Patent GB-312946-A (GB)
Title: Improvements in or relating to copying lathes
IPC: B23Q35/10
Filed: 1927-12-03
Abstract: 312,946. British United Shoe Machinery Co., Ltd., (United Shoe Machinery Corporation). Dec. 3, 1927. Lathes.-In a lathe for producing lasts for boots or shoes, the model and work are carried by a swing frame having a short radius and a small moment of inertia, the driving gearing for the work and model spindles and the proportions of the frame being so arranged that the proper relations between the model and its copying roller are maintained and exact reproduction is possible in spite of the short radius of the frame. Length grading mechanism is also provided which is capable of being varied manually during a traverse of the cutter along the work so as to reproduce different longitudinal portions of the model to different scales, and width grading is provided which may be controlled automatically to vary the scale of girth measurements cyclically during each rotation of the work and model. A machine for making last parts such as those described in Specification 205,839, [Class 17 (i), Boots and shoes, Apparatus for making &c.], as distinct from complete lasts, comprises a bed having V-guides 12, 14, Fig. 2, and a flat guide 16, upon which are mounted the cutter slide 20, the copying roller slide 18 and an intermediate slide 22. The slides 20, 22 are traversed to and from each other during cutting by a right and left handed screw 24 rotated by skew gearing 28, worm gearing 32 and a belt drive 36 from the main shaft 38 of the machine which is itself rotated by a belt 40 and an intermediate shaft from a motor. The slide 18 is connected to the slide 22 by the length grading mechanism. The swing frame comprises a heavy square bar 48, Figs. 2 and 11, mounted by trunnions 49 in bearings 46 on the machine frame and carrying a central adjustable bracket 50 supporting a driving shaft 56 for the work and model face-plates 58, 60 respectively. The two face-plates are rigidly connected to the single driving shaft 56 to eliminate differential backlash between the driving gears of the face-plates due to unequal presures between the model and copying roller. The shaft 56 is driven from the main shaft 38 through gearing 84 - - 88, Fig. 4 and a gear 90 rotatable about the axis of the swing frame 48. 'The gear 90 drives a gear 92 whose shaft 94, Figs. 4 and 11, carries two gears 96, 100. engaging gears 98, 102 on the tailstock and headstock spindles respectively. The tailstock centres 80, 82 do not drive the work but are rotated solely to prevent wear on the model and work. In a modification, the work centre 82 is stationary and the shaft 94 terminates in the gear casing 52. The gear casings may be made of aluminium and approximately half of the mass of the swing frame is concentrated in the bar 48 to reduce its moment of inertia. The gears 90, 92 are equal in size and the gears 96, 100 are each half the size of the gears 98, 102 and the centre of the bar 48 is equidistant from the axis of the model roller 104 in its normal position and the axis of rotation of the model and work, so that as the frame 48, 80, Fig. 10, oscillates during cutting, the gear 92 will roll round the gear 90 and cause a radial line 106<1> on the model, passing through the axis 103 of the model roller, always to pass through this axis as shown by the line 106". The radius 106<1> on the model will thus rotate (assuming the driving gear 90 to be stationary) at half the angular velocity of the swing frame. The centres 80, 82 are carried by tailstocks 72, 74 movable along the bar 48 to grip the model and work by screws 76, 78 which are locked by wing nuts 79. Lathe centres and drivers.-Plates 330, Figs. 13 and 14, provided with four tapped holes 332, may be mounted on the tailstocks and the holes are so arranged that by rotating and reversing the plates they may be made to occupy any of the positions shown by the corresponding marks in Fig. 14 (i.e. the four dots, the four X's &c.) Thus, a centre 80, inserted in one of the tapped holes, may be made to occupy any one of the sixteen positions shown in Fig. 14. The faceplates 58, 60 are provided with cross keys 64 for engaging recesses in driving dogs 66 which are attached by screws and are shaped with joint surfaces 250 corresponding to the joint surfaces of the last part 68 and model 70. Studs 71 on the dogs pass through an intervening plate and engage the last parts. Width-grading mechanism.-The copying roller 104 is carried by a grading slide 106, Figs. 2 and 4, movable transversely of the axis of rotation of the work on the slide 18. Grading is effected by a link 108, pivoted at 110 to the slide and carrying at its rear end a roller 112 engaging a fan board 114 which is pivoted at 116 and has an arcuate surface with the pivot 110 as centre. The fan board is oscillated by a link 118 connecting it to the swing frame 48. A link 136 pivoted to the link 108, is pivoted at its lower end to a block 134 slidable along an arcuate slot 130 in a member pivoted at 132 and having an arm 128 carrying a roller 126 which is kept in engagement with a cam 124 by a spring 129. The block 134 is movable along the arcuate slot by a link 138 pivoted to the block and to an arm 139 on a toothed segment 140 which may be oscillated bv a worm shaft 144 and a handle 146. The cam is rotated by gearing 122 from the main shaft 38 at the same speed as the model and work and is so arranged that the width grading may be varied during each rotation of the work. This operation is described in Specification 312,978. To enable the grading to be continuously controlled by the operator the slide 18 is provided with an apron 206, Fig. 15 on which is mounted a shaft 208 geared at 210 to the handoperated shaft 144 and at 214 to a lever 212 pivoted at 213 and carrying a pointer 216. A chart 234 is pinned to the machine frame by pins 242 and with the aid of setting scales, is inscribed with a curve such as 232. As the slide 18 is traversed along the model the pointer 216 is maintained in contact with the curve, and in this way work may be produced having portions of its length identical in girth measurements with the pattern and other portions' graded to different extents. A scale 147 indicates the width grading determined by the handle 146. In order to maintain the axis of the copying roller in the grading plane (i.e. the plane containing the axes of the work and the cutter, spindle, and represented in two consecutive positions by lines 106<1>, 106<11> in Fig. 10) the roller 104, Fig. 4, is carried by a lever 150 pivoted at 148 to the grading slide 106, and is oscillated at half the angular velocity of the frame, since the line 106<1> rotates at half the speed of the frame 48, 80. The rear end of the lever 150 has pivoted thereto a slide 152 engaged by a guide 156 pivoted at 154 on the slide 18. the guide being attached to an arm 158 connected by a link 160 to a. longitudinal rod 162 on the fan board. A strap 164 steadies the link 160. The centre 103 of the copying roller is situated out of the vertical plane passing through the axis' of rotation of the frame in order to diminish errors in copying. The cutter 165, Fig. 2, which is directly driven by a motor, is mounted at an angle of about 30‹ to the axis of rotation of the work similarly to that described in Specification 147,919 and in order to compensate for the similar inclination of the copying roller 104 a parallel motion linkage 166, 167, Fig. 4, is provided which maintains the axis' of the roller in a horizontal plane throughout the movements of the lever 150. The proportions of the width grading mechanism 138, 139, &c., are so arranged that equal divisions on the chart scale give equal increments in the girth of the last part produced. Length-grading mechanism. For hand control of the length grading mechanism a block 200, Fig. 15, is adjustable on the intermediate slide 22 by means of a screw 202 and carries the pivot of a link 226 whose other end is connected to an arm 228 of a three-armed lever pivoted to the slide 18 at 219. The second arm has a geared connection 222 with a hand wheel 229 and the third arm 218 carries a pointer 220. The movements of the slide 22 are accordingly communicated ta the slide 18 in greater or less amounts as the hand wheel 229 is rotated, such rotation being performed by the operator in accordance with a curve 230 inscribed on the chart 234. The length-grading may thus be varied throughout the length of the work, similarly to the width-grading. For automatic length-grading, the block 200 carries an inclined bar 198, Fig. 1, provided with four studs 204, any one of which may be connected by a link 192 to a corresponding stud 196 on the grading lever 190 pivoted to the model slide 18. Alteration of the position of the link 192 alters the amount of length grading and the operation is then similar to that of the usual grading mechanism. Spindles.-Mechanism is provided for stopping the rotation of the model and work driving shaft 56 in a definite angular position to facilitate removal and insertion of the work, and comprises a bell crank lever 169, Figs. 1-3, having two notches of which one engages a pin 170 on the end of the swing frame 48 and the other engages a finger 174 on a link 176. When the swing frame is pulled back by the operator, the lever 169 is rocked and the link 176 oscillates a second bell crank 178 which has pivoted thereto a square bar 181 provided with a bevel 182. The bevel is thus brought into contact with a laterally sliding clutch connecting the driving pulley 40 to the main shaft 38 and remains in this position until it is rocked by a cam 186, rotated from the shaft 38 at the same speed as the shaft 56, to throw the clutch completely. The feed for the slides 20, 22 is stopped by tripping out the worm 188, Fig. 1, in known manner.