Patent GB-336995-A (GB)
Title: Improved method of and apparatus for blowing soot from tubes and other surfaces
IPC: F23J3/00
Filed: 1929-07-23
Abstract: 336,995. Smith, W. A., and Glinn, R. J. July 23, 1929. Cleaning, flu'id-pressure processes for. - The tubes &c. of boilers are cleaned by blowing air &c. against them in pulsations effected by a pulsator 6, Fig. 1, interposed between the source of supply of cleaning air and the blower tube 2<1>, which is also adapted intermittently to rotate the said blower tube. The pulsator comprises a casing having an air inlet 7 and outlet 8 and a dividing wall 5 which is formed with an orifice providing a seat for a valve 1 controlling the air supply and defining a chamber 10 in which a spring-pressed piston 3 reciprocates. The piston 3 is larger in diameter than the valve 1 and, is subjected to the air supply pressure, while the chamber 10 is provided with a vent port 26. The piston rod 11 is connected by links 16, 20 to a lever 22 pivoted to the blower head 2 and carrying a pawl 24 engaging a ratchet,wheel 25 secured to the blower tube, and the valve 1 is provided with an actuating rod 13 pivoted to the link 16 on the side of the fulcrum 17 remote from the piston rod 11. In operation, when compressed air is supplied to the pulsator the pressure increases until the load on the piston is sufficient to overcome the resistance of the piston spring 4 and the load on the underside of the valve 1. The piston will then rise, partially rotating the blower tube 2<1> through the pawl and ratchet wheel and opening the valve 1 to allow air to pass to the said tube. When the supply pressure falls the piston will return to its original position and shut the valve and maintain it so until the pressure again rises. In a modification the stem 13 of the valve is not connected to the link 16 but is formed with a head adapted to be engaged and depressed by the said link on upward movement of the piston, the valve being normally maintained in its closed position by a spring interposed between an abutment inside the pulsator casing and a disc secured to the valve stem. Alternatively the piston and valve are carried by a common spindle and the air is admitted to the casing therebetween. In a further modification, Fig. 4, a pair of differential ported pistons 36, 37 are secured on a spindle 38, the larger piston 36 constituting the air control valve and being displaced under differential air load in opposition to the action of a spring 4 pressing thereupon. The outer face of the piston 36 is exposed to the supply pressure, while the outer face of the smaller piston 37 is connectible to the supply pressure through ports 41, 43 and a pipe 46, and to atmosphere through ports 42, 44. In the form shown in Fig. 5 the pulsator comprises a spring- pressed piston 48 and the piston rod 51 thereof carries a pawl 52 which co-operates with a ratchet wheel 53 to rotate same and also a cam 54 integral with it, the latter acting through a follower 55 on a lever 58 to rotate the blower tube through a definite angle and then return it to its original position. The cleaning air is supplied to a port 49 of the pulsator chamber 62 and, on attainment of a predetermined pressure, opens a pilot valve 64 which allows air to act upon the piston and move it to actuate the cam 54 and permit the air to pass to the blower tube through a port 50. The piston is returned to its original position by air which is led to the back of the piston through a bye-pass passage 67.