GB2367777A

GB2367777A - Blast processing using turbine blowers

Info

Publication number: GB2367777A
Application number: GB0024892A
Authority: GB
Inventors: Peter Reynolds
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-10-10
Filing date: 2000-10-10
Publication date: 2002-04-17
Also published as: AU2001295713A1; WO2002030621A3; WO2002030621A8; GB0024892D0; WO2002030621A2

Abstract

Closed-circuit blasting apparatus comprises a plurality of turbine blowers (21, fig. 4) arranged side-by side, a reservoir 19 for blast medium, a cyclone 16 for separating used blast medium and feeding it into the reservoir 19, all mounted in a hand portable housing. A filter 18 lies between the cyclone 16 and the turbines. By using a variable air inlet (263, fig. 4) for the turbines the action of the cyclone 16 can be controlled. The turbines may be mounted in a dome (24, fig. 4) removably attached to the remainder of the housing. Rotation of the dome alters the amount of air entering the turbines. Air is supplied by the blowers to a hand tool having a Venturi device to entrain the blasting medium. A brush mounted on an elastic collar surrounds the exit of the hand tool. The blast medium may be pellets of non-woven fabric, some of which are impregnated with a substance (e.g. polish) which transfers to the workpiece upon impact. Also disclosed is a shoulder mounted recycling container (figs. 6 and 7).

Description

TITLE :"BLAST-PROCESSING"

FIELD OF THE INVENTION This invention relates to blast-processing.

Some embodiments of the invention may be blast-processing apparatus of the type that includes a blower head mounted on a container that can have wheels and has hoses attached for delivery of air, sand or any suitable blast medium, and for water injection when required, all of which attach to a gun-type hand-held tool by suitable hoses for delivery of selected mixture to the surface to be treated.

BACKGROUND Sandblasters of this type are well-known in the prior art but these require a compressed air supply, or high pressure water supply or use a spinning wheel system.

It is difficult to use such systems for mobile cleaning tasks and the size of the equipment required makes manoeuvrability difficult and a large vehicle is required for transportation of such bulky equipment.

Sand-blasting process and apparatus generally are well-known. There are two main kinds. One, of minor importance here, utilises high-pressure water, e. g. from a mains supply via a pressuriser, essentially for high-pressure water washing, with the possibility to add a sand pickup facility to convert from water washing to sand-blasting, where the water acts as a vehicle to pick up and convey the sand. The other uses high-pressure air as the vehicle, called"air-blasting", and a reservoir of sand, and possibly a reservoir of water, where the air acts as the vehicle for the sand alone in"dry-blasting", and for the water in addition to the sand in"wet-blasting".

If the sand is collected at the workpiece to be used again (recycled), the method is called"the closed-circuit method"; if the sand is not collected at the workpiece but is

lost, the method is called"the lost-sand method". The more important concern here is with air-blasting, wet or dry, and mainly closed-circuit.

Usually, there is a hand-held blasting tool, connected by hoses to receive air, as the vehicle, from the reservoir of a high-pressure air compressor, and sand drawn at will from a reservoir and possibly water drawn at will from a reservoir or the mains, both into the hand-held tool by Venturi-type action of the air. This is very cumbersome, particularly the high-pressure air compressor which may need a diesel engine to operate it as well as a bulky reservoir.

In these days of consciousness of silicosis, a copper mineral may replace the sand as the abrasive medium. Plastics pellets have also been used in place of the sand as an abrasive medium.

THE INVENTION The present inventor has noted that much of the difficulty arises because of the need to use such high-pressure air compressors. He has also noted that these compressors utilise a pump which operates sequentially, by repeatedly trapping a volume of air from its low-pressure inlet side and transposing this to its high-pressure outlet side, usually by means of a piston-cylinder arrangement or a rotary shutter arrangement. Since the compressed air reservoir of these compressors is at a very high pressure, this has to be very strong, consequently very heavy and bulky and therefore awkward. He sought for a solution which did not require such heavy duty air compression. After much experiment, he realised that it should be possible to use, instead, a much lower compression device, e. g. a turbine, which does not sequentially trap volumes of air but operates continuously, with a somewhat fan-like action. He experimented with suction turbines used for vacuum cleaners, inverting them to make

use of their exhaust air rather than their input side, so as to form blowers. He found these worked satisfactorily, even more so if he used a plurality of them in parallel, even better if their outputs were arranged to reduce turbulence, as by feeding substantially in a straight line through into a supply hose for the hand-held tool, and preferably by having the inside of the hose somewhat smoothed to reduce turbulence; and much better if there is a much larger cross-sectional area, than with the prior art apparatus, for the usual Venturi or a like device of the hand-held tool at its injection nozzle and/or at its narrowest part, and/or for the hand-held tool itself at its exit mouth (which also reduces turbulence).

His initial apparatus had three such turbines arranged beside one another with the hose feeding off at right angles to their common exhaust flow direction, but the efficiency (useful power) increased by 50% when the hose was rearranged to feed off in line with the exhaust flow, more especially with a dome arrangement such as that described below. Generally, turbulence-reduction measures, e. g. avoidance or minimising of obstructions, ribs, ridges and comers, contributed noticeably to increases in efficiency. Another such measure utilises, in place of a conventional Venturi in the hand tool, a parallel-sided (straight-bore) tube with an injection nozzle, somewhat like a Bunsen burner.

Compared with the heavy duty prior air compressor arrangements, with their diesel engines, embodiments of the present invention can use minuscule power, e. g. only one kW per turbine for a heavy duty blaser. In fact, they are light and neat rather than bulky and cumbersome, much cheaper and readily transportable and their hoses are not dangerous or liable to cause difficulties as with the prior arrangements.

Further, they do not need an intervening air reservoir, as do the high-pressure air compressors.

A further feature is a brush surrounding the exit mouth of the hand tool to maintain substantially sealing contact with the workpiece in order to contain the abrasive medium being blasted at the workpiece, the brush preferably being mounted to the workpiece on an elastic (e. g. medium hard rubber) collar. With this, the stream of abrasive medium which is usually centred within the contact area with the workpiece can be directed onto the whole of that area simply by tilting the hand tool, e. g. in a circle around its central position, without changing the position of the brush contact.

According to respective aspects of the invention, there are provided: 1. Blast-processing apparatus, characterised in that it comprises a hand-held blasting tool adapted to use substantially lower air pressures than the known apparatus.

2. Blast-processing apparatus, characterised in that it comprises a hand-held blasting tool with a Venturi or the like that is of substantially greater cross-sectional area than in the known apparatus.

3. Blast-processing apparatus, characterised in that it comprises a hand-held blasting tool with an outlet mouth that is of substantially greater cross-sectional area than in the known apparatus.

4. Blast-processing apparatus, characterised in that it comprises a source of pressurised air adapted to produce air for feeding to a hand-held blasting tool at a substantially lower pressure than in the known apparatus.

5. Blast-processing apparatus, characterised in that it adapted to provide air to a hand-held blasting tool at substantially lower air pressures than the known apparatus.

6. Blast-processing apparatus, characterised in that it is adapted to operate without the use of a high-pressure air compressor.

7. Blast-processing apparatus, characterised in that it does not contain a pressured air reservoir.

8. Blast-processing apparatus, characterised in that it comprises ; tow-pressure, high-volume turbine means for providing air to a hand-held blasting tool.

9. Blast-processing process corresponding to points 1 to 8.

In place of sand, there may be provided any other suitable abrasive medium.

According to another aspect of the invention, there may be provided, in place of sand, a processing medium that is not abrasive, e. g. a polishing medium, e. g. comprising pellets of non-woven fabric. According to another aspect of the invention, some particles of the processing medium may be different from others, e. g. some (perhaps one in ten) of the fabric pellets may be impregnated with a polish (e. g. liquid) which transfers to the workpiece upon impact and is then used by subsequent un-impregnated pellets to polish the workpiece. Again, the processing medium might comprise glass beads, for peening or work-hardening.

Embodiments of this invention are intended to provide a sandblaster that is easily manoeuvred and simple in use.

Accordingly, they provide a sandblaster that can be conveniently wheeled close to the work area and does not require a separate supply of compressed air or a water supply from either mains tap or tank as in the case of a high-pressure air washer combination. This sandblaster can also re-circulate medium for re-use if required.

Furthermore, water from a nearby small container can be drawn into the air/medium mix for the purpose of avoiding dust particles from the workpiece entering the

surrounding atmosphere, though in such circumstances recycling is not normally possible.

DESCRIPTION RELATING TO THE DRAWINGS Preferred embodiments of the invention will now be described with reference to the accompanying drawings, in which: FIGURES 1 and 2 are a side and a top schematic cross-sectional view respectively of a hand held gun embodying the invention.

FIGURE 3 is a schematic perspective transparent side view of the wheeled medium container unit on top of which is the self-contained air supply unit, which together form a housing that embodies the invention; also shown are the hose connections for recycling.

FIGURES 4 and 5 are a side and a top schematic transparent view respectively of the air supply unit dome.

FIGURES 6 and 7 are a schematic perspective side view and transparent side view respectively of a separate recycling medium container that can be hung over the shoulder of the operator for use in difficult areas.

FIGURES 8 and 9 are views like Figures 1 and 2 respectively of the hand tool showing dimensions of one example, see table in ensuing description.

FIGURE 10 is a view like Figure 3 of the wheeled medium container unit, i. e. the housing without the removable dome, showing dimensions of one example, see table in ensuing description.

FIGURE 11 is a transparent side view of the dome, showing dimensions of one example, see table in ensuing description.

FIGURE 12 is a schematic view of particles of a mixed medium.

Reference will now be made by way of example to the accompanying drawings. In these are at, a closed hollow arrowhead represents the flow of the abrasive medium, an open arrowhead represents flow of air, and a solid arrowhead represents flow of air/medium mix.

As shown in Figure 1, the gun comprises an air nozzle 7 that can be turned to allow entry of the medium only or of the medium and water to form a medium/water mix, it can also be positioned so as completely to prevent entry of medium and medium/water into the air stream. The nozzle 7 fits into the gun housing 10 and is held in position by screw 11, which runs in a channel 12 thus allowing the nozzle 7 to be turned to one of three selectable positions, marked a, b, c respectively, first position is medium/water mix, second position is off, third position is medium only, in this order; in another embodiment, screw 11 can be turned to intermediate positions to vary the amount of medium or medium/water; in another embodiment, the proportion of water to medium can be selected by screw 11.

Air entering channel 1 is then restricted through the narrower orifice 243 and enters the venturi chamber 2 and then enters into nozzle 8 and in so doing creates a reduced pressure in chamber 2 that pulls medium into channel 5 and, when selected, water into channel 6, the mixture is forced into channel 3 and strikes the surface of workpiece 261 to be treated.

Escape is restricted by brush head 9 and spent medium is guided back through the outer channel between nozzle 8 and gun housing 10 to outlet 4 and returned to medium container 19 via return hose 15.

As shown in Figure 3, air 241 is pumped, by using one, two or three vacuum cleaner turbines 21 as blowers in power head Figure 4, through supply hose 13 to

nozzle 7, Figure 1. By channelling the air into the domed top 24 of the power head Figure 4, air is guided directly towards the outlet 25 with very little turbulence and this creates a very powerful blower action delivering a high volume/rate of air that is sufficiently strong to create the venturi effect in the gun, Figure 1, which in turn draws a high enough quantity of medium along channel 5 into the airstream in channel 1 to strike the surface of workpiece 261 with enough impact to blast, clean or otherwise process the workpiece 261 efficiently.

The container unit in Figure 3 holds the medium 201 in the lower chamber 19, medium 201 is channelled downwards to outlet nozzle 32 and the flow is controlled by fixed air channel 20 that has a 45-degree angle at the bottom that acts as a baffle to restrict flow of the medium 201 and also allows air to be drawn into delivery tube 14, this combination helps to avoid blockages caused by oversupply of medium 201 into hose 14.

As shown in Figures 3 and 4, the triple motor blower can be controlled by two switches 22 and 23, switch 22 operates two motors 21, while switch 22 operates a third motor, so that the operator can use one, two or three motors 21 to suit his/her requirements. The majority of the air 241 drawn into the turbines is to be drawn through the side inlet vents 263 on base 26, as it is desirable that only some air is drawn through the bottom of the base unit 26 for the purpose of separating fine dust particles from returned air and medium 245, and for this purpose a chamber 16 is used below the base unit 26, fitted with a coned top and bottom, the air and medium mix 245 is forced back into this chamber by the flow recirculated due to the brush head 9 in Figure 1. The chamber 16 is designed to guide the returned mixture in a tangential circular motion, the heavier medium 201 falls to the bottom for re-use and

the lighter debris and dust are drawn into the upper chamber 17 above which is fitted a filter 18, immediately below base unit 26, to protect the turbines 21. Base unit 26 is fitted with an inner ring 262 that can be turned so as gradually to restrict air intake from the side inlets to suit operator requirements should more suction be required in chamber 16 for heavier debris separation.

As shown in Figure 6, the portable medium re-cycling container 27 can be used when operating in areas in which the base unit in Figure 3 would not be convenient.

Such a situation could be when using a ladder or scaffolding. The container 27 can be used with a shoulder strap 31, outlet nozzle 28 supplies medium to hose 14 Figure 3, returned medium enters through screw fitting 29 for re-use, the power of the return air carries dust and debris into a filter bag 30 for later disposal. Container 27 acts as a blower separator: the returning air/medium mix 245 blows into the air-filled upper part of container 27 and most of the air can only escape through outlet 301 to filter bag 30, and therefore carries dust and debris with it to bag 30, while the heavier medium 201 sinks to the bottom. The action here, as also at the bottom of the container unit shown in Figure 3, can be seen clearly in conjunction with the action of baffle tube 20. In this embodiment, the operator can also detach power head Figure 4, and operate it as a stand-alone unit, e. g. by fitting a longer air hose 13, Figure 3, it is possible to operate some distance from the power head.

Blast-processing apparatus Figure 3 comprises turbine blower means 21 to provide air will to 41 as a vehicle for a blast-processing medium 201. It comprises a hand tool Figure 1 adapted to use, as a vehicle for a blast-processing medium 201, air 241 provided by turbine blower means Figure 4. It comprises a plurality of turbine blowers 21 arranged to act side by side. It comprises a reduced turbulence path 242

for air 241 blown from turbine blower means 21 as said air vehicle. Said path 242 is arranged to feed said air vehicle 241 substantially in a straight line 242 from said turbine means 21 through to the inlet 25 of a supply hose 13 adapted to use said air vehicle 241. It comprises a hand tool Figure 1 adapted to use said air vehicle 241 provided by said turbine blower means 21, the hand tool Figure 1 having a Venturi or like device 7,8 to entrain blast-processing medium 201, said device 7,8 having a substantially increased cross-sectional area that provides the adaptation. Said cross-sectional area 243 or 244 is at least four times as large as a standard or conventional such area for such a tool. Preferably, said cross-sectional area 243 or 244 is at least 16 times as large as a standard or conventional such area for such a tool. A said cross-sectional area 243 is at the mouth 243 of an injection nozzle 7 into said device 7,8. Another said cross-sectional area 244 is at an exit orifice of nozzle 8 of said device 7,8. Typically, in the prior art, cross-sectional area 243 is circular with diameter 2 to 3 mm, and the cross-sectional area 244 is circular with diameter 6 to 7 mm.

The apparatus comprises a hand tool Figure 1 to apply said blast-processing medium 201 to a workpiece 261, with a brush online surrounding the exit mouth 252 of the hand tool Figure 1 to maintain substantially sealing contact (at 252) with the workpiece 261 in order to contain the medium 201, the brush 9 being mounted to the hand tool Figure 1 on an elastic collar 99. The apparatus is adapted for closed-circuit operation (by use of said brush 9) and for the blast-processing medium 201 being returned to be returned under pressure due to said air vehicle 241. The returned air/medium mix 245 is returned under said pressure into a cyclone separator 254. The apparatus comprises variable air inlet means 262,263 to the turbine means 21, and is

arranged for variation of the air inlet 262, 263 to the turbine means 21 to control the action of the cyclone separator 254. The apparatus is adapted for closed-circuit operation and comprises filter means 18 between a returned blast-processing medium region 17 and the turbine means 21. It comprises a reservoir 19 for the blast-processing medium 201 at a bottom exit 32 of which reservoir 19 is provided a baffle 20 to help prevent the medium 201 from blocking the exit 32, said baffle 20 being provided with an air conduit 253 by-passing the medium 201 to help prevent the medium 201 from blocking the exit 32.

The apparatus comprises a housing, Figure 3, that can be moved around by hand comprising a reservoir 19 for blast-processing medium 201, a returned blast-processing medium region 16 provided with a cyclone separator 254 arranged to feed the separated medium 201 to the reservoir 19, said turbine means 21, and filter means 18 between the separator 254 and the turbine means 21. Said turbine means 21 are mounted in a dome Figure 4 removably mounted into said housing Figure 3.

The hand tool Figure 1 adapted to apply the blast-processing medium 201 has a member 7 rotatable to vary the amount of the medium 201 able to be entrained in the tool Figure 1.

The blast-processing method described particularly comprises use of turbine blower means 21 to provide air as a vehicle for a blast-processing medium 201. In one embodiment, this medium 201 comprises pellets 270 of non-woven fabric, as exemplified in Figure 12. In another embodiment, some particles 271 of this processing medium 201 are different from others 270. Said different particles 271 are impregnated with a substance, e. g. polish, which transfers to the workpiece 261 upon impact therewith in the course of the blast-processing.

The following references in Figures 8, 9, 10 and 11 have the dimensions in mm :

Fig. 8 112= 33. 0 123 = 9. 0 142 = 60. 0 100 = 10. 0 113= 46. 0 124 = 35. 0 143 = 120. 0 101 = 60. 0 114= 56. 0 125 = 304. 0 102= 9. 0 115= 10. 0 126= 209. 0 Fig. 11 103= 16. 0 116= 14. 0 127= 160. 0 130= 60. 0 104= 3. 0 117= 16. 0 128= 40. 0 131= 330. 0 105= 16. 0 118= 76. 0 129= 10. 0 132= 80. 0 106= 16. 0 133= 70. 0 107 = 9. 0 Fig. 9 Fig. 10 134 = 140. 0 108= 13. 0 119= 69. 0 138= 320. 0 135= 320. 0 109= 35. 0 120= 49. 0 139= 100. 0 136= 40. 0 110= 40. 0 121= 195. 0 140= 790. 0 137= 60. 0 111= 26. 0 122= 9. 0 141= 100. 0

It will be apparent to one skilled in the art, that features of the different embodiments disclosed herein may be omitted, selected, combined or exchanged and the invention is considered to extend to any new and inventive combination thus formed.

Claims

CLAIMS 1. Blast-processing apparatus, characterised in that it comprises turbine blower means to provide air as a vehicle for a blast-processing medium.

2. Blast-processing apparatus, characterised in that it comprises a hand tool adapted to use, as a vehicle for a blast-processing medium, air provided by turbine blower means.

3. Apparatus as claimed in claim 1 or 2, characterised in that it comprises a plurality of turbine blowers arranged to act side by side.

4. Apparatus as claimed in any one of claims 1 to 3, characterised in that it comprises a reduced turbulence path for air blown from turbine blower means as said air vehicle.

5. Apparatus as claimed in claim 4, characterised in that said path is arranged to feed said air vehicle substantially in a straight line from said turbine means through to a supply hose adapted to use said air vehicle.

6. Apparatus as claimed in any one of claims 1 to 5, characterised in that it comprises a hand tool adapted to use said air vehicle provided by said turbine blower means, the hand tool having a Venturi or like device to entrain blast-processing medium, said device having a substantially increased cross-sectional area.

7. Apparatus as claimed in claim 6, characterised in that said cross-sectional area is at least four times as large as a standard or conventional such area for such a tool.

8. Apparatus as claimed in claim 6, characterised in that said cross-sectional area is at least 16 times as large as a standard or conventional such area for such a tool.

9. Apparatus as claimed in any one of claims 6 to 8, characterised in that a said cross-sectional area is at the mouth of an injection nozzle into said device.

10. Apparatus as claimed in any one of claims 6 to 9, characterised in that a said cross-sectional area is at an exit orifice of a nozzle of said device.

11. Apparatus as claimed in any one of claims 1 to 10, characterised in that it comprises a hand tool to apply said blast-processing medium to a workpiece, with a brush surrounding the exit mouth of the hand tool to maintain substantially sealing contact with the workpiece in order to contain the medium, the brush being mounted to the workpiece on an elastic collar.

12. Apparatus as claimed in any one of claims 1 to 11, characterised in that it is adapted for closed-circuit operation and for the blast-processing medium being returned to be returned under pressure due to said air vehicle.

13. Apparatus as claimed in claim 12, characterised in that the returned medium is returned under said pressure into a cyclone separator.

14. Apparatus as claimed in any one of claims 1 to 13, characterised in that it comprises variable air inlet means to the turbine means.

15. Apparatus as claimed in claim 14, when appendant to claim 13, characterised in that it is arranged for variation of the air inlet to the turbine means to control the action of the cyclone separator.

16. Apparatus as claimed in any one of claims 1 to 15, characterised in that it is adapted for close-circuit operation and comprises filter means between a returned blast-processing medium region and the turbine means.

17. Apparatus as claimed in any one of claims 1 to 16, characterised in that it comprises a reservoir for the blast-processing medium at a bottom exit of which reservoir is provided a baffle to help prevent the medium from blocking the exit, said

baffle being provided with an air conduit by-passing the medium to help prevent the medium from blocking the exit.

18. Apparatus as claimed in any one of claims 1 to 17, characterised in that it comprises a housing that can be moved around by hand comprising a reservoir for blast-processing medium, a returned blast-processing medium region provided with a cyclone separator arranged to feed the separated medium to the reservoir, said turbine means, and filter means between the separator and the turbine means.

19. Apparatus as claimed in claim 18, characterised in that said turbine means are mounted in a dome removably mounted to the remainder of said housing.

20. Apparatus as claimed in claim 19, characterised in that said dome is rotatable on said remainder of the housing to control air inlet to the turbine means.

21. Apparatus as claimed in any one of claims 1 to 20, characterised in that it comprises a hand tool adapted to apply a blast-processing medium, the tool having a member rotatable to vary the amount of the medium able to be entrained in the tool.

22. Apparatus as claimed in any one of claims 1 to 21, characterised in that it comprises a portable unit comprising a blast-processing medium reservoir.

23. Apparatus as claimed in claim 22, characterised in that the portable unit comprises a separator for an air/blasting-medium mix and is adapted for use in the closed-circuit method of blast-processing.

24. Blast-processing apparatus substantially according to any embodiment hereinbefore described.

25. Blast-processing apparatus substantially according to any embodiment hereinbefore described with reference to the accompanying drawings.

26. Blast-processing method, characterised in that comprises use of turbine blower means to provide air as a vehicle for a blast-processing medium.

27. Blast-processing method substantially according to any embodiment hereinbefore described.

28. Blast-processing method substantially according to any embodiment hereinbefore described with reference to the accompanying drawings.

29. Blast-processing method, characterised in that comprises a blast-processing medium comprising pellets of non-woven fabric.

30. Method as claimed in claim 29, characterised in that some particles of the processing medium are different from others.

31. Method as claimed in claim 30, characterised in that said different particles are impregnated with a substance which transfers to the workpiece upon impact.

32. A workpiece, characterised in that it has been blast-processed by apparatus or method as claimed in any one of claims 1 to 31.

Amendments to the claims have been filed as follows 1. Blast-processing apparatus, characterised in that it comprises turbine blower means to provide blown air as a vehicle for a blast-processing medium.
2. Blast-processing apparatus, characterised in that it comprises a hand tool adapted to use, as a vehicle for a blast-processing medium, blown air provided by turbine blower means.
3. Apparatus as claimed in claim 1 or 2, characterised in that it comprises a plurality of turbine blowers arranged to act side by side.
4. Apparatus as claimed in any one of claims 1 to 3, characterised in that it comprises a reduced turbulence path for air blown from turbine blower means as said air vehicle.
5. Apparatus as claimed in claim 4, characterised in that said path is arranged to feed said air vehicle substantially in a straight line from said turbine means through to a supply hose adapted to use said air vehicle.
6. Apparatus as claimed in any one of claims 1 to 5, characterised in that it comprises a hand tool adapted to use said air vehicle provided by said turbine blower means, the hand tool having a Venturi or like device to entrain blast-processing medium, said device having a substantially increased cross-sectional area.
7. Apparatus as claimed in claim 6, characterised in that said cross-sectional area is at least four times as large as a standard or conventional such area for such a tool.
8. Apparatus as claimed in claim 6, characterised in that said cross-sectional area is at least 16 times as large as a standard or conventional such area for such a tool.
9. Apparatus as claimed in any one of claims 6 to 8, characterised in that a said cross-sectional area is at the mouth of an injection nozzle into said device.
10. Apparatus as claimed in any one of claims 6 to 9, characterised in that a said cross-sectional area is at an exit orifice of a nozzle of said device.
11. Apparatus as claimed in any one of claims 1 to 10, characterised in that it comprises a hand tool to apply said blast-processing medium to a workpiece, with a brush surrounding the exit mouth of the hand tool to maintain substantially sealing contact with the workpiece in order to contain the medium, the brush being mounted to the workpiece on an elastic collar.
12. Apparatus as claimed in any one of claims 1 to 11, characterised in that it is adapted for closed-circuit operation and for the blast-processing medium to be returned under pressure due to said air vehicle.
13. Apparatus as claimed in claim 12, characterised in that the returned medium is returned under said pressure into a cyclone separator.
14. Apparatus as claimed in any one of claims 1 to 13, characterised in that it comprises variable air inlet means to the turbine means.
15. Apparatus as claimed in claim 14, when appendant to claim 13, characterised in that it is arranged for variation of the air inlet to the turbine means to control the action of the cyclone separator.
16. Apparatus as claimed in any one of claims 1 to 15, characterised in that it is adapted for close-circuit operation and comprises filter means between a returned blast-processing medium region and the turbine means.
17. Apparatus as claimed in any one of claims 1 to 16, characterised in that it comprises a reservoir for the blast-processing medium at a bottom exit of which reservoir is provided a baffle to help prevent the medium from blocking the exit, said

baffle being provided with an air conduit by-passing the medium to help prevent the medium from blocking the exit.
18. Apparatus as claimed in any one of claims 1 to 17, characterised in that it comprises a housing that can be moved around by hand comprising a reservoir for blast-processing medium, a returned blast-processing medium region provided with a cyclone separator arranged to feed the separated medium to the reservoir, said turbine means, and filter means between the separator and the turbine means.
19. Apparatus as claimed in claim 18, characterised in that said turbine means are mounted in a dome removably mounted to the remainder of said housing.
20. Apparatus as claimed in claim 19, characterised in that said dome is rotatable on said remainder of the housing to control air inlet to the turbine means.
21. Apparatus as claimed in any one of claims 1 to 20, characterised in that it comprises a hand tool adapted to apply a blast-processing medium, the tool having a member rotatable to vary the amount of the medium able to be entrained in the tool.
22. Apparatus as claimed in any one of claims 1 to 21, characterised in that it comprises a portable unit comprising a blast-processing medium reservoir.
23. Apparatus as claimed in claim 22, characterised in that the portable unit comprises a separator for an air/blasting-medium mix and is adapted for use in the closed-circuit method of blast-processing.
24. Blast-processing apparatus substantially according to any embodiment hereinbefore described.
25. Blast-processing apparatus substantially according to any embodiment hereinbefore described with reference to the accompanying drawings.
26. Blast-processing method, characterised in that comprises use of turbine blower means to provide blown air as a vehicle for a blast-processing medium.
27. Blast-processing method substantially according to any embodiment hereinbefore described.
28. Blast-processing method substantially according to any embodiment hereinbefore described with reference to the accompanying drawings.
29. Blast-processing method, characterised in that comprises use of a blast-processing medium comprising pellets of non-woven fabric.
30. Method as claimed in claim 29, characterised in that some particles of the processing medium are different from others.
31. Method as claimed in claim 30, characterised in that said different particles are impregnated with a substance which transfers to the workpiece upon impact.
32. A method of blast-processing, characterised in that blown air entrains a blast-processing medium which it sucks from a reservoir in which there is used a method to prevent the medium from producing blockages at an outlet for the medium from the reservoir and/or at a conduit for the medium from said outlet.
33. A method as claimed in claim 31, characterised in that the suction is provided by Venturi means with an operative aperture having a cross-sectional area of increased size.
34. A method as claimed in any one of claims 32 to 33, characterised in that the medium reservoir and means to entrain the medium are carried by the operator during the processing.
35. A method of blast-processing substantially according to any example hereinbefore described.
36. Blast-processing apparatus, characterised in that it comprises turbine blower means to provide blown air as a vehicle for a blast-processing medium, conduit means, means to enable the blown air to suck said medium through the conduit means from a reservoir, and means to prevent the medium from producing blockages at an outlet from the reservoir and/or at the conduit means.
37. Apparatus as claimed in claim 36, characterised in that said prevention means comprise baffle means.
38. Apparatus as claimed in any one of claims 36 or 37, characterised in that said enabling means comprise Venturi means with an operative aperture having a cross-sectional area of increased size.
39. Apparatus as claimed in any one of claims 36 to 38, characterised in that the blower means comprise a plurality of turbine blowers arranged to act side by side.
40. Apparatus as claimed in any one of claims 36 to 39, characterised in that it comprises a reduced turbulence path for air blown from the blower means as said vehicle.
41. Apparatus as claimed in any one of claims 36 to 40, characterised in that it comprises a hand tool with an exit mouth through which to apply said medium to a workpiece, a brush surrounding the exit mouth to maintain substantially sealing contact with the workpiece in order to contain the medium, and a return conduit for the used medium with an inlet mouth adjacent said exit mouth.
42. Apparatus as claimed in claim 41, characterised in that said return conduit inlet mouth surrounds said exit mouth.
43. Apparatus as claimed in claim 41 or 42, characterised in that the hand tool comprises a member rotatable to vary the amount of the medium able to be entrained by the blown air.
44. Apparatus as claimed in any one of claims 36 to 43, characterised in that it comprises variable air inlet means to the turbine blower means.
45. Apparatus as claimed in any one of claims 36 to 44, characterised in that a portable unit comprises at least said reservoir.
46. A workpiece, characterised in that it has been blast-processed by apparatus or method as claimed in any one of claims 1 to 45.