US3690023A

US3690023A - Trencher-scraper machine

Info

Publication number: US3690023A
Application number: US3354A
Authority: US
Inventors: Carl Peterson
Original assignee: Foster Miller Inc
Current assignee: Vencore Services and Solutions Inc
Priority date: 1970-01-16
Filing date: 1970-01-16
Publication date: 1972-09-12
Anticipated expiration: 1989-09-12

Abstract

A method and apparatus for excavating earth with a vehicle having a wheel or endless chain to which is secured a plurality of excavation elements such as buckets or blades which excavate earth and also provide propulsion for the vehicle. The wheel or chain is supported from the vehicle frame so that the lowermost of the excavation elements engages and bites into the surface of the earth. The wheel or chain is driven in a direction which advances the vehicle forwardly with excavation elements providing the primary source of traction. The vehicle also includes a scraper blade which is located behind the wheel or chain. The leading edge of the scraper blade advances with the vehicle and cuts into the earth below the level of the excavation wheel chain to slice off a further layer of earth. The scraper blade, additionally, serves as a braking element to resist any tendency of the excavating wheel or chain to ride upwardly out of the excavated channel. The force of the excavated earth acting on the advancing scraper blade cooperates with the weight of the vehicle to maintain the excavating wheel or chain in the excavated channel. The vehicle is assisted by a powered tractor which is employed to provide any supplemental traction necessary to overcome any resistance presented by the earth to the advancing blade which cannot be overcome by the traction of the excavating wheel or chain alone. As the vehicle advances the excavation elements fill with earth and are moved along an endless path to a conveyor which receives the earth and transports it away from the vehicle. The excavation elements remove continually a substantial portion of the upper layer of earth and the scraper blade excavates the remaining portion of the earth.

Description

Peterson Sept. 12, 1972 [54} TRENCHER-SCRAPER MACHINE [72] Inventor: Carl Peterson, Boxford, Mass.

[73] Assignee: Foster-Miller Associates, Inc., Waltham, Mass.

[22] Filed: Jan. 16, 1970 [21] Appl. No.: 3,354

[52] US. Cl. ..37/90, 37/97, 37/108 R, 37/190, 37/192 R, 37/195 [51] Int. Cl. ..E02f 3/08, E02f 3/18 [58] Field of Search ..37/9, 8, 108, 189-192, 37/90, 97; 172/785, 122, 123

[56] References Cited UNITED STATES PATENTS 2,088,369 7/1937 Flynn ..37/190 X 84,230 11/1868 Stowell ..37/190 3,314,175 4/1967 Petty et a1 ..37/190 X 2,763,941 9/ 1956 Earley ..37/ 192 R X 1,985,188 12/1934 Miller ..37/9 3,316,664 5/ 1967 Wilmoth et a1. ..37/9 3,224,120 12/ 1965 Wilmoth et al. ..37/ 190 X 3,059,714 10/1962 Johnson ..37/8 UX 2,320,855 6/1943 Dukes ..37/DIG. 20 1,231,352 6/1917 Hickman, Jr. ..172/122 X 1,246,524 11/1917 Bager ..37/94 2,709,312 5/1955 Seifert ..37/190 2,896,342 7/1959 Reising ..37/97 969,187 9/1910 Poulter ..37/86 2,068,433 1/ 1937 Peterson ..172/785 X 854,894 5/1907 Jones ..172/785 FOREIGN PATENTS OR APPLICATIONS 137,833 10/1956 U.S.S.R. ..37/190 116,210 2/1958 U.S.S.R. ..37/9

Primary Examiner- Robert E. Pulfrey Assistant Examiner-Clifford D. Crowder Attorney-Wolf, Greenfield, l-lieken & Sacks [5 7] ABSTRACT v A method and apparatus for excavating earth with a vehicle having a wheel or endless chain to which is secured a plurality of excavation elements such as buckets or blades which excavate earth and also provide propulsion for the vehicle. The wheel or chain is supported from the vehicle frame so that the lowermost of the excavation elements engages and bites into the surface of the earth. The wheel or chain is driven in a direction which advances the vehicle forwardly with excavation elements providing the primary source of traction. The vehicle also includes a scraper blade which is located behind the wheel or chain. The leading edge of the scraper blade advances with the vehicle and cuts into the earth below the level of the excavation wheel chain to slice off a further,

layer of earth. The scraper blade, additionally, serves as a braking element to resist any tendency of the excavating wheel or chain to ride upwardly out of the excavated channel. The force of the excavated earth acting on the advancing scraper blade cooperates with the weight of the vehicle to maintain the excavating wheel or chain in the excavated channel. The vehicle is assisted by a powered tractor which is employed to provide any supplemental traction necessary to overcome any resistance presented by the earth to the advancing blade which cannot be overcome by the traction of the excavating wheel or chain alone. As the vehicle advances the excavation elements fill with earth and are moved along an endless path to a conveyor which receives the earth and transports it away from the vehicle. The excavation elements remove continually a substantial portion of the upper layer of earth and the scraper blade excavates the remaining portion of the earth.

17 Claims, 16 Drawing Figures PATENTEHsEP 12 I972 sax-1U 1 or 3 INVENTOR CARL R. PETERSON ATTORNEYS mtminsrm m2 3.690.023

saw a or 3 FIG. 4

i .5 FIG. l4

1 INVENTOR CARL R PETERSON 2/654 ywjwm m ATTORNEYS PATENYEDSEM m2 3.690.023

sum 3 or a Y aw a i 142" i FIG. 7

" lNVENTOR CARL R. PETERSON #Sadm ATTORNEYS 1 TRENCHER-SCRAPER MACHINE BACKGROUND OF THE INVENTION A number of machines have been proposed in the prior art for excavating earth. Among the more common of machines adapted to excavate large volumes of earth is a vehicle having a scraper blade which digs into the earth to slice off a layer of earth as the vehicle is driven forwardly. These machines are advanced along the earths surface by high powered tractors or bulldozers which must generate sufficient force and traction to draw the scraper blade through the earth. Additionally, because of the large forces required to force the scraper blade through" the earth nearly all of the machine components must be of massive construction in order to withstand the high loads which are developed. The requirement for high powered tractors or bulldozers to advance the scraper is necessitated by the relatively crude excavating technique which simply scrapes off a substantial thickness of the earths surface.

In order to overcome the disadvantages of scraper-- excavators, somemachines have been provided with rotary digging elements which mill through the earths surface to excavate the earth. These rotary excavators are advanced forwardly along the earths surface by tractors or bulldozers in much the same manner as the scraper-excavators referred to above. Additionally, these rotary excavators are rotated in a direction which tends to retard the forward advancement of the vehicle (the digging elements move forwardly through the earths surface during excavation). This presents substantial resistance to forward advancement of the vehicle. Because of the resistance to forward movement of the vehicle, high power tractors and bulldozers still are required.

Other excavating machines frequently include a bowl which receives the excavated earth directly from the scraper blade or rotary excavator. In most instances, the earth is pushed upwardly into the bowl through an opening formed in its bottom as the vehicle is advanced by the separate propelling unit such as a tractor. Such vehicles present a number of difficulties in that as the bowl fills up, a considerable and increasing resistance is presented to forward propulsion of the vehicle in that the earth must be loaded into the bowl from the bottom in opposition to the weight of the earth already in the bowl. In order to overcome this, some of these vehicles have been equipped with elevating devices to lift the earth and convey the earth to a location above the bowl from which it is dumped into the bowl. These elevators, however, serve no other function and do not aid in propelling the vehicle. The layer of earth is excavated off solely by the action of the scraper blade or rotary excavator. This limits the depth to which the blade may penetrate and, therefore, the thickness of the layer of earth which is removed. In the prior machines the thickness of the removed layer is dependent solely on the traction between the tractor and the earth. Additionally, the thickness of layer which these devices may remove also is limited by the speed of the elevator which transports the earth from the blade to the selfcontained bowl in the vehicle. Thus, even when the vehicle is assisted by supplemental tractors or bulldozers, its capacity is limited by the operational speed of the elevator.

Prior vehicles which include self-contained storage bowls and the elevators described above, essentially are a compromise between a hauling vehicle and an excavation vehicle. This necessarily detracts from the efficiency of the vehicle while performing either of its functions. For example, the size of the storage bowl and, therefore, the capacity of the vehicle as a truck is limited because the truck also must include the relatively bulky and heavy elevator. When used as a truck, the elevator serves no purpose and provides undesirable dead weight.

A further disadvantage of prior excavating machines resides in their bulky and heavy construction which is required to withstand the large forces which develop during the. excavating operation. Because of their heavy, bulky nature it is difficult to transport these machines from one construction site to another. Additionally, the heavy weight of these machines has been necessary in order to provide proper traction between the tractors and the earths surface and also to maintain the scraper blade or other digging device at its desired depth in the earths surface. The instant invention overcomes these disadvantages by employing a technique in which the excavating unit provides its own traction and in which the forces transmitted to the frame of the machine are minimized thus enabling the frame to be of less bulky construction.

SUMMARY OF THE INVENTION inherent in currently available and known earth excavators. In brief, the vehicle includes novel construction for excavating the earth which may be employed in a combined excavator-truck or, as preferred, in a vehicle used only for excavating which conveys the excavated material to a separate hauling truck which may remove the excavated earth from the site.

In one embodiment of the invention, the vehicle includes a frame which is pulled by a tractor and which supports a rotary excavator having a plurality of excavating elements, such as buckets, secured about its periphery. The frame is arranged to support the rotary excavator so that its buckets will project below the surface of the earth and will bite into the earth. Means are provided for controlling and adjusting the depth of penetration of the buckets into the earth. A scraper blade also is supported by the frame and is disposed just rearwardly of the rotary excavator to excavate further and scrape smoothly the earths surface behind the excavator. In contrast to prior rotary excavators, the instant excavator is driven in a direction which will tend to advance the vehicle forwardly instead of retarding forward movement. As the excavation buckets of the rotary excavator bite into the earth they loosen the earth and also provide substantial traction which propels the vehicle forwardly. The buckets which have penetrated the earth slip rearwardly as the vehicle advances, but still generate the necessary tractive force.

The traction provided by the rotary excavator is can trolled by varying the height of the excavator while maintaining the depth of the scraper blade constant. The traction of the excavator wheel is sufficient so that the excavator wheel will provide a substantial horizontal advancing force to propel the vehicle forwardly. In

addition, the excavating wheel may provide some of the force necessary to advance the scraper blade in a forward direction. The remaining force necessary to overcome the resistance of the earth presented to the scraper blade is provided by the tractor. The excavator wheel thus removes a substantial portion of the earths surface, so thatv the scraper blade only removes the remaining portion of the earths surface. Because the scraper blade does not remove the full layer of earth, the resistance of the earth to the scraper blade is less than in conventional machines. The propelling force which the tractor thus must generate is considerably less than the force required by tractors and bulldozers on conventional machines in which the full layer is excavated by the scraper blade.

As the vehicle advances forwardly the rotary excavator is driven continually so that earth trapped in its buckets or blades may be transported to a conveyor on the vehicle. The conveyor receives the excavated earth as it empties from the buckets and transports the excavated earth to a separate truck which moves alongside the excavating vehicle. This technique enables the excavating vehicle and truck to be used to their full capacity in a more efficient manner than a combined truck-excavator. Additionally, the construction employed in this excavating machine enables a relatively thick layer of earth to be removed with each pass of the vehicle thus affording a more economical operation as well as overcoming the difficulties presented in prior machines.

In another embodiment of the invention the excavating device may consist of an endless chain which is supported from the frame of the vehicle with the excavating buckets being secured to the chain. The chain is arranged to provide the same function as the rotary excavator described above in that the buckets penetrate into the earth to provide traction and to loosen the soil and thereafter to transport the soil to a conveyor which delivers the soil away from the excavating vehicle. This embodiment also includes a scraper blade which is supported behind the chain and which smoothes out the excavated surface behind the chain. The chain arrangement is preferred in very large vehicles in lieu of the rotary excavator which, in such vehicles, necessarily would be of extreme dimensions. A chain excavator of the same capacity can be mounted within a smaller space than the rotary conveyor.

An additional feature of the invention resides in the arrangement by which the excavator is supported from the frame of the machine which permits the excavator to be raised or lowered thus varying the depth to which its buckets or blades penetrate the earth. In addition to controlling the depth of penetration and, therefore, the thickness of layer removed by the excavator wheel or chain, the control mechanism for varying the height of the excavator also serves to control the balance of traction between the excavation elements and the tractor.

It is among the primary objects of the invention to provide an excavating machine in which the excavating member serves also to provide propulsion for the machine.

Also among the objects of the invention is to provide an excavating machine including a scraper blade in which a minimum of power is required to advance the scraper blade through the surface of the earth.

A further object of the invention is to provide an excavating machine having an excavating member and a scraper blade in which the excavating member removes a first portion of the earths surface while advancing in a direction tending to propel the vehicle forwardly and in which the scraper blade follows to remove the remaining layer of the earths surface.

Still another object of the invention is to provide an excavating machine including a scraper blade in which a horizontal propelling force is required to advance the scraper blade through the earth is minimized.

It is another object of the invention to provide an excavator which removes a layer of earth and conveys the removed earth to a location remote from the excavator.

It is a further object of the invention to provide an excavating machine which is capable of removing relatively thick layers of earth from the ground surface.

Yet another object of the invention isto provide an excavating vehicle which may remove large or thick layers of earth without requiring the assistance of supplemental high powered tractors or other drive mechanisms.

An additional object of the invention is to provide an excavating machine including a scraper adapted to scrape and smoothen the excavated surface and in which the earth to be scraped off initially is loosened before engagement thereof by the scraper to present less resistance to the scraper. The pre-softening of the soil also enables the excavating machine to be used in connection with relatively hardened earth which normally would present considerable resistance to advancement of a conventional scraping and excavating arrangement.

DESCRIPTION OF. THE DRAWINGS These and other objects and advantages of the invention will be apparent more fully from the following detailed description thereof with reference to the accompanying drawings wherein:

FIG. 1 is a somewhat schematic elevation of excavating machines constructed in accordance with the invention;

FIG. 2 is a plan view of the machine shown in FIG. 1;

FIG. 3 is a side elevation of a modification of the excavating machine in which the rear transport wheelsmay be varied in height;

FIG. 4 is a somewhat diagrammatic end view of the excavating machine illustrating the manner in which it may be employed to excavate a smooth horizontal surface on a hill or slope; I

FIG. 5 is an exploded view of a connection between a tractor and the main frame of the excavating machine;

FIG. 6 is an elevation of a modification of the excavator including an endless chain excavator unit;

FIG. 7 is a section through the endless chain excavator unit as viewed from the plane 7-7 of FIG. 6;

FIG. 8 is a side elevation of the scraper blade having projections secured thereto;

FIG. 9 is a sectional plan view of the scraper shown in FIG. 8 as viewed along the line 9-9 of FIG. 8;

FIG. 10 is a schematic illustration of the clearance between the rotary excavator and its associated scraper blade;

FIG. 11 is an illustration similar to that of FIG. 10 in which the scraper blade in contoured to parallel the locus of motion of the rotary excavator unit;

FIG. 12 is a schematic elevation similar to that of FIG. 11 in which the scraper blade is contoured tobe disposed in parallel to the locus of adjustment of the chain excavator;

FIG. 13 is a somewhat diagrammatic elevation of a modified scraper blade having forwardly projecting fingers;

FIG. 14 is a somewhat diagrammatic plan view of the structure shown in FIG. 13;

FIG. 15 is a'diagrammatic elevation of the machine with a modified conveyor; and

FIG. 16 is a plan view of the machine shown in FIG. 15.

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the machine, shown in FIGS. 1 and 2, includes a main frame consisting of a pair of overhead longitudinal rails 12 and rearward downwardly depending frame sections 14. Two or more trailing wheels 16 are rotatably mounted to the rear frame section 14 as by the axle l8-and may be powered or freely rotatable. The forward ends of the overhead rails 12 are pivoted to the frame of a tractor 22 about a vertical axis such as at the vertical pin 24 to facilitate steering. The vehicle is controlled by the operator who is located in the cab 26 atop the tractor. The tractor also, of course, includes an engine 28 which powers the vehicle.

The vehicle includes an excavation unit, indicated generally by the reference character 30, which is supported from the overhead rails 12 of the main frame. As shown in FIGS. 1 and 2 the excavation unit includes a plurality of rotary excavation wheels 32 which are arranged generally in lateral, spaced alignment with each other. Each of the excavation wheels 32 includes a plurality of buckets 34 secured circumferentially about the wheels 32. Each of the wheels 32 is driven, as described below in more detail, in a direction which will advance the vehicle forwardly (to the left as seen in FIG. 1). The buckets 34 are arranged about their associated wheels 32 so that as the wheels 32 are rotated (counter clockwise as seen in FIG. 1) the open faces of the buckets 34 will dig into, loosen and become filled with the earth but maintain traction on the soil. The traction thus obtained enables the excavation wheels 32 to be employed for driving the vehicle forwardly as well as to aid in the excavation process.

The excavation wheels 32 cooperate with a scraper blade 36 having a leading edge 38 which extends transversely of the vehicle. The scraper blade 36 is arranged in relation to the excavation wheels 32 so that its leading edge 38 penetrates into the earth to a greater depth than that of the buckets 34. Means are provided for adjusting the relative depth to which the excavation wheels 32 and scraper blade 36 penetrate the earth, and consequently, the relative thickness of the earths layer which is excavated by the excavation wheel and scraper blade. The heightwise adjustment capability of the excavation wheel 32 in relation to the scraper blade 36 also provides means for controlling the traction and forward propulsion of the machine while maintaining the blade 36 at a constant desired penetration level. The heightwise position of the excavation wheel 32 controls the balance of tractive effort which is developed by the tractor and the excavation wheel 32.

penetrates the earth. As the excavator wheel is raised the tractor will bear more of the vehicle weight and, therefore, can develop more traction. Under optimum operating conditions, the tractive force generated by the tractor is enough only to overcome the drag of the scraper blade 36, the remaining forward propulsion being generated by the excavator wheel 32. Because the scraper blade 36 cuts through a thinner layer of earth than prior machines excavating to the same depth, the forward tractive propulsion generated by the tractor need not be as great as the propulsion which normally would be required. This avoids the use of supplemental bulldozers or multiple tractors, as in the prior art. Thus, in operating the machine, the depth of penetration of the scraper blade 36 is set to the desired excavation depth. The height of the excavation wheels 32 then are adjusted to a level at which they will provide sufficient horizontal forward traction which will permit theztractor to supply the remaining horizontal force necessary to overcome the drag and resistance of the earth to the scraper blade 36. As the machine advances, the power of the tractor may be varied by the operator to overcome obstacles such as rocks, stumps, ets.

As the excavation wheels 32 rotate, they tend continually to rise upwardly and out of the excavated channel. The excavation wheels 32 are maintained in the channel by the weight of the vehicle and also by the action of the scraper blade 36 which tends to wedge into the earth, thus imparting a downwardly directed component of force to the frame of the machine through the scraper blade. The magnitude of this force is dependent on a number of factors such as the location of the scraper blade with respect to the excavation wheels, the characteristics of the earth being excavated, the extent to which the excavation wheels have loosened the soil through which the excavation blade passes and the angle at which the leading edge 38 of the 'blade 36 meets the earth. The scraper blade also provides a reaction surface against which the excavation wheels 32 may load or throw any earth which they have not scooped up in the buckets. Additionally, the scraper blade 36 assists substantially the excavation operation and finally smoothes out the excavated surface left behind. The relative portions of the excavated layer which are removed by the excavating wheels and the blades may be varied as the height of the excavating wheel 32 is varied, In some instances, the excavating wheel may project only half way through the intended excavation depth with the excavating blade 36 being positioned at the full depth. Under other operating conditions, the excavation wheel 32' will be spaced more closely to the excavation blade. Because the scraper blade 36 digs into soil which has been loosened somewhat by the excavation wheels 32, the resistance which the earth presents to the scraper blade 36. as it advances may vary. Both the excavation wheels 32 and the scraper blade 36 are supported from the frame 10 for heightwise adjustment to control the depth of cut as well as for retracting these units upwardly out of the way when the vehicle is used on the road or highway.

In the embodiment shown in FIGS. 1 and 2 each of the excavation wheels 32 is supported on a wheel frame 40, each wheel frame 40 having a number of supporting rollers 42 joumaled at spaced locations about the wheel frame 40. The rollers 42 on each wheel frame 40 engage the inner cylindrical surfaces 44 of their associated excavation wheel 32 to support and guide the excavation wheels 32 for rotation about a fixed transverse axis. Each of the wheel frames 40 is arranged in transverse alignment so that the respective excavation wheels 32 also will be arranged in transverse alignment. The wheel frames 40 are secured to and supported by a transverse frame 46 which extends transversely across the vehicle and through each of the excavation wheels 32.

The transverse frame 46 and wheel frames 40 are suspended from the overhead rails 12 of the main frame by laterally spaced pivot arms 48 which embrace the overhead rails 12 and which are pivoted at one end to the lateral ends of pins fastened to the frame 10. The pivot arms 48 extend rearwardly and downwardly from the pins 20 toward he transverse frame 46 to which the pivot arms 48 are rigidly fastened.

The rearward end of the excavation unit 30 is supported by a pair of fluid operated cylinders 50 which are pivoted to the overhead rails 12 and which have downwardly extending piston rods 52 which are pivoted, at their lower ends, to the transverse frame 46. In addition to supporting the excavation unit, the arrangement of pivot arms 48 and fluid cylinders 50 permit the height of the excavation wheels 32 to be controlled by the operator. The fluid operated cylinders 50 may be actuated to swing the excavation unit and pivot arms 48 about the pivot 20 to the desired heightwise position. As shown in FIG. 2 the'overhead rails 12 may be disposed along the space between adjacent excavation wheels 32 so that when raised to their uppermost position the excavation wheels 32 project upwardly through and beyond the overhead rails 12.

When raising or lowering the excavation wheels 32 it may be necessary to raise or lower the scraper 36 therewith. As shown, the scraper is fastened to a slide 54 which, in turn, slides along a guiding surface 56 formed on the rear frame section 14. The heightwise movement of the slide 54 and scraper 36 along the guiding surface 56 is controlled by fluid operated cylinders 58 which are pivoted at one end to the overhead longitudinal rails 12 and which have downwardly extending piston rods 60 which are connected to the slide 54. Thus, by controlling the

cylinders

50 and 58 the height of both the excavation wheels 32 and scraper 36 may be controlled relative to the frame of the vehicle and relative to each other.

A number of arrangements may be provided for driving the excavation wheels 32. A suggested arrangement is shown in the drawings and includes a number of gear teeth 62 arranged circumferentially about the lateral surfaces of each of the excavation wheels 32. The teeth 62 are enmeshed with pinion gears 64 which are rotatably mounted to the wheel frame 40. Each of the pinion gears is driven by achain 66 which, in turn, is driven by a driving gear; 68.Each driving gear 68 is fastened to a transversely extending excavator drive shaft which is powered by the independent motors 72. The laterally outward chains 66 and associated

gears

64, 68 may be contained within the hollow pivot arms 48. The shaft 70 is journaled, at its ends, to the pivot arms and the motors 72 are secured to the pivot arms and connected to the shaft 70. The motors 72 may be controlled by the operator to regulate the rotary speed of the excavation wheels 32.

The invention also includes an arrangement for transporting the excavated earth from the buckets 34 to a location remote from the excavation vehicle such as to a hauling truck to transport the excavated earth to a different location. For this purpose, the excavator includes a conveyor supported on the transverse frame 46 and which extends through and transversely of the excavation wheels 32. The conveyor indicated generally by reference character 74 protrudes laterally and outwardly of the ends of the most lateral excavation wheels 32. The conveyor 74 may be of generally conventional design having a plurality of rollers 76 which support and guide a flexible conveyor belt 78. The conveyor 74 may be driven in either direction and preferably is driven by a reversible motor. During operation as the excavation wheels 32 rotate, the earthfilled buckets 34 are rotated to a position above the conveyor 74. When in this position the buckets 34 begin to empty downwardly with the earth falling onto the conveyor. The conveyor preferably is provided with receiving plates 80 which extend along and on either side of the conveyor to collect all of the earth falling from the buckets 34 as they discharge. The conveyor then transports the earth laterally toward and away from the machine.

In a modified version of the excavating vehicle, it

may be preferable to eliminate the sliding, movable 1 construction of the scraper blade 36 and secure the scraper blade 36 directly to the frame in order to transmit more effectively the forces between the scraper blade and the main frame.

FIG. 3 shows a modification of the vehicle in which the scraper blade 36' is fastened rigidly to the main frame. The excavation wheels 32 are mounted and supported from the frame in the same manner as in the embodiment as shown in FIG. 1. In this embodiment, the scraper blade 36 is raised and lowered in unison with the main frame to which it is attached. This action is provided by mounting the trailing wheels 16 to connecting links 84 which are pivoted to the rear frame section 86 at the pin 88. The pivotal position of the connecting links 84 is controlled by a pair of fluid operated cylinders 90 which are pivoted at their upper ends to the upper portion of the rear frame section 86 and which have piston rods 92 pivotally connected at the pins 94 to the outer end of the connecting links 84. The cylinders 90 are controllable to pivot the wheels 16 from the position shown in solid in FIG. 3 to the position shown in phantom and indicated generally by the reference character 96. In operation, the cylinder 90 is operated to control the height of the frame 10 and, therefore, simultaneously control the level of the scraper blade 36 and excavation wheels 32.

A further advantage of the arrangement is that by operating the cylinders 90, both the scraper blade 36 and excavation wheels 32 are raised or lowered simultaneously and in unison which avoids the necessity of readjusting one of these parts relative to the other after one of the parts has been shifted in position. The relative disposition between the excavation wheels 32 and the blade may be controlled separately by the fluid operated cylinder 50 which connects the main frame to the transverse frame of the excavating unit in the same manner described above.

The cylinders 90 may be operated in unison or independently of each other. This enables the wheels 16 to be maintained at the same or at different elevations with respect to the frame 10. The advantage in this arrangement is shown somewhat diagrammatically in FIG. 4 which illustrates the vehicle as used to excavate and scrape a flat horizontal surface on the side of a hill or other sloping terrain. As shown in FIG. 4, the tractor 22 is driven along the side of the hill and is disposed in a position which is inclined to the vertical. The main frame, however, which follows the tractor is maintained in a generally vertical upright position so that the excavation unit 30 and scraper blade 36 remain in a level, horizontal configuration. The main frame 10 is pivoted to the tractor about a longitudinal axis topermit such relative angular orientation. The main frame is supported in this position by controlling the position of the wheels 16 by the fluid cylinders 90 so that the uphill of the wheels 16 is raised in relation to the downhill of the wheels 16. As the vehicle advances forwardly it excavates a portion of the hillside and leaves the excavated portion flat and horizontal. The vehicle advances along the hill in this configuration until the trailing wheels 16 advance to the flat and level excavated portion. The cylinders 90 then are operated to return the wheels 16 to the same horizontal position so that the excavation unit is maintained in its generally vertical disposition as the wheels 16 then follow behind on the flat, excavated portion of the earth.

When the vehicle shown in FIG. 3 is transported along the road, the cylinders 90 are actuated to swing the wheels 16 downwardly fully to the position shown in phantom at 96. This effectively raises the frame and excavating unit above the road level to provide sufficient road clearance for the frame and its supported parts. Additionally, the wheelbase of the vehicle is reduced which enhances somewhat the maneuverability on the road.

FIG. shows an exploded arrangement of the joint between the main frame and the tractor which permits the tractor 22 and frame 10 to be pivoted with respect to each other about a vertical axis for steering, and about a horizontally axis to enable the tractor and frame 10 to assume different upright attitudes as when used on the sides of hills and the like. The connection joint may include a vertical socket 98 formed in the frame of the tractor 22. The socket 98 receives the lower pin 100 of a T-shaped connector 102. The connector 102 also has a pair of horizontally extending pins 104 which intersect and are perpendicular to the lower pin 100. The pins 104 are received within longitudinally spaced bearing plates 106 which are secured to the forward end of the main frame 10. The pins 20, which support the pivot arms 48 are secured and extend laterally from the main frame 10 in the region of this swivel joint.

A further embodiment of the invention is shown in FIGS. 6 and 7 and is substantially identical to that described above except that the rotary excavation wheels 32 are replaced by endless excavation chains, indicated generally at 108. A number of such endless excavation chains 108 are arranged in pairs transversely of the vehicle in the same manner as-the arrangement of excavation wheels 32 described above. Each of the excavation chain pairs is supported by an L-shaped chain frame 110. Three sprockets 112,114, and 116 are rotatably mounted on the chain frame 10 at its free ends and at its bent portion, the excavation chains 108 being wrapped endlessly about the

sprockets

112, 114' and 116. A number of buckets 118 are secured to the outer periphery of each pair of chains for the same purpose as the buckets 34 on the rotary excavation unit 30 described above. The buckets 118 preferable include a number of forwardly projecting teeth 120 and are arranged so that when the chains 108 are driven in an excavating direction (counter clockwise as seen in FIG. 6) the lower of the buckets l 18 which are located along the bottom run of the chains 108 face rearwardly to penetrate'through the soil and fill the buckets 118. The lower run of the chains 108 extends along the lower leg 122 of the L-shaped chain frame 110 and is defined by that portion of the chain 108 which extends across the lower sprockets 1 14, l 16.

The. chain excavation unit is suspended from the chain frame 10 by a pair of pivot arms 124 which are pivoted at their upper ends, to the overhead rails 12 at the pins 126. The forwardlyand downwardly extending ends of the pivot arm 124 are pivoted to the forwardly extending end of the lower leg 122 of the L-shaped chain frame 110. The pivot arms.l24 and the forward ends of the frame 110 and chain excavator unit are raised or lowered by a pair of fluid operated cylinders 128 which are pivoted to the overhead rails 12 of the frame at the pins 130 and which have downwardly extending piston rods 132 which are pivotally connected to the forward lower ends of the pivot arms 124. The cylinders 128 are operative to raise or lower the forward end of the chain frame 1 10.

The rearward end of the chain excavation unit is supported adjustably by a pair of fluid operated cylinders 134 which are pivotally connected between the overhead rails 12 of the frame 10 and the upper portion of the chain frame 110 near the sprocket 114. The rear-- ward cylinders 134 are adjusted primarily to control traction and depth of penetration of the chain excavator- The forward cylinders 128 are useful primarily to raise the forward end of the chain excavator above ground level when the vehicle is transported over the road. In some instances, however, it may not be necessary to raise the forward end of the chain excavator andthe cylinder 128 may be replaced with a rigid structural member. This, however, depends on the dimensions and particular structural characteristics of the machine.

The drive for the excavator chain 108 preferably is taken from an independent motor and is transmitted to the chain through the upper sprockets 112. The motor (not shown) may be secured to one of the L-shaped. ex.- cavator frames or to the transverse frame 136 which extends across all of the chain frames 110 and secures the chain frames in registration with eachother. The

I 136 and operates in the same manner as the conveyor 74 described above in connection with the rotary excavation unit 30.

FIG. 7 shows, in section, the pattern which the excavation chains 108 or excavation wheels 32 make as they advance through the upper layer of the earth. This pattern consists of a number of parallel channels 150 separated by earth walls 152. The buckets thus remove a substantial portion of the material to be excavated. The scraper blade 36, which follows the buckets, advances along the plane 154. The material excavated by the blade thus includes a lower layer of earth together with the walls 152 and other earth not picked up by the buckets. The thickness of the lower layer is, of course, dependent on the relative heightwise setting between the excavation buckets and the leading edge of the scraper blade 36. When the lower level is relatively thin, the resistance of the earth to the advancing edge of the scraper blade 36 is relatively small. In addition, the resistance maybe reduced further if the earth has been loosened substantially by the excavating unit. Even when the lower layer of earth presented to the scraper blade 36 is relatively thick, however, this layer still is less thick than the layer which normally is presented to conventional scraping or excavating machines in which the scraper performs the primary excavating operation. In these prior machines, the resistance of the earth to the scraper is considerable. In contrast, the lower resistance presented to the advancing scraper enables the use of a tractor with less power to advance the vehicle. The power which the tractor must generate is lessened further by reason of the traction generated by the excavation unit, which during optimum conditions of operation, generates a sufficient tractive force to overcome at least a portion of the drag on the scraper blade.

In each of the foregoing embodiments of the invention, the blades or buckets excavate a number of parallel but closely spaced channels in the earth, the channels being separated by thin walls of earth. It is, of course, desirable to fill the buckets completely for efficient excavation. In order to insure that the buckets are filled completely, projections as shown in FIGS. 8 and 9 may be formed on the scraper blade 36. The projections 156 preferably are arranged to be disposed alternately between the excavating wheels or chains to engage and urge the unexcavated walls 152 sideways into the buckets. The projections may be V-shaped either of symmetrical or unsymmetrical cross section or other contour designed to break down the earth walls and direct the earth laterally toward and into the buckets.

In some instances, a machine constructed in accordance with the invention may be employed to excavate relatively deep trenches by passing the machine over the excavated area a number of times. The depth of the trench may be such that the transverse conveyor 74 is disposed below the level of the earths surface, 166 as shown in FIG. 15, and cannot, by itself, carry the excavated earth to a remote location. When the machine is used to excavate such relatively deep trenches the conveyor should be modified as shown in FIGS. 15 and 16 so that it directs and transports the earth inwardly through the excavation units 32to a central conveyor 168 which extends forwardly and then upwardly above the level of the earth's surface 166. The conveyor 168 may include a transversely extending portion 170 to remove the earth toa separate hauling vehicle. This technique may be modified to include any number of forwardly extending conveyors 168 disposed between adjacent selected wheels 32 or excavation chains.

Each embodiment of the invention described thus far includes a mechanism which permits continuous relative heightwise adjustment of the excavating unit in relation to the scraper blade 36 and also continuous heightwise adjustment of the excavation unit and scraper blade in unison in relation to the frame and, therefore, the surface to be excavated. FIG. 10 shows, somewhat diagrammatically, the most simple of the arrangements between the excavating unit and its associated scraper blade in which a relatively large clearance is provided between the unit and its blade so that there will be no interference throughout the full range of relative movement between these parts. FIG. 11 shows an arrangement by which the scraper blade 36 is of a special shape which parallels closely the locus defined by the excavator wheel 32 as it is moved to various adjusted positions. F IG. 12 shows a similar arrangement in which clearance is provided between the scraper blade and the chain excavator. In this arrangement a contoured chain guide 162 is provided between the

sprockets

112, 114 to support and guide the run of chain between the sprockets in a generally circular path about the sprocket 116. The scraper blade 36 is arranged in generally concentric relation to the chain guard. The chain excavator is pivoted to a raised or lowered position about the axis of the sprocket 116 to vary the depth of excavator penetration and scraper blade penetration.

Operation of the machine involves controlled cooperation between the

transport wheels

16, 23 and the chain or rotary excavation unit to vary the height of the excavation unit in relation to the frame and, therefore, in relation to the surface of the earth. As described above, the heightwise position of the excavation unit determines the balance of weight distribution between the

transport wheels

16, 23 and the excavation unit, the optimum balance being determined in part by the composition and consistency of the earth being excavated. The heightwise position of the excavation unit may be varied between an upper position in which the full weight of the vehicle is borne by the transport out of the excavated region. The balance shouldbe such that the primary forward advancing force of the vehicle is developed by the excavation unit with the tractor wheels 23 providing supplemental assistance I only to overcome the drag ofthe scraper blade.

A very substantial excavating operation thus is performedv by the buckets or other excavating elements which fill with earth and then transport the earth to the conveyor which transports the excavated earth to a remote location. The excavating operation is finished by the following scraper blade 36 which is disposed below the level excavated by the excavation unit. The scraper blade acts as a brake in opposition to the force of the excavation unit, providing a wall for the rotating or advancing excavation elements to load against and also preventing rearward spillage of excavated earth. The blade also excavates further to smooth out the excavated surface left behind. Depending on the digging action and penetration of the excavating elements, the scraper blade may advance through relatively loose soil which presents little resistance to the advancing scraper blade. This is in direct contrast to prior excavators in which the advancing scraper blade digs directly into firm, packed soil. Indeed, this is one of the limiting factors in such prior devices which requires supplemental powered units such as bulldozers to provide the necessary driving force for the blade.

In some instances, it may be desirable to provide additional means for increasing the downwardly directed force component of the machine to insure further that the excavating unit does not tend to climb forwardly out of the excavated channel. Any tendency for the excavator unit to climb out of its channel will tend to raise the'wheels 23 of the tractor 22, thus reducing the tractive effort of the wheels 23 and possibly even raising the wheels 23 completely off the ground. A further hold-down force may be generated by modifying the scraper blade, as shown in FIGS. 13 and 14, to include a number of forwardly extending fingers 162 which project forwardly from the edge of the scraper blade. The fingers 162 are spaced laterally of the scraper blade and are disposed between adjacent excavator wheels 32 or excavator chain pairs 108. The forward ends of these projections extend into relatively firm soil which has not yet been loosened substantially by the advancing buckets of the excavating unit. Additionally, the forward ends 164 of these projections are formed in a wedge-like incline so that their advancement will generate a downwardly directed force to the blade and the frame to which the blade is secured. The wedge surface 164 may be relatively shallow or may extend over a considerable area. By generating downwardly directed forces in response to advancement of the unit instead of merely holding the unit down by the bulk weight of the machine a more efficient and lighter machine may be produced.

Thus, I have provided an improved method and apparatus for excavating the surface of the earth which eliminates the relatively large thrust heretofore required with conventional scraping excavators. Moreover, these objectives are achieved by the use of a forwardly rotating excavating unit which both excavates and provides tractive force. The excavation unit cooperates with a scraper blade which brakes the opposing force of the excavation unit, provides a wall for the reverse rotation excavating unit .to load against and, in addition, further excavates and smoothens out the region left behind.

The heightwise positions of the excavation unit and scraper blade are adjustable in unison and with respect to eachother to permit the balance of traction between the excavation unit and the tractor to be controlled; The technique and apparatus avoids the necessity for supplemental power such as other bulldozers or tractors to overcome the heretofore 'high resistance of the earthto the scraper unit.

It should be understood that the foregoing description of my invention is intended merely to be illustrative thereof and that other embodiments and modifications will be apparent tothose skilled in theart without departing from its spirit. For example, although the invention has been described primarily as employed in a the machine intended for excavationalone it may be incorporated into a combined excavating-hauling 'vehicle, if desired. Although such a combination tends to reduce the general efficiency of the machine as an excavating unit because it necessarily is a compromise between a hauling and excavating vehicle, the excavating function of the vehicle is more efficient than currently available and known combined excavation-hauling vehicles. Further modifications may relate to the arrangement for heightwise movement on the frame. Additionally, although the transport means has been illustrated as comprising regular road wheels, chain-like endless tracks could be substituted although such tracks would not be as suitable for road use.

Having thus described the invention, what I desire to claimand secure by Letters Patent is:

l. A surface excavating machine comprising: a main frame, transport means for enabling saidframe to advance along the earths surface, excavating means including a plurality of excavating elements supported on said frame for movement along an endless path, means mounting said excavating means on said frame to enable a portion of said endless path to' intersect the surface of the earth when said vehicle is disposed on said surface to cause said excavating elements to penetrate the earths surface to a selected depth at which said elements may provide traction along the earths surface; drive means for moving said excavating elements in endless sequence along said endless path and in a direction which tends to advance said machine'forwardly when said excavating elements are in engagement with the earth s surface; said excavating elements being so constructed and arranged as to entrap a volume of earth and thereafter carry said volume of earth along said endless path to a location remote from said ex.- cavated surface to enable said entrapped volume of earth to be discharged from saidexcavating elements; and blade means supported by said mainframe, for engaging and penetrating the earths surface below the penetration depth. of said excavating means, said blade means being mounted tosaid frameand being constructed to present a forwardly and downwardly inclined surface to the earth thereby to generate a downwardly directed force in response to forward advancement of said machine thereby maintaining said excavating means in continuous penetrating relation to the surface of the earth and precluding said excavating means from 5 climbing out of the excavated region.

2. An apparatus as defined in claim 1 wherein the weight of said machine is distributed between said transport means and said excavating means, said apparatus further comprising:

means mounting said excavating means to said frame for adjustable movement heightwise of said frame, said transport means and said blade means whereby the weight borne by said excavating means may be varied to control the balance of traction between said excavating means and said transport means to preclude said excavating means from climbing forwardly out of the excavated region.

3. An apparatus as defined in claim 2 wherein said blade means further comprises:

a scraper blade mounted to said frame rearwardly of said excavating unit and having a blade edge disposed below the level of said excavating unit.

4. An apparatus as defined in claim 3 wherein said transport means includes powered tractor means connect'ed to said frame for assisting in forward advancement of the machine.

5. An apparatus as defined in claim 3 wherein said scraper blade is disposed in proximity to the excavating means toprovide a reaction surface for earth thrown rearwardly by said excavation means to assist in self m ntsloading of said excavation means and to provide said 12. An apparatus as defined in claim 11 wherein said hold-down force as said machine advances forwardly. 3 finger means includes reaction surfaces disposed at an 6. An apparatus as defined in claim 3 wherein said angle to the direction of advancement of said blade scraper blade is mounted for heightwise adjustable means to increase further the downwardly directed movement on said frame whereby the excavation depth component of force generated by said blade means. of said scraper blade and the downwardly directed 13. An apparatus as defined in claim 1 further comforce generated thereby may be controlled simultaneprising: ously. conveyor means mounted. to said frame to receive 7. An apparatus as defined in claim 6 wherein said earth discharged from said excavating elements, scraper blade and said excavation means are mounted said conveyor means extending transversely for heightwise adjustment in unison and in relation to through the center of said machine and thereafter 10. An apparatus as defined in claim 1 further comprising:

a plurality of said excavating means mounted in a gang in transversely spaced relation on said frame and in substantially transverse registry;

each of said excavating means being rotatably supported about a support frame, each of said support frames being secured to a transverse frame extending transversely of the main frame of said machine, said transverse frame being supported from said main frame of said machine;

said blade means having a blade edge disposed rearwardly of and below the level of said gang of said excavating means to excavate an additional layer of earth and to smoothen the excavated surface left behind; and

projection means secured to said blade means and extending forwardly between adjacent excavating means in said gang to divert earth transversely toward and into the excavation elements on said excavation means.

11. An apparatus as defined in claim l.further comprising:

said blade means being mounted to said frame rearwardly of said excavating means and having a blade edge disposed below the level of said excavating means, and

forwardly projecting finger means secured to said blade and extending forwardly of said edge thereof to engage and loosen relatively firm soil which has not yet been engaged fully by said excavating eleeach other. extending upwardly whereby when said earth 8. An apparatus as defined in claim 1 further comreceiving portion of said conveyor means is prising: disposed below the level of the earths surface said means mounting said excavating means to said frame for adjustable movement heightwise of said frame and said transport means whereby the weight of said machine borne by said excavating means may be varied to vary the traction of said excavating means said means mounting said excavation means for said movement comprising:

pivot arm means pivoted adjacent one end to said frame and having the other, free end thereof con nected to said excavation means; and

adjustable drive means operatively connecting said other end of said pivot arm means to said frame to upwardly extending portion of said conveyor means may transport said excavated earth to a location remote from said machine and out of said excavated region.

14. A method of excavating a surface layer of earth with an excavating machine comprising:

providing a plurality of excavating elements arranged in an endless sequence which excavating elements are adapted to entrap a volume of earth;

supporting a portion of the weight of said excavating machine by mobility means resting on said earths surface and being adapted to permit said machine ments, said conveyor means being adapted to receive and transport discharged earth to a remote location.

raise and lower said free end of said arm. to advance and be transported along the earths 9. An apparatus as defined in claim 1 further comsurface; prising: advancing said endless series of excavating elements conveyor means mounted to said frame to receive along an endless path to cause said excavating elesaid earth discharged from said excavating elements to dig into and to penetrate the earths surface, said penetration being effective both to provide traction for said machine and to fill said excavating units with earth;

controlling the balance of weight bearing on said excavating elements and said mobility means thereby to control the traction of said excavating elements through said earth, said traction being controlled to advance said machine forwardly while excavating said earth entrapped within said excavation elements; and

engaging the earth with a blade means below the penetration depth of said excavation elements and in a attitude which presents a forwardly and downwardly inclined surface to the earth to generate a downwardly directed force in addition to that caused by the weight of said machine in response to forward advancement of said machine.

15. A method as defined in claim 14 further comprismg:

locating said blade means in proximity to said excavation elements to assist self-loading of said excavation elements.

16. A method as defined in claim 15 wherein said step of controlling the balance of weight borne by said transport means and said excavation means comprises:

varying the relative height between said excavation elements and said mobility means.

17. A method of excavating earth from the earth's surface comprising:

positioning a scraper blade so as to provide a forwardly and downwardly inclined surface in penetrating relation to the earths surface and at a predetermined penetration depth;

providing a plurality of excavating elements arranged in an endless sequence, said excavating elements being adapted to entrap a volume of earth;

locating said excavating elements in a position to penetrate the earth's surface in advance of said scraper blade and at a lesser penetration depth than said scraper blade, whereby said excavating elements and scraper blade may be advanced so providing a supplemental power traction means connected to said machine for providing additional forward tractive effort, said additional forward tractive effort being of a magnitude sufficient-to overcome the forward resistance of the earth presented to the scraper blade which is not overcome by the forward propulsion of said excavating elements.

Claims

1. A surface excavating machine comprising: a main frame, transport means for enabling said frame to advance along the earth''s surface, excavating means including a plurality of excavating elements supported on said frame for movement along an endless path, means mounting said excavating means on said frame to enable a portion of said endless path to intersect the surface of the earth when said vehicle is disposed on said surface to cause said excavating elements to penetrate the earth''s surface to a selected depth at which said elements may provide traction along the earth''s surface; drive means for moving said excavating elements in endless sequence along said endless path and in a direction which tends to advance said machine forwardly when said excavating elements are in engagement with the earth''s surface; said excavating elements being so constructed and arranged as to entrap a volume of earth and thereafter carry said volume of earth along said endless path to a location remote from said excavated surface to enable said entrapped volume of earth to be discharged from said excavating elements; and blade means supported by said main frame, for engaging and penetrating the earth''s surface below the penetration depth of said excavating means, said blade means being mounted to said frame and being constructed to present a forwardly and downwardly inclined surface to the earth thereby to generate a downwardly directed force in response to forward advancement of said machine thereby maintaining said excavating means in continuous penetrating relation to the surface of the earth and precluding said excavating means from climbing out of the excavated region.

2. An apparatus as defined in claim 1 wherein the weight of said machine is distributed between said transport means and said excavating means, said apparatus further comprising: means mounting said excavating means to said frame for adjustable movement heightwise of said frame, said transport means and said blade means whereby the weight borne by said excavating means may be varied to control the balance of traction between said excavating means and said transport means to preclude said excavating means from climbing forwardly out of the excavated region.

3. An apparatus as defined in claim 2 wherein said blade means further comprises: a scraper blade mounted to said frame rearwardly of said excavating unit and having a blade edge disposed below the level of said excavating unit.

4. An apparatus as defined in claim 3 wherein said transport means includes powered tractor means connected to said frame for assisting in forward advancement of the machine.

5. An apparatus as defined in claim 3 wherein said scraper blade is disposed in proximity to the excavating means to provide a reaction surface for earth thrown rearwardly by said excavation means to assist in self loading of said excavation means and to provide said hold-down force as said machine advances forwardly.

6. An apparatus as defined in claim 3 wherein said scraper blade is mounted for heightwise adjustable movement on said frame whereby the excavation depth of said scraper blade and the downwardly directed force generated thereby may be controlled simultaneously.

7. An apparatus as defined in claim 6 wherein said scraper blade and said excavation means are mounted for heightwise adjustment in unison and in relation to each other.

8. An apparatus as defined in claim 1 further comprising: means mounting said excavating means to said frame for adjustable movement heightwise of said frame and said transport means whereby the weight of said machine borne by said excavating means may be varied to vary the traction of said excavating means said means mounting said excavation means for said movement comprising: pivot arm Means pivoted adjacent one end to said frame and having the other, free end thereof connected to said excavation means; and adjustable drive means operatively connecting said other end of said pivot arm means to said frame to raise and lower said free end of said arm.

9. An apparatus as defined in claim 1 further comprising: conveyor means mounted to said frame to receive said earth discharged from said excavating elements, said conveyor means being adapted to receive and transport discharged earth to a remote location.

10. An apparatus as defined in claim 1 further comprising: a plurality of said excavating means mounted in a gang in transversely spaced relation on said frame and in substantially transverse registry; each of said excavating means being rotatably supported about a support frame, each of said support frames being secured to a transverse frame extending transversely of the main frame of said machine, said transverse frame being supported from said main frame of said machine; said blade means having a blade edge disposed rearwardly of and below the level of said gang of said excavating means to excavate an additional layer of earth and to smoothen the excavated surface left behind; and projection means secured to said blade means and extending forwardly between adjacent excavating means in said gang to divert earth transversely toward and into the excavation elements on said excavation means.

11. An apparatus as defined in claim 1 further comprising: said blade means being mounted to said frame rearwardly of said excavating means and having a blade edge disposed below the level of said excavating means, and forwardly projecting finger means secured to said blade and extending forwardly of said edge thereof to engage and loosen relatively firm soil which has not yet been engaged fully by said excavating elements.

12. An apparatus as defined in claim 11 wherein said finger means includes reaction surfaces disposed at an angle to the direction of advancement of said blade means to increase further the downwardly directed component of force generated by said blade means.

13. An apparatus as defined in claim 1 further comprising: conveyor means mounted to said frame to receive earth discharged from said excavating elements, said conveyor means extending transversely through the center of said machine and thereafter extending upwardly whereby when said earth receiving portion of said conveyor means is disposed below the level of the earth''s surface said upwardly extending portion of said conveyor means may transport said excavated earth to a location remote from said machine and out of said excavated region.

14. A method of excavating a surface layer of earth with an excavating machine comprising: providing a plurality of excavating elements arranged in an endless sequence which excavating elements are adapted to entrap a volume of earth; supporting a portion of the weight of said excavating machine by mobility means resting on said earth''s surface and being adapted to permit said machine to advance and be transported along the earth''s surface; advancing said endless series of excavating elements along an endless path to cause said excavating elements to dig into and to penetrate the earth''s surface, said penetration being effective both to provide traction for said machine and to fill said excavating units with earth; controlling the balance of weight bearing on said excavating elements and said mobility means thereby to control the traction of said excavating elements through said earth, said traction being controlled to advance said machine forwardly while excavating said earth entrapped within said excavation elements; and engaging the earth with a blade means below the penetration depth of said excavation elements and in a attitude which presents a forwardly and downwardly inclined surface to the earth to generate a downwardly directed force in addition to that caused by the weight of said machine in response to forward advancement of said machine.

15. A method as defined in claim 14 further comprising: locating said blade means in proximity to said excavation elements to assist self-loading of said excavation elements.

16. A method as defined in claim 15 wherein said step of controlling the balance of weight borne by said transport means and said excavation means comprises: varying the relative height between said excavation elements and said mobility means.

17. A method of excavating earth from the earth''s surface comprising: positioning a scraper blade so as to provide a forwardly and downwardly inclined surface in penetrating relation to the earth''s surface and at a predetermined penetration depth; providing a plurality of excavating elements arranged in an endless sequence, said excavating elements being adapted to entrap a volume of earth; locating said excavating elements in a position to penetrate the earth''s surface in advance of said scraper blade and at a lesser penetration depth than said scraper blade, whereby said excavating elements and scraper blade may be advanced so that said excavating elements remove a first layer of earth and said said scraper blade removes a second lower layer of earth; said blade also generating a downwardly directed force in response to forward advancement of the machine, advancing said endless series of excavating elements along an endless path to generate forward traction for said excavating elements and said scraper blade; providing a supplemental power traction means connected to said machine for providing additional forward tractive effort, said additional forward tractive effort being of a magnitude sufficient to overcome the forward resistance of the earth presented to the scraper blade which is not overcome by the forward propulsion of said excavating elements.