the interface between the projection members and bolt shank is under compressive pressure forces which will cause the bonding agent to liquify the plastic at the interface with the plastic flowing together and intermixing so as to provide an integral bond at the interface between the shank and nut . In another form of the invention, an assembly for maintaining a clamping fastening force on panels is provided. The assembly includes an upper and a lower panel each having top and bottom surfaces and a bore extending through each of the panels from the top to the bottom surface. A plastic bolt is provided having a head and a shank having a first predetermined diameter with the shank extending from the bolt head. A plastic nut is

provided having a first end and a second end with a -central-bore wall extending through the nut from the first end to the second end to define a shank receiving bore having a second predetermined diameter. A plurality of axial plastic projection members are on the bore wall with the projection members defining a third predetermined diameter less than the shank first diameter to provide an interference fit with the shank when the nut is mounted on the shank. The nut and shank are bonded upon reducing the regions between the projections and shank to a flowable state which then solidify to thereby bond the nut on the shank. The bolt shank can be inserted in aligned bores of the panels and the nut mounted on the end of the bolt shank distal from the bolt head until it engages the lower panel bottom surface to exert a clamping force on the panels by the bolt head on the upper panel top surface and the nut on the lower panel bottom surface. The interface between the shank and projections is then reduced to a flowable state to intermix and then solidify to securely maintain the clamping force exerted by the bolt head and nut on the panels.

Preferably, the projections are in the shape of a trapezoid having inclined surfaces spaced inwardly in the nut bore from the nut ends to allow the nut to be mounted on the bolt shank by engagement of either inclined surface with the shank distal end and with either one of the first and second nut ends engaging the lower panel bottom surface. The projections are circumferentially spaced around the nut bore wall to define spaces therebetween to allow plastic to flow and also to allow the nut to be removed from the shank by breaking the bonds formed at the interface between the projections and the shank surface upon application of a loosening torque force to either the head or the nut. To facilitate the removal of the nut from the bolt shank, the spaces between the

projections preferably occupy a greater volume in the nut bore than the volume occupied by the projections.

Another manner in which the interface between the projections and shank can be reduced to their flowing, liquid state is by use of ultrasound to heat the respective plastics. Tools are commercially available utilizing an ultrasound actuator to apply ultrasound energy to plastic interfaces. By the employment of relatively small projections in the nut bore, the dwell time can be reduced to a minimum, typically well under a second. Such time savings achieved with the inventive fastener herein can lead to substantial increases production efficiency over conventional threaded-type fasteners requiring a torque application force, particularly in continuing assembly operations.

Brief Description of the Drawings

In the drawings, wherein like elements are referenced alike:

FIG. 1 is a cross-sectional view of a boss having an internal screw thread;

FIG. 2 is a side elevational view of the boss of FIG. 1;

FIG. 3 is a plan view of the boss of FIG. 1;

FIG. 4 is a view of the boss of FIG. 3 in the process of being joined to another plastic body;

FIG. 5 is a view similar to FIG. 4 with the boss integrally joined to the plastic body;

FIG. 6 is a cross-sectional view of a boss with a screw therein; FIG. 7 is a partially sectional view of a boss integrally joined to the plastic body;

FIG. 8 is a side elevational view of the screw and boss of FIG. 6;

FIG. 9 is a sectional view of a boss having a collar thereon;

FIG. 10 is a sectional view of the boss of FIG. 9 integrally ^~ joined to a plastic body;

FIG. 11 illustrates a partial insertion of the boss of FIG. 9 into a plastic body; FIG. 12 illustrates a cross-sectional view of the boss of FIG. 9 with a collar added thereto;

FIG. 13 is a cross-sectional view of a boss having an internal screw thread and a collar;

FIG. 14 is a cross-sectional view of the boss of FIG. 13 with a screw therein;

FIG. 15 is a view of the boss of FIG. 13 integrally joined to a plastic body;

FIG. 16 is a cross-sectional view of bottom insertable boss with a screw; FIG. 17 is a view of a bottom insertable boss with a smooth bore therein;

FIG. 18 is a front elevational view of a first plastic element, such as a container, having a second plastic element, such as a handle, secured by bosses and energy directors thereon in accordance with the preferred embodiment of the invention;

FIG. IS is an end view of the handle shown in FIG. 18;

FIG. 20 is a front elevational view of the handle shown in FIG. 18;

FIG. 21 is a side elevational view of the handle shown in FIG. 18;

FIG. 22 is a view similar to FIG. 18, but with the handle oriented vertically instead of horizontally; FIG. 23 illustrates another embodiment of the invention where a second member is being attached to a first member, to which is secured a boss to receive a plastic fastener, the boss and fastener having energy directors thereon; FIG. 24 shows the plastic fastener bonded to the boss, and the boss bonded to the first member;

FIG. 25 illustrates the boss and fasteners of FIGS. 23 and 24 used to attach one end of a handle to a container;

FIG. 26 illustrates another container with a handle attached by fasteners and bosses in accordance with the invention;

FIG. 27 is an enlarged view showing a portion of the handle, shown in FIG. 26, attached by four bosses and four fasteners to the container; FIG. 28 is an enlarged view of a boss;

FIG. 29 is an enlarged view of an end of a boss;

FIG. 30 shows a boss being connected to a container wall;

FIG. 31 shows the melding of the plastics from the energy directors and the wall of the container;

FIG. 32 illustrates a boss having a large number of energy directors thereon;

FIG. 33 illustrates a second member having an integral boss with energy directors attached to a first member;

FIG. 34 is a perspective view of the second member and boss of FIG. 33;

FIG. 35 is a bottom, perspective view of the second member and boss shown in FIG. 33. FIG. 36 is a perspective view of a weldable fas¬ tener showing a plastic nut and bolt combination according to the present invention;

FIG. 37 is a top plan view of the nut of FIG. 36 showing the raised projection members on the nut bore wall;

FIG. 38 is an elevational view of the nut showing the flats thereof;

FIG. 39 is a sectional view of the nut through the bore and showing the integral projection members; FIG. 40 is a sectional view of the bolt and nut with the bolt extending through aligned bores in a pair of panels to be joined together;

FIG. 41 is a side sectional view similar to FIG. 40 showing the nut mounted on the distal end of the bolt shank showing the integral bond formed between the projection members and the shank with the panels securely clamped between the nut and the bolt head;

FIG. 42 is a side sectional view similar to FIGS. 40 and 41 showing the nut removed from the shank to allow the parts to be separated by breaking of the bond formed at the interface between the projections and the shank;

FIG. 43 is a side sectional view showing a modi¬ fied belt shank inserted through aligned holes in the panels with a spacer member mounted on the shank to space the panels from each other; and FIG. 44 is a cross-sectional view taken along line 9-9 of FIG. 43 showing the nut mounted on the distal end of the modified bolt shank.

Detailed Description of the Preferred Embodiment

Referring now to the embodiment of the invention disclosed in FIGS. 1-6, the plastic piece is a boss 200. The boss 200 is a projecting part which projects outwardly from a plastic body or shell 201. The body 201 may be a injected molded shell or a piece of plate stock which has a predetermined thickness between a top sidewall 203 and a bottom sidewall 205. This cross- sectional thickness the shell is usually smaller than the cross-sectional thickness of the boss 200. The body 201 may be, for example, a dashboard shell, which would usually have integral bosses or projections at various locations projecting outwardly from the wall 203 which would allow it to be joined to another shell or to have therein openings for receiving fasteners or the like to which may be joined by other instruments or materials used in the automobile. As above explained, the boss 200, particularly if it is solid without a hole, represents a large cross-sectional thickness which may be

larger in cross-sectional thickness than the shell wall between the top sides 203 and the bottom sides 205 of the shell such that it takes much longer for the boss to cool and solidify after the plastic has been injected into the mold than the time required to solidify the thinner cross-section of the shell wall. In many instances, the particular material used for the entire shell body and for the boss is dictated because of the strength requirements needed for the boss. In some instances, a much more expensive, stronger plastic is used for the shell so that the requisite strength is available for the material for the boss to receive a screw or the like to fasten the shell in place. On the other hand, if strength or hardness is added for the shell, it may reduce the ductility desired for the shell.

In accordance with the present invention, the boss 200 is made of a separate piece of the same material or a different material as the shell and after molding the boss is integrally affixed to the shell by first providing holes or recesses 204 in the shell 201 at the locations desired and then attaching a boss at these holes 204. Preferably, the holes or recesses 204 include a encircling recess-defining wall 206 which in this instance is circular or cylindrical in shape to receive a cylindrical lower connecting portion 200a of the boss 200. As is the case in the above-described embodiments of the invention, it is preferred that the diameter of the boss be slightly larger than the hole diameter so that there is a force fit when driving the connecting end 200A of the boss into the hole 204.

It is preferred to provide a series of small projections 210 which are also force fitted into engagement with the shell and the recess-defining wall 206. By ultrasonic welding or by use of a bonding agent, the projections 210 are caused to flow in a plastic state, for example, melted, and likewise the plastic at the wall 206 is also melted and caused to intermingle and

intermix to form a flowable, plastic puddle. The boss 200 is pushed into the hole 204 until the full depth is reached whereby there is allowed a solidification of intermixed plastic 215, as viewed in FIG. 19, which provides, when solidified, an integral plastic bond between the boss 200 and the shell 201. It is preferred that the melted and intermixed plastic 218 extend entirely around the circumference of the boss. In the preferred operation, both a bonding agent and the ultrasonic welding horn may be used to cause the respective plastics of the boss and body to meld and intermix so that when they solidify it is difficult to see any parting line between the respective boss 200 and the sheet body 201. In order to assist in guiding the connecting end

200A of the boss 200 into the hole 204, it is preferred that the connecting end 200A have a beveled or chamfered portion 220 at its leading edge. Thus, the chamfered portion 220 of the boss is centered in the hole as it is pushed into a force fit until the boss's major diameter is reached at the location of the meltable projections 210. Usually, but not necessarily, the boss 200 will have a performed bore 222 therein for receiving a fastener and the hole may be in the form of a screw thread 224 (FIG. 1) . In the embodiment of FIG. 6, a thread 224 is present in the boss 200 and the thread 224 is threadably mated with a mated thread 226 of a metal screw fastener 228. The thread 224 may already be formed in the boss 200 prior to attaching of the boss to the shell 201 or there may merely be provided a smooth walled bore 200, as shown in FIG. 7, such that metal screw 228 is a self-tapping screw 228 which has been threaded into the unthreaded bore 232 (FIG. 9) which extends axially and centered along a vertical axis 234, FIGS. 7 and 9. The bore 232 shown in FIG. 9 has an enlarged chamfered entrance portion 236 at its entering end. In the embodiment of the invention shown in FIG. 6, the boss 200

has the threaded screw 228 already therein, prior to insertion of the boss 200 into the hole 204 and the welding of the boss to the shell 201. Thus, the fastener may be assembled to the boss prior to the positioning and connection of the boss to the shell.

In some instances, it is desired to limit the amount of the insertion of the boss 200 into the hole 204 and this may be accomplished readily by providing a shoulder 240 (FIG. 10) on the boss 200 which will abut the plastic body 201, as shown in FIG. 10. As best seen in FIG. 10, the preferred shoulder 240 is annular in shape and has an outer diameter larger than the outer diameter for the cylindrical wall 241 thereabove. In FIG. 10, a lower edge 243 of the collar shoulder 243 abuts the top shell wall 203 to limit the extent of boss insertion so that lower end 245 of the boss does not project below the lower sidewall 205 of the shell 201. The hole 204, shown in FIGS. 1-10, is a through hole in the sense that it does not have a bottom. The collar 240 serves as a rim which not only stops insertion of the boss 201 but also adds extra area for welding when the ultrasonic horn is directed to the collar so as to melt plastic in the area 247 (FIG. 10) . The melted and later solidified, plastic material includes not only plastic material from the projections 210 but also from the collar portion 240 as well as from the shell 201. Preferably, the collar is disposed directly in abutment with the top wall 249 of the projection, as is shown in FIG. 10. The illustrated boss 200 in FIG. 10 may either have a thread already formed therein, such as shown in FIG. 1, with the thread 224 in the boss, or alternatively, the bore may be smooth walled to receive a self-tapping thread therein, as shown in FIG. 9. Of course, the metal screw fastener may be either threaded into the boss at a later time or it may be threaded into the boss prior to affixing the boss to the shell 203.

In some instances, it will be desired to insert and to attach the boss at the bottom side 205 of the shell 201, and this is illustrated in FIGS. 15 and 16, wherein the bottom wall 205 is provided with an enlarged diameter recess 250 that has an upper wall 251 against which is abutted a collar 240 on the boss. In the embodiment wherein the boss is inserted through the opening 250 in the bottom sidewall 205 of the body 201, the insertion continues until upper facing annular wall 253 of the collar 240 abuts the top wall 251 of the recess 250 whereby upward travel is stopped. As described previously, it is preferred to provide a series of projections 210 on the boss 200. The bosses are intended to receive a force fit with the hole defining wall 206 and which will meld with the plastic from the collar 240 and the plastic from the shell 201 to provide the unitary connection therebetween when the melded plastic solidifies. Preferably, the ultrasonic welding is done by placing an ultrasonic welding horn against the collar 240 so that a portion of the collar is also melted and blended with the other plastics as above-described.

The illustrated screw 228 in FIGS. 15 and 16 has a screw 224 mated with the metal thread 226 on the metal screw 228. In this embodiment of the invention, the screw has a lower end 257 which projects below the boss and its collar 240 and is disposed within the recess 250, as shown in FIG. 15. Rather than having a screw thread formed in the upwardly inserted boss, as shown in FIGS. 15 and 16, the boss may have a hollow bore which is unthreaded, as shown at 262 in FIG. 17 of a boss that may be used in lieu of the boss shown in FIG. 16.

As previously explained, the plastic for the boss 200 may be of a stronger or different material and a cheaper or better appearing material or more ductile material may be used for the shell 201. Thus, the strength factor for the boss need not be the determining factor of the plastic material used for the shell 201.

It is often desired to have fillers such as glass or other fillers added to the boss to make it stronger. The plastic body may have many shapes, such as a dashboard or any other plastic part to which it is desired to add a boss. In some instances, the plastic body 201 will merely be a flat sheet, for example, a support plate for electronic components such as for an integrated circuit, a printed circuit or other electronic circuits used in the semiconductor industry. Four bosses may be joined to the corners of the plate or the sheet or at other special locations depending upon the model or needs. Thus, rather than having a series of molded boards each with a number of different molded bosses thereon, the electronic carrying board may be formed first without integral bosses and then using separate discrete bosses of different materials from the actual sheet of board material with the bosses may be joined to the board in various locations without having to build a mold for each electronic board. In many instances, the boss is not really a projection and may or may not have the specific hole used for a fastener or other attaching device. For instance, a hole in the boss may receive another force fit plastic plug or pin from another shell half to join the two shell halves together in lieu of using metal fasteners or the like.

From the foregoing, it will be seen that there is described a new and improved method of joining plastic articles together; and that a new and improved manner of securing plastic components to a plastic body or plate is provided. The invention provides a quick and inexpensive joinder of plastic articles or bodies usable in automated or manual, large scale assembly operations and provides a good adhering of the component bodies to a plastic body or plate. As shown in the drawings, for purposes of illustration, the invention is embodied in a first plastic member 10, such as a container 11 having a thin

wall 12 to which is attached a second member 14 (FIG. 18) such as a handle 15. Typically, the container wall has a thin cross-section, e.g., under 0.025 inch and is often made of a plastic that is difficult to fuse, such as PET, particularly in securing other plastic objects thereto. Often, the second member, such as the handle 15, are of a shape or a different material that cannot be integrally molded with the plastic body. In formation of PET containers, a small preform is injected molded and then the preform is blown to full, and it is desired to attach a full size handle to the full size container. In this illustrated embodiment of the invention, the container is made of a PET plastic and the handle is made of either PET or of polycarbonate material although other plastic materials may be used for the container and/or handle. In accordance with the present invention, the first plastic body 10 and the second member 14 are provided with a plastic boss 20. The boss 20 has energy directors 24 in the shape of spaced protrusions 26 which are melted and mixed with plastic of the container wall 12 to form a good strong connection therewith. In the embodiments of FIGS. 18-22, a plurality of bosses 20 are integrally formed with the plastic handle with the energy directing protrusions 26 that project outwardly from a face wall 23. In the embodiments of FIGS. 23-31, the boss 20 is a separate, discrete piece, as best seen in FIGS. 11, 13 and 14 with boss protrusions 26 projecting outwardly from a face cylindrical wall 23 and abutted against a wall 28 (FIG. 24) defining an opening 30 in the container wall. In the FIG. 23-31 embodiments, the handle 15 has a hole 32 therein with an enlarged portion 34 of the fastener, such as a fastener head 35 abutting an outer side of the handle. A shank 36 on the fastener has energy directors 38 in the form of protrusions 40 thereon that are fused and mixed with plastic of a bore wall 42 in the boss in which wall 42 defines an elongated, hollow bore 44 therein. Thus, the shank of

the fastener may be fused to the boss, which is fused to and projects outwardly from the'container wall 12. In this embodiment of FIGS. 6-14(23-31?), the bore and fastener have a fused length greater than the thickness of the container wall to give a good bonding surface area.

As disclosed in the aforesaid patent applications which are hereby incorporated by reference as if fully reproduced herein, the boss 20 (FIG. 23) may have a cylindrical body 46 with the boss protrusions 26 having slanted sidewalls 48 tapered in the direction of insertion so that the slanted sidewalls will slide along the container opening wall 28. The preferred fit is an interference fit with the outer diameter of the boss being equal to or greater than the diameter of the boss cylindrical body 46. In the embodiments of FIGS. 18-22, the face wall 23 of the boss 20 is a flat, circular wall with a plurality of radially extending protrusions 24, e.g., there being ten (10) protrusions shown in FIGS. 18 and 20. The protrusions are spaced to cover the entire bottom wall 23 of the boss so that the entire bottom wall will be attached to the container wall. The protrusions 24 project radially inwardly from an outer, circumferential wall 31 for the boss toward the center of the boss, and terminate at inner ends 33 spaced from a center axis 35 for the boss. Typically, the protrusions are quite small and pointed with a thicker base and a narrower outer side. The protrusions may be, for example, 0.375 inch in length; 0.016 inch in width; and 0.016-0.020 inch in height. A small diameter hole 55 is formed in the upper sides of the bosses to receive an ultrasonic horn therein.

The boss 20 will be forced under pressure against the container wall, and the protrusions may be deformed in the process. It has been found that the special protrusions 26 acts as energy directors for the ultrasonic energy to cause the ultrasonic energy

emanating from the ultrasonic horn to flow along the protrusions to their outer ends with the vibrations concentrated thereat, e.g., the ultrasonic vibrations are concentrated at the pointed ends 50 (FIGS. 18 and 29) . It appears that the energy directors first melt. That is, the ultrasonic energy is concentrate at the pointed ends of the protrusions and causes a quicker melting of the protrusions themselves and the abutted contiguous plastic of the container wall 12 first, before there is a melting of the portions 46a between the protrusions. The melted plastic from the protrusions flows sideways into spaces 51 between adjacent protrusions (FIGS. 18 and 29) .

A more generic form of boss 20 with energy directing protrusions 24 is shown in FIGS. 33-35, and this generic form of boss may be used on a portion 80 of any plastic second member 14. As more clearly seen in FIG. 35 the protrusions 24 may be formed with a triangular cross-section with long, sloped sidewalls 81 meeting at the sharp pointed end or edge 50. The spaces 51 between protrusions allow for the lateral flow of plastic as the protrusions are melted and form fused areas 62 of mixed plastic from the protrusions and the first plastic member 10. The boss 20 of FIGS. 33-35 is more hollow with a hole 55 having an enlarged diameter hole portion 55a and a connecting, smaller diameter portion 55b to receive an ultrasonic horn therein to melt the plastics of the respective first and second members 10 and 14. The outer cylindrical wall 31 of the boss can also be encircled by an ultrasonic horn; and the hole 55 need not be present in the boss 20. Thus, it will be seen that various plastic members 14 for any number of applications, in addition to the container application described herein, may be provided with an integral plastic piece or boss 20 with the energy directing protrusions 24 thereon, and be attached with a good, strong, complete area bond of invisible melded plastics to a first member 10.

Turning now to the embodiment of FIGS. 23-31, to facilitate the insertion of the boss into the opening 30 in the container body wall 12, it is preferred to provide a chamfered end 58 on the boss. That is, the lower, leading end of the boss has a smaller diameter than the hole diameter to facilitate the starting of the boss insertion before the interference fit begins near the upper end of chamfered end 58. Usually, the boss will be made of a plastic material, the same as or close to the material of the body wall 12 to facilitate fusing and blending of the plastics into one another. Here, the container wall 12 is made of PET plastic and the boss is made of a plastic similar to the PET container wall 12. In other instances, bosses made of polycarbonate material have been fused to the PET wall. After melting of the engaged plastics of the boss and first member wall, the melted plastic is allowed to solidify and hence, the plastics are intermingled to form a melded, rigid plastic connection of great strength. When a cut is made through the cross-section along the line 60 (FIG. 26) through the location where the protrusions 26 were originally, one usually cannot locate where the protrusions were located. The protrusions are melted and mixed so well that they no longer could be found. As best seen in FIG. 26, there are rigid, fused areas 62 of combined plastics from the boss 20 and the first body wall 12 in a circular band. The fused plastic areas 62 provide a very strong connection between the boss and the container.

In a like manner, the fastener protrusions 40 have a slanted wall 40a to facilitate insertion of the fastener into the bore 44 of the boss. The outer diameter of a cylindrical wall 66 on the fastener is equal to or larger than the diameter of the bore wall 42 so as to provide an interference fit between the fastener and the bore wall 42 of the boss. When ultrasonic energy is applied to the fastener, the protrusions 40 serve to concentrate the ultrasonic energy at their outer pointed

ends 70 which appear to melt first and more completely mix with the melted plastic of the bore wall 42 of the boss. The protrusions 40 are spaced circumferentially about the circumference of the fastener as shown in FIG. 15(32?). The plastic between protrusions also melts, intermingles and mixes and then is allowed to solidify into a solid fused area 72 (FIGS. 24 and 25) .

Another container 111 is shown in FIGS. 26 and 27 as having a handle 115 in the form of a loop with an outer gripping portion 116 and inner attaching portion

117. The handle 115 can be made of PET plastic or it can be made of polycarbonate or other material. Preferably, the container is made of PET although it can be made of various plastics such as polyethylene, acrylics, polystyrene, etc. The illustrated container 111 has a central depression 119 therein with the handle attaching portion 117 being fastened by four fasteners 22 and four bosses 20 in the same manner as described above in connection with the container 11 of FIG. 25. As shown in FIG. 26, there are four spaced fasteners 22 and four bosses 20 to attach the handle portion 117 at four spaced locations to the adjacent container wall 112. The gripping handle 15 (FIG. 25) is attached at the bottom of the container within a recess 80 formed by a bottom recess wall 81 of the container body to allow the container to sit upright on the bottom wall. The upper end of the handle 15 has an integral end 82 which has an opening 84 therein smaller than the diameter of a shoulder ring 85. The handle may be of soft, flexible polycarbonate and the smaller diameter opening may be pulled over the shoulder 85 while stretching, and then allowed to return to its smaller diameter on the container neck 87. Thus, the upper end of the handle may be secured to the container neck. Because the handle 15 is of a soft, flexible and thin plastic material, it can be pushed against the sidewall of the container and not interfere with the packaging of adjacent containers.

Likewise, the handle 116 can be made of a soft material, although it is preferred to be made of a rigid strap, plastic material and fitted into the central recess or depression 119, so as not to substantially interfere with i.e., increase the overall dimension. Particularly, for large containers, e.g., three or more liters, the rigid handle allows pouring from the container in a horizontal position when the cap 130 is removed.

From the foregoing, it will be seen that there is a new and improved method of fastening plastic members together using energy director protrusions on a boss. The ultrasonic energy from the ultrasonic horn concentrates the energy at the protrusions causing them to melt first. The space between protrusions allows the melted plastic of the protrusions to have a space in which to flow thereby eliminating the usual bulge or expansion one gets when abutting two smooth, plastic surfaces together. The protrusions usually are positioned to cover the area where the bond is to be made so that the bond may a complete one, e.g., around a 360° circumference for a circular area.

In FIG. 36, a weldable fastener 305 including a plastic bolt 310 and nut 312 according to the present invention are illustrated. The nut and bolt of the present invention are formed from a plastic material such as a polycarbonate, polypropylene or nylon material, and can be used for fastening bodies together, such as the panels 314 and 316 illustrated in FIGS. 40-43. The nut 312 is mounted on the bolt 310 by way of raised projection members 18 formed on the nut 312 so that the nut 312 can be secured on the bolt 310 as by an integral bond between the bolt and projections and thereby provide a good, secure clamping force on the bodies 314 and 316. More particularly and referring to FIGS. 37-39, the nut 312 has opposite end surfaces 320 and 322 with a bore 324 extending through the nut 12 between the end surfaces 320 and 322. Preferably, the nut 312 has a

polygonal shape and is illustrated as a hex nut having flats 325 with the bore 324 being centrally located and defined by a cylindrical bore wall 326 extending between the end surfaces 320 and 322. The raised projection members 318 are spaced circumferentially around the bore wall 326 and are adapted to engage the elongate shank 328 of the bolt 310 as the nut 312 is press fit and slid thereon.

The bolt elongate shank 328 has a proximate end 330 and a distal end 332 with the enlarged bolt head 334 formed at the proximate end 330, as is conventional. Preferably, the bolt head 334, similar to the nut 312, has a polygonal shape having flats 335, and is illustrated having a hexagonal shape, and the bolt shank 328 has a cylindrical surface 337 adapted to receive the nut 312 thereon. The annular bore wall 326 has a predetermined diameter which can be sized substantially the same or slightly larger than the diameter of the shank cylindrical surface 337. By way of example, in one preferred embodiment, the nut bore wall 326 has a diameter 0.130 inch. The projection members 318 extend radially a predetermined distance into the annular bore 24 and together define a diameter slightly smaller than the diameter of the bolt shank 328 so as to provide an interference fit between the projection members 18 and bolt shank surface 337. Where the bore wall predetermined diameter is 0.130 inch, the projections 318 can extend radially 0.0072 inch from the bore wall 326, and define a diameter 0.1158 inch. In the preferred and illustrated form, the pro¬ jection members 318 extend axially along the bore wall 326 between and spaced from the nut end surfaces 320 and 322. The projections 318 are shown to be in the shape of a trapezoid having opposite inclined surfaces 336 and 338 which extend from the bore wall 326 towards the interior of the bore 324 with the inclined surface 336 positioned in the bore 324, spaced inwardly from the end surface 320

and the inclined surface 338 positioned in the bore 324 spaced inwardly from the end surface 322, as best seen in FIG. 38. The inclined surfaces 336 and 338 extend towards each other and are joined by a top, axially extending surface 340. In the preferred embodiment, the inclined surfaces are inclined at a 15° angle from the bore wall 326. The projections 318 also include slightly inclined side surfaces 342 and 344 extending from the bore wall 326 at an angle to the top surface 40 between the inclined end surfaces 336 and 338. This provides pointed ends that serve to direct and concentrate ultrasonic energy to these ends to cause them to quickly heat and melt before other areas.

Although the exact number of projections 318 can vary, in the preferred and illustrated embodiment, four projection members 318 are spaced equally at 90° intervals on the annular bore wall 326. Preferably, the number of projections used is to give a complete bond of 360° about the nut and bolt. The predetermined diameter defined by the projection members 318 can be measured across the bore 324 from the top surface of opposite projection members 318. As the top surfaces 340 define a diameter therebetween smaller than the diameter of the shank cylindrical surface 337, the inclined surfaces 336 and 338 are provided to assist in mounting the nut 312 on the shank 328 so that as the distal end 332 of the shank 328 is inserted into the bore 324, the distal end 332 will engage and cam along one of the inclined surfaces 336 and 338 to progressively increase the interference and the compressive forces exerted between the shank 328 and projection members 318. To further facilitate mounting of the nut 312 onto the bolt 310, the shank distal end 332 can be chamfered, as illustrated in FIG. 36, forming an annular ramp surface 346 which can cam against one of the inclined surfaces 336 and 338 to facilitate press-fitting of the nut 312 onto the bolt shank 328.

With the nut 312 mounted on the bolt 310 to exert a clamping force for fastening parts as described above, the interference fit provided between the projection members 318 and shank surface 337 will cause their interengaging portions to be under compressive pressure forces. The interengaging portions between the projection members 318 and shank surface 337 can then be brought to their flowable state at their interface, such as by a bonding agent. Suitable bonding agents include those using acetone or cyanoacrylate ester that causes the plastics to form a liquid or semi-liquid state initially when the plastic is placed in compression and then to cure or otherwise harden to integrally bond the nut 312 on the bolt 310. Alternatively, ultrasound tools can be utilized to apply ultrasound heat energy to the areas interengaged by the force-fit between the projection members 318 and shank surface 337. Utilizing the inventive plastic weldable bolt 310 and nut 312 herein can save substantial time in applying the fasteners 335 to parts versus conventional threaded-type fasteners and other means for forming permanent connections, e.g., riveting and conventional welding or soldering, as the dwell times for the application of ultrasound to the interengaged areas can be controlled by sizing of the projection members 318 so that it is well under one second.

Thus, to fasten a pair of bodies together, such as panels 314 and 316 illustrated in FIGS. 40-42, or the panels 314 and 316 in spaced relation to each other by way of intermediate member 364 therebetween, such as illustrated in FIG. 43, the bolt shank 310 is inserted through the aligned holes of the bodies with the nut 312 then being press fit on the distal end 332 of the bolt 310. More specifically and referring to FIGS. 40-42 the panels 314 and 316, which can be metal, plastic, or any other material, are fastened together by the clamping

force between one of end surfaces 320 and 322 of the nut 312 and the bottom 348 of the bolt head 334.

The panels 314 and 316 have mounting through bores 350 and 352, respectively, drilled or pre-formed therein. The panels 314 and 316 each include respective top surfaces 354 and 356, and bottom surfaces 358 and 360. To fasten the panels 314 and 316 together, the bottom surface 358 of the panel 314 and the top surface 356 of the panel 316 are abutted flush against each other such that the respective bores 350 and 352 of the panels 314 and 316 are aligned with each other. The bolt shank 328 can then be inserted through the aligned holes 350 and 352 with the nut 312 then being press fit on the shank 328, as described earlier. The nut 312 can be slid along the portion of the shank 328 protruding from the bottom surface 360 of the lower panel 16. Since the nut 312 has projection members 318 with inclined surfaces 336 and 338 at both ends, the nut 312 can be slid onto the protruding shank portion with either of its opposite end surfaces 320 and 322 facing the bottom surface 360 of the lower panel 316 so that the chamfered end of the shank 328 will engage one of the inclined surfaces 336 and 338 depending on which respective end surface 320 and 322 is facing the bottom surface 360. As illustrated in FIGS. 40-46, the nut 312 is slid axially onto the protruding bolt shank portion with the surface 320 facing the bottom surface 360 until these two surfaces are engaged with continued axial force bringing the bottom 348 of the bolt head 334 into secure clamping engagement with the top surface 354 of the upper panel 314. In this manner, a clamping force is exerted on the panels 314 and 316 by the bolt head 334 and the nut 312.

With the nut 312 in clamping arrangement on the bolt shank 328 and the panels 314 and 316 clamped there¬ between, the areas engaged with a force fit between the engaged projection members 318 and the shank 328 are

brought to their flowable state at their interface and form a region 362 of blended plastic thereat, as described earlier and shown in FIG. 41. Once the plastics are intermixed and blended in the region 362, the plastic region 362 can be cooled and cured to solidify and integrally bond the nut 312 in its clamping arrangement on the bolt shank 328. With the integral bonding of the nut 312 to the shank 328, the fastener of the present invention is a significant improvement over conventional threaded-type fasteners which can tend to loosen over time under the influence of tension and shear forces, particularly when utilized in high shock or vibration environments. The bonding at the plastic region 362 provides a good, strong resistance to tension forces tending to pull the nut 312 off of the shank 328 similar to that provided by other permanent fasteners such as rivets. Unlike conventional welding or soldering, the integrity of the interface between the fastened parts is not compromised so that upon removal of the nut 312 from the bolt 310, as described below, the parts can be released from their fastened connection in their original state for reuse and reassembly.

To remove the nut 312 integrally secured on the bolt shank 328, as shown in FIG. 41, a turning torque force can be applied to the nut 12 by engaging the flats 325 with jaws of pliers, wrenches or the like as done with conventional threaded-type fasteners while holding the bolt head against rotation. Alternatively, the torque force could be applied to the bolt head 334 while holding the nut 312 against rotation; however, turning of the nut 312 is preferred since it provides a mechanical advantage as the bond to be broken by the torque force is in the nut bore 324.

A turning torque force sufficient to break the bonds formed in the region 362 should be applied to the nut thus allowing the release of the parts 314 and 316 without damage thereto as only the broken bonds at the

areas 362 on the projection members 318 and bolt shank 328 will be damaged by the turning torque force, as seen in FIG. 42. This is of particular importance where the parts should have the capability of being disassembled and then reused as by reassembly to another part such as with another one of the inexpensive plastic nut and bolt fasteners 305 taught herein.

Referring to FIG. 43, the panels 314 and 316 can be printed circuit boards and the intermediate member 364 can be a tubular spacer to allow the printed circuit boards to be mounted in spaced relation to each other on the bolt shank 328. In this manner, the printed circuit board panels 314 and 316 are stacked on the shank 328 in engagement with the opposite end shoulders 365 and 367 of the spacer 364 and clamped thereagainst by the bottom 348 of the bolt head 334 and the nut end surface 320. Such stacking of printed circuit boards is of particular value in electronic equipment where space savings are important and, accordingly, more spacers 364 and a longer bolt shank 328 can be utilized depending on the number of boards to be stacked. Thus, when the boards need to be replaced, interchanged or maintained such as by adding and removing electronic components thereto, the nut 12 bonded on the shank 328 can be removed by applying a turning torque force sufficient to break the bonds in regions 362 between the projection members 318 and the shank 328.

Manifestly, it will be apparent that the dwell time required to bond the projection members 318 to the shank 328 can be varied by varying the size and number of the projections 318 formed on the bore wall 326. In addition, the amount of torque necessary to break the bonds between the projection members 318 and the shank 328 can also be adjusted based on the number and size of projection members 318 provided. In the preferred and illustrated form, four projection members 318 are spaced equally at 90° intervals on the nut annular bore wall 326

so that with the nut 312 mounted on the bolt shank 328, the spaces 372 formed between the projection members 318 will occupy a greater volume in the bore 324 than the projection members 18. With four projection members 318, a good and secure connection can still be achieved between the projection members 318 and the shank 328 while still allowing for a turning torque force to break the integral bonds formed between the projections 318 and shank surface 337. As the projections 318 are relatively small compared to the spaces 372 between adjacent projection members producing regions 362 of intermixed plastic which are relatively small in comparison to the distance around the circumference the bore 324 and shank 328, as seen in FIG. 44, the turning torque force required to break the bonds formed between the projections 318 and shank surface 337 can be controlled and limited such that the required breaking torque force, for example, may be only slightly greater than that required to unscrew a conventional nut which is tightly screwed and locked on a threaded bolt shank. Application of the bond breaking torque allows the nut 312 to be removed from the shank 328 to effect release of the parts.