US2521782A - Abrasive blast marking machine - Google Patents

Description

Sept. 12, 1950 Filed May 28, 194'! INVENTOR P. L (4 JOSEPH M.ESCHER Sept. 12, 1950 .1. M. ESCHER ABRASIVE BLAST MARKING MACHINE 2 Sheets-Sheet 2 Filed May 28, 1947 Patented Sept. 12, 1950 A ENT- orncs B AswE BLAST momma Joseph M. Escher, Mount Qliver, Pa", assig or to Jas. H. Matthews & Co.,Pittsb urgh,"PaJ, acornotation of Pennsylvania A nea m y as, 1947, Serial No. 750,945

is v tion re a es to abrasiv b a t m ils 111 machines; es e ally such machin s i wh c an abras ve blast is employed fo marking aruo es. a r o ted aslslor stenci be ns disposed over the portion of'th'e' article toward Whiehthe blast is directed so that the article is predeterminedly marked 'by impingement of abrasive par,- ticles a ainst the rti e th ough t e nerfijo ations in the mask or stencil. Machines .of the type ment o ed a e u d widely o plyin ra emarks and'other indicia to articles made of variu materials, be n mar y emp yed o the marking'oi metal articles. h Machi s o th ene al ime ab e ref red to 'whiQh have heretofore been vemployed have been subject to certain disadvantages. A relatively concentrated blast will treat only a small surjace area at ,one time. Consequently. it is desirable to provide for relative movement be, tween the axis of the blast and the worl; being treated so that the blast, will act .on the area of the work which it is desired to treat. To that em a he et re b en pro e t -m unt on ma hin f m a s i a a nst w ich work to be treated by the blast is adaptedtto be postin guides. This .is u sat fa to y first becaus the abrasive gets into the guides and interferes wi r e o e ati o he, id and seco dhacause the abrasive works its way out between i th sli and th f ame a d contamin e the u r undin air to the detriment t e h th of workmen and the cleanliness of the shop. or r abras e l s ma ki g mac i es as heretofore proposed "have been wasteful of abras ve hi h avib uit e'xpens ve. c

' I have deyised'an abrasive blastmarkl l machineobviating the disadvantages above pointed out which havebeen inherent in such machines as heretofore proposed. "I provide for substantially frictionless m v m nt o the head a ainst which the work is positioned jor treatment by theblast and -I confine the abrasive within the machine so that it cannot work its way out into the surrounding atmosphere. "I filter from the abrasive theair used for creating the blast and reuse 'the'-"abrasive, maintaining it at all times in achamber in the machine.

I provide, in an abrasive'blast marking ma.- chine having a nozzle, means for discharging an abrasive blast through the'nozzle and a head 'against which work to be treated 'by the blast may b e-positioned, supporting means for the head includinga fiexible'portion enabling substantially frictionless movement of the head relatively to the-nozzle in a direction transverse of the direction of the blast. The supporting means for the headpreferably includes a-n elongated supporting member at ieasta portion of which. flexible, said member extending generally paral- 'lel-to'the direction of the blast. I desirably em- P a a lura i f on ated s pportin me rs so' ones ne l bo h nozzl and 1. as lea tv a or on wh h is fle The iippor inemembers a ta t e form 5 of ostsleaoh s vin -a l a t a por n Q its length consisting of a piece of flexible tubing ma .emnlo plu al y of pos on ei d With the base o nam o h m chin s osed about th nozz o bla nd i e era l para w lation h he e to et e w th a plu al of s connected with th head an a p u a i of .pieoes o lexible ubi ch emb ac n an eri o on o the t men io pos nd an e d o one .o jt s somi m n oned t Mor specifically ea h ofthe elonga e supp n momb ers for the head may comprise .a rod "at each and and a d n e mediat th fir t men oned iiqfis and two iengthsof flexible tubing each e ns br r et os d l nd ston o h r -mead ro andthe secon en i ed se .Iiurther provide, in an abrasive blast marking ma hin ha in a .no le .,.mea or r iseh re ae mi s t i no le la t o i d-ab tai i e aab a head again t whi h w k to be t at dby t blas be pos oned a a ne ion s a te loonne ted w thtlie hea and into whi the n zzle d ch es so tha t e i om nent of the blast s es out of aid chamber. hil the abrasive component remains within said cha nsher. .I de ir y provide an ab a ive rec ta l he ai er iou ham c mm nieet e th the hea a t e r c a e some? e ai so reo i nt 1 h lasi nas es out of the n ma?! whi the b as com onen isr urn a o the mo n-t ble til .fu ther r ide, n n ab a v blast markin m thin havin -an a a v rec pta le. an je tor extend n u waralv through t eatre sir eoertac ea o r Of comp ess a n- ,n t o i ro sth sourc o com re ed a r to the ar o so tha a blas a r with nt a eda a si e iro the e epta le is .diseha ged' u wardly throu h the eje or and a hea a ai st whi h o be t a d'h t e la t ma bepos t ne l a v pu m te a sea g th ece a le to h e??? i li nm an air-De u cham er into whiclithe ejector discharges so that the air component of the blast passes out of said chamber w i th ab as ve om enentslrqosbaek th; receptacle" The air-pervious materials s pref ,e 'a yx e h ma h .iu rtionios t filter riom' h tra ne abrasiv in the same manner as a vacuum cleaner filters air from the entrained" dust and dirt which it draws in. The e i .ai -ne vi u mate ialis i s ecial at tase. wh se ier or h 'iat enerv atra re n p sat t e b om and he movabl as tithe o a er i thu f rm a dosed chame 'whw ain a neds sed n all-r at v P9- s t on eit e hsa andr oenta le- *I preferab'lyprovide means for limiting move- 2 5 tioned, the slide being movable back and iorth ment of the head transversely of the blast, such means being adjustable so that the movement of the headmay at, all times be. confined between desired limits. I also provide for restraining the head against turning movement, allowing it free- In the accompanying drawings I have shown a present preferred embodiment of the invention, in which i Q'fFigure 1' is a vertical cross-sectional view through an abrasive blast markin machine;

: Figure 2 is an elevational view of the marking machine as seen from the right in Figure 1;

Figure 3 is a top plan view of the marking machine; and j'Figure 4 is a fragmentary vertical cross-sectional view of a portion of the machine.

Referring now more particularly to the drawings, there is provided a base 2 mounted on feet 3 and to which is bolted by bolts 4 a generally cylindrical support -5 having a flanged bottom 5 through which the bolts pass. The support 5 has a vertically arranged central bore 1 which is interseated by a lateral opening 8. Seated upon the support 5 is an abrasive receptacle 9 having at its bottom a downward projection extending into the bore 1 of the support 5, Through the projection I0 is a vertical bore H. The receptacle 9 flares from relatively small horizontal cross-section adjacent its bottom to relatively great'horizontal cross-section adjacent its top and has at its top a vertical cylindrical rim i2.

There is provided a source of compressed air. The air may come from any suitable compressor and enters the marking machine through an air inlet pipe l3 which enters an elbow M which in turn enters the bore H in the downward projection Ill of the abrasive receptacle 9. An air tube 15, enters the top of the bore I l and projects vertically; having an ejector It at its upper end whose function will presently be described. An abrasive tube I! surrounds the air tube I and seats on the bottom of the receptacle 9. An annular passage I8 is provided between the outside of the air tube I5 and the inside of the abrasive tube 1 1 'through which abrasive is adapted to be drawn upwardly by the ejector as will presently be described. Suitable set screws iii are threaded into the abrasive tube and bear against the air tube 4 tacle 9. At its upper end the abrasive tube I7 is provided with a blast nozzle 2| maintained in place by a set screw 22.

Disposed in the abrasive receptacle 9 is'flnely divided abrasive material 23. This may be any suitable abrasive material, as, for example, sand, metallic abrasive, etc. It lies in the receptacle 9 to a substantial depth, the abrasive adjacent the tube I! being adapted to pass through the openings 26 to enter the annular passage 18. When compressed air passes upwardly through the tube I 5 and the ejector 16 at high velocity it draws abrasive from the abrasive receptacle 9 through theopenings 20 and upwardly through the passage I8 so that a blast of air and entrained abraslve issues athighvelocity from the mouth of the and'seats against the flange 34.

: 4 nozzle 2|. This abrasive blast is adapted to impinge. on rnaterial to be marked, the impingement of the abrasive against the surface of the material marking it in characteristic manner.

- The abrasive produces a series of fine pits in the surface of the material giving the material an etched appearance.

Fastened to the outside of the tube l1 within thereceptacleS isa flange 24 whose diameter is somewhat less than the diameter of the receptacle 9 in the vertical plane of the flange. A vent or breather tube 25 extends vertically through the flange 24 at a point near the tube H and has its upper end disposed above the top of the receptacle 9. The purpose of the tube 25 is to prevent the formation of a vacuum in the bottom of the abrasive receptacle 9 which might interfere, with passage of the abrasive through the openings 20 and up through the annular passage IS.

The flange 24 is provided with a number of bores 26 spaced about the tube ll, four such bores being shown in thedisclosed embodiment of my machine. Each bore 26 receives the reduced lower end 21 of a pin 28, the enlarged body portion of the pin projecting upwardly from the flange 24. A length of flexible tubing 29, as, for example, rubber tubing, is disposed about each pin 28 but projects upwardly a considerable distance above the top thereof. Four rods 30 are provided, each having an enlarged central portion 3| and reduced upper and lower extremities '32 and '33, respectively, with a flange 34 below the upper extremity 32 and a flange 35 above the lower extremity 33. The lower extremity 33 of each of the rods 30 fits into the upper end of one of the tubes 29, the flange seating on the top of the tube. A length offlexible tubing 36 fits over the upper end 32 of each of the rods 30 The head of the machine comprises a generally cylindrical member 31 having at its bottom a flange 38 provided with four bores 39. The reducedupper end 40 of a pin 4! enters each of the bores 39 from the bottom and the body of each pin 4| projecting downwardly from the flange 38 fits. into the upper end of one of the tubes 36. Thus the head is supported by the four elongated flexible supporting members or posts each comprising a pin 28, a tube 29, a rod 30, a tube 36 and a pin 41. The postsjare made flexible by the provision of the tubes 29 and 36. The head is normally supported by the posts so as to be coaxial with the nozzle 2! but may be moved transversely with respect to the axis of vthe nozzie and hence transversely with respect to the direction of the blast toldispose difierent surface portions of the work to be marked in positionto be acted on by the blast.

Screwed to the top of the member 31 by screws 42 is an annular plate 43. Screwed to the plate 43' by screws 44 is a cap member 45 having through its top a Window or opening 46. A gasket 43a is disposed between the plate 43 and the cap member 45 toseal the same together. The member- 45 may be replaced by similar members with diflerent sized and shaped windows 46. The size and shape. of the window 46 is determined by the size and shape of the markings to be applied by the machine. An article to be marked has a mask or stencil positioned over a surface thereof and the article and mask are laid on top of the member 45 with the mask downwardly so asto bridge acrossthe window 46. The mask is perforatedso that the blast will make the desired marking on-the article through the perforations in the-ma'sk. 1

Fastened to the under surface of the plate 33 bystraps 41 is a rod 48. The rod lies in a-ho'rizontallplane and has both of it's ends projecting from. the plate 43 as shown in Figure 3-. Fastened to the machine frame by screws 49 is a plate 50 to which is fastened at its inner surface an angle I Projecting upwardly from the angle 5i isa bar 52. Disposed about the top and side faces" of" the bar' 52 is a U-sha-ped rubber strip 53'. Mounted upon the rubber strip '53is a plate El the bottom of whichha'sasaddle 55overlying and embracing the U-shaped rubber strip 53. Thus the plate 54 is in effect mounted for pivotal movement about a horizontal axis extending ap proximately along the top of the bar 52, the resiliency of the U"-sh'aped rubber strip 53 enabling such movement of the plate 54.

Projecting upwardly from the plate '54 are two spaced. apart vertically elongated eyelets 56 throughwhich the rod 48 passes. -A stop mem- 1361755 in the form of a sleeve is slipped over each end of the rod 38 and maintained in adjusted position-by a 'set screw 53. The machine frame has-atop 59 in which are formed two parallel elongated openings 6%- through which the eyelets 56 pass. Pivotal movement of the plate 5 1 is accompanied by movement of the rod 48 generally a horizontal direction perpendicular to the axis;of the rod, such movement of the rod being accompaniedbyconsonantmovement of the head t -the machine. The head may also be moved back and forth in the direction of the length of therod 48, the rod sliding within the eyelets 5c.- The eyelets 56 are vertically elongated to provide for angular movement of the plate 54 while the head. moves in a generally horizontal direction perpendicular to the bar 52-. Movementof the head in the *direction of the length of the rod 48' is limited by the stop members 57 one of which at each limit of suchmovement strikes one of the eyelets 56.

. The frame has a horizontal slot 6| iniits rear face near its top. -A-n L shaped member 62 has one leg extending downwardly. 'from. the top-of the, machine overlapping the: slot tiand another leg overlying the -top"5=9- of the frame. set screw 63 passes through the downwardly eriteii'ding leg of the member 62 and enters the sl'ot B1 and is adapted to maintain the member 62 in desired adjusted position longitudinally or thexslot 16!. The horizontal flange of themem ber 62 has a V-shaped notch 64 therein, one or the -eyelets-56-lying within that notch. The membcrxGZ limits movement of the head generally horizontally at right angles to the length of the rod- 48. With respect "to Figure 3, the farther to thev right the member 56-2 is positioned the greaterwill bethe amplitude of movement allowed the headin the horizontal, direction perpendicular to the lengthof the rod :48.

I The stop members 5-? :and .52 as-shown in the drawings are positioned to hold the head stationary so that it cannot partake of any horizontal movement. Each of the stops 5'! isitouch-in'g the. outer surface of one of the eyelets 55, this preventing movement of the rod 28 longituwells and the member E2 is disposed as'fa'r as it will .go toward the left, viewing Figure 3, so that the eyelet 56 is disposed atthe'b'ottom of-the crotch of the V, thus holding the 'head against movementin a horizontal plane at right angles to the lengthof the rod 48. Any desired ampli-r bugle of movement of the head longitudinally or the rod-4e may be prov lded iorby moving the stop members 51 outwardly on: the-rod. Any dcsired-movement of 'thehead horizontally at right angles toth'e rod-48 may be-provided for by mov ing them leer 62= towardtherightwiewingFigui'e 3,'-tli1i1s posiuonmge wider-part of the V shaped notch 6 opposite the eyelet 56 and allowinggreater. amplitude of generally pivotal movement bf'th'e'plateh'l.

There" isforrned between the flange S'S o fthe head and the rim T2 of the receptacle '9 an abrasiveconfini-ng chamber by disposing a bag of flexible air-pervious material thartabetween. "The structure of the bag does not constitute the present "inventionso it not shown ohdescribedin detail. The bag-isshown more or less diagram matically in Figure '1 as a tapered sleeve open at both ends. The'air perviousbager sleeve is designated by reference numeral 'li li and may, for example, be of -fab'ric' such as the material com monly used for making vacuum -cleaner"bags. The sleeve is applied with sufiicient fullness that movement of the 'head as far asthem'echa ni'sm'will permit doesnot stretch the sleeve. The air from the blast is filtered through the sleeve 65. the abrasive at all tim'es're'maining in the chamber formed thereby. The top andbottom ofth'e sleeve maybe-clamped respectively to the flange 38 and the rim l' 2 byanysuitable clamping means, not shown.

There is provideda' valve "for opening and closi'ri'g the-air inlet I3, tha-tvalve conveniently 'bei'ng controlled, electrically or otherwise, by. a treadle' adapted t'o' 'be depressed by the operators foot and-operative when depressedtobpen the valve. 'The operator positions atop'theheadiandj so as to bridge the-window an article to be marked with a mask over its bottom surface and thenopens -the-air valve. The'air moves up'-' wardly thr'oughthe air 'tube'lliat high velocity and passes thro'ugh the ejector I e andthe' nozzle 21 Ih'e ejector creates a vacuumin the 'annular passage [8 between the air 'tube [5 and the abrasive tube 17 and abrasive is drawn up through that annular passage and is'entrained w'ith th'e'airat theupper extremityof the ejector I 6 so I that a blast of air with entrained abrasive' is discharged upwardly through the'n'ozzle 2 If it is desired td'mark awider'area o'f-the work than can be marked'when theh'ead is stationary with respect'to the nozzle the head is moved relati-vely to'tl'ie nozzle in a generally horizontal planev farenoug-h ftoallow the blast to impinge on all of the surfaceof the work'which is'to be marked. To' prevent greatermovement of the head than is necessary for'completemarking of the article the stops 5! and E2 are appropriately set. "The abrasive afterimpinging" on the work drops backdown within the 'ehamberto the receptacle 9, the air being-lilteredo ut; through the sleeve 65'. 'I hus' -the abrasive is at an times confined within the chamber and'i's continually reused! The" air is 'l ilter'ed outand there is' no contamination by abrasive'bf theatmOsphere-oi" the shop. As long as the work is held tightly'over the window 1 36 there is no way for abrasive'toescape 'int'o'the atmosphere. The head may be very'easily moved by' sli'g ht pressureof'the operator's hands, its movement-*being "substantially 'frictionle'ss :by

reason of the provisionof the flexible "tubes29' am ss.

Althoug-h themovement-of the head has been referred to as substantially horizontalfthe "head may tilt somewhat du'ii-ng fits generally horizontal movement. The-movement is' relativelylimited' and although not exactly horizontal issubstan-e tially so anclior practical purposes may be regarded as horizontah The plate 54 .with the eyelets B and the rod 48 restrainthe head from twisting or turning movement so that, the head is movable generally horizontally but with fixed orientation in the horizontal plane. I

While I have shown and described a present preferred embodiment of the invention it is to be distinctly understoodthat the invention-is not limited thereto but may be otherwise variously embodied within the scope of the following claims.

I claim: 1. In an abrasive blast marking machine having a nozzle, means for discharging an abrasive blast through the nozzle and a head against which work to be treated by the blast may be positioned, supporting means for the head including a flexible supporting portion enabling substantially frictionless movement of the head relatively to the nozzle in a direction transverse of the direction of the blast.

2. In an abrasive blast marking machine having a nozzle, means for discharging an abrasive blast through the nozzle and a head against which work to be treated by the blast may be positioned, supporting means for the head including an elongated supporting member at least a portion of which is flexible, said member extending generally parallel to the direction of the blast, whereby the head may be substantially frictionlessly moved relatively to the nozzle in a direction transverse of the direction of the blast.

3. In an abrasive blast marking machine having a nozzle, means fordischarging an abrasive blast through the nozzle and a head against which work to be treated by the blast may be positioned, supporting means for the head including a plurality of elongated supporting members positioned generally about the nozzle and each having at least a portion which is flexible, whereby the head may be substantially frictionlessly moved relatively to the nozzle in a direction transverse of the direction of the blast.

4. In an abrasive blast marking machinehaving a nozzle, means for discharging an abrasive blast through thenozzle and a head against which work to be treated by the blast may be positioned, supporting means for the head including a plurality of posts positioned generally about the nozzle, at least a portion of the length of each of the posts consisting of a piece of flexible tubing, whereby the head may be substantially frictionlessly moved relatively to the nozzle in a direction transverse of the direction of the blast.

5. In an abrasive blast marking machine having a base, a, blast conduit projecting from the base, means for discharging an abrasive blast through the conduit and a head against which work to be treated by the blast may be positioned, supporting means for the head including a plurality of posts connected with the base disposed about the conduit in generally parallel relationship thereto, a plurality of posts connected with the head and a plurality of pieces of flexible tubing each embracing an end of one of the first mentioned posts and an end of one of the second mentioned posts, whereby the head may be substantially frictlonlessly moved relatively to the nozzle in a direction transverse of the direction of the blast.

p 6. In an abrasive blast marking machine having a nozzle, means for discharging an abrasive 8 blastthrough the nozzle and a head against which work to be treated by the blast maybe positioned,- supporting means for the headincludin aplurality of elongated supporting members positioned generally about the nozzle in generally parallel relationship thereto, each of the elongated supporting members comprising a rod at each end and a rod intermediate the first mentioned rods and two lengths of flexible tubing each embracing the opposed ends of one of the first mentioned rods and the second, mentioned rod, whereby the head may be substantially frictionlessly moved relatively to the nozzle in a direction transverse of the direction of the last.

7. In an abrasive blast marking machine havin a nozzle, means for discharging through the nozzle a blast of air and abrasive and a head against which work to be treated by the blast may be positioned, means mounting the head for movement transversely of the nozzle and an airpervious flexible sleeve forming. a flexible airpervious chamber connected with the head and which flexes upon movement of the head and into which the nozzle discharges so that the air component of the blast passes out of said chamber while the abrasive component remains within said chamber.

.8. In an abrasive blast marking machine having an abrasive receptacle, an ejector extending upwardly through the abrasive receptacle, a connection from a source of compressed air to the ejector so that a blast of air with entrained abrasive from the receptacle is discharged upwardly through the ejector and a head against which work to be treated by the blast may be positioned, a plurality of flexible elongated sup porting members for the head, said members be ing positioned generally about the ejector in gen-- erallyqparallel relation thereto so that the head maybe substantially frictionlessly moved relatively to the ejector in a direction transverse of the direction of the blast and air-pervious flexible material sealing the receptacle to the head to form an air-pcrvious chamber into which the ejector discharges so that the air component of the blast passes out of the chamber while the abrasive component drops back into the receptacle.

9. In an abrasive blast marking machine, an upwardly open abrasive receptacle, an air tube extending upwardly through the receptacle with its interior out of communication with abrasive in the receptacle, an abrasive tube surroundingthe air tube, the interior of the abrasivetube' means whereby a blast of air through the air tube causes abrasive to be drawn from the recep tacle through the annular space between the abrasive tube and the air tube to be entrained with the air to form a blast of air and abrasive which is discharged upwardly, a head against which work to be treated by the blast may be positioned, a plurality of flexible elongatedsup' porting members for the head, said members extending upwardly from within the receptacle and being positioned generally about the abrasive tube in generally parallel relation thereto so that the head may be substantially frictionlessly moved relatively thereto in a direction transverse of the direction of the blast, and air-- pervious flexible material sealing the receptacle to the head to form an air-pervious chamber into which the blast is discharged so that the air com ponent of the blast passes out of the chamber while the abrasive component drops back into the receptacle.

10. In an abrasive blast marking machine having a nozzle, means for discharging an abrasive blast through the nozzle and a head against which work to be treated by the blast may be positioned, supporting means for the head carrying the head for movement relatively to the nozzle generally in a plane transverse of the direction of the blast and means connected with the head permitting movement of the head in any direction generally in said plane but maintaining the head against substantial turning movement in said plane.

11. In an abrasive blast marking machine having a nozzle, means for discharging an abrasive blast through the nozzle and a head against which work to be treated by the blast may be positioned, flexible supporting means for the head carrying the head for substantially frictionless movement relatively to the nozzle generally in a plane transverse of the direction of the blast and guide means for the head maintaining it against substantial turning movement in said plane.

12. In an abrasive blast markin machine having a nozzle, means for discharging an abrasive blast through the nozzle and a head against which work to be treated by the blast may be positioned, flexible supporting means for the head carrying the head for substantially frictionless movement relatively to the nozzle generally in a plane transverse of the direction of the blast and means for limiting movement of the head generally in said plane in each of two directions generally at right angles to each other, said means being adjustable so that the limits of movement of the head in each of said directions may be changed as desired.

13. In an abrasive blast marking machine having a frame, a nozzle mounted in the frame, means for discharging an abrasive blast through the nozzle and a head against which Work to be treated by the blast may be positioned, flexible supporting means for the head carrying the head for substantially frictionless movement relatively to the nozzle generally in a plane transverse of the direction of the blast and guide means for the head including an elongated guide member connected with one of the frame and the head, a guide device connected with the other thereof cooperating with the elongated guide member for guiding the head for movement generally in the direction of the length of the elongated guide member and stop means on the elongated guide member adapted to engage the guide device to limit movement of the head in said direction, the stop means being adjustable along the elongated guide member so that the limits of movement of the head in said direction may be changed as desired.

14. In an abrasive blast marking machine having a nozzle, means for discharging an abrasive blast through the nozzle and a head against which work to be treated by the blast may be positioned, flexible supporting means for the head carrying the head for substantially frictionless movement relatively to the nozzle generally in a plane transverse of the direction of the blast, a member mounted for substantially pivotal movement about an axis substantially parallel to but offset from said plane, said member intersecting said plane, and connections between said member and the head permitting movement of the head in said plane but maintaining the head against substantial turning movement in said plane.

15. In an abrasive blast marking machine having a frame, a nozzle mounted in the frame, means for discharging an abrasive blast through the nozzle and a head against which work to be treated by the blast may be positioned, flexible supporting means for the head carrying the head for substantially frictionless movement relatively to the nozzle generally in a plane transverse of the direction of the blast, a member mounted in the frame for substantially pivotal movement about an axis substantially parallel to but olfset from said plane, said member intersecting said plane, an elongated guide member connected with one of said first mentioned member and the head and extending generally parallel to said axis, a guide device connected with the outer of said first mentioned member and the head cooperating with the elongated guide member for guiding the head -tor movement generally in the direction of the length of the elongated guide member, movement of the head at right angles to the length of the elongated guide member being aocompanied by pivotal movement of said first mentioned member, said first mentioned member, the elongated guide member and the guide device cooperatively maintaining the head against substantial turning movement in said plane.

16. In an abrasive blast marking machine having a nozzle, means for discharging an abrasive blast through the nozzle and a head against which work to be treated by the blast may be positioned, flexible supporting means for the head carrying the head for substantially frictionless movement relatively to the nozzle generally in a plane transverse of the direction of the blast, a member set in a flexible mounting and movable therein generally pivotally about an axis substantially parallel to but ofiset from said plane, said member intersecting said plane, and connections between said member and the head permitting movement of the head in said plane but maintaining the head against substantial turning movement in said plane.

17. In an abrasive blast marking machine having a nozzle, means for discharging an abrasive blast through the nozzle and a head against which work to be treated by the blast may be positioned, flexible supporting means for the head carrying the head for substantially frictionless movement relatively to the nozzle transverse of the direction of the blast, a generally V-shaped stop member for limiting movement of the head in one direction, said member being adjustably positionable generally along the bisector of the V whereby to change the limits of movement of the head in said direction.

JOSEPH M. ESCHER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Date

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