GB1499594A - Particulate transfer control device - Google Patents

Abstract

1499594 Blasting FRUEHAUF CORP 17 April 1975 [15 May 1974] 15935/75 Heading B3D [Also in Divisions B8 and F2] A control device for use with apparatus, such as abrasive blasting apparatus, for pneumatically transferring a particulate material having an air passageway 12 and a particulate passageway 14 communicating with the air passageway, the device comprising closure means 42 for the air passageway, closure means 46 for the particulate passageway, and a sequencing mechanism connected to the closure means 42 and 46 and having control fluid passageways, the mechanism being so arranged that a first flow pattern of the control fluid when both closure means are open acts on the closure means first to close the particulate passageway and then the air passageway. As described, the apparatus is for abrasive blasting and a compressed air source is connected to an inlet 18, particulate material, such as sand is supplied to the passageway 14, and a hose having a nozzle is connected to an outlet 24. A transverse section 28 in the passageway 12 registers with a bore 36 which can be closed by the closure member 42, which is in the form of a diaphragm, when air pressure is supplied to a space 38. The particulate passage 14 communicate with the passageway 12 and can be closed when air pressure acts in a space 66 to cause a piston 61 to compress a resilient annulus 46. The sequencing mechanism consists of a housing 78 on the diaphragm housing connected by a pipe 80 to a control valve 82 and a source of control fluid. The pipe 80 connects with a bore 88 having a one-way valve 92 controlling a passage 90 leading to the space 38. A bore 86 leading from bore 88 is connected by bleed holes 94, 102 with the space 38 and a bore 100, respectively, bore 100 being connected by a pipe 84 to the space 66, and a one-way valve 96 connects the bore 100 to a passage 98 leading to the bore 86. With the valve 82 in the position shown, both spaces 38 and 66 are vented to atmosphere and both closure means are open, air and saud thus being supported on the nozzle. When valve 82 is moved by a handle to the dotted position, the control fluid is connected to bore 88. The control fluid, because the ball valve 92 closes, passes along bore 86, past ball valve 96 into bore 100 and pipe 84 to act quickly in space 66 to cause the piston to compress the member 46 and close the particulate passage 14. The control fluid also slowly passes through bleed passage 94 into space 38 so that the diaphragm eventually closes the bore 36 and thus the air passageway 12. To re-open the passageways, the valve 82 is turned to its position shown solid and the ball valve 92 permits the space 38 to be quickly relieved of pressure so that the diaphragm opens the bore 36 and thus the air passageway 12, the ball valve 96 closing so that the space 66 is vented through the bleed hole 102 and passages 86, 88 to cause the piston to gradually relieve the pressure on the member 46 and open the particulate passageway 14 after the opening of the air passageway 12.