Patent GB-804634-A (GB)
Title: Improvements in sewing machines
IPC: D05B29/06
Filed: 1956-03-09
Abstract: 804,634. Sewing machines. UNION SPECIAL MASCHINENFABRIK G.m.b.H. March 9, 1956 [March 12, 1955], No. 7391/56. Class 112 [Also in Groups VIII and XXIV] Stitch forming. In an overedge sewing machine a curved needle, an under looper and an overedge looper are mounted for oscillation in planes perpendicular to the line of stitch formation about respective fixfied axles, and are operatively connected to a rotary driving shaft. The needle 8 is carried by an arm 9 fixed to a shaft 10. The under looper 11 is carried by an. arm 13 fixed to a shaft 15, and the overedge looper 12 is carried by an arm 14 fixed to a shaft 16. The driving shaft 17 is provided with cranks 20, 21, 22 connected by respective pitmans 24, 27, 28 to arms 23, 25, 26 fixed to the shafts 10, 15, 16. The threads pass through a guide plate 82 to disc-type tensioners 79, the needle thread N then pass ing through eyelets 84, 89, the overedge looper thread O through eyelets 85, 87 and the underedge looper thread U through eyelets 86, 92. Pins 89, 93, fixed to the needle-carrying arm 9, co-operate with members 88, 90, 91 to effect a take-up action in the respective threads. Connecting upper and lower shafts. A gear wheel 29 on the driving shaft 17 meshes with a gear wheel 30 on the lower shaft 31. Feeding, lifting presser bar, controlling thread tension. A main feed dog 38 and differential feed doog 39 are respectively carried by arms 37, 36 operated by eccentrics 133, 132 on shaft 31 to impart feed-lift movement to the feed dogs. Links 44, 45 respectively connecting arms 36, 37 to a pivot bolt 43, radially adjustable on a head 41 provided on shaft 17, impart feed-advance movement to the feed dogs, the eccentricity of bolt 43 determining the stitch length. The pivotal connection between link 44 and arm 36 lies in an arcuate slot 36a, and is connected by a link 51 to an arm 52 pivotally mounted at 53. Arm 52 is biased upwardly by a spring 55 and may be drawn downwardly by a chain 57 to increase the differential effect, a lug 52a on arm 52 moving between adjustable stop screws 58, 59 in a slot 60 over a scale 61 to indicate the degree of differential action. The presser foot 64 is carried by an arm 65 pivotally mounted at 66 and biased downwardly by the forked end of a pin 69 loaded by a spring 69a. An extension 65a of arm 65 overlies an arm 70a fixed to one end of a shaft 71. A spring 74 acts on shaft 71 to bias arm 70a away from extension. 65a, the movement being limited by means of a stud 75 which is screwed into a fixed lug 67a and the head of which overlies a lug formed on an arm 72 fixed to the other end of shaft 71. The latter may be turned, by means of a chain 73 attached to arm 72, for engaging arm 70a with extension 65a to lift the presser foot. The amount of lifting is limited by means of a stud 77 which screws into arm 72 and which engages lug 67a, said amount being so adjusted as to decrease the period of engagement of the feed dogs with the work in order to shorten the stitch length when the presser foot is raised at the beginning and end of a seam. The thread tension is simultaneously increased for tightening the shortened stitches by means comprising an arm 70b fixed to shaft 71 and pivoted at 70c to bar 78 slidably arranged behind the thread tensioning discs 79, bar 78 being thereby moved along wedge surfaces 81 to displace the tensioning discs against their springs 80. Cutting. The head 41 of shaft 17 is formed with an eccentric 46, connected by a pitman 47 to an arm 48. The latter is pivotally mounted at one end and carries at its other end a cutting blade adapted to cooperate with a fixed blade for edge-trimming the work. The pivot of arm 48 is resiliently displaceable in the axial direction to allow slight separation to occur between the blades. Means are also provided to prevent said axial displacement when heavy material is being operated upon. Driving. A V-pulley 106, journalled by a ball bearing 108 to be rotated continuously on shaft 17, provides one half of a friction coupling for driving shaft 17, the other half being provided by a member 109 splined on shaft 17. A cylindrical member 124 journalled by a ball bearing 112 to rotate on the hub of member 109 and restrained from axial movement relative to the latter, is engaged by pins 122 at the ends of a forked member 121 fixed to a shaft 120. An arm 115 fixed to the latter is biased by a spring 113 to separate the coupling members against the bias of a spring 110 interposed between a handwheel 107 and the bearing 112. A chain 116 carried by arm 115 serves to rock shaft 120 for shifting member 109 into engagement with member 106. On release of the chain, member 109 moves into engagement with a fixed member 118 to brake shaft 17. Frames, lubrication. The machine casing 1 is formed with walls 104, 105 supporting the bearings 18, 19 for the driving shaft 17, and forming with a detachable cover 2 and detachable baseplate 3 an oil-tight chamber enclosing the eccentrics 20, 21, 22 and gear wheels 29, 30. The base plate is formed with perforated, lugs. which engage pins 7 projecting from rubber cushions 6. The needle arm 9, the thread take-up members 89, 93 and the thread tensioners 79 are enclosed by a hinged cover 83. The bearings 18, 19 are lubricated by wicks 135, 136 and the bearings 32, 33, 34 of shaft 31 by wicks 134, 131, 130, all of which wicks dip into an oil sump 138. Oil from bearings 17, 33, 34 is pumped by means of spiral grooves formed in the respective journals to the shaft head 41, eccentric 133 and eccentric 132 respectively. Oil dripping from the external moving parts, such as the work-feed and edgetrimming mechanisms, is returned to the sump 138 through a filter screen 137. Cooling. A fan wheel 126, fixed to the continuously rotating member 106, forces air through a duct provided in the rear wall of the machine casing. The inner wall of said duct is provided with pins arranged stepwise to afford a cooling surface for oil thrown thereupon by the gear wheels 29,' 30.