Dry mounting press

Abstract

The invention is an improved press for dry mounting photographic prints and the like to a supporting substrate. The press comprises a bed, a heated platen assembly hinged with respect to the bed, and a cross-bar assembly that supports the platen assembly and comprises adjustable means for transmitting closing pressure to the platen assembly at selected points. The platen assembly also is constructed so as to provide a more uniform heating of the work.

Description

This invention relates to presses of the type commonly called dry mounting presses which are used for the mounting of photographic prints, printed matter and the like by means of a heat sealing adhesive.

Usually the heat sealing adhesive is applied in the form of a heat sealing mounting tissue which is placed between the print and the card or substrate to which the print is to be mounted, and these components are bonded together under heat and pressure applied by the press.

The present invention is an improvement of dry mounting presses of the type disclosed in U.S. Pat. No. 2644151, issued June 30, 1953 to T. H. Krueger, which employs a toggle mechanism for raising and lowering the heated platen assembly and a center shaft for transmitting pressure from the toggle mechanism to the platen assembly. The Krueger-type press offers a degree of self-adjustment of platen pressure in the front-to-back direction, and also includes means for adjusting the platen assembly vertically so as to vary the pressure exerted on the work when the press is closed. Nevertheless, the Krueger-type press is limited by non-uniformity of platen pressure due to platen deflection, and such pressure non-uniformity cannot be conviently or substantially eliminated by the aforementioned means for vertically adjusting the platen assembly. The pressure non-uniformity is aggravated when the width of the press is greater than its depth. Furthermore, vertically adjusting the platen assembly to increase or decrease the pressure exerted on the workpiece cannot be effected suitably without first adjusting the means that permit the limited degree of front-to-back self-adjustment. Another problem with prior dry mounting presses is non-uniformity of platen temperature due to conductive and/or radiative heat losses, notably at the margins of the platen. Temperature differences as high as 35.degree.F have been found to occur due to such heat losses. Prior dry mounting presses have other limitations known to persons skilled in the art, including relatively high cost.

Accordingly, the primary object of this invention is to provide a mounting press which overcomes or substantially minimizes the limitations of prior known presses.

Another object is to provide a press construction which is simple to operate and relatively inexpensive to build.

A further object is to provide a press of the character described having the capability of applying pressure substantially uniformly over the entire area of the workpiece.

Still another object is to provide a press of the character described having a novel mechanism for supporting and moving the platen assembly.

A more specific object is to provide a mounting press comprising a novel mechanism for transmitting a closing pressure to the platen assembly, said mechanism being adapted to facilitate adjustment of the closing pressure while allowing the platen assembly to be self-adjusting with respect to front-to-back pressure.

Another specific object is to provide a press of the character described wherein the platen assembly is self-levelling, said press comprising means for transmitting a closing force to the platen assembly at a selected point or points.

Still another specific object is to provide a mechanism for supporting and moving a platen assembly characterized by means for loading the platen assembly so as to minimize platen distortion and thus cause a more uniform pressure distribution with respect to the work.

A further specific object is to provide means assuring a smooth floating action for the platen assembly when closing the press.

These and other objects which are rendered obvious hereinafter are achieved by a press of the character described wherein the platen assembly is operatively connected to the toggle mechanisms by a novel cross-bar assembly that comprises means for transmitting closing pressure to the platen assembly at selected points, said same means being adapted to adjust the magnitude of said closing pressure. In other words, the height adjustment means doubles as a primary pressure loading point or points for the platen assembly. Additionally, the platen assembly is designed to provide a more uniform temperature distribution for the heated platen. Other features and many of the attendant advantages of the invention are described in or rendered obvious by the following description of specific embodiments of the invention which is to be considered together with the accompanying drawings wherein:

FIG. 1 is a side elevation of a preferred embodiment of the invention in the closed position;

FIG. 2 is a plan view of the device of FIG. 1;

FIG. 3 is a side elevation showing the device of FIG. 1 in the open position;

FIG. 4 is an enlarged fragmentary sectional view taken along line 4--4 of FIG. 1;

FIG. 5 is an enlarged sectional view in elevation taken along line 5--5 of FIG. 2;

FIG. 6 is an enlarged sectional view taken along line 6--6 of FIG. 2;

FIG. 7 is an enlarged sectional view taken along line 7--7 of FIG. 2;

FIG. 8 is an enlarged sectional view in elevation taken along line 8--8 of FIG. 2;

FIG. 9 is a plan view, partly in section and on a reduced scale, of the heater element embodied in the platen assembly of the device of FIG. 1;

FIG. 10 is an enlarged fragmentary view taken along line 10--10 of FIG. 2;

FIG. 11 is a plan view of a modification of the invention;

FIG. 12 is a sectional view in elevation taken along line 12--12 of FIG. 11;

FIG. 13 is an enlarged fragmentary view taken along line 13--13 of FIG. 11;

FIG. 14 is a fragmentary plan view of another modification of the invention;

FIG. 15 is a view taken along line 15--15 of FIG. 14; and

FIG. 16 is a diagram of the power and control circuit for the press of FIG. 1.

In the drawings identical parts are referred to by the same numerals.

Referring now to FIGS. 1-3 and 8, the preferred embodiment comprises a bed 2 and a platen assembly 4 which are hinged together and coupled by a toggle mechanism and cross-bar construction as hereinafter described so that the platen assembly may be brought down against the bed as shown in FIG. 1 or raised to an open position as shown in FIG. 3, and also so that the bonding pressure exerted by the platen assembly and bed on the work may be appropriately adjusted.

The bed 2 is a metal casting and is formed with a smooth flat surface 5 which is surrounded by a marginal flange 6 so as to provide a recess or box-like receptacle to receive a resilient mat or body 8. The latter preferably is made of sponge rubber or like material and has sufficient thickness so that it will project above the top edge of flange 6 to provide for full resilient action. The bed is provided with suitable feet 10 for resting the press on a suitable support such as a table.

The toggle mechanism comprises two identical assemblies, one at each side of the press. Each assembly comprises a U-shaped cantilever member 12 comprising a lower arm 14 and an upper arm 16. The lower arm of each of the two members 12 is secured to the bed by means of two studs 18 and 20. In this connection it is to be noted that the underside of the bed casting is formed with a continuous flange 22 that comprises front, rear and opposite side sections that extend parallel to but are offset inwardly of the corresponding sections of flange 6. Additionally, at each of its opposite sides the bed casting is formed with a second flange 24 that is spaced from the corresponding side section of flange 22. The front ends of flanges 24 are connected to the side sections of flange 22 by offset portions 26, while their rear ends are integral with extensions of the rear sections of flange 22. In effect, the side sections of flange 22 and the flanges 24 form a dual wall construction as shown in FIG. 4. The studs 18 extend through matching holes in flanges 22 and 24 and are locked in place by C-type retaining rings 28 that are engaged with grooves in the studs. Studs 20 extend through bosses 30 formed on the underside of the bed casting and are anchored by retaining rings (not shown) in the same manner as studs 18. The feet 10 are anchored in bosses formed at the four junctions of the front, rear and opposite side sections of flange 22.

Referring now to FIGS. 1-4 and 8, the platen assembly 4 comprises a hollow metal casting 34 having a top wall 36 with a convex curvature from front to back and depending front, rear and opposite side walls 38 that are straight and coact with top wall 36 to form a box-like enclosure. The bottom edges 40 of walls 38 are flat and lie in a common plane. Additionally, the casting 34 has two pairs of parallel internal reinforcing ribs 42A and 42B (see FIGS. 2 and 10) that extend from front to back and two other parallel internal reinforcing ribs 43 that extend side to side. Ribs 42A, 42B and 43 are integral with top wall 36 and the front and rear side walls 38. The lower edges of ribs 42A, 42B and 43 are spaced above the plane of the lower edges 40 of walls 38, except that at their midpoints the ribs of 42A and 42B are formed with vertical extensions 45 that directly engage the platen 60 and prevent it from bowing up at its center (only the extension 45 of ribs 42B are visible in FIG. 2). If desired, casting 34 may have additional reinforcing ribs. The two ribs 42A are each located about halfway between the center line extending front to rear of casting 34 and the adjacent side wall 38 of the same casting.

The forward half of the upper wall 36 of casting 34 is formed with a hollow rectangular extension 46 that defines a small housing which is closed off by a cover plate 48. The latter is removably secured to extension 46 by screws (not shown) and acts as a mounting plate for a thermometer 50 and a thermostat light 52. A conventional bimetal thermostat 54 is mounted in the platen assembly as described more fully below. The thermostat is of the type having a rotatable adjustment shaft (not shown) which projects up through a suitable opening in cover plate 48 and has affixed thereto a knob 56 which has a pointer that coacts with a temperature scale 58 provided on the cover plate to indicate the temperature setting of the thermostat. Although not shown, it is to be understood that appropriate temperature values are inscribed on cover plate 48 in association with the graduations of scale 58. Typically the scale will have a temperature range of 150.degree. to 350.degree.F.

The platen assembly also includes a metal platen 60 having a smooth hard bottom surface. The platen is sized so that its edges are flush with the outer surfaces of the front, rear and opposite side walls 38 of the platen assembly casting 34. Overlying and coextensive with the platen is an electrical heater unit 62. Overlying the platen is an insulator member 64 which preferably is a relatively thick sheet of asbestos. The remaining volume of the interior space of casting 34 may be occupied by a mass 66 of insulator wool, e.g. glas wool insulation. The platen is secured to casting 34 by means of screws 68, the latter being screwed into tapped blind holes formed in the platen. The margins of the heater unit are sandwiched tightly between the platen and the bottom edges 40 of walls 38. The casting and platen are both made of the same material, preferably aluminum or an aluminum alloy, so that they will have the same coefficient of thermal expansion.

Referring now to FIG. 9, the heater unit is rectangular in area and comprises two heater sections 70A and 70B each consisting of insulated electrical resistance wire 71 wound about a flat insulating core (not shown). The outer heater section 70A surrounds the inner heater section 70B and each of its four legs has a width of about 1-11/4 inches. Also, heater section 70A comprises resistance wire with a lesser resistivity than the wire of heater section 70B. Preferably heater section 70A is designed to provide about twice the watt density of heater section 70B. The two heater sections may be wired for series of parallel operation (for convenience in FIG. 16, the two heater sections are considered as one). The higher heat density of heater section 70A tends to substantially fully offset the relatively high heat losses that occur by radiation at the edges of the platen. The two heater sections are enclosed in an insulating sheath 72. By way of example but not limitation, the insulating core and sheath of the heater unit may comprise a composite of mica and silicone rubber. In any event, the heater unit is made so that the sheath 72 extends beyond the edges of the outer heater section 70A with the result that the heater unit is bounded by an electrically insulating margin portion 74. The width of the latter is at least equal to and preferably slightly greater than the thickness of the walls 38. By way of example, the walls 38 may have a thickness of one-eighth inch and the margin portion 74 may have a width of about three-sixteenths inch. As a result, the intervening margin portion 74 of the heater unit is sandwiched between the lower edge of casting 34 and the platen and thereby tends to reduce conductive heat loss to the casting 34 from the marginal portions of the platen. The thermostat 54 is located at the front of the platen assembly above and in engagement with the outer heater section 70A. This provides more accurate temperature control.

Referring now to FIGS. 1-4 and 6, the rear ends of cantilever members 12 are connected by a fixed tie rod 80. Mounted on tie rod 80 so that they can rotate but not move axially of the rod are two like bracket or hinge arms 82. Axial movement of arms 82 on tie rod 80 can be prevented by means of retaining rings 83 secured in grooves in the tie rod. As shown in FIGS. 4 and 6, the bracket arms 82 are hollowed out so as to form a channel 86 and have solid transverse sections 84 at their front ends. Still referring to FIGS. 1-4 and 6, the toggle hinge mechanisms each comprise a pair of angulated toggle plates or links 88. The toggle plates are all identical and are formed so that their ends extend at an angle of about 90.degree. to each other and define a recess at one side characterized by a flat side surface 90 that faces front. As seen in FIGS. 2 and 4, each pair of toggle plates is located on opposite sides of the upper arm 16 of one of the cantilever members 12 and the lower ends of the toggle plates are pivotally secured to the arm 16 by means of a pivot stud 92. A C-type retaining ring 94 is mounted in a groove in each stud so as to prevent the latter from coming out. Preferably spacers in the form of washers 96 are located on studs 92 between the arms 16 and the toggle plates so as to facilitate pivotal movement of the latter.

Attached to the upper ends of toggle plates 88 is a handle mechanism that comprises a pair of like lever arms 98 and a handle 100 which extends between and is connected to the outer ends of the lever arms. If desired, handle 100 may be connected to lever arms 98 so as to permit it to be rotated on its own axis. The opposite end of each of the lever arms 98 is provided with a lateral extension or ear 102 which is secured to the upper ends of a pair of the toggle plates 88 by a pivot stud 104. Spacers 106 like spacers 96 are interposed between arms 98 and toggle plates 88, and studs 102 are secured in place by C-type retaining rings 108. Additionally the inner end of each lever arm 98 is provided with a hole located substantially along its center line to accommodate a stud 110. The hole for stud 110 is located so that a line connecting it and stud 104 will be at an angle of somewhat less than 90.degree. to the center line of lever arm 98. Each stud 110 projects through its lever arm 98 far enough so that the surfaces 90 of both of the associated toggle plates can be engaged by the stud when the handle is moved so as to close the press.

Studs 110 serve to connect the lever arms 98 to the bracket arms 82 and also a metal cross beam 114. As seen best in FIGS. 7-7, cross-beam 114 is of U-shaped cross-section with a flat upper wall 116 and right-angled front and rear walls 118 and 120. Additionally each end of the cross-beam has a right angled end wall 122 and an interior wall 124 that is spaced from end wall 122 so as to define a channel 126. The rear wall 120 is slotted as at 128 in line with channel 126. The front ends of bracket arms 82 extend through slots 128 into channels 126, the latter being wide enough so that the bracket arms can move relative to the cross-beam. The walls 122 and 124 at each end of the cross-beams are formed with aligned holes (located substantially equidistant from front and rear walls 118 and 120) to accommodate studs 110 which also extend through transverse bores formed in the solid sections 84 of bracket arms 82. The portions of studs 110 that connect the cross-beam and the bracket arms have a reduced diameter so as to form a shoulder 130 (FIG. 4) that engages the outer surface of end wall 122. A C-type retaining ring 132 is affixed in a suitable groove at the inner end of each stud 110, the C-rings and shoulders 130 coacting with the adjacent surfaces of interior wall 124 and end wall 122 to prevent the stud from moving axially while permitting it to rotate in those walls and the bracket arms 82.

The cross-beam 114 supports the platen assembly 4, this being achieved by connections at two spaced points. Referring now to FIGS. 1-3 and 5, the casting 34 of the platen assembly is formed with two bosses 134 on its upper surface, each boss being located half-way between the front and rear ends of the casting and about half-way between the front-to-rear center line of the casting and one of the two opposite sides. Bosses 134 have flat upper surfaces and secured to each such surface by a pair of cap screws 136 that are mounted in tapped holes in the bosses and casting 34 is a mounting plate 138 to which is welded or swaged a threaded load-applying stud 140. Considering the platen assembly as a beam, it is preferred that the studs be located exactly half-way between the front and rear ends of casting 34 and a distance from the adjacent side equal to the width of the press (which is the horizontal dimension in FIG. 2) divided by approximately 4.5.

Screwed onto each stud 140 is an adjusting member in the form of a bushing or hollow shaft 142. The latter is internally threaded so that it can be screwed up and down on stud 140. The cylindrical outer surface of bushing 142 has a threaded section 144, and a reduced diameter end section that is knurled as shown at 146 to facilitate rotation by hand. The remaining portion of its outer surface, which extends for about half its length, is smooth except for two circumferential grooves sized to accommodate a C-type retaining ring 148. In FIG. 5, ring 148 is shown mounted in the upper groove which is not visible but corresponds to groove 150 in the corresponding bushing 142 of FIG. 12. The second lower groove is identified by numeral 152. Mounted on each bushing 142 is an annular dishshaped spring washer 154 of the type commonly known as a Belleville washer. The latter element rests on retaining ring 148 which acts as a shoulder or stop. Screwed onto the threaded section 144 of each bushing is an adjusting nut or collar 156 which preferably has a cylindrical outer surface that is knurled as shown at 158 to facilitate turning by hand. The cross-beam 114 is provided with two openings 160 in its upper wall 116, with each hole being located so as to be concentric with one of the studs 140. Thus openings 160 are spaced from one another the same amount as studs 140. Openings 160 are oversized with respect to the bushings 142 and the upper wall 116 of the cross-beam is raised on both sides around each of the openings so as to provide flat annular shoulders 162 and 164 for engagement by washer 154 and nut 156 respectively.

As is obvious from the foregoing description, the studs 140, bushings 142, washers 154, retaining rings 148 and nuts 156 support the platen assembly from cross-beam 114 and constitute mechanisms for adjusting the height of the platen assembly. Also the cross-beam and hence the platen assembly are capable of rotation on a pivot axis provided by pivot studs 110. Since the platen assembly pivot axis is located substantially at its balance point, the mechanism to the extent described will permit the platen assembly to hang horizontal or tilt in one direction or another when the press is opened. Accordingly provision is made for limiting pivotal movement of the platen assembly. Referring now to FIGS. 4 and 6, the upper surface of the forward end of each of the bracket arms 82 is provided with two mutually spaced depressions or cavities 166 for receiving two resilient blocks 168 that are formed of a suitable natural or synthetic elastomer. Preferably blocks 168 are sized so that when seated in cavities 166 they will both lightly engage the upper wall 116 of cross-beam 114, i.e. they are sized so that they need not be compressed at all or to any substantial degree in order to fit as shown in FIG. 6. However, they may be made slightly oversized so that they will be under some degree of compression when installed as in FIG. 6. The important thing is to limit free play between the cross-beam and the bracket arms in the direction of the arrow in FIG. 6, and to damp movement of the cross-beam so that the platen assembly will not pivot freely and instead will be inclined as shown in FIG. 3 when the press is opened. Blocks 168 may be cemented to the cross-beam or bracket arms if desired and also the two blocks 168 at each end of the cross-beam may be formed integral with each other.

Referring now to FIGS. 2 and 7, the cross-beam 114 also acts as a housing and support for an ON-OFF switch 170 and an ON-OFF indicator light 172, both of which are mounted in its upper wall 116. Additionally it houses a solid state relay 174 which is bolted to its rear wall 120. The latter acts as a heat sink for the relay. Switch 170 preferably is of the type having a V-shaped pivotal operating button 176, but other types of ON-OFF switches obviously may be used. For reasons of safety, the bottom of the cross-beam in the region of switch 170, light 172 and relay 174 is closed off by a removable panel 178 which is secured by screws (not shown) to the rear wall 120 of the cross-beam. As seen in FIG. 7, panel 178 also acts as point of attachment for one end of a stretch-type coiled electrical cable 180 which is used to connect switch 170, light 172 and relay 174 into a circuit with heater unit 62 and thermostat 54. The other end of cable 180 passes through a hole in the upper surface of platen assembly casting 34 and is connected to the thermostat and heater unit. A power cable 182, which is connected to switch 170 and light 172, extends along the channel defined by cross-beam 114 and is bent rearward so as to extend along the channel 86 of the right-hand bracket member 82 as seen in FIG. 2. The power cable extends out of the rear end of the bracket arm and is provided with sufficient length for its free end to be conveniently plugged into a conventional wall outlet. Small brackets (not shown) are used to hold cable 182 close against the cross-beam and bracket arm for reasons of safety and appearance.

FIG. 16 shows the electrical control circuit for the above described press. The heater unit 62, ON-OFF switch 170 and relay 174 are connected in series between two input terminals 186 which are connected by power cable 182 to a suitable A.C. power source. The relay 174 comprises a triac having its T.sub.1 and T.sub.2 terminals connected in series with switch 170 and heater unit 62, while its gate electrode is connected through a suitable biasing resistor 184 and thermostat switch 54. The thermostat light 52 is connected across the heater unit while the power ON light 172 is connected in series with switch 170. With this unit, closing of the thermostat switch causes the triac to conduct and thereby cause heater 62 and light 52 to be energized. It is to be noted that the magnitude of the current carried by the thermostat is relatively low, the heavy current load for the heater being carried by the triac rather than the thermostat. By way of example, 8 to 15 amperes are carried by the heater unit while only a 1/2 to 11/2 ampere signal is passed by the thermostat. This has the effect of materially prolonging thermostat life.

These are the advantages of the press described above. For one thing, when the handle is moved backward to the position of FIG. 3, the platen assembly is raised as a consequence of the pivot axis of the cross-beam, i.e. studs 110, being swung upwardly (clockwise in FIG. 1) about the axis provided by studs 104. As seen in FIG. 3, the extent of rearward movement of handle 100 is limited by its engagement with the upper surfaces of the rear ends of bracket arms 82. When the handle is moved forward again (FIG. 2) reverse operation occurs and the platen assembly is lowered to close the press. The toggle plates undergo limited movement on the pivot studs 92 when the platen assembly is raised and lowered. When the platen assembly is lowered to close the press it can be locked in the closed position by the sample expedient of forcing the handle down far enough to locate the axis of pivot studs 110 rearwardly of the line joining the axes of pivot studs 92 and 104. In other words the press is held closed by virtue of the overcentering of pivot studs 110. When the press is locked in the closed position, studs 110 engage surfaces 90 of toggle plates 88. A similar overcentering action holds the press open. In this connection note that in FIG. 3 the pivot studs are again to one side of a line joining the axes of pivot studs 92 and 104. On closing the press, the resilient blocks 168 permit the platen assembly to pivot relative to bracket arms 82 so as to automatically level itself when pressed against the bed.

The cross-beam 114 and the height adjusting mechanisms (elements 140, 142, etc.) constitute the means for transmitting closing pressure to the platen assembly from the toggle mechanisms. The toggle mechanism does not apply closing pressure to the platen assembly through tie-rod 80 and bracket arms 82. As a consequence the hinge construction provided by tie rod 80 and bracket arms 82 need not be heavy. Adjustment of the pressure exerted on the work by the press is achieved by backing off nuts 156 and then screwing bushings 142 up or down on studs 140 so as to lower or raise the platen assembly relative to cross-beam 114. The two bushings are turned so that equal pressure is exerted by the cross-beam on both studs 140. Once the correct pressure is achieved, the nuts 156 are tightened up enough so as to lock the bushings against rotation. The height adjusting mechanisms permit the platen pressure to be adjusted correctly for laminating as well as dry-mounting. Also the height adjustment mechanisms allow the press to accept relatively thick as well as relatively thin work-pieces so that, for example, the press may be used to dry-mount a print to a 1/2-inch substrate. Typically the threaded sections 144 of bushings 142 are long enough to permit a 1 inch height adjustment for the platen assembly. The two grooves 150 and 152 in the bushings allow the same height adjustment units to be used in different size presses. A particular advantage of the height adjustment capability of the press is that the height of the platen assembly can be varied without having to adjust any other mechanism. The most important advantage of the invention is that use of the cross-beam permits loading the press so as to reduce the variations in pressure along the full area of the platen to less than 1 psi, which is a marked improvement over the Krueger-type press which typically has a pressure variation of 3 psi and greater. The remaining deflection of about 1 psi or less is due to deflection of the bed and manufacturing tolerances. It has been found that the optimum loading points are those which produce minimum platen deflection across the width of the press, and those have been found to be at distances from the sides of the platen assembly equal to the latter's width divided by about 4.5.

The cross-beam construction can be expanded to permit loading at more than two points for optimization of platen loading. This modification of the invention is shown in FIGS. 14 and 15. In this case the cross-beam 114 is provided with two pairs of front and rear extensions 190 and 192, and each extension is provided with an opening corresponding to opening 160 for accomodating a height adjustment unit like that shown in FIG. 5. The platen casting 34 is formed with a two elongate bosses 134A and two threaded studs 140 are secured to each boss. The rear studs 140 are located so as to be spaced from the rear end of the platen assembly a distance equal to the depth of the platen assembly divided by approximately 4.5 and the front studs are spaced the same distance from the front end of the assembly. The studs 140 on the left of FIG. 14 are spaced from the left hand side of the platen assembly a distance equal to the width of the assembly divided by 4.5 and the right-hand studs 140 are correspondingly spaced from the right hand side of the platen assembly. With this arrangement, loading forces are transmitted from the cross-beam to the platen assembly at four distinct points. This modification produces a better pressure distribution on the workpiece than the device of FIG. 1, but is more expensive to manufacture.

The cross-bar loading arrangement also may be modified so as to transmit the loading force to the platen assembly at a single point. This modification of the invention, which is shown in FIGS. 11-13, is advantageous for relatively small size presses which usually have less of a platen deflection problem.

Referring now to FIG. 11-13, the cross-beam 114 has a single opening 160 located equidistance from its opposite ends for accomodating a bushing 142, and the platen assembly casting 34 has a single boss 134B located at its centerpoint to which is attached the threaded stud 140 on which the bushing is mounted. FIG. 12 illustrates the retaining ring 148 for the spring washer 154 mounted in the lower groove 152 of the bushing. As is obvious, since only a single height adjustment unit connects the platen assembly to the cross-beam, the platen assembly will tend to rotate about the axis of bushing 142 when the lock nut 156 is loosened. Therefore, means are provided is prevent such rotation so as to assure that the sides of the platen will line up with the sides of the bed when the press is closed. The means for restraining the platen assembly against rotation comprises two bosses 194 formed on the upper surface of platen casting 34 adjacent each side and behind its side-to-side center line, plus two rear extensions 196 on the cross-beam which are aligned with bosses 194. Extensions 196 have cavities 198 on the bottom sides. Secured to the upper end of each boss 194 by a screw 200 is a rubber plug 202. Plugs 202 extend up into cavities 198 and coact with the surrounding surfaces of extensions 196 to prevent the platen assembly from rotating on the axis of bushing 142. Obviously only one extension 196, one boss 194 and one rubber plug 202 are required to prevent rotative movement of the platen assembly, but the dual arrangement shown in FIG. 11 is preferred for reasons of symmetry. As shown in FIGS. 11 and 13, the bracket arms 82 are spaced inwardly of the sides of the press far enough to permit the provision of extensions 196 on the cross-beam. For this purpose it is preferred that the cross-beam be formed with an additional internal wall 127 (FIG. 13) at each end for mounting the studs 110. The rear wall of the cross-beam is slotted between walls 124 and 127 as shown at 129 for accommodating the forward ends of bracket arms 82.

Except as may be otherwise noted above, the modifications of FIGS. 11-13 and FIGS. 14 and 15 are constructed and operate in the same manner as the preferred embodiment of FIGS. 1-10 and 16.

It is recognized that still other changes may be made without departing from the principles of the invention.

Claims

What is claimed is:

1. A press comprising:

a bed;

a platen assembly positioned above said bed;

hinge arms pivotally connected to the bed;

a cross-beam extending transversely of said hinge arms over said platen assembly;

pivot means connecting said hinge arms to said cross-beam so as to allow relative pivotal movement between said cross-beam and said hinge arms;

height-adjusting means located between and spaced from said hinge arms for locking said platen assembly to said cross-beam;

toggle links pivotally connected to opposite sides of said bed;

lever arms pivotally connected to said toggle links;

means connecting said cross-beam to said lever arms; and

means for pivoting said lever arms relative to said toggle links so as to selectively raise and lower said platen assembly into open and closed positions respectively relative to said bed; said height adjusting means comprising a stud affixed at one end to said platen assembly, and rotatable threaded means screwed onto said stud connecting said cross-beam to said stud, whereby the spacing between said cross-beam and said platen assembly can be varied by rotating said threaded means on said stud.

2. A press according to claim 1 wherein said rotatable threaded means comprises a nut and a bushing with interior and exterior screw threads, said bushing being screwed onto said stud and extending up through an oversized hole in said crossbeam, said bushing having a flange engaging the underside of said cross-beams said nut being screwed onto said bushing and coacting with the upper side of said cross-beam whereby to lock said bushing against rotation on said stud.

3. A press according to claim 2 wherein said flange is a spring washer removably mounted on said bushing.

4. A press according to claim 3 including means on said bushing providing a shoulder for engaging said spring washer and holding it against said cross-beam.

5. A press according to claim 1 wherein said stud and the said hole in said cross-beam are located substantially half-way between the opposite ends of said cross-beam.

6. A press according to claim 5 further including cooperating means carried by said cross-beam and said platen assembly for preventing rotation of said platen assembly and stud relative to said cross-beam.

7. A press according to claim 1 including a second like height-adjusting means connecting said platen assembly to said cross-beam, said first-mentioned height-adjusting means having its stud located intermediate one end and the midpoint of said cross-beam and said second height-adjusting means having its stud located intermediate the opposite end and the midpoint of said cross-beam.

8. A press according to claim 2 including a second like height-adjusting means connecting said platen assembly to said cross-beam, said first-mentioned height-adjusting means having its bushing extending up through a hole in said cross-beam which is located between one end and the midpoint of said cross-beam and said second height-adjusting means having its bushing extending up through a hole in said cross-beam located intermediate the opposite end and the midpoint of said cross-beam.

9. A press according to claim 8 wherein said holes are located at equal distances from said midpoint.

10. A press according to claim 2 wherein the upper end of said bushing is adapted for turning said bushing on said stud.

11. A press according to claim 1 comprising four of said height-adjusting means connecting said platen assembly to said cross-beam, first and second ones of said height-adjusting means being located at one side of said cross-beam and the third and fourth ones of said height-adjusting means being located at another side of said cross-beam, said first and third height-adjusting means being disposed on one side of and spaced equidistant from a line intersecting the midpoint of said cross-beam at a right angle and said second and fourth height-adjusting means being disposed on the opposite side of and spaced equidistant from said intersecting line, with said line being equidistant from said first and second height-adjusting means.

12. A press according to claim 1 further including resilient means interposed between said cross-beam and at least one of said hinge arms for limiting relative movement between said cross-beam and said hinge arms.

13. A press comprising:

a bed;

a platen assembly located above the bed;

first and second hinge arms pivotally connected to the bed at opposite sides thereof;

a cross-beam extending transversely of said hinge arms over said platen assembly;

height-adjusting means located between and separate from said hinge arms for connecting said platen assembly to said cross-beam, said height-adjusting means comprising a threaded stud affixed to said platen assembly and threaded means screwed into said stud for connecting said stud to said cross-beam so that said platen assembly will move up and down with said cross-beam;

first and second toggle links;

first and second pivot studs pivotally connecting one end of said first and second toggle links respectively to said opposite sides of said bed;

first and second lever arms at said opposite sides of said platen assembly;

third and fourth pivot studs pivotally connecting the other ends of said first and second toggle links to said first and second lever arms respectively;

fifth and sixth pivot studs each mounted to an opposite end of said cross-beam, said fifth pivot stud being connected to said first hinge arm and said first lever arm and said sixth pivot stud being connected to said second hinge arm and said second lever arm so as to allow relative pivotal movement among said cross-beam, said hinge arms and said lever arms; and

means connecting said lever arms for pivoting said lever arms relative to said toggle links so as to selectively raise and lower said platen assembly into open and closed positions respectively relative to said bed,

each of said toggle links being angulated and having a recess along one side thereof between its two pivots, said toggle links and said fifth and sixth studs being disposed so that portions of said fifth and sixth studs can move into said recesses to an overcentered relation with said first and second toggle links respectively when said platen assembly is moved into its said closed position by pivotal movement of said lever arms.

14. A press according to claim 13 including third and fourth toggle links,

said first and third toggle links being disposed on opposite sides of said first lever arm and said second and fourth toggle links being disposed on opposite sides of said second lever arm, said third and fourth toggle links being pivotally mounted at one end to said first and second pivot studs respectively and pivotally mounted at the opposite end to said third and fourth studs respectively, said fifth and sixth pivot studs extending in front of said third and fourth toggle links between said lever arm and said cross-beam.