Patent GB-677518-A (GB)
Title: Improvements in or relating to mounting devices for rubbing machines
IPC: B24B23/04
Filed: 1949-02-22
Abstract: 677,518. Rubbing-machines. STEVENS, A. H. (Du-Fast, Inc.). Feb. 22, 1949, No. 4793/49. Class 60. [Also in Groups XXIV and XXV] A mounting for the eccentrically driven live member or frame of a rubbing attachment which mounting constrains the member to a movement such that any line thereon remains parallel to its original direction as the eccentric driving member causes the live member to move so that any point thereon traces out a circle, comprises two parallel motion linkages connected together in series with their respective planes of movement at right angles to one another, the linkages being interposed between the live member or frame and a dead member or frame of the device, one of the linkages being coupled to the dead frame and the other to the live frame. A dead frame 1 is disposed in spaced parallel relation to a live frame 2, and an intermediate frame 3 is disposed substantially midway between the frames 1, 2 in parallel relation thereto. The intermediate frame 3 is flexibly connected to the dead frame 1 by a system of normally parallel link members 4 and is flexibly connected to the live frame 2 by a system of normally parallel link members 5 disposed at right angles to the system of link members 4. The link members 4, 5 are each constituted by a short strip of flexible material, e.g. power belting capable of undergoing a practically infinite number of flex stress reversals over a pulley of small diameter without failure. One end of each link member 4 is gripped by an end rail 7 of the intermediate frame 3, the other ends of the link members being gripped by fittings 8 secured to the dead frame 1 by bolts 27; the link members 5 are likewise gripped at one end by the side rails 6 of the intermediate frame 3 and at the other ends by fittings 9 on the live frame 2. The live frame 2 is actuated by a crank member 10 having a stub shaft 11, a crank pin 12 and a counterweight portion 13. The crank pin 12 is snugly but not tightly received in the inner raceway of a ballbearing unit 14 on the live frame 2, the tip portion of the crank pin being spherical to permit some self-aligning rocking action of the crank pin in the raceway; the radial thrust force of the crank is applied to the live frame substantially in the horizontal plane of the centre of gravity of the live frame, the centre of gravity and centre of actuation of the live frame being substantially coincident. The counterweight 13 is close to the live frame substantially in the bearing plane. The dead frame 1 is suitably constructed for releasable attachment to the barrel (motor housing) or other fixed portion of a portable electric drilling machine. The dead frame has an aperture 16 through which is inserted the chuck end of a drilling machine 17 from which the chuck is removed, the stub shaft 11 of the crank member 10 being threaded for releasable engagement with the chuck driving spindle of the drill. A pair of lugs 19 carried by the attaching head 1 engage the barrel of the drill at spaced points, preferably in the cooling and ventilating apertures 20 of the drill motor housing. A movable clamping member 21 is pivotally supported on the end of a clamping screw 22 threaded in a lug 23 integral with the attaching head 1; lugs 24 integral with the member 21 engage in the ventilating apertures 20, and guide members 25 integral with the member 21 extend outwardly therefrom in sliding engagement with the attaching head so serving to maintain the clamping member in an upright position. The live frame or rubbing head 2 comprises a relatively stiff flat pressure plate 28 having upstanding marginal stiffening flanges 29 at its opposite sides and upwardly-curved inwardlyturned end portions forming sockets 30 in which the ends of a sheet 31 of sand paper or other rubbing material are removably secured. The plate 28 is reinforced by a stiffening member 32 extending from side to side of the plate and apertured to fit snugly over and around the bearing socket member 15 upon a circumferential marginal base portion 33 providing a broad support for the bearing socket 15; fastening means 34 hold the bearing socket in fixed position between the stiffening plate 32 and pressure plate 28 centrally of the latter. Each end of the rubbing shoe carries fastening means for releasably securing the sheet of rubbing material, each fastener comprising an actuating lever member 36 mounted between and upon brackets 37 secured to the stiffening plate 32, for pivotal movement on bearings 38; side flanges 39 of the lever member 36 provide pivot bearings 40 for the ends of a spring-wire retaining member 41 adapted to be lodged snugly in the pocket 30. A layer 42 of soft rubber or other resilient material is bonded to the under surface of the pressure plate 28. In a modification, Fig. 6, the crank member 10 is recessed to receive the bearing unit 14 which fits over a cylindrical pin 43 having an annular mounting flange portion 44 secured between the stiffening plate 32 and pressure plate 28; this construction enables the counterweight 13 to be positioned closer to the rubbing head.