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Publication numberUS3859917 A
Publication typeGrant
Publication dateJan 14, 1975
Filing dateOct 24, 1972
Priority dateOct 24, 1972
Also published asCA1006046A1
Publication numberUS 3859917 A, US 3859917A, US-A-3859917, US3859917 A, US3859917A
InventorsBubley Henry J, Oltra Claude H
Original AssigneeAmerican Screen Printing
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Screen printing press
US 3859917 A
Abstract
An improved screen printing press having a first frame with a surface to receive work for printing and a second frame pivotally mounted on the first frame and having a pair of spaced-apart support arms for movement therewith toward and away from the surface, a chase pivotally mounted on the first frame beneath the arms, and movable therewith, a screen removably mounted on the chase, a carriage assembly means, with a squeegee and a flood bar, mounted for reciprocal movement on the arms, the second frame also having, at a rear portion thereof, a press drive means operatively connected to drive arms mounted for pivotal movement on the first frame to drive the carriage assembly means. The second frame pivots with respect to the first frame about an axis in the plane of the work surface to eliminate smearing during the movement of the second frame. A timed relationship exists between the upward pivotal movement of the second frame and the pivotal movement of the drive arms such that linear movement of the carriage assembly means is momentarily suspended at the end of the printing stroke to eliminate ink drip and splatter. Shuttle means in the carriage assembly means engages stops at opposite ends of the support arms to shift the squeegee and the flood bar relative to one another by a novel parallelogram movement.
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Description  (OCR text may contain errors)

United States Patent 1191 Bubley et al.

[ 1 Jan. 14, 1975 SCREEN PRINTING PRESS [75] Inventors: Henry J. Bubley, Deerfield; Claude H. Oltra, Chicago, both of I11.

[73] Assignee: American Screen Printing Equipment Company, Chicago, Ill.

[22] Filed: Oct. 24, 1972 [21] Appl. No.: 299,689

Primary ExaminerRobert E. Bagwill Assistant ExaminerR. E. Suter Attorney, Agent, or Firm-Robert E. Wagner, Robert E. Brown; Stone, Wagner & Aubel [57] ABSTRACT An improved screen printing press having a first frame with a surface to receive work for printing and a second frame pivotally mounted on the first frame and having a pair of spaced-apart support arms for movement therewith toward and away from the surface, a chase pivotally mounted on the first frame beneath the arms, and movable therewith, a screen removably mounted on the chase, a carriage assembly means, with a squeegee and a flood bar, mounted for recipro- References Cited cal movement on the arms, the second frame also hav- UNITED STATES PATENTS ing, at a rear portion thereof, a press drive means op 1,821,302 9/1931 Gomer 101/126 eratively Connected to drive arms mounted for Pivotal 1,840,073 1/1932 Williams 101/123 movement on the first frame to drive the Carriage 1,898,406 2/1933 Tate et al.... 101/123 sembly means. The second frame pivots with respect ,989 10/1935 Wulf 101/126 to the first frame about an axis in the plane of the 2,704,510 3/1955 Walsh 101/123 work surface to eliminate smearing during the move- 2,709,404 5/1955 Stokes 101/12 ment of the second frame. A timed relationship exists I i u between the upward pivotal movement of the second 2936705 5,1960 Z? esmanm W123 frame and the pivotal movement of the drive arms 2963964 12/1960 X such that linear movement of the carriage assembly 219751705 3/1961 Gilman 101/123 means is momentarily Suspended at the end of the 2,991,711 7/1961 Ehrhard 61 a1 101/126 P g stroke to eliminate ink p and Splattee Shut- 3,605,614 9/1971 Gilman etal...... 101/126 tle means in the carriage assembly means engages 3,731,623 5/1973 Bubley et. a1 101/123 X stops at opposite ends of the support arms to shift the FOREIGN PATENTS OR APPLICATIONS squeegee and the flood bar relative to one another by 702 29s 3/1966 Italy 101/123 3 novel parallelogram movement 17 Claims, 11 Drawing Figures PATENIEB JAN 1 4 I875 SHEEI 10F 3 SCREEN PRINTING PRESS BACKGROUND OF THE INVENTION This invention relates to screen printing apparatus in general and, more specifically, to a new and improved stencil screen printing press designed to eliminate smearing of work and permit easy scaling of the size of the press.

In known types of stencil screen printing apparatus, the printing head, including the screen frame, is raised and lowered to permit insertion and removal of the stock to be printed. In most previous printing apparatus, this printing head is mounted on a fixed frame containing'a bed and press drive means, and is raised and lowered with respect to the bed and fixed frame on a pivot point above the bed. An advanced and novel form of press of this type is sold by American Screen Printing Equipment Company of Chicago, Ill. and is the subject of U.S. Ser. No. 83,800, filed Oct. 26, 1970, and titled Glider Press, now U.S. Pat. No. 3,731,623, issued May 8, 1973. Though this press contains many unique and desirable features, the printing head, when moved upwardly with respect to the surface of the printing bed at the end of a print stroke, tends to move a rear portion of the screen into contact with the printed work, because of the placement of the pivot point, thereby smearing the work.

This smearing problem was attempted to be solved by the prior art by pivoting the entire printing head and press drive means portion of the printing press with respect to the fixed printing bed.

While it is believed that such construction will tend to eliminate the smearing problem, the structure he teaches has several disadvantages. The pivot point in is disposed at the rearmost portion of the base, which places an inordinate amount of weight forward of the pivot point. This weight produces excessive stresses and wear on the power means and cam drive means, and instability and possible undesirable movement and vibration of the frame.

The prior art also mounts the driving arm, which drives the squeegee and flood bar assembly A, inside the support arms, on the pivoting frame itself. Since the assembly A is therefore movable with respect to a moving frame rather than a fixed frame or reference point, its movement and registration are adversely affected by any instability or movement of the movable frame. Because of these problems, it has been impossible to engineer and construct large size printing presses according to Fuchs by merely scaling the size of the movable frame. The excessive weight and instability encountered have precluded proportioning elements such as the drive arms necessary to scale the prior art to larger sizes. Finally, the prior art teaches pivoting the entire master frame about the rear pivot point located slightly above the horizontal plane of the screen, necessitating accurate re-registration of the entire frame and screen, with respect to the printing surface, each time the printing head moves downward.

DESCRIPTION OF THE INVENTION This invention provides an improved screen printing press containing many features of U.S. Ser. No. 83,800, now U.S. Pat. No. 3,731,623, mentioned above, while eliminating the problems of smearing and splattering at the end of the printing cycle and permitting scaling to any desirable size of press unit. U.S. Pat. No. 3,731,623

was issued May 8, 1973 and assigned to American Screen Process Equipment Company, which is, by change of name, the same entity as the assignee of the present application. U.S. Pat. No. 3,731,623 is expressly incorporatd in its entirety herein by reference thereto.

This improved screen printing press overcomes the disadvantages of present presses by a first fixed frame and a second frame pivotal on pivot points disposed on the first frame in the horizontal planeof the surface of the printing bed of the fixed frame, and in a vertical plane forward of the press drive means. The second frame supports the printing head, including the support arms, the carriage assembly means having the squeegee and flood bar, a chase and a screen frame mounted thereon, and, to the rear of the pivot points, a press drive means.

The location of the pivot point in the horizontal plane of the printing surface allows movement of the printing head toward and away from the printing surface with out smearing of the work since the chase and screen will not move downwardly toward that surface when they are pivoted relative to the first frame with the printing head.

Another advantage of the present invention is that the drive arm means connecting the press drive means and the carriage assembly means are mounted on the first fixed frame and outside of the carriage assembly support arms. Such mounting assures steady and uniform movement of the carriage assembly means by the drive arms since they are mounted on a fixed reference point rather than a movable frame. It also allows support of the significant weight of the massive drive arms necessary for very large presses on the rigid first fixed frame rather than the movable second frame. This feature, together with the location of the pivot points on the first frame to permit a proper, balanceddistribution of the weight of the components mounted on the second frame on either side of the pivot point, allows sca ling of this press to any desired size by eliminating the stresses, excessive power demands and inordinate weight which precluded proportioning previous presses to larger sizes.

The novel relocation of the pivot point and the disposition of the arms driving the carriage assembly means, did, unfortunately create a major problem. Near the end of the printing stroke, the printing head begins to pivot with the second frame to an upward position off the press to allow removal of the printed work. At this point, the carriage assembly means would tend to creep and shake on the support arms, splattering ink on the printed work. This problem has been successfully overcome in the present invention, however, by a novel timed relationship between the movement of the printing head and the drive arms. To achieve this relationship, the press lift cam is so formed that, while it is being rotated by the press drive means against a cam follower fixedly mounted on the first frame to move the printing head rapdily upward, the connecting means driving the drive arm means, and being rotated at the same speed of rotation by the same press drive means, will reach a point of linear alignment in which, through a few degrees of rotation by the press drive means, the slight relative movement of the connecting means causes only sufficient movement of the drive arm means to eliminate forward creep of the carriage assembly means. This programmed movement of the ward position, by itsconnection to the rigid drive arms,

for the brief period between the end of the print stroke and the full upward movement of the head. This completely eliminates any shaking of the carriage assembly means andthe resulting spilling of ink.

The carriage assembly means itself has a novel parallelogram movement which acts to shift the flood bar and squeegee bar relative to one another while maintaining them in balanced, locked-in relationship.

The chase or master frame of this invention is independently pivotally mounted on a horizontal axis defined by the pivot points to permit the use of either the harmonic peeling means set forth in detail in U.S. Ser. No. 83,800 now U.S. Pat. No. 3,731,623 or a uniform rate of peel with this form of press so that off-contact printing resulting in high-fidelity prints is possible. The mounting of the chase in such a manner also permits accurate re-registration of the screen frame with respect to the printing surface, since the chase will always remain registered in the plane of the surface at its pivot point.

Accordingly, it is an object of this invention to provide an improved screen printing press which eliminates smearing of the work located on the printing surface and which can be easily scaled to any desired size.

It is a further object of this invention to provide an improved, screen printing press having drive arms mounted on a first fixed frame and driven by a press drive mounted on a second frame pivotal on the first frame about an axis in the plane of the printing surface, the movement of the second frame and the press drive arms being in a timed relationship effective to control movement of the drive arms for a desired period of time at the end of a print stroke, while the second frame is pivoted away from the printing bed, to eliminate smearing and splattering of work.

It is still another object of this invention to provide an improved screen printing press in which the chase is independently pivotal about an axis between the pivot points of the second frame on the first frame, to insure accurate re-registration of the chase with respect to the printing surfact.

It is also an object of this invention to provide an improved screen printing press having a squeegee and flood bar mounted in balanced, locked-in relationship on a carriage assembly and shifted with respect to one another by a parallelogram movement.

These and other objects of this invention will become evident from the following description of the drawings, illustrating a preferred embodiment wherein:

' FIG. 1 is a perspective view of the improved printing press of this invention shown with the printing head in its upward position near the end of a printing cycle;

, FIG. 2 is an enlarged, fragmentary side elevational view of the printing press shown in FIG. 1 with the screen in printing'position;

FIGS. 3-7 are reduced side elevational views of the printing press shown in FIG. 1 which illustrate the operation of the press and the timed relation between the movement of the second frame and the carriage assem- FIG. 8 is an end elevational view of the rear portion of the second frame including the power drive means, the cam, cam follower and springs;

FIG. 9 is an enlarged fragmentary side elevational view of a carriage assembly positioned adjacent the forward stop means in the position assumed during the print stroke;

FIG. 10 is an enlarged fragmentary side elevational view of the carriage assembly shown in FIG. 9 in the position assumed during the flood stroke; and,

FIG. 11 is a fragmentary side elevational view of the carriage assembly shown in FIG. 10 converted to nonflood scoop position.

Referring now to the drawings, and in particular, to FIG. 1, the improved screen printingpress of the present invention is shown generally at 10. This press 10 includes a first fixed frame '12 having a control console 15 located at its front which permits an operator to control the operation of the press. The first frame 12 has a printing bed 16 located at its top which is preferably a vacuum base of the type described in now abandoned application U.S. Ser. No. 674,623, filed Oct. 1 1, 1967 and titled Vacuum Base. A vacuumto the printing surface 17 of bed 16 is supplied through a flexible conduit 19 joined to a vacuum source 18, which is supported on the frame 12. The air flow through the conduit 19 may be reversed to provide a blow-black release of the stock being printed, which'is particularly advantageous in releasing heavy stocks.

This screen printing press 10 also has a second frame 14 which is pivotally mounted on first frame 12 at a pivot point 13. The second frame 14 is pivotally movable with respect to the first frame 12 on a horizontal pivot shaft 23 extending between similar pivot points 13 disposed on opposite sides of the first frame 12 and located in approximately the samehorizontal plane as printing surface 17. Second framel4 has, at its front portion, a screen printing head, indicated generally at 20, which includes a pair of parallel spaced support arms 21 and 21' having a carriage assembly means, generally indicated at 22, mounted for movement therealong.

The carriage assembly means 22 includes a carriage assembly 24 and 24' disposed on each of the support arms 21 and 21', respectively. The carriage assemblies 24 and 24 are of identical, but reverse construction, one being a mirror image of the other. They are linked together for unitary movement by a pair of joining rods 30 extending between them.

A master frame or chase 37 is disposed below support arms 21 and 21' and is mounted for independent pivotal movement about pivot shaft 23 on a spherical bearing 39 and a bracket 36 disposed on opposite sides of frame 12, as shown in FIG. 2. The master frame 37 is movably attachable, at its front end, to the midportion of a lateral brace 64 joined to vertical braces 65 and 65' which extend downwardly from support arms 21 and 21' to assure rigidity of the chase 37. While this mounting enables the chase 37 to be raised with the printing head 20 during the printing cycle, it also permits the chase 37 to be lowered independently of the head 20, for purposes of changing the stencil screen 38, by detaching its forward end from the lateral brace 64. Since the rear portion of the chase 37 will always, in this manner, be returned to its previous position in the plane of the surface 17 of printing bed 16,

the problem of accurately re-registering the entire master frame upon changing of the screen is eliminated.

The stencil screen, 38 is held in the chase 37 by clamps 68, or the equivalent, acting against its frame, which are chosen to facilitate replacement of the screen. The entire printing head may be locked in to front lock stops 90 and 90 during printing by bearings on braces 65 and 65 to assure proper screen position.

The press drive means is mounted on a rearward portion of second frame 14 and is generally indicated at 40 in FIG. 1 and shown in more detail in FIG. 8. It includes a motor 41 mounted on a movable motor support 42 having a threaded shaft 43 cooperating with threads on the support to permit adjustment of the motor relative to the second frame 14. A variable speed drive pulley 44 is mounted on motor 41 and, through a belt 45, drives a pulley 46 mounted on an inputshaft 47 of a reduction gear arrangement 48. The reduction arrangement 48 is of a known type having an output shaft 49 disposed at right angles to input shaft 47 and extending from its opposite sides. Output shaft 49 is rotated to drive a press lift cam 51 disposed on one side of gear arrangement 48 and a main drive lever arm 50 disposed on the opposite side. A number of mechanically operated switches and linkages 52 are coordinated and activated with the operation of the press to perform various functions in the printing cycle, e.g., energizing the vacuum bed and applying the blow-back. A take-off apparatus may be energized and synchronized with the press by a microswitch mounted on the press. Clearly, additional switches could be provided for other accessories and the activation of various functions could be accomplished by alternative means such as electrical timers and switches and control cams.

The main drive lever arm 50 is connected, through a second arm 54, to L-shaped arm 55 which has its opposite end fixedly mounted on a rotatable shaft 56 extending through bearings on the first frame 12 and joined, at its opposite ends, to identical drive arms 59 and 59', as shown in FIG. 8.

The drive arms 59 and 59 which are mounted on the first frame 12 through shaft 56, are generally L-shaped and connected at their opposite ends through drive rods 60 and 60 to carriage assemblies 24 and 24', respectively. As thedrive arms 59 and 59 are pivoted on frame 12 with shaft 56 by press drive 40, they act to drive carriage assemblies 24 and 24' in forward and return strokes across bed 16 on arms 21 and 21. The length of stroke made by the drive arms and carriage assemblies is variable by adjusting the position of second arm 54 in an arcuate slot 57 formed in L-shaped arm 55, since shaft 56 and pivoting shaft 23 are always maintained in vertical alignment and generally form a triangle with output shaft 49.

The design of the press drive means 40 permits it to be located within the sides of the bed 17 and chase 37. As mentioned above, the mounting of the heavy drive arms 59 and 59 on the first frame 12 permits the size of the press to be proportionately increased without adversely increasing the weight of the second frame 14. Bed '17 is also unobstructed by drive arms 59 and 59' during the printing cycle, which permits mechanical feeds, conveyors and the like to be used with the press, or the press to be used as an element in a printing system. Where mechanical-type takeoffs having mechanical fingers for removing printed stock from the press bed 17 are used, it has been found desirable to form cut-out areas in bed 17 along the edge of the press adjacent the takeoff to permit the fingers to better grip the stock on the bed.

As shown in FIGS. 2 and 8, the press lift cam 51 is positioned so that its perimeter is constantly in cooperation with a cam follower 62 mounted on frame 12 through a rigid cam follower arm 63. As cam 51 is rotated on shaft 49 toward its high side, the second frame 14 is pivoted with respect to the first frame 12 about pivot points 13 on pivot axis 23, to move the printing head 20 upwardly away from the printing bed 16 and the rear portion downwardly.

A carriage assembly 24 is described in more detail in FIGS. 9 and 10. This assembly is of identical, but reverse construction to carriage assembly 24 mounted on the opposite support arm 21. Carriage assembly 24 has a housing 25 mounted on arm 21 and connected at its rearward end by a pivotal connection 27 to drive rod 60 and drive arm 59. Nylon guides (not shown) are provided within the housing 25 to assure smooth and friction-free movement of the carriage assembly 24' along the arm 21, during the printing cycle. The housing 25 contains a shuttle 26 captive between its inside surface and the outside surface of arm 21. The shuttle 26 is provided with a continuous cam track 31, which functions to shfit a flood bar and a squeegee in a generally vertical movement relative to one another. The shuttle 26 itself is linearly moved with respect to housing 25 upon engaging stops 72 and 74 disposed at opposite ends of arm 21.

A shuttle catch 75 is pivotally mounted on housing 25 to engage shuttle 26 and prevent its movement during the flood traverse. The catch is disengaged when the shuttle hits stop 72. A movable parallelogram support 32 is disposed on the outside of housing 25 with the top and bottom members of the parallelogram pivotally mounted thereon through bearing bolts 29. The opposite side members of the parallelogram 32 are pivotally connected to the top and bottom sides of the parallelogram 32 to move in vertically opposite directions. One side member supports a squeegee assembly 33 and the other a flood bar assembly 35. A cam follower roller 28 is captively disposed to ride in cam track 31, and is attached through the vertical squeegee support member of the parallelogram to the squeegee assembly 33. This roller 28 functions to move the parallelogram 32 in pivotal movement about the bearing bolts 29 in response to linear movement of the shuttle 26 at the end of each stroke. Thus, direct movement of the squeegee 33 with the roller 28 causes corresponding opposite vertical movement of the flood bar 35, providing a system in which the squeegee and flood bar are positively locked in a constant relationship for corresponding movement.

At the end of the flood or return stroke, the stop 72 engages the facing end of shuttle 26 while the carriage housing 25 continues its transverse movement, thereby causing the cam follower roller 28 to be moved in the cam track 31, shifting the parallelogram 32 and Iowering the squeegee 33, as shown in FIG. 9. At the opposite or rearward end of support arm 21, the stop 74 engages the shuttle and shifts it in a similar manner to reverse the positions of the squeegee and flood bar, for the return stroke, as shown in FIG. 10. In printing fabrics and the like, the flood bar and the flood bar assembly 35 may be replaced with a second squeegee to permit printing in both directions. In such event, the cam 51 will be timed to lower the press head 20 before forward movement of the carriage assembly 40 is commenced.

Conversion of the press from'flood to non-flood condition can be rapidly accomplished with little effort, by release of the flood bar clamp 34, substitution of a nonflood scoop 80,and adjustment of the flood bar assembly 35 by movement of shoulder screw 81 rearward and removal of shoulder screw 82. Push arm 84 is then mounted on the rear of shuttle 26 to'loca'te the nonflood scoop to cooperate with the squeegee on the return stroke. The simplicity of the mechanism assures proper non-flood and flood function at all times, since the parallelogram movement shifting the flood and squeegee assemblies is automatically actuated by the shuttle at every change in direction of the press. With the chase 37 in down position and the press head 20 elevated, the squeegee and the flood bar can be easily removed and cleaned or replaced.

The operation of the press is shown in FIGS. 1-7.

,When the press is in the condition shown in FIG. 1, the

stock to be printedmay be placed on the surface 17 of bed 16. The motor 41 is then actuated through the central console causing the shaft to rotate and the carriage assemblies 24 and 24' to be driven by the drive arms 59 and 59' to the front of the press, as shown in FIG. 2. The condition of each carriage assembly during the forward or non-print stroke is shown in FIG. 10 for the flood type operation. If a non-flood scoop is used, the position of the flood and squeegee assemblies would be as shown in FIG. 11. In either operation, the ink' pool is moved to the front of the screen by this stroke.

When the carriage ass e'mbly'means 22 reaches the end of the support arms at the front of the press, the shuttles 26 and 26' are engaged by stops 72 and 72' lowering the squeegee assemblies and elevating the flood bar assemblies, as shown in-FIG. 3. At this point, as output shaft 49 continues its rotation, the direction of the drive arms 59 and 59 is reversed. This occurs just as press lift cam 51 reaches its low side or smallest radius so that the printing head is adjacent the printing surface 17. The drive arms 59 and 59"continue to rotate with shaft 56 in a rearward direction to pull the squeegee across the stencil screen 38. In off-contact printing, as shaft 56 moves, a peeling mechanism, which will be explained below, functions to elevate the screen 38 behind the squeegee. In on-contact printing, no elevation of the screen is experienced.

FIG. 4 shows the press at approximately the midpoint of the print stroke, using the contact method in which the screen remains in place. When drive arms 59 and 59' reach the rear position, shown in FIG. 5, the print stroke is complete. The carriage assemblies 24 and 24' have engaged stops 74 and 74 near the rearof the respective press arms 21 and 21', causing the flood bar to be lowered and the squeegee head to be elevated. At this point in time, the press lift cam 51 is approaching its high side, causing the second frame 14 to be pivoted about horizontal axis 23, thereby moving the printing head 20 away from the printing bed 16.

FIGS. 5 and 6 clearly show the novel, timed relationship between the movement of the second frame 14 and the movementof the drive arms 59 and 59' and associated carriage assembly means 22. As shown in these figures, the second frame 14 continues to be pivoted and the printing head 20 raised to its uppermost position, while the drive arms are backedoff slightly to hold carriage assembly means 22 in a position adjacent stops 74 and 74' thereby preventing forward creep along the press arms. While cam 51 moves to its greatest radius, main drive lever arm 50 and the second arm 54 move through an arc which imparts only sufficient rearward linear movement to the drive arms 59 and 59 to constantly maintain carriage assembly means 22 adjacent the rear of the press arms during the continuing upward movement of the printing head. Since carriage assembly means 22 is therefore held firmly adjacent stops 74 and 74' by this slight, but constant backing off force of the drive arms exactly corresponding to the movement of the printing head and theforward force exerted by the press arms on the carriage assembly means, shaking or vibration and splattering of ink is eliminated. It is also significant that because of the lo cation of pivot point 13, the rear portion of screen 38 never swings in an are that will bring it in contact with the surface 17 of the printing bed 16. The entire press may also be caused to dwell or stop in the condition shown in FIG. 6 to enable the removal of printed stock and the insertion of unprinted stock.

As shaft 49 continues to rotate cam 51 and lever arm 50, the second frame 14 begins to pivot toward the printing surface 17, and lever arm 50 and second arm 54 reach a point in their arc where their movement initiates forward movement of the drive arms 59 and 59' and the carriage assembly means 22, as shown in FIG. 7. The second frame 14 is also being constantly urged to a horizontal position with respect to the printing bed 16 of the first frame 12 by spring means 58 and 58' which have one end connected by a turnbuckle to a rear portion of the second frame l4 and an opposite end connected to a supporting brace on the first fixed frame 12.

In many types of screen printing, particularly when using a screen material that has appreciable stretch, it is desirable to use off-contact printing. This type of printing is achieved by lifting or peeling the stencil screen behind the squeegee as the squeegee is moved along the support arms in the print stroke. This peeling of the stencil screen may be accomplished, in the present invention, by a peeling mechanism which is not shown herein but which is similar to that described in US. Ser. No. 83.800, filed Oct. 26, I970 and titled Glider Press now US. Pat. No. 3,731,623, which is incorporated in its entirety herein by reference thereto. The peeling mechanism disclosed in that application may be mounted on the present press so that the rate of peeling follows a harmonic motion pattern in that peeling is faster as the squeegee moves across the center of the screemthan at either end, thereby compensating for the greater tendency of the screen materials to stretch at that point. Peeling is accomplished by cables connected to the front of chase 37 and releasable therefrom to permit movement of the chase with respect to the printing head 20. These cables are each extended over pulleys and through a support arm 21 or 21' to pulleys positioned on shaft 56 for rotation therewith. As shaft 56 rotates in response to movement of L-shaped arm 55, a pulling force is exerted on the cables, lifting the chase in opposition to the downward pressure of the sequeegee assembly on the stencil screen. When metallic or other screen material having little appreciable stretch is used, off-contact printing may also be satisfactorily accomplished with this invention by use of a uniform rate of peeling means. An alternative form of peeling means linkage to that described above which may be used to perform either harmonic or uniform peeling is operated directly from a peeling cam being rotated by shaft 49. As the peeling cam rotates, it moves a lever arm pivotally mounted on the second frame 14. The disposition of the peeling cables is as described above except that one end of the cable is attached near the end of the lever arm opposite its pivot point. The point of attachment of the cable to the lever arm may be adjusted along the lever arm to vary the amount of peel. The rate of peel, from uniform to harmonic, can be adjusted by changing the shape of the cam as necessary.

The press of the present invention is of rugged design and constructed of standard, available materials, which makes it quite economical to manufacture. Moreover, the press is of universal design, permitting it to be scaled up or down to meet particular customer requirements. Upon consideration of the foregoing, it will become obvious to those skilled in the art that various modifications may be made without departing from the invention embodied herein. Therefore, only such limitations should be imposed as are indicated by the spirit and scope of the appended claims.

We claim:

1. A printing press, including fixed frame, a bed supported on said frame and having an upwardly facing surface to receive work to be printed, a second frame pivotally mounted on said first frame, a pair of spacedapart arms mounted on a front portion of said second frame for pivotal movement therewith toward and away from said bed, a chase pivotally mounted beneath said arms, said chase being positioned over said work on said bed during printing, a screen removably mounted on said chase, carriage assembly means mounted on said arms for movement therealong, a drive arm pivotally mounted on said first frame and connected to said carriage assembly means, press drive means mounted entirely on a rear portion of said second movable frame to move said carriage assembly means reciprocally along said arms during a printing cycle and to pivot said second movable frame relative to said first fixed frame during the printing cycle, means operatively connecting said press drive means mounted on said second frame to said drive arm means pivotally mounted on said first frame, said press drive means operatively engaging said first frame to pivotally move said second frame about a pivot point disposed generally in the horizontal plane of said surface of said bed adjacent a rear edge of said surface and allowing said rear portion of said second frame on which said press drive means is mounted to be swung below said horizontal plane of said surface of said bed during the printing cycle, such positioning of said pivot point thereby eliminating smearing of work placed on said bed, by preventing any portion of said screen from contacting said work to be printed during movement of said second frame during a printing cycle, said press drive means moving said second movable frame and said drive arm relative to one another during said printing cycle such that, for a desired period of time, the disposition of said means connecting said press drive means to said drive arm causes said carriage assembly means to be maintained adjacent a selected point along said arms during the upward movement of said second frame to thereby eliminate creep of said carriage assembly means along said arms and resulting dripping of ink.

2. The printing apparatus of claim 1 wherein said second frame is urged toward a horizontal position with respect to said first frame such that said screen and said bed lie in parallel planes, by resilient means joining said rear portion of said second frame to said first frame.

3. The printing press of claim 1 wherein said press drive means includes a power drive shaft rotatable about a central axis, said power drive shaft having a cam mounted for rotation therewith near one end thereof and linking means mounted'on an opposite end thereof and operatively connecting said press drive means with said drive arm to pivot said drive arm relative to said first frame, said cam engaging a cam follower mounted on said first frame to move said second frame about said pivot point, said cam and said linking means being moved by said power drive shaft driven by said press drive means, such that as the rotation of said cam causes said second frame to be pivoted upward with respect to said bed near the end of a printing stroke, further movement of said linking means will, through a desired period of time, cause sufficient backing movement of said drive arm and said connected carriage assembly to preclude forward creep of said carriage assembly along said spaced-apart arms during said upward movement of said second frame.

4. The printing press of claim 1 wherein said drive arm mounted on said first frame includes a pair of spaced drive arms mounted for corresponding pivotal movement with respect to said first frame on a drive shaft extending between them, each of said drive arms disposed outside of said arms supporting said carriage assembly.

5. The printing press of claim 1 wherein said chase is mounted on a horizontal axis defined by said pivot points on said first frame and is independently pivotal about said axis to allow peeling of said screen during the printing cycle, while always having a portion thereof maintained in proper registered relation to said bed to facilitate registration of said chase with respect to said bed and said first frame.

6. The printing press of claim 1 wherein said bed has a plurality of cut-out portions formed along one edge thereof to facilitate access to work positioned on said bed to allow its gripping, removal and transfer.

7. A printing press including a first fixed frame, a bed supported on said frame and having an upwardly facing surface to receive work to be printed, a second frame pivotally mounted on said first frame, a pair of spacedapart arms mounted on a front portion of said second frame for pivotal movement therewith toward and away from said bed, a chase pivotally mounted beneath said arms, said chase being positioned over said work on said bed during printing, a screen removably mounted on said chase, a carriage assembly mounted on said arms for movement therealong, a drive arm pivotally mounted on said first frame and connected to said carriage assembly, press drive means mounted on a rear portion of said second frame and operatively connected to said drive arm to drive said drive arm and thereby move said carriage assembly reciprocally along said arms, said press drive means including a power drive shaft rotatable about a central axis, said power drive shaft having a cam mounted for rotation therewith near one end thereof and linking means mounted on an opposite end thereof and operatively connecting said press drive means with said drive arm to pivot said drive arm relative to said first frame, said second frame being pivotally moved by said press drive means with respect to said first frame during a printing cycle about a pivot point disposed generally in the horizontal plane of said surface of said bed adjacent a rear edge of said surface and allowing saidrear portion of said second frame on which said press drive means is mounted to be swung below said horizontal plane of said surface of said bed during the printing cycle, said linking means including a press drive arm fixedly mounted on said power drive shaft for rotation therewith, a rod pivotally connected at one end to an outward end of said press drive arm and moved in generally reciprocal movement thereby, an L-shaped slot arm fixedly mounted near one end thereof on a shaft, said shaft pivotally mounted on said first frame and having said drive arm connected thereto, said slot arm being adjustably connected near its opposite end to said rod, said cam engaging a cam follower mounted on said first frame to move said second frame about said pivot point, said cam including a press lift cam having a varying radius, said cam and said linking means being moved by said power drive shaft driven by said press drive means to cause a related movement of said second frame and said drive arm sufficient to prevent creep of said carriage assembly on said arms while said second frame continues to pivot upward when said press drive arm sweeps through an arc bridging the lowest point on its circle of rotation whilesaid press lift cam engages said cam follower across the greatest radius of said cam.

8. A printing press, including a first fixed frame, a bed supported on said frame and having an upwardly facing surface to receive work to be printed, a second frame pivotally mounted on said first frame, a pair of spaced-apart arms mounted on a front portion of said second frame for pivotal movement therewith toward and away from said bed, a chase pivotally mounted be neath said arms, said chase being positioned over said work on said bed during printing, a screen removably mounted on said chase, a carriage assembly mounted on said arms for movement therealong, a drive arm pivotally mounted on said first frame and connected to said carriage assembly, press drive means mounted on a rear portion of said second frame and operatively connected to said drive arm to drive said drive arm and thereby move said carriage assembly reciprocally along said arms, said carriage assembly including a pair of spaced carriage housings, each housing supported on one-of said arms, means on each carriage housing for supporting a squeegee and a flood bar in associated relationship for movement relative to each other corresponding to the position of said screen over said bed, said squeegee being brought into contact with said screen when said screen is positioned over said work, and means for shifting said squeegee and said flood bar relative to each other to automatically and properly position the same during movement of said carriage housings on said arms, said second frame being pivotally moved by said press drive means with respect to said first frame during a printing cycle about a pivot point disposed generally in the horizontal plane of said surface of said bed adjacent a rear edge of said surface and allowing said rear portion of said second frame on which said press drive means is mounted to be swung below said horizontal plane of said surface of said bed during the printing cycle, such positioning of said pivot point thereby eliminating smearing of work placed on said bed, by preventing any portion of said screen from contacting said work to be printed during movement of said second frame during a printing cycle, the operative relationship between the pivotal movement of said second frame and the movement of said drive arm by said press drive means being such that said carriage housings are maintained at selected points along said arms with said cam track in said shuttle and stop means disposed near opposite ends of each of said arms to engage and reversibly" move said shuttle as said carriage assembly is moved adjacent each end of said arms, the movement of said shuttle by said stop means operating to pivot said means supporting said squeegee and flood bar to shift said squeegee and said flood bar in a generally vertical direction relative to each other.

9. In a printing press having a first fixed frame, a bed supported on said frame having an upwardly facing surface to receive work to be printed, a second frame mounted for pivotal movement on said first frame, a pair of spacedapart arms mounted on said second frame for movement therewith, a chase pivotally mounted beneath said arms and positioned over said work on said bed during printing, a screen removably mounted on said chase, a carriage assemblymounted on each of said arms for movement therealong, a drive arm connected to each of said carriage assemblies, press drive means mounted on said second frame and operatively connected to each drive arm to drive each drive arm and thereby move each of said carriage assemblies in associated, reciprocal fashion along said arms, the improvements including pivot points disposed on opposite sides of said first frame and forming a horizontal axis about which said second frame is pivotally moved during a printing cycle, said pivot points disposed generally in the horizontal plane of said surface of said bed adjacent a rear edge of said surface and allowing a rear portion of said second frame on which said press drive means is mounted to be swung below said horizontal plane of said surface of said bed during the printing cycle to prevent smearing contact between said screen and said work on said bed by never allowing any portion of said screen to move below the horizontal plane of said pivot points during movement of said second frame, said press drive means being mounted entirely on said rear portion of said second movable frame to move said carriage assemblies reciprocally along said arms during a printing cycle, and to pivot said second movable frame relative to said first fixed frame during the printing cycle, means operatively connecting said press drive means mounted on said second frame to said drive arms pivotally mounted on said first frame, said press drive means operatively engaging said first frame to pivotally move said second frame about said pivot points during the printing cycle, said press drive means moving said second movable frame and said drive arms relative to one another during the printing cycle, such that, for a desired period of time, the disposition of said means connecting said press drive 13 means to said drive arms causes said carriage assemblies to be maintained adjacent a selected point along said arms during said upward movement of said second frame to eliminate dripping of ink on said work.

10. The printing press of claim 9 wherein said press drive means includes a power drive shaft rotatable about a central axis, said power drive shaft having a cam mounted for rotation therewith near one end thereof and linking means mounted on an opposite end thereof and operatively connecting said press drive means with said drive arms to pivot said drive arms relative to said first frame, said cam engaging a cam fol lower mounted on said first frame to move said second frame about said pivot point, said cam and said linking means being moved by said power drive shaft driven by said press drive means, such that as the rotation of said cam causes said second frame to be pivoted upward with respect to said bed near the end of a printing stroke, further movement of said linking means will, through a desired period of time, cause sufficient backing movement of said drive arms and said connected carriage assemblies to preclude forward creep of said carriage assemblies along said spaced-apart arms during said upward movement of said second frame.

11. The improvement set forth in claim 9 wherein said drive arm includes a pair of spaced-apart L-shaped arms pivotally mounted on said first fixed frame within the side margins of said chase, said L-shaped arms being mounted on a common axis which is in generally vertical alignment with the horizontal axis between said pivot points of said second frame on said first frame.

12. The improvement set forth in claim 9 wherein said press drive means includes a power drive shaft rotatable about a central axis and adjustable linkage means to impart motion from said power drive shaft to each drive arm to drive said carriage assemblies reciprocally along said arms, said central axis of said power drive shaft, said axis ofsaid pivot points and an axis extending between said drive arms generally forming a triangulate prismatic arrangement during the printing cycle, to permit adjustment of the length of the stroke of said carriage assemblies by adjustment of said linkage means connecting said drive shaft and said axis extending between said drive arms.

13. The improvement set forth in claim 9 wherein said chase is mounted on said horizontal axis defined by said pivot points on said first frame and is independently pivotal about said axis to allow peeling of said screen during the printing cycle, while always having a portion thereof maintained in proper registered relation to said bed to facilitate registration of said chase with respect to said bed and said first frame.

14. In a printing press having a first fixed frame, a bed supported on said frame having an upwardly facing surface to receive work to be printed, a second frame mounted for pivotal movement on said first frame, a pair of spaced-apart arms mounted on said second frame for movement therewith, a chase pivotally mounted beneath said arms and positioned over said work on said bed during printing a screen removably mounted on said chase, a carriage assembly mounted on each of said arms for movement therealong, a drive arm connected to each of said carriage assemblies, press drive means mounted on said second frame and operatively connected to each drive arm to drive each drive arm and thereby move each of said carriage assemblies in associated, reciprocal fashion along said arms, said press drive means including a power drive shaft rotatable about a central axis, said power drive shaft having a cam mounted for rotation therewith near one end thereof and linking means mounted on an opposite end thereof and operatively connecting said press drive means with said drive arms to pivot said drive arms relative to said first frame, the improvements including pivot points disposed on opposite sides of said first frame and forming a horizontal axis about which said second frame is pivotally moved during a printing cycle, said pivot points disposed generally in the horizontal plane of said surface of said bed adjacent a rear edge of said surface and allowing a rear portion of said second frame on which said press drive means is mounted to be swung below said horizontal plane of said surface of said bed during the printing cycle, said linking means including a press drive arm fixedly mounted on said power drive shaft for rotation therewith, a rod pivotally connected at one end to an outward end of said press drive arm and moved in generally reciprocal movement thereby, an L-shaped slot arm fixedly mounted near one end thereof on a shaft, said shaft pivotally mounted on said first frame and having each drive arm connected thereto, each slot arm being adjustably connected near its opposite end to said rod, said cam engaging a cam follower mounted on said first frame to pivotally'move said second frame about said pivot point, said cam including a press lift cam having a varying radius, said cam and said linking means being moved by said power drive shaft driven by said press drive means to cause a related movement of said second frame and said drive arms sufficient to prevent creep of said carriage assemblies on said arms while said second frame continues to pivot upward when said press drive arm sweeps through an arc bridging the lowest point on its circle of rotation while said press lift cam engages said cam follower across the greatest radius of said cam.

15. in a printing press having a first fixed frame, a bed supported on said frame having an upwardly facing surface to receive work to be printed, a second frame mounted for pivotal movement on said first frame, a pair of spaced-apart arms mounted on said second frame for movement therewith, a chase pivotally mounted beneath said arms and positioned over said work on said bed during printing, a screen removably mounted on said chase, a carriage assembly mounted on each of said arms for movement therealong, a drive arm connected to each of said carriage assemblies, press drive means mounted on said second frame and operatively connected to each drive arm to drive each drive arm and thereby move each of said carriage assemblies in associated, reciprocal fashion along said arms, the improvements including pivot points disposed on opposite sides of said first frame and forming a horizontal axis about which said second frame is pivotally moved during a printing cycle, said pivot points disposed generally in the horizontal plane of said surface of said bed adjacent a rear edge of said surface and allowing a rear portion of said second frame on which said press drive means is mounted to be swung below said horizontal plane of said surface of said bed during the printing cycle to prevent smearing contact between said screen and said work on said bed by never allowing any portion of said screen to move below the horizontal plane of said pivot points during movement of said second frame, and each drive arm being pivotally mounted on said first fixed frame and being driven by said press drive means in an operative, synchronized relationship to the movement of said second frame upward with respect to said bed such that said carriage assemblies are maintained adjacent a selected point along said arms during said upward movement of said second frame to eliminate dripping of ink on said work, each of said carriage assemblies including a carriage housing movably mounted on each of said arms, said drive arm being connected to each carriage housing to reciprocally move each carriage housing along said arms during the printing cycle, means pivotally mounted on each carriage housing for supporting a squeegee and a flood bar in associated relationship for movement relative to each other corresponding to the movement of said.

tion the same during movement of said carriage assemblies on said arms.

16. A printing press including a first fixed frame, a bed supported on said frame and having an upwardly facing surface to receive work to be printed, a second frame pivotally mounted on said first frame, a pair of spaced-apart arms mounted on said second frame for pivotal movement therewith toward and away from said bed, a chase pivotally mounted beneath said arms and positioned over said work on said bed during printing, a screen removably mounted on said chase, a carriage assembly mounted on each of said arms for movement therealong, each of said carriage assemblies having a carriage housing supported on said arm, parallelogram means pivotally mounted on each carriage housing for supporting a squeegee and a flood bar in associated relationship for pivoting movement relative to each other, a free sliding shuttle contained in each carriage housing and movable with respect thereto, said shuttle operatively connected to said parallelogram means to pivot said parallelogram means to shift said squeegee and said flood bar generally vertically with respect to one another upon movement of said shuttle relative to said carriage housing, drive arms pivotally mounted on said first frame and connected to each of said carriage housings, press drive means mounted on said second frame and operatively connected to said drive arms to drive said drive arms and thereby move said carriage assemblies reciprocally along said arms, and stops disposed near opposite ends of each of said arms to engage opposite ends of said shuttle when-said carriage assemblies are moved adjacent said stops and move said shuttle within each carriage housing to shift said squeegee and said flood bar relative to each other, the operative relationship between the pivotal movement of said second frame and the movement of said drive arms being such that said carriage assemblies are maintained adjacent said stops following a printing stroke for a desired period for time while said second frame is being pivoted on said first frame upward from said bed thereby to eliminate creep of said carriage assemblies along said arms and resulting dripping of ink upon said work.

17. The printing press set forth in claim 16 wherein a first member of said parallelogram means may be moved with respect to a second member of said parallelogram'and maintained in position by a push arm means to convert each carriage assembly to a non-flood scoop printing operation.

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Classifications
U.S. Classification101/123, 101/126
International ClassificationB41F15/08, B41F15/40
Cooperative ClassificationB41F15/0818
European ClassificationB41F15/08A4B