AU606416B2 - Abrasive blasting apparatus - Google Patents

Description

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C1~I.

aas;w AU-AI-15448/88 WORLD 'NTELLECTUAL PROPERTY ORGANIZATION International Bureau

PCT

0 INTERNATIONAL APPLICATION PUBLJ (51) International Patent Classification 4 B24C 7/00, B05B 7/32, 7/14 E04F 21/12 0OPERATION TREATY (PCT) n Number: WO 88/ 07915 (43) International Publication Date: 20 October 1988 (20.10.88) (21) International Application Number: PCT/GB88/00264 (22) International Filing Date: (31) Priority Application Number: (32) Priority Date: (33) Priority Country: 6 April 1988 (06.04.88) 8708499 9 April 1987 (09,04,87) (81) Designated States: AT (European patent), AU, BE (European patent), BR, CH (European patent), DE (European patent), DK, FR (Furopean patent), GB (European patent), IT (European patent), JP, KR, LU (European patent), NL (European patent), NO, SE (European patent), SU, US.

Published With (71) Applicant (for all designated States except US): GA- GEMARCH LIMITED [GB/GB]; I Park Gate, Knaresborough, North Yorkshire HG5 9DR (GB), (72) Inventors; and Inventors/Applicants (for US only) NICHOLSON, Bruce [GB/GB]; I Park Gate, Knaresborough, North Yorkshire HG5 9DR DAVIS, Ronald [GB/GB]; Highfield Road, Bradford, West Yorkshire BD2 2AU (GB), (74) Agent: BRAY, Lilian, Janet; Eric Potter Clarkson, 17 Crown Street, Hebden Bridge, West Yorkshire HX7 8EH (GB) inte i .aLw Lefl ort.

This document contains the amndments made under Section 49 and is correc' for printing OA.jp-. 8 DEC 1988-

AUSTRALIAN

4 NOV 988 PATENT

OFFICE

(54) Title: ABRASIVE BLASTING APPARATUS (57) Abstract A method and apparatus for mixing separately-contained media such as would be used in a wet abrasive blasting operation comprises a receptacle (10) for a liquid/abrasive medium, a receptacle (11) for a liquid, and a delivery line (20) along which pressurised fluid Is adapted to be fed, The receptacles (10, 11) communicate via pipes (22, 23) with the delivery line (20) so that the liquid and the liquid/abrasive medium are entrained by the pressurised fluid. The receptailes communicate with each other via a hole (14) to balance the fluid pressure system between them and a means (15, 19) is also provided to deliver pressurised futd into at least one of the receptacles (10, 11) in order substantially to balance the fluid pressure system between the receptacles 11) and the delivery line (20) and to facilitate outflow of the liquid/abrasive medium and the liquid into the entraining fluid, The method comprises entraining the separately-contained media such as liquid/abrasive medium and the liquid medium in a flow of pressurised fluid whilst simultaneously applying the pressurised fluid to the media In their receptacles (10, 11) in order to balance the fluid pressure system between the receptacles themselves and the receptacles and the delivery line and to assist their egress into the entraining flow, L_ ^WO 88/07915 PCT/GB88/00264 ABRASIVE BLASTING APPARATUS This invention relates to abrasive blasting apparatus especially but not exclusively a wet abrasive blasting apparatus.

In wet abrasive blasting apparatus the abrasive medium is entrained in a pressurised liquid flow or gaseous-entrained liquid flow (hereinafter for convenience simply referred to as "pressurised fluid flow") and is directed against, the surface or other article to be treated by a controllable nozzle. It is common practice with such an app ratus to add a dry abrasive medium into a gaseous stream and then to add liquid to wet the abrasive medium prior to its egress from the nozzle outlet so that dust generation at the work area is reduced, This liquid is normally delivered into the abrasive and pressurised fluid flow by a separate pump the inclusion of which makes the cost. of the blasting apparatus more expensive than is de irable, renders thO blasting apparatus mlore pron toL brea 4 own, and requires a greater technical knowledge of the operator. A further disadvantage is thai variations in the entraining fluid pressure require either manual adjustments of the pressure outflow from the pump, or the provision of a pressure balancing control means between the entraining fluid supply and the pump.

As a result, control of the apparatus with particular reference to the abrasive medium/liquid outflow is difficult, in the first instance, with consequent variation in the efficienr'y of the apparatus, and, in the second instano, the cost of the apparatus is further increased by the need to provide the pressure balan ing control tmeans which, in any case, does not provide instantanteous adjustment of the pump upon va&riato Lon in entrairing fluid pressure occurring, aaaii with advers C effects on the efficiency of the apparatus.

2 It is an object of the present invention to provide an apparatus for wet abrasive blasting which obviates or mitigates the aforesaid disadvantages of cost, varying control and efficiency.

The apparatus according to this invention may be used dry, or the apparatus may, more generally, be employed for purposes other than abrasive blasting.

More detailed references to these alternative uses will be made later, Generally, therefore, apparatus according to the present invention comprises a first receptacle adapted to contain particulate material or a particulate S. 15 material and a liquid combination, a second receptacle to contain material to be mixed with the contents of tne first receptacle, and a delivery line along which an entraining pressurised fluid can be fed from a source and with which the receptacles are adapted to 20 communicate, and is characterised in that a means is provided to direct pressurised fluid from the source into one of the receptacles behind its contents in terms of its contents outflow from the receptacle, and in that a communication exists between the receptacles substantially to balance the fluid pressure system between the receptacles themselves and the receptacles S" and the delivery line to facilitate the simultaneous outflowing and dispersal of the contents of both of the receptacles into the entraining fluid flowlig along the delivery line.

Preferably, the first and second recertacles are located one within the other.

Preferably also, the inlet in the first A7 receptacle for the Introduction of the particulate

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<>11 O Uj r LDU] t A, f;j 3 material or the particulate material and liquid combination is provided with a valve which ,s closed by the application thereto of pressurised fluid from within the receptacle.

Preferably also, a means to enable a circumferentially directed jet of liquid is provided to swirl the particulate material to assist its entry into the first receptacle.

Preferably also, the first and second receptacles are separated by a porous wall.

sees Also according to the present invention there is 15 provided a method of mixing a plurality of separately Scontained media, at least one of which is a par iculate material or a particulate material and a liquid combination, by entraining the media from their containers into a flow of pressurised fluid and 20 characterised in that the pressurised fluid is s\ simultaneously applied behind at least one of the media in terms of .its outflow from its container, and in that a communication is provided between the containers substantially to balance the fluid pressure 25 system between the conta iners themselves and the Scontainers and the flow of pressurised fluid to facilitate the simultaneous outflowing and dispersal of the media from their containers into the entraining fluid.

The present invention can, therefore, provide a pumpless wet abrasive blasting apparatus and as the entraining pressurised fluid is also applied In this instance directly to an abrasive and a liquid combination and a separate liquid there A t

V^VT

org WO 88/07915 PCT/GB88/00264 -1 is instantaneous and equal adjustment to the en raining pressurised fluid and direct pressurised fluid upon any pressur:' variations occurring at the pressurised fluid source.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawing, in which:- Figure 1 is a part sectional elevation of an apparatus for wet abrasive blasting according to the present invention; and Figure 2 is a corresponding plan view.

The apparatus comprises two co-axial concentric receptacles or chambers 10 and 11. The inner chamber serves to contain the abrasive medium which is for example sand, which sand may be wet sand. With the present invention it is not necessary as is customary with wet abrasive blasting apparatus using sand as the abrasive medium to employ dry sand which is often delivered to the apparatus bagged. As a consequence the present invention provides, a wet abrasive blasting apparatus in which it is possible to re-use wet sand. The inner chamber 10 in use also, of course, contains water and it is to be noted that the water is always introduced first into the inner chamber 10 followed by the sand (or other solid abrasive medium) to ensure that there is effective mixing of the sand and water and no clogging at the outlet 12 of the inner chamber. The introduction of the sand into thE water in the inner chamber 10 causes the sand to sink through the water thus getting wet immediately. The. introduction of pressurised air into th(inner chamber 10, as hereafter described, causes a swirling action in th inner chamber 10 to complete the mixing. The outlet 1]2 iL disposed at' the bottom of th.

chamber 10 and the inlet 13 of' the inner chamber 10 is provided a t th top of sai WO 88/07915 PCT/GB88/00264 The outer chamber 11, in use, cIontains additilonal water for addition to) the sanid/water mixture egressing front the inner chamber 10 at- will be described later.

There 1 s, at LIeast, one hol) Ie 14 providing a1 communication between the outer chamber 11 and the inner chamber 10, which hole 14 is, disposed at the upper end of' both chambers 10, 11, The inlet 13 to the inner chamber 10 is controlled by an air luch valve, for example a mushroom-t-ype valve, 15, which valve 15 is closed on app~lication, thereto of pressurised aIr., The apparatus has as its operational or mlotivE fluid pressurised air which passes from a pressurised air' source, such ror, example, as ti pressurised air maints(ro shown) to a delivery pipe system gaenerally indicated at 16.

Air tinder prossure is delivere-d from a source triot showrn), possibly an a-ir compressor Lo the pipe system 16 atthe main inlet 17 ontrolledI by a valve 1,8, 2Q Pr~ussurlsed1 air is delivered to tho valv(, 1-5 hv pipe 19, whieh air thent flows from the inner chamber 1,o into the outer chamber It vija the hoP-, 14, Pressur isedi air is also delivered by a pipe 2 0, Valve controlled as indicated at 21' to an abrasiv(e, blasting hose and nozzle (not s howtn) coupled to the pipo by a b AyoneL joint connection as indicated at 38, Thenozzle of the abvasivE: blasting~ hose is provided with deadman's handlP- sc that- the abrasive blasting operatiori is rontrolled by, the operator (release of the handleo lo s in o the n Ile and di qvo ntLinu ii ng the abras i vb la tinrig o pe rat io) PreferciblY the blasting nozzle of the lance tvpt a nd n o a conventional Venturi no-"zle- as it has bo(-r.

fo(urtd. that. abrasive Lends to lodge in txnd c-log a ventuor~ nozzle during uts- of' the apparatus, Th.- lance provides ar, ftt llnt ror the pressurised fluid which, has- a sinaller I _I WO 88/07915 PCT/GB88/00264 bore than that of the delivery pipe 20 effectively to concentrate the pressurised fluid flow therethrough ,o that it can be appropriately directed by the operator. It has been found that the lance operates effectively when the ratio of the diameters of the pipe 20 and of the lance is in the range 1.5 1 to 10 1 inclusive with a lance that is at least 100 mm in length. Typically, the diameter of the bore of the lance is of the order of mm for a 45 mm diameter pipe 20 for delivery of pressurised air at. 10 cubic metres per minute at 100 psi.

The length of the lance is usually of the order of 450 mm to enable the operator to distance himself from the blasting and grip the lance effectively.

The chambers 10 and 11 communicate with the pipe via pipes 22 and 23 respectively each of which is respectively controlled by a valve 24, Thus the pipes 22, 23 provide communication between the bottom of the chamber 10 and 11 with the pipe Adjacent the top of t h outer chamber 11 there is provided a fast- exhaust pipt-, 2 control led by a valve 27 Water is supplied to the inner and outer chambers from for example] a mairns water supply (not shown) by a pipe 28. incorporating a non-return valve 29 and an open/close valve 30. The water is delivered directly into the chamber 11 by the pipe 2R to which is connected a pipe 31 for delivering water into the inner chamber this pipe being valve controlled as indicated at 32, A water level cont ro or overflow pipe 3:.

corrnuncates with the inner chamber 10, this pipe 33 also.

being valve controlled as indicated at 34, The \arious valves are indicated as being manually controlled but it is c early t be understood that thpes valves cari be suhjec t to aut omat i- control in an' convenient manner.

-1 WO 88/07915 PCT/GB88/00264 To render the apparatus ready for use thE valves 18.

21, 24, 25, 27, 30, 32 and 34 are all closed. Valves and 32 are then opened to allow water to flow into the inner and outer chambers 10, 11. A given quantj ty of abrasive medium for example sand (wet or dry) is then fed through the inlet 13 which is open owing to no air pressure being supplied to the valve 15 to close same.

Water continues to be fed into the chambers 10 and 11, and, when the required total volume of sand and water is delivered into the inner chamber 10, water will.flow out of the pipe 33. At this stage, the valve 32 is closed followed by the valve 34. When sufficient water has been fed into the chamber 11, the valve 30 is also closed.

The valve 17 is then opened causing the valve 15 to be moved to the closed position and pressurised air to be introduced into the inner chamber and, through the communication hole 14, into the outer chamber 11.

Valve 21 is now opened allowing pressurised air to flow along the pipe towards the hose and nozzle (not shown) Valv'.es 24 and 25 are then opened to the desired degree to allow the water/sand mixture from the chamber and additional water from the chamber 11 to be movei into, and be entrained by, the airstream for delivery along the hose out of the nozzle whence it is directed against the surface or other article to be abrasive blasted.

The sand/water mixture and the additional water arr subjected to the same air pressure in the upper parr of the chambers 10 and 11 as that which is used to entrain thenm oit. of their respectiv chambers., Thus, any variation in the, air pressure at sourc(- i, automatically and instantaneously applied to both th, entraining air and the internal air (cuntained within thchambers 10 and It.

WO 88/07915 PCT/GB88/00264 8 At any stage, the valve 24 can be closed, and water only from the chamber 11 be fed into the airstream, for the purposes of washing down the work area.

Alternatively, the valves 24 and 25 can be closed lee-ing air travelling through the hose and nozzle, for blowing or drying purposes.

During operation, the air feed pressure can be varied up or down in order to achieve different rates of working or different types or levels of finish on the work area. A pressure gauge may, in these circumstances, be included in the air inlet line 17 in order that the operator can more accurately judge the working pressure.

The normal sequence of operations for shutting off the apparatus is first of all to close the valve 24 to prevent any further emission of abrasive, When all of the abrasive in the hose has cleared, the valve 25 may be closed to prevent any further water going down the line.

After all the water has cleared from the hose, the valves 21 and 18 are closed. The valve 27 may then be opened to allow fast. reduction of the air pressure in vessels i0 and 11, which in turn allows air lock valve 15 to open.

If, for any reason during normal operation, ai emergency stop is required, this can be activated manually, or triggered automatically (by release of the deadman's handle, for example), by opening the valve 27, preferably with a simultaneous closure of the valve 18.

Means is provided to effect fast filling of the chamber 10 with substances which do not flow quickly on their own wet sand or slurry). Such means consists of a water jet 35 situated inside and in close proximity to the wall of the filling hopper 36 at the top of the apparatus. The jet 35 is circumferentially-directed that is swirls water round the hopper area, when required, and enables th entr of the material through the open inlet 13 and into th- chamber 10. A valve 37 controls the flot O water to the Jet WO -0/07915 PCT/G B88/00264 It is to be noted that additives can be included in either the water, in the chamber 10, or alternatively, in I-h wae in the chamber 11, such an additive being, for example, a rust inhibitor, if the surface or article heinto: treated is formed of metal, or, an anti-freeze material for low temperature working. Alternatively, the addi tive may be introduced in powder or, granular form, mixed with the abrasive. Because the total volume of material in both chambers i.s 1knovn at commencement of the operational sequence, pve-measured doses of additive can be included In either chamber' to give an accurate dilution of the add itive.

The wet~ abrasive blasting apparatus described above canm be used dry and in this case the dry abrasive or other abrasive medium is simply,, oontained within the chamber 10, the water SUpply system being closed off an(' the sand or, other' abrasi\'e medium beingj entrained along1 pipe 20 through the pipe 22 via the open valve 24 the sandr- hel ug subjected to tho internal air pressure equal t he entra ninga n ir pressure as decvribed above, The apparatuis can also be, used for ice blasting and ir. this, case- th inner, chamber, will contain ice. particles and water and the oiter chamber 11 will contain water. It ic, to be noted that the ice particles formed from ;.atei t,1l1 be prevented from coagulating (freezing together) by introducing suitable additives into the water prior tu frospezing, Sut, dditives would be for example poty- The above described apparatus can, as aforesaidl, beused either wet r dry as described and it can b- us(e Fo r washiticg down us ingr Aator ortly frrom Qhamlber' 10 C) ot.

fromi chambers4 10C and i1, The apparatuks provides faster- cleaning than kncowr we', abrasi\ e blast ing apparatus (all other opet'atiuniLO fNt(-(ors being e qua.L it Ican Uri h- 20110 t r P'~'e ir4' 'rt ai c'i rooms tanues,; Th~- reason th- hi WO 88/0791:5 PCT/G B88/00264 that each particle of' abrasive, having being soaked under pressure, is enclosed in a fi lmc of water so that its ef factive w'oight is Increased Lis it leaves the blast nozzle. Thus its momentum is treater and ic does more 53 work when it strikes the workpiece surface, The apparatus is not subject to "choking" as are known apparatus which, 0n occasion, become blocked at the abrasive outlet of the pressure vessel, In practice, with the known apparatus, these blorkages are usually relieved by turning off the main air supply N.g, closing valve 21 momentarilj VTh apparatus is relativel O neap to manufacture compared pith known apparatus, There is less wastage of abras ive on site since withl the apparatus according t) t he present invention 4l1 spent abrasive can be re-used in t h- wet condition, i e it is not. necessary to dry snmok The aipparatus can be readily used in high hiumidity areas since contamiation by~ mIui st Or" will not adversely ti reeAl 1,.

The apparatus Is spark fre" and static free, It is pumpless as will be c'lea r frtom I h- aboive ana duo to the K oh oKI pump there is o by iun y no need to pro v ide a purnj driving generator, The apparatus has no mechanical wotrkin; parts and due tU the simple nature of the apparatus all parts can easily1 be changed and renewedi in a short time.

The apparatus is KakC t" u"ho W as reon It can W.

used urnski lied labour.

The appa rat us when OSPA to n ""fblast in n pvowesst procluoe,- C'ar loss- al r-bovn rue tnhant ornixrabl, knowt.

appi at un-'f and t herefto r- NOi tows Calti-out at any g tVlt d Is t ;i nc f ro n th- Wotl. xi-i. Tat make, 1 environmentuat. more aeoeptahl.'~ Iwo088/07915 PCT/G B88/00264 Finally, the appar'atu,; can be used with a wide- range of' easily obttainable abrasives wet and dry and in use it iM considered that there will b e a lower u Sag of' ab'as ivt' l.hai with other w et cabrasive blasting s-yst oms (in the region of 20%O iess) and the apparatus involves less uleai'iiig tip ant sie to han convenitioniil wot abrasive blas:ting apparatus, Thp apparatus according,. to the present invent ion is St; t V 0- n ver VSat il a-.nd be (USed, t nt ei' al iad as Vol lows:, Wt a dry abras 1vo cIeni jnng of s tone br'ili, t err'at~lt a, steeci I ironi and allI othcer hard or seo hard %urfaces, 2 Stripping- of pa ints and other cotinz i'oru the.s(e sir'aoes eithver in oneo operationi or, Layer tiy laeor, 3 WashLng, of r of' these su r Naues I Removal of' cant ami nant., from sur fwoes, v l ri i o, ,-ic L ive c on t. a ii, i n t io n o I bi ogo, i C f L~mi rvit t i of t pozsibI uwing chomioal additLive, in tnhe wattrt mpr'o e te It Ef Vc! I. ency o)f' th,( L roa Linen I t I re nva I o ullIs and greases fromn suri'aoes- possiblk itsing hot Remnoval otf gzra f'i Li f'rom 811one and 0 Lliet' stirftacve-i.

f; T te-u v ing or' surfaves et t.her- for as ei apparaL ~Or its a preparation for over ooating or hanidinig of' thfv' Surface" te (-xposing or grainl on timber su rfaces ths, V rons L riag (it, qjlwg Lass to mke opalue tin' rougheining or iitat ting (if platst k' arnd a.14 t' sr'ocit v Figara i'v- n r o'9 La ss, stn p is an tht !iurfavo tuiing ,4uitc alI r 1[sk 1~r p'ett I, QV'tn~o maktelr 1ai, il Lttort of miI-s tan 1, rin' appli icit i tl of' matri t*i he mi.'ing of sAu b qt a (I I ii Wit II- lV It'-4 V M A 1 i :4 (11W I l t JP)W.A '1 grao a: r ~1'itou"t'rf r-t ,4"mJ il mat er't it WO 88/07915 WO 8807915PCT/G B88/00264 12 or liquids) with themselves or with each ocher, and k the spray or 'blast' application of the resultant mixes, For example, the mixing and application of' renders, slurries, coatings, paints, adhesives, dpicin,- mixes, mixing salt with sand or gravel and spraying onton roads liable to freezing, or deicing mixey onto aircraf't) the mixing of plant seeds into culture media and the spray application of Such; the mixing and Spraying of' fertilisers and weedkillters onto agrkLu .tura l land; the mixing of or coating of textile fibres with bonding agents and thei r 4 pray app licak ion in, for example, bonded fabric produro~n; the impregnat ion of surfaces with another- subs tance; the variegatr'd coouring o f surfaces :nuch as floor,,, wall1s, tiles, by- using diff'erent ooloured materials in the different 0 chambers or of different densities on one chamnber, Mlodfloations may he made to the' above described e~nMplV a porous Wwt 1 may be provided be twseen the Chambers W0 It in Order to allow for the MoVeMont oci, say, u .1iquld, from chamber it into chamber 1, Vo F wNamnple when ice blasting, rce and water would he pul into chamber 10 and water into chamber 11. If tho water in chambe r 10 is, reduced too much dWr ng the b last ing operation, then water uan perolate f'rom ohainber it1 tai chamber 10 and so prevent clogging of the too in chamber, In another e-,mbodiment of the inventiocn, axn outer Phamber is used for th" abruni vo/liquid medium tont an i nl r ohamber Col. t he iquid, medium. Her theI o v'haMber oati bo of a iaI volume w ith respect t oW on lter chamber. and t porous wall can, be used to id" t ho chambers so that the liquid Vlowg Vron the outor ohamnb"r into the inner chamour L~o c'harge, it with liquid pri itr and during tho bias txng to obviate t he need for soparm.' .WO88/07915 PCT/G B88/0026,4 1Q pipeworhl and other filling means. Some of the abrasi Ve may also pass into the inner chamber through the wall but this does noL inhibit. 'the mixing arid blasting process.

Hrowever, this As pritferably prevented by making the pore size ini the wall such that passage of -the abrasive there through i s prevented. Effectively, i n t hi embodiment, -the- inner chamber is reduced to a porous pipe located in the outer chamber and commun,,cating, therewith above the level of the media- contained therein, through which pipe iquid can be drawn off from the liquid! abrasive med ium and entrained separately in the prassurised fluid from. the abrasive/liquid medium.

TheW apparatus in!,y comprise more than two chambers provided all the chambers are in communication so that there is -In the chambers air pressure equal to the entraining fluid pressure, The, cha~iibers may be located one within the other ond bo coaxial and concentric as In the above dosczribed appartitus or t h ey, a -y b e d is po(sd i-ntt s ide -bN-s1d relationship oitho r, parallel o ne WitLh another or in Juxtaposed ooaxitAl relati onship, The chambers mtay in fart br- soparate oino f rm anojtr, u nd there ma be t wu) or more ehamriier, prov idoo there i s communication between them to ensure Common 2$ fluid pressure within all the chambers, which pressure is equal to and variable with the entraining fluid pressuro.

Claims (9)

1. An apparatus comprising a first receptacle adapted to contain particulate material or a particulate material and a liquid combination, a second receptacle to contain material to be mixed with the contents of the first receptacle, and a delivery line along which an entraining pressurised fluid can be fed from a source and with which the receptacles are adapted to communicate, and characterised in that a means is provided to direct pressurised fluid from the source into one of the receptacles behind its contents in terms o, of its contents outflow from the receptacle, and in that a communication exists between the receptacles S. 15 substantially to balance the fluid pressure system between the receptacles themselves and the receptacles and the delivery line to facilitate the simultaneous outflowing and dispersal of the contents of both of the receptacles into the entraining fluid flowing along the 20 delivery line.

2, An apparatus as claimed in Claim 1i characterised in that the first and second receptacles are located one within the other.

3. An apparatus as claimed in Claim 1 or 2, characterised in that the inlet in the first receptacle for the introduction of the particulate material or the particulate material and liquid combination is provided with a valve which is closed by the application thereto of pressurised fluid from within the receptacle.

4, .n apparatus as claimed in any one of Claims 1 to 3, characterised in that a means to enable a circumferentially directed jet of liquid is provided to U on WON K swirl the particulate material to assist its entry into the first receptacle.

An apparatus as claimed in any one of Claims 1 to 4, characterised in that the delivery line terminates in a lance which comprises a substantially straight-bore rigid tube of at least 100mm in length and in that the ratio of the diameters of the delivery line and of the lance is between 1,5:1.0 and 10:1 inclusive.

6. An apparatus as claimed in Claim 2 or in any one of Claims 3 to 5 when dependant on Claim 2, characterised in that the first and second receptacles are separated by a porous wall.

7. An apparatus as claimed in Claim 6, chiaracterised in that the outer receptacle comprises the first receptacle which is adapted to contain a particulate material and a liquid combination and the inner receptacle comprises G 20 the second receptacle which is adapted to contain a liquid and which can be filled by passage of the liquid through the porous wall from the first receptacle.

8. A method of mixing a plurality of separately contained media, at least one of which is a particulate material or a particulate material and a liquid combination, by entraning the media from their containers into a flow of pressurised fluid and characterised in that the pressurised fluid is simultaneously applied behind at least one of the media in terms of its outflow from its container, and in that a communication is provided between the containers substantially to balance the fluid pressure system between the containers themselves and the containers and the flow of pressurised fluid to facilitate the simultaneous outflowing and dispersal of the media from 16 their containers into the entraining fluid.

9. A method as claimed in Claim 8, in which one of the media is a liquid and characterised in that the temperature of the liquid is above the ambient temperature. A method as claimed in Claim 8, characterised in that the particulate material is ice. Do*: Dated this 30th day of October 1990. GAGEMARCH LIMITED *'By their Patent Attorney GRIFFITH H-ACK CO @gas** a 6 so 4 a