GB742321A - Improvements in and relating to pressure actuated blast guns - Google Patents

Abstract

742,321. Soot-blowers. AIRNESCO PRODUCTS, Ltd. April 13, 1954 [April 13, 1953], No. 10089/53. Addition to 733,165. Class 99(2). [Also in Group XXIX] In the portable blast gun described in the parent Specification wherein blasts of pressure air or steam are emitted from the gun when a valve V is opened by a piston 111 working in a cylinder A, the cylinder is divided by the piston, or other differentially-operated member, into chambers C<SP>1</SP>, C2, and the piston is moved against the action of a spring 10 due to a drop in pressure in the chamber C<SP>2</SP>. The chambers are interconnected by a balance pressure duct, e.g. a duct 22 in the piston, and means, e.g. comprising a piston 102 working in a cylinder 100 and held on a seating by a spring 104, is responsive to a predetermined pressure in the chamber C<SP>2</SP> for opening that chamber to atmosphere to cause a spontaneous drop in pressure in the chamber. As shown, the chamber C<SP>2</SP> is exhausted through ports 105 uncovered by the piston 102, and the piston 111 is rigidly fixed to the valve V. A reduced diameter portion 103 of the piston 102 projects through an opening 101 connecting the cylinder 100 and the chamber C<SP>2</SP> so that an increased area is subjected to the pressure within the chamber C<SP>1</SP> when the piston is moved off the seating thus ensuring that the force acting against the return spring 104 is in excess of the initial unseating pressure of the piston. A cap 106 screwed onto the cylinder 100 allows the thrust of the spring 104 to be varied to give different pressures against which the piston 102 is displaced to open the ports 105 ; the cap is also used to start and stop operation of the gun as an alternative to closing or opening the inlet 41 of the chamber C<SP>1</SP>. In operation, the cap 106 is unscrewed to give a setting of the spring 104 that fails to counterbalance the pressure in the chamber C<SP>2</SP> and the piston 102 is moved to uncover the ports 105, the piston 111 being moved by the pressure in the chamber C<SP>1</SP> to open the valve V. The pressure on each side of the piston 111 becomes equalised and the spring 10 returns the piston to a position whereby the valve is closed, the pressure in the chamber C<SP>2</SP> being such that the spring 104 restores the piston 102 to a position in which the ports 105 are closed. When the pressure in the chamber C<SP>2</SP> has built up by the flow of air through the duct 22 the cycle of operations is repeated until the cap 106 is screwed down to prevent operation of the piston 102, or the inlet 4<SP>1</SP> is closed. In a modification, the valve V, Fig. 3, is operated by a diaphragm 112 of rubber or other resilient material secured to the wall of the cylinder A ; alternatively, the diaphragm is held by a liner inserted in the cylinder, or annular locking sleeves.