| 摘要 |
A stretch frame for sheet material such as printing screen utilizes tensioning rollers to be secured to the sheet edges and then rotated to stress the sheet material. The rollers may be rotatably received within laterally opening channels in the frame and restrained against reverse rotation to release the sheet tension by a ratchet device extending along a substantial length of each roller. This construction insures that the printing screen or other web shaped material is rigidly held in place.
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