Patent GB-810127-A (GB)
Title: Improvements in or relating to lapping apparatus
IPC: B24B37/10
Filed: 1955-12-09
Abstract: 810,127. Lapping. CRANE PACKING CO. Dec. 9, 1955 [Dec. 10, 1954], No. 35511/55. Class 60. An article comprising an annular surface on a shoulder concentric with and between a lower stem portion and an upper cylindrical portion, has the annular surface lapped by a rotatable lap plate having an annular groove providing land portions on opposite sides thereof, the annular surface resting on the land portions and bridging the distance between them, and the stem portion extending into the groove ; means for restraining the article against revolution about the rotational axis of the lap plate while permitting rotation of the article about its own axis comprises an antifriction roller supported from the machine framework above the plane of the surface of the lap plate and positioned in the normal path of movement of the article, the antifriction roller having running engagement with the cylindrical surface on the article and being so positioned as to bear against the cylindrical surface so as to hold the article against circumferential movement on the lap plate and bias the article so that the stem portion bears against one side of the groove in rolling engagement therewith to induce rotation of the article about its own axis. A lapping machine comprises a frame 10 with a table top 12 having a circular opening 16 through which projects a rotatable lap plate 18, e.g. of cast iron formed with circumferential grooves 22 separating land areas 24. Conditioning rings 26 rest on the annular lap surface 20 slightly overlapping its inner and outer peripheries. Each ring 26 has secured thereto a yoke 32 with a hub portion 36 loosely surrounding a spindle 38 connected at its upper end with a spindle 42. The ring 26 is urged against the lap plate by a spring 43 reacting against a collar 45 adjustably secured on the spindle 38 by set screw 47. A limited amount of universal movement is permitted between the ring 26 and the spindle 38 so that the ring will rest squarely upon the lap plate in face-to-face contact with the land areas 24. A series of spaced angularly disposed slots 49 formed in the lower region of the ring serves to distribute the lapping compound. The spindle 42 is clamped by set screw 62 in an eccentrically disposed bore 60 in a cylindrical block 56 rotatably mounted in a boss 54 at the end of an arm 48 of a spider 44 selectively secured in various positions of vertical adjustment to a housing 52 mounted on the table portion 12. The block 56 has a knurled head 59 and is secured in adjusted position by clamping screw 64; a scale 68 and pointer 66 are provided. The amount of overhang on the inner and outer peripheries of the annular lap surface is thus adjustable to correct the wear of the lap surface. A tank 70 for lapping compound contains an agitator mechanism the shaft 72 of which is driven through gearing 74 from an electric motor M ; the lapping compound flows through discharge orifice 78 controlled by solenoid actuated valve 80, and along flexible wire 82 bearing against the side of one of the conditioning rings 26. One type of workpiece A includes a central stem 90 carrying at its ends gears 92, 94 and having an intermediate disc element 96 the annular surface 98 of which is to be lapped ; to increase the effective lapping pressure a cylindrical weight 99 is positioned over the upper gear 92 and is formed with a socket 101 the wall of which has a groove 103 housing a resilient ring 155 which grips the teeth of the gear 92. Another type of workpiece A<SP>1</SP> has a body portion a, a stem portion b and a shoulder portion c which is to be lapped. Means to restrain the articles A, A<SP>1</SP> against revolution about the lap axis which permitting rotation about their own axes includes antifriction members or rollers 102, 104 positioned in the path of the articles and bearing against the body portion a or the weight 99. The lower end of the spindle 38 has a socket 106 in which is slidably and turnably mounted a clamping rod 108 the lower end of which receives a screw 110 having an enlarged head 112 and a washer 114. Between the washer 114 and the underneath surface 116 of the clamping rod 108 are the horizontal arm portions 120 of roller supports 122, 124 on which the rollers 102, 104 are mounted by studs 128, the support 122 having an offset portion 130. The screw 110 passes through elongated slots 126 in the arm portions 120. When the parts have been adjusted a handle 134 on the rod 108 is raised in a slot 132 and latched against a shoulder 136 so that the arms 120 are firmly clamped against each other with the upper surface of the upper arm clamped against the lower end of spindle 38. The upper end of the spindle 42 carries a knurled adjusting knob 140 by which the effective radial distance between the two rollers may be varied. When the workpieces contact the rollers their motion is arrested, and the depending portions in the grooves 22 are urged into contact with the inner or outer wall of the grooves, depending on the position of the rollers relative to the grooves, whereby the workpieces are rotated. Specifications 652,655 and 672,527 are referred to.