| 摘要 |
A device for dispensing solid material from a tube having a longitudinally displaceable internal piston moved by an externally operated spindle threading through the piston. At its base the spindle has a narrowed, non-threaded region, such that when the piston is fully withdrawn into the tube, the threads of the spindle and piston slip if the spindle continues to be rotated. To prevent the piston threads from completely disengaging the spindle threads, the spindle's non-threaded region is shorter than the piston's internal threads. In this way, the spindle will not break even if it continues to be rotated after the piston is fully withdrawn into the tube, yet it readily engages the piston threads when turned in the opposite direction to displace the piston towards the dispensing end of the tube. Thus the device as a whole remains reliably usable. |
