| 摘要 |
In one embodiment, the subject invention includes a frame 10 comprising a front plate, a rear plate, a generally circular passage which extends through the frame, and rollers arranged, circumferentially positioned about the passage. The rollers are suspended within the passage by an adjustable arm which is mounted to the frame on one end, and is rotatably coupled to a roller on an opposite end. The adjustable arm includes a threaded rod that is rotatably mounted to a plate by a mounting plate and extension 18 which engages the rod and which travels longitudinally along the rod.
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