| 摘要 |
772,397. Sewing machines. SINGER MANUFACTURING CO. Aug. 3, 1955 [Aug. 9, 1954], No. 22279/55. Class 112. [Also in Group XXIV] In a zig-zag sewing machine as described in Specification 754,629, in which a main shaft is geared to a cross shaft 44 carrying a rotary pattern cam which co-operates with a follower to effect vibration of a needlecarrying frame, a pattern member carried by shaft 44 is such that the latter makes a plurality of revolutions during each complete cycle of operations of the pattern member. In Fig. 2 a frame 47 is formed at one end with a sleeve 52 which fits over an extension 58 of shaft 44 and is secured thereto by a thumb screw 59. Journalled on sleeve 52 is a sprocket 50 coupled to shaft 44 by means of a pin 55 extending from a flange 56 on said shaft. The other end of the frame carries a stud 53 on which a sprocket 51 is freely journalled. A pin 61 also carried by the frame is engaged by a spring clip 60 carried by the machine frame. An endless belt 48, carried by sprockets 50, 51 is formed on its inner surface with cleats 49 which enter recesses provided in the sprockets, and on its outer surface with cam lobes which co-operate with a follower 34. In a modification sprocket 51 is omitted and frame 47 is shortened so as only to cover sprocket 50. The belt then hangs freely from the latter and may be of any desired length. In a further modification, Fig. 7, a drum 63 fits on the extension 58, is secured thereto by a thumbscrew 64, and is coupled to shaft 44 by means of pin 55. The periphery of the drum is formed with a raised endless cam track 65 formed with a series of cam lobes 66. The cam follower comprises a tubular member 67 housing a slider 68 having a depending follower-pin 69 on which is slidably mounted a shoe 70 which embraces the cam track and is held in engagement therewith by a spring 71, member 67 also being spring-biased towards the drum to maintain pin 69 in engagement with the cam track. The drum, as shown, makes three complete revolutions before the stitch pattern is repeated. |
