Patent GB-702893-A (GB)
Title: Apparatus for supplying fluid-borne flow of abrasive material
IPC: B24C7/00
Filed: 1952-09-18
Abstract: 702,893. Pneumatic conveyers ; hopper discharge. RITTER CO., Inc. Sept. 18, 1952 [Oct. 1, 1951], No. 23478/52. Class 78 (1) [Also in Groups VI, XXIII and XXXV] Apparatus for supplying a fluid-borne flow of abrasive material comprises a container for the material having an orifice adjacent its bottom, a mixing chamber below and communicating with the orifice and having an outlet, a source of fluid under pressure, a movable fluid conduit communicating with the source and extending through the chamber and orifice and terminating adjacent the upper portion of the container, a fluid duct from the upper portion of the container to the chamber, valve means connected with the conduit for movement thereby to control the flow of the material through the orifice and means for moving the conduit to stir the material in the orifice and container and to actuate the valve means to supply the material to the chamber for mixture with fluid from the duct and discharge through the chamber outlet. When intended for use by dentists for cutting and shaping teeth by the action of fine abrasive such as aluminium oxide in a jet of carbon dioxide, air or the like, as described in Specification 235,832, [Class 81 (11)], the apparatus comprises a cabinet 20, on castors 21, having a control head 22, with an instrument panel 23, from which extends a flexible conductor 24 having at its free end a handpiece 25 carrying a jet nozzle 26, such as that described in Specification 691,703, [Group XXIII], a holder 27 may be provided for releasably supporting the hand piece. A suction pipe 28 extends upwardly through an opening in the top 29 of the cabinet, in which it is supported for vertical adjustment by a telescopic joint, and connected with a filter and a source of reduced pressure ; the upper portion of pipe 28 is turned horizontally at 30 with an open end 31 adapted to be positioned adjacent the patient's mouth for withdrawing the abrasive and other products of the operation. The fluid, e.g. carbon dioxide gas, is supplied from a tank 32 through a pressure reducer 33 and pipe 34 to a pipe 36 either through pipe 35 when a valve 38 therein is open, or through a further pressure reducer 41 when valve 38 is closed. The valve 38 is closed by a spring and is opened by a solenoid device 39 controlled by a switch 93 on the instrument panel. The pipe 36 is connected to a valve 37 manually operated by a knob 45 on the instrument panel; in one position of the valve 37, the gas passes through pipe 42 to the abrasion chamber, the abrasive-laden gas passing through pipes 43, 44 to the handpiece jet ; the valve 37 in its other position by-passes the mixing chamber and delivers gas direct to the pipe 44. The means for supplying the abrasive material to the carrier gas comprises a container 46 supported in the cabinet. A removable top closure 47 is provided with a relief valve 54 which is normally closed by the pressure of the contained fluid aided by a spring, but which can be opened, by depressing knob 51, to relieve the pressure in the container when use of the apparatus is discontinued. A threaded plug 62 has an abrasive discharge orifice 63 leading into a mixing chamber 64 formed in a valve block 65 integral with the container. A tube 66 connected at its lower end with the gas supply pipe 42 extends upwardly through the orifice 63 with clearance and is vibrated laterally to agitate and stir the abrasive material ; it is preferably provided with holes for producing jets of gas for stirring the material and keeping it in a loose condition for flowing down through orifice 63. The upper end of tube 66 is turned laterally at 71 to direct gas into a conduit 72 formed in the container wall and discharging laterally at 74 into the chamber 64, mixing there with abrasive falling through orifice 63 and driving the mixture into pipe 43 leading to the jet nozzle 26. Discharge of abrasive through the orifice 63 is controlled by a body 77, of magnetic material, e.g. steel, secured to the tube 66 just below the orifice. The upper end of body 77 is roughened by a series of concentric corrugations or V-grooves to form outwardly inclined ridges. When the tube is stationary discharge of abrasive from the orifice is obstructed ; when the tube is vibrated abrasive is worked outwardly by the corrugations and discharged at the sides of the body 77 so maintaining a steady flow of abrasive at a rate substantially proportional to the amplitude of vibration of the tube 66. The tube 66 is vibrated by an electromagnet 79 having a laminated core 80 of E-shape with its energizing coil 81 surrounding the central branch of the core and the outer polar branches of the coreterminating adjacent the outer walls of the bottom block 65 of the container so as to produce a magnetic field extending through the body 77. The magnet coil is excited with pulsating direct current from a half-wave rectifier 101 through a potentiometer 102 by adjustment of which the amplitude of vibration is varied. The supply of abrasive mixture through pipe 44 to jet nozzle 26 is further controlled by a valve 85 ; by energizing a solenoid 86 the valve is moved to a position in which the abrasive stream passes through conductor 24 to the handpiece 25 and jet nozzle 26 ; when the solenoid 86 is de-energized the valve is moved by a spring to another position in which the abrasive stream is diverted through a pipe 87 to a filter 88 for removing abrasive material from the gas and allowing the latter to escape to atmosphere. The filter 88 is positioned in the lower portion of the cabinet 20 and is provided with a pipe elbow 111 having a telescopic connection with pipe 28. The filter is connected at its top with the intake of an exhaust fan 112 driven by an electric motor 113. The discharge from the exhaust fan is connected with the space in the cabinet around the filter, outlet openings being provided in the bottom of the cabinet. When valve 38 is closed to reduce the pressure of the gas supplied to mixing chamber 64, the pressure in pipe 44 is reduced by operating, by means of a solenoid 91, a valve 90 in a pipe 89 leading to the filter 88 through a relief valve 92. The solenoids 39, 91 for actuating valves 38, 90 respectively are jointly controlled by a switch 93. Simultaneous control of the supply of abrasive material and fluid carrier is effected by a treadle 104 operating a foot switch 105 which controls supply to rectifier 101 and solenoid 86. A main switch 109 is provided.