Patent GB-681996-A (GB)
Title: Portable rubbing machine
IPC: A47L11/12
Filed: 1949-06-14
Abstract: 681,996. Portable rubbing machine. PORTER-CABLE MACHINE CO. June 14, 1949 [June 2, 1949], No. 15771/49. Class 60. [Also in Groups XXII, XXV and XXVI] A portable rubbing machine operated by compressed air comprises a body having a cylindrical opening, double-acting pistons mounted for reciprocation in the cylindrical opening, a valve in the body for supplying air alternately to facing ends and outer ends of the pistons and exhausting it therefrom, slides for operating the valve, rubbing shoes, and driving members extending from the rubbing shoes and the slides through one side of the cylindrical opening and into the pistons to provide driving connections between the pistons and the slides and the rubbing shoes, each member being directly secured to one shoe and also directly secured to one slide and extending into one piston. A body 20 having side indentations 22 and a control member 23 carries oppositely reciprocating rubbing shoes 25, 26; a liquid jet 27 secured to one side of the body extends between the rubbing shoes for applying liquid to the surface of the workpiece during wet rubbing operations. Each rubbing shoe 25, 26 comprises a shoe plate 28 to the bottom surface of which a soft pad 30, e.g. of rubber or felt, is secured. Sheet material 32, e.g. sand paper, is removably secured to the rubbing shoes, by clips 33. The clip structure includes a block 34, on the top of the shoe plate, having an inclined end gripping surface 35 inwardly of the end of the shoe plate; a link 37 has one side supported for limited rotational movement in a bearing bore 36 in the block, the opposite side of the link being movably engaged by loops 38, integrally formed at opposite ends of a C-shaped sheet metal clip element 40 having a gripping edge 43. A tab 42 integrally formed on the element 40 serves for opening and closing the fastener. The body 20 is a cast metal structure; a main block 44 has a longitudinal bore 45 containing cylinder liners 48, 49; internal cavities 53, 54 in the block 44 encompass top and side portions of the liners. Slots 55, 56 in the liners register with slots 57, 58 in the bottom wall 59 of the main block. Air can flow from cavity 53 to slot 57 through passage 60. A valve cavity 62 has a cylindrical lower portion 63 and threaded upper portion 64; a bearing bore 65 containing a sleeve bearing 66 extends across the bore 45. To minimize drilling operations in the main block, particularly in the case of long passages and those having angularly disposed portions, metal tubes are positioned in the mould for the block so that they are cast into the block when it is made. One tube 67 extends from the plane end surface 47 to the cylindrical lower portion 63 of the valve cavity; another tube 68 extends from the plane end surface 47 to the mid-portion of one side of the block near the bottom thereof to provide a passage for liquid used in wet rubbing operations; a third tube 69 extends from one end surface of the block to the other, parallel to the main bore 45, a drilled passage 70 providing connection with the valve cavity. A drilled passage 72 connects the valve cavity to the main bore 45; drilled passages 73, 74 connect the valve cavity to the internal cavity 53. The pistons 75, 76, provided with piston rings 77, 78, each comprise hollow end portions 79, 80 closed by metal discs 82, 83 pressed into annular recesses 84, 85, the end portions being joined by a partition 86 having a lateral bore 87 receiving driving posts 88, 89 secured by pins 90, 92. The posts 88, 89 extend through the slots in the cylinder lines and in the block and at their exposed ends have slide receiving shank portions 93, 94 and shoe-supporting feet 95, 96. The cylinder bores are closed by end caps 97, 98 having channels 99, 100 in their inner faces connecting the opposite ends of the tube 69 and the outer ends of the cylinder bores. The end cap 98 has adjacent parallel ports 102, 103 extending inwardly from a top recess 104; the bottom of each port communicates with a lateral bore 105 adapted to receive a threaded fitting 106 on a hose line. Valves 112, 113 are biassed by springs 114, 115 to close passages 116, 117 in their valve seats 107, 108. Passage 118 in valve seat 107 connects with the end of tube 67; passage 119 in valve seat 108 connects with the end of tube 68. The valve stems 120, 122 project into the recess 104, and are actuated by a common control member 23 comprising a shell having an exposed wall 123 conforming to the general contour of the body, and side walls 124 extending into aligned recesses 24, 104 in the block and end cap. A leaf 125 secured to the lower surfaces of the side walls 124 has a curved portion 126 at one end engaging a cross pin 127 at the inner end of the recess; the opposite end of the leaf engages the projecting valve stems 120, 122. Aligned slots 128 in the side walls engage studs 129 projecting inwardly from the sides of the recess to limit the movement. The bottom wall 59 of the body 20 has grooves 132, 133 receiving cylindrical slide bars 134, 135 secured in place by end cross clamping strips 136, 137 held in place by screws 138. Slides 139, 140 have pairs of grooves 142, 143 and 144, 145 fitting on the bars. Openings 146, 147 in the slides fit on the shank portions 93, 94 of the drive posts 88, 89 and are secured in place against the feet 95, 96 on the posts by screws 148. Parallel arms 149, 150 project from adjacent ends of the slides 139, 140, the arms having lateral channels 152, 153 carrying slide blocks 154, 155 having bearing bores 160, 162 into which project studs 158, 159 carried by the opposite ends of a cross head 157 on one end of an oscillator shaft 156 journalled in the sleeve bearing 66, the other end of the shaft extending into the valve cavity 62. The slide bars 134, 135 have arcuate notches 163, 164 to clear the ends of the cross head 157. The shaft 156 oscillates a distributing valve 165 in the valve cavity 62, the bottom surface 167 of which has ports 70, 72, 73 and a projection 168 which fits in an opening 170 in a stationary valve plate 169 having ports 172, 173 registering with the passages 70, 72, and an arcuate slot 175 registering with the port 73. A valve rotor 176 has an arcuate channel 178 in its lower surface which connects the arcuate slot 175 with one or other of the ports 172, 173. Notches 179, 180 control the flow of air to one or other of the ports 172, 173. In one position of the valve, air under pressure from the passage provided by the tube 67 is supplied to the outer ends of the cylinders through passage 70, while air is exhausted from between the pistons through the ports 72, 73. In the opposite position of the valve, exhaust is from the ends of the cylinder while pressure air is admitted between the pistons. In both positions, the exhaust air flows outwardly through the port 73, passage 74, cavity 53 in the body, passage 60 and slot 57 from which it escapes from the lower portion of the machine around the slides and adjacent the shoes, the body acting as a muffler for quieting the operation of the machine. The oscillator shaft 156 has a notched end 182 fitting into a correspondingly shaped opening 183 in a valve actuating member 184, a stud 185 projecting upwardly from the movable valve plate 176 being disposed in the slot 186 in the member 184. A compression spring 191 is disposed between the member 184 and a valve cap 181 threaded into the upper portion 64 of the valve cavity. An apron 187 has side flanges 188 fitting over lower marginal portions of the machine body and a face portion 189 covering the slides and having openings 190, 192 for passage of the feet 95, 96. Interposed between face portion of the apron and the lower faces of the slides and arms are felt pads 193, 194, 195 which control the outward flow of exhaust air during operation of the machine and also exclude dust and dirt from the operating parts of the machine. Each of the shoes 25, 26 has a top plate 196 secured thereto by rivets 197. A shoe supporting stud 198 having a head portion 199 extends upwardly from each of the shoes to serve as a mounting element for securing the shoes to the feet 95, 96. A notch 200 is provided in one side of each of the studs; the feet 95, 96 have axial openings snugly fitting the projecting studs. For securing the rubbing shoes in place, a, set screw 203 is threaded into an outside end of each of the slides and has a tapered end adapted to engage the notch 200 in the stud to draw that stud inwardly as the screw is tightened. Aligned openings 204, 205 in the apron and clamping straps provide access to the ends of the set screws for effecting the removal and installation of the shoes relative to the machine.