US2328581A - Abrasive projecting apparatus - Google Patents

Description

Sept. 7, 1943. N. J. Q'UINN 2,328,581

ABRASIVE PROJECTING APPARATUS ATTRNE'YS.

Sept. 7, 1943. N- J, QUINN 2,328,581

ABAsIvE PRoJEcTING APARATUs INVENT OR.

i /VELsoNlQu/NN BY'! ATTORNEYS.

Sept. 7, 1943. N. J. QUI-NN ABRSIVE PROJECTING APPARATUS Filed Nov. 8., 1940 4 Sheets-Sheet 3 INVENTOR. NELso/v \.7.` Qu/NN ATTORNEYS; 1

Sept. 7, 1943., N. J. QulNN ABRASIVE PROJECTING APPARATUS 4 Sheets-Sheet `4 Filed Nov. 8, 1940y INVENTOR. NELSON JIQu/N/v BY @/Mmy l AVroRNEx/s..v4

Patented Sept. 7, 1943 U N I T E D STATES P-ATEN T OFFICE ABnasIvr-LPROJECTING APPARATUS Nelson it. Quinn, Toledo, 'ohio y Application November 8, 1940, Serial No. '364,931

(ci. s1- 8) 25 Claims.

This application is a continuation in Apart of my co-pending application Serial No. 166,082, for Abrasive projecting apparatus, led September 28, 1937.

The present invention, relating -as indicated, to a method of and apparatus -for projecting abrasives, is more particularly directed -to Ia method of and apparatus for projecting successive charges of abrasiveiat a high speed by means of uid pressure released in small increments or charges to reduce the consumption of the same and produce explosive-like pro-pulsion of the abrasive charges against the Work. A further'vobject of the invention is the provision of a method and apparatus that will reduce the costof abrasive cleaning and increase the eiiiciency. Another object is the provision of a simple Vand inexpensive mechanism forcarrying out the method referred to above and one that will have a minimum ci' working parts and greatly reduce -the destructive and rapid wear of the abrasive -on the propelling mechanism.

The cleaning of castings `is, today carried outlay 4three methods, (l) tumbling, (2) propelling abrasive against them by feeding the same into an air `blast and (3) directing abrasive against them by a centrifugal wheel. 'Tumbling is ,slow and `applicable only to certain types lof castings. .An air blast is extremely wasteful `ef air and -a vrelatively small amount of abrasive can be carried by the air stream. Centrifugal Wheels are a development, commercially at least, of the last few years and. while very effective are expensive to maintain because of the high Wear o-n the blades and means for feeding abrasive to the blades. In addition the propulsion speed of abrasive thrown by a wheel must be kept much lower than from an air blast to prevent excessive wear on the blades and to `avoid still other difficulties in operation. The present invention provides a method and apparatus the cleaning operation of which is more efiicient than any of those now in use.

As will be hereinafter `more particularly explained, my projecting apparatus has been designed to be operable entirely by means o-f a single supply of compressed air, which acts also a's the propelling agency for the slugs of abrasive. Other features and objects of my invention will appear from the detailed description following as construed in the `light of the drawings appended hereto. The novel features of the invention will be summarized in the claims.

Referring now to the drawings: y

Fig. l is a longitudinal cross-section of one form of my abrasive projecting gun;

`a convenient distance away from the device.

fFig. 7;

A9 is .a sideeievat'ion of one of demente, of the device seen 'in Fig. v5;

Fig. -1'0 .is a side View Aof f another element ofthe .device seen in Fig. 5,; l

Fig. 1l is a side elevation partially in section of another alternative form of my abrasive projecting gun; and

Fig. 12 is a 'fragmentary cross-sectional View taken substantially on the Vline TI-l2 'of Fig. '11.

In general, my `invention may be said to 'comprise three parts; one, a suitable form of the air metering valve T5 two, 'the 'feed valve "for 'abrasive I6; `and three, the barrel mechanism I1. These parts are bolted together to form a continuous unit and supplied with compressed air whichnot only furnishes the propelling 'forcefo'r the vabrasive vbut controls the operation of the device.

Air is -admitted to 'the metering chamber through a compressed air nipple |`8 and thence metered by the reciprocating piston I9, after which it passes through the chamber '2'0 .into contact with the abrasive. l

In operation the metering .piston I9 lies horizontally, but vfor convenience is described as 'it appears in Fig.. l... It circular in cross-section and is provided withthree annular recesses `2 I, 22 and I23 (Figs. l and 4). The recess 22,'whenpos'itioned in line with 'the nipple It andthe .passage 420 permits passage of the 'air `column to the abra sive feed chamber. The feeding `of air is Vcut off when the annular opening 22 occupies the posiftionshown in Fig. l, at which time it is out off Vline with the aforesaid openings. Piston lil i's reciprocably carried in a chamber of the casing of the valve 15 and normally retained in the posi- 'tion in Fig. l by suitable spring mechanism hereafter to be described.

Reciprocation of the piston I9 is controlled lby an auxiliary line `25 which meets the main lin'e fat In practice, I have Afound six feet to be ay good distance as this revents surging in the main feed line from being transferred to the auxiliary line and affecting the control of the piston i9. A needle valve 2l is inserted in the auxiliary line to control the amount of air passing therethrough. As the auxiliary air column leaves the needle air valve 2l, it enters a jacket integral with the chamber of the valve i5, as shown in Fig. 4. Openings lead from the jacket 23 to the interior of the piston chamber. Valvel rings 35 carried slidably in the openings 2l and 23 serve to open and close the intake ports til. Abutting pins 38 carried by the piston iS prevent the Valve rings 35 from forming a seal against the flanges acting to limit their movement.

When the piston is in the position shown in Fig. 1 the lowermost valve ring has been pushed down by the upper flange of the opening 2l to a position opening the adjacent intake ports 3B. Air rushes through the ports from the auxiliary line 25 filling the chamber formed adjacent the recess 2l and as a suitable pressure is built up, forces the piston i9 upwardly (as shown in this figure) to bring the annular opening 22 in line with the nipple IS and the passage 2G. At this time a charge of air under a pressure of approximately 6() to 100 pounds per square inch gauge rushes through the metering valve into the abrasive feed chamber to'propel the abrasive as hereafter described.

The action of the piston iS in opening the port 22 moves the lowermcst valve ring 35 (as appears in Fig. 1, upwardly) to close the intake ports all and open exhaust parts it discharging to the atmosphere. Simultaneously the upper valve ring has closed the upper exhaust ports Alt and opened the upper intake ports 30. Air then enters the upper intake ports from the auxiliary line 25 and in the manner already described forces the piston back down into the position shown in Fig. 1, closing the main air feed line to the abrasive feed chamber. As the piston l is forced downwardly to this position, the valve vrings 35 position themselves to again force the rpiston lll upwardly repeating the operation of feeding air intermittently to the abrasive chamber'.

Each time the piston it is forced upwardly in Fig. 1, mechanism is operated to feed a corresponding amount of abrasive into position to be thrown through the barrel il'. This mechanism is best shown in Figs. 1, 2 and 3. As there shown upward movement of the piston i9 forces the valve pin 45 upwardly against a stiff compression sprinCf 4l which, in turn, rocks the rocker arm 59 about its pivot 5l. This movement, in turn, forces the valve pin E5 downwardly against the action of a compression spring 5l to reciprocate the valve plug 6l) integral with the pin 25. As the plug 5l) is shifted, abrasive is fed to the ejecting breech A suitable supply of abrasive is normally fed to the funnel lll' through which is falls to ll the chamber 63. As the plug te is shifted by the piston i9, it assumes the dotted line position shown in Fig. 3 to close off the funnel 6l and at the same time pack the abrasive charge in the breech 65. It will be noted that a layer of abrasive stands between the radial face of the plug and the breech, preventing wear on the plug resulting from the air column throwing the abrasive from the barrel. Similarly, the position of the plug closing the feed funnel prevents the air fed from passing up through the funnel Si.

As the piston IS moves to the position shown in 1 Fig. 1, the spring 51 forces the plug SB outwardly and rocks the arm 50 to push the pin 45 against the piston I3.

If desired, I could employ this spring action to return the piston to its inactive position.; although from the standpoint of better timing, I prefer to make use of the double valve ring mechanism heretofore described.

To prevent the abrasive moving either way from the breech zone I may provide radially split diaphragme lll, preferably formed cf rubber or other suitable resilient material and positioned as shown. The pressure of the air ejecting the abrasive is sufficiently strong to easily displace the diaphragms during the ejecting operation. As the first of the column of the compressed air passes the passage Eil, through the adjacent diaphragm 10, il; encounters the abrasive just deposited into breech d5 and blows the same the mass of abrasive in line with the barrel through the second diaphragm 'l0 and out the barrel l 'l as a compact slug.

It is a very important characteristic of my invention to eject the charge of abrasive as a ccm- -pact slug and not intermingle relatively widely separated particles of abrasive in an air stream asis done in the ordinary type of air blast.

The barrel I7 as shown in Figs. l and 2 is surrounded by an outer shell 'l5 and is preferably made of very hard cast iron to resist as well as possible the abrasive effect of the charges shot therethrough. Even with the hardest material now known, the barrels wear very rapidly and must be continually replaced. The same is true of the breech portion 55 and in lesser degree of any other portion of the machine handling abrasive.

To eect ready interchange of parts due to this wear, the device is built in sections. As shown in Fig. l, the valve is provided with a ange 'I8 Which is bolted to a similar iiange 8D carried by the abrasive feed valve mechanism lli and which clamp between them the adjacent diaphragm lll. At the other end of the abrasive feed mechanism are similar flanges ST2 which are bolted to corresponding flanges iid securing the barrel to the rest of the device as shown. Similarly, the flanges S2 and S4 maintain the adjacent diaphragm I9 in place and position a member with a conical opening adjacent the barrel to permit room for displacement of the adjacent diaphragm.

The plunger or plug member Ell wears very rapidly due to intimate sliding contact with abrasive fed to the breech and is readily replaced by removal of the cover 8l'. A shield 9@ is mountled on the outer barrel member i5 adjacent the end to deflect abrasive bouncing back from the the pressure of the spring 4'. will, if increased,

tend to move the plug Eil to open the funnel 6l more rapidly and further will aid the air from the auxiliary line in returning the piston i9 to its initial position.

It will be seen from the foregoing description that I have provided a new means of projecting abrasive onto surfaces to be cleaned. By the term abrasive I means any material of granuassegni jlar nature whichit `is desired to'project onto an object. It will further vbe -apparent that my device projects such abrasive "in-'compact slugs as 'distinguished from mixtures'of air and scattered abrasive, with the result that very much less 'air is used for a given amountof abrasivethrown. 'Afurther 'result is that vthe abrasive vis projected 'with much more force yonto the surface desired because of its compact nature, and because the particles travel under the momentum giventhem jby the force of the ejection. `It will also be apparent thatmy device is operable entirely from Vthe Vsingle column of air used to provide the propelling force and that each mass or `slug of -abrasive is propelled ahead of an vair column and through comparatively still air. l The various 'parts of therdevice are automatic in operation. The yentire assembly is simple Ain construction and readily disassembled forcleaning and for "replacement due to wear.

The modification seen `more particularly yin lFigs. 5, 6, and 7 comprises, in general, -a recepta- "cle 95 for receiving abrasive, a reciprocating {irjing rtube 95 which projects -into the `receptacle and segregates a slug of abrasive withinlthe -receptacle, a valve indicated generally by the refverence character 91 forc'ontrolling admissionlo'f `fluid under pressure to the firing tube, a barrel 9B for directing the slug after the same is blown 'out of the firing tube, and a source of power 99 for reciprocating the firing tube and'actuating'the valve.

'I'he receptacle 95 is cylindrical and is pro- `vided with a vsuitable intake l|0| and an expan- 'sion chamber |02.

as 'the front end of the device, the receptacle is provided with a front flange v|04 anda re'arfilange 105, the purposes of which `will hereinafter appear. f

The ring tube which, as `is above noted, is reciprocable within the receptacle and is made of suitable wear-resisting material. For facilitat- 'ing the cutting or segregating of a'slugof abrasive, the front end of the firing tube -is interiorly chamfered as at |01 to make it sharp or, `if -dey,

-sired, the same may be exterior-ly chamfered. This is seen in Fig. 6. The rearend |08`ofthe ring tube threadingly lengages the valve, 'the latter being part of the firing tube reciprocating means.

This valve will now be-describedin'detail, `reference being had more particularly to'Figs. `6 and '1. `A cylindrical valve casing |-|0 is provided with 'a transverse wall Y|| so as to present a front chamber Whichissupplied'with compressed uid from-a flexible conduit ||2. The front end of Athe casing is interiorly recessed foraccommodatingan annular valve seat |-l'4 which -isretained 'therein by an exteriorly threaded `nut -`|'|5, and

which presents a forwardly extending interiorly v'threaded nipple for engaging the threads ofithe end |08 of the firing tube.

Adapted for coaction with the valve seat |`|f4 is 4the head ||1`of a valve, the stem H8 kof which is slidingly engaged by an apertured boss H9,

With reference to thebarrel I *valvefthe vrear-end of @the stem 'H8 vis Provided 75 'SCTCWS -being provided with a set screw 134. -lar actuates the valveopening means heretofore referred to.

Vbolted or otherwise secured lto -the lplate |28.

provided with a detent |45. lried by the plate v|42 is -a screw, `the bottom lof lthe valve casing and the firing tube. found 'that very little power is required to rotate 'is projected-out of the barrel 98.

lwith a slot |23 -w'hi'ch cooperates withfmeans *hereis provided Witha central aperture for slidingly engaging the firing tube 96. @ne end o'f a pair of cylindrical slideways |121 -isvof reduced diame- Ater and is accommodated by an opening ln'the plate |25 and secured in such opening `,by set The otherendof each of theslideways is similarly connected to a plate 428. Bolted vto the 4casing Il) `and slidingly engaging the slideways |21 is a pair Vof slideblocks |30 (see -Fig).

ner similar to that in which theslide'ways '|21 are 'connected thereto, -is a spacer rod 1| 32 rwhich slidingly `accommodates `a `collar |33, the :latter This col- -Such valve opening meanscomprisean arm 135 which projects through the slot `|23 offthe stern '|`|'8. As is more-clearly seenin Fig' the upper -end of thisarm sadapted 'forengaging the col- -'lar f| :i3-and the lower end of `thisarrn pivots-about forcesare transmitted for reciprocating thecasing and the firing tube.

For imparting such reciprocating forces, fthe source of power "99, heretofore mentioned, -is provided and is, by way of illustration, `an yelectric motor suitablymounted on a-plate |42, `the latter being pivotally vcarried byva plate H3 which is A vertical plate `|44. is secured to one side, asis seen in Figs. 5 and 6, of the centerof plate mlandis Threadingly carwhichen'gagesfthe detent forretaining plate M2 in any desired pivotal position. The motor, by

ksuitable means such as a vbelt indicated -lcy a Adottedline, rotates a pulley |46 (Fig. 6) which-is .connected to one end of a stub shaft |41, ithe other end of which is provided with avcrank'arm |40, the stub shaft being suitably rotatably 'journaled in the vertical pla-te IM. The crankarrn is provided with a counter balance M5. A connecting rod n| 5I pivotally interconnects the crank arm and the said bar 140. As is better seenin Fig. '1 the plates |28 and |43 present a vertical slot |52 l'for accommodating the connecting rod.

Thus, rotation of the pulley M6 reciprocates It has been the pulley and that a fractional horsepower inotor is entirely suitable. g For preventing seepage of abrasive and to prevent wearof the firing tube as it slides through the opening'of the plate |25, a suitable wiping lWasher |54 is vprovided and is preferably con- "nested to the plate |25.

It has been'indicated above that the slug olf abrasive upon leaving the ring `tube enters and Thisbarre'land its immediately cooperating yelements are supported by the front face of thev front flange H34 as by bolting and will now be described. Such bolting interconnects the ilange |04, a washer 155, a diaphragm ll, and a flange 58 of a guard tube or shell Il'al. The barrel is longitudinally movably supported within the shell i5@ and for this purpose the barrel slidingly engages apertured guide block 62, the latter being suitably secured to the shell.

The aperture of the washer 58 is convex rearwardly and outwardly as at IM, The Washer is of a composite structure, and that portion thereof which is convex is made of a very tough wearresisting stiff material and the flat body portion thereof is made of relatively ilexible material. The purpose of such composite structure will hereinafter appear.

The diaphragm ll is similar to the diaphragms l0 and is best seen in Fig. 9. flat disc provided with any desirable number of slits H31 which radiate from a central point.` As is seen in Fig. '7, when pressure is exerted on the rear face of the diaphragm the slitted portion thereof deforms or projects forwardly and prei sents a pluralityv of lips which enter the rear end i6@ of the firing tube. This end flares outwardly and is urged against the diaphragm by washer and spring means H0.

The operation of this alternative embodiment is as follows: e

Abrasive is supplied to the receptacle 95 through the intake lill and substantially cornpletely fills the former so that, when the firing tube is in the position seen in Fig. 5,-upon appli-- cation of power, the ring tubes will be driven or pushed through the abrasive so as to segregate therefrom or cut thereoutof and completely surround and enclose a slug of abrasive. During the segregating action the abrasive displaced by the ring tube backs up into the expansion charnber [U2 and into the intake. As the ring tube approaches the washer IE5, the forward portion of the abrasive within the tube becomes somewhat packed or the individual particles of abrasive constituting such portion become closer together' than such particles would if the receptacle were continuous. his packing is more marked when the firing tube projects into the aperture of the washer. The firing tube moves forward until it is in sealing relation with the convex surface of the washer and for insuring a good seal between the .firing tube and the Washer, the latter, due to the nexibility of the flat outer portion thereof, may be slightly displaced.

Ey means of set screw ita-i the collar 33 may beso adjusted that when such seal is suitably established, the valve is opened by coaction between the arm S36 and the collar. When the valve is opened, live fluid under high pressure rushes behind the slug in the firing tube and due to its initial pressure and expansion the slug is blown or exploded out of the firing tube, through the diaphragm and nally projected out of the barrel e8. The relationship of the various elements when a slug is being ejected or fired, is seen in Fig. '7. The breech member or ringtube 95 is preferably extended outside of the abrasive receptacle so that the valve I il may be spaced a sai'e distance from the chargev in the breech. lIhus When the breech tube has been moved forwardly to firing postion as. shown in Fig. 7 the length of the .slug or mass in the tube does not extend to the valve.

While the slug is passing through the dia- Itis a phragmthe said lips thereofv which are formed Aby the slits E51 flex forwardly into the outwardly lips terminate also ilexes forwardly. Such flexing urges the barrel forwardly against the tendency of the spring I'I to urge the barrel rearwardly. Thus during each firing cycle the barrelis reciprocated within the shell iit.

Devices constructed in accordance with this invention have successfully operated at a speed of 500 operating cycles per minute, so that 560 slugs per minute were ejected or blown out of the device. These slugs, it will be noted, are projected intermittently and ily as slugs from the barrel to the surface to be sandblasted. Upon striking such surface the slug will disperse and scatter as if it were a snowball.

Attention is particularly directed to the suddenness with which the air pressure is released into the rear end of the firing tube. The fluid `pressure within the firing tube cannot be released except by actuation of the slug because the slug completely fills the ring tube. ln other words, the fluid cannot escape around the slug, but must follow the slug. Thus, a very small quantity of fluid is required for each operating cycle to shoot the slug. Tlu's quantity may be as small as a few cubic inches as compared to several cubic feet which is required in a conventional sandblast nozzle device having a continuous stream of air passing through an open pipe. The ratio between small quantities of air used by my method and in my guns is as small as 1/100 part of the air for throwing the same quantity of abrasive by a sandblast.

't is to be noted that the diaphragm lE'i forms a seal at the front of the receptacle E5 and that no such seal is necessary at the rear of -the receptacle.

When the ring tube is sealed against the washer, a slug within the ring tube is completely segregated from the remainder of the abrasive within the receptacle and such a slug is substantially, completely and entirely projected, all without disturbing such remaining abrasive. The latter is uneiected and unacted upon by lluid pressure.

It is well known that the abrasive contacting parts of abrasive projecting devices are subject to enormous Wear. rThis is particularly true where the relative velocity is high. Thus, in my disclosure the firing tube and barrel are the elements of major wear. Ey constructing the device in sections and bolting the sections together, these elements may ber readily replaced. For instance, by removing the bolting which interconnects the elements llfi, 56, lill, and l58, the barrel, the diaphragm, the washer and the firing tube may be replaced in a very short period 0f time.

When devices of the character described operate at the speed described and project the abrasive upwadly, horizontally or slightly downwardly the diaphragm l5? may be dispensed with because the interval between each cycle of operation is too short for gravity to act on the slug sufdciently to move it materially.

The alternative construction seen in Figs. 11 and l2 is similar to that seen in Figs. 5, 6 and 7, and only the differences therebetween will be described, such differences being chiey in the provision of pneumatic means for reciprocating the firing tube. In this alternative construction compressed -uidpreferably air, recprocates a piston which in `turn ciprocates the firing tube. As the firing tube approaches the end of its forward stroke, a valve is opened Yand admits into the firing tube the compressed fluid which has actuated the piston.

To this end a cylinder |15 is provided with. a front flange |16 and a rear flange |11. An apertured bumper plate I 18 is interposed between anges and |16 and is suitably secured between and to these flanges as by bolting, riveting, or welding. c

The piston which reciprocates in the cylinder Ais itself a valve and comprises .a relatively thin cylindricalshcll I 80. The front end of the shell `is interiorly threaded for receiving a base IBI which is provided with a threaded central aperc a main source of fluid pressure |86 which, by

means of a control valve |81, communicates with an automatic valve indicated generally in Fig. 11 -by the reference character |89. This valve alternately directs the fluid pressure to one-side and then the other side of the piston.v The automatic valve is seen in detail inFig. 12 and comprises a casing |9| which is surrounded by a jacket |92 so as to provide a space between the casing and `the jacket.

The fluid pressure from the control valve |81 `is admitted to this space and bymeans of apertures |93 ows into the interior of the casing. It is to be noted that the interior |94 is cylindrical and that the holes |93 are in two circumferentially extending rows,` one at each end of the interior. The rear end of the casingthreadingly receives a hollow plug |96 which communicates withthe interior |94 and which by means of a conduit |91 communicates with thefront end of the ,cylinder |15 immediately adjacent the flange |16. The inner end of the plug |496 pre,- sents a valve seat which in the present instant is preferably spherical. interconnecting the front end of the casing |94 `and the rear end of the cylinder |15 is a conduit |99, the rear `end of which presents a spherical valve seat.

Adapted for coaction with these valve seats and disposed within the interior r4|94 of the casing is a ball 200, the diameter of which isV substantially equal to the diameter of the interior |94 so that fluid pressure vcannot pass from one of these series of apertures |93 around lthe ball to `the other series of apertures. These apertures are so located vthat the ball is alwaysbe'tween them. Thus, it is seen that when the ball is in the position seen in Fig. l2, fluid pressure is admitted against the rear of the vpiston and that when the ball moves to the left of Fig. 12 fluid pressure will be admitted against thefront of the piston. Y

Means will now be described for exhausting the iiuid pressure built up withinv the cylinder |15. As was heretofore said, the fpistonhas lan opening extending longitudinally therethrough, but `it is to be noted that such opening', by means 'of the firing tube 96, does not communicate with the forward portion of the cylinder |15. The piston, unless this opening is sealed, cannot be forced forwardly by Yfluid pressure. According `to this invention valve means are provided for sealing this opening and consequently, for permitting fluid pressure to build up behind the piston and force the same forwardly, such means also controlling the admission of fluid pressure to the interior of the firing tube 96.

This valve means, which is built into the piston, comprises a cup-like cap 202 which is vthreaded. to the base IBI and which presents an opening 293. Adapted'for seating on the rear surface of the base and consequently for sealing the aperture 'through the piston is a plate 205. Resilient means in the form of a spring 206 are interposed between'the p-late 205 and the cup 202 for normally maintaining the Opening closed. The `base isprovided with a Aplurality of circumferentially spaced openings for accommodating pins 291, the rear side of which are provided with enlarged heads. rlhe heads abut the plate v205 and serve the purpose of preventing the pins from working their way forwardly out of the opening; The pins project forwardly of the base .I 8| and are adapted for simultaneously engaging or rbumping the bumper plate |18 or unseating the plate 205 and consequently permitting the fluid pressure at the rear of the piston to enter the ring tube 96 and expand against the slug of abrasive for projecting the same out of the barrel S8; `ien the plate 205 is unseated, the pressure at the rear end of the cylinder is less than the pressure at the front end thereof and consequently the ball 230 will move from the position seen'in Fig. 12 to the left thereof and seat itself against the conduit |99. Thus the flow of'fiuid under pressure from the source |85 to the rear of the cylinder will be terminated and fluid under pressure will be admitted tothe front of the cylinder.

For exhausting fluid pressure from the front of :the piston, the cylinder is provided with a series of circumferentially spaced openings 208. These openings, lit will be noted, are uncovered by the piston only when the latter `occupies the extreme r-ear end of the cylinder |15 and are not uncovered when the piston is in the front end of the cylinder. These openings communicate with the interior of a hollow ring 299 which encircles .the cylinder and which communicates with the cylindrical interior of a valve casingZI. The front end of this valve casing is centrally bored so that the` casing has an opening extending there# through and presents a valve seat 2II which is surrounded by a coil spring 2|2. This spring urges rearwardly a piston 2|4 which is adapted for reciprocation within the said cylindrical interior of the Valve casing 2|0. The piston seats onthe seat 2|| and seals the hollow interior of .the ring 209 from the interior Kof the valve casing 2|0. Therear end of the cylindrical interior of the valve 2I0 threadingly receives a plug 2I6 which, in turn, threadingly receives a conduit "2|1 thelatter being in communication with the rearend of the cylinder |15.

From the foregoing it will be seen that when the piston which is within the vcylinder |15, the former in and of itself being a valve, is actuated forwardly, the iiuid pressure so actuating this -piston is by means of conduit 2I1 transmitted 'to the rear of the piston 2|4 and forces the latter against the seat 2| I. When the plate 205 is un- 'seatedthis pressure is released and the piston 12H is unseated land unseals or opens communication between the ring 209 and the interior of the valve casing 2 IQ. l

When the plate 205 is unseated, the ball 25|) moves to the left of Fig. 12 and fluid pressure is admitted to the fro-nt end of cylinder |75 by conduit |21. When vthe openings 298 are uncovered the pressure in the front of the cylinder |15 exhausts through these openings into the ring 29, into the interior of the casing 2|() and out of the forward end thereof. The uncovering of the openings 298 forces the ball from the left of Fig. 12 to the right thereof, thus sealing the piston 2|4 against the seat 2H and forcing the piston forwardly.

The moving back and forth of the ball 290 is extremely rapid and due to the unique construction and arrangement of various valves this alternative construction is cap-able of expelling as many as 500 abrasive slugs or wads per minute. The speed of operation of the device is dependent upon the fluid pressure admitted to the automatic valve |89.

The various elements which. comprise a device constructed in accordance with this alternative form of the invention may be very thin and the overall dimensions oi such a device are within the limits of portability. The entire device appro-ximates the weight of an ordinary portable electric drill.

The word abrasive as used herein is intended to embrace all materials which, when directed against a surface, have an elect thereon. Such material might be sand, metallic shot or grit, other granular material, polishing balls, such as leather pellets, or the like.

It is interesting to note that the slugs or wads of abrasive projected by the alternative forms of this invention are substantiaily cylindrical. This is because the firing tube is substantially cylindrical. The result is a segregated elongated projectile which flies from the tube nose or end iirst and strikes the surface to be abraded.

When an open air blast nozzle or a centrifugal wheel is used, the abrasive is projected as individual particles with substantially still air in between the particles, i. e., each particle encounters its own independent air resistance. If No. 50 steel grit is used there are approximately 75,500 particles per pound. With an open air blast or centrifugal wheel there would be '75,500 different .O07 gram projectiles spaced at random from each other. It will be Iobvious that the nozzle velocity is higher than the target velocity even though the projecting range or ying distance is but 2 to 3 feet. The same pound of abrasive would comprise six or less shots for the present invention. It is not diicult'to comprehend that abrasive projected by this invention surfers but little loss ci velocity due to air friction.

Other forms may be employed embodying the features of my invention instead of the one herein explained, change being made in the form or construction, provided the elements stated by any of the following claims or the equivalent of such stated elements be employed, whether produced by my preferred method or by Others embodying steps equivalent to those stated in the following claims.

I therefore particularly point out and distinctly claim as my invention:

1. In apparatus of the class described, a frame, an abrasive breech in said frame, means to intermittently feed abrasive to said breech in compact slugs, a displaceable valve member to retain the abrasive in said breech and a metering device to intermittently admit charges of air to said vbreech to expel said intermittent charges of abrasive in the form of compact slugs.

2. In apparatus of the class described, a frame, an abrasive breech in said frame, means to intermittently feed abrasive to said breech in compact slugs, a displaceable valve member to retain the abrasive in said breech, a metering device to intermittently admit charges of air to said breech to expel said intermittent charges of abrasive in the form of compact slugs and feed mechanism operated by said metering device to actuate said abrasive feeding means.

3. In apparatus of the class described adapted to project abrasive in compact slugs, a frame, an abrasive breech in said frame, a feed pipe for abrasive opening into said breech, a valve to intermittently open and close the said opening, power means to operate said valve, an air metering device opening into said breech, a reciprocable piston .in said device, power means to operate said piston in timed relation with said valve to admit a charge of air to said breech after a charge of abrasive has been fed thereto.

4. In apparatus of the class described adapted to project abrasive in compact slugs, a frame, an abrasive breech in said frame, a feed pipe for supplying abrasive to the opening into said breech, a valve to intermittently open and close said opening, power means to operate said valve, an air metering device opening into said breech, a reciprocable piston in said metering device, a member connecting said piston and said valve to operate the valve by reciprocation of the piston and power means to reciprocate said piston in timed relation with said valve to admit a charge of air to said breech after a charge of abrasive has been fed thereto in a compact slug.

5. In apparatus of the class described adapted to project abrasive in compact slugs, a frame, an abrasive breech in said frame, a feed pipe for supplying abrasive to the opening into said breech, a valve to intermittently open and close said opening-power means to operate said valve, an air metering device opening into saidy breech, a reciprocable piston in said metering device, a member connecting said piston and said valve to operate the latter by reciprocation of the former, a source of high pressure air, means actuated by said air pressure source to reciprocate said piston in timed relation with said valve( to admit a charge of air to said breech after a charge of abrasive h as been fed thereto.

6. In apparatus of the class ldescribed adapted to project abrasive in compact slugs, a frame, an abrasive breech in said frame, a feed pipe for supplying abrasive to the opening to said breech. a valve to intermittently open and close said opening, power to means to operate said valve, an air metering device opening into said breech, a reciprocable piston in said metering device, a member connecting said piston and said valve to operate the latter by reciprocation of the former, a source of high pressure air, means actuated by said air pressure to reciprocate said piston in timed relation with said valve to admit a charge of air to said breech after a charge of abrasive had been fed thereto, and control' mechanism to vary the proportion of air used to operate said piston with respect to the amount of air fed to said abrasive breech.

7. In apparatus of the class described, a frame, an abrasive breech in said frame with a pair 0f inlet openings andan outlet opening, a barrel amaai carried by said frame coactingwi'th said outlet opening, a feed pipe for abrasive emptyinglintc one of said inlet openings, a reciprocable plunger to intermittently open and close said opening and feed abrasive to Vsaid breech in a compact slug-g an air metering device with a hollow cylinder opening into said other vinlet toy the breech,=apiston reciprocable in said cylinder, means fto -re ciprocate said piston, adischarge passage opening in said piston to open and close the second named inlet to said breech, land a source of-air under pressure leading to said cylinder and admitted to said breech intermittently of saiddischargefpassage. l j

B. In apparatus of the class described, a frame, an abrasive breech in said framewitlr apairaof inlet openings vand an youtlet opening, a barrel carried by said frame coactingl with said `outlet opening, a feed pipe for abrasive emptying into one of said inlet openings, a'reciprocable plunger to intermittently open and close'said opening and feed abrasive to said breechin acompact slug,an air metering device with a hollow cylinder opening into said other inlet to the breech, a piston reciprocable in said cylinder, fluid intake and exhaust ports at each endof said cylinder, an air jacket discharging to each pair ofk intake ports, an air supply source leading to said jacket, valve mechanism to regulate the amount of airia'd` `mitted to said jacket, valve` rings carried by said piston and adapted to seal said intake and exhaust ports, a discharge passage insaidpiston to open and close the second named inlet to said breech, and a source of air under pressure leading to said cylinder andmetered by` said piston discharge passage. ,n

9,. In adevice of the characterfdescribed, the combination of an abrasive` receptacle: means projecting in said receptacle 'for segregating and packing a quantity vof abrasives@ to form a packed slug, and means 'for projecting 'the packed slug as a slug out of the device, i

10. In .apparatus adapted to project abrasive in compact unsupported slugs against an object, a frame with a discharge passage spaced from said object, an abrasive breech in said frame, positive means to forcibly feed abrasive to said breech in compact slugs, a source of compressed fluid under pressure and a metering device to intermittently admit charges of air to said breech to expel intermittent charges of abrasive.

1l.. In apparatus adapted to project abrasive in compact unsupported slugs against an object, a frame with a discharge passage spaced from said object, an abrasive breech in said frame, means to feed abrasive to said breech in compact slugs, means to retain said abrasive in said breech when said breech is positioned out of horizontal position, a source of compressed fluid under pressure and a metering device operated by said air blast to intermittently admit charges of air to said breech to expel intermittent charges of abrasive against the work.

12. In apparatus adapted to discharge abrasive in relatively compact slug-s toward an object to be cleaned thereby, a frame, an abrasive breech in said frame. positive means to deposit successive charges of abrasive in said breech in compact slugs, to retain said abrasive in the breech when said apparatus is tilted and a metering device to pass air under pressure through said breech and past said retaining means to discharge abrasive from said. apparatus toward an object. f

13. In apparatus adapted to discharge abralsive in relatively compact slugs toward an .object to be cleaned thereby,l aframe, an abrasive breech in said frame adapted toreceive a charge of abrasive to be projected, positive `abrasive feeding means to deposit successive-charges of abrasive in lsaid breech, means to retain the charge of abrasive in said breech and means to admit fluid under pressure to said breech to si'- multaneously open said retaining means and project said abrasive `from said apparatus, and timing mechanism interconnecting said abrasive feeding means and fluid admitting means to feed abrasive and fluid to said breech in timedrclation to eachother. l i "r 14. In apparatus adapted to 'discharge abrasive in relatively compact slugs toward `object to be cleaned thereby, `a frame, an abrasive' breech in said frame adapted to receive a charge of abrasive to be projected, positive abrasive feeding means to deposit successive charges of abrasive in said breech, `means to admit fluid under pressure to said breechto project said abrasive from said apparatus, and'timing mechanism interconnecting said `abrasive feeding means and fluid admitting means to feed abra'- sive and fluid to said breech in timed'relation toeachother. f i' 15. In abrasive, projecting apparatus the. combinaticn of an abrasive receptacle, `.an axially reciprocable firing tube `one end of which ris openand projects ink said receptacle, piston and cylinder'means forre'ciprocating said firing tube,l said pistonhaving an axial opening therethrough, the-'other end of said` firing `tube being open and secured to said piston in communication with the opening of the latter, a cap for covering and uncoveringr the Aopeningof said piston,` and means adapted for; abuttinfr `one end of said cylinder for actuating said capinto uncovering position whereby fluidundcr pres-V sure from the firing tube remote side of said piston is admitted to said ring tube for projecting abrasiveout of said `firing tube.

16, In abrasive projecting apparatus,Y the combination of an abrasive receptacle, an axially reciprocable ring tube one end of which is open and projects in said receptacle, piston and cylinder means for reciprocating said ring tube, said piston having an axial opening therethrough, the other end of said rng tube being open and secured to said piston in communication with the opening of the latter, a cap for covering and uncovering the opening of said piston and resiliently urged into covering position, means for admitting fluid under pressure to the other side of said piston, and means for intermittently actuating said cap into uncovering position.

1'7. The combination of an abrasive receptacle provided with a pair of openings the Surface of one of which is flexible and convex rearwardly and outwardly, an axially movable iring tube projecting through the other of said openings, the front end of said ring tube being adapted for seating against said convex surface for sealing the interior of said tube from the remainder of said receptacle, and means for admitting duid under pressure to the rear end of said firing tube.

18. The combination of means including an abrasive receptacle provided with a pair of openings the surface of one of which is flexible and convex rearwardly and outwardly, an axially movable firing tube projecting through the other of said openings, the front end of said firing tube being adapted for seating against said convex surface for sealing the interior of said tube from the remainder of said receptacle, and slitted flexible pressure responsive means for sealing said one of said openings.

19. The combination of an abrasive receptacle having an opening, a exible slitted washer for closing said opening, a barrel one end of which flares and is adapted for circumscribing the slit of said washer, and means for admitting fluid under pressure to said receptacle whereby abrasive within said receptacle is projected outwardly through said opening, through said washer by displacing the slit thereof with the lip of such slit conned by said end of said barrel, and finally through said barrel.

20. The combination of an abrasive receptacle having an opening, a slitted resilient'washer for closing said opening, an axially movable barrel one end of which is adapted for circumscribing the slit of said washer, resilient means for urging said barrel against said Washer and means for admitting fluid under pressure against the abrasive within said receptacle whereby such abrasive is expelled through said opening, through said washer by displacing the lips of the slit thereof against said end of said barrel, and nally through said barrel.

21. A method of throwing measured masses of cleaning abrasive in rapid succession, comprising the steps of forcing a measured amount of abrasive through an opening into a breech chamber in a gun and then closing said opening and while closed releasing a sudden charge of com pressed air behind the abrasive mass to expel it from the gun and repeating the cycle of said steps in quick succession.

22. An abrasive gun for rapidly throwing separate dense charges of abrasive and having a ring barrel and a charge holding breech, a supply means for bringing abrasive to the breech, coacting elements for loading a dense measured load of abrasive from the supply into the vbreech and for closing the breech, means responsive to the movement of said elements for releasing a charge of compressed air behind the load only while the breech is closed.

23. The combination of a gun having a nozzle and charging chamber, a compressed air supply and abrasive supply, means for mechanically charging the chamber while separating a measured mass of abrasive from the supply and for closing the chamber, valve means for suddenly delivering a charge of compressed air to the chamber to eject the charge of abrasive as a mass, and an interconnecting control operating mechanism responsive to the chamber closing means to assure closing of the charge chamber before delivering the compressed air, and means for shutting oif the air immediately after each discharge. Y

24. A repeating abrasive slug throwing gun in cluding a firing tube and a breech load-carrying tubeymeans for relatively moving said tubes axially, means for presenting a mass of abrasive between the tubes when separated whereby when moved together a measured mass of abrasive is contained in the breech portion and isseparated from the mass and the opening between the tubes is closedto prevent escape of abrasive or air, and means responsive to the tube movement for delivering an explosive charge of compressed air to the mass when the tubes are in said closed position. f

25. An abrasive throwing gun having an opening breech and an ejecting passage, a repeating mechanism for forcibly moving a mass of abrasive into the breech when open and thereafter closing the gun except for free movement through the throwing passage to prevent lateral movement of abrasive, repeating means for releasing explosive air charges through the passage, and timing means causing such release only when the breech is closed and whereby the mass is forcibly ejected in a dense charge, the time of air flow constituting a small fraction of the time of the cycle including the charging and closing.

NELSON J. QUINN.

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