Patent GB-846988-A (GB)
Title: Sewing machine attachment for spiral seams
IPC: D05B21/00
Filed: 1958-02-19
Abstract: 846,988. Sewing machines. ROSSA, E. D. Feb. 19, 1958 [Feb. 23, 1957], No. 5464/58. Class 112 Feed by clamps. In a sewing machine attachment for use in producing spiral seams and comprising a carriage movable in a path at right angles to the direction of normal work feed, means for anchoring the work to the carriage while permitting rotation of the work by the normal work-feeding means of the machine, and means for effecting movement of the carriage, a first arm is fixed to an oscillating shaft of the machine, a second arm is fixed to a shaft adapted on oscillation to effect movement of the carriage, and said arms are connected together by a rod articulated to sleeves carried by said arms, at least one sleeve being moved along its respective arm according to a predetermined law in order to vary the degree of oscillation of the second arm. A carriage 3 is slidably mounted in fixed guideways 2 and is formed with a depression 21a engagable by the pointed lower end 22 of a pivoted and telescopic presser bar, whereby the work can rotate about end 22 under the action of the usual feed dogs. A rotary screw 6 is engaged by a follower 8 mounted on the carriage to effect movement of the latter. A tube 12 projecting downwardly from the carriage contains a hollow plunger 10 biased upwardly by a spring 15. A rod 9 mounted in plunger 10 and biased downwardly by a spring 11 carries the follower 8. Plunger 10, when pressed downwardly, engages a notch 10b therein with a spring-biased catch 16 to hold the follower 8 in engagement with the screw 6. The latter is carried by a shaft 29 journalled in a fixed bracket 7, and shaft 29 is coupled by a one-way clutch 32 to a shaft 27 (not shown) journalled in a fixed bracket 35. A rod 26 fixed to shaft 27 has fixed thereto a sleeve 36 pivoted to one end of a link 25 the other end of which is pivoted to a sleeve 37 slidable on a rod 24 fixed to a feed rock shaft of the machine. Sleeve 37 is biased by a spring 41 into engagement with a cam structure 40 carried by a bracket 42a fixed to a rod .42 slidable in bearings 43 on bracket 7. Rod 42 is rigidly connected by a sleeve 65 and a rod 64 to tube 12, whereby the cam structure 40 moves linearly with the carriage 3. The angular movement imparted to rod 26, and hence the rate of feed of the carriage, will be governed by the formation of cam 40 which establishes the position of sleeve 37 on rod 24. Presser bars and feet. The presser bar comprises a tube 45 pivoted to a bracket 47 on the head of the machine and containing a rod 44 biased upwardly by a spring 52. A nose 55a on a double-armed lever 55 pivoted at 56 on tube 45 is adapted to engage a collar 53 on rod 44 to hold the latter in a depressed position, wherein the pointed pin 22, carried by a plunger 49 slidable in a socket 48 mounted on the lower end of rod 44, engages the depression 21a in the carriage 3. A crosspin 51 on rod 44 is engaged in slots 48a formed in socket 48, and a compression spring 50 is interposed between plunger 49 and rod 44. When the carriage reaches a limiting position at the end of stitching, the upper end of lever 55 engages an abutment 58 on bracket 47, whereby nose 55a is withdrawn from collar 53 and rod 44 rises to release the work.