GB2072062A - Apparatus for subjecting a workpiece to a jet of liquid - Google Patents

Abstract

Apparatus for removing solid matter from a workpiece by directing a jet of liquid from a nozzle 12 onto the workpiece supported on a platform 11 has a first tank (16) into which liquid drains from the workpiece and in which pieces of solid matter removed from the workpiece accumulate. Water containing suspended particles overflows from the first tank (16) into a conical tank (19) where the water is directed towards a narrow, lower part of the tank. The water flows upwardly through a wider part of the tank and overflows into a third tank from which it is pumped through a cyclone separator to a reservoir (21). Water projected at the workpiece is pumped from the reservoir. Suspended particles settle out of the water in the conical tank as the upward velocity of the water decreases in the wider part of that tank. Abrasive particles may be supplied through a conduit 14 to the nozzle which is supplied with liquid from the reservoir 21 by a pump 28. <IMAGE>

Description

SPECIFICATION Apparatus for subjecting a workpiece to a jet of liquid This invention relates to apparatus for treating the surface of a workpiece by directing a jet of liquid onto the surface. Particles of solid matter may be entrained in the liquid projected at the workpiece.

Apparatus of this kind is used for removing cores from castings and for otherwise cleaning work pieces.

Generally, the liquid used in apparatus of the kind referred to is water which is pumped at high pres sure to a nozzle which directs the jet of water onto the workpiece. The presence in the water being pumped of particles of solid matter, particularly abrasive particles which are commonly required to be entrained in the jet of water projected at the workpiece, causes severe damage to the pump. One way in which such damage can be avoided is by discarding water which has been projected art a workpiece and supplying fresh water to the pump.

This would require a plentiful supply of clean water and has the further disadvantage that water con taminated by solid particles would be discharged at a fairly high rate.

Apparatus in which water which has been pro jected at a workpiece is circulated back to the pump has been proposed but this apparatus suffers from the disadvantage that sufficient solid particles enter the pump to damage the pump severely. Means for separating solid particles from the recirculated water is unsatisfactory in practice.

It is an object of the present invention to provide improved means for separating solid particles from the water used in apparatus of the kind referred to.

According to the invention, we provide apparatus for treating the surface of a workpiece and compris ing a housing in which there is defined a chamber, means for supporting the workpiece in the chamber, a nozzle for directing a jet of liquid onto the work piece when supported in the chamber, a reservoir for a supply of the liquid, a pump arranged for pumping liquid from the reservoir to the nozzle, an outlet at the bottom of the chamber, a first tank arranged to receive from the outlet of the chamber liquid which has been directed onto the workpiece and solid mat ter which has been removed from the workpiece, a second tank arranged to receive from the first tank liquid and solid particles suspended in the liquid and means defining a liquid flow path along which liquid returns from the second tank to the reservoir, wherein the second tank is shaped to contain a body of liquid whereof the area of a cross-section in a horizontal plane in an upper part of the second tank exceeds the cross-sectional area in a horizontal plane in a lower part of the second tank, directing means is provided for directing into the lower part of the second tank liquid from the first tank and the arrangement is such that the liquid flows from the lower part through the upper part before leaving the second tank.

Because the cross-sectional area of the body of liquid in the second tank is greater in the upper part of the tank than in the lower part, the velocity of the liquid flowing upwardly through the second tank is less in the upper part than in the lower part. This allows particles to separate out of the liquid in the second tank.

The means defining the liquid flow path from the second tank to the reservoir would normally include means for separating further particles from the liquid.

The arrangement is preferably such that liquid flows from an upper part of the first tank into the second tank and that solid matter removed from the workpiece accumulates at the bottom of the first tank.

The first tank may include a weir over which the liquid flows from the first tank to the second tank.

The area of a cross-section in a horizontal plane of the body of liquid in the second tank preferably increases gradually with increasing distance above a bottom of the second tank.

It is preferred that the differential coefficient of increase of said area with respect to said distance is approximately proportional to the distance. By approximately, we mean within 20% of and preferably within 10% of.

An upper edge of a wall of the second tank may form a weir over which the liquid leaves the second tank.

The second tank preferably has the shape of a cone. The apex angle of the cone may be in the range 70" to 120 .

The directing means preferably comprises a tube having an open upper end through which liquid flows from the first tank and an open lower end from which liquid flows into the lower part of the second tank. The diameter of the tube may be within the range half to one eighth the diameter of the second tank at the level of the weir. In the case of a noncircular element, references herein to the diameter are to the mean distance between opposite points on the element.

The area of the surface of the body of liquid in the second tank is preferably within the range ten to twenty times the cross-sectional area of the tube.

At the level of the lower end of the tube, the diameter of the body of liquid in the second tank is preferably within the range two to four times the diameter of the tube.

The upper end of the tube is preferably exposed above the surfaces of the body of liquid in the second tank or is at the level of said surface. The length of the tube is preferably less than the diameter of the tube.

The means defining the liquid flow path from the second tank to the reservoir may define a circuit which includes a third tank, a separator of the cyclone kind (hereinafter called a cyclone) or a battery of cyclones and the reservoir, the arrangement being such that liquid flows around the circuit from the third tank through the cyclone or battery of cyclones and the reservoir back to the third tank, liquid enters the circuit from the second tank and liquid leaves the circuit from the reservoir. The liquid preferably enters the circuit at the third tank.

An example of apparatus embodying the invention will now be described, with reference to the accompanying drawing, which shows diagrammatically a cross-section of the apparatus in a vertical plane.

The apparatus comprises a housing 10 within which there is provided a turntable or other platform 11 forsupporting a workpiece within the housing.

The platform may be provided with means for clamping the workpiece to the platform. A nozzle 12 is swivelably mounted in an aperture in a wall of the housing 10 so that a jet of liquid can be directed from the nozzle onto selected parts of a workpiece when supported on the platform 11. Hoses 13 and 14 are connected to the nozzle for supplying water under high pressure and abrasive particles respectively.

The particles supplied through the hose 14 may be dry or may be a slurry in water.

At the bottom of the housing 10 there is an outlet opening 15 through which water which has been projected at a workpiece and particles of solid mater ial which have been removed from the workpiece can fall into a first tank 16 disposed directly beneath the housing. Near to the top of the tank 16 there is formed by an upper edge of a wall of the tank a weir 17 over which water can flow from the first tank down an inclined trough 18. The water which flows over the weir 17 contains suspended solid particles, both particles of abrasive which were entrained in the jet directed at the workpiece and particles removed from the workpiece. Larger pieces of material removed from the workpiece fall to the bottom of the tank 16. The tank 16 is mounted on wheels so that it can be moved away from the housing 10 and the pieces of solid debris then removed from the tank.Meanwhile, a further tank can be wheeled into position beneath the housing.

A lower end of the trough 18 is disposed within a second tank 19 which is itself disposed within a third, larger tank 20. The third tank has a flat bottom and vertical walls. The second tank has the shape of a cone with the apex of the cone situated near to the bottom of the third tank and an open upper end of the cone situated just below the top of the third tank.

An upper edge of the second tank 19 forms a weir over which water flows from the second tank into the third tank. Water entering the third tank from the second tank may be guided into the third tank at a level below the surface of a body of water in the third yank. The surface of the water in the second and third tanks may be above the level of the upper edge of the second tank.

The apparatus further comprises a reservoir 21 and a separator 22 of the cyclone type connected in a circuit by ducts 23, 24 and 25. For causing water to flow from the third tank 20 to the separator 22 through the duct 23, there is provided a low pressure pump 26. The separator is mounted above a collection vessei 27 into which a slurry of solid particles and water is discharged from the separator. Water overfiows from the vessel 27 back to the third tank 20. Water frorn which particles have been separated by the separator 22 passes down duct 24 to the reservoir 21.

For pumping water from the reservoir 21 to the nozzle 12, there is provided a high pressure pump 28. One or more filters may be provided at the inlet side of the pump 28 to trap any particles still sudpended in the water drawn from the reservoir.

During operation, water flows from the separator 22 through the duct 24 to the reservoir at a rate which is a plurality of times greater than the rate at which water is withdrawn from the reservoir by the pump 28. The excess flow of water passes through duct 25 back to the third tank 20. Usually, water entering the reservoir has a temperature above the ambient temperature and loses heat whilst in the reservoir.

The body of water in the second tank 19 has a cross-sectional area in a horizontal plane which increases with increasing distance above the bottom of the second tank. In the particular example shown, the apex angle of the tank is 90 and the rate of increase of cross-sectional area with distance from the bottom of the tank is proportional to that distance.

Directing means is provided for directing water from the inclined trough 18 into a lower part of the second tank 19. This directing means is in the form of a tube 29 having an open upper end within which the trough terminates and an open lower end, the centre of which is vertically above the apex of the tank. The upper end of the tube 29 is exposed above the surface of the body of water in the second tank and the lower edge of the tube lies below the surface of the water and is spaced from the wall of the tank by a distance greater than the radius of the tube but less than the diameter of the tube. In the particular example shown, the tube is cylindrical.

During use of the apparatus, water in which particles are suspended flows down the trough 18 from the first tank 16 and then flows downwardly through the tube 29 into that part of the second tank which iies below the tube. The water then flows laterally outwardly and upwardly towards the free edge of the wall of the second tank. As the water rises in the second tank, the cross-sectional area available for flow increases and the velocity of flow decreases correspondingly. Particles of solid matter settle from the water onto the wall of the second tank and move down the wall to the bcttom of the tank where they accumulate. During intervals between operation of the apparatus, the accumulated solid matter is removed from the second tank. To this end, an outlet may be provided at the bottom of the second tank.

Any oil or other material capable of floating on water which passes down the trough 18 from the first tank 16 is trapped within an upper end portion of the tube 29. Such floating matter can be removed intermittently from the tube. A pump may be provided to withdraw matter floating on the water in the upper end portion of the tube 29.

Instead of a single separator 22, there may be con nected in circuit with the reservoir 21 and the third tank 20 a battery of separators.

Claims (13)

1. Apparatus for treating the surface of a workpiece and comprising a housing in which there is defined a chamber, means for supporting the workpiece in the chamber, a nozzle for directing a jet of liquid onto the workpiece when supported in the chamber, a reservoir for a supply of the liquid, a pump arranged for pumping liquid from the reservoid to the nozzle, an outlet at the bottom of the chamber, a first tank arranged to receive from the outlet of the chamber liquid which has been directed onto the workpiece and solid matter which has been removed from the workpiece, a second tank arranged to receive from the first tank liquid and solid particles suspended in the liquid and means defining a liquid flow path along which liquid returns from the second tank to the reservoir, wherein the second tank is shaped to contain a body of liquid whereof the area of a cross-section in a horizontal plane in an upper part of the second tank exceeds the cross-sectional area in a horizontal plane in a lower part of the second tank, directing means is provided for directing into the lower part of the second tank liquid from the first tank and the arrangement is such that the liquid flows from the lower part through the upper part before leaving the second tank.

2. Apparatus according to Claim 1 wherein the arrangement is such that liquid flows from an upper part of the first tank into the second tank and that solid matter removed from the workpiece accumulates atthe bottom of the first tank.

3. Apparatus according to Claim 1 or Claim 2 wherein the first tank includes a weir over which the liquid flows from the first tank to the second tank.

4. Apparatus according to any preceding claim wherein the area of a cross-section in a horizontal plane of the body of liquid in the second tank increases gradually with increasing distance above a bottom of the second tank.

5. Apparatus according to Claim 4 wherein the differential coefficient of increase of said area with respect to said distance is approximately proportional to the distance.

6. Apparatus according to any preceding claim wherein an upper edge of a wall of the second tank forms a weir over which the liquid leaves the second tank.

7. Apparatus according to any preceding claim wherein the second tank has the shape of a cone.

8. Apparatus according to any preceding claim wherein the directing means comprises a tube having an open upper end through which liquid flows from the first tank and an open lower end from which liquid flows into the lower part of the second tank.

9. Apparatus according to Claim 8 wherein the second tank contains a body of liquid having an upper surface with an area in the range ten to twenty times the cross-sectional area of the tube.

10. Apparatus according to Claim 9 wherein, at the level of the lower end of the tube, the diameter of the body of liquid in the second tank is within the range two to four times the diameter of the tube.

11. Apparatus according to Claim 9 or Claim 10 wherein the length of the tube is less than the diameter of the tube.

12. Apparatus substantially as herein described with reference to and as illustrated in the accompanying drawing.

13. Any novel feature or novel combination of features disclosed herein or in the accompanying drawing.