US3357335A - Clamping and sequencing arrangement for vacuum printing frame - Google Patents

Description

1967 D. T. BLATHERWICK 3,357,335

CLAMPING AND SEQUENCING ARRANGEMENT FOR VACUUM PRINTING FRAME Filed Feb. 23, 1965 3 Sheets-Sheet 1 DeiberfT 'siafigev'wi k M Wa /1% fl-Fro KUQELYJ Dec. 12, 1967 D. T. BLATHERWICK 3,357,335

' CLAMPING AND SEQUENCING ARRANGEMENT FOR VACUUM PRINTING FRAME 5 Sheets-Sheet 2 Filed Feb. 25, 1965 I I w I a 0 I u I v m. w M? k .2 m T m a 4 L o w aw Iw r 6 BM i 1% 5 w 1009 0 Z Z all am/w W w M :M ow vw ec. 12, 1967 D. T. BLATHERWICK CLAMPING AND SEQUENCING ARRANGEMENT FOR VACUUM PRINTING FRAME 5 Sheets-Sheet 5 QMW Filed Feb, 23, 1965 W De) barf T Blodfindick United States Patent 3,357,335 CLAMPING AND SEQUENQING ARRANGEMENT FUR VACUUM PRINTHNG FRAME Delbert T. Blatherwick, Woodstock, Ill., assignor to American Photocopy Equipment (Iompany, Evanston, ill., a corporation of Illinois Filed Feb. 23, I965, Ser. No. 434,455 13 Claims. (Cl. 5-76) ABSTRACT OF THE DISCLOSURE A vaccum printing frame for graphic arts purposes swingable between the horizontal and vertical positions having interlocked means for insuring that operations take place semi-automatically in a desired sequence and including cover counterweighting means.

In the preparation of offset printing plates the plate and positive are inserted into a printing frame where they are held together under glass for exposure to intense light. Vacuum is employed for forcing the combined plate and positive into intimate contact with the glass surface. The frame is swung from a horizontal loading position to a vertical exposed position.

It is an object of the present invention to provide a novel clamping and sequencing arrangement for a vacuum printing frame which is positive and reliable and which enables plates to be exposed rapidly on a production basis with a minimum of care and attention on the part of the printing frame operator. In this connection it is an object to provide a clamping and sequencing arrangement which insures that the loading, evacuation, tilting and exposing sequence is carried out semi-automatically and consistently from plate to plate reducing the possibility of spoiling a plate due to inadvertence or forgetfulness on the part of the operator. In this connection it is also an object to produce a printing frame clamping arrangement in which the frame once clamped cannot be unclamped without completing the operating cycle, i.e., without swinging the frame back into horizontal unloading position. Indeed, it is one of the features of the present device that the vacuum is automatically released and the frame is automatically swung open upon restoration to horizontal position.

It is another object of the present invention to provide a vacuum printing frame and control arrangement therefor which is safe and which overcomes the hazards to both the equipment and the operator which might be encountered in the operation of frames of more conventional type.

It is still. another object of the invention to provide a clamping and sequencing mechanism which includes a novel interlock arrangement which cannot be defeated or overpowered by the machine operator and which is capable of withstanding long hard usage under production conditions without maintenance or adjustment.

Other objects and advantages of the invention will become apparent upon reading the attached detailed description and upon reference to the drawings in which:

FIGURE 1 is a perspective view of a printing frame apparatus constructed in accordance with the present invention.

FIG. 2 is a side view of the printing frame proper, unclamped and open in readiness for loading but with the wall of the frame partly broken away to reveal the internal details.

FIG. 3 is a fragmentary perspective of the mechanism shown in FIG. 2.

FIG. 4 is a fragmentary section looking along the line 4-4 in FIG. 3.

3,357,335 Patented Dec. 12, 1967 FIG. 5 is a fragmentary section looking along line 5-5 in FIG. 1.

FIG. 6 is a fragmentary section looking along line 66 in FIG. 3.

FIG. 7 is an enlarged fragmentary section corresponding to a portion of FIG. 2.

FIG. 8 is a side View of the clamping frame similar to FIG. 2 but showing the frame in closed and clamped condition in readiness for swinging to the vertical exposing position.

FIG. 9 is a fragmentary view of the rear portion of the mechanism at the beginning of swinging movement.

FIG. 10 is a fragmentary view similar to FIG. 9 but showing the lifting of the rear latch which occurs upon restoring the frame to horizontal position.

While the invention has been described in connection with a preferred embodiment, it will be understood that the invention is not limited to such embodiment and that I intend to cover the various alternative and equivalent arrangements which are included within the spirit and scope of the appended claims.

Turning now to the drawings, FIGURE 1 shows a vacuum printing frame apparatus having a frame or housing 10 which includes a pair of spaced supports 11, 12. Mounted between the spaced supports is a printing frame 15 having a base portion 16 and a glass cover 17, the cover being hinged to the base portion by a hinge 18 at the rear edge. The cover is provided with a handle 19 for swinging the cover upwardly, i.e., to open the frame when thefrarne is horizontal.

For the purpose of supporting the frame 15 for swinging movement between the horizontal loading position and the vertical exposing positions, shown dotted in FIG. 2, a transverse shaft 20 is provided at the underside of the base portion in a substantially centered position, projecting at each side to form trunnions 21, which are seated in brackets 23, secured to the supports 11, 12. The brackets constitute a simplified form of journal bearings and, being open at the top, permit the frame 15 to be unstepped for easy removal when removal becomes necessary.

Prior to discussing the clamping and sequencing arrangement forming the substance of the present invention, it will be helpful to have in mind the internal construction of the printing frame. For the purpose of sealing the cover to the base a peripheral gasket 30 (FIG. 5) is provided surrounding a blanket 31 formed of rubber or the like covered with small protuberances 32. When the glass cover is seated on the gasket the blanket defines an evacuated space 33 which communicates through a vacuum line 34 to a vacuum pump 35 which has a motor 37 under the control of a switch 36. It will be apparent that when the vacuum pump is turned on air is withdrawn through the line 34 forming a vacuum in the space 33 and causing the blanket to be powerfully attracted toward the glass cover plate. Thus during normal use of the device an unexposed plate and positive are placed upon the blanket and when the cover is closed and clamped, application of the vacuum causes the blanket to press the pair plate and positive against the surface of the cover thereby insuring a sharp image when the frame is subsequently rocked into vertical position and exposed to a high inten sity light source. The light source, which may, for example, be in the form of mercury vapor lamps, is mounted in the rear portion of the housing 10 and does not form a part of the present invention. The vertical position of the frame is defined by suitable stops 33 formed by the supporting members II, 12 while the horizontal position for the frame may be defined by stops 39.

In accordance with the present invention means are provided movable into alternate positions for locking the base member 16 of the frame in horizontal position during loading and for clamping the cover onto the base, with the locking means being automatically released incident to the clamping so that the frame is then free to swing upwardly toward its exposing position. Thus I provide along the sides of the base portion clamping bars mounted for endwise reciprocating movement engaging a clamp at the forward end and a horizontal lock at the rear end. In the discussion which follows attention will be given to the mechanism along one side of the base portion, the near side as shown at FIGS. 1 and 2, and it will be understood that the mechanism is duplicated at both sides of the frame. The clamping bar, indicated at 40 in the drawings, is supported in pairs of guide rollers 41 at the front of the frame and 42 at the rear. The rollers are secured to plates mounted on the base 16 by screws 43. Each roller is grooved so that the bar 40 is held captive. For clamping the cover when the clamping bar 40 is in its forward position, a clamping plate 50 is secured to the cover by screws 51. At its lower end the clamping plate carries a roller 52 on a pin 53, the roller being preferably in the form of an antifriction. bearing having a circular outer race.

When the cover is separated from the base, forward movement of the bar 40 is prevented by a front lock 55 in the form of an arm which is pivoted at 56 and biased upwardly against a stop 57 by a spring 58 into obstructing position. When the cover is lowered (FIG. 7), the roller 52, engaging the lock 55, moves it downwardly out of the way of the bar 40 so that the bar 40 is free to move forwardly into the clamping position shown in. FIG. 8 in which the front end of the bar overlies the roller 52.

For applying forward. clamping movement to the bar 40, a manual operating lever 60 is provided at the center of the base having a shaft 61 which extends the width of the base and which. terminates, in the mechanism under discussion, in an arm 62. Arranged in the path of movement of the arm 62 is a roller 65 mounted on a pin 66 with the roller being spaced outwardly from the bar sufficiently to clear the guide 41. It will be apparent, then, that downward swinging movement of the manual lever 60 causes the arm 62 to engage the roller 65 to produce the desired clamping movement of the bar.

For the purpose of locking the frame in horizontal position when the bar 40 is moved rearwardly, a stop member 70 is provided on the supporting structure in position to obstruct downward movement of the rear end of the bar as shown in FIG. 2. For the purpose of engaging the stop member 70, a roller 72 is secured to the bar by a pin 71. The dimensions and clearances are such, as shown in the drawings, that the bar 40 performs either the horizontal locking function (FIG. 2) or a clamping function (FIG. 8) and since the same member performs both functions,

positive interlocking of the functions is assured.

In accordance with one of the important aspects of the present invention means are provided for maintaining the bar 40 in its clamping position during upward swinging movement of the frame and for causing the bar to move to a clamp-freeing position when the frame is restored to horizontal position. To accomplish this, the bar 40 is biased into clamp-freeing position by a coil spring 80 which is secured to one end 81 to the bar and at the other end 82 to the frame or housing, with a latch and arcuate track being provided at the rear end of the bar for holding the bar, against the force of bias, in the clamping position. Thus referring to the drawings, I employ a latch 90 pivoted to the frame for rocking movement about a pivot pin 91 and having an end face 92 arranged in the path of movement of the roller 72 secured to the bar. The latch 90 is downwardly biased into the position shown in FIG. 9 resting, in active position, on the stop 70. Arranged adjacent the stop surface 92 of the latch and in the path of movement of the roller 72 is an accurate stop member 95 secured to the support or housing 10 and having a surface 96 concentric with the supporting trunnion 21 on the base portion of the frame. In carrying out the in 4. vention the stop surface 92 at the end of the latch is preferably overhanging, i.e., offset from, the surface 96 so that when the roller 72 on the bar completes its cycle, i.e., when the frame is restored to horizontal position, the latch is engaged by the roller causing the latch to be crowded upwardly into a non-engaging position, enabling the roller 72 to slide under the latch and enabling the clamping bar 40 to be restored to a non-clamping position by the spring 80. Such latch movement is utilized to switch off the switch 36 which controls the vacuum pump so that vacuum is released permitting the cover member 17 of the frame to be raised relative to the base.

In accordance with one of the more detailed features of the present invention, the cover 17 is provided with a counterweight so that when the clamp mechanism, and vacuum, are released, the cover 17 swings automatically into open position. Counterweighting is, in the present instance, achieved by springs 100 acting on plates 101 pivoted at 102 the springs being reactively connected to the supporting frame as shown in FIG. 1. Each plate has two rollers 103 and 104 spaced to act in opposition on a bar 107 pivotally connected to the cover 17 at a pin 106 which is located forwardly of the trunnions 21 when. the base is in horizontal position. Thus the springs 100 are not only capable of opening the cover 17 with respect to the base but acts, when the cover and base are clamped together, to provide upward bias for the frame 15 as a whole. In determining the force. of the springs 100, it is preferably suflicient to raise the glass cover 17 against the forces of weight and friction but excessive counterweighting is to be avoided. so as to reduce the damaging imp-act. At each side of the cover 17 is a rubber bumper 105 provided in the path. of movement of the upper edge of the. cover for the purpose of absorbing minor impact without damage to the cover when the cover is swung open. Under normal circumstances the bias simply services to start the upward movement of the cover and the operator or the machine, grasping the handle 19 on the cover, guides the cover into its fully open position for removal of the positive and exposed plate.

It may be noted that the spring, has a large lever arm (the distance between the pins 102, 106) for supporting the cover while only a small lever arm. (the radial distance from pin.10 6 to trunnions 21) biasing the base and cover as a unit with respect to the supporting framework due to the near center location of the trunnions.

Thus referring to FIG. 2, which shows the lever and spring assembly at the near or right-hand side of the machine, the members. 101, 107, taken together form a composite lever pivoted. on horizontal pivot pin 102 secured to the outer frame or support. The lever arm at the input. side of the lever is the perpendicular distance between the spring 100 and the pivot 102 while the effective lever arm of the output side is the radial distance between the pivot 102 and the pin 106 at the end of the lever 107. Since the point of connection 106 is near the center of gravity of the cover, the weight of the cover is assumed by the lever system without any substantial amount of reaction force at, the cover hinge 18. The roller mounting for the lever arm 107, provided by rollers 103, 104, permits the lever arm to accommodate itself to the varying radius of the pin 106 with respect to the lever pivot 102, as the cover is opened and closed. When the cover is closed and clamped in place, the pivot pin 106, to which the biasing force is applied, lies closely adjacent the axis of the trunnions 21 so that only a small amount of spring biasing torque, if any, is applied to the frame as a whole. Since the trunnions 21 are, as shown, positioned near the center of the printing frame, the weight of the frame is substantially balanced when the frame is horizontal, but since the trunnions are adjacent the forward face of the frame, the rearwardly overhanging com ponent of weight, when the frame is approaching the vertical position, is efifective to apply final closing torque,

maintaining the frame seated in its closed position until intentionally tilted therefrom by the operator.

While the operation of the above described mechanism during a complete loading, exposing, and unloading cycle, will be apparent to one skilled in the art, it will be helpful, for the purpose of fully understanding the manner in which the various functions are integrated, to consider a typical operating cycle, with reference particularly to FIGS. 2-10 inclusive. It will be assumed that the frame is initially in horizontal position with the cover upraised. Under such condition, as shown in FIG. 2, the clamping bar 40 is in its retracted position under the urging of the biasing spring 80. The rear latch 90 is upraised and the roller 72 on the clamping bar is blockingly supported on the stop member 70 which is secured to the supporting frame of the machine. Forward movement of the clamping bar 40 is, under such circumstances, precluded since the front latch 55 is in blocking position. Since the rear latch 90 is upraised, the vacuum pump switch 36, which is coupled to this latch, and which is of the normally closed variety, serves to keep the motor 37 deenergized so that no vacuum is applied. Rocking movement of the frame 15 forwardly beyond horizontal position is prevented by the fixed stop 39 on the frame.

After the positive and unexposed plate are inserted into position on the rubber blanket 31 in the base portion of the frame, the cover 17 is manually lowered by the handle 19. Engagement between the roller 52 and the clamping bracket 50 serves, first of all, to depress the front latch 55 out of the way of the clamping bar 40. The manual clamping lever 60 is then pushed downwardly by the operator causing the arm 62 thereof to press against the roller 65 on'the clamping bar forcing the clamping bar forwardly into clamping position against the force of the biasing spring 80. This moves the roller 72 from under the rear latch 90, enabling the rear latch to drop into the position shown in FIG. 8 and releasing the control switch '36 so'that the vacuum pump motor 37 is turned on. Application of vacuum through conduit 34 promptly evacuates the space 33 above the blanket 31, causing the blanket to press the positive and unexposed plate intimately against the under surface of the glass cover. Because of the dropping of the rear latch 90 into obstructing relation with respect to the roller 72 on the clamping bar, the clamping bar is locked in the clamped up condition in readiness for upward swinging of the printing frame. Moreover, the roller 72 at the rear end of the bar 40is moved clear of the horizontal locking member 70 so that the frame is no longer locked in its horizontal position. Because ofthe counterbal'ancing effect of the springs light upward pressure applied to the handle 19 by the machine operator suffices to swing the printing frame toward its vertical position. During the initial portion of this movement the roller 72 on the clamping bar drops off the face of the latch 90 onto the surface 96 of the curved rail 95 on the machine frame. Since the member 95 is concentric with the axis of swinging movement, the interference between the roller 72 and the curved member assures that the clamping bar dd remains in its forward or clamping position during the time that the printing frame is in transit between its horizontal and vertical positions.

The capacity of the vacuum pump 35, as compared to the small volume 33 above the blanket, is sufficient so that substantially complete evacuation of the space 33 occurs in an extremely short space of time, a space of time which may be on the order of one second duration. This insures that the positive and unexposed plate are clamped against the glass cover before the frame has had opportunity to move very farout of its horizontal position. This insures that the positive and unexposed plate will have no opportunity to slip with respect to one another and insures that the plate will be exposed with the positivein the same position as it was originally deposited. Thus there is no reliance upon the operator to manually operate a switch for turning on the vacuum which runs the risk that the switch may be turned on too late so that the plate has an opportunity to slip out of position.

When the printing frame 15 strikes the fixed stop 37 which defines the vertical frame position, the light source is turned on. This may either be done manually or automatically by a switch which is arranged in the path of movement of the frame and actuated as the vertical stop surface 37 is about to be engaged. The duration of the exposure may be either controlled by the operator or may be controlled by an automatic exposure timer and is a matter outside of the scope of the present invention.

Following exposure the machine operator, by grasping the'handle 19, pulls the printing frame 15 back toward its horizontal position. As the frame approaches the horizontal, the roller 72 strikes the corner of the rear latch 9G by reason of the interference or overlap indicated at d (FIG. 8), raising the latch 90. Since the latch is thus moved out of obstructing position with respect to the roller 72, the clamping bar 40 moves rearwardly under the urging of the biasing spring so that the roller becomes supported on the horizontal locking member 70 locking the printing frame in horizontal position. Simultaneously the switch 36, engaged by the upward movement of the latch 90, turns off the motor of the vacuum pump and releases the vacuum. With the clamping plate 50 and the vacuum both released, the glass cover 17, is free to move upwardly under the influence of the bias provided by the springs 100. The operator continues the opening movement of the cover sufficient to remove the positive and exposed plate, This restores the mechanism to the condition illustrated iii FIG. 2 and completes a single operating cycle.

The function of the operator is thus reduced to the simple and natural movements of unloading, reloading, lowering the cover and clamping followed by upward swinging movement of the frame into vertical position. The above mechanism insures that all of the steps required in theexposure of a platewill be carried out in a precisely predetermined order-without reliance upon the operators timing or judgment. This precludes the possibility that an operator may spoil a plate-by performing some function out of step as, for example, failing to manually turn on the vacuum While the frame is still in its substantially horizontal position. Moreover, those motions which are required of an operator may be accomplished with light operating forces so that the operator may run the machine over an entire work shift, unloading and reloading repeatedly on a production basis without fatigue. Movement of the cover and movement of the printing frame as a whole are both accomplished by using a single handle 19 on a cover. Since means are provided for locking the baseportion of the frame in horizontal position, upward movement of the handle during the loading cycle will have no effect upon the base portion. Conversely, with the cover clamped in place and the base portion released by its lock, upward movement of the handle produces bodily swinging of the frame. The operators efforts may be concentrated upon registering the plate and positive and in either controlling, or overseeing, the exposure.

Moreover, the arrangement described above isfound to be safe and without risk either to the machine or the operator. Thus the arrangement is to be contrasted with prior devices in which it is possible for the operator to swing the frame upwardly without clamping and without application of vacuum giving rise to the possibility that the cover may suddenly swing free by reason of the biasing or counterbalancing force with resultant impact between the glass cover and the upper portion of the supporting structure, possibly resulting in breakage. I

In spite of the various interlocked functions performed by the present mechanism, the'mechanism is inherently simple and. inexpensive, adding little to the cost of the total machine.

In the following claims the Words horizontal and vertical are to be' interpreted as "generally horizontal and generally vertical? The term glass refers to any transparent sheet material.

I claim as my invention:

1. In a vacuum printing frame apparatus the combination comprising a, pair of spaced supports,- a printing frame having a base portion and having a glass cover hinged at the rear edge thereof, means for central]? supporting the base portion on the supports for tilting between a horizontal loading position and a vertical exposing position, stops on the supporting structure for defining said positions, clamps at the forward edge of the base portion for clamping the glass cover into a seated vacuum-retaining position, clamping bars mounted for endwise shifting movement along respective sides of the base portion for operating, the clamps, a manual operator accessible at: the front edge of the base portion for simultaneous shifting of the bars, means for latching the bars in clamping position and for maintaining them in clamping position as the frame is tilted toward its vertical exposing position, and means responsive to restoration of the frame to horizontal position for releasing the latching means 2. In a vacuum printing, frame apparatus the combination comprisingv supporting structure including a pair of spaced supports, a printing frame having a base portion and a glass cover hinged at the rear edge thereof, a connection for applying vacuum above the base portion for urging a plate into seated engagement with the glass cover when the cover is closed, means for centrally supporting the base portion on the supports for tilting of the frame between a horizontal loading position and a vertical exposing position, stops on the supporting structure. for defining said positions, a clamp for clamping the glass cover to the baseportion, means for locking the frame in its horizontal position, a manual operator for closing the clampand releasing the lock, means responsive to closing of the clamp for applying vacuum to the connection, means for biasing the cover into its open position relative to the base portion, and means responsive to restoration of the frame to its horizontal position for simultaneously releasing the vacuum and releasing the lock so that the cover begins to open automatically upon restoration of the printing frame to horizontal position,

3. In a vacuum printing frame apparatus the combination comprising supporting structure including a pair of spaced supports, a printing frame having a base portion and a glass. cover hinged at the rearedge thereof, means for centrally supporting the base plate on the supports for tilting the frame between a horizontal loading position and a vertical exposing position, clamps at the forward corners of the base portion for clamping the cover, clamping bars mounted for endwise sliding movement along the sides of the base portion and coupled to the clamps at their respective forward ends for clamping the cover when the bars are in a first limit position, means forming a locking surface on the frame adjacent the rear end of the bars when the frame is in its horizontal position for blockingly engaging the rear ends of the bars and for locking the frame in horizontal position when the bars are in their opposite limit positions thus insuring that the clamps are clamped before the frame is swung from its horizontal position. v

4. -In a vacuum printing frame apparatus the combination comprising supporting structure including a pair of spaced supports, a printing frame having a base portion and a glass cover hinged at the rear edge thereof for sealthe base portion for clamping the cover, clamping bars mounted along the sides of the base portion for endwise sliding movement between first and second limit positions, said bars being coupled to the clamps at their respective forward ends for clamping the cover when the bars are in their first limit positions, means forming a locking surface on the frame adjacent the rear end of the bars when the frame is in its horizontal position for blockingly engaging the rear ends of the bars and for locking the frame in horizontal position when the bars are in their second limit positions, and means actuated upon moving the bars into their first limit positions for evacuating the frame.

5, In a vacuum printing frame apparatus the combination comprising supporting structure including a pair of spaced supports, a printing frame having a base portion and a glass cover hinged at the rear edge thereof, means for centrally supporting the base portion on the supports for tilting between a horizontal loading position and a vertical exposing position, stops on the supporting structure for defining said positions, clamping means for the cover at the forward edge of the base portion, means including a clamp operating member accessible for manual operation at the front of the frame for moving the clamping means into clamping position, means including a latch for maintaining the clamping means clamped up during the time that the frame is tilted. toward the vertical exposing position, and means responsive to the return of the frame to its horizontal position for releasing the latch for automatic release of the clamping means.

6. In a vacuum printing frame apparatus the combination comprising a supporting structure including a pair of spaced supports, a printing frame having a base portion and a glass coverhinged at the rear edge thereof, means for centrally supporting the base portion on the supports for tilting the frame between a horizontal loading position and a vertical exposing position, stops on the supporting structure for defining said positions, clamping means at the front edge of the base portion for clamping the glass cover to the base, clamp operating means including a manual control lever at the front of the base portion for operating the clamping means, said clamp operating means having a latch for retaining the same in a clamping position, means for tripping the latch automatically incident to restoring the printing frame to its horizontal position, and biasing means for urging the clamp operating means into a non-clamping position so that the glass cover is unclamped automatically upon tripping of the latch.

7. In a vacuum printing frame apparatus the combination comprising a supporting structure including a pair of spaced supports, a printing frame having aebase portion and a glass cover hinged at the rear edge thereof, means for centrally supporting the base portion on the supports for tilting the frame between -a horizontal loading position and a vertical exposing position, stops on the supporting structure for defining said positions, clamping means at the front edge of the base portion for clamping the glass cover thereto, clamp operating means coupled to the clamping means and having a manual operating handle, means for keeping the clamping means engaged during the time that the printing frame is tilted toward the vertical exposing position,

, means responsive to return of the frame to horizontal position for releasing the clamping means, and means for biasing the glass cover toward the open position so that the cover opens automatically upon restoring the frame to its horizontal position.

8. In a vacuum printing frame apparatus the combination comprising a supporting structure including a pair of spaced supports, a printing frame having a base portion and a glass cover hinged at the rear edge thereof, means for cent-rally supporting the base portion on the supports for tilting the frame between a horizontal loading position and a vertical exposing position, stops on the supporting structure for defining said positions, a clamp at the front edge of the base portion for clamping the cover, locking means for holding the frame horizontal, manual means for simultaneously closing the clamp and releasing the locking means so that the frame may be tilted away from its horizontal position, and means responsive to return of the frame to horizontal position for simultaneously releasing the clamp and resetting the locking means, said glass cover being biased into open position for opening when the clamp is released.

9. In a vacuum printing apparatus the combination comprising supporting structure including a pair of spaced supports, a printing frame having a base portion and a glass cover hinged at the rear edge thereof, means for centrally supporting the base portion on the support for tilting the frame between a horizontal loading position and a vertical exposing position, stops on the supporting structure for defining said positions, a clamp at the forward edge of the base portion for clamping the cover thereto, means including a lock for holding the frame in the horizontal position, manual means for simultaneously closing the clamp and releasing the look so that the frame may be tilted from the horizontal position, and means actuated upon release of the lock for applying vacuum within the printing frame at a rate of evacuation which is sufficiently great so as to insure clamping of the plate with respect to the glass cover by the time that the frame may be swung substantially from its horizontal.

10. In a vacuum printing frame apparatus the combination comprising supporting structure including a pair of spaced supports, a printing frame having a base portion and a glass cover hinged at the rear edge thereof, a connection for applying vacuum above the base portion for urging a plate into seated engagement with the glass cover when the cover is closed, means for centrally supporting the base portion on the supports for tilting the frame between a horizontal loading position and a vertical exposing position, stops on the supporting structure for defining said positions, a clamp for clamping the glass cover to the base portion, means including a lock for holding the frame in its horizontal position, a manual operator for closing the clamp and releasing the lock, means for disabling the manual operator until the glass cover is closed, means operated incident to closing of the clamp for applying vacuum to the connection, means for preventing opening of the clamp while the frame is swung from horizontal to vertical position and back again, means for biasing the cover into its open position, and means responsive to restoration of the frame to its horizontal position for simultaneously releasing the vacuum and releasing the clamp so that the cover may be opened upon restoration of the printing frame to horizontal position.

11. In a vacuum printing frame apparatus the com bination comprising a supporting structure including a pair of spaced supports, a printing frame having a base portion and a glass cover hinged at the rear edge thereof, means for centrally supporting the base portion on the supports for tilting of the frame between a horizontal loading position and a vertical exposing position, stops on the supporting structure for defining said positions, clamping means at the front edge of the base portion for clamping the glass cover thereto, a handle on the glass cover, means for keeping the clamping means engaged during the time that the printing frame is tilted toward the vertical expo-sing position by upward force on the handle, and means responsive to return of the frame to horizontal position for releasing the clamping means so that upward force on the handle causes the cover to separate from the base portion.

12. In a printing frame apparatus the combination comprising a supporting frame including a pair of spaced supports, a printing frame having a horizontal hinge connection adjacent the center thereof for tilting between a horizontal loading position and a vertical exposing position, said printing frame consisting of a base portion and a glass cover substantially coextensive therewith, a second horizontal hinge connection along the rear edge of the cover for hinging the same to the rear edge of the base portion, clamping means for securing the cover to the base, and biasing means connected to the center portion of the glass cover and reactively connected to the supporting frame for applying an upward biasing force to the center portion of the glass cover for biasing the cover upwardly about the second hinge connection when the cover is free of the base while applying only limited bias to the frame as a whole about the first hinge connection.

13. A printing frame apparatus as claimed in claim 12 in which the means for applying biasing force to the cover is in the form of a lever having a pivot fixedly positioned with respect to the supports together with a biasing spring for biasing the lever.

References Cited UNITED STATES PATENTS 7/1955 Padgett 76 8/1966 Benson 95--76

Claims (1)

1. IN A VACUUM PRINTING FRAME APPARATUS THE COMBINATION COMPRISING A PAIR OF SPACES SUPPORTS, A PRINTING FRAME HAVING A BASE PORTIONF AND HAVING A GLASS COVER HINGED AT THE REAR EDGE THEREOF, MEANS FOR CENTRALLY SUPPORTING THE BASE PORTION OF THE SUPPORTS FOR TILTING BETWEEN A HORIZONTAL LOADING POSITION AND A VERTICAL EXPOSING POSITION, STOPS ON THE SUPPORTING STRUCTURE FOR DEFINING SAID POSITIONS, CLAMPS AT THE FORWARD EDGE OF THE BASE PORTION FOR CLAMPING THE GLASS COVER INTO A SEATED VACUUM-RETAINING CLAMPING BARS MOUNTED FOR ENDWISE SHIFTING MOVEMENT ALONG RESPECTIVE SIDES OF THE BASE PORTION FOR OPERATING THE CLAMPS, A MANUAL OPERATOR ACCESSIBLE AT THE FRONT EDGE OF THE BASE PORTION FOR SIMULTANEOUS SHIFTING OF THE BARS, MEANS FOR LATCHING THE

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