GB1588966A - Valves for abrasive blast cleaning machines - Google Patents

Description

(54) IMPROVEMENTS IN OR RELATING TO VALVES FOR ABRASIVE BLAST CLEANING MACHINES (71) We, LODGE CLEMCO LIMITED, a British Company, of Orgreave Drive, Handsworth, Sheffield, S13 9NR, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: - This invention relates to valve means for abrasive blast cleaning machines, and is particularly concerned with valve means within the machine to control the supply of abrasive material (grit or shot) to the blast hose.

It is highly desirable in shot blast machines to be able to control the flow of abrasive into the blast line. Tn the absence of any valving arrangement at the bottom of a hopper for the abrasive, abrasive is gravity fed into the blast line, and picked-up by the pressure air passing therethrough.

At the cessation of operations, abrasive remains in the blast line, and must either be manually removed (a troublesome task) or left there to be blown clear at the start of the next blasting operation with a consequent waste of the not inconsiderable amount of abrasive in the line. Abrasive in the blast line at the start of blasting can also constitute a potential hazard to the operative.

Attempts have been made to provide valve means at the hopper outlet, but such attempts have not met with any appreciable success. Conventional stop valves are not capable of withstanding the arduous conditions present within abrasive blast cleaning machines, and the excessive wear that can take place requires replacement of such valves at far too great a frequency for it to be an economic proposition to use them.

It has also been proposed to meter the supply of abrasive with, e.g., a paddle wheel type of dispensing means at the hopper outlet, but this can result in slugs of abrasive passing down the blast line in pulses, which does not result in efficient usage of the abrasive and can result in bad blasting because of the non-continuous firing of abrasive at the surface being cleaned.

According to the present invention, a valve for controlling the flow of abrasive material from, e.g., a hopper to the blast line of an abrasive blast cleaning machine comprises compressible sleeve-like means adapted to be connected at one end to, e.g., a hopper outlet, and at the other end to the blast line of the machine, means associated with the sleeve-like member capable of compressing it ta an extent sufficient to close the bore therethrough, and control means for the compression means being fluid adapted to be supplied to both sides of a piston in a cylinder, the piston rod of which extends out of the cylinder and into contact with the sleeve-like member, pressure fluid being admitted to opposite sides of the piston such that the sleeve-like member is compressed and/or opened, and in the ab- sence of a signal, pressure fluid is removed from the return side of the piston and pressure fluid applied or maintained on the opposite side of the piston hence causing the piston to move automatically to fully close the sleeve-like member, and there being adjustable means in association with the piston to limit the maximum extent to which the sleeve-like member can be opened.

Thus, when a signal is fed by the operative to the control means, the sleeve-like member is caused to open, and if that signal is deliberately or accidentally removed, the compression means automatically closes the sleeve-like member to shut off the supply of abrasive material. To ensure that when the equipment is reactivated the same, predetermined, quantity of abrasive is supplied, the adjustable stop means limits the extent to which the compression means can move in a direction to open the sleeve-like member.

Preferably, the sleeve-like member is a sleeve of latex rubber or comparible synthetic plastics material and lies within a housing, with the housing having an access opening for the compression means. Thus the sleeve-like member is compressed between the compression means and the opposite wall of the housing.

Although the fluid activating the com pression means may be hydraulic fluid, it is preferred to use air control, and when the air supply essentially required by the shot blast machine may be utilised. Thus, in one embodiment of the invention, pressure air is admitted to the opposite side of the piston to the piston rod to urge the piston in a direction such that the end of the piston rod compresses the sleeve-like member to fully close its bore. Then, abrasive is required to be supplied, air is disconnected from that side of the piston, and admitted to the opposite side of the cylinder to cause the piston to move to the opposite end of the cylinder, and when the piston is brought into contact with an adjustable stop means extending into the cylinder, and thereby permit any desired quantity of abrasive to be fed to the blast line.

Instead of having a mechanical adjustable stop means, the adjustable stop means may be provided by pressure air. Thus, in an operative position, air may be supplied to both sides of the piston in a manner to move the piston to the required position following which the pressure in the cylinder to each side of the piston is equalised to hold the piston in the required position.

In the absence of a signal, pressure air may be removed from the return side of the piston whilst maintaining pressure air to the opposite side of the piston and hence causing the piston to move automatically to fully close the sleeve-like member. On the return of the signal, the valving arrangement may be such to ensure that the pressure conditions within the cylinder are re turned to be identical with the conditions that existed prior to the signal being removed and when the piston is automatically brought to the same open position and hence ensure that the original predetermined supply of abrasive is recommended.

To provide the necessary failsafe aspect, valve means are provided to control the admission of air to one or both sides of the cylinder as may be required, which valve means is activated by a signal from means activated by the operative, the valve means being so arranged, that in the absence of such signal, the piston is automatically moved in a direction to close completely the bore through the sleeve-like member.

Thus, a so-called "dead-mans handle" can be provided in a signal air circuit to the valve means, which when released removes the signal to the valve, which as a result either directs pressure air to the cylinder to drive the piston to the fully closed position, or when the spring means are provided, connects the cylinder to atmosphere so that the spring means drives the piston to the fully closed position.

Such a system has the distinct advantage of allowing the supply of adbrasive to be cut off, and pressure air maintained in the blast line, so that abrasive can be removed from the blast line at the end of blasting operations, allowing final depressurisation of the machine to take place with the blast line empty. The machine can then be restarted with greater safety. Also the supply of abrasive to the blast line can be closely controlled thereby providing continuously the correct amount of abrasive for a particular operation, and the avoidance of both damage to the component being blast cleared and the unnecessary and wasteful over supply of abrasive.

The invention will now be described with reference to the accompanying drawing which is a part schematic sectional side elevation valve means for controlling the flow of abrasive material from, e.g. a hopper to the blast line of an abrasive blast cleaning machine.

In the drawing, valve means 1 for controlling the flow of abrasive material from, e.g. a hopper (not shown) to the blast line of an abrasive blast cleaning machine (not shown) is formed by a sleeve-like compres sible member 2 adapted for connection at one end to the hopper outlet and at the other end to the blast line of the machine, the sleeve-like member 2 lying in the bore 3 of a housing 4. The housing 4 is in two halves suitably secured together by bolts 5 passing through lugs 6 on the housing. At each end of the housing, appropriate flanges 7 are provided for connection to the machine and to the blast line.

The housing 4 has one half member formed with an integral connecting piece 8 having a bore 9 communicating directly with the bore 3. The connecting piece 8 has end flanges 10 for securing the connecting piece 8 to the end of a cylinder 11 within which lies a piston 12. The piston rod 13 of the piston 12 extends through a central bore in an end cap to the cylinder and to a compression member 14 lying in the bore 9 of the connecting piece 8, which contacts the sleeve-like member 2 within the bore 3 of the housing 4. The piston rod 13 to the opposite side of the piston 12 extends telescopically within a thread and extending through a threaded hole in an end cap 16 to an operating handle 17. Externally of the cylinder, a knurled nut 18 is provided on the tube 15, and the end of the tube 15 lying within the cylinder acts as an abutment for the piston for reasons which will be explained below.

Inlet means 19, 20 for operating fluid (preferably pressure air) are provided connecting the cylinder to a control device 21 secured externally to the cylinder, there being means 22 secured to the control device for the supply of the pressure air.

Within the control device, appropriate valv ing arrangements are provided to direct pressure air into the cylinder, to one side or the other of the piston.

Thus, during operation of the blast cleaning machine, grit from the hopper is required to be fed to the blast cleaning line. Therefore with pressure air admitted to the control device 21, the control device is set such that pressure air is admitted to the side of the piston facing the housing 4 with the effect of driving the piston to the right as shown in the Figure, thereby withdrawing the compression member 14 from the compressible sleeve 2 to allow the passage of grit therethrough. When grit is required not to be supplied, the control device causes the admission of pressure air into the cylinder to the opposite side of the piston, and the discontinuance of supply of pressure air to the side of the piston facing the housing.This has the effect of driving the piston to the left as shown in the drawing causing the compression device 14 to compress the compressible sleeve 2 thereby preventing the continued supply of grit from the hopper. The provision of the adjustable tube 15 referred to earlier has the effect of providing an over-riding control over the maximum amount that the sleeve-like member 2 can be opened. Thus, the knurled nut 18 can be set on the tube 15 to determine the extent to which the tube 15 projects into the cylinder. Therefore the piston can be moved to the right (as shown) under the action of pressure air until it abuts the end of the tube.

To provide for failsafe operation, the control unit 21 is connected in a signal air system which includes a dead-mans handle.

Thus, with the dead-mans handle held in the operative position, the controls are set such that the valve means within the control unit can operate normally to provide for and discontinue the supply of grit as is required during machine operation. If for any reason the dead-mans handle is released, the control device is automatically set such as to close the compression member on to the sleeve 2 to prevent the continued supply of grit.

Providing the control unit 21 in a signal air circuit has the distinct advantage of allowing the supply of abrasive to be cut off with pressure air maintained in the blast line, and whereby grit can be removed from the blast line at the end of the blasting opeartions. This has the advantage of allowing a final depressurisation of the machine to take place with the blast line empty, providing the distinct still further advantage that the machine can be restarted in considerably greater safety than would otherwise be the case.

WHAT WE CLAIM IS: 1. A valve for controlling the flow of abrasive material from, e.g., a hopper to the blast line of an abrasive blast cleaning machine comprising compressible sleevelike means adapted to be connected at one end to, e.g., a hopper outlet, and at the other end to the blast line of the machine, means associated with the sleeve-like member capable of compressing it to an extent sufficient to close the bore therethrough, and control means for the compression means being fluid adapted to be supplied to both sides of a piston in a cylinder, the piston rod of which extends out of the cylinder and into contact with the sleevelike member, pressure fluid being admitted to opposite sides of the piston such that the sleeve-like member is compressed and/or opened, and in the absence of a signal, pressure fluid is removed from the return side of the piston and pressure fluid applied or maintained on the opposite side of the piston hence causing the piston to move automatically to fully close the sleeve-like member, and there being adjustable means in assocation with the piston to limit the maximum extent to which the sleeve-like member can be opened.

2. Valve means as in Claim 1, wherein the pressure fluid is supplied in a manner to move the piston to the required position following which the pressure in the cylinder to each side of the piston is equalised to hold the piston in the required position.

3. Valve means as in Claim 1 or Claim 2, wherein the sleeve-like member is a sleeve of latex rubber or comparible synthetic plastics material and lies within a housing, with the housing having an access opening for the compression means.

4. Valve means as in any of Claims 1 to 3, wherein the fluid activating the compression means is compressed air.

5. Valve means as in any of Claims 1 to 4, wherein control means are provided to control the admission of pressure fluid to the cylinder containing a piston, stop control means being in a signal air circuit including a failsafe device.

6. Valve means for controlling the flow of abrasive material from, e.g., a hopper to the blast line of an abrasive blast cleaning machine substantially as hereinbefore described with reference to the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. ing arrangements are provided to direct pressure air into the cylinder, to one side or the other of the piston. Thus, during operation of the blast cleaning machine, grit from the hopper is required to be fed to the blast cleaning line. Therefore with pressure air admitted to the control device 21, the control device is set such that pressure air is admitted to the side of the piston facing the housing 4 with the effect of driving the piston to the right as shown in the Figure, thereby withdrawing the compression member 14 from the compressible sleeve 2 to allow the passage of grit therethrough. When grit is required not to be supplied, the control device causes the admission of pressure air into the cylinder to the opposite side of the piston, and the discontinuance of supply of pressure air to the side of the piston facing the housing.This has the effect of driving the piston to the left as shown in the drawing causing the compression device 14 to compress the compressible sleeve 2 thereby preventing the continued supply of grit from the hopper. The provision of the adjustable tube 15 referred to earlier has the effect of providing an over-riding control over the maximum amount that the sleeve-like member 2 can be opened. Thus, the knurled nut 18 can be set on the tube 15 to determine the extent to which the tube 15 projects into the cylinder. Therefore the piston can be moved to the right (as shown) under the action of pressure air until it abuts the end of the tube. To provide for failsafe operation, the control unit 21 is connected in a signal air system which includes a dead-mans handle. Thus, with the dead-mans handle held in the operative position, the controls are set such that the valve means within the control unit can operate normally to provide for and discontinue the supply of grit as is required during machine operation. If for any reason the dead-mans handle is released, the control device is automatically set such as to close the compression member on to the sleeve 2 to prevent the continued supply of grit. Providing the control unit 21 in a signal air circuit has the distinct advantage of allowing the supply of abrasive to be cut off with pressure air maintained in the blast line, and whereby grit can be removed from the blast line at the end of the blasting opeartions. This has the advantage of allowing a final depressurisation of the machine to take place with the blast line empty, providing the distinct still further advantage that the machine can be restarted in considerably greater safety than would otherwise be the case. WHAT WE CLAIM IS:

1. A valve for controlling the flow of abrasive material from, e.g., a hopper to the blast line of an abrasive blast cleaning machine comprising compressible sleevelike means adapted to be connected at one end to, e.g., a hopper outlet, and at the other end to the blast line of the machine, means associated with the sleeve-like member capable of compressing it to an extent sufficient to close the bore therethrough, and control means for the compression means being fluid adapted to be supplied to both sides of a piston in a cylinder, the piston rod of which extends out of the cylinder and into contact with the sleevelike member, pressure fluid being admitted to opposite sides of the piston such that the sleeve-like member is compressed and/or opened, and in the absence of a signal, pressure fluid is removed from the return side of the piston and pressure fluid applied or maintained on the opposite side of the piston hence causing the piston to move automatically to fully close the sleeve-like member, and there being adjustable means in assocation with the piston to limit the maximum extent to which the sleeve-like member can be opened.

2. Valve means as in Claim 1, wherein the pressure fluid is supplied in a manner to move the piston to the required position following which the pressure in the cylinder to each side of the piston is equalised to hold the piston in the required position.

3. Valve means as in Claim 1 or Claim 2, wherein the sleeve-like member is a sleeve of latex rubber or comparible synthetic plastics material and lies within a housing, with the housing having an access opening for the compression means.

4. Valve means as in any of Claims 1 to 3, wherein the fluid activating the compression means is compressed air.

5. Valve means as in any of Claims 1 to 4, wherein control means are provided to control the admission of pressure fluid to the cylinder containing a piston, stop control means being in a signal air circuit including a failsafe device.

6. Valve means for controlling the flow of abrasive material from, e.g., a hopper to the blast line of an abrasive blast cleaning machine substantially as hereinbefore described with reference to the accompanying drawing.