| 摘要 |
A horizontal scrubbing brush for a vehicle-washing apparatus, vertically guided in lateral tracks on a portal frame, is suspended from two sets of cables, one set leading to a counterweight, the other being linked with a piston of a single-acting pneumatic cylinder which is pressurized to raise the brush and is cut off to let the brush descend under its own weight partly balanced by the counterweight. The piston head within the cylinder is provided with resilient peripheral lips which let the air escape slowly during the descent of the brush and also exert a braking action during its ascent.
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