GB1574274A

GB1574274A - Material tensioning apparatus

Info

Publication number: GB1574274A
Application number: GB1621578A
Authority: GB
Original assignee: RAWLINS G
Current assignee: RAWLINS G
Priority date: 1978-04-25
Filing date: 1978-04-25
Publication date: 1980-09-03

Description

(54) MATERIAL TENSIONING APPARATUS (71) I GRAHAM CLENTON RAW LINS, a British Subject of "Hylton", 401 Turnhurst Road, Packmoor, Stoke-on Trent, Staffordshire do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to apparatus for tensioning a material and enabling application of the material to a support frame for producing a sieve, or a screen for use in printing.

A machine for use in forming a sieve or printing screen has previously been proposed wherein a sheet material, for example gauze or cloth is applied to the machine and side gripping members are then moved outwardly in the plane of the sheet material to effect tensioning thereof. Thereafter a support frame for the screen is lifted into contact with the tensioned screen and the material of the screen is secured to the frame, for example by gluing. It is important to apply the correct tension to the sheet material and in the previously proposed machine the mechanical arrangement for effecting this is cumbersome and awkward to manipulate, and is very time consuming.

According to the present invention there is provided apparatus for tensioning a sheet material and enabling application of the material to a support frame, said apparatus comprising means for holding the sheet material in a non-tensioned condition, and means for tensioning the sheet material and maintaining same in engagement with a support frame for securing thereto while in a tensioned condition, the means for holding and tensioning the sheet material being controlled by fluid media.

Preferably the support frame can be mounted on a table member which is movable by a ram assembly between a first position wherein the sheet material can be held in the non-tensioned condition across the support frame, and a second position wherein the support frame is moved against the held sheet material to tension the latter and maintain engagement between the sheet material and the support frame.

Preferably also the means for holding the sheet material comprises a bar arrangement which is movable between a first nonclamping position and a second clamping position wherein a respective edge of the sheet material is clamped between the bar arrangement and gripper means on a frame structure of the apparatus.

An embodiment of the present invention will now be described by way of example only with reference to the accompanying drawings wherein Figure 1 is a sectional elevation of an apparatus according to the invention; Figure 2 is a plan view of the apparatus in Figure 1; and Figure 3 is an end elevation of the apparatus of Figures 1 and 2.

Referring to the drawings an apparatus for use in forming screens for printing comprises a frame structure 10 of generally rectangular configuration and preferably formed from welded hollow section frame members. The frame structure 10 is covered at its sides preferably by a suitable metal sheeting.

The apparatus is generally vertically disposed in use and are each side of the apparatus, substantially midway along the length thereof, an hydraulic ram assembly 12, has its cylinder 14 pivotally mounted at a lower end on brackets 16 which are fixed to respective horizontally extending frame members of the structure 10, its ram 18 being arranged to move vertically and mounting at its upper end a horizontally extending bar 20. The bar 20 has fixed thereto adjacent to each end, a downwardly extending tube 21 which is slidable on an upwardly extending guide rod 22 on the frame structure 10 to retain the bar 20 horizontal. On its upper face the bar 20 has friction means secured thereto, for example a layer of a friction material such as rubber.

At the upper end of the frame structure 10 gripping means is provided at each side above the respective bar 20 in the form of an elongate belt 24 formed of a friction material, for example rubber, which belt is attached to a lower face of a frame member extending horizontally of the structure 10.

Centrally within the frame structure 10 a main hydraulic ram assembly 26 extends vertically having its cylinder 28 mounted at its lower end on a support 30 and its ram 32 mounting at its upper end a table member 34 which is of rectangular configuration.

The table member 34 has a bar 36 on its upper surface extending centrally of the table member 34 parallel to one pair of opposed sides thereof.

The hydraulic rams 18, 32 are controlled from a common hydraulic power pack by means of appropriate controls (not shown), each pair of opposed rams 18 being operable together, and the ram 26 being individually operable, from an appropriate control console (not shown). Hydraulic check valves are provided for retaining the respective rams in their extended positions as necessary and preventing the rams from creeping down under pressure when the power pack is turned off.

In use, with the rams 18, 32 in a first non-operative position, four open-ended rectangular support frames 38 are positioned on the table member 34, each of the frames 38 having an edge resting on the bar 36 such that the frame is in an inclined position on the table member 34. A material, for example nylon, is laid across the upper end of the apparatus above the frames 38 with the edges of the sheet material passing under the belts 24. The rams 18 are then extended in opposed pairs such that the bars 20 are moved upwardly to clamp the respective edges of the sheet material against the belts 24.

When the material is clamped in position the ram 32 is then extended to move the table member 34, with the frames 38, upwardly against the sheet material thus tensioning the latter and bringing the frames into intimate engagement with the tensioned material by virtue of the inclination of the frames 38. To prevent any rotation of the table member 34 vertically extending tubes 40 are connected at their upper ends to the underside of the table member 34 and are slidable in vertical guide rods 42 which are connected at their lower ends to the support 30.

When the desired tension has been applied to the material, as can be determined from the applied hydraulic pressure, the material can be secured to the frames 38 by any suitable means, for example by applying glue through the material along the edges of the frame 38, and the hydraulic check valves enable the rams 18, 32 to retain the frames 38 in such contact with the sheet material as necessary. Once the material is permanently secured to the frames 38 the material can be cut around the latter to provide four screens for use in screen printing. The rams 18, 32 are retracted and the apparatus is then ready for re-use.

In a modification, the gripping means on the frame structure may comprise a strip of friction material retained in a complementary groove in a respective member of the frame structure at each side thereof. The respective bar is then preferably profiled to clamp the material against this strip.

This apparatus is therefore extremely quick and easy to operate and in addition is reliable and relatively simple to service and repair if necessary.

Various modifications may be made without departing from the invention. For example it is envisaged that the apparatus may be pneumatically operated and also the frame structure may be of a configuration other than that shown with the table member being adapted to support any suitable number of frames. Also the components of the guide arrangements 21, 22 and 40, 42 can be arranged and indeed any other suitable guide arrangement can be utilised.

WHAT I CLAIM IS: 1. Apparatus for tensioning a sheet material and enabling application of the material to a support frame, said apparatus comprising means for holding the sheet material in a non-tensioned condition, and means for tensioning the sheet material and maintaining same in engagement with a support frame for securing thereto while in a tensioned condition, the means for holding and tensioning the sheet material being controlled by fluid media.

2. Apparatus according to Claim 1, wherein the support frame can be mounted on a table member which is movable by a ram assembly between a first position wherein the sheet material can be held in the non-tensioned condition across the support frame, and a second position wherein the support frame is moved against the held sheet material to tension the latter and maintain engagement between the sheet material and the support frame.

3. Apparatus according to Claim 2, wherein the ram assembly is located centrally of the table member at the side thereof remote from the location of the support frame.

4. Apparatus according to Claim 2 or 3,

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. extending tube 21 which is slidable on an upwardly extending guide rod 22 on the frame structure 10 to retain the bar 20 horizontal. On its upper face the bar 20 has friction means secured thereto, for example a layer of a friction material such as rubber. At the upper end of the frame structure 10 gripping means is provided at each side above the respective bar 20 in the form of an elongate belt 24 formed of a friction material, for example rubber, which belt is attached to a lower face of a frame member extending horizontally of the structure 10. Centrally within the frame structure 10 a main hydraulic ram assembly 26 extends vertically having its cylinder 28 mounted at its lower end on a support 30 and its ram 32 mounting at its upper end a table member 34 which is of rectangular configuration. The table member 34 has a bar 36 on its upper surface extending centrally of the table member 34 parallel to one pair of opposed sides thereof. The hydraulic rams 18, 32 are controlled from a common hydraulic power pack by means of appropriate controls (not shown), each pair of opposed rams 18 being operable together, and the ram 26 being individually operable, from an appropriate control console (not shown). Hydraulic check valves are provided for retaining the respective rams in their extended positions as necessary and preventing the rams from creeping down under pressure when the power pack is turned off. In use, with the rams 18, 32 in a first non-operative position, four open-ended rectangular support frames 38 are positioned on the table member 34, each of the frames 38 having an edge resting on the bar 36 such that the frame is in an inclined position on the table member 34. A material, for example nylon, is laid across the upper end of the apparatus above the frames 38 with the edges of the sheet material passing under the belts 24. The rams 18 are then extended in opposed pairs such that the bars 20 are moved upwardly to clamp the respective edges of the sheet material against the belts 24. When the material is clamped in position the ram 32 is then extended to move the table member 34, with the frames 38, upwardly against the sheet material thus tensioning the latter and bringing the frames into intimate engagement with the tensioned material by virtue of the inclination of the frames 38. To prevent any rotation of the table member 34 vertically extending tubes 40 are connected at their upper ends to the underside of the table member 34 and are slidable in vertical guide rods 42 which are connected at their lower ends to the support 30. When the desired tension has been applied to the material, as can be determined from the applied hydraulic pressure, the material can be secured to the frames 38 by any suitable means, for example by applying glue through the material along the edges of the frame 38, and the hydraulic check valves enable the rams 18, 32 to retain the frames 38 in such contact with the sheet material as necessary. Once the material is permanently secured to the frames 38 the material can be cut around the latter to provide four screens for use in screen printing. The rams 18, 32 are retracted and the apparatus is then ready for re-use. In a modification, the gripping means on the frame structure may comprise a strip of friction material retained in a complementary groove in a respective member of the frame structure at each side thereof. The respective bar is then preferably profiled to clamp the material against this strip. This apparatus is therefore extremely quick and easy to operate and in addition is reliable and relatively simple to service and repair if necessary. Various modifications may be made without departing from the invention. For example it is envisaged that the apparatus may be pneumatically operated and also the frame structure may be of a configuration other than that shown with the table member being adapted to support any suitable number of frames. Also the components of the guide arrangements 21, 22 and 40, 42 can be arranged and indeed any other suitable guide arrangement can be utilised. WHAT I CLAIM IS:

1. Apparatus for tensioning a sheet material and enabling application of the material to a support frame, said apparatus comprising means for holding the sheet material in a non-tensioned condition, and means for tensioning the sheet material and maintaining same in engagement with a support frame for securing thereto while in a tensioned condition, the means for holding and tensioning the sheet material being controlled by fluid media.

4. Apparatus according to Claim 2 or 3,

wherein the table member is retained in its second position by means of a check valve operatively connected with the ram assembly.

5. Apparatus according to any of Claims 2 to 4, wherein means are provided for preventing rotation of the table member.

6. Apparatus according to Claim 5, wherein the means for preventing rotation of the table member comprises a rod connected to one of the table member and a base structure of the apparatus, and a guide for the rod connected to the other of the table member and the base structure.

7. Apparatus according to any of Claims 2 to 6, wherein the table member is arranged to retain a plurality of support frames thereon.

8. Apparatus according to any of the preceding claims, wherein the means for holding the sheet material comprises a bar arrangement which is movable between a first non-clamping position and a second clamping position wherein a respective edge of the sheet material is clamped between the bar arrangement and gripper means on a frame structure of the apparatus.

9. Apparatus according to Claim 8, wherein the frame structure is of generally rectangular configuration and the bar arrangement comprises a bar located at each side of the frame structure and extending substantially parelled to the respective side, movement of each bar being controlled by a respective ram assembly.

10. Apparatus according to Claim 9, wherein means are provided for simultaneously operating each pair of opposed ram assemblies associated with the sheet material holding means.

11. Apparatus according to Claim 9 or 10, wherein each bar has guide means in the form of a rod connected to one of the bar and the frame structure and a guide for the rod connected to the other of the bar and the frame structure.

12. Apparatus according to any of Claims 8 to 11 wherein the gripper means comprises an elongate strip of friction material extending along each side of the frame structure on a member thereof for engagement by the respective bar arrangement when the latter is in its second position, so as to clamp the sheet material therebetween.

13. Apparatus according to any of the preceding claims, wherein the means for holding and tensioning the sheet material are hydraulically controlled.

14. Apparatus for tensioning a sheet material and enabling application of the material to a support frame, substantially as hereinbefore described with reference to the accompanying drawings.