GB2028721A

GB2028721A - Stretching fabrics

Info

Publication number: GB2028721A
Application number: GB7927683A
Authority: GB
Original assignee: HALL MARK MACHINE IND Ltd
Current assignee: HALL MARK MACHINE IND Ltd
Priority date: 1978-08-25
Filing date: 1979-08-08
Publication date: 1980-03-12

Abstract

Tensioning apparatus, for example for the cloth forming a silk screen, includes a platform 22 movable relative to a frame 12 towards or away from which two pairs of opposed side members 26 are movable, the side members 26 and platform 22 being interconnected whereby movement of the platform, for example by an hydraulic jack 14, causes movement of all side members. The platform 22 may support a frame to be covered by tensioned cloth or this frame may be supported on a table 50, independent of the platform, provided with a separate hydraulic jack 54 for raising or lowering it. <IMAGE>

Description

SPECIFICATION Improvements in or relating to tensioning apparatus The present invention concerns improvements in or relating to tensioning apparatus, especially but not exclusively tensioning apparatus for cloth or the like for use in a screen printing apparatus. The invention is equally applicable for tensioning canvases, gauzes meshes and the like prior to their attachment to frames.

Prior apparatuses for tensioning cloth and the like have included side members with means for holding the edges of the cloth and means for moving opposed side members apart, normally said moving means including screw-threaded arrangements. A frame is then placed on and attached to the thus tensioned cloth.

According to the present invention there is provided tensioning apparatus including a platform, two pairs of opposed side members each provided with holding means, the platform and side members being operatively connected whereby movement of the platform in one direction cause corresponding movement of the side members to move the members of each pair away from or towards each other.

Preferably the platform is mounted for movement relative to a frame on which said side members are pivotally mounted, arms pivotally mounted to the side members and platform providing said operative connection. The length of the arms may be adjustable.

Preferably a hydraulic piston and cylinder device is provided for moving the platform.

The axis of the piston of the piston and cylinder device may be arranged in the direction of movement of the platform or may be arranged at an angle to said direction. In the latter case a bell-crank linkage is provided between the piston and the platform.

Preferably the apparatus includes a table on which a frame over which a tensioned cloth is to be fixed may be placed, the table being movable towards a tensioned cloth supported by said side members in the same direction of movement as the platform.

The table may be supported on the platform or may be arranged independently thereof and provided with a further piston and cylinder device to move it.

The independently arranged table is preferably supported on the piston of its piston and cylinder device in a manner permitting relative pivotal movement and a guide arrangement in the form of a telescopic tube and bar is preferably provided between the table and a fixed member of the apparatus to control said pivotal movement of the table.

The holding means may be adapted to hold the lateral edges of a cloth to be tensioned and may comprise a channel opening away from the corresponding channel on the other side member of the pair, a check member extending partially over the channel opening and a bar in the channel, the arrangement being such that with a piece of cloth covering the channel opening the bar may be pushed into the channel carrying the cloth with it, movement of the cloth to tend to extract it from the channel causing the bar to wedge between a channel wall and the check member thus wedging the cloth also. The edge of the channel over which the cloth extends and the bar may be provided with a protective covering of a resilient material.

One embodiment of the present invention will now be described by way of example only with reference to the accompanying drawings in which: Figure 1 is an elevation of a tensioning apparatus; and Figure 2 is a plan of the apparatus.

A cloth tensioning apparatus comprises a frame 10 fabricated by welding together box section members, the frame 10, in plan view being substantially rectangular. A sub-frame 12 extends across the frame and supports a hydraulic jack 14 arranged with its axis horizontal and its piston rod 16 connected by a cross head 17 to a pair of spaced bell-cranks 18 pivotally mounted on sub-frame 12 by an axle 20. A pair of links (not shown) pivotally mounted between the bell-cranks 18 and a platform or rising frame 22 cause upward and downward movement of the rising frame 22 on extension and retraction of the piston rod 16 respectively.

The frame 10 has hinges 24 fixed thereto, the hinges serving to pivotally mount side members 26 to the frame 10 in such a manner that the side members 26 can pivot outwardly away from the frame from a substantially vertical position to a position angled outwardly of the vertical. As the frame 10 is rectangular and each side thereof supports a side member 26 it will be appreciated that the apparatus includes two opposed pairs of side members 26 which pivot away from each other, the outer ends of the members thus having an outward and a downward component of movement.

The pivoting movement is achieved by providing a pair of connecting arms 28 between each side member 26 and the rising frame 22, the arms 28 extending between brackets 30 on the rising frame 22 and brackets 32 fixed to the side members 26, the attachment of the arms to the brackets being pivotal.

The length of each arm 28 is adjustable by means of a threaded adjusting rod 34.

Holding means 38 for the cloth or the like to be tensioned are provided at the outer end of each side member 26. Said holding means take the form of a channel 40 opening away from the corresponding channel on the opposed side member and being partially closed by a check member 42. A rectangular section bar 44 whose lateral dimension is greater than that of the channel is adapted forfitment in the channel to wedge the cloth therein, in a manner to be described in detail below. A protective resilient covering is provided on the upper edge of the channel and around the bar.

Atable 50 having a rectangular plan is mounted within the rising frame 22 on the end of the piston rod 52 of a further hydraulic jack 54, the axis of which is vertical. The mounting means 56 for the table are such that it can pivot relative to the rod 52 and the extent of this pivotal movement is controlled by a bar 58 fixed to the underside of the table so as to be loosely fitted in a tube 60 fixed to the sub-frame 12.

Diagonally extending, horizontally disposed arms 62 are fixed to each corner of the table 50 and are intended to support a frame to be covered by tensioned cloth.

In operation with the pistons of the jacks 14 and 54 retracted and the rising frame 22 and table 50 consequently at their lowest positions, a frame for example a screen printing frame over which a screen is to be tensioned is placed on the table 50, 62. The screen to be tensioned is then spread aver the top edges of the side members 26, which, with the rising frame 22 in its lowest position, will be substantially vertical.

The dimensions of the screen are such that it overlaps the side members whereby its edge portions may be forced into the channel 40 by the bar 44 with the bar in a substantially horizontal orientation.

The bar 44 is then tilted to the position shown in Figure 1 and as its lateral dimension is greater than the width of the channel 40 any movement of the screen tending to withdraw it from the channel, that is in a direction towards its opposite edge, will tend to increase the wedging action of the bar 44. Thus the screen edge portions are securely trapped in the holding means 38.

The jack 14 can now be operated to lift the rising frame 22 this movement in turr causing the arms 28 to force the side members 26 to pivot outwardly, thus tensioning the screen. The jack 54 is then operated to raise table 50 with the frame thereon and this movement continues until the upper face of the frame rests against the underside of the tensioned screen, and if desired, at this point'the screen may be attached to the frame. Further movement of either or both jacks could then take place to give a further tensioning effect, if desired.

Various modifications can be made without departing from the scope of the invention, for example different holding means 38 may be employed; these could be simple clamp arrangements, gripper pins, etc. the hydraulic jacks could be replaced by screw jacks or the like: and the connection means between the side members and the rising frame could take any suitable form. It would be possible to arrange that the jack for lifting the table was arranged horizontally, in which case a bell-crank linkage would be required, and the jack for the rising frame could be arranged vertically. It is also possible to dispense with the table and its jack and to support the frame to be covered on the rising frame.

Claims

1. Tensioning apparatus including a platform, two pairs of opposed side members each provided with holding means, the platform and side members being operatively connected whereby movement of the platform in one direction cause corresponding movement of the side members to move the members of each pair away from or towards each other.

2. Apparatus as claimed in claim 1, in which the platform is mounted for movement relative to a frame on which said side members are pivotally mounted, arms pivotally mounted to the side members and platform providing said operative connection.

3. Apparatus as claimed in claim 2, in which the length of said arms is adjustable.

4. Apparatus as claimed in any one of claims 1 to 3, in which a hydraulic piston and cylinder device is.

provided for moving the platform.

5. Apparatus as claimed in claim 4, in which the axis of the piston of the piston and cylinder device is arranged in the direction of movement of the platform.

6. Apparatus as claimed in claim 4, in which the axis of the piston of the piston and cylinder device is arranged at an angle to the direction r f movements of the platform.

7. Apparatus as claimed in claim d, fl which a bell-crank linkage is provided between the piston and the platform.

8. Apparatus as claimed in any one of the preceding claims, including a table on which a frame over which a tensioned cloth is to be fixed may be placed, the table being movable towards a tensioned cloth supported by said side members in the same direction of movement as the platform.

9. Apparatus as claimed in claim 8, in which the table is supported on the platform.

10. Apparatus as claimed in claim 8, in which the table is provided with a further piston and cylinder device to move it.

11. Apparatus as claimed in claim 10, in which the table is supported on the piston of its piston and cylinder device in a manner permitting relative pivotal movement,

12. Apparatus as claimed in claim 11, in which a guide arrangement in the form of a telescopic tube and bar is provided between the table and a fixed member of the apparatus to control said pivotal movement of the table.

13. Apparatus as claimed in any one of the preceding claims, in which the holding means is adapted to hold the lateral edges of a cloth to be tensioned and comprises a channel opening away from the corresponding channel on the other side member of the pair, a check member extending partially over the channel opening and a bar in the channel, the arrangement being such that with a piece of cloth covering the channel opening the bar may be pushed into the channel carrying the cloth with it, movement of the cloth to tend to extract it from the channel causing the bar to wedge between a channel wall and the check member thus wedging the cloth also.

14. Apparatus as claimed in claim 13, in which the edge of the channel over which the cloth extends and the bar are provided with a protective covering of a resilient material.

15. Tensioning apparatus substantially as hereinbefore described with reference to the accompanying drawings.

16. Any novel subject matter or combination including novel subject matter herein disclosed, whether or not within the scope of or relating to the same invention as any of the preceding claims.