Patent GB-1222420-A (GB)
Title: Improvements relating to sewing machines
IPC: D05B3/08
Filed: 1968-09-19
Abstract: 1,222,420. Serving machine. DURKOPPWERKE G.m.b.H. 19 Sept., 1968 [26 Sept., 1967], No. 44483/68. Heading D1G. A buttonhole sewing machine has an upper structure comprising a base 2, Standard 3 and upper arm 4 pivoted at 2' to a support 1, whereby the upper structure can be swung upwardly to expose mechanism under the base 2. The upper arm shaft 5 is driven by a pulley 19 via a belt 16 shiftable by a rod 17 to either a fast-running pulley 12 rigid with a driving pulley 13 or to a slow-running pulley 14 rigid with a driving pulley of greater diameter than pulley 13. Pulley 19 is rotatably and slidably mounted on shaft 5 by needle bearings 20. A non-rotating disc 38 is interposed between a thrust ball bearing 39 abutting bearing 20 and a coverplate 41 rigid with pulley 19, and is rigid with a fork 37 pivoted at 43 to one arm 32 of a double-armed lever pivoted at 25 to a fixed bracket 25. Counterclockwise movement of arm 32 thereby serves to couple pulley 19 drivingly to a friction disc 21 secured by screws 22 to a stop arm disc 23 keyed to shaft 5. Clockwise movement of arm 32 disengages pulley 19 from disc 21. The other arm 31 of said ball crank is formed with a base 54 slidably housing a bolt 55 which is biased out-, wards by a spring 56 and is pivoted at 58 to a plate 57 carrying a roller 64 engaged in a fork 63 on a starting-and-stopping plunger 30 slidably mounted in a fixed housing 26. The lower end of plunger 30 is pivoted at 42 to a; lever 43 pivoted at 45 to the machine frame. A spring 44 biases lever 43 clockwise to shift plunger 30 upwardly into engagement with a notch 23' in cam disc 23, plunger 3 being held in the raised position by the engagement of a notch 49 formed therein with a resilient arm 47 pivoted at 48 to lever arm 31, the latch then being moved clockwise by spring means to disengage pulley 19 from disc 21. To start the machine, a lever 150 is raised for engaging a slidable rod 46 with an abutment 50 on lever 50 to move the latter counterclockwise. Plunger 30 is thereby moved downwards to disengage from notch 23', arm 47 is cammed out of notch 49 and is moved by a torsion spring 52 into engagement with a fixed abutment 51, and a sloping edge on plate 57 is engaged with a fixed roller 60, whereof plate 57 turns clockwise about rollers 64 to impart counterclockwise movement to arm 31 for engaging pulley 19 with disc 21. The member is then driven at high speed from pulley 12 >  Plunger 30 is held in the lowered position by engagement of a notch 66 formed thereon with a lug 67 on a lever arm 68 pivoted at 70 to the machine frame and biased clockwise by a torsion spring 71. The stitch pattern is governed by a control cam disc 9 journalled at 29 and driven from draft 5 by variable speed gearing.At the end of stitching cycle belt 16 is shifted to pulley 14 to drive the machine at low speed and thereafter when shaft 5 has rotated a predetermined number of times, plunger 30 is released to stop the machine while belt 16 is returned to pulley 12. A worm 80 and a cam 81, spaced therefrom are rigid with shaft 5. A rocker 82, slidable on a shaft 83 parallel with shaft 5, is drawn to one end portion abutting a fixed stop 90 of a spring 87. A spring 86 acting on one arm 82" of rocker 82, biases the latter counterclockwise to engage the other arm 82' with a fixed plate 88, when a tooth 84, slidable in arm 82' against the bias of a spring 84', is raised from worm 80, and the nose of a pawl 118, pivoted at 119 to arm 82' and biased clockwise by a spring (120) projects through the wide end portion of a slot formed in plate 88. A pin 113 on arm 82' is engaged by a nose 1l2 on an arm 112 pivoted at 111 'to one arm 109 of a three-armed lever pivoted at 100 to the machine frame. A second arm 101 is biased clockwise by a spring 103 into engagement with a fixed abutment 104 to raise arm 112 and to separate a roller 102 an arm 101 from a crank arm 114 on one end of a pivoted shaft 116 having at its other end a crank arm 117 connected to rod 17, whereby a torsion spring 114 acting in shaft 116 series to shaft belt 16 to pulley 12. A third arm of said lever journals a crank pin on a crank plate 107 carrying a second crank pin engaged in a slot formed in an arm 98 pivoted at 97 to a lever 94 which is pivoted at 93 to the machine frame and is biased counterclockwise by a spring 96 to engage a follower arm 95 thereon with a portion of cam disc 9. Near the end of the stitching cycle, nose 95 rides up a cam lobe 92, whereby bar 98 moves rightwards to turn plate 107 for straightening a toggle joint between bar 98 and the said third arm. When nose 95 subsequently disengages from came lobe 92 the three arm lever rocks counterclockwise with lever 94 to engage roller 102 with arm 114 for shifting belt 16 to the slow running belt 14, while arm 112 is drawn downwardly, whereby nose 112' acts on pin 113 to move rocker 82 clockwise for engaging tooth 84 with worm 80. Rocker 82 thereby begins to move axially on shaft 83. The nose of pawl 118 instantly pivots freely in the wider portion of the slot in plate 88, and on axial movement of rocker 82 is cammed downwards at a narrowed part of said slot to engage the under surface of plate 88. When tooth 84 nears the end of worm 80, a second nose on pawl 118 engages a fixed stud 121 and pin 113 disengages from nose 112' whereby the abutment of pawl 118 enters plate 88 and retains tooth 84 engaged with worm 80. After about five revolutions of draft 5 when tooth 84 reached the end of worm 80 cam 81 engages pawl 118 to turn the latter counterclockwise out of abutment with plate 88, where spring 86 turns rocker 82 counterclockwise to release tooth 84 from worm 80, cam 81 then releasing pawl 118 to allow the upstanding nose thereon to re-enter the slot in plate 88 and spring 87 restores rocker 82 to its initial end position. During the counterclockwise movement of rocker 82, a pin 75 projecting from arm 82" engages a lever arm 73 upstanding from lever arm 68 to turn the latter counterclockwise whereby lug 62 is disengaged from notch 66 to release the stopping plunger 30. During the upward movement of the latter a lever cam 124, which is pivoted on the machine frame and has one end engaged in a notch 124 formed in plunger 30 engages the free end of bar 98, whereby plate 107 turns for breaking the toggle joint and spring 103 thereby turns arm 101 to shift roller 102 away from arm 114 when spring 115 returns belt 16 to pulley 12.