| 摘要 |
759,249. Sewing machines. SINGER MANUFACTURING CO. Dec. 24, 1954 [Jan. 15, 1954], No. 37313/54. Class 112. In a four-motion feed mechanism the feed dog is connected to the feed-lift shaft by disengageable means which comprise a first member operated by the feed-lift shaft, a second member connected to the feed dog, a movable device carried by one of said members and movable into engagement with the other member, a spring engaging one end of the movable device, and means for compressing the spring and thereby connecting the movable device with said other member. The feed lift shaft 44 carries a crank arm 68 adapted to be releasably connected to a lever 53 which is journalled on shaft 44 and is coupled to a feed bar carrying the feed dog. When the lever s disconnected from the crank arm, a spring 57 rotates the lever to lower the feed dog into an inoperative position. A rod 201 is screwed at one end into the crank arm and passes through a flared hole 66 in the lever, the other end of the rod having a cylindrical head 205 carrying a radial pin 207 which engages in a spiral cam slot 212 formed in a sleeve 208 mounted on head 205. A sleeve 216 having a domed head 217 is slidably mounted on rod 201 and is interposed between a strong spring 214 and a weak spring 222. Rotation of sleeve 208 in one direction, by means of a handle 209, serves to compress spring 214 and thereby urge head 217 into hole 66 for connecting the lever to the crank arm. Rotation of sleeve 208 in the opposite direction releases spring 214 to allow spring 222 to expel head 217 from hole 66. Specification 721,003 is referred to. |
