Patent GB-808086-A (GB)
Title: Improvements relating to screw-cutting machines or screw-cutting attachments for machines
IPC: B23G1/16
Filed: 1956-08-24
Abstract: 808,086. Screw-cutting machines and attachments. LITTLE Inc., A. D. Aug. 24, 1956 [Feb. 14, 1956], No. 25877/56. Class 83 (3). [Also in Group XXIV] A screw-cutting machine or attachment for taps T, dies &c. comprises a reversible-drive 15, 20, 32 for a lead-screw 44 which feeds the chuck 90 through a linkage 100-105, 115, in which the effective length of the two-part link 100, 105 is adjustable to vary the rate of feed, and adjustable means 118 for restraining the movement of the link 100, 105, to provide a uniform rate of feed for the chuck. The toothed housing 15 in the attachment 1-3 is driven clockwise by the spindle 10 of the drilling- machine on which the attachment is secured. by a clamp 6, the housing 20 being driven anticlockwise from the housing 15, at a higher speed through gears 24, 26, 28 and a gear 30 attached to the casing 20. A carrier-shaft 18, on which T-links 32 are pivoted, is raised or lowered by a hand lever 56 to expand an upper or a lower annular clutch shoe 34, 35, mounted on the links 32, into driving-engagement with housing 15 or housing 20, and thus drive the shaft, which is splined within the lead-screw 44. A spring 36, opposing a spring 54 acting on the lever 56, Fig. 3, normally supports the shoes in the neutral position, but the spring 54 may be adjusted by a screw 55 to bias the shoes 35 against the housing 20, thus engaging the drive for withdrawing a tap &c. The lever 56 is mounted on a pivot 52 and is also pivotally connected to a housing 45 for a bearing 46, located in the housing and on the shaft 18 by rings 48. The chuck 90, on a spindle 78 splined in the lead-screw 44, beneath the shaft 18, is guided by a slide 84 with opposite shoulders 85 in guideways 76 between depending fingers 74 on the casing of the attachment. A cammember 94, 95 on the slide returns the hand lever 56 to its neutral setting n, or the reverse setting r, from the forward feed setting o by engaging an adjustable feed-determining nut 60 on a screw 58 rigid with the lever 56. The same function is also performed by an upstanding member 71, on the feed-nut 65, which contacts the bearing housing 45 when the nut is at the. end of its travel. Movement of the lever in the opposite direction, from the reverse setting to the neutral position, is effected when the returning chuck-spindle 78 engages the spindles 18: The linkage for feeding the chuck faster, or slower than the traversing-speed of the hut comprises three interconnected swinging links 118, 100-105, 115 at the front of the attachment, and at the back a mirror-image arrangement of the links, the links 115 being joined at 117 and the parts 100 of the two-part links 100-105 at 125, 126. The links 118 are pivoted at their upper ends e to quadrants 124 clamped by screws 132 to the attachment, and at their lower ends d to the parts 100 of the two-part links 100-105. The links 100-105 pivot at a on pins 101 fixed to the parts 100 and bear in shoulders 68, on the feed-nut housing 66; guided in slots 70 in the casing of the attachment. The parts 105 are pivoted at b to the links 115, which are pivoted at their lower ends at c to the shoulders 85 of the slide 84. One of a pair of holes 108 in each part 105 is aligned by an index-pin 110 with one hole of two rows of holes 102 in the corresponding part 100, and the parts are clamped together by screws 112 passing through slots 106 in the parts 105 into one of three holes in each part 100. Interfitting sliding, surfaces may be provided on the parts 100, 105. For the setting of the links 100-105 with the centre b disposed on the opposite side of the point a to that of point d, illustrated in Fig. 3, the chuck 90 is moved faster than the feed-nut 65. Slower movements than those of the nut are produced by adjusting the length of each link 100-105 to move both points b, d to the same side of the point a, as in Fig. 4, a corresponding adjustment of the pivot-point e of the links 118 being effected by re-positioning the pivoted sectors 124 and clamping them by screws 132 engaging graduated slots 130 in the sectors.