US2187072A

US2187072A - Trail builder, bulldozer, and the like

Info

Publication number: US2187072A
Application number: US72960A
Authority: US
Inventors: Bleu Charles Le
Original assignee: Individual
Current assignee: Individual
Priority date: 1936-04-06
Filing date: 1936-04-06
Publication date: 1940-01-16
Anticipated expiration: 1957-01-16

Description

Jan. 15, 1940.

c. LE BLEU TRAIL BUILDER, BULLDOZER, AND THE LIKE Original Filed April 6, 19556 2 Sheets-Sheet 1 FIG.

FIG 2 IN VEN TOR.

Jan. 16; 1940. c. LE BLEU TRAIL BUILDER, BULLDOZER, AND THE LIKE Ofiginal Filed April 5, 1936 2 Sheets-Sheet 2 Patented Jan'. l6,

UNITED STATES" PATENT OFFlCE mm. BUILDER, nunmozsa. AND rim Charles Le Bleu, Los Angeles, cam. Application April 6, 1936, Serial No. 72,980

Renewed May 5,

22 Claims.

This invention relates to earth moving devices, the term earth being taken in the broad sense to include snow, ice, and the like, adapted to be connected to a tractor to be moved across a surface to be treated and includes a digging and scraping implement disposed in operation frame carrying at its forward end a material handling implement which, in the case of the bulldozer, is a rigid part of the pusher frame, but.

in the trail builder is pivoted to the forward end of the pusher frame, and transverse tilting of the material handling implement is accomplished by collectively tilting the pusher frame, or by tilting the material handling implement on the pusher frame. This conventional type of construction entails certain costs that it is the object of this invention to minimize.

Another object of this invention is the provision, in a device of the class named, of an articulately assembled pusher frame and scraper assembly and a suitably designed control means therefor adapted to articulate the assembly to raise, lower and transversely tilt the material handling implement and to positively retain the assembly in its articulately adjusted positions.

Still another object is the provision in a device of the class described of a pusher frame, a scraper mounted on the forward end of the pusher frame for rearward rocking movement and yieldable means disposed between the pusher frame and the scraper to resist the rearward rocking movement of the scraper.

Still other objects, features and advantages of this invention will be apparent to those skilled in the art upon detailed perusal of the attached drawings and the following specifications, wherein I describe and exemplify my'invention, but it is to be understood that my invention as herein exemplified and described is susceptible to many changes in the combination, correlation and construction of parts, members, and features without departing from the spirit of the invention as defined in the annexed'claims.

in the drawings:

Figure 1 is a plan view of my invention as embodied in a bulldozer attached to 'a tractorof conventional design.

Figure 2 is a side elevation of Figure 1.

- Figure 3 is a side elevation of my invention as embodied in a trail builder, grader, and, the like.

Figure 4 is a plan view of Figure 3.

Figure 5 is a longitudinal sectional view of the hydraulic motors for' raising, lowering, and articulately adjusting the device associated with a diagrammatic illustration of a control mechanism for said motors. v

Figure 6 is a transverse sectional view of one of the hydraulic motors (these motors are identical) taken on a line 6-6 of Figure 5.

In the drawings similar characters of reference designate corresponding parts in the several views.

Referring'now to the drawings, Figures 1, 2, I

and 3, T is a tractor of conventional design including a body 9 and a pair of track laying units, In, Ill disposed oneat each side of the body and pivotally connected theretoat II, H for vertical swinging movement. A pair of brackets l2, l2 are secured one to each of the track frames and provided with a ball l3, I3. A pair of pusher arms l4, M are disposed one at each side of the tractor and provided at their rear ends with ball sockets l5, l5 by means 'of which they are articulately mounted on balls l8, 13' carried by the track frames.

Pusher arms l4, it are provided behind their front ends with round faced rings l6, l6"-adapted to receive a ball socket. A cross beam i1 is disposed transversely in front'of the tractor, see Figure 1, and provided at each of its opposite ends with a ball socket I8, l8 articulately mounted on round faced rings l8, it carried by pusher arms I4, H are provided at their front ends with balls l9, l9 articulately mounted in ball sockets 20, 20' carried by a scraper 2|. 1

Arm 22 is articulately connected at its lower end to cross'beam I! at 23, and at its upper end to the back of scraper 2| at 24. Arm 22 retains the scraper in the upright position shown. Brackets l2, l2 carry trunnions 25, 25'.

Spaced forwardly from trunnions 25, 25' are other trunnions 26, 26' also mounted one on each of the track frames.

Pivotally mounted on each of the trunnions 26, 26' is a vertical link 21 and 21'.

A pair of fabricated brackets 28, 28' are disposed one on each of the track frames and pivot-- ally mounted at their rear ends on trunnions' 25, 25 and behind their front ends on the upper ends of vertical links 27, 27'.

Mounted on each of theffabricatedbrackets by means of lugs and pins, as at 29, is an oscillating

motor

80 and 3|.

Motors 30 and Si are identical in construction and each .comprises (refer to Figures 5 and 6) a cylinder 32 having fixed partitions 33 and 34 diametrically opposite to one another and of sectoral form with a common center concentric with the bore of cylinder 32. Concentrically dis.- posed within the cylinder 32 is a shaft 35 having vanes 35 and 35V sweep the spaces between fixed partitions 33 and 34. Cylinders 32 are provided each with a pair of

ducts

36, 31 and 38, 39. Duct 38 registers with parts 40 and ii communicating with the bore. Duct 31 registers with

parts

42 and 43 communicating with the bore. Duct 38 registers with

parts

44 and 45, communicating with the bore. Duct 39 registers with parts 48 and 41 communicating with the bore.

The motor just described is an oscillating motor. When fluid under pressure is admitted to duct 36 and duct 31 is connected to exhaust, the impeller 35, 35V will be rocked clockwise, by arresting the flow of fluid the impeller may be fluid locked in its arrested position. By reversing the flow of fluid the impeller may be turned in the opposite direction. The other motor being identical in, construction operates in a similar manner. When fluid under pressure is admitted to duct 38 and duct 39 is connected to exhaust, the impeller 35, V will be rocked clockwise, and by arresting the flow of fluid the impeller may be fluid locked in its arrested position, and by reversing the flow of fluid the impeller may be turned in the opposite direction. Obviously then, fluid under pressure may be directed to the m0= tors to cause simultaneous operation thereof in the same or in opposite directions and the motors may be operated singly in either direction. I provide means for directing the flow of fluid to and from the motors 30 and Si as'follows: I provide a control valve 48 comprising a housing 48 having a pair of bores and a conduit 50 connected to duct 39, a conduit 54 connected to duct 38. a conduit 5! connected to duct 38, a conduit 53 connected to duct 31, a conduit I2 connected to a fluid reserve tank 58 and a conduit I connected to a source of fluid under pressure P. Tumably'mounted in each of the said pair of bores are valve plugs 51v and I8.

Valve plugs

51 and 58 being in the positions shown, the motors are fluid locked against rotation in either direction and the continuously running pump P receives fluid via conduit I9 from the reserve tank II and discharges the fluid into conduit II from which it flows through the control valve into a conduit 52 and thence into reserve tank It. To operate motor 30 in a counterclockwise direction, valve plug I1 is rotated in a counterclockwise direction to register through part ill with conduit and register side part 8| with connecting duct 62 and conduit 54. Thus fluid under pressure will enter the bore of motor 30 through parts 48 and 41 thus causing counterclockwise rotation of impeller 35, 85V and the fluid displaced thereby through

parts

44 and 45 will return to the valve 48 via conduit I4 thence via side part 6i and connecting duct 42 to the through part 83 of valve plug 58. Now if valve plug II remains in the position shown, the fluid will flow thence to the reserve tank ll, but valve plug ll may. be operated in the manner of valve plug I1 and the fluid displaced from the motor a may thus be utilized to operate motor II. Thus it is clear that motors 30 and Il may be operated simultaneously in the same or in opposite directions and may be operated singly. When the motors are operated simultaneously fluid displaced by the operation of motor 30 will be utilized' to operate motor- 3|, and when only one motor is operated the fluid will be received directly from the pump P via the control valve 44. It is believed that further explanation of.

the operation of control valve 48 and motors 84 and Ii is unnecessary since it is clear from a study of Figure 5 that the valve plugs" and II may be operated in the manner already described to register the through parts with the various conduits connected to the motors to accomplish the desired operation thereof. An advantage of the hydraulic hook-up Just described resides in the fact that the fluid displaced by the operation of one of said motors may be utilized to operate the other of said motors with the results that both motors may be oscillated simultaneously and equally regardless of the fact that said motors may be unequally loaded.

' Each of motor shafts ii are provided, one with arms 84 and the other with arms 84', carrying between their outer ends ball and

socket connections

65 and 65'. 68 is a suspension link secured at its upper end to ball socket connection II and secured at its lower end to a ball and socket connection 61 carried by cross beam I1 adjacent one of its ends, and this structure is duplicated at the other side of the tractor, ball socket connection 65' being provided with a suspension link 86' secured at its lower end to a ball and socket connection 61 carried by cross beam l1 adjacent its other end. Thus it is seen that motor 30 is operably connected to cross beam i1 adiacent one of its ends, and motor Ii is operably connected to cross beam l1 adjacent the other of its ends, and since, as heretofore explained, side beams I4, I 4 and cross beam i1 and scraper 21 are articulately assembled and side beams l4, H are articulately connected to the tractor, it follows that side beams i4, i4 may be swung singly and may be swung simultaneously in the same or opposite directions. Motors I0 and Ii, as explained. are disposed and adapted to be operated singly, or simultaneously in the same 'or opposite directions, and'since these motors are operably connected to cross beam i1, one adjacent each end thereof, it follows that the motors may be operated singly, or simultaneously in opposite directions for transversely tilting the scraper 2|, and may be operated simultaneously in the same direction for raising and lowering scraper 2i.

Referring now to Figures 8 and 4 wherein I exemplify my invention in a modified form whereby the scraper may be disposed either in the transverse position or in an oblique position indicated in Figure 4 by broken lines, a pair of brackets 44, II are secured one to each of the track framm and provided with a ball 44, II. A pair of telescoping pusher arms 1|, 14' are disposed one at each side of the tractor and provided at their rear ends with ball sockets 1|, 1| by means of which they are articulately mounted on balls 44, ll carried by the track frames. Telescoping pusher arms 14, 14' each comprises a fixed

section

12 and 13 and a

telescoping section

12, 18 slidably disposed in the fixed section. The fixed

sections

12 and 13 are provided adjacent their front ends with round faced' rings 14, 14' adapted to receive a ball socket. A telescoping cross beam 84 is disposed transversely in front of the tractor, see Figure 3, and provided at each of its opposite ends with a ball socket 1|, 1| articulately mounted on round faced'rings 14, 14' carried by the fixed

sections

12, 13 of the telescoping pusher arms 1|, 1|. Telescoping sections 1!, 13', of the pusher arms 14, 14' are provided at their forward ends with balls 14, .18 articulately mounted in ball sockets 11, 11' carried by scraper 18. Jour- 'naled on scraper 1| at 14 and II are sheaves It and II. Secured adJacent the front ends of telescoping section 11', 18' of pusher arms 1|, 1! are brackets 83 and I4. Secured to scraper 1| are brackets II and II. Adlustably secured to bracket 88 atllisacablellextendingup- "front ends of the pusher arms, and power opwardly therethrough, thence through an opening in bracket 85, thence about sheave 8|, thence about sheave 82 and downwardly through an opening in bracket 86, thence on downwardly and secured to bracket 84. Disposed between bracket the pusher arms are swung in opposite directions for transversely tilting the scraper, and when the track laying units swing independently in a vertical plane. Still another advantage of this arrangement is as follows: The force exerted on scraper 18 by the compression springs 88 and-88' maybe such that, when a predetermined force is'applied by accumulated materials to the scraper above the ball joint connection of the pusher arms.

with the scraper, the scraper 18 may rock backwardly thus compressingthe springs and partially or wholly prevent the further accumulation of material, thus minimizing the necessity for almost constant operation of the motors 88,

3| to control the accumulation of material. The operation of these motors together'with associated control mechanism has already been described in connection with Figures'l, 2, and 3, and therefore will not be repeated in connection with the description of Figures 3 and e.

Still referring to Figures 3 and d, it will be noted that the fixed sections 12 and '13 of

telescoping pusher arms

18, 10 are provided with openings 9| and ill, and the telescoping sections 12' and I3 are provided each with a plurality of

openings

92 and 82'. v A pair of pins 98 and 93 are also provided. Thus the efiective length of pusher arms 18 and 18' may be adjusted as desired and secured in the adjusted position by the pins 93 and 93', and by adjusting one of said pusher arms the scraper 18 may be disposed in the oblique position indicated in Figure 4 by broken I lines.

Having thus described my invention, what I claim as new and useful and desire to secure by Letters Patent is: a

' 1. A material handling machine comprising a tractor, a pair of pusher arms disposed one 811; each of the opposite sides of the tractor, means articulatelymounting the rear end of the pusher arms on the tractor, for independent vertically swinging movement about a common axis a rigidly constructed scraping unit disposed forwardly of the tractor, means articulately mounting the scraping unit on the front ends of thepusher arms whereby the pusher arms may swing in-' dependently. in opposite directions in a vertical plane about the common axis for transversely tilting the scraping unitwithout imparting torsional strain thereto, and power operated means to swing the pusher arms for tilting the scraper unit, and other means for retaining said scraper unit in its upright position on said pusher arms.

2. A material handling machine comprising a tractor, a pair of pusher arms disposed one ati each of the opposite sides of the tractor, means articulately"ni6unting therear ends of the pusher arms on the tractor, a rigidly constructed scraping unit disposed'forwardly of the tractor, means a t culately mount s the scrap nk lmit. on the ing unit disposed forwardly of the tractor, means articulately mounting the scraping unit on the front ends of the pusher arms, and power op- .erated means for swinging the pusher arms to transversely tilt the scraping unit, and other means for retaining said scraper unit in its HI).

right position on said pusher arms.

4. A material handling machine comprising a tractor, a pair of pusher arms disposed one at each of the opposite sides of the tractor, means articulately mounting the rear ends of the pusher arms on the tractor for independent vertical swinging movement, a rigidly constructed scraping unit disposed forwardly of the tractor, means articulately mounting the scraping unit on the front ends of the pusher arms, other means connected tothe pusher arms and the scraping unit to'retain-the scraping unit in theupright position on the pusher arms and automatically shiftable to permit the pusher arms tb be swung in opposite directions for transversely tilting the .scraping unit, and means for so swinging the pusher arms.

5. A material handling machine comprising a tractor, a pair of pusher arms disposed one at each of the opposite sides of the tractor, means articulately mounting the rear ends of the pusher arms on the tractor, a scraping unit disposed forwardly of the tractor, means articulately mounting the scraping element on the front ends of the pusher arms, other means connected to the pusher arms and the scraping unit and shiftable automatically on 'the latter to permit the pusher arms to be swung in opposite directions in a vertical plane for transversely tilting the scraping unit, and means to so swing the pusher.

arms.

6. A material handling machine comprising a tractor, a pair of pusher arms disposed one at each of the opposite sides of the tractor, means articulately mounting the rear ends of the pusher arms on the tractor, a cross beam disposed forwardly of the tractor, means articulately con- .shiftable'to permit the pusher arms to swing in opposite directions in a vertical plane for transversely tilting the scraping unit, and power operated means mounted on the tractor and connected to the cross beam for so swinging the pusher arms in opposite directions to transversely tilt the scraping unit.

'7. A material handling machine comprising a tractor, a pair ofpusher arms disposed one at each of the opposite sides of the tractor, means articulately mounting the rear ends of the pusher arms on the tractor. a cross beam disposed ftawardly of the tractor, means articulately conn ting the ends of the cross beam each to a 4 pusher arm, a scraping unit disposed forwardly of the tractor, means articulately mounting the scraping unit on the front ends of the pusher arms, means connected to the cross beam and the scraping unit to retain the scraping unit in its upright position on the pusher arms and permit the pusher arms to swing in opposite directions in a vertical plane, and control means mounted on the tractor and connected to the cross beam for swinging the pusher arms in opposite directions to transversely tilt the scrap- -ing unit. 1

8. A material handling machine comprising a tractor including a body and a pair of track laying units disposed one at each of the opposite sides thereof and journaled behind their front ends to the body for independent vertical swinging movement, a pair of pusher arms disposed one at each of the opposite sides of the tractor, means articulately mounting the rear ends of the pusher arms on the track laying units for independent vertical swinging movement, a rigidly constructed scraping unit disposed forwardly of the tractor, means articulately mounting the scraping unit on the front ends of the pusher arms, and power operated means for swinging the pusher arms longitudinally for raising, lowering and transversely tilting the scraping unit, and other means for retaining said scraper unit in its upright position on said pusher arms.

9. A material handling machine comprising a tractor including a body and a pair of track laying units disposed one at each of the opposite sides thereof and journaled behind their front ends to the body for independent vertical swinging movement, a pair of pusher arms disposed one at each of the opposite sides of the tractor, means articulately mounting the rear ends of the pusher arms on the track laying units for independent vertical swinging movement, a scraping unit disposed forwardly of the tractor, means articulately mounting the scrap ing unit on the front ends of the pusher arms, power operated means connected to the pusher arms and the scraping unit to retain the scraping unit in its upright position on the pusher arms and permit simultaneous swinging movement of the pusher arms in opposite directions in a vertical plane without affecting the upright position of the scraping unit, and means to control the operative and inoperative positions of the machine.

10. A material handling machine comprising a tractor including a body and a pair of track laying units disposed one at each of the opposite sides thereof and journaled behind their front ends on the body for independent vertical swinging movement, a pair of pusher arms disposed one at each of the opposite sides of the tractor, means articulately mounting the rear ends of the pusher arms on the track laying units, a scraping unit disposed forwardly of the tractor, means articulately mounting the scraping unit on the front ends of the pusher arms, other means connected to the pusher arms and the scraping unit to retain the latter in its upright position on the pusher arms and permit simultaneous swinging movement of the pusher arms in opposite directions in a vertical plane without affecting the upright position of the scraping unit, a cross beam disposed forwardly of the tractor behind the scraper, means articulately connecting the ends of the cross beam each to a pusher arm, and power operated means mounted on the track laying units and connected to the cross beam for raising, lowering and transversely tilting the scraping unit.

11. A material handling machine comprising a tractor including a body and a pair of track laying units disposed one at each of the opposite sides thereof and journaled behind their front ends on the body for independent vertical swinging movement, a pair of pusher arms disposed one at each of the opposite sides of the tractor, means articulately mounting the rear ends of the pusher arms on the track laying units, a scraping unit disposed forwardly of the tractor, means articulately mounting the scraping unit on thefront ends of the pusher arms, a cross beam disposed forwardly of the tractor behind the scraping unit, means articulately connecting the ends of the cross beam each to a pusher arm, means articulately connected to the cross beam and the scraping unit to retain the latter in its upright position on the pusher arms and per mit simultaneous swinging movement of the pusher arms in opposite directions in a vertical plane without affecting the upright position of the scraping unit, and power operated means mounted on the track laying units and connected to the cross beam and operable to raise, lower and transversely tilt the scraping unit.

12. The combination in a device of the class described, a pair of substantially spaced apart telescoping pusher arms adapted at their rear ends for pivotal connection to a tractor, a scraping unit disposed at the front ends of the pusher arms, means articulately mounting the scraping unit on the front ends of the pusher arms, other means connected to the'pusher arms and the scraping unit to retain the scraping unit in its upright position on the pusher arms and permit simultaneous articulation of the pusher arms in opposite directions in a vertical plane without affecting the upright position of the scraping unit.

13. The combination in a device of the class described, a pusher frame comprising a pair of spaced apart telescoping pusher arms adapted at their rear ends for articulate connection to a tractor and adapted at their front ends for articulately supporting a scraper and a telescoping cross beam articulately connected at its opposite ends each to a pusher arm behind the front end.

14. The combination in a device of the class described, a pusher frame including a pair of spaced apart telescoping pusher arms each comprising a fixed section adapted at their rear ends for articulate connection to a tractor and a telescoping section adapted at their front ends for articulately supporting a scraper and a telescoping cross beam articulately connected at its opposite ends each to thefront end of a fixed section;

15; The combination in a device of the class described, a pusher frame,- a pair of spaced apart pusher arms each adapted at its rear end for pivotal connection to a tractor for independent swinging movement about a common axis, a scraping unit mounted on the front end of the pusher frame for back and forth rocking movement thereon, whereby the scraping unit tends to rock forwardlywhen disposed in scraping contact with the ground and subsequently to rock rearwardly when a predetermined load has accumulated, means connected to the pusher frame and the scraping unit to limit forward rocking movement, and means disposed between the pusher frame and the scraping unit to initially N independent vertical swinging movement, a pair of pusher arms disposed one on each side of the tractor, means articulately mounting the rear ends of thepusher arms on the track laying units, a scraping unit articulately disposed at the front ends of the pusher arms, means in combination with the pusher arms and the scraping unit to maintain the scraping unit in an upright position while allowing simultaneously. swinging movement of the pusher arms in opposite directions in a vertical plane without affecting the perpendicular position of the scraping unit and power means articulately connected with the pusher arms whereby the pusher arms may be swung independently in a vertical plane about a common axis forraising, lowering and trans versely tilting the scraping unit.

17. A material handling machine comprising a tractor including a body and a pair of track laying units disposed one at each of the opposite sides thereof and journaled behind their front ends of the body for independent vertical swinging movement, a pair of pusher arms disposed one at each of the opposite sides of the tractor, a scraping unit disposed at the front ends of the pusher arms, said pusher arms being articulate- 1y mounted at their rear ends to the tractor for independentvertical swinging movement, a cross beam disposed forwardly of the tractor behind the scraper, means articulately connecting the ends of the cross beam each to apusher arm and power operated means of the track laying units and connected to the cross beam for raising,

' lowering and transversely tilting the scraping unit without imparting torsional strain thereto and means articulately mounting the scraping unit on the front ends of the pusher arms whereby the pusher arms may swing independently in a vertical plane about the common axis and power operatedmeans to swing the pusher arms for transverse tilting of the scraping unit.-

18. A material handling machine comprising-a tractor, pusher arms disposed one at each of the opposite sides of the tractor, means-articu- J lately mounting the rear ends of the pusher arms onthe tractor, across beam disposed forwardly of'the tractor, means articulately connecting the ends of the cross beam each to a pusher arm, a scraper unit disposed forwardly of the tractor, means articulately mounting the scraping unit on the front ends of the pusher arms, means articulately connected to the pusher arms and the scraping unit to retain the scraping unit in its upright position on the pusher arms, and power operated means mounted onthe tractor and connected to the cross beam for raising and lowering the front end of the pusher arms and the scraping unit. 19. A material handling machine comprising tractor, a pair of pusher arms disposed one at each of the opposite sides of the tractor, means articulately mounting the rear ends of the pusher arms on the tractor, a cross beam disposed forwardly of the tractor, means articulately connecting the ends of the cross beam each to'a pusher arm, 'a scraping unit disposed forwardly of the tractor, means articulately mounting the scraping unit on the front ends of the pusher arms, means articulately connected, to the cross beam and the scraping unit to retain the scraping unit, in its upright position on the pusher arms, and power operated means mounted on the tractor and connected to the cross beam for raising and lowering the front ends of the pusher arms and the scraping unit.

20. The combination in a device of the class described, a pusher frame adapted at its rear end for pivotal connection to a tractor, a scrap,- ing unit articulately mounted on the' front end of 'the pusher frame for back and forth rocking movement thereon, whereby the scraping unit tends to rock forwardly when. disposed in scraping contact with the ground, subsequently rocking rearwardly when a predetermined load has accumulated, means connected to the pusher frame and the scraping unit to limit forward rocking movement, and power operated means mounted on the tractor and connected to the pusher frame for raising and lowering the front end of the pusher frame and the scraping element.

21. A material handling implement comprising a tractor including a body and track laying units disposed one at each of the opposite'sides thereof and supporting the body from the ground, pusher arms disposed one at each of the opposite sides of the tractor and articulately mounted at their rear ends on the tractor, a cross beam disposed forwardly of the tractor, means articulately connecting the ends of the cross beam each to a pusher arm, a scraping unit disposed forwardly of the tractor, means articulately mounting the scraping unit on the front ends of the pusher arms, means connected to the pusher arms and the scraping unit to retain the scraping unit in its upright position on the pusher arms, a cantilever bracket disposed'with each of the track laying units, means pivotally mounting the rear ends of the brackets on the track laying units, supporting links pivotally mounted on the track laying units adjacent the forward ends thereof, means pivotally supporting the for ward end of said brackets on the upper end of said supporting links, and power operated means connecting the brackets and the cross beam for raising and lowering the front end of the pusher arms and the scraping unit.

22. A material handling machine comprising a tractor, a pair of track laying units connected therewith, a pair of pusher arms one disposed at each of the opposite sides of the tractor, means articulately mounting the rear ends of the pusher arms on said track laying units, a rigidly con? structed scraping unit disposed forwardly of the tractor, means articulately mounting the scraping unit on the front ends of the pusher arms and 'power operated means for swinging the pusher arms in opposite directions in a vertical plane to transversely tilt the scraping unit, and other means for retaining said scraper unit in its upright position on said pusher arms.

enamel-ammo.-