A silk screen printer

Abstract

 The invention relates to a silkscreen printer having a cylindrically curved printing table intended for applying print to print material. The printer further comprises a stencil which is stretched in a stencil frame arranged for reciprocating movement in response to reciprocating of the printing table (2), and also a squeegee device which is intended to press the stencil against the printing table and therewith transfer print onto print material located between the printing table and the stencil. The printer further comprises a gripper (8) which co-acts with the printing table (2) and which is intended to grip firmly the forward end portion (3a) of the print material (3), as seen in the direction of movement, during at least a part of the printing sequence.
The gripper (8) is mounted in the printing table (2) for pivotal movement in the direction of the longitudinal curved extension of the printing table. When occupying a registered position the gripper (8) is pressed against a stop means (13) by means of a spring device (16) such as to register the gripper in relation to the printer chassis (10), this registration being effected without taking into account the stop position of the stencil frame and print­ing table (2).
It is suggested that Figure 3 is published together with the abstract.

Description

FIELD OF INVENTION

[0001] The present invention relates to a silkscreen printer, and more particularly, but not exclusively, to a silk­screen printer of the kind which has a curved printing table, preferably a cylindrical printing table, which is mounted for reciprocating movement.

[0002] Silkscreen printers of the kind which include a flat sten­cil frame or frame carriage, in which a stencil is held stretched, and a cylindrical printing table are normally constructed to apply print to a hard and inflexible print material, or to apply print to material which is only slightly flexible.

[0003] This category of silkscreen printer can be divided into two subordinate groups, namely:

a) Silkscreen printers in which the material to receive print is held firmly by gripping devices arranged on a stencil frame.

b) Silkscreen printers in which the material to receive print is held firmly by gripping devices arranged on the printing table.

[0004] The printer classified under group a) above is primarily intended for printing on hard print material, whereas the printer classified under group b) can also be used advan­tageously to print flexible material, and even very thin material.

[0005] The present invention relates to silkscreen printers of the kind classified in group b).

[0006] Silkscreen printers with which a stencil is stretched in a frame or frame carriage which can be moved reciprocatingly in response to the reciprocal movement of the cylindrical printing table are known to the art. These known printers also include a squeegee device or arrangement which is stationary in relation to the printer chassis and which is intended, inter alia, to press the stencil against the print material and the printing table, or drum, and to transfer print to the print material located between the printing table and the stencil, through relative movement of the squeegee and the stencil.

[0007] It is also known with printers of the kind to which the invention relates to provide the printing surfaces of the printing table with recesses which co-act with gripping devices in a manner to hold firmly the forwardly located end portion of the print material, as seen in the movement direction, at least during a part of the printing sequence.

[0008] The gripping devices used in this regard normally have the form of two pairs of gripping fingers which clamp the print material at its forwardly located end portion.

BACKGROUND PRIOR ART

[0009] The British Patent Specification No. 1 467 910 teaches a silkscreen printer of the kind which comprises a recipro­catingly movable cylindrical printing table or drum and (although not shown) a frame or frame-carriage in which a stencil is held stretched and which is reciprocatingly movable in the horizontal plane, this horizontal, recipro­cal movement of the stencil frame being controlled by the pivotal movement of the drum or printing table.

[0010] This known printer also includes a gripper for holding firmly the sheet of material to receive print, here refer­ red to as the print material. The gripper is mounted on the printing drum and is moved by the drum in a circular path which is coincidental with the upper printing surface of the drum.

[0011] In the case of a silkscreen printer belonging to group b) above, means are provided for registering the position of thin print material precisely in relation to the gripper(s) on the drum, even though the gripper(s) may not be located in a registered position when the gripper stops rotating, together with the drum.

[0012] The present invention can be said to constitute a further development of the silkscreen printer described and illus­trated in the aforementioned British Patent Specification.

SUMMARY OF THE INVENTION

TECHNICAL PROBLEMS

[0013] It is known that in the case of silkscreen printers in general and in particular in the case of silkscreen printers which incorporate a cylindrical or part-cylin­drical reciprocatingly movable printing table, or drum, (stop-cylinder-machines), difficulties are experienced in returning the printing drum, gripper and frame to, and stopping the same in, one and the same precisely located position, a registered position, in which the gripper on the printing drum is able to grip print material that has been brought to a precise, registered position at a slightly earlier stage of the printing sequence.

[0014] It will be understood that the same difficulties are ex­perienced when the reverse applies and the gripper is first brought to a precise registered position and the print material is intended to be displaced subsequently to its registered, precise position, in which the gripper can grip said registered material.

[0015] Since the oscillating energy for the printing drum becomes high when the drum is rotated backwards and forwards at high speed, and since the mass of the frame must also be included as a positive contribution to the prevailing kinetic energy, a highly qualified technical problem re­sides in the provision of means whereby the printing drum, with gripper, and the frame can be brought to stop at a pre-determined exact position. Naturally, the kenetic energy which must be overcome becomes progressively great­er with the higher permitted printing speeds, which in­creases the difficulties of stopping the printing drum and the frame in one and the same registered position at a selected constant printing speed.

[0016] Since, in order to apply print with greater accuracy in silkscreen printers, it is necessary that the gripper and the print material gripped thereby, and the stencil, all adopt one and the same relative position during each printing sequence, a technical problem resides in the pro­vision of conditions which will enable the gripper to be arranged for movement in the printing drum, or table, (thus not always stationarily in relation to the prevail­ing rotary position of the printing drum) in spite of the large oscillatory masses and kinetic energies involved with respect to the drum and frame, and then to realize that solely the gripper mounted on the printing drum can, in such case, be caused to take a pre-determined exact position, inter alia, in relation to the printer chassis, without taking the stop position of the printing drum and the frame (the stencil) relative to the printer chassis into account.

[0017] When the gripper, the print material gripped thereby, and the stencil can be allowed to take any non-registered position, a technical problem resides in the provision of simple means whereby the print material and the stencil can be brought to exact registry with one another during the subsequent printing sequence.

[0018] When taking the aforesaid problems into consideration, it will be seen that a further technical problem resides in the provision of conditions, with the aid of simple means, whereby adjustments can be made to the registered position of the gripper in relation to the printer chassis, and to maintain this position over a multiple of printing se­quences.

[0019] It will also be seen that a highly complicated, technical problem resides in the provision of conditions, with the aid of simple means, whereby the gripper can be registered in a correct position at high printing speeds, without needing to take into account the large oscillating masses and large kinetic energies of the printing drum and sten­cil frame, or at least not to any great extent.

[0020] When considering the present state of this art and the technical problems encountered with silkscreen printers of this kind, it is seen that a qualified technical problem resides in the realization that the requisite exactitude of the position of the gripper in relation to the printer chassis can be actually achieved by causing solely the to stop in a precise, registered position and to grip print material which has in turn been positioned precisely in relation to the printer chassis, while the stencil, stencil frame, and printing drum, or table, can be allowed to stop in any, non-registered position rela­tive to the printer chassis, and therewith afford a longer retardation time and retardation path, and that when returning the stencil and printing drum to a printing position, the stencil shall first be displaced to a posi­tion which is in register with the stationary gripper prior to beginning the actual printing sequence, through controlled mutual movement between stencil, printing drum, and print material.

[0021] Another predominant technical problem resides in the pro­vision of conditions, with the aid of simple means, where­by registration of the gripper can be effected, in spite of the large oscillating masses and high kinetic energies involved, solely by stopping the lightweight gripper and its attachment means, which engender only small kinetic energy, in a registered position relative to the printer chassis or to some other reference point, such as the registration of the material to receive print.

[0022] It will also be seen that a further technical problem re­sides in the provision of conditions, with the aid of simple means, which will enable the gripper to be tilted "loosely" in relation to the printing drum and thereby enable solely the upper part of the gripper to be brought to a registered position; i.e. conditions can be provided which will enable the upper part of the gripper to be urged by means of a spring to a precise registration posi­tion irrespective of the position of the stencil at that time, and which when the gripper grips print material which has been brought to a registered position with the aid of other means intended herefore, will afford the necessary registered co-action between gripper, print material and stencil throughout the whole of the follow­ing printing sequence.

[0023] It will also be seen that in silkscreen printers of this kind a further qualified technical problem resides in the realization that one or more of the aforesaid technical problems can be solved readily, by providing conditions in which first solely the upper part of the gripper is brought to a precise registered position relative to the printer chassis or some other reference point and into gripping engagement with precisely registered print mate­rial in said registered gripper position, and in which, with the gripper and print material registered in relation to the printer chassis, the stencil frame and stencil pattern are subsequently displaced to a registered posi­tion relative to the gripper, and in which, subsequent to further displacement of the gripper and print material, the stencil and print material are held in a mutually registered position during the whole of the printing se­quence.

SOLUTION

[0024] The present invention relates to a silkscreen printer, and more specifically, although not exclusively, to a silk­screen printer of the kind which includes a curved print­ing table, preferably a fully cylindrical or partially cy­lindrical printing table, by means of which print can be applied to print material, and which further includes a stencil frame which has a stencil stretched therein and which is arranged for reciprocating movement above the printing table in response to the reciprocating oscilla­tory movement of said table, and which also comprises a squeegee device or arrangement which is stationary in re­lation to the printer chassis and which is intended to press the stencil against the print material and the print­ing table, such as to transfer print onto print material located between the printing table and the stencil, through the medium of relative movement between the squeegee and the stencil.

[0025] The cylindrical printing table of the silkscreen printer to which the invention relates is also intended to co-act with a gripping device, referred to here as "gripper", which is effective in holding firmly the forwardly located end portion of the print material, as seen in the direc­tion of movement, during at least a part of the printing sequence.

[0026] For the purpose of solving one or more of the aforesaid technical problems it is proposed in accordance with the present invention that the gripper is mounted in the printing table for horizontal, pivotal movement and in one direction extends in the longitudinal extension or move­ment direction of the printing table, and that when occupying its registered position, the gripper can be pressed by a horizontally acting spring device against a first stop means provided on the printer chassis.

[0027] In accordance with one advantageous embodiment the posi­tion of the first stop means can be adjusted, therewith to enable the horizontal position of the gripper to be adapt­ed to the registering position and to bring the gripper to a desired registered position in relation to the chassis or some other reference point.

[0028] The spring device shall be capable of urging the gripper against a second stop means during a printing sequence, such that the gripper and the print material gripped thereby are registered relative to the stencil frame, and according to one preferred embodiment of the invention the first stop means is stationary in relation to the printer chassis or stand.

[0029] For the purpose of enabling the large kinetic energies engendered by the oscillating and linearly moving masses involved to be overcome by retardation essentially inde­pendently of the requirement of good gripper registration, and to permit longer retardation times to be employed without needing to reduce the printing speed, it is pro­posed in accordance with the invention that the printing table and the frame are arranged so as to be able to pass a location in which the gripper shall be brought to a registered position and there to leave the gripper for registration in said position and to continue towards a stop position at which no precise registration is required.

[0030] In accordance with one advantageous embodiment of the in­vention, the first stop means preferably has the form of a movement damping means which has a well defined terminal position, for example a hydraulic damper or like device, therewith to absorb gently the small kinetic energy en­gendered solely by the gripper.

[0031] The gripper is preferably constructed so that with the gripper in its registered position, the forward end of the gripper in which the print material is held, is elevated slightly, in order to provide easier access for the regis­tered print material and to facilitate the co-action be­tween gripper and material.

[0032] According to the invention the gripper is mounted on the outer, free end of an elongated member, which is pivotally attached at its other end. During the printing operation and during return movement to the registering position, i.e. when the gripper rests against the second stop means, the elongated member will extend in a direction which is related to a radius of the curved printing table, such that said outer end of the elongated member, and therewith the gripper, are located on one side of the radius while the pivotal attachment is located on the other side there­ of. Furthermore, the pivotal attachment shall be located at a given distance from the centre of rotation of the curved printing table.

[0033] The elongated member is arranged to be inclined, or to tilt, from the pivotal attachment in the direction of printing table movement, when said table is returned to a gripper registering position, upon completion of a print­ing sequence.

[0034] Thus, when the gripper is in its registered position and the printing table in general is able to move somewhat beyond this position, the elongated member will rotate so as to extend in the direction of said radius and thus elevate the gripper to a position above the printing sur­face of the table, therewith to facilitate access to and co-action with the registered print material.

ADVANTAGES

[0035] The advantages primarily afforded by a silkscreen printer constructed in accordance with the present invention re­side in the provisions of conditions which enable the gripper and the print material to be registered in rela­tion to the printer chassis or some other reference point while taking up the limited kinetic energy engendered by the gripper, therewith dispensing with the necessity of also bringing the stencil frame and printing table to registered positions. The stencil and the print material, however, are in mutually registered positions during a printing operation, as a result of first bringing the stencil into a position of registry with the gripper and the print material held thereby and thereafter taking measures to transfer the stencil pattern onto the print material.

[0036] These advantages are obtained by mounting the gripper on simple attachment means which can be moved pivotally in a horizontal direction along the printing table, and by enabling solely the gripper to take a pre-determined registered position relative to the printer chassis, so that the gripper, in said registered position, is able to grip print material, which has also been positioned pre­cisely, irrespective of the position of the stencil and without needing to pay too much attention to the inexacti­tude of the stop position of the stencil and the printing table, this inexactitude resulting from the large masses of and the large kinetic energies engendered by the sten­cil and printing table.

[0037] The primary characteristic features of the inventive silk­screen printer are set forth in the characterizing clause of the following claim 1.

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] A preferred embodiment which exhibits features significant of the present invention will now be described in more detail with reference to the accompanying drawings, in which:

Figure 1 is a simplified, perspective view of a prior art silkscreen printer which has gripping devices mounted on a cylindrical, reciprocatingly movable printing table;

Figure 2 is a simplified side view which illustrates the attachment of an inventive gripping device to the printing table, the gripping device being shown in a non-registered position; and

Figure 3 is a simplified side view of the inventive grip­ping device attachment of Figure 2 with the gripping de­vice in its registered position.

DESCRIPTION OF EMBODIMENTS AT PRESENT PREFERRED

[0039] With reference to the accompanying drawings, Figure 1 is a schematic perspective view of part of a silkscreen print­ing machine 1 comprising a curved printing table 2 which exhibits a cylindrically curved printing surface 2a, the printer being intended to apply print to print material 3. The illustrated printer also comprises a stencil 4 which is streteched in a stencil frame 5 in a conventional man­ner, only part of the stencil being shown in the Figure.

[0040] Figure 1 illustrates the print material 3 with its for­wardly located end of edge 3a located adjacent standard registering devices positioned on respective sides of the cylinder printing surfaces 2a. Immediately adjacent the registering devices are holding-down devices which are in­tended to hold the forwardly located end 3a of the thin print material against the printing surface 2a.

[0041] The reader is referred to the contents of the aforemen­tioned British Patent Specification 1 467 910 for a better understanding of the design of the individual printer com­ponents and the general method of operation of the printer.

[0042] It should be mentioned briefly that the reciprocating movement of the frame 5 and the stencil 4 is controlled directly by the rotational movement of the printing cylin­der, via a rack arrangement (not shown) extending along the side 5a of the stencil frame 5, and a toothed ring (not shown) extending around the cylindrical surface of the pressure cylinder 2.

[0043] During the printing sequence, the printing table moves to the right, as shown by an arrow in Figure 1, therewith causing the frame 5 and stencil 4 also to move to the right.

[0044] At this stage, a squeegee device 7 which is stationary in relation to the printer chassis is located in a position in which it co-acts with the stencil 4 and presses ink paste (not shown) which has been deposited on the stencil 4 through perforations present in the stencil and down onto the underlying print material 3.

[0045] Although not shown in Figure 1, the leading edge 3a of the print material 3 is gripped by means of two gripping de­vices, hereinafter referred to as grippers, each compris­ing respective gripping fingers and being arranged in the printing surface 2a of the cylinder.

[0046] The illustrated printer also comprises a squeegee device 7 or squeegee arrangement, which is illustrated schematical­ly and which is intended to press the stencil 4 against the print material 3 and the printing table 2a in a con­ventional manner, such as to transfer print onto the print material 3 located between the printing table and the stencil. The printing table 2a co-acts with the aforesaid two grippers, which are intended to hold the print materi­al 3 firmly at its leading edge 3a, as seen in the direc­tion of movement, during preferably the whole of a print­ing sequence, and in all events during at least part of said printing sequence.

[0047] Since the various devices and arrangements intended for effecting movement of the squeegee device 7, the recipro­ cating movement of the stencil frame 5, the movement of the printing table 2a and all other drive functions are of conventional design they will not be descirbed in de­tail in the present application, for the sake of simplici­ty.

[0048] Nothwithstanding this, however, it should be mentioned for the sake of clarity that the squeegee device 7 is arranged to be lowered during a printing sequence, so as to press the stencil 4 against the print material and the printing table 2a at the uppermost or highest point of the printing table 2a, and is held in this position as the print material 3 is displaced to the right in Figure 1 by the grippers.

[0049] Reference is now made to Figures 2 and 3 which show that one of the two grippers 8 is mounted for some degree of horizontal movement in a circular path around the printing surface 2a of the printing table 2.

[0050] It will be understood that various devices and means can be used to move the gripper 8 horizontally along the printing surface 2a of the printing table 2.

[0051] For example, the gripper 8 may be arranged to move along said printing surface 2a in a direction which extends in the direction of the longitudinal extension of the stencil frame or in its direction of movement during the printing operation.

[0052] Figure 2 illustrates how print material 3, and particular­ly the leading edge 3a of said material, takes a precisely registered position in relation to the printer chassis 10.

[0053] As indicated by the arrow, Figure 2 illustrates the print­ ing table 2 and the gripper 8 during movement towards a gripper registering position, namely in which a surface 11 on the gripper 8 is in co-action with a surface 12 on a first stop means 13, which is stationary in relation to the chassis 10.

[0054] During this movement a surface 14 on the gripper 8 rests against a surface 15 on the printing table 2a, therewith registering the gripper in relation to the printing table 2, the stencil 4 and the stencil frame 5.

[0055] Figure 3 shows that when the printing table is moved fur­ther to the left, the gripper 8 will abut the first stop means 13, therewith stopping further movement of the grip­per, the gripper 8 in this position having gripped the leading edge 3a of the print material with its gripping fingers 8a and 8b.

[0056] In this position the gripper 8 is registered relative to the chassis 10, but is not registered relative to the printing table 2a and the stencil 4, since these are dis­placed further to the left. This has been illustrated in the Figure by showing the printing table surface 15 lo­cated at a distance from the gripper surface 14. In practice this distance can be greater than that shown.

[0057] Figure 3 shows the gripper 8 in co-action with first stop means 13 provided on the printer chassis, although it will be understood that some other reference point may be cho­sen.

[0058] The differences between Figures 2 and 3 are intended to show that further displacement of the frame and the print­ing table 2a to the left, beyond the registered position of the gripper 8, can now take place without changing the position of the gripper 8 in relation to the stop means 13. During this movement of the gripper however, a spring 16 is allowed to expand or extend, such as to hold the gripper in the registered position.

[0059] It is now possible to allow the stencil frame 5 and printing table 2 to stop without paying direct attention to the desired precise registration of the gripper 8, pro­vided that the printing table 2 and the stencil frame can pass freely beyond the registered position. Thus, regis­tration of the gripper 8 in relation to the chassis, through the medium of the stop means 13, is quite inde­pendent of the position of which the stencil frame 5 and the printing table 2 stop.

[0060] If the stencil frame 5 and the printing table 2 are per­mitted to travel still further to the left than that il­lustrated in Figure 3, the frame 5 and the stencil 4 stretched therein will be in a still less registered posi­tion in relation to the gripper 8, the print material 3 and the chassis 10.

[0061] The gripper 8 comprises a multiple of reaction support surfaces or anvil surfaces 8b and a multiple of upwardly and downwardly movable fingers 8a which are intended to clamp the leading edge part 3a of registered print mate­rial 3 in the gripper registering position illustrated in Figure 3.

[0062] With a starting point from the respective Figure 3 posi­tions of the gripper 8, the print material 3, the printing table 2, the stencil 4 and stencil frame 5, and upon re­turn movement of the printing table 2 and stencil 4 in order to apply print to the print material 3, the stencil is first moved relative to the gripper 8 and the print ma­ terial 3 until the gripper 8 engages a second stop means which is formed when the surfaces 14 and 15 are brought into abutment with one another, wherewith the stencil is registered in relation to the gripper 8 and printing can be effected with both gripper 8 and material 3 and the stencil 4, or frame 5, being located in mutually regis­tered positions.

[0063] The position of the first stop means 13, and therewith the registering position of the gripper 8, can be adjusted with the aid of an externally screw-threaded stud which is arranged to cooperate with an internally screw-threaded sleeve, the stud and sleeve not being shown in detail in order not to complicate the drawing.

[0064] Thus, the printing table 2 and the stencil frame 5 of the illustrated embodiment are allowed to travel slightly be­yond the registered position of the gripper 8. The grip­per is thus located in a registered position in relation to the chassis, in which position the gripper is able to grasp and collect a sheet of print material 3 which has been registered precisely with the aid of other means in­tended for this purpose and which is intended for a subse­quent printing sequence.

[0065] As previously mentioned, the registered position of the gripper 8 can be adjusted with the aid of the stop means 13, this adjusted position thus applying to a multiple of printing sequences.

[0066] In order to further clarify the concepts fundamental to the present invention it can be mentioned that in silk­screen printers of this kind the stencil frame is dis­placed backwards and forwards in response to the recipro­cating movement of the printing cylinder, which therewith decides the speed at which printing is effected.

[0067] It will be obvious that large masses are in motion and that these masses engender large kinetic energies, and that is is extremely difficult to stop the stencil frame and printing cylinder in precisely one and the same ter­minal position irrespective of the printing speed.

[0068] Consequently, it is desirable to be able to register sole­ly the material in relation to solely the gripper irre­spective of the orientation of the stencil and printing table in said terminal position, and to therewith ignore the inexactitudes caused by large, oscillatory masses in the prevailing stop position of the printing table and stencil with stencil frame.

[0069] Accordingly, it is proposed in accordance with the inven­tion that the gripper 8 is pivotable and "loosely" mounted on the printing cylinder and that in a printing position or a return position the gripper is pressed against a stop in the printing cylinder 2 which causes the gripper 8, upon gripper movement to the left in Figure 1, to stop against a first stop means 13 which is stationary in re­lation to the printer stand or printer chassis, and in such a registered position is caused to engage a sheet of print material 3 which is registered in this position, while allowing the stencil frame 5 and the printing cylin­der 2 to continue to move, preferably through a consider­able distance, during extension of the spring 16, but with the gripper 8 loosely pivotally adapted so that it still remains in its registered position. When the stencil frame 5 and stencil 4, together with the printing cylinder 2, move from the illustrated Figure 3 position in the opposite direction during a printing sequence, there ini­tially occurs a relative movement between the printing table 2 (and the stencil 4 in the frame 5) and the gripper 8, but when the gripper 8 adopts a correctly registered position relative to the frame 5 and stencil 4 as a result of this relative movement, the gripper 8 accompanies move­ment of the stencil 4 and the printing table 2 as a result of co-action with the second stop means (14, 15).

[0070] This means that upon movement in the opposite direction, illustrated in Figures 2 and 3, the gripper 8 will be brought to a registered position relative to the printer chassis 10 by the stop means 13 with small energy absorb­tion, irrespective of the relative stop positions of the stencil positions of the stencil frame 5 and the printing cylinder 2 when collecting or gripping material 3 to be printed.

[0071] Thus, prior to commencing the actual printing operation, the gripper 8 is first brought to a registered position in relation to the frame 5 and the stencil 4, via movement of the printing table 2a, whereafter the actual printing operation takes place with the gripper 8, the print mate­rial 3 and the frame 5 and stencil 4 correctly positioned in relation to one another.

[0072] For the sake of simplicity corresponding components in Figure 1 have been identified with the same reference marks in Figures 2 and 3, although certain parts have been omitted.

[0073] The movement damper which functions as a first stop means 13 may be modified to provide a well defined terminal po­sition (a first stop) for the gripper 8 when the gripper rests against said stop under the bias exerted by the spring 16.

[0074] It will be seen from Figure 3 that the forwardly located end of the gripper 8 intended for gripping the leading edge part 3a of the print material 3 is elevated slightly in the registered position of the gripper.

[0075] It will be seen from Figures 2 and 3 that the gripping de­vices 8a and 8b of the gripper 8 are mounted on the outer end of an elongated member 20, which is pivotally mounted at its other end.

[0076] The elongated member 20 is intended to extend in a direc­tion related to the radius 21 of the curved printing table 2, such that said outer end and the gripping devices 8a and 8b are located on one side of the radius while the rotatable attachment 20a is located on the other side of the radius.

[0077] The angle herebetween is referenced a in Figure 2.

[0078] The rotatable attachment 20a is located at a distance b from the rotational centre 2ʹ of the curved printing table, this distance preferably being 15 to 50 % of the length of the radius, preferably about 30 %.

[0079] The elongated member 20 is arranged such that when the printing table 2 returns towards and beyond the registered position of the gripper 8 subsequent to a printing se­quence, the member is inclined at an angle a to the direc­tion of movement of the printing table.

[0080] When the gripper 8 occupies its registered position against the stop means 13, and when movement of the print­ing table 2 is permitted to continue beyond this position, the elongated member 20 rotates about its lower rotatable attachment 20a such that the elongated member 20 extends more in the direction of the radius 21 and the angle a decreases. The gripper 8 will therewith rise above the printing surface 2a of the printing table, as particularly illustrated in Figure 3.

[0081] The gripper 8 returns to the position illustrated in Fig­ure 2 upon commencement of a following printing sequence.

[0082] Figure 3 also shows in chain lines the position of the attachment 20a when the gripper 8 abuts the stop means 13.

[0083] It will be understood that the invention is not restricted to the aforedescribed exemplifying embodiment, and that modifications can be made within the scope of the follow­ing claims.

Claims

1. A silkscreen printer comprising a printing table, preferably a cylindrical printing table, adapted to apply print to print material, and having a stencil which is stretched in a stencil frame and located above the print­ing table, and which further comprises a squeegee device which is intended to press the stencil against the print­ing table and therewith transfer print onto print material located between the printing table and the stencil, the printer further comprising a gripper which is intended to grip the forward end portion of the print material, as seen in the direction of movement, during at least a part of the printing sequence, characterized in that the grip­per is movably arranged in the printing table and extends in the direction of the longitudinal extension of the printing table; and in that the gripper, in its registered position, can be pressed against a first stop means with the aid of a spring device.

2. A printer according to claim 1, characterized by means for adjusting the position of said first stop means.

3. A printer according to claim 1, characterized in that the first stop means is located against and is stationary in relation to the printer chassis or printer stand.

4. A printer according to claim 1, 2 or 3, characterized in that the printing table and stencil frame are arranged to pass beyond a position in which solely the gripper is in a registered position.

5. A printer according to claim 1, characterized in that the first stop means has the form of a movement damper having a clearly defined terminal position.

6. A printer according to claim 5, characterized in that the first stop means has the form of a hydraulic damper or like device.

7. A printer according to claim 1 or 10, characterized in that the forwardly located part of the gripper intended for gripping print material is located in a slightly ele­vated position, a registering position.

8. A printer according to claim 1 or 7, characterized in that the gripper is mounted on the outer end of an elon­gated member, which is pivotally mounted at the other end thereof.

9. A printer according to claim 8, characterized in that the elongated member is arranged to extend in a direction related to a radius of a curved printing table, such that the said outer end and said gripper are located on one side of the radius while the pivotal attachment is located on the other side thereof.

10. A printer according to claim 9, characterized in that the pivotal attachment is located at a distance from the rotational centre of the curved printing table.

11. A printer according to claim 8 or 9, characterized in that the elongated member is arranged to slope from the pivotal attachment towards the direction of movement of the printing table when the printing table returns towards and beyond a registered position of the gripper subsequent to a printing sequence.

12. A printer according to claim 11, characterized in that the elongated member is arranged to extend in the di­rection of the radius when the gripper occupies a regis­ tered position and when the printing table moves beyond this position, such that the elongated member lifts the gripper above the printing surface of the printing table.

Drawing