US1735693A - Track grinder - Google Patents

Description

Nov. 12, 1929. c. w. PITMAN TRACK GRINDER l1 SheetS Sheet 1 Filed Feb. 25, 1925 5 1929- v c. w. PITMAN 1,73

TRACK GRINDER Filed Feb. 25, 1925 ll Sheets-Sheet 2 Nov; 12, 1929. c. w. PITMAN I 1,735,693

TRACK GRINDER Filed Feb. 25, 1925 ll Sheets-Sheet 3 Nov- 2, 1929- c. w. PITMAN 1,735,693

TRACK GR I NDER Filed Feb. 25, 1925 ll Sheets-Sheet 6 JWWW- N 929-- c. w. PITMANI 1,735,693

. TRACK GRINDER Filed Feb. 25, 1925 11 Sheets-Sheet 7 c. yv. PITMAN TRACK GRINDER Filed Feb. 25, 1925 ll Sheets-Sheet 9 Nov. 12, 1929. c, w, PlTMAN I 1,735,693

' TRACK GRINDER Filed Feb. 25, 1925 ll Sheets-Sheet -10 f g Z2.

1929- c. w. PITMAN ,7

TRACK GRINDER Filed Feb. 25, 1925 ll Sheets-Sheet l1 6/; www 4- Patented Nov. 12, 1929 V CHARLES W. PITMAN, OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOR TO RAILWAY TRACK WOR K COMPANY,'OF PHILADELPHIA, PENNSYLVANIA, A CORPORATION 3 PENNSYLVANIA TRACK GRINDER Application filed February 25, 1925. Serial No. 11,556.

One object of my invention is to produce a mobilejtra-ck grinding machine which is capable of continuous movement along a railwaytrack and simultaneously therewith to grind one or both of the rails composing the track.

Another object of the invention. is to provide themachine with controllingmechanism whereby-the machine may be moved backward and forward over a limited and predetermined portion of the track and simultaneous ly therewith operate to grind that portion of oneor. both of the rails underlying the machine during thismovement of the machine Another object of the invention is .to so construct the'grindingunlts thereof that, in addition to its above described capabilities,

the machine proper may be stopped at any de sired point along the track and the grinding units will operate-to grind an extremely small portion of therails.

The machine s also provided with power.

units for producing'the above described propelling and grind ng-operations. v

- The propelling mechanismof the machine includes worm gearing, by .which the machineis steadily propelled along the rails dur-. ingthe above described operations. The pitch of the worm relative to the worm wheel is such that rotation is imparted to the worm Wheel only when the worm isrotat-cd and the worm therefore cannot be rotated by theworm wheel. The traction wheels of the machine are adapted to he -rigidly connected to themachinealong the-rails, either by virtue of the traction power unit therein confined or,

upon releaseof the clutch elements on the axles, by manual'operation.

Another object of the invention is to automatically maintain a constant and predeter m1ned-pressure of the abrasive units, em-

ployed in the'grinding process, on the rails during the period oftime in which the ess ofgrinding isiin operation.

Another object of the invention is to provide the grinding machine with two separate grinding units, one overlying each rail'of the track undergoing reconditioning, either procor both ofwhich may be lowered into contact Wltll the respective'underlying rail and thereafter to be locked in such position, such lowering and locking operations of each individual unit being performed by a single operating shaft.

. Still a other bject supply a continuous flow of cooling medium to the-rail at the'point undergoing'the grind-;

ing operation, mechanism which is resillently mounted, so that the; same, may be movedaway from but which Will return auto matically t'o a. predetermined position with respect to the adjacent grinding unit.

Other advantages of the invention and the' improved constructional details thereof will.

be more fully setxforth in the following Idescription and are clearly shown in the accompanying drawings, wherein:

Figure '1. is aside elevation of my improved track grindingjmachine;

Fig. 2 is an end elevation;

ot-the invention is to is a plan view with thesuperstruc-f' ture ofthe machine removed;

Fig. i isa side elevation of onezof the grinding units drawn on an enlarged scale; "Fig. 5 1S a'plan'view ofthe structure shown in Flg. 4;

Fig. 6 is a longitudinal sectional elevation on the line 6-6, Fig. 5; j I I Fig. 7 is a longitudinal sectional elevation on the line 7f'?',-Fig'."v 5

. a Fig. 8 is atransversc sectional elevationon Y the line 8+8, Fig. l;

Fig. 9 is a transversesectional elevation on theline9+9, Fig. l; I r Fig. l0 is asectional 10-10, Fig. 9; T o I a f Fig. 11 is a, sectional elevationon the line plan'view on the line loo . Fig. 12 is an enlarged plan view of certain of the elements of the invention;

Fig. 13 is a rear elevation of the structure shown in Fig. 12 and Fig. 14 is a plan View of the machine frame and the traction elementsthereon.

Referring to Figs. 1, 2 and 8, my invention 7 consists of a main frame 1 comprising longitudinal'lyextendingchannel beams 2, 3, 4

and 5, and transversely extending channel beams 7, 8, 9 and 10, which extend from side to side of the frame 1. a A superstructure 1.5 is mounted on the frame 1 for the'purpose of protecting the mechanism of my grinding machine from the elements and for the purpose of supporting" and housing the power controlling units.

A container for a cdoling medium is also confined in the superstructure.

Secured to th'e under side of the longitudia nal beams and are journal boXes- 16, 16,

and 17, 17, respectively, in which are -rotat' ablyi mounted transversely extending ' axl es 18 and 19, to which are secured supporting andtraction wheels 20,20."

-A'tr'action motor 21 is secured to an dintermediate the longitudinal beams 3 and 4 as shown in Fig; 3 andFig. 14, and serves to drive 1 a longitudinally extending shaft "22 which is supported, adjacent. its ends, inbearings. 23 secured to transverse beams 24, 24,

extending between andsecured at their ends was longitudinal beams a and a. The OPPO- site ends of the shaft 22' are provided with worm gears 2 5, 25, which mesh with worm wheel's 26, 26,n1ounted-on the axles 18 and '19 respectively." One of the worm g'earings 2526- illustrated clearly in Figs. 1 and 3,

I 'wherein is also illustrated housing 27 which encloses sa d worm gearing and is looselymounted on the respective axle and 'ad1acent;

end of the shaft 22-. 1

Each of the worm wheels 26 is loosely mounted on its'respective axle andis provided at one of its'sides with a jaw clutch element 28 adapted to be engaged by a movable clutchelement 29 splinedfto its respective axle 18 or 19-. "Each ofthe clutch elemerits 29 is controlled by an independent hand' lever 80 pivoted to the frame ,e1-'ated in-the usual manner. I

. gT-he traction wheels 20,120, travel on rails and opww,all or portions-of which itiis desired to grind. Intermediate'each pair of longitudi nail y aligned wheels '20, 20, 1s a, grindlng unit 35. 7 Each grinding un1t35comprises a 7 main casting or housing 36'wh1ch is secured to each pair 23 or 4';5I of the longitud nalextending beams composing th'e 'framel, one of said grinding units beingclearly shown n Each of the main castings 36-is provided v with longitudinally: extending guideways 37,

37, 8), in which are slida-blymounted laterally extending- ribs 38, 38, of across-head 39', in which is adjustably mountedaseriesof faced sheave 44 around and within the grooved face of which passes a flexible cable 45.

' Each of the cables 45 is adjustablysecured toits respective lever 42 at 46 and is pro? vided, at its opposite end, with an eccentric strap 47 mounted in the face of a flanged eccentric 48;

Each of the eccentrics 48, 48, is secured to a transversely extending shaft 49. There is one eccentric 48 for each lever 42' and a pair of levers 42 for each grindingunit therefore the shaft 49 will have a pair of ee centrics 48, 48, at each of its ends. The shaft 49 is rotatably mounted in bearings 50, 50,

secured to the beams 2 and; 5 respectively,

and has a bevel gear .51 secured thereto adacent the beam 3..

wheel 51 and is secured to the projecting end of the armature shaft of amot0r 53-. The motor 53 is securely mounted on the transverse beams 24, 24, and. when energizedef f ctively reciprocates the abrasive units with respect to and in contact with the railsw, m. a 1

The abrasive units 40 arecapabl'e 'ofbeing manually placed in'contact with the rails or and thereinmaintained at a uniform pres;

sure automatically applied, or they may raised clear of the rails b-ysaid manually operated mechanisms.

It will be apparent from the above "description'that my improved gr nding machine may be effectively propelled or maybe 7 'inefiectively moved from place to place, along the rails to be operatedupon, by'the -energiz-ation of the traction motor 21 and the open ationof the clutch'levers 30,30. When'the machine has been brought to a positioni'on' the rails, above-a portion thereof toj'be especially operated upon, themotor 21 isinte'rmittently reversed, and if the clutch elements 28-29 arepermitted to remain in engagement with 7 each other, the machine will be moved baclr ward and forward, alternately, a'nd at a.

steady evenspeed due to locking te'ndeneies ofthe worm gearing- 25 2 6 andfthe tractive potency of thetract-ion wheels20, '20 on the rails above'descri bed. 7 the motor-"'21 be dis-energized, the machine propenwillvre main quiescent while the abrasive unitsam I 1 .95. A bevel pinion 52 meshes with the bevel V the carrier 55 y reciprocated with respect thereto and to, the rail m. i V f Upon operating the motor 53, the shaft 49 is rotated and therewith the eccentrics '48, 48. Each pair of eccentrics at the opposite ends of the shaft 49 is so positioned thereon with respect to each other that upon rotationof the shaft 49, the cables are alternately pulled and slackened, causing a corresponding oscillation of the levers 42 which, through" the draw bars 41,41, causes the cross lieads'39 to be recipro-cated, ca'us ing acorresponding reciprocation of the abrasive units 40 over the surface of the rail an V Eachseries of abrasive units 40 is supported ina hollow carrier 55, the interior surface of one end 56 of which lies'in a vertical plane, the opposite end 57 thereof lying at an angle with respect to the vertical plane of the opposite end.

Lying between the vertical end 56 of the carrier and the first of the abrasive units 40, and between each of the succeeding said units, is a separating plate 58. On each side of each of the said plates 58 is a. projection 59 supported in a groove 60 provided in the inside of the longitudinal walls 61, 61, of

A wedgemember 62 is provided'between the last or end abrasive unit and the inclined end wall 57 of the carrier'55 for'the purpose; of clamping all the said abrasive units'40 together and against the "verticalwall 56' of said carrier to insure rigiditybetween said units and the carrier. Y j

Each of the abrasive units 40 has secured. by sulphuring, in its upper end a threaded retaining stud 65. The'retaining studs 65 pass through elongated apertures 67 in a bar 68 which extends longitudinally of the series of abrasive units 40 and to which the said abrasive units are secured by nuts 66 on the studs 65. The bar 68 is composed of two identical sections which are secured together by bolts 69 and serves to apply equal pressure to all the abrasive units 40 simultaneously. 7 Each of the separators 58 is open at one end as indicated at 64 for the passage ofthe bar 68 as the same is fed downward, dueto the diminishing of the units 40. p I A pressure screw, 7 0 is provided by which the abrasive units40 are'a'dvanced in the carrier 55 and through which a uniform pressure ismaintainedbetween said-abrasive units and the rail being ground as the said abrasive units are worn away during such grinding.

"The "screw 70 is provided with a head '71 adapted to a socket 72 in the bar 68 which will permit rotation of said screw 70 therein but which causes a cooperative movement ver tically of the abrasive units 40 and the screw 70 when saidscrew is moved axiallyi threaded sleeve 73 slidably mountedin a he screw 70 is adapted to an internally bearing 74 secured, as will be described later,

to the carrier 55. The sleeve 73 is provided with an annular element 75 at its lower end which is threaded thereon and functions as-a upper end of the bearing 74, a flange there a of being adapted to a counter-boredportion 81 of said bearing. Ajplate 82 is securedto the bearing 74 by means of screws 82 and is adapted to surround the'sleeve 79 above the flange 80 for the purpose of retaining said sleeve against axial movement with respect to the bearing 74. The screw 70 passes through a plain bore in said sleeve 79 and is splined thereto, as shown at 83, Fig. 6.

Ratchet Wheels 84 and 85 are secured to i the sleeve 79, and intermediate said ratchet wheels is loosely mounted a pawl carrier 86. A nut isadapted to threads on the upper end of the sleeve 79 and serves to retain the ratchet wheels 84 and 85 and the pawl carrier 86 inv position on the sleeve. 79.

The pawl carrler 86, Figs. 10,11, 12' and 13, has pivoted thereto spring-pressed pawls 87 and 88 which cooperate with thesaid ratchet wheels 84 and 85 respectively. Pins 89 and 90 project from the pawls 87 V and 88 respectively and are adapted to engage cam plates 91 and 92 secured to the bearing 74. l

The pawl carrier 86 is provided with a notch 93 adapted to receive a spring-pressed plunger 94 mounted in a bracket 95 secured to the bearing 74 for the purpose of retaining the carrier 86 inacentral position wherein the said carrier 86, the sleeve7 9, and the screw 70 are held against rotation.

A projection 96 is provided on the carrier 86 and is adapted to be engaged bylugs 97, 97, projecting from a block 98 integral with areciprocablerod 99 mounted in bearings 100, 100, rigidly attached to the bearing'74.

As shown in Fig. 12, the elements are in a neutral position.- As will be apparent from said figure, a reciprocation of the rod 99 and block 98 between the neutral position and a" position adjacent the'left hand bearing 100 will cause an intermittent rotation of the screw 70 in such a direction as to cause a pressure to be exerted on the abrasiveunits 40 means of the pawl 87 on the pawl carrier 86 engaging and moving the ratchet wheel 84 and the cam plate 92 disengaging the'pawl 88from' the ratchet 85 to permit: said movement of the ratchet wheel 84. A reciprocation of the rod 99 between the neutral position and a position adjacent the right hand bear? 5 7 ing 100 will cause a rotation of the screw 7 O plunger 94: is forced out of the notch 93in said 7 in anopposite direction and relieve the pressure onthe abrasive units 40, the pawl 88 such time engaging and movingthe ratchet wheel 85 and the cam plate 91 disengaging mot suchmoveinent of the ratchet wheel 85;

To accomplish thecabove mentioned recip-g rocation of the rod 99,,"the block 98 is provided with a depending lug 101, adapted to be engaged by arms 102 and 103 of tripping heads 104 and 105 respectively, Figs, and 11;

The tripping heads'lO l and 105 are slidably mounted in guideways 106 and 10.7. Intermediate, the said guideways 106 and 107 is rotatably mounteda cam 108, against the opposite sides of which the tripping heads 10 i and 105 are maintained springs 109 and 110. The cam 108 is mounted on the inner end of a shaft 111 which projects outwardly through the channel beam '5 and has mounted on'its projecting end a hand lever 112.

WVhen in the neutral position, as shown in Fi '10, and considering the crosshead 39 as 'receivinga reciprocating motion, the trip heads 10 1 and 105 are engaging opposite sides of the earn 108 at the high portion of the pc- .riphery thereof'whereby the arms f 102: and -103 -are held in such positionsthattheymerely engage the lug 101 attheextreme limit of its outward movement,during the-aforesaid I I in Flgsy, 7 and 8.

reciprocationof the crosshead 39'. H v

JNhenit is desired to increase the-pressure ontheflabrasive units 40, theshai't 111 is ro-j tated tobring the low portion of the earn 108 in alignmentwith the trip head 105, which causes the arm 103to move inwardly 'sothat it will be engaged by the lug 101 immediately preceding the limit: of its, movement in one direction during said reciprocation.

Engagement'of the, lug 101 with. the arm 103 causes the rod 99 and the block 985cc be moved longitudinally, causing a slight, rota tion of the pawl carrier 86 in the threction of V the arrow anFig; 10. Such rotation of" the.

carrier 86 causes the pawl- 87 to move the ratchet wheel 84 and consequently the sleeve 7 9 ma hkedirection. The pin 90'on'the pawl I 88 engages the can; 92"and withdraws the pawl 88 from the ratchet wheel 85'; The

7 carrier, by the canrlike side ofthe notch 79 causes/a hke rotation of the screw;70,

93 being pressed against the angular or con-V ical shaped engaging face of the'plungert i.

The above mentioned rotation of the sleeve w i ch" produces an upward axial movement of the sleeve 73, thereby increasingjthe com pressionof the springfi which in turn produces anincreased downward pressure on the screw 70 pressure barj68, and the abrasive units 40.

Asthe lcross head 39 approaches the l'imitof it's'inovenie'nt in the d rection opposite to that just. described the arm 102 en a es the hi I Z i .7 z" D a the pawl 87 from the ratchet wheel 8% toperr 101 and returns the elements to their neutral positions, as shown in said Figure 10.

If the pressure on the abrasive units is equal to the predetermined operating pres-h sure as, determined by the tension "otthe spring 110, said spring will yield when the. lug 101 engages the arm 103v "and no rotation of the screw owill be registered. Q.

1 shouldit be desirable to; reduce the pressure on theabrasive units 40, the1ever 112 will be moved in the opposite direction to that just described with a corresponding re verse operation of the above described ele-; ments and a consequent reduction; ofthe pressure aforesaid.

As shown Fig.6, pressure on the end wedge 620i the grinding unit35 is controlled by mechanism identical, with that just de'.

scribed in connection with the abrasive units 40, and maybe externallyoperated by a, H

" Q d te Q-ure the... vertical movement relat ve to the crosshead '89 duringv the grinding process, said carrier is provided with toggle-operatedflocks, one

on either s'id ejtheifeolgtl The end walls and 121 of thehollow interior; portion of thec 0$ d 3. are n ed nw ardly'frqm the bottom and upwardly therefrom. Int egral with each of the sidewallsfil, 61, ofthe carrier 55 is projecting abutment 122, Fig, 7, which normally lies in cont-actwitlrthe inside of. the wall-120 of the crosshead 39.

Slidably'mounted in guideways 123 and 124:

are blocks 125 and 126 respectively. 'Toggle' links 127 and 128 are connecte'd to there spective blocks atonejen'd thereof, theljope posite ends of said toggle being. pivotally secured'togetherand to vertically s1id able racksl29 adapted to guideways 130m; tegral with uprights131 which $11PPOit and rigidly connect the bearing; T4 with the carrier '55. A movable abutment is slid:

, ably mounted inguideways 133 integral the sidewall 61 ofthefcarrierY'55, one end of said movable abutment'nornially 'engag carrier- 55 against ing the inside Qfthe wall 121, opposite end, of, said abutment engaging; a tapered block 1341' verticallyfadjustable, by means of abolt 135', (Fig. 7); between the adjacent ends of theblock'126fand' abutment 132' r spectively. As shown in Fig. 7 'the' elements are shown in, alocked position against vertithe crossliead 39.

cal movement otthfe caution- 155,relative.to

.In order to raise the carrier 55 and its associated abrasive units 40 clear of the rail upright brackets 141, 141, integral with the side walls of the. crossliead 39. The shaft 138 has asquared end 142 for the accommodation of a socket wrench or head of a crank (not shown) by which the carrier 55 may b between the upper ends of the racks 129, 129,

raised.

The oper'ation'of unlocking and raising the carrier 55 and its associated abrasive units 40 will be apparent upon reference to Fig. 7. By application of a crank or wrench to the squared end 142 ofthe shaft 138 and a subsequent turning of said shaft, the pin-i ions 137 will raise theracks 129. The first effect of such raising ofthe racks 129 willbe to collapse the toggles 127128, thereby moving the blocks 125 and 126 toward each other and releasing the' abutments 122 and 1132, from rigid contact' with the end walls 120 and 121 of thecrosshead 39, The next step in the operation will be the engagement and the lower sides of the lugs 136,; 136.

Upon a continued rotation of the shaft 139, the carrier 55 and its associated elements will be raised to any desired extent.

The carrier 55 may be retained in its elevated position by providing a ratchet wheel 144 on the end of, the shaft 138 and a pawl 145 pivoted to one of the integral brackets '141 for cooperative engagement with said ratchet wheel 144. V p Reversal of the direction of rotationot the shaft 138 will lower the carrier 55 and its associated elements until the projecting under side of the guideways 133 and abuthead 39, a A coolingmedium may be supplied to the i adjacent the said abrasive rail being operated upon. The pipe 150 isment 122 engage lugs 143 projectinginwardly from the side walls of the crosshead 39.

Continued rotation of said shaft in this direction will operate the toggle links 127 128,.

thereby moving the blocks 125 and 126 out-- wardly against the abutment 122 and adj usting block 134 and the abutment 132 whereby the said abutments122 and 132 are forced into rigid engagement with the inside of the inclined end abrasive units 40-during. the grinding operationby a pipe 150 which normally lies so mounted at the ends of levers 151 pivoted at 152 to the casting 36 that the said pipe addition of a prime mark to those of the 1 controlled.

wallsl20 and 121 of the crossunits 40 and the 150 may readily be moved toward or away from said abrasive units' The levers 150 have projecting arms 153 towhich are pivoted rods 154, the upper ends of which are hook shaped and adaptedto bc'positioned in forkedbrackets 155 secured'to the frame of the grinding machine. By the above described, arrangement of elements, each fpipe 150 is held at a predetermined distance rom the rail andthe abrasiveunits by the hook end of the rod 154 engaging theb'ase of the slot'in the forked bracket 155, but may be manually swung away from the said position and will automatically return to said predetermined position by gravity. when released, the arms 151 turning on theirpivots' 152. The cooling mediumsupplied by the pipe 150 is delivered thereto from atank 156v mounted onthe superstructure of the grinding machine and conveyed togs'a1dT p pe through a flexible hose pipe connection 157 uiiderrcontrol of a valve v158. v T he mechanism for co'iitrollingthe degree of pressure on the wedge member; 62 being identical with that employedfor controlling the pressure on the abrasive, units 40, separate description thereof is deemed unneces v sary, andthe similar elementsiwill be identified by similar referencecharacters with the wedgecontrol.

In Fig. 1, I havediagrammaticallyjillustrated and designated by the reference character 160 a controlling unit for the traction motor 21 whereby the speed 'and' direction of travel of the machine nay be definitely" I claim: 1. In a mobile and'a reciprocating element;jabrasive.units adyustably mounted in said reciprocating element; means, carried by said IQClPFOCEtl' abrasive units, and means mounted onsaid fixed element for operating said raisingand' lowering means byrecipr'ocation of-said reciprocating element, whereby the degree of pressure between the abrasive units and the rails is controlled; y A

2. In a mobile track grinding machine, a

grinding unit comprising a relativelyfixedx.

housing; avci'osshead reciprocally mounted track grinding [machine a grinding unit comprising ai fixed elementing element, for raising and lowering the said in said housing; a carrieradjustablymounted I in said crossliead'; abrasive units adjustably mounted n said carrier; means on said car rier for raising and loweringsaid abrasive units with respect to said carrier; .meanS mounted on said'fixed housings for operating said raising and lowering means, when said crosshead is-reciprocated.

. 3-. In aniobile'track grinding machine, a

grinding unit comprising a reciprocably mounted crosshead; an abrasive'unit carrier suitab y m unt In a Q Oss ea means position with respect to said pressure maintaining means. i

10. A mobile grinding machine, comprising a frame; crossheads reciprocally mounted .in said vframe; abrasive units; carriers for said abrasive units mounted in said cross heads; pressure bars attached to said abrasive units; upright bearings on said carriers; flanged and internally threaded sleeves slidably mounted in and axially aligned with said bearings; pressure screws adapted'to said internally threaded sleeves and operatively connected to said pressure bars; springs confined between the lower ends of said upright bearings and the upper side of said flanges adapted to move said sleeves downwardly in said bearings,- and means on said carrier for rotating said pressure screws with re spect to said sleeves, whereby pressure may be applied to said abrasive units by said springs, and means on said frame adapted to engage and operate said screw rotating means during the reciprocation of said crossheads. I

11. A mobile grinding machine, comprising a frame; crossheads reciprocally-mounted in said frame; abrasive units; carriers for said abrasive units; hearings on said carriers; pressure screws suitably mounted in said bearings for'applying pressure to said abrasive units; sleeves suitably mounted in the upper ends of said bearings and surrounding and being splined to said pressure screws;

ratchet wheels secured to said sleeves; pawl carriers loosely mounted on said sleeves intermediate said ratchet wheels; resilient pawls pivoted to said pawl carriers and operatively engaging said ratchet wheels in opposed relationship to each other; cams secured to said bearings for releasing either of said pawls, means for oscillating said pawl carriers to turn said pressure screws; and

means on said frame for resiliently operating said oscillating means upon reciprocation of said crossheads to maintain a predetermined degree of pressure of said abrasive units against said rails.

12. A mobile grinding machine comprising a frame; reciprocating members mounted on said frame; abrasive units adjustably mounted in said reciprocating members; compression springs for applying pressure on said abrasive units; pressure screws for controlling the degree of compression of said. springs; oscillating means for controlling the rotation of said screws mounted on said reciprocating members; a projection on said oscillating means; slide rods on said reciprocating members; blocks integral with said rods; lugs on said blocks engaging said projections on said oscillating means; depending projections on said blocks; and resilient arms mounted on said grinding machine frame for engaging said depending projections on said blocks upon actuation of said 7 reciprocating members for the purpose of maintaming a predetermined degree of pres sure of said abrasive units upon the surface of the objects being ground.

13, A mobile grinding machine comprising a frame; reciprocating members on said frame; abrasive vunits adjustably mounted in said reciprocating members; pressure.

screws for controlling the degree of pressure applied tosaid abrasive units; oscillating means for rotating said screws; sliding rods for operating said oscillating means;-

said shafts for controlling the position of said 7 cams; andmeans for reciprocating said depending projections into engagement with said projecting arms alternately.

CHARLES W. PITMAN.

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