924,075. Dressing grinding wheels. CAVITRON ULTRASONICS Inc. Aug. 3, 1960 [Aug. 4, 1959], No. 26838/60. Class 60. The surface of a grinding wheel is cleaned by the method of supplying a liquid under pressure to a limited area of the surface where a thin layer is maintained in contact with the area by suitable flow - restricting means, and applying vibrational impacts of ultrasonic frequency and relatively small amplitude to the layer so as to subject it to cavitational action. As shown in Figs. 1 and 2, the liquid layer is confined between a rotating grinding wheel G and a shoe C which is vibrated to give the layer the necessary impacts. The invention is described as applied to the treatment of a grinding-wheel G carried by a vertically - adjustable slide 56 for operation upon a workpiece W<1> held by a holder 61 in a tray 60 which is mounted on a table 53 movable longitudinally on a transversely - movable base 51. A rail 70 projecting from the wheel guard housing 63 supports a carriage on which is mounted a vibrator assembly A in the form of a transducer 1, Fig. 2, carrying at one end the shoe C in slightly spaced relation to a portion of the wheel periphery. The transducer 1 is housed in a tubular body 11 screwthreaded in a hanger 86 suspended from a rod 82 secured in trolleys 72, 78 from the rail 70. The hanger 86 is adjustable on the rod 82 by means of an adjusting cap 90 acting against a spring 91 so as to permit precise spacing of the unvibrated shoe from the wheel, this spacing being maintained even as the wheel wears away because a wear-resistant roller 77 on the bracket 72 is constantly urged into contact with the wheel by a spring 83. The transducer section 2 and a substantial part of the body 3 connecting it with the shoe are supported at the inner end of the housing 11 by a resilient sealing ring 20 engaged by an end collar 21 which is clamped by tie rods 22 to the hanger 86. That portion of the housing 11 surrounding the transducer section 2 is wound with a wire winding 16 which is protected by a tubular sheath 19 and has its ends led outwardly into a recessed part of the hanger where they are connected by a twopart separable connector 30, 32 with wires in a flexible cable 28 leading to an A.C. generator 35. Coolant is supplied to the interior of the housing 11 and returned therefrom through pipes 26, 27 passing through a sealed plug 24 at the outer end of the housing and connected via the connector 30, 32 with corresponding conduits in the cable 28. The transducer section 2 is of electrodynamic, piezoelectric or magnetostrictive type and the connector body 3 is of metal of high tensile strength. The shoe C which is connected to the body 3 by silver solder or a threaded stud 4, Fig. 2, has an enlarged head having an arcuate face 6<1> conforming with the operative face of the wheel and provided with a number of small slots 7 to serve as a reservoir for the cleaning liquid; the face 6<1> may be given the desired contour by feeding the shoe into contact with the grinding wheel. Side flanges 6<11> integral with the head or independently supported serve to confine the liquid layer at the face 6<1>. As shown in Fig. 2, this liquid is fed through a pipe 9 to passages 7<11> in the shoe leading to the reservoir slots 7. When the grinding wheel is made of porous material, this method of supply may be replaced by, or supplemented with, a radially-outward feed of the liquid through the structure of the wheel, the liquid then being gravity fed to both sides of the wheel near its centre and passing through shrouded slots 65<1>, Fig. 15, in the clamping plates 65 into the central body portion of the wheel. The liquid may, alternatively, be forced into a wedge-shaped gap 6c, Fig. 21, between the upper edge of the shoe and the grinding wheel from a relatively flat and wedge-shaped nozzle 8a located within the gap. When the surface of the grinding wheel is cylindrical, the vibration of the shoe is linear along the axes of the body 3 by arranging the neck portion 5 of the shoe to be a straight continuation of the body 3. In all cases, the shoe C is arranged to conform with the surface of the grinding wheel so that in the case, for example, of a wheel as shown in Fig. 16 for cutting threads on a workpiece, the face 6<1> of the shoe is formed with ribs 6a intersecting the reservoir slots 7. In order to ensure the treatment of the whole surface of a toothed or otherwise contoured grinding wheel, the vibrations of the shoe, instead of being linear, may take an elliptical or circular form by providing the neck portion 5 with a cavity 5b of the necessary shape on one side. The cleaning fluid is one having low surface tension with wetting or detergent properties and may be selected from the anionic or cationic hydrophilic groups of wetting agents. The effectiveness of the arrangement described is stated to derive from the maintenance of the thin liquid layer between the grinding wheel and shoe notwithstanding the centrifugal force tending to spin it off, and the simultaneous cavitation action which is produced by the vibration of the shoe and is of such strength as to pull out embedded workpiece particles and loose abrasive grains from the wheel ; the spacing between the periphery of the wheel and arcuate face of the shoe is not more than 0.01 inch and the frequency of vibration of the shoe is preferably 20,000-40,000 cycles per second with a stroke of 50 microns. The method may be used with surface speed of up to 5,800 linear feet per minute.