US3711971A

US3711971A - Large capacity scraper unit construction

Info

Publication number: US3711971A
Application number: US00194897A
Authority: US
Inventors: W Martin
Original assignee: W Martin
Current assignee: WE MARTIN Co
Priority date: 1971-11-02
Filing date: 1971-11-02
Publication date: 1973-01-23
Anticipated expiration: 1990-01-23
Also published as: BR7204681D0; DE2230166A1; SU613728A3; JPS4853503A; CA973129A; AR193424A1; GB1380332A; IT955333B; DE2230166C2; JPS5211125B2

Abstract

The largest capacity earth moving scrapers may be loaded to their rated capacity using a single powered traction unit as opposed to the usual arrangement wherein a towing traction unit is assisted by a pusher traction unit to fully load the scraper bowl. The achievement of the foregoing involves a combination of increasing available tractive force and reducing loading resistance. Tractive force is increased by a rigid integration of a traction unit with the scraper frame for pushing rather than towing. Decreased loading resistance is made possible by mounting the scraper bowl for transverse tilting (canting) movement relative to the scraper frame whereby blade draft resistance may be selectively controlled by the operator and particularly during that portion of an excavating operation as the payload approaches rated capacity. Selective bowl cant is, in turn, dependent upon a constructional configuration which will stabilize the bowl, laterally, in the various bowl cant positions and particularly against yaw forces. The constructional configurations herein illustrated for stabilizing the bowl include widely spaced, overhead frame members and additional stabilizing structure positioned outside the peripheral confines of the bowl for transferring lateral forces to the scraper frame.

Description

United States Patent 91 Martin 111 3,711,971 1 Jan 2 3, 1973 1 LARGE CAPACITY SCRAPER UNIT CONSTRUCTION William E. Martin, P.O. Box 187, Kewanee, 111. 61443 [22] Filed: Nov. 2, 1971 [211 App]. No.: 194,897

Related U.S. Application Data [63] Continuation-impart of Ser. No. 77,659, Oct. 2,

1970, abandoned.

[76] Inventor:

, [56] References Cited UNITED STATES PATENTS 2,111,134 3/1938 Allin ..37/126 R 2,304,527 12/1942 Armington et a1. ..37/124 3,138,883 6/1964 Elenburg ..37/124 3,149,429 9/1964 Martin ..37/124 3,302,316 2/1967 Martin ..37/129 3,418,735 12/1968 Martin ..37/129 3,450,418 6/1969 Rice ..37/126 R 3,452,462 7/1969 Martin ..37/126 R 3,435,547 4/1969 Martin ..37/124 3,460,279 8/1969 Martin ..37/124 X 3,501,856 3/1970 Martin ..37/124 X 3,443,329 5/1969 Martin ..37/129 Assistant ExaminerEugene H. Eickholt AttorneyColton & Stone [57] ABSTRACT The largest capacity earth moving scrapers may be loaded to their rated capacity using a single powered traction unit as opposed to the usual arrangement wherein a towing traction unit is assisted by a pusher traction unit to fully load the scraper bowl.

The achievement of the foregoing involves a combination of increasing available tractive force and reducing loading resistance. Tractive force is increased by a rigid integration of a traction unit with the scraper frame for pushing rather than towing. Decreased loading resistance is made possible by mounting the scraper bowl for transverse tilting (canting) movement relative to the scraper frame whereby blade draft resistance may be selectively controlled by the operator and particularly during that portion of an excavating operation as the payload approaches rated capacity.

Selective bowl cant is, in turn, dependent upon a constructional configuration which will stabilize the bowl, laterally, in the various bowl cant positions and particularly against yaw forces. The constructional configurations herein illustrated for stabilizing the bowl include widel spaced, overhead frame members and additional sta illzmg structure positioned outside the peripheral confines of the bowl for transferring lateral forces to the scraper frame.

41 Claims, 27 Drawing Figures PAIENTEDJAH 23 ms 3. 71 1. 971

sum UlUF 11 FIG. 2

INVENTOR WILLIAM E. MARTIN FIG. I

BY 6*. v/fizil ATTORNEYS.

PAIENTEDJMI 23 I975 SHEET UZUF 11 INVENTOR WILLIAM E. MARTIN ATTORNEYS.

FIG. 6

INVENTOR WILLIAM E. MARTIN BY Ma, ATTORNEYE.

PATENTEUJMIZS I975 3,711, 971

vSHEET 05 [1F 11 ATTORNEYS.

PATENTEDJAH 23 I975 SHEET 08 0F 11 FIG. l2

FIG. I?)

INVENTOR WILLIAM E. MARTIN BY aka/Jaw ATTORNEYS.

PAIENTEDJ1H23 I975 'SHEET 117111 11 ATTORNEYS PATENTEDJAHZB I975 SHEET U8UF 11 FIG. l9

FIG. 20

INVENTOR WILLIAM E. MARTIN ATTORNEYS.

PATENTEDJAH 23 I915 SHEET [19 [1F 11 INVENTOR WILLIAM E. MARTIN FIG. 23

ATTORNEYS.

PATENIEnJAnza I975 SHEET 10 [1F 11 BY wan/24.;

ATTORNEYS.

PATENTED JAN 23 I975 SHEET llUF 11 INVENT WILLIAM E. MAR

ATTORNEYS.

LARGE CAPACITY SCRAPER UNIT CONSTRUCTION CROSS REFERENCE TO RELATED APPLICATION This is a continuation-in-part of Applicants copending application Ser. No. 77,659, filed Oct. 2, 1970, now abandoned.

BACKGROUND OF THE INVENTION Large capacity self-loading scrapers are conventionally towed by a front traction unit through an articulating hitch connection. It is axiomatic, in the earth moving industry, that such scrapers require the assistance of a second, or pusher, traction unit in a majority of those excavating operations in which the scraper is normally employed. Thus, while the single towing traction unit may provide sufficient draw bar pull to effect initial scraping operations; as the scraper bowl approaches its filled capacity which may be on the order of 25 yards for example, a point is reached in virtually all soil conditions where resistance to further movement within the cut exceeds available draft long before the bowl is filled to its rated capacity. It becomes impossible at an even earlier point in time to effect reactivation of the load, i.e., to stopand then recommence scraping operations. In either of these events resulting in the inability to load to rated capacity, two choices are thus available: an operator may proceed to the dump area with less than a capacity load or a second traction unit may be utilized to assist the forward traction unit in loading the bowl to its rated capacity. The former involves a substantial loss in actual applied work time and reduces the effectiveness of a large capacity scraper to that of a far more economical smaller capacity scraper which, in effect, renders impractical the selection of the first stated option. The latter option employing a second pusher tractor, although widely used, involves a very substantial expense for the second traction unit whose cost cannot be effectively defrayed because of its large percentage of standby time. i

The use of endless loading conveyors greatly increase the loading capacity of the larger scraper units; however, such loading converyors are, themselves, quite expensive and are not suitable for some soil conditions. Consequently, the large capacity self-loading scraper requiring a standby pusher unit is generally considered to be standard equipment for large commercial excavating work.

Stated in somewhat obvious terms; the problem reduces to one of providing sufficient tractive force to overcome resistance to forward movement of the scraper unit during an excavating operation.

Assuming a traction unit of unlimited horsepower, the factors determinative of available tractive force are: (1) road adhesion; (2) vehicle weight; (3) vehicle wheel base length; (4) relationship of the front and rear axles to the center of gravity; (5) coefficient of rolling resistance; and (6) the height of the center of gravity.

The cumulative resistance factors making up the overall resistance to forward movement of the scraper unit which must be equalled or exceeded by the applied tractive force during a scraping operation are a function of: (1) blade draft (cutting) resistance; (2) soil cohesion; (3) internal friction of the soil; (4) soil-metal friction; (5) soil-metal adhesion; (6) surcharge (weight of loaded soil); and (7) rolling resistance of the vehicle. Inasmuch as all scraping operations involve shearing and lifting of the soil, the foregoing factors may be broadly grouped into three categories, viz. (1) rolling resistance; (2) resistance to shear; and (3) resistance to upward movement of the soil. This latter resistance is the preponderant factor in virtually all scraping operations and increases dramatically as the scraping operation continues with the concomitant increase in surcharge. An approximation of the percentage power requirements to overcome the aforestated resistance factors are as follows:

To overcome rolling resistance:

It is, of course, the latter factor which is primarily responsible for the requirement of a second or pusher traction unit to fully load a large capacity scraper to its rated capacity.

It will be appreciated from the foregoing that it is not the size of the traction power plant that is critical but, rather, the draw bar pull that can be exerted by the traction unit which is typically referred to as the tractive force discussed, supra.

The primary object of the invention is to provide a large capacity self-loading scraper which requires but a single traction unit to load its rated capacity.

Ancillary advantages inhering from the scraper construction herein disclosed include faster loading and contour excavating.

SUMMARY OF THE INVENTION Basically, the invention involves a combination of increasing available tractive force and reducing loading resistance.

The increase in tractive force is achieved by rigidly integrating the traction unit with the scraper frame for pushing rather than towing. Steering is effected by a front steerable wheel unit on the forward scraper frame.

The decrease in loading resistance is made possible by mounting the scraper bowl for transverse tilting- (canting) movement relative to the scraper frame. The ability to cant the bowl during a scraping operation provides a selective control of blade draft resistance to decrease loading resistance which decreased loading resistance coupled with the increased tractive force available with a rear mounted traction unit permits the largest scraper bowls to be loaded to capacity. This arrangement also permits a first deep cut to be made so that a subsequent cut parallel to and intersecting the first cut may be effected in the bowl level position while yet retaining decreased blade draft since one side of the bowl cutting edge will be doing little if any work during the second run. Reactivation of much larger loads, i.e., starting and stopping during a scraping operation, is also made possible by the decreased blade draft associated with bowl cant operation.

I It is important to note that, in either of the foregoing enumerated instances, available tractive force increases as the weight of loaded material increases so that this increased tractive force is available simultaneously with the decreased blade draft resistance made possible by the cant bowl operations, just described.

Neither rear mounted traction units nor selectively tiltable scraper bowls are new, either singly or in combination; as exemplified in U.S. Pats. No. 3,149,429 and No. 3,435,547 which are merely representative of a large number of conventional small and intermediate range scrapers. It has been found that the combination of a rear mounted traction unit and a selectively tiltable bowl makes it possible to self-load the largest commercially available scrapers to their rated capacity whereas neither of these arrangements, alone, is sufficient to permit self-loading to-rated capacity under all working conditions in the absence of a second traction unit if,

and only if, bowl stability may be achieved as discussed,

infra.

Most of the tiltable bowl assemblies of the prior art which have been powered by a rear traction unit, as in U.S. Pat. No. 3,435,547, have evolved primarily as an accessory unit for existent equipment such as a motor patrol grader thus necessarily limiting their size to fall within the low to medium capacity range in order to permit their positionment beneath the motor grader frame structure. These prior constructions have included tiltable bowl mountings for the usual purpose of effecting contour excavating.

The very large capacity bowls are not normally used for contour excavating and, consequently, there has been little if any activity directed toward the development of a canting bowl of large capacity for the rather obvious reason that no particular known need existed for such a construction. Furthermore, there is substantially more involved in the practical solution to the problems necessarily incident to an extension of the teachings contained in the prior art canting bowl structures than simply a change in size. The primary concern is one of lateral stability. Thus, while universally connected link and/or piston-cylinder mountings suspended from an overhead frame provide sufficient lateral stability for small scraper bowls of the type known to the prior art, they would render the large capacity scrapers of the type with which this invention is concerned totally inoperative. Basically, the distinction is one of mass and inertia. It is one thing to control lateral stability and/or yaw of a scraper bowl weighing a few thousand pounds fully loaded and quite another where the concern is for a scraper unit having a fully loaded'gross weight of approximately 150,000 pounds and a load capacity of approximately 60,000 pounds for a 25 yard pay load With a typical 500 HP power plant exerting a tractive rim pull of 72,000 pounds the magnitude of the developed yaw forces as one edge of a canted bowl is lowered into digging position would far exceed the counter stabilizing effect exerted by the prior art bowl suspension systems. The problem of lateral stability and yaw control, while not unique to a canting bowl construction, is greatly magnified thereby because of the requirement that the various interconnecting suspension structures be universally mounted to permit the desired tilting movement thereby losing the lateral dimensional stability that is inherent in the conventional, non-universal pivot connections provided for a vertically movablelift arm construction.

Although it was to be expected'that a rear'mounted traction unit would provide a greater tractive force; the

actual magnitude of this increase far exceeded that to be expected as on the order of a 44-91 percent increase (depending on the road adhesion coefficient) over front mounted traction units for a fully loaded 150,000 pound scraper unit.

The foregoing may be verified by substitution into the following comparative formulas for the determination of maximum tractive force development in front and rear wheel drive vehicles: I

where P, and P, are the maximum tractive forces (in pounds) that can be developed without wheel slip for front and rear wheel drive vehicles, respectivey;

p. is the road adhesion coefficient;

W is the vehicle weight in pounds;

L is the vehicle wheel base in inches;

L5 and L are the respective distances from the center of gravity to the front and rear axles in inches;

f is the coefficient of rolling resistance; and

H is the height, in inches, of the center of gravity from the ground.

in a typical solution of the above equations for a fully loaded 25 yard capacity scraper having a fully loaded gross weight of 150,000 pounds under poor soil conditions where p 0.2 and f 0.15; the rear traction scraper unit develops 44% more usable tractive force, before wheel slip, than is the case for an identical scraper unit having front wheel drive. Under good soil conditions where p, 0.7 and f= 0.015, 91 percent more usable tractive force is developed by the rear wheel drive scraper unit. I

The derivations for the foregoing formulas may be found in Mechanics of Vehicles, by J. J. Taborek, reprinted from MACHINE DESIGN (1957).

It is the recognition of the fact that a rear mounted traction unit could be combined with a large capacity tiltable bowl to increase applied tractive force and decrease loading resistance, respectively, to the point where a second traction unit is superfluous that is he desirable function achieved by this invention. The particular novel structure necessary to carry out the desired function goes to the solution of a problem (lateral and/or yaw stability) which arose as an incident of the recognition that loading resistance can be decreased by the simple expedient of cutting with a canted bowl. Thus, as the stall point is approached in a scraping operation in particularly difficult soil, for example, the bowl can be-tilted and a full load scraped with one edge of the bowl blade. Additionally, one may make a first cut with only a portion of the canted bowl edge and then level the bowlprior to making a second parallel cut to approximately the 'same depth which overlaps the first cut so that blade draft is substantially reduced during both cuts while available tractive force inherently increasing as a function of increasing vehicle weight.

The necessary lateral stability is achieved by universally suspending the bowl substantially within the lateral confines of two transversely spaced frame members which are integral with the scraper unit frame and positioning separate stabilizing members outside the lateral bowl confines which are distinct from the suspension structure. Overall bowl control is then effected con jointly by the suspension structure (for raising, lowering and canting the bowl) and the stabilizing members which function alone or in combination with a portion of the suspension structure to effect a transverse interlock between the bowl and scraper frame to preclude transverse movement of the bowl substantially beyond the transverse confines of the transversely spaced frame members. The imposition of lateral forces to the bowl may thus be transmitted laterally through the stabilizing structure to either the transversely spaced frame members or to another portion of the scraper frame.

When the stabilizing structure is utilized to transmit lateral forces to a portion of the scraper frame other than the widely spaced, overhead frame members, such as directly to the rear traction unit; the bowl lift arms are so related to the overhead superstructure as to insure the transmission of lateral forces imposed at that end of the bowl remote from the stabilizing structure to the widely spaced frame members. This diminishes the application of torsional stresses as would be applied to a central supporting frame member as in the aforereferenced prior art patents as well as avoiding the transmission of those forces to the various hydraulic control cylinders.

Loading resistance may yet be further decreased, in accordance with various embodiments of the invention, by suspending the bowl in such manner that the fore and aft disposition of the bowl floor may be maintained substantially parallel to the earth in both the level and canted scraping positions. This, of course, reduces the height to which the excavated soil must be lifted which, it will be recalled, is the primary contributing factor in determining loading resistance.

Although relating to a theory as yet unproven, it is thought that vibration is a significant factor in reducing loading resistance in those embodiments of the invention herein disclosed where the bowl is towed by the frame of the scraper unit. Thus, resistance to loading at the bowl is transmitted to the forward end of the elongate, transversely spaced frame members which are pushed by a rear mounted traction unit so that the frame members are thought to be alternately tensioned and relieved by the variations in loading resistance applied at the bowl as a scraping operation proceeds. The result of such variations in the bending moments applied to the elongate frame members as a function of the instantaneous changes in loading resistance is to vibrate the bowl and thereby increase loading efficiency. Although it has long been recognized that bowl vibration facilitates loading, the prior-art utilization of this knowledge has involved the addition of vibratory equipment to the scraper rather than he realization of the same as a function of the bowl mounting system,

per se.

In most of the frame towed bowl constructions herein disclosed, the bowl is towed away from the front end of the widely spaced frame members by frame or tow arms downwardly dependent from and rigid with the widely spaced frame members since this arrangement affords a somewhat better transfer of lateral forces, through the bowl lift arms, directly to the spaced frame members. Similarly, in exemplary preferred embodiments of the frame pushed bowls, a pair of frame arms downwardly dependent from and rigid with the rear portions of the widely spaced frame members act as push arms through their interconnection with the rear ends of the bowl lift arms thus, again, assuring a direct transfer of lateral forces to the frame members.

It will be apparent that the principles of the invention applied 0 smaller scraper units will permit self-loading of the same with smaller power plants than have been heretofore required.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic perspective of a mobile scraper frame and bowl with interconnecting structure between the bowl and scraper frame being omitted;

FIG.-2 is a perspective view of a scraper unit employing a front frame towed bowl construction including bowl stabilizing brackets affixed to the bowl side walls;

FIG. 3 is a side elevational view of the scraper unit of FIG. 2 with a portion of the rear traction unit broken away to illustrate the bowl pitch control mechanism;

FIG. 4 is a top plan view of FIG. 3;

FIG. 5 is a sectional view taken along the line 5-5 of FIG. 3 and illustrating the scraper bowl in canted position;

FIG. 6 is a sectional detail view of the universal connection between a bowl lift arm and a frame two arm;

FIG. 7 is a fragmentary elevational view of a scraper unit similar to that of FIG. 3 but illustrating a modified pitch control mechanism;

FIG. 8 is a view of the scraper unit of FIG. 7 illustrating a bowl position intermediate the carry and working positions;

FIG. 9 illustrates the bowl level working condition of the scraperunit shown in FIGS. 7 and 8',

FIG. 10 is an exploded perspective of the pitch control mechanism employed with the scraper unit of FIGS.7-9;

FIG. 11 is a fragmentary side elevational view of a scraper unit similar to that of FIG. 7 but employing a modified pitch control mechanism;

FIG. 12 is a fragmentary side elevational view of a scraper unit similar to that of FIGS. 7 and 11 but em-. control ploying yet a further modified pitch mechanism;

FIG. 13 is a fragmentary side elevational view of a front frame towed bowl wherein both the stabilizing and pitch control mechanism is positioned rearwardly of the bowl;

FIG. 14 is a perspective view of the stabilizing and pitch control mechanism of FIG. 13;

FIG. 15 is a fragmentary elevational view of a scraper unit employing a modified Watts linkage as the stabilizing mechanism;

FIG. 16 is a sectional view taken along line 16-16 of FIG. 15;

FIG. 17 is an elevational view of a scraper unit em ploying a modified bowl to frame towing connection;

FIG. 18 is a sectional view taken along line 18-18 of FIG. 17;

FIG. 19 is a fragmentary elevational view of a scraper unit similar to that of FIG. 17 but employing a further modified towing connection;

FIG. 20 is a sectional view taken along line 20-20 of FIG. 19;

FIG. 21 is a fragmentary elevational view of a scraper unit employing a frame pushed bowl construction;

FIG. 22 is a sectional view taken along line 22-22 of FIG. 21;

FIG. 23 is a view similar to that of FIG. 21 but illustrating a modified bowl lift control mechanism; and

FIGS. 24-27 are elevational views of frame pushed bowl constructions having the stabilizing mechanism positioned forwardly of the bowl and pitch control mechanisms positioned rearwardly thereof respectively corresponding to the pitch control mechanisms of FIGS. 2, l1, 7 and 12.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A more complete understanding of the structural distinctions underlying the several modifications of the invention herein disclosed will be had by prior reference to FIG. 1 schematically depicting that scraper unit structure which is common to the various modifications. Thus, each modification of a scraper unit 10 comprises a mobile scraper frame 12 defined by overhead superstructure 14' bridging a rear traction unit 16' and a forward steerable wheel unit 18'. Overhead superstructure 14 is defined by transversely spaced, parallel frame members 20 which terminate at their forward ends in an integral connection with torque tube 22 integrally connected with goose neck 24' and rearwardly thereof in convergent portions 26' terminating in integral connections to the chassis of rear traction unit 16. A scraper bowl 28 is adapted for lateral stabilization and suspension relative to the scraper frame structure for raising, lowering and canting movement relative thereto within the transverse confines of the overhead, parallel frame members 20 by structure not illustrated in FIG. 1. It is the specific structure for suspending and stabilizing the bowl relative to the mobile frame structure that distinguishes the various embodiments. Power steering control of the forward wheel unit about the axis of steering trunnion 30' may be effected from a rear mounted operators station 32' in any desired manner such as by hydraulic or electric control lines traversing the mobile frame structure. Similarly, the power steering may be remotely powered from a prime mover 34' mounted on the rear traction unit 16 or a separate power steering source may be integrated with the forward wheel unit. Similarly, a forward control station may be mounted integral with the steering trunnion, if desired.

As previously explained, it is the combination of the rear mounted traction unit'and selective control of bowl cant that makes possible the realization of the invention. Bowl cant control, in turn, depends upon lateral stabilization of the bowl relative to the scraper frame. The relationship of the rear mounted traction unit 16' to the overhead superstructure 14' and forward steerable wheel unit 18', as depicted in FIG. 1, satisfies the first essential element of the combination while the particular transverse spacing of the overhead frame members 20', as shown in FIG. 1, to lie substan- Inasmuch as that scraper unit structure depicted in FIG. 1 is common to all of the modifications herein disclosed, the tens and units reference digits used in FIG. 1 are retained throughout the drawings.

FRAME TOWED BOWL CONSTRUCTIONS Although the basic objects of the invention are met by bowl suspension arrangements wherein the bowl is pushed by the mobile frame structure, superior results have beenachieved by a mounting of the bowl in such manner that it is towed from adjacent the forward end of the overhead superstructure. These superior results are thought to derive from an inherent vibration induced at the bowl cutting edge as a function of the instantaneous variations in loading resistance as transmitted from the bowl to the forward end of the bridging superstructure, which may have an overall length of from 20 to 30 feet and which is, therefore, subject to low amplitude flexure in response to the applied bending forces.

A first scraper unit 10 embodying a towed bowl construction is illustrated in FIGS. 2-6 wherein the bowl 28 is adapted to be towed from adjacent the forward end of superstructure 14 through the intermediary of opposed bowl lift arms 36 and tow arms 38 rigidly dependent from superstructure 14 adjacent the forward terminus of overhead frame members 20. Each tow arm 38 consists of spaced brackets 40 between which the lift arms 36 are mounted on self-aligning universal bearing assemblies 42 in the manner more specifically illustrated in FIG. 6. Each bearing assembly 42 includes a shaft 44 rigidly bridging spaced brackets 40 and rigidly supporting, centrally thereof, the inner race 46 of bearing assembly 42. The outer race 48 of each bearing assembly is rigidly secured within an opening formed in the forward end of each lift arm 36 so that each lift arm may pivot about the axis of shaft 44 and undergo canting movement relative thereto as illu's trated by the phantom line canted position in FIG. 6.

The degree of transverse tilt, or cant, permitted by each universal bearing assembly 42 is obviously delimited by the cross sectional height and thickness of lift arm 36, as viewed in FIG. 6, and the transverse spacing between brackets 40. Bowl lift arms 36 are universally connected intermediate the ends thereof with opposed side walls 50 of bowl 28 via universal bearing assemblies 52. The inner and outer races of bearing assemblies 52 are identical with the universal, self-aligning races-46, 48 illustrated in FIG. 6 and the bearing assemblies 52 differ from bearing assemblies 42 only in the cantilever stub shaft mounting illustrated in FIGS. Thus each bearing assembly 52 includes a short stub shaft 54 rigidly secured at one end thereof in an opening in bowl side wall 50. The other end of stubshaft 54 extends outwardly of the bowl side wall and rigidly supports an inner race 56 identical to the inner race 46 shown in FIG. 6. A coacting outer race, identical to the outer race 48 of FIG. 6, is rigidly mounted in an opening in the adjacentlift arm 36. The bowl may thus pivot relative to lift arms 36 about the common axis of stub shafts 54 and cant relative to the lift arms generally after the manner described in connection with the phantom line showing of FIG. 6. Similar universal bearing connections 58 interconnect the rear ends of lift arms 36 with lift cylinders 60. A bowl pitch control cylinder 62, universally interconnected between brackets 64, 66 on the rear of bowl 28 and the chassis of rear traction unit 16, respectively, completes the description of the bowl towing and suspension structure.

The bowl is stabilized laterally and particularly against yaw forces developed during cant bowl operation by a pair of stabilizing brackets 68 secured to bowl side walls 50 which coact with elements of the suspension system, just described, to effect a transverse interlock between the bowl and scraper frame to preclude lateral movement of the bowl substantially beyond the solid line position of FIG. 6. The stabilizing brackets 68 are slotted over an intermediate portion of their lengths to define elongate slots 70 loosely receiving the rear ends of lift arms 36 to captivate the same against lateral movement relative to the bowl side walls within those limits imposed by the relative dimensions of the slots and lift arms. The elongate length of each slot 70 is such as to permit the desired full range of bowl raising and lowering movements as controlled by lift cylinders 60.

The particular transverse dimension of each slot 70 is calculated to permit limited twisting movement, or rotation generally about the'longitudinal axes, of lift arms 36 relative to the bowl having due regard for the width and thickness of the lift arms where they traverse slots 70. An exemplary dimensional relationship would permit an approximate 2W rotation of the lift arms generally about their longitudinal axes in the manner illustrated in FIG. and as permitted by the

universal mountings

42, 52 and 58. The spacings of the brackets 40, defining each towing arm 38, are similarly calculated to permit limited twist or rotation of bowl arms 36, generally about their longitudinal axes, relative to tow arms 38. An exemplary dimensioning might involve a permissible lift arm twist of 2%" relative to the tow arms. Thus, in accordance with the cited exemplary dimensions, the how] could be canted as much as 5 relative to the scraper frame. This will become clear from an inspection of FIG. 5 bearing in mind that the bowl is not only universally mounted on the lift arms but the lift arms are, in turn, universally mounted relative to the scraper frame. Thus, upon opposite actuation of lift cylinders 60, as in FIG. 5, lift arms 36 are rotated generally about their longitudinal axes through an angle a relative to the scraper frame and integrally connected tow arms 38; while the bowl 28 rotates generally about a longitudinal axis, relative to lift arms 36, through an angle [3 The limits of angle a are defined by the spacing between tow arm brackets 40 whose engagement with opposite diagonal edges of the forward ends of lift arms 36 limits their relative twisting movement as indicated in FIGS. 5 and 6. Similarly, the rotation of bowl 28 relative to the lift arms (angle 3 is arrested when the opposite diagonal edges of the rear ends of lift arms 36 engage the opposed side walls of slots 70 in bracket 68.

The relative angular relationship of parts, just described, relates primarily to yaw stabilization when cutting with the bowl in a canted position and it is important to note that the bowl is stabilized against those yaw forces-tending to rotate the bowl about a generally vertical axis irrespective of whether the bowl is in a maximum cant position as just described and'illustrated in FIG. 5. This for the reason that further rotation of the bowl about a generally vertical axis after the play, is taken up in the loose connections defined by the interengagement between lift arms 36, slot and tow arms 38 is resisted by the interlocking engagement of the parts which defines the transverse interlock previously described. It follows that, in this particular embodiment utilizing brackets 68 as the stabilizing means, yaw stabilization is at a maximum in the maximum bowl cant position since, in this position, the parts are already interlocked as illustrated in FIG. 5. Lateral stabilization against other than yaw forces when cutting in a bowl level mode takes place in a similar manner.

The positioning of the bowl substantially within the transverse confines of the widely spaced overhead frame members 20 of superstructure 14 has been found to be essential to provide the requisite yaw stability to resist that magnitude of forces involved in cant bowl operation of the larger size scrapers. The explanation is, of course, one of outboard stabilization, i.e., a transmission of the working forces to a stable superstructure spanning the movable component (bowl) whose lateral movements are to be resisted.

A further reduction in loading resistance of the scraper unit 10 is made possible by selective energization of bowl pitch control cylinder 62 to control bowl movement between the solid and dotted line positions of FIG. 3 to maintain the fore and aft orientation of bowl floor 72 substantially parallel to the cut thereby decreasing the height to which the excavated material must be lifted. It is important to note that the various universal connections between the bowl and scraper frame permit the bowl floor to be so oriented even during cant bowl operation.

An apron 74 is conventionally mounted on bowl side walls 50 for bowl opening and closing movement about pivots 76 under the control of cylinders 78.

It will be apparent from the foregoing that scraper unit 10, illustrated in FIGS. 2-6, embodies all three of the previously discussed factors contributing to decreased loading resistance viz. bowl cant, forward frame towing and bowl pitch control.

Assuming a bowl empty carry position as in the solid line position of FIG. 3; extension of both lift cylinders 60 would pitch the bowl forwardly to bring bowl cutting blade 80 into excavating engagement with the earth in the usual manner as-indicated in the intermediate phantom line bowl position of FIG. 3. As cylinders 60 extend to lower the rear ends of lift arms 36, the forward end of the bowl is similarly lowered as by the lowering of universal bowl pivotmountings 52. If it now be desired to excavate in the cant bowl position, lift cylinders 60 may be oppositely actuated to cant the bowl as previously described. In either the bowl level or canted position, the rear end of the bowl may be lowered simultaneously with the positioning of the bowl in excavating position by appropriate. extension of pitch cylinder 62 as indicated in the lower phantom line position of FIG. 3.

The three additional frame towed bowl constructions illustrated in FIGS. 7-10, 11 and 12, respectively, differ from the embodiment illustrated in FIGS. 2-6 only in the details of the bowl pitch control mechanism wherein the single pitch control cylinder 62 (FIG. 3) is replaced by various control cylinder operated linkage mechanisms for performing the same function of pitch control. The advantages inherring in the modified constructions employing linkage mechanisms are the permissible use of smaller pitch control cylinders and a further increase in bowl stability.

The details of a parallelogram bowl tilt control assembly 136 are seen in FIGS. 7-10 to include a generally vertically disposed main support link 138 which is universally mounted adjacent an upper end thereof via universal bearing assembly 140 between spaced mounting brackets 142 on rear traction unit 116. A cross shaft 144 is universally mounted, intermediate the ends thereof, adjacent the other end of support link 138 by means of a universal, self-aligning bearing assembly 146 of the type shown in FIG. 6 and pivotally supports, at opposite ends thereof, the opposed parallelogram subassemblies 148, per se. The

parallelogram subassemblies include generally upright links 150 journalled intermediate the lengths thereof on cross shaft 144 and pivotally mounting, at opposite ends thereof,

parallel links

152, 154 which parallel linksare, in turn, pivotally connected to spaced lugs 156 on the rear of bowl 128. The lower links 152 may be interconnected with links 150 by a common pivot shaft158 which pivotally mounts the cylinder end of pitch control ram 160 while the piston end thereof is interconnected with the rear of bowl 128 between spaced, subassembly mounting lugs 162; alternatively, separate control rams could be provided for each parallelogram sub-assembly. It will be seen that only the two

universal pivot connections

140 and 146 are required to provide the appropriate bowl pitch control while yet permitting bowl cant throughout the various carry, intermediate and level (parallel fore an aft bowl floor positionment) bowl excavating positions illustrated in FIGS. 7, 8 and 9, respectively. Lateral stability is achieved, as in FIGS. 2-6, by the described coaction of lift arms 164 with tow arms 166 and stabilizing brackets 168.

A scissor link, bowl tilt control assembly 236 is illustrated in FIG. 11 as including opposed pairs of pivotally related

links

238, 240 joined at respective end portions by pivot 242 and at their other ends to rear traction unit 216 and the bowl 228, respectively. The mounting ,oflink 240 to traction unit 216 is by a universal bearing assembly 244. Pivot 242 may be defined by a common pivot shaft which also supports the cylinder end of pitch control ram 246. Concurrent contraction of pitch control ram 246 and extension of lift cylinders 248 results in a' lowering of the bowl from the solid line carry position of FIG. 11 to the phantom line working position, as will'be apparent.

A toggle link pitch control assembly is illustrated in FIG. 12 which may include a single main support link 336 universally suspended from rear traction unit 316 and universally supporting, at the other end thereof, a cross shaft 338 to the opposite ends of which are pivoted bell cranks 340 which are fulcrummed on cross shaft 338 and have their opposite ends respectively connected with the bowl 328 and opposed pitch control cylinders 342. Universal connections 344 between the pitch control cylinders and bell cranks completes the description of the toggle link assembly which is operative to maintain a fore and aft parallel bowl positionment in the manner indicated by the relative solid and dotted line positions of FIG. 12 while yet accommodating bowl cant by the universal mounting of hell cranks 340 relative to the rear traction unit.

One alternative to the use of stabilizing brackets secured to the bowl side walls for coaction with a part of the suspension system to provide the essential lateral stability is illustrated in FIGS. 13 and 14. The scraper unit 410, fragmentarily shown in FIG. 13, differs from that of FIGS. 7-10 in that the stabilizing brackets 168 have been omitted and a wide, generally I-I-shaped stabilizing plate 436 has been substituted for each pair of

links

152 and 154 as best seenin the perspective showing of FIG. 14. Thus, in a manner similar to that construction shown in FIG. 10, the side links 438 are mounted for conjoint universal movement relative to the scraper frame by virtue of the

universal pivot mountings

440, 442 interconnecting main support link 444 with the rear traction unit 416 and cross shaft 446, respectively. The side sway inherently permitted by the

separate links

152, 154 of the embodiment shown in FIGS. 7-10 is eliminated by the establishment of a transverse interlock through the close fitting pivot connections between links 438 and stabilizing plates 436. Thus, the alternative arrangement shown in FIGS. 13 and 14 performs the dual functions of laterally stabilizing the bowl and controlling bowl pitch.

A third exemplary construction which provides the requisite lateral stability for cant bowl operation involves a modified Watts linkage interacting between the bowl support arms and the scraper frame as illustrated by the scraper unit 510 in FIGS. 15 and 16. The details of the stabilizing structure are best illustrated in FIG. 16 wherein the same is seen to comprise a radius link 5 36 mounted at the center thereof for rotation on a large stub shaft 538 rigid with rear traction unit 516. Relatively massive radius arms 540, 542 are universally connected to opposite ends of radius link 536 and are parallelly extended in opposite directions to universal connections 544 with an upturned extension 546 of one bowl liftarm and a downturned extension 548 of the other lift arm. The solid line, parallel position of radius arms 540, 542 in FIG. 16 typifies the bowl level carry position. It will be apparent that conjoint downward movement of bowl lift arms 550 is accommodated by a clockwise movement of radius link 536, as viewed in FIG. 16, as the'radius armsfollow the downwardly moving lift arms to the bowl level,-phantom line position of FIG. 16. Similarly, differential actuation of he bowl lift arms is permitted to assume the phantom cant bowl position of FIG. 16 with the radius arms effecting a further clockwise rotation of radius link 536.

- The result of this modified Watts linkage is to, in effect, provide a rigid link or transverse interlock construction bridging the rear ends of bowl lift arms 550 and, concomitantly, transmit lateral forces directly to the rear traction unit through stub shaft 538. This stabilizing linkage at the rear end of the bowl coacts with the widely spaced tow arms 552 and their method of interlocking with the forward ends of lift arms 550 in the manner previously explained in connection with the embodiment of FIGS. 2-6 to provide an exceptionally stable bowl suspension. Apart from the modification of the bowl lift arms to include rearward extensions to which the radius arms are connected'and the details of the modified Watts linkage, just described, the scraper unit 510 is substantially identical to that illustrated in FIGS. 2-6 wherein the modified Watts linkage replaces the function of stabilizing brackets 68 and pitch control is retained by a single cylinder 554.

A modified towed bowl construction is illustrated in connection with the scraper unit 610, shown in FIGS. 17 and 18. Scraper unit 610 retains the basic stabilizing mechanism of the scraper unit 510 (FIGS. 15 and 16) and differs therefrom primarily in the details of the bowl to frame parallelogram towing connection 636 which includes the bowl lift cylinder 638 and in the employment of two cylinders 640 interconnected between the overhead frame and bowl for performing the functions of both bowl cant and bowl pitch control.

The single tow arm 642 of this embodiment converges downwardly from a large, rigid securement area centrally of superstructure torque tube 622, to terminate in an offset fork 664 between the legs of which fork is rigidly supported a cylinder mounting shaft 646. The relatively massive tow arm body above fork 644 rigidly supports the outer race 648 of a universal, selfaligning bearing assembly 650 whose inner race 652 is rigid with cross shaft 654. Upstanding support links 656 are rigid with the outer ends of cross shaft 654 and are spaced on either side of the convergent portions of tow arm 642 a sufficient distance to permit the same to cant, relative to the tow arm, with their rigidly interconnecting cross shaft 654 about bearing assembly 650 throughout an are equal to that of the'desired bowl cant. Parallelogram links 658, 660 are pivotally interconnected between each of the support links 656, on

stub shafts

662, 664 and spaced mounting brackets 666 rigidly carried by torque tube 668 interconnecting the forward ends of bowl lift arms 670 which lift arms are, in turn, rigid with the side walls of bowl 628. The rearward ends of

links

658, 660 are pivoted to mounting brackets 666 via stub shafts 672 and a cross shaft 674, respectively. A universal connection 676 between the cylinder end of lift cylinder 638 and shaft 646 as well as a conventional piston end connection to cross shaft 674 permits canting movement of the bowl and parallelogram towing connection 636 relative to tow arm 642 about bearing assembly 650.

The rear end of the bowl is stabilized by a modified Watts linkage 678 identical to that described in connection with FIGS. 15 and 16 except that the upturned and

downturned arms

680, 682 to which radius arms 684 are pivoted'are integrally connected with the rear of bowl 628 rather than being a rearward extension of the lift arms. I

The pitch/cant cylinders 640 are interconnected between the bowl and overhead frame members 620 to control both bowl pitch and tilt.

It will be seen that this embodiment is characterized by all three of the aforenumerated operating advantages, i.e., bowl cant, forward frame towing and bowl pitch control.

In operation of the scraper unit 610, bowl lift is controlled by cylinder 638 which may be activated, alone, to control depth of cut in the manner of a conventional scraper or, in combination with conjoint extension of cylinders 640, to maintain fore and aft orientation of the bowl parallel to the ground as shown in phantom lines in FIG. 17. When bowl cant operation is desired, cylinders 640 may be oppositely activated to cant the bowl and parallelogram towing connection about ball assembly 650 and the modified Watts linkage 678.

It has been found that the required transmission of lateral forces to the widely spaced frame members 620 can be achieved via the wide area securement of the single tow arm 642 to torque tube 622 when the bowl lift arms are integral with the bowl side walls rather than being pivotally related thereto.

The scraper unit 710 (FIGS. 19 and 20) is similar to the unit 610, just described, in that the lift arms 736 are rigid with the bowl and the same is stabilized by a rear mounted modified Watts linkage 738 which linkage is, however, interconnected with upturned and downturned

integral extensions

740, 742 of lift arms 736. Accordingly, as in the case of scraper unit 610, raising, lowering and canting bowl movements take place as a direct function of lift arm movement. Due to the fact that relative movement between the lift arms and bowl is precluded, the transmission of lateral forces to the widely spaced frame members 720 may be conveniently accomplished through a single universal towing connection 744 best shown in FIG. 20. A large mounting post 746 including reinforcing ribs 748 terminating in exposed mounting lugs 750 is rigidly dependent from a large central area of torque tube 722. The forward ends of bowl lift arms 736 are rigidly interconnected by a torque tube or brace 752 to the center of which is welded a bearing mounting lug 754 which rigidly mounts, adjacent the forward end thereof, the outer race 756 of a universal bearing assembly 758. The inner race of the bearing is secured to a shaft 760 bridging mounting lugs 750. The bowl 728 is thus towed through a single large central connection with brace 752 rigidly interconnecting the lift arms. Lateral forces acting on the forward end of the bowl are transferred to the widely spaced overhead frame members 720 via the rigidly interconnected lift arms and brace 752, the mounting post 746 and torque tube 722. The rear ends of lift arms 736 are stabilized by the modified Watts linkage 738.

This particular modification (FIGS. 19 and 20) lacks the selective bowl pitch control feature but retains that forward frame tow feature productive of bowl vibration.

In operation of the scraper unit 710, the bowl may be lowered from the solid line carry position of FIG. 19 to a lower working position by extension of lift cylinders 762 to pivot. the lift arms and integrally connected bowl downwardly about a generally horizontal axis passing through bearing assembly 758. Opposite actuation of the lift cylinders raises one arm while lowering the other to cant the bowl rigidly carried thereby; the universal pivot connection 758 and modified Watts linkage 738' accommodating such movement in the manner previously described.

FRAME PUSHED BOWL CONSTRUCTIONS The remainder of the modifications herein disclosed relate to frame pushed bowl constructions wherein advantage is not taken of that decreased loading resistance made possible by inherent bowl vibration operative as a function of the long towing lever arm" extending forwardly of the rear traction unit. Nevertheless, and as previously explained, the combination of bowl cant and lateral stabilization features, alone, make possible the rated capacity loading of the largest scrapers as will become even more fully apparent from a description of the embodiments shown in FIGS. 21-23 which also lack the pitch control feature.

The frame pushed scraper bowl 828 of scraper unit 810 (FIGS. 21 and 22) is pushed directly by rear traction unit 816 adjacent the lower rear edge of ejector section 836 through a universal bearing assembly 838 which, also, supports the rear end of the bowl for canting movement. The forward end of the bowl is supported from superstructure torque tube 822 via a mounting post 840, modified Watts linkage 842, identical with that previously described, and bowl lift arms 844 rigid with bowl side walls 846. Lift cylinders 848 are universally interconnected between overhead frame members 820 and the forward ends of lift arms 844. It will be apparent that simultaneous extension of lift cylinders 848 will lower the forward end of the bowl from the carry position of FIG. 21 to a lower working position while opposite actuation of the lift cylinders will cant the bowl generally about a longitudinal axis extending between bearing assembly 838 and main pivot shaft 850 of linkage 842.

In FIG. 23 is illustrated an alternate arrangement for controlling lift arms 936 wherein lift cylinders 938 act through bell cranks 940 and links 942 interconnected between the bell cranks and lift arms. The

connections

944, 946 between the bell cranks and lift arms are, of course, universal connections to permit the required bowl cant.

A somewhat better transfer of lateral forces to the overhead frame members is achieved by a pushing interconnection between push arms downwardly dependent from the spaced overhead frame member and the rear ends of the bowl lift arms. The modifications disclosed in FIGS. 24-27 are exemplary wherein the primary distinctions reside in alternate pitch control arrangements.

The scraper unit 1010 shown in FIGS. 24 includes a pair of lift arms 1036 universally interconnected with bowl side walls 1038 as illustrated in connection with FIG. 5 and whose rear ends are universally connected with push arms 1040 downwardly dependent from frame members 1020 by universal bearing assemblies 1042. The forward ends of lift arms 1036 are interconnected with superstructure torque tube 1022 in a manner identical to that shown in FIG. 21 and lift cylinders' 1044 are universally interconnected between overhead frame members 1020 and the forward ends of the lift arms. Bowl pitch is controlled by a single pitch control cylinder 1046 universally interconnected between mounting ears 1048 on the rear of bowl 1028 and overhead superstructure 1014.

The scraper unit 1110 shown in FIG. 25 is identical to that of FIG. 24 except for the bowl pitch control mechanism which includes scissor link pairs 1136, 1138 interconnected between opposite rear sides of the bowl 1128 and appropriate mounting lugs 1140 on rear traction unit 1116. Adjacent ends of

links

1136, 1138 are interconnected by a cross shaft 1142 which may be universally mounted relative to scraper unit 1110 in a manner identical to the mounting of cross shaft 144 in FIG. 10 so that the scissor links, pivotally interconnected by cross shaft 1142 on either side of bowl 1128, may follow canting movement of the bowl as induced by opposite actuation of lift cylinders 1144. A pair of pitch control cylinders 1146 may be universally interconnected between the sides of bowl ejector section 1148 and cross shaft 1142 or, alternatively, a single pitch control cylinder may interconnect the rear of bowl 1128 and cross shaft 1142. Retraction of pitch cylinders 1146 in conjunction with extension of lift cylinders 1144 results in a lowering of both the front and rear ends of bowl 1128 from the carry position of FIG. 25 to an excavating position wherein the fore and aft orientation of the bowl is substantially parallel to the cut. Bowl cant is permitted by the universal suspension of cross shaft 1142 from the rear traction unit and the forward modified Watts linkage 1150.

Scraper unit 1210 shown in flG. 26 is identical, in construction and operation, to that of FIG. 25 except that a parallelogram pitch control linkage 1236 is substituted for the scissor pitch control linkage of FIG. 25. The construction and operation of the parallelogram pitch control linkage is like that illustrated and described in connection with FIGS. 7-10.

Scraper unit 1310 is, also, identical in construction and operation to scraper l 1 10 of FIG. 25 except for the substitution of a toggle link pitch control mechanism 1336 which is like that illustrated and described in connection with FIG. 12.

I claim:

1. A self loading scraper having a mobile scraper frame defined by overhead superstructure bridging a rear traction unit and a forward wheel unit; said superstructure including transversely spaced frame members rigid with said rear traction unit; a scraper bowl positioned substantially within the transverse confines of said spaced frame members; bowl control means interconnected between said scraper bowl and said said mobile scraper frame for interlocking said bowl and scraper frame against transverse movement of said bowl substantially beyond the transverse confines of said spaced frame members, and for'raising, lowering and canting said bowl relative to said scraper frame; said bowl control means including suspension means suspending said how] substantially within the transverse confines of said spaced frame members for effecting said raising, lowering and canting movements; and said bowl control means further including stabilizing means, in addition to said suspension means, positioned wholly exteriorly of the peripheral confines of said bowl for transmitting lateral working forces between said bowl and said spaced frame members and rigidly interconnected traction unit.

2. The scraper of claim 1 wherein said suspension means include universal connection means.

3. The scraper of claim 2 wherein said suspension means includes bowl lift arms mounted on opposite sides of said bowl and power lift means interconnected between said lift arms and overhead superstructure.

4. The scraper of claim 1 including power operated pitch control means interconnected between said scraper frame and bowl for selectively controlling bowl pitch.

5. The scraper of claim 4 wherein said power operated pitch control means comprise a hydraulic ram interconnecting said scraper frame and bowl.

Claims

1. A self loading scraper having a mobile scraper frame defined by overhead superstructure bridging a rear traction unit and a forward wheel unit; said superstructure including transversely spaced frame members rigid with said rear traction unit; a scraper bowl positioned substantially within the transverse confines of said spaced frame members; bowl control means interconnected between said scraper bowl and said said mobile scraper frame for interlocking said bowl and scraper frame against transverse movement of said bowl substantially beyond the transverse confines of said spaced frame members, and for raising, lowering and canting said bowl relative to said scraper frame; said bowl control means including suspension means suspending said bowl substantially within the transverse confines of said spaced frame members for effecting said raising, lowering and canting movements; and said bowl control means further including stabilizing means, in addition to said suspension means, positioned wholly exteriorly of the peripheral confines of said bowl for transmitting lateral working forces between said bowl and said spaced frame members and rigidly interconnected traction unit.

6. The scraper of claim 4 wherein said power operated pitch control means comprise opposed link pairs universally carried by said scraper frame.

7. The scraper of claim 4 wherein said power operated pitch control means comprise a pair of links universally carried by said scraper frame.

8. A self loading scraper having a mobile scraper frame defined by overhead superstructure bridging a rear traction unit and a forward wheel unit; said superstructure including traNsversely spaced frame members rigid with said rear traction unit; a scraper bowl positioned substantially within the transverse confines of said spaced frame members; bowl control means; including stabilizing means positioned exteriorly of the peripheral confines of said bowl, for effecting a rigid transverse interlock between said scraper frame and bowl for transmitting transverse working forces from said bowl to said spaced frame members and the traction unit; and said bowl control means further including suspension means, in addition to said stabilizing means, for raising, lowering and canting said bowl.

9. In a self-loading scraper having a mobile scraper frame defined by overhead superstructure bridging a rear traction unit and a forward wheel unit, the improvement comprising: said superstructure including transversely spaced frame members rigid with said rear traction unit; suspension means suspending a scraper bowl from said scraper frame substantially within the transverse confines of said spaced frame members for raising, lowering and canting said bowl relative to said frame members; stabilizing means positioned exteriorly of the peripheral confines of said bowl for limiting relative transverse movement between said bowl and scraper frame; said suspension means including universal connection means and bowl lift arms mounted on opposite sides of said bowl; power lift means interconnected between said lift arms and said overhead superstructure; said suspension means further including frame arm means rigid with said superstructure and depending downwardly therefrom; and means including said universal connection means interconnecting said frame arm means and lift arms whereby said lift arms may undergo universal movements relative to said frame arms.

10. The scraper of claim 9 wherein said frame arm means comprise a pair of tow arms depending downwardly from said spaced frame members adjacent the forward end thereof.

11. The scraper of claim 9 wherein said frame arm means comprise a pair of push arms depending downwardly from said spaced frame members adjacent the rear end thereof.

12. The scraper of claim 10 wherein said frame arm means comprise a tow arm rigidly dependent from said superstructure and universally interconnected with a cross brace rigidly interconnecting the forward ends of said lift arms.

13. The scraper of claim 10 wherein said bowl lift arms are univerally mounted on said bowl whereby said bowl may undergo universal movements relative to said lift arms.

14. The scraper of claim 13 wherein said stabilizing means include stabilizing bracket means secured to the side walls of said bowl and defining elongate slots through which a portion of said lift arms extend for limiting said universal movements undergone by said bowl relative to said lift arms.

15. The scraper of claim 13 wherein said stabilizing means comprise a modified Watts linkage including a radius link centrally mounted for rotation on a pivot shaft rigid with said scraper frame and a pair of radius arms interconnecting opposite ends of said radius link with said lift arms.

16. The scraper of claim 13 wherein said stabilizing means comprise a spaced pair of stabilizing plates pivoted at one end thereof to said bowl and at the other ends thereof to opposite ends of spaced links for conjoint, parallel movement relative thereto; a cross shaft rigidly interconnecting said spaced links intermediate the opposite ends thereof; and a main link universally interconnecting said cross shaft and scraper frame whereby said stabilizing means may undergo universal movements with said bowl relative to said frame.

17. In a self-loading scraper having a mobile scraper frame defined by overhead superstructure bridging a rear traction unit and a forward wheel unit, the improvement comprising; said superstructure including transversely spaced frame members rigid with said rear traction unit; suspension means suspending a scraper bowl from said scraper frame substantially withiN the transverse confines of said spaced frame members for raising, lowering and canting said bowl relative to said frame members; stabilizing means positioned exteriorly of the peripheral confines of said bowl for limiting relative transverse movement between said bowl and scraper frame; said suspension means comprising a pair of bowl lift arms universally mounted intermediate the ends thereof on said bowl and universally interconnected adjacent respective opposite ends thereof, with bowl lift cylinders depending from said overhead superstructure and a pair of tow arms rigidly dependent from said spaced frame members.

18. The scraper of claim 17 wherein said pair of tow arms are rigidly dependent from the forward ends of said spaced frame members.

19. The scraper of claim 17 wherein said stabilizing means includes bracket means rigid with the side walls of said bowl for limiting transverse relative movement between said bowl and lift arms.

20. In a self-loading scraper having a mobile scraper frame defined by overhead superstructure bridging a rear traction unit and a forward wheel unit, the improvement comprising; said superstructure including transversely spaced frame members rigid with said rear traction unit; suspension means suspending a scraper bowl from said scraper frame substantially within the transverse confines of said spaced frame members for raising, lowering and canting said bowl relative to said frame members; stabilizing means positioned exteriorly of the peripheral confines of said bowl for limiting relative transverse movement between said bowl and scraper frame; power operated pitch control means interconnected between said scraper frame and bowl for selectively controlling bowl pitch; said power operated pitch control means comprising a parallelogram linkage universally carried by said scraper frame.

21. In a self-loading scraper having a mobile scraper frame defined by overhead superstructure bridging a rear traction unit and a forward wheel unit, the improvement comprising; said superstructure including transversely spaced frame members rigid with said rear traction unit; suspension means suspending a scraper bowl from said scraper frame substantially within the transverse confines of said spaced frame members for raising, lowering and canting said bowl relative to said longitudinally members; stabilizing means positioned exteriorly of the peripheral thereof confines of said bowl for limiting relative transverse movement between said bowl and scraper frame; said stabilizing means comprising link means intermediate said scraper frame and bowl for transferring lateral loading forces from said bowl to said frame; said link means including a radius link mounted intermediate the ends thereof for pivotal movement about an axis fixed with respect to a central portion of said scraper frame and extending generally longitudinal thereof; a pair of radius arms each having one end there of pivoted to opposite ends of said radius link and extending in opposite directions; and means including universal connection means interconnecting the other end of each said radius arm with said bowl.

22. The scraper of claim 21 wherein said suspension means include bowl lift arms on opposite sides of said bowl; and said last named universal connection means interconnecting said other end of each said radius arm with said bowl lift arms.

23. In a self-loading scraper having a mobile scraper frame defined by overhead superstructure bridging a rear traction unit and a forward wheel unit, the improvement comprising frame members rigid with said rear traction unit; suspension means suspending a scraper bowl from said scraper frame substantially within the transverse confines of said spaced frame members for raising, lowering and canting said bowl relative to said frame members; stabilizing means positioned exteriorly of the peripheral confines of said bowl for limiting relative transverse movement between said bowl and scraper frame; said stabilizing means comprisinG upper and lower stabilizing plates pivoted at opposite ends thereof to the rear of said bowl and a pair of spaced links; and means mounting said pair of spaced links on said scraper frame for universal movement relative thereto.

24. A self-loading scraper having a mobile scraper frame defined by central superstructure bridging an integrally connected rear traction unit and a forward steerable wheel unit; said superstructure including transversely spaced frame members; a scraper bowl positioned substantially within the transverse confines of said spaced frame members; bowl control means, including stabilizing means positioned exteriorly of said bowl for effecting a transverse interlock between said bowl and scraper frame for transmitting transverse working forces from said bowl to said spaced frame members and the traction unit; and said bowl control means further including suspension means, in addition to said stabilizing means, for raising, lowering and canting said bowl.

25. The scraper of claim 24 including power operated lift means interconnected between said scraper frame and bowl for raising and lowering the front end of said bowl; and power operated pitch control means interconnected between said scraper frame and bowl for selectively controlling the fore and aft orientation of said bowl.

26. A self-loading scraper having a mobile scraper frame defined by central superstructure bridging an integrally connected rear traction unit and a forward steerable wheel unit; said superstructure including transversely spaced frame members; suspension means suspending a scraper bowl from said scraper frame substantially within the transverse confines of said spaced frame members for movement relative thereto between upper carry and lower working positions; stabilizing means positioned exteriorly of said bowl for limiting relative transverse movement between said bowl and scraper frame; power operated lift means interconnected between said scraper frame and bowl for raising and lowering the front end of said bowl; power operated pitch control means interconnected between said scraper frame and bowl for selectively controlling the fore and aft orientation of said bowl; and said suspension means including bowl lift arms universally connected adjacent one end thereof with frame arms rigid with said spaced frame members and universally connected adjacent the other end thereof with said power operated lift means.

27. An earth moving scraper comprising: a mobile scraper frame defined by overhead superstructure bridging a rear traction unit and a forward wheel unit; said superstructure including transversely spaced frame members; bowl control means including suspension means suspending a scraper bowl having a scraper blade and a floor extending rearwardly therefrom substantially within the transverse confines of said spaced frame members for raising, lowering and canting said bowl relative to said frame members; said suspension means including a pair of arms extending substantially along the path of travel of the scraper on opposite sides of said bowl for coupling the bowl with the scraper frame; said suspension means further including power means coupled with the scraper frame and each of said arms for lowering and raising the bowl to and from an elevated earth carrying position and an earth scraping position wherein at least a part of the blade on said bowl engages the ground to cause earth scraped therefrom to be directed into the interior of the bowl and supported by the floor thereof; said bowl control means further including stabilizer means for effecting a transverse interlock between said scraper frame and bowl; and pitch control means interconnecting said bowl and scraper frame for maintaining the fore and aft attitude of the bowl floor in a plane parallel to the surface of the earth being worked when the bowl is in said earth scraping position.

28. An earth moving scraper as set forth in claim 27, wherein said power means is coupled with each of said arms at one of the ends of the latter and said pitch control means comprises extensible means coupled with said bowl at the end of the bowl opposite said one end of the arms, said extensible means being movable between retracted and extended positions in accordance with the lowering and raising of the bowl by said power means.

29. An earth moving scraper as set forth in claim 28, wherein said extensible means comprises a power cylinder positioned rearwardly of said bowl.

30. An earth moving scraper as set forth in claim 29, wherein said pitch control means includes a scissors linkage pivotally coupled with said bowl and scraper frame.

31. An earth moving scraper as set forth in claim 29 wherein said pitch control means includes parallelogram linkage pivotally coupled with said bowl and scraper frame.

32. An earth moving scraper as set forth in claim 28, wherein said arms extend fore and aft of the bowl and the latter is pivotally mounted on the arms at a point intermediate the ends of the arms.

33. An earth moving scraper comprising: a frame; a scraper bowl carried by the frame and having a scraper blade and a floor extending rearwardly therefrom; a pair of arms extending substantially along the path of travel of the scraper on opposite sides of said bowl for coupling the bowl with the frame; power means coupled with the frame and each of said arms for lowering and raising the bowl to and from an elevated earth carrying position and an earth scraping position wherein at least a part of the blade on said bowl engages the ground to cause earth scraped therefrom to be directed into the interior of the bowl and supported by the floor thereof; stabilizer means connected to the bowl for maintaining the fore and aft attitude of the floor thereof in a plane parallel to the surface of the earth being worked when the bowl is in said earth scraping position; said power means being coupled with each of said arms at one of the ends of the latter and said stabilizer means comprises extensible means coupled with said bowl at the end of the bowl opposite said one end of the arms, said extensible means being movable between retracted and extended positions in accordance with the lowering and raising of the bowl by said power means; said arms extending fore and aft of the bowl and the latter being pivotally mounted on the arms at a point intermediate the ends of the arms; and said arms being coupled with said frame through universal couplings and said power means being coupled with said arms and said frame through universal couplings.

34. An earth moving scraper as set forth in claim 32, wherein said stabilizer means includes structure on opposite sides of said bowl for restraining lateral movement of the bowl relative to the arms while permitting vertical movement of the bowl relative to the arms.

35. An earth moving scraper as set forth in claim 32, wherein said frame includes at least one depending leg, and each of said arms is supported at the other end by said leg.

36. An earth moving scraper as set forth in claim 35, wherein said leg depends from said frame forwardly of said bowl.

37. An earth moving scraper as set forth in claim 35, wherein said leg depends from said frame rearwardly of said bowl.

38. An earth moving scraper as set forth in claim 27, wherein said power means comprises a pair of individual power cylinders, one of which is coupled with each of said arms whereby said bowl is movable to a tilted position upon activation of one of said cylinders.

39. An earth moving scraper comprising: an overhead frame; a scraper bowl having a floor, said bowl being disposed beneath the frame and movable from an earth moving position to an earth scraping position wherein at least a leading edge of said bowl projecting from the floor thereof engages the earth being worked; fore and aft extending arms on opposite sides of said scraper bowl and coupled with the latter through universal coupling means; at least one depending leg on said frame for supPorting said arms at one end; individually operable power means coupled with the frame and each of said arms at the other end thereof for raising and lowering the bowl to and from said positions relative to the frame; and extensible means coupled with the scraper bowl and said frame and movable between retracted and extended positions in accordance with the lowering and raising of the bowl to maintain the fore and aft attitude of the floor thereof essentially parallel to the surface of the earth being worked when the bowl is in said earth scraping position.

40. An earth moving scraper as set forth in claim 29 wherein is provide a first link pivotally suspended from the frame rearwardly of the bowl, and a second link pivotally joined to the bowl and said power cylinder, said first link being pivotally connected to the second link intermediate the points of pivotal connection thereof to said bowl and the power cylinder.

41. An earth moving scraper as set forth in claim 39 wherein said power means and the extensible means are selectively operable to tilt the bowl in a fore and aft direction while the same is in a raised position thereof above the ground to facilitate dumping of earth from the bowl during unloading thereof.