Claims
- 1. A device for stretching a fabric upon a frame for use in a screen printing machine, comprising a support; a fluid-operated motor having a cylinder, a piston rod reciprocably extending into said cylinder, and means for moving said piston rod in at least one direction to draw the piston rod into said cylinder; means for securing said motor to said support; tongs carried by and reciprocable with said piston rod and including first and second fabric-engaging jaws; and means for mounting said tongs for automatic alignment with a force on fabric engaged by said jaws, including an universal joint between said piston rod and said tongs.
- 2. The device of claim 1, wherein said support defines a supporting surface and said cylinder includes a first end portion from which said piston rod extends and a second end portion, said securing means being located at the second end portion of said cylinder and defining for said motor a pivot axis which is substantially normal to said piston rod and is substantially parallel to said supporting surface.
- 3. The device of claim 1, wherein said piston rod is reciprocable between an extended position and a retracted position; and further comprising a base which supports said tongs in the extended position of said piston rod.
- 4. The device of claim 3, wherein said base is rigid with said support.
- 5. The device of claim 4, wherein said support includes a supporting surface and said base has a top surface including a portion which slopes toward said supporting surface in a direction toward said cylinder.
- 6. The device of claim 3, wherein said base and said tongs have confronting surfaces including means for guiding and centering said tongs during movement of said piston rod to said extended position.
- 7. The device of claim 1, wherein said first jaw includes a first fabric-engaging portion having a first elasticity and said second jaw includes a second fabric-engaging portion having a greater second elasticity.
- 8. The device of claim 7, further comprising means for opening and closing said tongs, said first fabric-engaging portion comprising at least one projection which deforms said second fabric-engaging portion in response to closing of said tongs.
- 9. The device of claim 8, wherein said at least one projection comprises an elongated rib.
- 10. The device of claim 1, wherein each of said jaws has two substantially parallel lateral marginal portions which make oblique angles with the axis of said piston rod.
- 11. The device of claim 1, wherein said support includes a frame carrier, said piston rod being reciprocable between an extended and a retracted position and said tongs being located between said securing means and said carrier in the extended position of said piston rod.
- 12. The device of claim 11, wherein said carrier includes means for locating a frame preparatory to stretching of a fabric by said jaws in response to movement of said piston rod toward said retracted position.
- 13. The device of claim 11, further comprising a mobile second frame carrier and means for releasably affixing said second carrier to said support in a selected position relative to the carrier of said support.
- 14. The device of claim 11, wherein said support has an underside and said carrier includes means for locating a frame preparatory to stretching of a fabric over an upper side of the frame which engages said locating means at a first distance from said underside; and further comprising a base which supports said tongs in the extended position of said piston rod, and means for closing and opening said tongs by moving at least one of said jaws relative to the other jaw to and from a plane in which said jaws abut one another while said base supports said tongs, said plane being disposed at a lesser second distance from said underside.
- 15. The device of claim 1, wherein said piston rod is reciprocable between a retracted position and an extended position in which a fabric is insertable in said jaws preparatory to stretching of the fabric; and further comprising means for guiding said tongs during movement of said piston rod to said extended position so that, upon arrival of said piston rod at said extended position, said tongs assume a predetermined starting position for stretching of the fabric.
- 16. Apparatus for making stencils of the type having a frame and a stretched fabric mounted on said frame for controlled penetration by ink in a screen printing machine, comprising a holder having an upper side; and a plurality of stretching devices mounted at and surrounding a frame-receiving portion of said upper side, each of said devices comprising a support having an underside on said upper side, a fluid-operated motor having a cylinder, a piston rod reciprocably extending into said cylinder and means for moving said piston rod in at least one direction to draw the piston rod into said cylinder and away from said portion of said upper side, tongs carried by and reciprocable with said piston rod and including first and second fabric-engaging jaws, and means mounting of said tongs for automatic alignment with a force on fabric engaged by said jaws including a universal joint provided between said piston rod and said tongs.
- 17. The apparatus of claim 16, wherein said frame-receiving portion of said upper side is rectangular.
- 18. The apparatus of claim 16, wherein said stretching devices include at least two neighboring devices and the jaws of the tongs of said at least two neighboring devices have immediately adjacent lateral marginal portions.
- 19. The apparatus of claim 16, further comprising means for maintaining the supports of said stretching devices in predetermined positions with reference to said holder.
- 20. The apparatus of claim 16, wherein said devices form plural rows including two pairs of parallel rows.
- 21. The device of claim 16, wherein each of said tongs has two substantially parallel lateral marginal portions which make oblique angles with the axis of the respective piston rod, said stretching devices including two neighboring devices arranged such that a lateral marginal portion of the tongs of one of said neighboring devices is immediately adjacent a lateral marginal portion of the tongs of the other of said neighboring devices.
- 22. The device of claim 16, wherein each of said piston rods is reciprocable between a retracted position and an extended position in which a fabric is insertable in the respective jaws preparatory to stretching of the fabric, each of said devices further comprising means for guiding the respective tongs during movement of the respective piston rod to its extended position so that, upon arrival of a piston rod at its extended position, the respective tongs assume a predetermined starting position for stretching of the fabric.
Priority Claims (1)
Number |
Date |
Country |
Kind |
02560/90 |
Aug 1990 |
CHX |
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CROSS-REFERENCE TO RELATED APPLICATION
This is a continuation of commonly owned patent application Ser. No. 07/738,466 filed Jul. 31, 1991, now abandoned.
US Referenced Citations (5)
Continuations (1)
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Number |
Date |
Country |
Parent |
738466 |
Jul 1991 |
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