GB2158378A

GB2158378A - Hopper fed abrasive blast cleaning machine

Info

Publication number: GB2158378A
Application number: GB08512033A
Authority: GB
Inventors: Francis Joseph Hayes
Original assignee: Individual
Current assignee: Individual
Priority date: 1984-05-12
Filing date: 1985-05-13
Publication date: 1985-11-13
Also published as: GB8512033D0; GB8427887D0; GB2158378B

Abstract

An abrasive blast cleaning machine comprises a pressure vessel (12) for containing abrasive media under pressure and having first inlet (13) for enabling pressurisation of the pressure vessel, an outlet (15) including a valve (30) for controlling the flow rate of abrasive media under pressure out of the pressure vessel, and a second inlet (17) for enabling charging of the pressure vessel with abrasive media from a storage vessel (10) which may be located on top of the pressure vessel. The second inlet (17) is controlled by a valve (14) operated by a pneumatic double-acting cylinder (20) or by means of the pressure utilised to pressurise the vessel (12). When the pressure vessel is pressurised the valve (24) closes the second inlet (17) maintaining the pressure in the pressure vessel (12) but when the pressure is switched off the valve (24) opens inlet (17) allowing abrasive media to flow from said storage vessel (10) into said pressure vessel. Even for a large capacity abrasive blast cleaning machine only a small pressure vessel is required which reduces the cost of manufacturing as well as reducing the overall weight of the machine and improving its handling abilities. <IMAGE>

Description

SPECIFICATION Hopper fed abrasive blast cleaning machine The present invention relates to a portable blast cleaning machine, suitable for on-site abrasive cleaning, which is driven by compressed air.

At present, a variety of different types of equipment are available for abrasive cleaning for a wide variety of industrial applications including wall and stone cleaning, tank and container cleaning, ship or oil rig maintenance,or other industrial applications where a finishing process may be required such as in the forging or casting of metal objects, or simple surface preparation for further processing, for example, painting. In the abrasive blast cleaning industry a wide variety of dry abrasive media may be used for sand or shot blasting including a variety of different grades of sand or grit, steel shot, glass beads or many of a wide variety of other available abrasive materials.

In existing types of portable blast cleaning machines, the abrasive media is stored under pressure in a suitable vessel from which the abrasive under pressure may be introduced into a fast flowing airstream, which carries the abrasive along a suitable "blast" hose, which is terminated in a nozzle of appropriate size to produce the required speed of abrasive. In general terms, the size of the nozzle, i.e.the inside orifice diameter of the nozzle, determines the size of compressor required to deliver an appropriate volume of air per minute.

However, an additional consideration is the size of the blast equipment and, in particular the capacity of the pressure vessel containing the abrasive, since a proportion of the compressed air is required to maintain the pressure vessel at an appropriate pressure. Thus, the larger the pressure vessel the greater the output of compressor required, otherwise there is a limit on the maximum size of nozzle which may be used.For example, in practice it is difficult to get a satisfactory performance from a machine holding 250 Kgs. of abrasive with a blast hose having a 6 mm. nozzle, since too much air is lost in filling the pressure vessel to reach a suitable working pressure and for such a size of nozzle the maximum practical size of machine would have a 50 Kg. capacity only and may therefore require regular topping up with consequent "down time" when the machine cannot be used since it is being refilled. Further, with such conventional type of equipment, since the storage vessel is also the pressure vessel it is not normaily possible to quickly and easily ascertain the amount of material in the pressure vessel and it is therefore difficult to anticipate when the abrasive is likely to be exhausted in order to have readily available fresh supplies on hand.

Further, since with conventional machines the storage vessel is the pressure vessel, it is necessary to manufacture a large and generally expensive container capable of withstanding the pressures likely to be encountered in using the machine, and the manufacture of such large vessels can be an expensive and specialist job and large pressure vessels have a tendency to be relatively heavy.

It is the aim of the present invention to seek to provide an abrasive blast machine which is capable of overcoming the disadvantages of prior art machines as referred to above.

According to the present invention there is provided an abrasive blast cleaning machine comprising: a presure vessel for containing abrasive media having a first inlet for enabling pressurisation of the pressure vessel, an outlet including a valve for controlling the flow rate of abrasive media under pressure out of the pressure vessel and a second inlet for enabling charging of the pressure vessel with abrasive media; a storage vessel associated with the pressure vessel for storing abrasive media and connected to said second inlet for supply of abrasive media to said pressure vessel; and valve means in said second inlet for controlling the charging of the pressure vessel with abrasive media from said storage vessel.

Preferably, the storage vessel is mounted above, possibly directly on top of, the pressure vessel, the pressure vessel being relatively small when compared with pressure vessels of conventional types of blast machines, whilst the storage vessel may be of any suitable size and shape and may in fact be of a similar size to existing types of pressure vessels, i.e. capable of containing up to 300 Kgs. of abrasive. In a possible alternative arrangement, the storage vessel could be mounted alongside the pressure vessel and fed by a venturi-type system which may be actuated to fili the pressure vessel when the machine is switched off.

The storage vessel is preferably opentopped, but may have an appropriate cover provided if desired. The valve controlling the flow of abrasive material from the storage vessel to the pressure vessel is normally closed when the blast machine is in operation and may be controlled pneumatically by means of a double-acting cylinder linked into the controls for pressurising the pressure vessel and the blast nozzle, so that whenthe operator switches the machine off, for example to change position on the job etc., the pressure vessel is refilled automatically from the storage vessel. Thus, when the operator next switches the machine on, possibly only a few seconds later, the pressure vessel has been at least partially refilled.This "topping-up process" may be continued almost indefiniteiy with an appropriately sized hopper as a storage vessel, there being no con straints, other than manageability, on the size of the storage vessel, since it is not required to be utilised as a pressure vessel. Thus, the storage vessel may be of simple and iight weight construction, typically a machine according to the present invention would be approximately 60% of the weight of a conventional machine of similar capacity.

A further advantage of the machine according to the present invention is that it may be utilised with any nozzle size from, for example, 4 mm. to 15 mm. without modification, due to the small size of the pressure vessel, without having to modify the pipework or valves, whereas conventional machines are limited to a few millimetres difference between nozzles. In addition, the machine of the present invention is much more economical in its use of abrasive since the operator can detect more quickly a misadjustment of the abrasive flow valve and since there is less surface area for condensation to manifest itself in the pressure vessel.On this latter point, it should be noted that the amount of abrasive needed is generally proportional to the dryness of the abrasive used and if any clots of abrasive occur in the abrasive flow control valve, then this may have to be opened further to allow such blockages to be removed, thereby wasting the abrasive media.

It will be apparent that in view of the versatility of the machine it will be ideal for the plant hire market, where hire contractors would only need to stock a single machine to offer a comprehensive service whereas at present a wide range of machines may be required to be held in stock. Similarly, blast cleaning contractors would only require a single relatively inexpensive machine whereas for a range of uses they may have required several more expensive machines to offer a comprehensive service.

The present invention will now be described further with reference to the accompanying drawings, in which: Fig. 1 is a perspective view of the possible appearance of a hopper fed machine; Fig. 2 shows various aspects of the construction and operation of a conventional abrasive blast machine; Fig. 3 illustrates schematically a blast machine according to the present invention and illustrates the relative size of the pressure vessel of the machine according to the present invention when compared to a conventional machine; Fig. 4 illustrates in more detail the arrangement of a blast machine according to the present invention; and Figs. 5 and 5a illustrate alternative valve arrangements for the blast machine according to the present invention.

Referring firstly to Fig. 1, a general impression of the arrangement of the component parts of the machine according to the present invention can be ascertained together with typical preferred relative sizes of the pressure vessel 1 2 and storage hopper 10. In general, the storage hopper is mounted on a supporting frame which may be provided with a pair of wheels to enable relatively easy manoeuvrability of the machine and below this storage hopper 10, the pressure blast vessel 1 2 is mounted and is provided with associated pipework for supply of compressed air to presurise the pressure vessel and also to pick up pressurized abrasive from the pressure vessel for use in blast cleaning purposes.

Referring now to Fig. 2, a typical arrangement of a blast machine is shown, with the arrangement as shown in Fig. 2(a) illustrating the machine in operation with the pressure blast vessel 50 at least partially filled with abrasive 51 under pressure, which is mixed into a fast flowing airstream passing the base of the pressure vessel at a suitable mixing point normally controlled by an abrasive flow control valve 52. Initial charging and filling of the pressure vessel 50 with abrasive media is carried out utilising a valve 53 provided in the upper portion of the pressure vessel 50 as shown in more detail in Figs. 2(c) and 2(d) and may typically be controlled by the switching on or off of the air supply to the machine.

Figs. 2(b) and 2(d) illustrate the conventional type machine when empty and with the valve 53 open and ready for refilling of the pressure vessel 50.

Referring now to Fig.3(a), the arrangement according to the present invention is illustrated schematically. It can be seen that a relatively small pressure vessel 1 2 is utilised and an approximate relative sizing of the machine of the present invention is shown from a comparison of Fig. 3(c) for a similar prior art machine shown in Fig.3(b). It can be appreciated that the relatively large volume of the storage hopper 10 of the machine of the present invention is unpressurised and therefore may be made by relatively simple and lightweight construction without any need for the manufacture of a large pressurised vessel 50 which may effect a considerable saving in manufacturing costs and also maintains a low centre of gravity which assists in manoeuvrability of the machine.

As illustrated schematically in Fig.3(a), and in more detail in Fig. 4, a suitable valve arrangement may be provided to enable remote operation of the blast machine including automatic refilling of the vessel from the storage hopper when the machine is switched off, even for a few moments. Alternatively, a simple arrangement as used in prior art devices as shown in Fig. 2 could be utilised for refilling the pressure vessel 1 2.

Referring in more detail to the operation of the device of the present invention, it can be seen from Fig. 4, that when the main pressure control valve 14 in the air supply pipe 1 6 is closed, thereby preventing supply of pressurised air to the blast vessel 1 2 or the blast hose 18, a by-pass valve 1 9 supplies air under pressure along line 21 to a doubleacting cylinder 20 mounted in the storage vessel.

The double-acting cylinder 20 displaces a shaft 22, connected thereto, downwardly so as to cause a valve member 24, connected at the lower end thereof to open an inlet opening between the storage hopper 10 and the pressure vessel 12, to allow abrasive media in the storage hopper to flow from the storage hopper into the pressure vessel 1 2. When the main air supply valve 14 is switched on, the double-acting cylinder 20 is caused to retract the shaft 22 and valve 24 to thereby close the inlet opening and the pressure vessel 1 2 is pressurised directly from the main air line and the abrasive media under pressure is mixed with the air in the blast hose 18 via an abrasive control valve 30 in conventional manner.

Since only a small pressure vessel 1 2 is required to be pressurised at each switching on of the machine, the machine, as described, is more efficient in terms of its use of compressed air and also in respect of the quantity of abrasive used, due to the reduced tendency for condensation to occur in the pressure vessel. However, although the size of the pressure vessel has been reduced, the utility of the machine is in no way impaired, due to the provision of a large storage hopper, which could if desired be refilled during use without interrupting the operation of the blast machine, and indeed if desired could be mounted remotely from the blast machine and supplied along a flexible hose or the like, as required.The storage hopper can be of any suitable size ranging from a similar size to that of the pressure vessel up to several times the size of the pressure vessel, or a single storage hopper could be connected, suitably by flexible hoses to several pressure vessels which could each function simultaneously and independently of one another. Thus, the present invention provides an abrasive blast machine which is versatile, relatively inexpensive and easy to manoeuvre and efficient in its use of compressed air and abrasive media.

Figs. 5 and 5a illustrate alternative arrangements for the valve 24 which obviate the need for the double-acting cylinder 20 and shaft 22 with a consequential simplification of the control valve required to operate the unit.

With regard to this arrangement the valve 24 is replaced by a pop-up valve of the type utilised in conventional arrangements and as described in Fig. 2, and in this instance the popup valve 24' is located in the inlet opening of the vessel 12' and is operated by supplying air pressure along the pipe 31 to urge the pop-up valvo 24' upwardly into engagement with a valve seat 32. The pressure vessel 12' is simultaneously pressurised by means of the same outlet pipe 31 and the pressurisation of the pressure vessel 12' maintains the pop-up valve 24' in engagement with the valve seat 32 during operation of the blast machine.When the blast machine is switched off and the pressure in the pressure vessel falls, the pop-up valve 24' falls back onto the open upper end of the inlet pipe 31 so that the abrasive media is allowed to flow from the storage hopper into the pressure vessel automatically filling same. When the pressure is again applied the operation proceeds as previously described.

The valve seat 32 may be of polyurethane or other suitable plastics material or of natural rubber and such may be in the form of a collar or '0' ring mounted in a metal collar.

Whichever type of seat 32 is utilised, it is mounted in a sealing manner on the pressure vessel 1 2 and then connected directly to the storage hopper or indirectly via a supply hose or pipe.

In order to ensure a good seating of the pop-up valve on the valve seat 32 it is necessary to ensure that the valve seat is clear of abrasive when the pop-up valve 24' is lifted on to its seat 32. There are a variety of ways in which the seat can be cleared of abrasive as will be described later but, as shown in Fig. 5, a baffle is provided in the neck of the pressure vessel in the region of the pop-up valve 24' and valve seat 32 so that a blast of air at inlet 33 is directed by baffle 34 into the region of the valve seat to clear the valve of abrasive media simultaneously with the lifting of the pop-up valve 24 upon the application of pressure at inlet 31.

The air inlet 33 preferably leads to a circumferential channel 35 defined by a portion of the wall of the pressure vessel and baffle 34 so as to direct the air towards the valve seat area from all directions.

As mentioned above, a variety of alternative means can be utilised to clear the valve area of abrasive, namely the compressed air could be fed through the body of the valve seat for the popup valve by drilling appropriate holes in the valve seat to direct air into that region, or air may be fed through holes provided in the pop-up valve itself. Alternatively, a circular vessel could be mounted in the pressure vessel or hopper similar to a gas ring having a plurality of jets around the circumference thereof for directing air against the valve seat area, or finally one or more ports could be provided so positioned to direct blasts of air into the valve seat area.

One problem which has been identified which can occur occassionally is that the popup valve 24' may be pushed through the inlet opening and in order to overcome this possibility, as shown in Fig. 5a, a flange 38 may be provided, on the edge of the opening in the bottom of the storage hopper 10', to effectively narrow the inlet opening without significantly reducing flow or introducing turbulence in the flow of abrasive media into the vessel 12'. Further, the flange 36 assists in positioning and locating the valve seat 32.

It should also be appreciated that this arrangement could either be operated automatically or manually in order to refill the pressure vessel from the storage hopper as required and the control of the valves can be effected on the machine or alternatively remotely from the machine, for example on the blast hose, so that the operator can operate the device even if he is some distance from the blast machine.

Claims

1. An abrasive blast cleaning machine comprising: a pressure vessel for containing abrasive media having a first inlet for enabling pressurisation of the pressure vessel, an outlet including a valve for controlling the flow rate of abrasive media under pressure out of the pressure vessel and a second inlet for enabling the charging of the pressure vessel with abrasive media; a storage vessel associated with the pressure vessel for storing abrasive media and connected to said second inlet for supply of abrasive media to said pressure vessel; and a valve means in said second inlet for controlling the charging of the pressure vessel with abrasive media from said storage vessel.

2. An abrasive blast cleaning machine as claimed in claim 1, wherein the storage vessel is mounted above the pressure vessel whereby said abrasive media is gravity fed in said storage vessel into said pressure vessel through said second inlet.

3. An abrasive blast cleaning machine as claimed in claim 1, wherein said storage vessel is mounted alongside or remote from said pressure vessel and is connected to said pressure vessel by means of a supply pipe or hose.

4. An abrasive blast cleaning machine as claimed in claim 1, wherein said storage vessel is connected to a plurality of pressure vessels by supply pipes or hoses.

5. An abrasive blast cleaning machine as claimed in any preceding claim, wherein the storage vessel is open-toppped or has a removable cover enabling the storage vessel to be refilled without interrupting the use of the blast cleaning machine.

6. An abrasive blast cleaning machine as claimed in any preceding claim, wherein the valve member for controlling the flow of abrasive media from the storage vessel to the pressure vessel is operatively connected to a pneumatically-controlled double-acting cylinder, which, in use, functions to open the valve to allow abrasive media to flow into the pressure vessel when the machine is switched off.

7. An abrasive blast cleaning machine as claimed in any of claims 1 to 5, wherein the valve member for controlling the flow of abrasive media from the storage vessel into the pressure vessel is a pop-up valve, which functions such that, in use, when the pressure vessel is pressurised by means of compressed air flowing in through said first inlet, said popup valve closes said second inlet and that when the machine is switched-off said pop-up valve falls back onto the open end of said first inlet, thereby automatically opening said second inlet allowing abrasive media to flow into said pressure vessel from said storage vessel.

8. An abrasive blast cleaning machine as claimed in any preceding claim, wherein means are provided for clearing abrasive media from the region of said second inlet of said pressure vessel upon switching on of the machine and pressurisation of the pressure vessel in order to ensure a sealing fit of said valve member in said second inlet.

9. An abrasive blast cleaning machine as claimed in claim 8, wherein said means for clearing the region of said second inlet comprises one or more inlet openings for directing blasts of air to the region of said second inlet opening to clear abrasive media from the region of said second inlet to enable the valve member to sealingly close the second inlet.

10. An abrasive blast cleaning machine as claimed in claim 8, wherein said means for clearing abrasive media from said second inlet comprises a further inlet opening communicating with a peripheral channel, and a baffle for directing a blast of air from said further inlet into the region of said second inlet to clear the region of abrasive media to enable the valve member to sealingly close said second inlet.

11. An abrasive blast cleaning machine as claimed in claim 8, wherein said means for clearing said second inlet opening of abrasive media comprises a further inlet communicating with a teroidal member having a plurality of openings to direct blasts of air into said region of said second opening to clear said region of abrasive material to enable the valve member to sealingly close said second inlet.

1 2. An abrasive blast cleaning machine as claimed in claim 8, wherein openings are provided in said pop-up valve and/or in a valve seat, which is engaged by said pop-up valve, through which openings blasts of compressed air may be directed to the region of said second inlet to clear abrasive media from the region of said second inlet to enable said valve member to sealingly close said second inlet.

1 3. An abrasive blast cleaning machine as claimed in any of claims 1 to 11, wherein a valve seat is provided in said second inlet for mutual engagement by said valve member, said valve seat being formed of a collar located between said storage vessel and said pressure vessel.

14. An abrasive blast cleaning machine as claimed in claim 13, wherein said valve seat comprises a plastics material collar.

1 5. An abrasive blast cleaning machine as claimed in claim 13, wherein said seat comprises a natural rubber collar.

16. An abrasive blast cleaning machine as claimed in claim 13, wherein said seat comprises a metal collar supporting an O-ring.

1 7. An abrasive blast cleaning machine as claimed in any of claims 13 to 16, wherein a flange is provided at the lower end of the storage vessel which extends partially into said second inlet in order to slightly narrow said second inlet to minimise the possibility of the valve member passing therethrough, in use.

1 8. An abrasive blast cleaning machine as claimed in any preceding claim, wherein abrasive media under pressure extracted from said outlet of said pressure vessel and through said valve is mixed with compressed air and supplied to a blast hose terminated in a nozzle for directing the abrasive media and air mixture at an article to be cleaned.

1 9. An abrasive blast cleaning machine as claimed in any preceding claim, wherein a water separation device is included in the air supply to said blast cleaning machine to remove moisture from said compressed air to minimise condensation in the pressure vessel.

20. An abrasive blast cleaning machine as claimed in any preceding claim wherein pneumatic control means are provided for enabling control of the functioning of the blast machine remotely therefrom.

21. An abrasive blast cleaning machine as claimed in any preceding claims and substantially as herein described with reference to Figs. 1, 3a, 3c, 4, 5 and 5a of the accompanying drawings.