EP0650832A1 - Fabric stretching device - Google Patents

Abstract

In a device (10) for stretching a rectangular gauze material or similar fabric (12) in a printing frame (14), having tensioning devices (16) which are arranged on the sides of said printing frame and in which the fabric is fastened by means of a clamping mouth (18) in each case consisting of clamping jaws (32, 36), which are movable relative to one another and can be positioned one on the other under pressure on the closing path of a closing lever (50), and is subsequently tensioned in the pulling direction by a change in position of the clamping mouth units caused by a piston/cylinder unit for flow medium, a further closing path is disposed after the closing path determined by the closing lever (50), when the clamping jaws (32, 36) are moved together, said further closing path being controlled by a piston rod (72). Additionally, the piston rod (72) is to be part of the piston/cylinder unit for the pulling movement of the tensioning device (16). Assigned to the piston in the cylinder (20) are an open position of the clamping mouth (18) near to the clamping jaws (32, 36), a central position when the clamping jaws are closed, and an adjoining stroke path for the tensioning operation. <IMAGE>

Description

The invention relates to a device for clamping a piece of fabric, in particular a rectangular gauze material, on a pressure frame with clamping devices arranged on the sides thereof, in which the piece of fabric is fixed by means of a clamping jaw each of relatively movable clamping jaws that can be placed on the closing path of a locking lever under pressure, and then is tensioned in the pulling direction by a change in position of the clamping jaw units caused by a cylinder / piston unit for flow medium.

Such a device is described in CH-PS 679 918 with the note that the production of printed circuit boards in the screen printing process requires a very high accuracy of the piece of fabric used in a screen printing stencil, which is why an extremely uniform clamping of the piece of fabric is required; uneven stress distributions create distortions in the piece of tissue, and stress peaks occurring therein can lead to an undesirable tearing process. According to CH-PS 679 918, these disadvantages are to be made possible by a clamping jaw made of a pair of clamping jaws which can be closed by means of a mechanical lever system and which is connected to the free end of a piston rod of the cylinder / piston unit by a universal joint. The mechanical pressing together of an upper jaw by a closing lever on a lower jaw fixed in the pressing direction does not permit its individual application with a compressible force, ie it cannot be adapted to the respective circumstances when the piece of tissue is clamped.

Knowing this state of the art, the inventor has set himself the goal of improving the device of the type mentioned at the outset while avoiding the identified defects and of making the adaptation of the pressing force on the clamping jaws controllable during the clamping process.

The teaching according to the independent claim leads to solving this problem; the sub-claims describe particularly favorable further training.

According to the invention, when the jaws are brought together, the closing path determined by the locking lever is followed by a further closing path under the control of the piston rod of the cylinder piston such that the piston in the cylinder has an opening position of the clamping jaw close to the jaws, a middle position when the jaws are closed after a partial stroke length, and a subsequent stroke path are assigned for the clamping process. A piston disk is preferably assigned to the piston rod.

According to a further feature of the invention, a short-stroke cylinder is provided, by means of which the respective clamping jaw is arranged below the surface of the printing frame before the piece of tissue is inserted, and can be closed after insertion, after which that short-stroke cylinder can be actuated to unlock a slide and the clamping jaw can be adjusted above the surface is. The clamping jaw is also to be held in this gripping position until a latching member for the short-stroke cylinder is released, a piston disc being able to be guided into the central position over the partial stroke length.

The cylinder held at the end by a swivel bearing on the base or base profile is displaceably mounted on the other side in a pipe socket on which the piston rod is fixed with its end remote from the piston. In addition, the piston rod passes through an end plate of the cylinder, wherein the piston rod rests movably in its sealed through bore.

It has proven to be advantageous to link the pipe socket to a guide element and to pivotally connect it to a carriage carrying the clamping jaws; the latter should be mounted on a profile designed as a base element.

The guide element is advantageously a bracket, the legs of which overlap the two side surfaces of the profile and are connected to the slide by an axis of rotation. Parallel to the latter, the slide carries a pivot axis for a hood-like support member of the movable jaw.

It is also within the scope of the invention that the hood-like support member as a swivel body with parallel side walls - flanking the pipe socket - connects to the swivel axis of the slide and holds the clamping jaw from above with a front edge parallel to the swivel axis. In addition, the hinge point for the pipe socket on the other side of the axis of rotation on the stirrup leg should be opposite a hinge point for a handlebar rod, which is articulated on the other side of its swivel body.

According to a further feature of the invention, a hinge pin is connected as a hinge between the handlebar and swivel body - via a bolt rotatably mounted therein - to a rocker arm, the other end of which offers an elongated hole to an articulated axis of the bracket.

The hinge axis for the swing arm is guided according to the invention by the bracket leg about its hinge point for the handlebar.

The special assignment of the bracket and the swivel body slipped over it like a groove to the slide produces one with their axes and the articulation points for the strand-like connecting elements connecting them - handlebar and swing arm Relative movement of the jaws that can be precisely controlled by mechanics and fluid.

It has proven to be particularly favorable to make the profile guiding the carriage liftable by means of a lifting cylinder which is mounted below the profile adjacent to the printing frame. In addition, a locking member is to be arranged in the vicinity of the lifting cylinder, which engages in the carriage in the front end position holding it. According to the invention, the clamping jaw can also lie in an end position of the slide above a plane determined by the frame.

Fig. 1:

die Draufsicht auf eine Vorrichtung zum Aufspannen von Siebmaterial für das Siebdruckverfahren mit vier Gruppen von Spanneinrichtungen;

Fig. 2:

die gegenüber Fig. 1 vergrößerte Frontansicht einer Spanneinrichtung;

Fig. 3:

die Seitenansicht zu Fig. 2;

Fig. 4:

ein geschlossenes Klemmaul der Spanneinrichtung in gegenüber Fig. 3 vergrößerter Seitenansicht;

Fig. 5:

das Klemmaul der Fig. 4 in geöffneter Stellung;

Fig. 6:

das Klemmaul der Fig. 4, 5 in zwei verschiedenen Stellungen;

Fig. 7:

eine teilweise geschnittene Frontansicht von Teilen der Fig. 4, 5;

Fig. 8:

den Schnitt durch eine Gelenkstelle der Spanneinrichtung;

Fig. 9:

den Schnitt durch einen Teil eines Zylinders der Spanneinrichtung;

Fig. 10:

die teilweise Seitenansicht eines Details der Fig. 4;

Fig. 11:

den gegenüber Fig. 10 verkleinerten Längsschnitt durch den gesamten Zylinder mit unterschiedlichen Positionen einer Kolbenscheibe;

Fig. 12:

ein vergrößertes Detail aus Fig. 1 in geschnitten skizzierter Wiedergabe.

Further advantages, features and details of the invention result from the following description of preferred exemplary embodiments and from the drawing; this shows in

Fig. 1:

the top view of a device for clamping screen material for the screen printing process with four groups of clamping devices;

Fig. 2:

the enlarged front view of Figure 1 of a clamping device.

Fig. 3:

the side view of Fig. 2;

Fig. 4:

a closed clamping mouth of the clamping device in an enlarged side view compared to FIG. 3;

Fig. 5:

the clamping jaw of Figure 4 in the open position.

Fig. 6:

the clamping jaw of Figures 4, 5 in two different positions.

Fig. 7:

a partially sectioned front view of parts of Figures 4, 5;

Fig. 8:

the section through an articulation point of the clamping device;

Fig. 9:

the section through part of a cylinder of the clamping device;

Fig. 10:

the partial side view of a detail of Fig. 4;

Fig. 11:

the reduced compared to Figure 10 longitudinal section through the entire cylinder with different positions of a piston disc.

Fig. 12:

an enlarged detail of Fig. 1 in a cut representation sketched.

A device 10 for clamping a rectangular piece of stuff or a web 12 of preferably gauze-like screen material for use in the screen printing process has - along the four sides of a frame 14 - a plurality of clamping elements or tensioning devices 16. These each grip a section of the web 12 in its edge region with a clamping jaw 18 (FIGS. 2, 3) and tension the web 12, which is then fixed all around, by adjusting one pulling cylinder 20 in the pulling direction x. In Fig. 3, the web 12 rests on the surface 13 of the frame 14 and is pulled down from its outer edge to the clamping jaw 18 in its closed position at an angle of approximately 6 °.

In Fig. 1 is at 15 from line 15 _a with max. 10 bar of compressed air-fed control unit, from which three control lines 15 _b to 15 _d originate.

The tensioning device 16 has, on a base rail 22, a channel-like wedge profile 24 that opens downwards towards it and has a sliding surface 25 that is inclined at an angle w, over which — above a central longitudinal slot 26 of length a of the wedge profile 24 — a carriage 28 is movably supported. On the front side of the wedge profile 24, a stop tongue 30 projects between which and the frame 14 runs and an adjustable holding bracket 31 according to FIG. 3, which can be locked in place by a transverse pin 31a. On the side facing away from the frame 14 of the stop tongue 30, a short-stroke cylinder 27 is attached to the channel-like wedge profile 24, said cylinder being on the base rail 22 supports and which is explained in more detail with respect to FIG. 12.

Transversely to the longitudinal axis M of the tensioning device 16, a lower clamping jaw 32, which projects on both sides and is designed as a channel profile, is cast on the slide 28, in whose upwardly opening channel space a strip 34 of elastic material is held. In an upper jaw 36 there are two parallel elastic round profiles 37 which are also elastic.

4 shows in particular that the upper jaw 36 is a profile strip which is fixed to a downward-pointing pressure edge of a cross-sectionally triple-angled apron 38; the latter is firmly connected to a hood-like swivel body 40 of a U-like cross section, which opens downwards and through which a swivel axis 42 of the slide 28 passes.

On the slide 28, parallel to the swivel axis 42 and at a distance b of approximately 65 mm from it, an axis of rotation 44 is provided for a bracket 46 - movable within the swivel body 40, the two legs 47 penetrated by it parallel to the side surfaces 23 of the Wedge profile 24 are movable. A hand or closing lever 50 protrudes from the upper yoke web 48 connecting the bow legs 47 and can be moved in a central longitudinal recess 39 of the apron 38 between the open position of the clamping jaws 32, 36 and their closed position.

At a distance e of 40 mm here, a pipe socket 54, which can be moved in a longitudinal recess 29 of the slide 28, is articulated on the bracket legs 47 by a pair of aligned pivot pins 52 (FIGS. 5, 6).

According to FIG. 4, a straight line G2 runs through the axis of rotation 44 and a further point of articulation 56 at an angle t of approximately 135 ° to the connecting straight line G1 of the axis of rotation 44 and the hinge pin 52. In this - approximately the same distance e from the axis of rotation 44 - - On the leg 47, a two-piece handlebar rod 57 is mounted, which on the outside of the swivel body 40 connects this with a hinge pin 58 at the other end. At 60, a coil spring around an axial telescopic part of the length-adjustable handlebar rod 57 is indicated; the coil spring 60 can be provided at the foot of the handlebar rod 57 (Fig. 1, 5) or near its upper end (Fig. 4, 6).

Approximately in the middle between the axis of rotation 44 and the hinge point 56 - and laterally offset by a dimension n of approximately 18 mm - there is also a hinge pin 62 on the leg 47 of the bracket 46, which bolt moves into an elongated hole 63 within the swivel body 40 Swing arm 64 reaches.

The path of the individual parts 40, 46, 57, 64 from the open position of the clamping jaws 32, 36 indicated by the broken line about the pivot axis 42 and axis of rotation 44 into the closed position can be seen in FIG. 6. The hinge pin 52 generates a circular contour K1 about the axis of rotation 44 on its way, the hinge point 56 a circular contour K2. These paths K1, K2 result in a circular contour K3 as the movement path of the articulation pin 58.

The upper end of the rocker 64 is designed according to FIG. 8 as a round end pin 65, which is encompassed by a helical spring 60, and is rotatably attached to the articulated pin 58 of the handlebar rod 57. This hinge pin 58 is seated in a bearing pin 66 of diameter f of approximately 16 mm, which in turn is surrounded by a sleeve 68 which is welded on the inside to the roof part 38d of the apron 38. This sleeve 68 offers on the downward part of its circumference a guide slot 69 for that end bolt 65. In one embodiment, not shown, an axle eye in the head of the handlebar rod 57 is of a pin-like shape of the bearing pin 66 enforced and connected in this way to the depository.

The pipe socket 54, which is closed at the end with a plate 55 and - as mentioned - attached to the bracket 46 by means of articulated bolts 52, receives the head end of the pull cylinder 20 mentioned at the beginning. In another embodiment, a diametrical yoke rod is provided instead of the end plate 55.

In the end plate 55 of the pipe socket 54 with a diameter d1 of here 58 mm, the threaded end 71 of a piston rod 72 is screwed into the longitudinal axis A of the pipe socket 54 through the central bore 74 of an end wall 75 of the pull cylinder 20 in its interior 76 - of a diameter d2 of 50 mm - protrudes and is connected with its other end to an axially displaceable piston disk 78 therein. Sealing O-rings are identified at 79.

The tube wall 80 of the pull cylinder 20 is seated with its end distal to its end wall 75 sealed at an end plug 82 which is articulated at 84 to a rear flange 86 projecting from the base rail 22.

5 is open, the piston disk 78 is in the open position indicated in FIG. 11 at I near the end wall 75 and at a distance of the stroke h from its right-hand end position III in FIG. 11. The stroke h of the piston disk 78 measures approximately 150 mm in the embodiment shown. The angle q described when the piston disk 78 is transferred from the central position II into the opening position I described above from the articulation point 56 is approximately 56 ° (FIG. 6).

The clamping jaw 18 can be opened by manual actuation of the closing or hand lever 50, but is normally carried out pneumatically, in that fluid enters the pull cylinder 20 and acts on the piston disc 78. The piston disc 78 is from any position of the Stroke h moved to the central position II in the open position I.

In this process, the carriage 28 is also brought into the front position and fixed, a locking pin 90 guided in a U-profile 91 being pushed by a spring 60 _a along an inclined surface 92 of a link block 93 into the provided recess 94.

Since the link block 93 - preferably made of plastic - is fixed on the underside of the carriage 28, the latter is held in the described gripping position until the catch pin 90 is released from the catch recess 94. A movable pawl - not shown here - can also serve as the locking element.

When inserting the web 12 into the open jaw 18, the upper edge of the strip 34 made of elastic material is about 2 to 3 mm below the surface 13 of the front printing frame 14. After inserting the web 12, the jaws 32, 36 of the jaw 18 with the Closing or hand lever 50 placed on top of one another and prestressed until the position shown in FIG. 4 is reached. The hinge pins 62 of the pair of the rocker 64 are seated on their respective elongated hole bases and lie behind the associated handlebar rod 57 by the amount n of lateral displacement mentioned.

This prestressing process described can also be carried out pneumatically, in that fluid is applied to the piston disk 78 via the prechamber or the pressure chamber 88 and is pushed from the open position I shown in FIG. 11 into the central position II over a partial stroke length h1 of approximately 50 mm.

Before the actual tensioning process, the short-stroke cylinder 27 attached to the wedge profile 24 is controlled via a line 97 indicated in FIG. 3 in such a way that the link block 93 is lifted out of the locking position and releases the slide 28 so that it can be guided in the pulling direction x.

The clamping jaw 18 also rises by the stroke of the short-stroke cylinder 27 and holds the web 12 for the tensioning process approximately 8 to 10 mm above the surface 13 of the frame 14 in front. This distance from the frame 14 serves above all to avoid injuries to the web 12 when Clamping process.

For the tensioning process, the pre-chamber 88 delimited by the end wall 75 and the piston disk 78 is acted upon by pneumatic fluid via a line indicated only in FIG. 3 at 95, thereby generating an adaptable pneumatic closing force on the clamping jaw 18, in addition to the mechanical closing force.

The distance i of FIG. 11 relative to the partial stroke length h1 to the full stroke length h determines the possible clamping path of the tensioning device 16 - but usually the full stroke length h is not used at all.

After the tensioning process, the clamping jaw 18 is lowered into the position described for FIG. 3, so that the web 12 rests on the frame 14 for gluing.

In FIG. 11, an indentation on the inner surface of the rear plug 82 of a further exemplary embodiment is merely indicated above the longitudinal axis A at 98. The piston rod nut 73 holding that piston disk 78 is immersed in this recess 98 in the end position III, whereby the stroke length is extended by the depth dimension k of the recess 98.

By introducing fluid into a rear chamber 89 with variable volume between the piston disk 78 and the end plug 82 via a further line 96 (FIG. 3), the piston disk 78 can be pressed against the pulling direction x in addition to the mechanical return, in order to clamp the jaw 18 to open.

Claims (12)

Device for clamping a piece of fabric, in particular a rectangular gauze material, on a pressure frame with tensioning devices arranged on its sides, in which the piece of fabric is fixed by means of a clamping jaw each of relatively movable jaws that can be placed on the closing path of a locking lever under pressure, and then by a cylinder / Piston unit for flow medium caused change in position of the clamping jaw units in the direction of tension,
characterized,
that when the jaws (32, 36) are brought together, the closing path determined by the locking lever (50) is followed by a further closing path under the control of a piston rod (72) such that the latter in the cylinder (20) has an opening position close to the clamping jaws (32, 36) (I) of the clamping jaw (18), a middle position (II) with the clamping jaws closed after a partial stroke length (h 1) and an adjoining stroke path (stroke length i) are assigned for the clamping process. Apparatus according to claim 1, characterized in that a short-stroke cylinder (27) is provided, by means of which the respective clamping jaw (18) is arranged below the surface (13) of the front printing frame (14) before the tissue piece (12) is inserted, and after the insertion It can be closed, after which the short-stroke cylinder can be actuated to unlock a slide (28) and the clamping jaw can be adjusted above the surface. Device according to claim 1, characterized by a piston disc (78) on the piston rod (72), the latter being part of the cylinder / piston unit for the pulling movement of a tensioning device (16). Device according to one of claims 1 to 3, characterized in that the clamping jaw (18) is held in this gripping position until a latching member (90) for the short-stroke cylinder (27) is released, the piston disc (78) being in the central position (II) is feasible over the partial stroke length (h 1). Device with a rail-like base element and pivot bearing for the cylinder rising therefrom according to one of claims 1 to 4, characterized in that the cylinder (20) is displaceably mounted at the other end in a pipe socket (54) on which the piston rod (72) with its the Piston (78) distal end (71) is fixed, the piston rod (72) possibly passing through an end wall (77) of the cylinder (20) and the piston rod movably supported in the sealed through bore (74). Device according to at least one of claims 1 to 5, characterized in that the pipe socket (54) is articulated to a guide element (46) and this is pivotally connected to a slide (28) which carries the clamping jaws (32, 36) and in the direction of pull (x) movably mounted on a profile (24) as the base element. Device according to one of claims 1 to 6, characterized by a guide element designed as a bracket (46), the legs (47) of which overlap the two profile sides (23) and are connected to the slide (28) by an axis of rotation (44), where appropriate the bracket is arranged within a hood-like support member serving as a swivel body (40) and is connected on each side to it by two articulated rods (57, 64) which are articulated on the bracket at a distance (n) from one another. Device according to at least one of claims 1 to 7, characterized in that the slide (28) parallel to the axis of rotation (44) for the bracket (46) has a pivot axis (42) for the hood-like support member (40) of the movable clamping jaws (36) . Device according to at least one of claims 1 to 8, characterized in that a joint pin (58) is connected as a joint between one of the joint rods (57) and the swivel body (40) to a rocker arm (64) than the other joint rod, the other end of which Offers elongated hole (63) for an articulated axis (62) of the bracket (46). Apparatus according to claim 7 or 9, characterized in that the hinge axis (62) for the rocker arm (64) is arranged such that it can be guided through the hanger arm (47) around its hinge point (56) for the hinge rod formed by a link rod (57). Device according to at least one of claims 1 to 10, characterized in that the swivel body (40) with parallel side walls connects the pipe socket (54) flanking the swivel axis (42) of the slide (28) and with a front edge parallel to the swivel axis the clamping jaw ( 36) holds, and / or that the hinge point (52) for the pipe socket (54) on the other side of the axis of rotation (44) on the stirrup leg (47) is opposite a hinge point (56) for the handlebar rod (57), which is on the other side Swivel body (40) is articulated. Device according to at least one of claims 1 to 11, characterized in that the profile (24) guiding the slide (28) is arranged to be liftable by means of a lifting cylinder (27) which bears adjacent to the pressure frame (14) below the profile, where appropriate the A locking element (90) is assigned to the lifting cylinder, which engages in a holding position of the carriage (28) in an end position.

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