II. Background of the Invention The provision of uniformly thin layers of adhesive materials is a necessary step in the manufacture of inkjet print heads and other devices having two or more small surfaces bonded together by adhesives. Because of the small sizes of parts used in inkjet print heads and these other devices, it is necessary that the adhesive materials be provided in an amount that is sufficient to provide the required bonding strength, but that is not so much that the adhesive material extends beyond the surfaces to be bonded and into the functional parts of the device. An overflow of adhesive material of this type to surfaces other than the surfaces intended to be bonded together may cause interference with the proper operation of the device.

As an example, in the manufacture of inkjet print heads, surfaces to be bonded by adhesive may be as small as 35 F or less in width and 200 F or less in length. These surfaces are also typically intricate in shape and therefore are potentially very difficult to deal with. For this purpose, a layer of adhesive material no thicker than 2-12 F must be provided. If the layer of adhesive is too thin, there will not be enough adhesive to form a sufficiently strong bond. If the layer of adhesive is much thicker than the range given, there will be too much adhesive and the material will flow outside the bonding surface area.

One apparatus and method currently known to the art for

providing thin layers of adhesive material on a substrate involves the use of a wet film applicator rod, such as that manufactured by Paul N. Gardner Company, Inc. of Pompano Beach, Florida. The wet film applicator rod is a round stainless steel bar tightly wound with stainless steel wire.

The diameter of the rod and wire vary in size depending on the type of application. The diameter of the wire, in the wound form, regulates the thickness of the film to be produced. More particularly, the film thickness is governed by the area of the groove between adjacent turns of wire on the rod.

To produce a thin film of material with the wet film applicator rod, the rod is dragged across the substrate and over an amount of coating, during which time the groove between adjacent turns allows the proper amount of coating to pass through. The amount that has passed through flows out, leaving a smooth, uniform layer on the substrate. The groove area is determined by the size of the wire, hence, the larger the wire, the larger the groove, and the thicker the film left on the substrate. The film thickness is also determined by the speed at which the rod is dragged over the substrate, the pressure applied during the process, the viscosity and temperature of the coating material, and possibly the ambient temperature and humidity.

While the wet film applicator rod is capable of providing thin films of materials, such as adhesive materials, this apparatus and method has a number of disadvantages. For example, the wires require frequent cleaning in order to prevent them from becoming gummed up with adhesive material. The wires also have a tendency to fray after a number of uses. Moreover, the method is very technique-sensitive, i. e., different users will tend to produce films of different thicknesses due to variations in speed, pressure and other variables. Because of this technique sensitivity, it is difficult to properly train a new user of the apparatus.

Another method for applying thin adhesive films to parts involves the use of a roller machine in which wet

adhesive material is compressed directly on a first set of rollers provided on the roller machine. After processing on the first set of rollers, the adhesive material is transferred to a transfer roller. A part is then placed under and in contact with the transfer roller, and is moved at a linear speed that is equal to the angular speed of the transfer roller. As the part rolls under the transfer roller, the adhesive is transferred from the transfer roller onto the surface of the part in contact with the roller.

With this method, it is critical that the part move at the same speed as the transfer roller in order to ensure uniform coverage. Failure to match speeds, which occurs fairly frequently, will result in non-uniform application. In addition, the apparatus frequently must be shut down for cleaning and maintenance.

Accordingly, there exists a need for an improved method and apparatus for providing and applying thin layers of adhesive and other materials having consistent and uniform thicknesses.

III. Summary of the Invention The present invention comprises an apparatus and method for producing thin films of material and for transferring thin films of material from a substrate to a target component. In accordance with a first aspect, a roller press comprises a base and a frame which together support a pair of rollers at an elevation above the base, one roller atop the other roller. An electric motor drives the bottom roller which, in turn, drives the top roller. A tilt arm is attached at one end to a slider capable of linear movement, and at its other end to the frame. Linear movement of the slider imparts a combination of linear and rotational movement to the tilt arm which, in turn, imparts rotational movement to the frame causing the axis of the top roller to rotate around the axis of the bottom roller. As the top roller rotates from its position directly atop the bottom roller, the result is a decrease in the effective weight of the top roller as felt by the bottom roller. This results

in a decrease in the amount of"pinching"pressure provided by the two rollers.

In a second aspect, a method of providing uniformly thin films of highly viscous materials comprises providing an amount of material between two thin sheets and then compressing the two sheets together to cause spreading of the material between the sheets. Compression of the two sheets and the material contained therein may be performed by utilizing the above-described roller press. After compression, the two sheets are pulled apart, leaving an exposed, uniformly thin, and identical layer of the material on each of the two sheets.

In a third aspect, a roller applicator comprises a base and a frame supporting a roller at an elevation above the base. A part carrier assembly is attached to a slider capable of linear movement beneath the roller. The part carrier assembly includes a platform for retaining a part holder, a pair of risers, a forward bar having a first clamp unit, and a rear bar having a second clamp unit. The first and second clamp units are adapted to receive and retain a thin sheet at a distance above the part holder.

In a fourth aspect, a method of applying a thin film of viscous material to a component comprises providing a sheet having the thin film on its bottom surface and suspending the sheet above the component. The sheet and component are then transported beneath a roller that imparts a downward pressure upon the sheet, causing the sheet to come into contact with the component to thereby transfer the thin film from the sheet to the upper surface of the component.

These and other aspects of the present invention are described more fully by reference to this specification and the accompanying drawings.

IV. Brief Description of the Drawings Figure 1 is a side view of a roller press according to an embodiment of the invention.

Figure 2 is a side view of the roller press of Figure 1 in which the roller press is shown in a tilted position.

Figure 3 is a rear end view in cross-section of the roller press of Figure 1.

Figure 4 is a top view of the roller press of Figure 1 with the weight carriage removed.

Figure 5 is a side view of a roller applicator according to an embodiment of the invention.

Figure 6 is a top view of the roller applicator of Figure 5 with the additional weight removed.

V. Description of the Preferred Embodiment A number of subheadings are provided in the following discussion in an effort to provide organization and clarity. In addition, where a given structure appears in several drawings, that structure is labeled using the same reference numeral in each drawing.

While the following discussion describes in detail the presently preferred embodiments of, and preferred methods of implementing, apparatus for providing and applying thin films of adhesive material for use in manufacturing inkjet print heads, those skilled in the art will appreciate that the teaching of this specification is applicable to methods and apparatus for providing and applying thin films generally and, therefore, that the following discussion should not limit in any way the scope of the invention as defined by the appended claims.

A. Roller Press and Methods for Providing Thin Films Figure 1 is a side view of a roller press 10 in accordance with an embodiment of the present invention. The roller press 10 comprises a base 12 having a pair of uprights 14a, 14b attached to and extending perpendicularly upward from the base in parallel relation to each other.

Each upright 14a, 14b is preferably constructed of aluminum, but may also be constructed of steel, cast iron, or other suitable material that is sufficiently sturdy to support the additional components of the roller press described more fully below. Each upright 14a, 14b is attached to the base 12 by screws, welding, or other similar manner. Each

upright 14a, 14b is also provided with a through-hole 16 near its upper end. A first cross-bar 18 (Figure 3) extends between the pair of uprights to connect them together and to maintain their parallel spatial relationship.

The first cross-bar 18 is preferably attached to the interior surfaces of each of the two uprights 14a, 14b by a pair of screws that each extend through the upright into the respective end of the first cross-bar 18. Accordingly, the length of the first cross-bar 18 defines the distance separating the two uprights 14a, 14b. This manner of connecting and supporting the two uprights 14a, 14b is advantageous because it prevents the uprights from twisting about their vertical axes, which would result in a loss of the parallel spatial relation between the two uprights.

A first roller shaft 20 extends through the through- hole 16 of each of the pair of uprights 14a, 14b to be retained by the uprights at an elevation above the base 12 of the roller press. A first roller 22 is mounted on the roller shaft 20. Referring to Figure 3, bearings 24 are interposed between the edge of each of the through-holes 16 and the first roller shaft 20 in order to allow the first roller 22 to rotate freely as it is supported by the pair of uprights.

In the preferred embodiment, the first roller 22 has a diameter of about 7.8 inches and a length of about 8.0 inches. The first roller 22 comprises a cylinder formed of case hardened steel having a weight of approximately 50 lbs or more. It is preferable for the first roller 22 to have a very uniform surface, i. e., that the first roller 22 be as nearly a perfect cylinder as possible, having no crowns or valleys on its surface. As noted above, bearings 24 are provided around the first roller shaft 20 in order to allow free rotation of the first roller 22.

A pair of lower frame sections 26a, 26b is provided with a through-hole 28 in each such section such that one end of the first roller shaft 20 extends through the through-hole 28 of one lower frame section 26a while the other end of the first roller shaft extends through the

through-hole 28 of the other lower frame section 26b. Each of the two lower frame sections 26a, 26b is supported at one end by one of the pair of uprights 14a, 14b in the manner shown in Figure 3. The inward facing surface of each of the uprights 14a, 14b is provided with a circular well 30 that is concentric with the through-hole 16 for the first roller shaft 20. The outward facing surfaces of each of the lower frame sections 26a, 26b is provided with a circular extension 32 that is concentric with the through-hole 28 for the first roller shaft 20, and that is adapted to fit within the circular well 30 of the corresponding upright. A bearing 34 is interposed between the circular extension 32 of each of the lower frame sections and the edge of the well 30 of each of the uprights 14a, 14b, thereby allowing each lower frame section 26a, 26b to rotate about the axis defined by the first roller shaft 20.

Each of the lower frame sections 26a, 26b is thereby retained and supported in oppositely disposed relation to each other by its corresponding upright 14a, 14b at an elevation above the base 12. Referring back to Figure 1, each lower frame section 26a, 26b is generally rectangular in shape, and each has a tab 36a, 36b extending from one corner. A through-hole is provided in the tab 36a, 36b of each lower frame section, for purposes to be discussed below. A window 40 is provided in an upper corner of each of the lower frame sections 26a, 26b, and a second cross-bar 42 is positioned between and attached to each of the two lower frame sections. The second cross-bar 42 thereby provides further support to the two lower frame sections 26a, 26b and maintains their parallel spatial relationship.

The second cross-bar 42 is preferably attached to the interior surfaces of each of the two lower frame sections 26a, 26b by three screws that extend through each of the lower frame sections 26a, 26b into the respective ends of the second cross-bar 42. Accordingly, the length of the second cross-bar 42 defines the distance separating the two lower frame sections 26a, 26b. This manner of connecting and supporting the two lower frame sections is advantageous

because it prevents the lower frame sections from twisting, which would result in a loss of the parallel spatial relation between the two lower frame sections. In addition, this placement of the second cross-bar 42 maintains the rollers 22,54 in a parallel relationship with respect to each other.

A pivot pin 44 extends through each of the through- holes formed in the tabs 36a, 36b of each of the lower frame sections 26a, 26b. Each pivot pin 44 is held in fixed relation to its corresponding lower frame section 26a, 26b by a close fitting hole and screw clamp (not shown) or similar connection.

A pair of upper frame sections 46a, 46b is provided in parallel spaced relation to each other, and with a first through-hole 48 in each such section through which extends one of the pivot pins 44. A snap ring (not shown) or similar connection retains each upper frame section 46a, 46b on its pivot pin 44. The upper frame sections 46a, 46b are thereby retained and supported in oppositely disposed relation to each other by the two pivot pins 44 at an elevation above the base 12. Each upper frame section 46a, 46b is generally triangular in shape, with the first through-hole 48 being located at one corner of the triangle.

At another corner, each upper frame section 46a, 46b is provided with a second through-hole 50 through which extends a second roller shaft 52 which supports a cylindrical second roller 54, to be more fully described below. At a third corner, each upper frame section is provided with a tab 56a, 56b having an adjusting screw 58 mounted therein. Each adjusting screw 58 is capable of being adjusted such that it juts out from the external surface of its respective tab 56a, 56b by a selected and adjustable distance, for reasons to be discussed below.

An optional weight carriage 60 is shown in Figure 1.

The weight carriage 60 comprises a pair of rectangular arms 62a, 62b connected to and extending outward past the end of each of the upper frame sections 46a, 46b. A weight 64 is attached to the end of each arm 62a, 62b and is held in

place by the pair of arms. The weight is interchangeable with other weights of varying sizes, for reasons to be discussed more fully below.

As noted above, a second roller shaft 52 extends through the second through-hole 50 of each of the upper frame sections 46a, 46b to be retained by the upper frame sections at an elevation above the base 12 of the roller press. A second roller 54 is mounted on the second roller shaft 52. Referring to Figure 3, bearings 66 are interposed between the edge of the second through-holes 50 of each of the upper frame sections 46a, 46b and the second roller shaft 52 in order to allow the second roller 54 to rotate freely as it is supported by the pair of upper frame sections.

In the preferred embodiment, the second roller 54 has a diameter of about 7.8 inches and a length of about 8.0 inches, identical to the first roller 22. The second roller 54 comprises a cylinder formed of case hardened steel having a weight of approximately 50 lbs. or more. It is preferable for the second roller 54 to have a very uniform surface, i. e., that the second roller 54 be as nearly a perfect cylinder as possible, having no crowns or valleys on its surface. As noted above, bearings 66 are provided around the second roller shaft 52 in order to allow free rotation of the second roller 54.

As shown in Figure 1, the upper frame sections 46a, 46b are dimensioned so that the distance between the pivot pins 44 and the second roller shaft 52 is such that the second roller 54 sits directly atop and in parallel with the first roller 22. In other words, the length of each of the upper frame sections 46a, 46b is selected such that a right angle is formed by the intersection of a first line perpendicular to the axis of the pivot pins 44 and the axis of the second roller shaft 52, and a second line perpendicular to the axis of the second roller shaft 52 and the axis of the first roller shaft 20. Accordingly, when the pivot pins 44 and second roller shaft 52 are in a horizontal plane as shown in Figure 1, the second roller 54 is positioned directly atop

of and parallel with the first roller 22. In addition, the screws securing the second cross-bar 42 to the lower frame sections 26a, 26b may be loosened in order to adjust the relative orientation of the first roller 22 with respect to the second roller 54. After loosening the screws, the rollers may be placed in parallel and then the screws re- tightened. This process provides a mechanism for compensating for dimensional tolerance variations in the other components of the roller press.

Turning to Figure 4, a drive mechanism 68, such as an electric motor or the like, is attached to an interior surface of one of the lower frame sections 26b. The drive mechanism 68 includes a rotating shaft 70 to which is attached a drive pulley 72. A belt 74 connects the drive pulley 72 of the drive mechanism to a roller pulley 75 attached to the first roller shaft 20. Accordingly, the rotational motion of the drive pulley 72 is translated to the first roller 22 by the belt 74. The drive mechanism 68 thereby causes the first roller 22 to rotate.

A tilt arm 76 is pivotably connected at a first end to the second cross-bar 42 extending between each of the two lower frame sections. The tilt arm 76 may be connected to the second cross-bar 42 by a rivet, a shaft and bearing structure, or the like. At its other end, the tilt arm 76 is pivotably connected to a slider 84 which rides on a screw shaft 90 mounted in the base 12, as described more fully below. The tilt arm 76 comprises a relatively long, straight first portion 78 attached to the slider 84, and a shorter second portion 80 attached to the second cross-bar 42. The second portion 80 includes a curved hump 82 on its upper surface.

The slider 84 comprises a flat support 86 having an internally threaded sleeve (not shown) on its lower surface.

The support 86 rests upon and slides within the base 12. A connector 88 extends upward from the upper surface of the support 86, and serves as the mechanism by which the tilt arm 76 is connected to the slider 84. The screw shaft 90 comprises a threaded rod that is retained within and

supported by the base 12. The screw shaft 90 is provided at one end with a knob 92 having a handle which enables the user to manually turn the screw shaft 90. As the screw shaft 90 is turned, the slider 84 is correspondingly translated along the length of the screw shaft 90 within the base. The base 12, screw shaft 90 and slider 84 together comprise a unit that is commercially available from Velmex, Inc. of Bloomfield, New York. The unit is sold by Velmex, Inc. under the name UniSlide7. The roller press of the preferred embodiment includes a Series B9000 model UniSlide7 unit identified by part number B9027W1-S9-RC.

A feed tray 94 is attached at a first end to each of the lower frame sections 26a, 26b by a pair of rivets or the like. The first end of the feed tray 94 is located adjacent to the point at which the second roller 54 contacts the first roller 22. As shown in the drawings, the feed tray 94 is preferably flat and extends between the two lower frame sections 26a, 26b and outward from between the lower frame sections. A second end of the feed tray 94 is not connected to any other portion of the roller press, thereby allowing the feed tray 94 to rotate about the axis defined by the connections of the feed tray to the lower frame sections 26a, 26b. The bottom surface of the feed tray 94 rests upon the upper surface of the curved hump 82 of the tilt arm 76 (see Figure 1).

A catch tray 96 is attached to both of the lower frame sections 26a, 26b on the exit side of the first and second rollers 22,54, i. e., the side opposite that of the feed tray 94. The catch tray 96 preferably comprises two sections, a first section 98 fixedly attached to the lower frame sections 26a, 26b, and a second section 100 pivotably attached to the first section, as shown in the drawings. A pin 102 extends outward from each side of the second section 100 of the catch tray to rest in a slot 104 provided on the corresponding sides of the first section 98 of the catch tray, thereby allowing the catch tray to pivot.

A lifting mechanism is provided on the roller press for lifting the second roller 54 up and away from the first

roller 22. The lifting mechanism comprises an eccentric shaft 106 that extends through a through-hole 108 provided in each of the lower frame sections 26a, 26b. The eccentric shaft 106 is retained and supported by the two lower frame sections 26a, 26b via a pair of bearings (not shown), thereby allowing the eccentric shaft 106 to rotate about its longitudinal axis. As shown in Figure 1, the eccentric shaft 106 butts up against each of the adjusting screws 58 at each end of the eccentric shaft 106. A handle 110 extends generally perpendicularly from an end of the eccentric shaft 106 outside one of the lower frame sections 26a. As the eccentric shaft 106 is rotated with the handle 110 in the clockwise direction, the eccentric shaft 106 acts as a cam to bias the adjusting screws 58 and upper frame section tabs 56a, 56b upward and to the right (as shown in Figure 1). This causes the upper frame sections 46a, 46b to rotate in the counter-clockwise direction about the axis defined by the pivot pins 44, thereby lifting the second roller 54 out of contact with the first roller 22.

An optional control unit 112 is shown in the Figures.

The control unit 112 is provided with a microprocessor that is programmable to control the operation of the drive mechanism 68. The control unit 112 may also be provided with a second drive mechanism (not shown) that actuates the screw shaft 90 to control the position of the slider 84 on the screw shaft 90 to control the tilt of the roller press, as described more fully below.

The method of operation of the roller press 10 will now be described in the context of providing thin films of adhesive material for use in manufacturing inkjet print heads. The roller press is preferably used to compress a layer of adhesive material between two flat sheets of mylar or the like. The mylar sheets are preferably square or rectangular, having a width that is about the same as, or somewhat less than, the widths of the first roller 22 and second roller 54 of the roller press. Among other advantages, the mylar sheets prevent the adhesive material from coming in contact with the rollers.

To begin with, an amount of the adhesive material (e. g., a cured oxirane resin adhesive) is applied to one of the two sheets of mylar. This application may be made, for example, with a fluid dispensing applicator sold by Asymtek Co. of Carlsbad, California, model number A403B. The fluid dispensing applicator is capable of depositing beads of material having a range of widths and thicknesses.

Typically, a bead of material will be deposited having a width of about 0.100"and a thickness of about 0.060".

After the epoxy material is applied to the first mylar sheet, the second mylar sheet is placed on top of the first sheet, covering the layer of epoxy material and forming a "sandwich"of epoxy material between two sheets of mylar.

After the epoxy sandwich is formed, it is placed in the feed tray 94 of the roller press and fed into the roller press. More specifically, the drive mechanism 68 is engaged, causing the first roller 22 to rotate in the clockwise direction. Since the second roller 54 is in contact with the first roller 22, clockwise rotation of the first roller 22 causes counter-clockwise rotation of the second roller 54. The mylar sheets are then passed between the first roller 22 and second roller 54. During this time, the two rollers"pinch"the mylar sheets, compressing the layer of epoxy material located between the two sheets. The mylar sheets then pass out to the catch tray 96, where they are retained until removal by the user.

The extent of the compression of the epoxy layer during the process is a function of the speed at which the rollers rotate, and of the pressure exerted by the second roller upon the first roller as the mylar sheets pass through the roller press. This pressure is in turn a function of the effective weight of the second roller felt by the first roller at the contact point between the two rollers. For any given second roller, this effective weight of the second roller may be adjusted by the operator by at least two methods described below.

First, an additional weight may be added to the weight carriage 60. This additional weight is imparted to the

second roller 54 by the connection of the arms 62a, 62b of the weight carriage to the upper frame sections 46a, 46b, and from there to the second roller shaft 52. Adding weight to the weight carriage 60 therefore has the effect of increasing the effective weight of the second roller 54 as felt by the first roller 22. Conversely, removal of weight (s) from the weight carriage 60 will have the effect of lessening the effective weight of the second roller 54 felt by the first roller 22.

Second, the effective weight of the second roller felt by the first roller may be decreased by tilting the roller press. Referring first to Figure 1, the roller press is tilted by moving the slider 84 in a linear direction toward the uprights 14a, 14b. Linear movement of the slider 84 in this direction causes the tilt arm 76 also to move in the same linear direction. In addition, however, the forces applied to the two ends of the tilt arm 76 by, respectively, the slider 84 and the second cross-bar 42, cause the tilt arm 76 to have a counter-clockwise rotational motion as well. The net effect is that the tilt arm 76 both moves toward the uprights and raises up. This movement of the tilt arm 76 in turn causes the lower frame sections 26a, 26b of the roller press to rotate in the clockwise direction about the axis of the first roller shaft 20, eventually to the position illustrated in Figure 2. Further adjustment of the slider 84 and tilt arm 76 is possible in order to rotate the second roller 54 a full 90E from the position shown in Figure 1, i. e., such that the first roller 22 and second roller 54 are side-by-side.

When the roller press 10 is oriented as shown in Figure 2, the effective weight of the second roller 54 felt by the first roller 22 is a fraction of the effective weight felt when the roller press is oriented as shown in Figure 1.

Therefore, tilting of the roller press provides a mechanism by which the effective weight of the second roller may be decreased. At the extreme, when the roller press is tilted such that the first roller 22 and second roller 54 lie side by side (in a horizontal plane), the effective weight of the

second roller 54 felt by the first roller 22 would be zero.

As noted above, the control unit 112 may be programmed to partially or fully automate the operation of the roller press. For example, the user may input a degree of rotation and a motor speed, at which point the control unit 112 will cause rotation of the screw shaft 90 to adjust the position of the slider 84, and actuate the drive mechanism 68. The roller press will then be oriented to operate as requested by the user. Other functional capabilities of the control unit are possible, and will be readily recognized by those of skill in the art.

As noted above, the thickness of the layer of epoxy material obtained after passing the mylar sheets through the roller press is a function of several variables, including the initial thickness of the layer applied with the fluid dispensing unit, the speed of rotation of the rollers, and the effective weight of the second roller as felt by the first roller. After passing through the roller press, the epoxy material between the two sheets of mylar will be compressed to a thickness of from 4-24 F, or thicker if desired, which value will depend on the afore-mentioned variables. The two mylar sheets are then pulled apart, either manually or automatically, to obtain two sheets each having an exposed epoxy layer of between 2-12 F thickness.

It has been found through experiment that the epoxy layers located on each of the two mylar sheets after peeling them apart are virtually identical in thickness. This is believed to be due to the fact that surface bonding of the epoxy material to the surface of the mylar sheets predominates over the intermolecular bonds of the epoxy material. Accordingly, as the two mylar sheets are mechanically separated, an equal amount of epoxy material adheres to each of the two sheets, leaving an identical, relatively uniformly thin layer of epoxy on each of the two mylar sheets.

After separation of the mylar sheets, the epoxy layers are allowed to partially cure, during which time the epoxy material tends to flow out and form a uniformly thin layer,

eliminating any"peaks"or"valleys". As noted above, layer thicknesses on the order of 2 F are ideal for use in bonding parts used in the manufacture of inkjet print heads, and are readily obtainable through use of the roller press.

Having described an apparatus and method for providing thin films of, for example, adhesive materials, there will now be described an apparatus and method for applying thin films to small surfaces.

B. Roller Applicator and Methods for Applying Thin Films Figure 5 is a side view of a roller applicator 210 in accordance with an embodiment of the present invention. The roller applicator 210 comprises a base 212, a roller assembly 214 supported at an elevation above the base, and a part carrier assembly 248 slidably mounted onto the base.

The roller assembly 214 comprises a pair of uprights 216a, 216b attached to and extending perpendicularly upward from the base 212 in parallel relation to each other. Each upright 216a, 216b comprises a pair of vertical portions 218 and a horizontal portion 220, the horizontal portion 220 having a"V"-shape on its top surface for reasons to be discussed more fully below. Each upright 216a, 216b also has a through-hole 222 formed in an upper corner. The uprights 216a, 216b are constructed of steel, cast iron, or other suitable material that is sufficiently sturdy to support the additional components of the roller assembly described more fully below. Each upright 216a, 216b is attached to the base 212 by screws, welding, or other similar manner.

A first cross-bar 224 extends between the pair of uprights 216a, 216b to connect them together and to maintain their parallel spatial relationship. The first cross-bar 224 is preferably attached to the interior surfaces of each of the two uprights by a pair of screws that extend through the upright into the respective end of the first cross-bar 224. This manner of connecting and supporting the two uprights is advantageous because it prevents the uprights

from bending toward or away from each other, which would result in a loss of the parallel spatial relation between the two uprights.

A pivot shaft 226 extends between the two uprights 216a, 216b and through the through-holes 222 provided in the upper corner of each upright. The pivot shaft 226 is thereby supported by the uprights at an elevation above the base. Bearings (not shown) located in each of the through- holes 222 allow the pivot shaft 226 to freely rotate within the through-holes 222.

A pair of support arms 228a, 228b are attached to the pivot shaft 226, one support arm adjacent to each upright.

Each support arm 228a, 228b comprises a generally rectangular member that extends in a plane parallel and interior to that of its corresponding upright 216a, 216b. A second cross-bar 230 extends perpendicularly between and connects the two support arms 228a, 228b to each other at the ends of the support arms opposite the pivot shaft 226.

The second cross-bar 230 is thus maintained in a parallel, spaced apart relationship from the pivot shaft 226. Each support arm 228a, 228b is further provided with a bracket 232a, 232b near its midpoint between the pivot shaft 226 and the second cross-bar 230. Each bracket 232a, 232b extends beneath its corresponding support arm 228a, 228b and includes a through-hole 234 for supporting a roller shaft 236, as described more fully below.

The roller shaft 236 extends through the through-hole 234 of each of the two brackets 232a, 232b and beyond the outer surface of each of the support arms 228a, 228b.

Bearings are provided in the through-holes 234 of each of the two brackets 232a, 232b to allow the roller shaft 236 to rotate freely while being supported by the two brackets. As shown in Figure 5, the roller shaft 236 is accommodated in the"V"formed in the top surfaces of the horizontal portions 220 of the uprights and is thus not in direct contact with the uprights. This orientation allows the roller shaft 236 to rotate without interference from the uprights.

A roller 237 is mounted on the roller shaft 236. In the preferred embodiment, the roller has a diameter of about 7.8 inches and a width of about 8.0 inches. The roller 237 comprises a cylinder formed of rubber-coated aluminum having a weight of approximately 20 lbs. It has been found by experiment that a relatively hard rubber coating on the roller 237 is preferable to softer rubbers, e. g., rubber having a hardness of about 90 durometer. It is preferable for the roller 237 to have a very uniform surface, i. e., that the roller 237 be as nearly a perfect cylinder as possible, having no crowns or valleys on its surface.

As shown in Figure 5, the second cross-bar 230 rests upon the first cross-bar 224 to hold the roller in position.

An additional weight 238 may optionally be attached to the second cross-bar 230 in order to increase the effective weight of the roller 237, as discussed more fully below.

A slider 240 which rides on a ball screw 242 is attached to and retained within the base 212. The slider 240 comprises a flat support having an internally threaded sleeve (not shown) on its lower surface. The ball screw 242 comprises a threaded rod that is retained within and supported by the base 212. The ball screw 242 is provided at one end with a motor 244 which enables a controller (not shown) to cause the ball screw to turn. As the ball screw 242 is turned, the slider 240 is correspondingly translated along the length of the ball screw 242 within the base 212.

The base 212, ball screw 242 and slider 240 together comprise a unit that is commercially available from THK America of Pleasanton, California. The roller applicator of the preferred embodiment includes a unit manufactured and sold by THK America under part number GL15S05+500L. The THK America unit is provided with a controller (not shown) and a motor 244 to automatically rotate the ball screw 242 to thereby translate the slider 240 along the length of the ball screw 242.

A part carrier assembly 248 is attached to the slider 240, thereby enabling the slider 240 to transport the part carrier assembly 248 along the length of the ball screw 242

and under the roller assembly 214 shown in Figure 5. The part carrier assembly 248 comprises a lower plate 250 that rests upon and that is attached to the top surface of the slider 240. The lower plate 250 is typically square or rectangular in shape. An upper plate 252 is located on and attached to the top surface of the lower plate 250, and is also preferably square or rectangular in shape. Four upwardly extending posts 254a-d are provided on the top surface of the upper plate 252, one post at each of the four corners of the upper plate. The two posts 254a, 254b located on the edge of the upper plate 252 nearest to the roller 237 in Figure 5 are referred to as the forward posts, while the two posts 254c, 254d located on the opposite edge of the upper plate 252 are referred to as the rear posts.

A forward bar 256 extends between and is attached to the two forward posts 254a, 254b of the part carrier assembly. The forward bar 256 is provided with a through- hole 258 at each end through which extends one of the two forward posts 254a, 254b, thereby allowing the forward bar 256 to slide up and down in the vertical direction on the pair of forward posts 254a, 254b. An adjustment screw (not shown) on each end of the forward bar 256 provides the capability of fixing the vertical position of the forward bar 256 on the forward posts 254a, 254b by tightening the adjustment screws. In a similar manner, a rear bar 260 extends between and is attached to the two rear posts 254c, 254d of the part carrier assembly. The rear bar 260 is provided with a through-hole 262 at each end through which extends one of the two rear posts 254c, 254d, thereby allowing the rear bar 260 to slide up and down in the vertical direction on the pair of rear posts. An adjustment screw (not shown) on each end of the rear bar 260 provides the capability of fixing the vertical position of the rear bar 260 on the rear posts 254c, 254d by tightening the adjustment screws.

A raised platform 264 is provided on the top surface of the upper plate 252, between the forward bar 256 and rear bar 260, as shown in Figures 5 and 6. The platform 264 is

further provided with a number of short posts 266 disposed on two sides of the top surface of the platform 264. The posts 266 are preferably located in a line along each of two opposite edges on the top surface of the platform 264, as shown in Figure 6. A part holder 268 is adapted to be retained on the top surface of the platform 264 by two or more oppositely disposed posts 266. The part holder 268 includes a bracket 270 at each end that fits over a post 266 on the platform 264 to hold the part holder 268 in place.

An internal vacuum channel 272 is formed in the part holder, including a side access port and an opening at the bottom surface of the part holder. Accordingly, when the part holder 268 is placed on the top surface of the platform 264, a vacuum may be applied to the vacuum channel in order to further secure the part holder 268 in place on the platform.

Two risers 274a, 274b are provided, one on each of two sides of the platform 264 on the top surface of the upper plate 252. Each riser 274a, 274b is in the shape of a "gooseneck", for reasons to be more fully discussed below.

Each riser 274a, 274b is capable of being adjusted in the horizontal direction by the adjustment screws 276 that attach the risers to the upper plate 252, as shown in Figure 5. Thus the horizontal distance separating each riser 274a, 274b from the platform 264 may be adjusted.

A first clamp unit 278 is provided on the forward bar 256 while a second clamp unit 286 is provided on the rear bar 260. As described below, the two clamp units together provide a mechanism for retaining a thin sheet 302, such as a sheet of mylar, in a position above the part holder 268 held on the platform 264 of the upper plate 252. The first clamp unit 278 comprises an eccentric shaft 280 having a handle 282 extending generally perpendicularly from one end of the shaft. The eccentric shaft 280 is attached to the forward bar 256 such that a gap is provided between a surface of the forward bar 256 and the eccentric shaft 280.

A strip of o-ring material 284 or similar material is embedded in the surface of the forward bar 256 within the gap, but does not completely fill the gap. As the handle

282 of the eccentric shaft 280 is rotated, the eccentric shaft 280 acts as a cam to come in contact with and clamp tightly against the strip 284 on the surface of the forward bar 256. Accordingly, a thin sheet 302 may be held in place by the first clamp unit 278 by placing an end of the thin sheet 302 in the gap and then rotating the eccentric shaft 280.

The second clamp unit 286 operates in a manner similar to the first clamp unit 278, but the second clamp unit includes an optional adjustment mechanism. More particularly, a clamping plate 288 is connected to the rear bar 260 by an air cylinder 290 having an external port for pressurizing the air cylinder 290 from an external source (not shown). A spring 294 is provided in the air cylinder 290 such that the spring 294 biases the air cylinder 290 open, i. e., the spring 294 biases the clamping plate 288 away from the rear bar 260. As air is injected into the air cylinder 290, the air pressure compresses the spring 294, which increases the force biasing the clamping plate 288 away from the rear bar 260. A given measured air pressure in the air cylinder 290 will therefore correspond with a certain amount of force biasing the clamping plate 288 away from the rear bar 260.

The second clamp unit 286 is further provided with a second eccentric shaft 296 having a second handle 298 extending generally perpendicularly from one end of the second eccentric shaft 296. The second eccentric shaft 296 is attached to a top surface of the clamping plate 288 such that a gap is provided between the clamping plate 288 and the second eccentric shaft 296. A strip of o-ring material 300 or similar material is embedded in the surface of the clamping plate 288 within the gap, but does not completely fill the gap. As the handle 298 of the second eccentric shaft 296 is rotated, the second eccentric shaft 296 acts as a cam to come in contact with and clamp tightly against the strip 300 on the surface of the clamping plate 288. A thin sheet 302 may thereby be held in place by the second clamp unit 286 in a manner similar to that described above for the

first clamp unit 278.

Accordingly, a thin sheet 302, such as a sheet of mylar, may be retained in a position above the part holder 268 held on the platform 264 of the upper plate 252. A first end of the thin sheet 302 is first inserted into the gap between the forward bar 256 and the eccentric shaft 280 of the first clamp unit 278, where it is clamped in place by rotating the handle 282. The other end of the thin sheet 302 is then inserted into the gap between the clamping plate 288 and the second eccentric shaft 296 of the second clamp unit 286, where it is clamped in place by rotating the handle 298 of the second clamp unit 286. The thin sheet 302 is thereby held in place above the part holder 268.

The tautness of the thin sheet 302 may then be adjusted with the adjustment mechanism of the second clamp unit 286.

This is accomplished by adding air to the air cylinder 290 to a pre-determined pressure level which corresponds to a desired spring force from the spring 294 biasing the clamping plate 288 away from the rear bar 260. The desired spring force is selected so as to provide the desired degree of tautness of the thin sheet 302 as it is retained between the first and second clamp units.

A hinge 304 is provided at one end of the upper plate 252. The hinge 304 allows a portion of the upper plate 252, including the posts 254a-d, forward bar 256, rear bar 260, and risers 274a, 274b to be swung up and away from the part holder 268 retained on the platform 264, thereby allowing access to the part holder 268. In this way, the part holder 268 may be attached or removed from the platform 264 while a thin sheet 302 is clamped onto the part carrier assembly 248.

Although not shown in the drawings, the part holder 268 is constructed in a manner that allows it to hold a part in place while the roller applicator 210 is in operation. For example, the part holder 268 may be constructed to hold a part for an inkjet print head in place in order to transfer a thin film of epoxy or other adhesive material from a mylar film onto a surface of the part, in the manner described

below.

The operation of the roller applicator 210 will now be described. First, a thin sheet 302 (e. g., mylar) having a thin layer of adhesive material on its bottom surface is clamped in place by the first clamp unit 278 and second clamp unit 286. The tautness of the thin sheet 302 is then adjusted by using the adjustment mechanism for the second clamp unit 286, as described above. The first and second clamp units hold the thin sheet 302 in position a distance above the part retained on the part holder 268. The distance separating the bottom surface of the thin sheet 302 from the part may be adjusted by adjusting the vertical position of the forward bar 256 and rear bar 260, as described above.

Next, a part, such as a part for an inkjet print head, is placed in position on the part holder 268. The part holder 268 is then positioned on the platform 264 and is held in place by the interaction of the brackets 270 of the part holder 268 with the posts 266 of the platform 264. If available, a vacuum may be applied to the vacuum channel 272 of the part holder to more firmly hold the part holder in place on the platform. Access to the platform 264 while the thin sheet 302 is in place is possible by swinging the portion of the upper plate 252 open in the manner described above.

The part carrier assembly 248 is then advanced toward the roller 237 automatically by the controller (not shown) and motor 244 by causing the ball screw 242 to rotate, which causes the slider 240 to move toward the roller assembly 214. As the part carrier assembly 248 passes under the roller 237, the bottom surface of the roller comes into contact with the thin sheet 302 covering the uppermost surfaces of the part carrier assembly 248. The roller 237 thereby imparts a downwardly directed force upon the part carrier assembly 248, forcing the thin sheet 302 into contact with those components located below the sheet.

Accordingly, a layer of adhesive material located on the underside of the thin sheet 302 may be transferred from the

thin sheet 302 to the underlying component (s).

For example, with reference to Figure 5, as the part carrier assembly 248 advances through the roller applicator, the roller 237 first comes into contact with the forward bar 256 and begins to rotate in the counter-clockwise direction as viewed in Figure 5. As the part carrier assembly 248 continues to pass under the roller 237, the roller imparts a downward force on the thin sheet 302 above the first riser 274a, then the part held on the part holder 268, then the second riser 274b, and lastly the rear bar 260. If the adhesive layer is located only on the portion of the thin sheet 302 above the part held on the part holder 268, the adhesive is thereby transferred from the thin sheet 302 onto the part. In this manner, a uniformly thin layer of adhesive material may be applied to the part.

Advantageously, the part carrier assembly 248 can then be passed under the roller 237 in the opposite direction, which has been found through experiment to provide more uniform coverage.

Once the adhesive material has been applied to a first part retained in the part holder 268, an additional part holder 268 containing a second part may be placed in the roller applicator. This is done by swinging the portion of the upper plate 252 open in the manner described above to allow access to the part holder 268. The part holder is then removed, and another part holder 268 containing a second part is placed on the platform 264. The new part holder 268 advantageously may be placed in a different position on the platform by connecting the brackets 270 of the part holder 268 to a different set of posts 266 from the posts used for the first part. The upper plate 252 is then swung closed, and the part carrier assembly 248 is advanced through the roller applicator in the manner described above.

Since the part holder 268 is in a different position, the second part will not contact the thin sheet 302 in the same location as did the first part, and will therefore contact the thin sheet 302 in a location in which some adhesive material still remains.

The adjustability of the part carrier assembly 248 may be utilized to vary the performance of the roller applicator 210. For example, vertical adjustment of the forward bar 256 and rear bar 260 may affect the coverage of adhesive material on the part by changing the distance of displacement of the thin sheet 302 by the roller 237 as the part carrier assembly 248 passes beneath the roller 237.

Further, horizontal adjustment of the risers 274a, 274b toward or away from the platform 264 may also affect performance. Additional adjustments may be made to, for example, the linear speed of the part carrier assembly 248 under the roller 237, the diameter of the roller 237, and the weight of the roller 237. Each of these adjustments may provide differences in the extent and uniformity of transfer of the adhesive material from the thin sheet 302 to the underlying part. Those skilled in the art will recognize that other and further adjustments are also possible.

It has been found that the roller press and roller applicator of the present invention are capable of providing and applying uniformly thin films that are ideal for use in manufacturing small component parts, for example, inkjet print heads. Through use of the apparatus and methods described above, uniformly thin films of adhesive material of from 2-12 F are capable of being produced and applied with a high degree of consistency. Adhesive films having these properties are extremely important to small part manufacturing. Moreover, the roller applicator and roller press apparatus described above are relatively simple to operate and require very little maintenance. These and other advantages over the prior art devices and methods are possible through use of the present invention.

While embodiments, applications and advantages of the invention have been shown and described with sufficient clarity to enable one skilled in the art to make and use the invention, it would be equally apparent to those skilled in the art that many more embodiments, applications and advantages are possible without deviating from the inventive concepts disclosed, described, and claimed herein. The

invention, therefore, should only be restricted in accordance with the spirit of the claims appended hereto or their equivalents, and is not to be restricted by the foregoing specification, drawings, or the description of the preferred embodiments.