Patent GB-1076389-A (GB)
Title: Dual motion surface dressing machine
IPC: B24B23/04
Filed: 1965-12-30
Abstract: 1,076,389. Grinding. PORTABLE ELECTRIC TOOLS Inc. Dec. 30, 1965 [Jan. 11, 1965], No. 55212/65. Heading B3D. A surface-dressing machine comprises a housing with an open side, means for connecting a source of vacuum to the interior of the housing, a plate resiliently attached to the housing in position in the opening of the open side, the peripheral edge of the plate being closely spaced with respect to the edges of the open side of the housing so that upon the source of vacuum creating a pressure differential between the inside and outside of the housing, air and dust will be drawn into the housing through the spacing between the edges of the plate and the edges of the housing, and a driving mechanism carried by the housing and connected to the plate for imparting motion to the plate. The machine consists of a housing (21, Fig. 1) containing a vertically disposed motor which is oonnectible to a source of power by a bayonettype connection (25) disposed in a handle portion (22) of the housing which also has a knob (26) mountable on any one of the three faces of the housing which do not support the handle (22). The lower portion (23) of the housing is of hollow inverted rectangular shape and cooperates with a surface dressing member assembly (32) comprising a plate 48 attached to a backing pad 58 of rubber or like material for a sheet of abrasive material. The member 32 is resiliently supported from the housing portion 23 by tapered resilient members 35 which extend between ferrules (38, Fig. 5) secured to the members 32 and ferrules (40) carried by bolts (50) extending transversely of the housing portion 23. The abrasive sheet is releasably secured to the ends of the assembly 32 by resilient members 77 which are urged into the clamping position shown in Fig. 4 by clamp members 62 urged about pivots 70 by springs 74, 75, the clamp members having pointed ends 80 which co-operate with apertures 82, 83 in the resilient members 77 and plate 48 to assist in gripping the abrasive sheet. The clamp members can be moved about the pivots to permit the resilient members to move away from the backing plate so that an abrasive sheet can have its end placed between the plate 48 and the end 79 of the resilient member for clamping therebetween when the clamp member is returned to its initial position. The movement of the clamp members is effected by blocks 85 which are accessible externally of the housing portion and can be moved against the force of compression springs 95 from the position shown in Fig. 4, wherein parts 89 of the blocks are spaced from the clamp members, to positions wherein the parts 89 abut and rotate the clamp members about their pivots. The blocks are releasably retainable in the latter positions by engagement of corners 93 of the blocks with stops 94 on the housing. The surface dressing assembly 32 may be moved with either orbital or reciprocating movement and is driven from the motor in the housing which has a shaft 102 connected by gearing 104, 109 to a stub shaft 105 mounted in the housing. The shaft 105 has an axis 105<SP>1</SP> and is connected by an insert to a counterweight disc 117. A drive pin 118 is eocentrically mounted in the insert and receives a ball bearing 140 located within a resilient ring 144 in turn located in a block 138 of iron-nickel powdered metal impregnated with lubricating oil. The block 138 is slidable in a channel member 120 which is secured, for example, by welding, to the upper surface of the plate 48 with its axis slightly inclined to an axis transverse to the longitudinal axis of the plate 48. The lower portion of the block has a longitudinal recess (171, Figs. 7 and 8) defined by walls (169, 170) formed with depressions (173). An enlarged portion (125) of a lever is disposed within the longitudinal recess and is formed with portions (148) for co-operation with the depressions, the lever being rotatably mounted on a hollow rivet 127 which also serves to pivotally connect a depending portion 130 of the lever to the channel 120 and backing plate 48. The lever can be moved to one position (Fig. 7) in which the portions (148) of the lever engage the depressions (173) in the block (138) so that the block is prevented from sliding relative to the channel 120 and orbital movement of the pin 118 causes orbital movement of the assembly 32, or to an alternative position (Fig. 8) in which the portions 148 are disengaged from the depressions and the block can slide relative to the channel so that the orbital movement of the pin is converted into reciprocatory movement of the assembly 32. The lever is releasably retained in its positions by a spring (163) and can be moved from one position to the other by manual movement of a slide (157) mounted on the housing and formed with projections 154 having a lost-motion connection with an arm 153 of the lever. The lower edge of the housing has a rubber beading 185 having an inclined surface 186 corresponding to inclined surfaces 55 on the surface dressing assembly 32 to provide a minimal gap through which air and dust are drawn by a vacuum source connected to a tapered opening 180, Fig. 3 (not shown), in the housing. The machine may be used for wet or dry grinding.