An Improved Fastener and Driving Tool

Field of Invention

The present invention generally relates to threaded fasteners and its related fastening tool, more particularly to a threaded fastener having a non-standard form of driving recess and a fastening tool for engagement within such recess.

Background of the Invention

Fasteners such as screws and screwdriver have been widely used for attachment of parts. The screwdriver will convey a torque when engage into the recess at the screw head to fasten and loosen the screw. Various forms of recesses have been developed. Conventional recesses are in slotted or minus shape, cross or Philips shape, Pozidriv shape, Torx shape, Hex shape, Robertson shape, Torq-set shape, spanner head shape etc.

Among these screws, the slotted or minus shape screw has a most simple structure and most commonly use in woodworking applications. However, the drawbacks of this head are the screw driving tool bit cannot be centered on the slot of the screw head and the slot is open ended at both ends which cause the tool bit to be easily disengaged from the recess in the screw head. This causes an inefficient workability.

The cross shaped screw is wideh used everywhere and having the advantage of the tool bit to engage in the recess centered on (he scicw head But when there is high resistance to penetration, the screw uirns less than the tool bit, forcing the tool bit out of the recess void of

When this happens, the external edges of the bit begin to cut the inner corners he screw head, thereby enlarging the center into a rounded pit causing screw failure as the screw could not be turned anymore and has to be replaced. Disengagement of the driving tool would cause the driving tool to slip out of the recess and sometimes scratches the surface of the work.

The present invention overcomes the drawbacks of the known fasteners and driving tools while maintaining its advantages.

It is an object of the present invention to provide a fastener and driving tool wherein the lengthened arms of the grooves of the driving recess in the fastener head is suited to good torque transmitting engagement by the driving tool.

Another object of the present invention is to provide the fastener with vertical ridges and end points for receiving the corresponding sharp corners of the driving tool bit for preventing the bit from slipping out even during high resistance to penetration of the fastener.

Yet another object of the present invention is to provide the fastener with higher strength structure that is not prone to failure during fixing by minimizing the recess void bounded by the threaded shank diameter and thus increasing metal connectivity of head to shank.

Additional objects, advantages and novel features of the invention shall be set forth in part in the description that follows and in pan will become apparent to those skilled in the art upon examination of the following or may be learned by the practice of the invention. The objects

^, may be realized and attained by means of the instrumentalities and in irticularly pointed out in the appended claims.

Summary of the Invention

In the present invention, an improved fastener comprises of a threaded shank; and a head connected to the threaded shank characterized in that the head having a driving tool engaging recess that is formed with a plurality of grooves extend in radial direction from a central point at a larger diameter than the diameter of the threaded shank and symmetrically spaced in the circumferential of the head, whereby each groove is formed with a pair of vertical ridges curved at both periphery sides of the groove to respective end points at the fastening and loosening of the fastener directions and disposed in proximity to the outer diameter of the threaded shank and which is engageable with a driving tool having corresponding bits for firm interlocking action between driving tool bit and recess in head to prevent tool bit slipping out of recess of head during strong resistant to penetration.

Preferably the recess of the fastener is arranged in Y-shape on the top face of the head with the grooves symmetrically spaced at the central point and formed in tapered cross section.

Preferably the side walls from the end points are gradually expanded (o the outer periphery of the groove.

Preferably the base wall at the central point being the deepest portion and is substantially equivalent to the thickness of the fastener head.

snd point is preferably located at approximately half radius of the fastener

A driving tool for operating the fastener comprises of a shank, and a driving head having respective bits that engage in and substantially conform to the shape of the recess of the fastener. The driving head bits include engaging faces which are protrude and symmetrically spaced around the driving head and driving side walls connecting the adjacent engaging faces.

Brief Description of the Drawings

Other objects, features, and advantages of the invention will be apparent from the following description when read with reference to the accompanying drawings. In the drawings, wherein like reference numerals denote corresponding parts throughout the several views:

Figure 1 is top view of the fastener of the present invention showing the configuration of the recess at top face of the fastener head.

Figure 2 shows a cross sectional view of the section X-X shown in figure 1 showing the inclined faces of the groove of the recess.

Figure 3 depicts a side view of the driving tool for operating the fastener of the present invention.

tes a bottom view of the driving tool showing the driving head with the bits nding shape of the recess for the fastener.

Detailed Description of the Preferred Embodiments

Referring now to the drawings, and particularly to Figure 1 thereof, there is shown a fastener (10) having a threaded shank (11) and a head (12) connected thereon. The head (12) is substantially circular and provided with a driving tool engaging recess (13) formed in its top face of the fastener (10) where the recess (13) has a tapered cross section for the insertion of the driving tool (14). The recess (13) comprising a central point (15) at the center of the head (12) and grooves (16) extending radially outwardly of the central point (15) and spaced symmetrically therearound. The recess (13) in a radial direction from the central point (15) is extended at a larger diameter than the threaded shank (11) diameter. Preferably the fastener (10) of the present invention is made of metal. The head (12) of the fastener (10) could be formed in pan head, button or dome head, round head, truss head, flat head or countersunk, oval or raised head, bugle head, cheese head, fillister head and the like.

In a preferred embodiment of the present invention, (he fastener (10) includes three grooves (16) symmetrically arranged in Y-shape on the top face of the screw head (12) as shown in figure 1. A person skilled in the art may configure the shape of the recess into other forms such as slotted head, cioss shape, pentagonal shape, hexagonal shape and the like. Imaginary radial lines (18) are formed connecting the central point (15) to bisector points of the circumferential width (W) of the groove (16) with angle of appioximately 120 degrees between each groove (16) The gioove (16) includes a pair of side walls (16a) and an outer periphery (16b). The groove (16) of the recess (13) having its inner portion adjacent the

5) with its pair of side walls (16a) initially extends at equidistance and then outwards forming vertical ridges (28) to respective end points (17) which are preferably lie at approximately half radius of the screw head (12). The outer portion of the recess (13) having the pair of side walls (16a) extends from the end points (17) of the inner portion groove (16) at obtuse angles and meet with the respective edge corners (30) of the outer periphery (16b) of the recess (13). The pair of side walls (16a) of the outer part of the recess (13) is gradually expanded from the end point (17) of the inner portion of the recess

(13) to the edge corners (30) of the outer portion of the recess (13). The lengthened arms of the groove (16) result in more torque transfers from the driving tool (14) to the recess (13) in the head (12).

Each groove (16) has a base wall (19) which is inclined from the outer periphery (16b) inwardly and downwardly towards the longitudinal central point (15) as shown in figure 2. The groove (16) vertically extends into ε thickness (19) of the screw head (12) which includes an outer part inclined face (21) and an inner part inclined face (22) with respect to the central point (15) of the fastener (10). The inner part inclined face (22) is preferably formed with its upper half face in curved shape as shown in figure 2. The outer part inclined face (21) is deeper than half of the thickness (19) of the screw head (12). The base wall (19) at the central point (15) being the deepest portion with respect to the top face of the screw head (12). Within each of the groove (16) is receivable a radially outwardly projecting correspondingly shaped bit portion of the driving tool (14) as shown in figure 3.

The driving tool (14) as shown in figure 3 is, used to apply and remove the fastener (10). The driving tool (14) includes a shank (23) and /ι driving head (24) with respective bits (25) thai engage in and substantially conform to the shape of the recess (13) of the fastener (10). As an

ik (23) is preferably formed in hexagonal section shape for easy fitting into a screwdriver shank to rotationally drive the driving tool (14) about its longitudinal central axis. The shank (23) slot fits into a socket holder (not shown) of the screwdriver shank having an end slot for receiving different sizes of driving heads (24). The driving Head (24) has bits (25) that tapered in cross section and arranged symmetrically with respect to the central axis which correspond with the grooves (16) of the fastener recess (13). In a preferred embodiment of the present invention, three bits (25) are arranged each other with angle of approximately 120 degrees. The number of bits (25) of the driving tool (14) should be corresponding with the number of grooves (16) of the recess (13) of the fastener (10). The inner part inclined face (22) of the fastener (10) groove in V tip enabling the driving tool bit (25) located centered into the recess (13) of the head (12) thereby increasing the fastening and loosening efficiency of the fastener.

The driving tool (14) bits (25) include engaging faces (26) which protrude and are symmetrically spaced around the driving head (24) of the driving tool (14), and driving side walls (27) connecting the adjacent engaging faces (26). Each engaging faces (26) has an inner portion face (26a) and outer portion face (26b) which engage the base wall (19) at the inner part inclined face (22) and outer part inclined face (21) of the recess (13) respectively while the driving side walls (27) of the driving tool (14) engage the side walls (16a) of the recess (13), to convey an effective large torque TO the fastener (10) when the driving tool (14) engages into the recess ( 13) with just a small iotation force. The inner portion face (26a) is also formed with its upper half face in curved shape which matches the cuivature of the inner part inclined face (22) of the recess (13). The entire surface area of the base wall (19) of the recess (13) and the engaging faces (26) of the driving tool (14) are in parallel alignment with each othei resulting in a snug fit for better uip and efficient torque transfer. The driving side

ie driving tool bits (25) are formed with sharp corners (29) which conform to s vertical ridges (28) and end points (17) of the fastener (10) for locking during the turning of the fastener (10) and thus preventing the bit (25) from slipping out even during high resistance to penetration of the fastener (10).

The arms of the driving tool bits (25) are maximized to the edge of the fastener head, thereby increasing torque transfer to the fastener (10). The workability increases as the driving tool bits easily enter into the desired places of the fastener (10). The fastener (10) also attains higher robust and strength structure as the recess void bounded by the shank (11) diameter is minimized thereby increasing metal connectivity of head (12) to shank (11) preventing the head (12) of the fastener (10) being twisted off during high torque application. In the event when the driving tool bit slip out during the operation, it will not create a large pit in the center that will cause fastener failure.

As will be readily apparent to those skilled in the art, the present invention may easily be produced in other specific forms without departing from its essential characteristics. The present embodiments is, therefore, to be considered as merely illustrative and not restrictive, the scope of the invention being indicated by the claims rather than the foregoing description, and all changes which come within therefore intended to be embraced therein.