Steering, Driving And Single Track Support Systems For Vehicles

Abstract

A track vehicle having low ground pressure characteristics through use of a single full width track in which the track is laterally bendable with respect to the longitudinal axis of the vehicle whereby the cleats of the track are disposed along the true path of the vehicle to minimize sideways movements of the track elements and consequent soil sheer forces to facilitate the making of vehicle turns. Distinctive linkage elements are incorporated to interconnect track support and drive elements of the vehicle for maintaining a relatively constant track length it the central axis of the track. Various track drive, steering and engaging elements are used to beneficially utilize the novel kinematic and operative features of the vehicle support, track and track driving elements of the disclosed combination. The invention includes a track made up of separate link or shoe elements that are formed for cooperative interaction to distribute localized ground reaction forces by bridging action irrespective of whether said shoe or cleat elements are in extended or contracted relationship.

Description

The present invention relates to the general field of off-the-road vehicles and particularly to vehicle systems in which additional traction or flotation is obtained through use of multiple axles and wheels or, when more difficult terrain conditions are to be encountered, through use of endless track vehicle supporting and drive systems. Insofar as the wheel support for the vehicle is concerned, the invention is related to vehicle systems in which the wheels of more than one axle or a plurality of axles are themselves moved or steered in order to define the vehicle movement path. The invention presents improvements in offset fifth wheel or wagon steer fields. Considering the invention from the standpoint of track vehicles, the disclosure is related to the general field of tracks that are laterally bendable for track steering purposes and in part to the general field of bellyless track vehicles.

Previously some heavy service vehicles have been built which use a plurality of front steering axles so that the vehicles can still be steered even though an additional axle is provided for support of extreme vehicle loadings. Predominantly such previous systems have used Ackerman type steering in which components of the multiple axles operate together through use of linkage means so that the direction in which the wheels on the separate axles are steered will be mutually cooperative to assure execution of the proper vehicle turn as the wheels of any forwardly disposed axles are turned in the same direction.

Insofar as the track features of the invention are concerned, the bellyless characteristic of the present invention might in some measure be relatable to the "Groundhog" Army experimental vehicle or to vehicles of the type shown in the U.S. Pat. No. 3,198,273 to Turpin. The present invention is distinguished from such disclosures, inasmuch as a true bellyless configuration is now obtained through use of a single track in place of the two tracks shown in such earlier disclosures.

The bendable features of the present track system are in part relatable to the field of invention identified by U.S. Pat. No. 1,316,092 to Grover and Myer and U.S. Pat. No. 1,756,770 to Venzlaff. The present invention is primarily distinguished from such field of invention by the fact that in the present invention only a single bendable track is used for the support of the vehicle in place of the multiple tracks shown, described and used in the previous disclosures.

The present invention provides a vehicle system that is concerned with the provision of improved traction and a reduced ground pressure through use of a multiple wheel and axle configuration in which all of the vehicle wheels are steered cooperatively as necessary for the execution of efficient vehicle turns and to which system a track may be applied when it is desired to further increase the ground flotation characteristics of the vehicle. Steering movement of the wheels is accomplished by rotational movements of the supporting axles, since the wheels in the preferred embodiment are not pivotally steerable with respect to such axles. Through use of distinctive linkage mechanisms interconnecting the multiple axles of the vehicle, the wheels of any axle are radially disposed with respect to the center turning point for vehicle turns that are to be accomplished.

In addition to the radial disposition of the axles and wheels, the linkage mechanism assures a near constant length for the linear or arcuate distance between the front and rear axles as measured along the central axis of the axles and wheels. Since this distance is relatively constant whether the vehicle is in a straight ahead configuration or when turns are being executed, a track that is laterally bendable with respect to a longitudinal plane disposed vertically through the centerline of the vehicle may be disposed about the support wheels and axles to decrease the vehicle to ground bearing pressure.

A single track having a main tension member disposed along its central axis can be maintained on the vehicle without use of track tension compensating devices.

Use of a single track instead of separate tracks disposed on opposite sides of the vehicle provides easier satisfaction of a prime objective of the invention. A single track disposed about the support wheels of the vehicle and extending to completely cover the front and rear axles and supporting wheels can be designed to have a maximum ground contact area thus assuring the lowest ground pressure for any given length and width of vehicle.

In order to fully realize the desirable characteristics inherent in a single track configuration, the track itself can include certain beneficial features. First, since the track is to have a constant length at the longitudinal centerline a main tension transmitting element of the track is disposed along such centerline If the track is to be made up of link elements inclusive of cleats or lugs, such cross cleats are to be adapted for lateral movement as the track is bent with respect to the longitudinal plane of the vehicle, and the cleats also are arranged to assume a fan-shaped disposition with each cleat disposed along a line emanating radially from the center of the vehicle turn that is to be accomplished. If each segment or cleat of the track can be placed in this desire position, the cleats will at all times be disposed normal to and centered with respect to the course of travel for the vehicle. With such track disposition the side thrust or soil sheer forces associated with conventional track vehicle steering can be eliminated. The efficiency of vehicles of this type will be substantially improved, since the loss of power when accomplishing vehicle turns normally associated with conventional track vehicles is substantially reduced. In addition to improvements in efficiency, initial and maintenance costs can be reduced due to the use of simplified vehicle drive components. To improve the weight distributing characteristics of the track, a track lug or cleat configuration may be used which resists upward or concave bending of the ground contacting track elements without limitation of the radial fanning functions of such track components. A track incorporating these features can more efficiently transmit ground reaction loadings to spaced wheel supports.

FIG. 1 is a side elevation showing features of a preferred embodiment of the invention;

showing 2 is a plan view in partial cross section showing further details of the invention;

FIG. 3 is a plan view similar to that of FIG. 2 showing an alternate vehicle turning position;

FIG. 4 is a side elevation with parts shown in alternate position showing use of features of this invention to provide a wheel and track combination vehicle;

FIG. 5 is a side elevation showing features of a bridging link track together with alternate track drive and guiding components;

FIG. 6 is a side elevation showing the track cleats in extended configuration and further illustrating a bridging characteristic in the track links;

FIG. 7 is a side elevation showing the contracted disposition of track components;

FIG. 8 is an end elevation showing further features of the track cleats, center drive and sprocket drive components of the invention;

FIG. 9 is a partial top plan view taken along the line 9-9 of FIG. 8 showing additional track guide and retention features;

FIG. 10 is a plan view illustrating a different steering linkage embodiment of the invention;

FIG. 11 is a schematic plan view further illustrating potential vehicle use advantages when only a portion of the track is bent;

FIG. 12 is a schematic plan view showing potential alternate vehicle turn positions for the vehicle embodiment of FIG. 10; and

FIG. 13 is a graph illustrating the changes in length of the track at the central axis for vehicles having different wheel spacing patterns as various radius turns are made.

DESCRIPTION OF PREFERRED EMBODIMENTS

One embodiment of the invention is shown in FIGS. 1 through 3. In these FIGS. the principles of the invention are adapted for use on a vehicle of a type suitable for construction or maintenance purposes or for pushing, towing or material handling.

The vehicle 15 is provided with an essentially flat bed 16 above which the engine 17, cowl 18, operator seat 19 and steering apparatus 21 are mounted. On its outer lateral edges the bed 16 has downwardly depending frame supports 22 and 23 which transmit any vehicle load to the four supporting and steered axles 26, 27, 28 and 29, respectively, as numbered from front to rear and to the wheels thereon. The actual support or force transmission is from the cross frames or cross bars 31 and 32 to the main pivots 33 and 34 and from such pivots to the steered axles 26--27 and 28--29, respectively. The front axle 26 is interconnected to the pivot 33 by the torque tube 36, while the axles 27, 28 and 29 are connected to their respective pivots by the torque tubes 37, 38 and 39. The torque tube 37 is provided with an extension 41 which is interconnected to the steering apparatus 21 so that the axle 27 may be rotated with respect to the front pivot 33. In order that all the axles may be moved to alternate steering positions where the axles will be aligned radially with the center of any vehicle turn, the remaining steered axles 26, 28 and 29 are connected to the axle 27 by means of a distinctive linkage arrangement. First, the axle 27 is connected to the axle 28 by a drag link 42, which is joined to the axles 27 and 28 by pins 43 and 44. These pins are disposed on the axles 27 and 28 in positions equidistant from the centerline of the axles or the vehicle centerline with the drag link 42 being of such length as to maintain axles 27 and 28 in true parallel relationship when the vehicle is in a straight ahead configuration or with the steering apparatus in the neutral position. With this arrangement and with the front and rear pivots 33 and 34 being disposed at equal distances away from the axles 27 and 28, any rotation of the axle 27 about its pivot 33 will cause an equal but opposite rotation of the axle 28.

As distinguishable in FIG. 3, the drag link 42 is not connected to the steering apparatus 21 or to the pushrod 46 thereof. The pushrod 46 is connected to the torque tube extension 41 which rotates the axle 27 about its pivot 33. This will move the drag link 42 to cause the desired opposite rotation of the axle 28. As the axles 27 and 28 are moved, it is desirable to move the axles 26 and 29 to positions that are radially disposed with relation to the vehicle turn. It is also desirable that all of the inside and outside wheels be laterally positioned on true circular arcs having identical centers corresponding to the center of the vehicle turn. If the axles 26 and 27 are disposed at equal distances from the pivot 33 and if all of the axles are in fore and aft positions dimensionally related to the axle positions as illustrated, a linkage mechanism that will tend to rotate the front axle through an angle that is approximately 3 times greater than the turn angle for the axle 27 will provide the desired result. One linkage mechanism for interconnecting axles 26 and 27 or axles 28 and 29 to obtain this result is illustrated in FIGS. 2 and 3. Here a lever 47 pivotally mounted for rotation on the crossbar 31 by means of a bolt 48 is provided with arms 49 and 51 that are of equal length. The ends of the arms 49 and 51 are connected by links 52 and 53 to the torque tubes 36 and 37 in such manner that the crank arm distance from the pivot 33 to the point of attachment on the torque tube 36 is approximately one-third the crank arm distance from the pivot 33 to the point of attachment on the torque tube 37. Further, the resulting crank arms derived from such attachment are, in the neutral position, disposed for near tangent connection to said links and the circular movement patterns for said lever arms. For this relationship rocking movements of the lever 47 will cause rotational or angular movements of the axles 26 and 27 at about a 3 to 1 ratio. The paired front axles 26 and 27 are rotated in the same direction, and the paired rear axles 28 and 29 are also rotated together. The paired front axles, however, are rotated in a direction opposite to the rotation of the paired rear axles 28 and 29 due to operation of the drag link 42.

In order to obtain such desirable movements of the wheels and axles, pushrod 46 is connected to the steering apparatus 21 by rocker arm 54 pivotally mounted to the frame by the pivot bushing 56 on bracket 57. The rocker arm 54 is connected directly to a Pitman arm 58 of the steering apparatus 21 by a drag link 59. Adjustment clevises 61 are provided on drag link 59 and pushrod 46.

Inasmuch as the axle turning operations cause a lateral displacement of the axles with respect to the bed frame as well as a turning or rotation thereof, hydraulic or power assist steering may be beneficially incorporated to aid the driver-operator. For the embodiment illustrated hydraulic power steering could be economically provided, since the main vehicle propulsion force may be derived from a hydraulic system.

In this embodiment the engine 17 is connected through a clutch element in the clutch housing 62 to a hydraulic pump 63. The clutch may be eliminated when a control valve having a free flow position or "open center" is provided. The pump is connected by the flow lines 64 and 65 to the ports of hydraulic motors 66 and 69 driving the front axle 26 and rear axle 29 respectively. Further, these axles are positively driven with the wheels 67 and 68 on the inside and outside of the vehicle at the front axle 26 being rotated at uniform speeds at all times. Similarly, the wheels 70 and 71 will be driven at the same speed, and the drive components of the axles may be continuous from one wheel to the other and may be directly connected to the hydraulic motors 66 or 69.

For extensive use in the wheeled configuration, differential mechanisms could be used at any of the axles 26 through 29 to compensate for the difference in length of the inside and outside turning arcs for the vehicle so that excess slipping of the inside wheels would be avoided. A differential is not required, however, for axles 26 and 29 and the wheels thereon, since there is no relative slippage at these wheels due to a beneficial movement pattern operative between the end wheels and track.

The described arrangement provides a vehicle which may be operated on its wheels for movement along straight or curved courses. When operated as a wheeled vehicle, the presence of the multiple axles and of the greater number of wheels thereon can provide a vehicle having good flotation or low ground pressure characteristics. Since a plurality or all of the axles may be powered and since the power applied to any axle or wheel will be directed tangent to a desired course of travel for the wheels, good traction as well as good land flotation characteristics can be obtained. In such wheeled configuration the vehicle has direct use potentials in the fields of construction or materials handling, or for use in connection with various types of military vehicles.

In addition to providing a cooperative system that will keep the axles in radially aligned positions with respect to the center of a vehicle turn and in addition to providing a system that will maintain the wheels in aligned arcuate positions of curvature corresponding to arcs drawn from the center of the vehicle turn, the linkage mechanism described incorporates a further beneficial feature. The length of arc or line from the front axle to the rear axle and drawn through the centers of such axles remains relatively constant when the vehicle is in a straight ahead configuration or when turns of normal radius are being negotiated. This relationship, which is shown graphically in FIG. 13, makes it possible to adapt the vehicle to track laying purposes and to keep a track disposed about the wheels of the vehicle. Since the track tension exerted along the longitudinal centerline of the track or along the central arc of curvature as the track is bent will remain substantially constant for all turn radii of the vehicle, tracks may be used with the described vehicle support and drive system.

Construction features of the track itself can serve to better adapt the track to this intended usage. First, the track is to be laterally displaceable with respect to a longitudinal central plane passing vertically through the center of the vehicle or the track itself. The lateral displacements make it possible for the track to be disposed along the true path of the vehicle corresponding to the path of cooperative disposition for the wheels and axles, as described. Second, if the track is made up of multiple elements similar to the cross cleats or shoes of other track laying vehicles, provision is to be made for disposing such elements in a fan-shaped arrangement. Preferably each separate element should be positionable so that the ground engaging portions of each cleat or shoe will be radially disposed with respect to the center of the vehicle turn that is to be negotiated. By combination of these features the cleat or shoe elements can be moved laterally until the center of each element is disposed in position corresponding with an arc which has the center of vehicle turn as the center of the arc. With this arrangement each cleat or shoe element will be set down in position normal to and centered with respect to the true path of the vehicle at the point of ground contact. During turning maneuvers no lateral skidding movements will be required for the track shoes or cleats, and the consequent soil sheer forces associated with the sideways movement of track elements will be avoided. A track system incorporating these features is shown in FIGS. 1 through 3.

Though other systems for drive connection between the axles and the track are possible and are shown in later embodiments of the invention, FIGS. 1 through 3 illustrate a system in which driving contact for vehicle propulsion is established between the track and the forwardly and rearwardly disposed wheels. Though regular tires would provide good power transmission due to the wraparound type of engagement, the wheels can be provided with a drive cog-type configuration as illustrated in FIGS. 2 and 3 so that a more positive engagement between the wheels and elements of the track is possible.

For this track the cleat elements 72 are essentially of slat form and of length slightly longer than the outside width of the axle and tire assemblies. The cleats are spaced apart from each other when assembled in the track for relatively independent movement. An enlarged segment 73 is provided at the center of each cleat 72, however, so that the segments will at all times be in contacting relationship with the corresponding segments of adjacent cleats. The main tension members for the track, such as the cables 74 and 76, extend through the cleats at the enlarge segments 73 to hold the segments in contacting relationship. Since these cables are positioned at the centerline of the track and since the axles and wheels maintain the described constant length ratio even when the vehicle is being turned, the tension in the cables 74 and 76 will not be changed significantly when the track is bent to displace the cleats laterally when vehicle turns are being made. Essentially, the cables and segments together make up a central tension element or characteristic ligament of a drive spine 75 for tracks useful in connection with practice of the present invention.

The widened nature of the central segments 73 necessarily provides clearance between adjacent cleats 72 at the ends so that the cleats may be disposed in the desired fan-shaped pattern during turning maneuvers. In addition to providing clearance between the slatlike elements of the cleats 72, the segments must likewise provide clearance for the drive cups 77 disposed adjacent the outboard edges of the cleats 72 for direct engagement with the lugs of the drive wheels. These cups 77 are provided with a base 78 and upwardly raised flanges 79 for better engagement with the lug elements of the tires 67--68 and 70--71. In general the bases 78 are designed for close contact with the bottom of the lugs on the driving wheels, while the flanges 79 engage the sidewalls of such wheels. With this combined structure the base to lug contact provides the main propulsion forces, while the sidewall to flange contact serves to transmit lateral displacement forces from the steering and support system to the track thus keeping the track aligned with the intended arc of curvature and vehicle turn.

While the main track tension and drive forces are transmitted by the cables 74 and 76 of the drive spine, the track is further provided with band members 81 that are preferably placed adjacent the outboard edges of the cleats 72 to help maintain the cleats 72 in regulated positions. The track bands 81 are disposed beneath the drive cups 77 in the track illustrated. When the track is in the straight ahead configuration, the bands 81 will be slightly looped between adjacent cleats 72. When the maximum turn is being negotiated, as illustrated in FIG. 3, the track band 81 on the outside of the vehicle turn will be stretched, while the track band 81 on the inside of the turn will be most severely looped. The drive cups 77 of adjacent cleats 72 will be in contacting or near contacting relationship at the inside of the track with the band 81 looped between the adjacent cleats 72. The longitudinal stiffness of the band itself will tend to keep the cleats 72 in better regulated relationship insofar as lateral displacement of the separate cleats is concerned. Two fasteners 82 are used to join the bands 81 to the cleats 72 to better develop the sheer resistance of the bands 81 that assures good cleat alignment. The fasteners 82, as shown, may be engaged through the drive cups 77, the bands 81 and cleats 72 to hold all of these elements in assembled relationship.

Though a straight across cleat may be used, it may under some conditions be preferable to use a cleat that would not normally contact the ground along its entire length. A cleat having an interrupted contact pattern is shown in FIGS. 2 and 3, where the center section 83 of the cleat 72 is raised. A track having a raised center section will not be significantly different from a track having straight across cleats, insofar as track operation, bending pattern and track tension characteristics are concerned. The raised center section does change the ground contact pattern and may improve some vehicle drive and steering characteristics. When the vehicle is traveling on hard ground, the raised center section can prevent teetering of the vehicle center of gravity when obstructions are contacted at the center of the track.

When this track embodiment is used on the vehicle support and steering system described, the cleats 72 may be laterally displaced with respect to a vertically disposed longitudinal plane disposed along the centerline of the vehicle. Lateral displacement forces are transmitted to the track from the steering and support system by lateral track guiding members made up of track and guide elements. In the present embodiment the interengagement between the cup flanges 79 and the sidewalls of the driving and nondriving wheels provide the desired track steering. The nondriving wheels 84 disposed on the intermediate axles 27 and 28 help to keep the track in the desired arcuate patterns which establish the constant tension relationship for the track at its centerline.

A second desirable track construction is presented in FIGS. 5--9. This track, which is fully adaptable for use with the vehicle support and steering system described, incorporates features designed to better distribute ground reaction loadings to the vehicle elements. In addition to such features, the cooperative track and center guide components provide a more positive control of lateral bending and different track propulsion force transmitting components. In this construction the cross cleats 172, which again extend across substantially the full width of the vehicle to contact the supporting wheels, are formed of flat metal stock to provide an inwardly disposed base 86, a reinforcing flange 87, a lock extension 88 and a base extension 89. At the track centerline the cleats 172 are joined to the links 91 of an endless chain 92 with the links 91 associated with adjacent cleats 172 being pivotally joined by the link pins 93. As shown in FIG. 5, each of the links is of identical shape with a front gusset 94 of shape to engage and be joined to the reinforcing flange 87 and a foot element 96 of a shape to engage and be joined to the base extension 89. A face 95 of the foot 96 is then disposed to engage the reinforcing flange 87 of an adjacent cleat 172. With this arrangement the chain links and track elements may all be bent along a line of convex curvature without any interference between the described elements. At the same time movement of the elements into a concave configuration will be resisted when the faces 95 of the foot element 96 come into contact with the reinforcing flanges 87. The described elements, therefore, provide a bridging characteristic which will resist concave bending of the lower flight of the track when the vehicle is being moved over some obstructions. This bridging characteristic distributes any concentrated ground loading to adjacent support wheels of the vehicle.

In the actual construction and use of the described type of track, some clearance is provided in the fit between the pins 93 and the holes in the link elements 91. This operative clearance makes it easier to bend the track laterally so that the desired fan-shaped placement of the track for track steering purposes may be obtained. FIGS. 6 and 7, respectively, illustrate the disposition of the track cleats 172 at the outside and at the inside of a vehicle turn. As here illustrated, the base and lock extensions 88 and 89 fit together cooperatively in either the extended or contracted relationship. In either relationship, and as specifically shown in the FIG. 6 drawings, the disposition of a concentrated ground reaction point at the lateral free ends of a cleat 172 which would cause the cleat to be moved from its normal position of alignment with adjacent cleats will bring elements of the adjacent cleats into contacting relationship to better resist such concentrated loading. The contact between the lock extension 88 and base extension 89 as shown in FIG. 6 will tend to transmit any concentrated ground reaction force to the central drive spine provided by links 91 and chain 92. As illustrated, extensions 88 and 89 are of such length as to assure a contacting relationship therebetween even though the cleats are in the maximum fan-shaped or extended disposition.

While the assembled links of the drive chain 92 provide the main tension transmitting element or drive spine for this track embodiment and while a sprocket could be used in engagement with the pins 93 to rotate and move the track, it is preferable to use a separate track propulsion element in connection with the present embodiment of the invention. Paired drive sprockets 97 may be positioned for engagement with the mating rollers 98 joined to each of the cross cleats 172. The rollers 98 and sprockets 97 are best disposed closely adjacent to the central drive spine for the track but are illustrated in a lateral outboard position in FIG. 8 for clarity of illustration only. When disposed in the position as illustrated, good drive engagement and disengagement is still possible due in part to the flexible nature of the track and in part to the design configuration for the teeth 99 of sprocket 97. The teeth 99 can be formed to have a higher profile than standard so that engagement between the teeth 99 and the rollers 98 is assured even though the cleats 172 are disposed in fanned positions. Where the sprocket-type drive is used, the sprockets can be positioned at locations away from the end axles. If placed at intermediate positions, such as at or adjacent to the intermediate axles 27 and 28, the sprockets would be of a lesser diameter than the diameter of the wheels 84 and would be positioned to securely engage only the bottom or top flight of the track.

FIGS. 5, 8 and 9 illustrate a further track feature that can be beneficially incorporated and used in track systems adapted for the presently described equipment. In order to assure lateral displacement of the track elements as necessary to dispose the track cleats in the desired fan-shaped array, positive track guiding elements can be provided. As shown in these FIGS., each of the links 91 can be provided with a top flange 101 that extends laterally outward from the links 91. This flange is spaced inwardly away from the base 86 of the cleat 172 so that paired guide idlers 102 having roller discs 103 may be engaged under the top flanges 101. The idlers 102 are rotatably mounted on a steering bar 104 which may be joined to the steering apparatus 21, to any of the axles 26--28 or to the torque tube mountings therefor. With such arrangement the steering bar 104 will be moved laterally, and the idlers 102 will through interengagement with the flanges 101 of the links 91 physically displace such links and the associated cleats 172. For track guiding purposes the flange 101 will contact the hub of the guide idlers 102. At the same time the roller discs 103 are positioned beneath the flanges 101, and the intercontacting relationship between such discs and the flange 101 will prevent the track from sagging away from the guide idlers 102 under conditions where the vehicle bridges spaced obstructions, such as at a ditch. This feature which holds the track in engagement with the lateral track guiding members assures proper disposition of the track for all operating conditions.

The track described could be propelled by the drive wheels 67--68 and 70--71 of the drive system previously described. The wraparound engagement between the wheels and the track would be adequate for the drive propulsion of such track. This beneficial result is possible and can even be efficient due to an interesting interrelationship existing between the track and wheel movement patterns for tracks that would be suitable for use in connection with the present invention.

First, in installations where the inboard and outboard drive wheels, such as the wheels 67 and 68, are a torsionally coupled pair having equal rotative and circumferential speeds, the individual cleats of the track that are in engagement with the wheels from a top line of tangency to a bottom tangent point of departure will be disposed in parallel relationships at all times even though the cleats in the top or in the ground contacting flight of the track are disposed in a fanned relationship. The same relationship will exist at the rear drive wheels from the bottom point of tangency with the wheel circumference to the top point of tangency. This parallel spacing of the cleats as they rotate in contact with the front and rear wheels or other cylindrically disposed guide elements is derived from operational features of the described equipment. With the circumference and the rotative speed of such paired wheels or elements equal, the cleats will assume parallel positions due to interference between adjacent segments. If the drive wheels are provided with lugs, the lug spacing will assure an even placement of the cleats. Further, the movement pattern for the cleats at the point of transition from the fan-shaped array to engagement with the wheels tends to establish the even and parallel spacing for the cleats as they are engaged with the forwardly or rearwardly disposed portions of the end drive wheels or support members.

With the cleats disposed in evenly spaced and parallel relationship as they pass over the front drive wheels, a further kinematic benefit results. As each cleat comes to the point of tangent departure from the front drive wheels, the cleat will be disposed at a position parallel to the front axle. Since the axle is disposed in radially aligned position with respect to the center of vehicle turn, each cleat being brought into contact with the vehicle supporting ground will be placed in the desired fan-shaped position wherein the cleats are and remain radially aligned with respect to the center of vehicle turn. At the back drive wheel the radially aligned cleats will come into initial contact with the back drive wheels with both the cleats and the rear axle being radially aligned. Accordingly, if the rear drive wheels or elements are considered to define a cylindrical surface, each successive cleat at the point of initial contact with such cylindrical surface will be parallel to the center of the cylindrical surface and will be aligned with the generator or elements of such surface. With each cleat being picked up from a position parallel to elements of the cylindrical surface, the spacing of the cleats as they roll into contact with the rear drive wheels will stay constant and parallel until the cleats part from the rear drive wheel at the top line of tangency.

The fact that the track elements or cleats stay in parallel relationship while in contact with the end drive wheels or guide elements and are moved to laterally displaced positions of radial alignment with respect to the center of vehicle turn when out of contact with the end drive elements gives rise to improved efficiencies for track operation in addition to the improvement in driving or propulsion contact. If each cleat is brought into ground contact with the ground engaging elements of the cleat already disposed in position normal to the direction of vehicle travel and centered with respect to the curved path of the vehicle movement pattern, the soil sheer forces which normally resist the turning of track vehicles will be substantially eliminated.

With the elimination or reduction of soil sheer forces, previously established length to width ratios for track vehicles may be beneficially increased. Accordingly, the present track and track steering systems may be used to efficiently provide a track vehicle that could be of nonstandard configuration. With the capability to handle and use a longer track, the ground pressure characteristics of the vehicle may be improved to provide mobility under conditions which now exceed the capability of conventional double track vehicles. The greater length to width ratio could also provide higher speed capabilities and decreased jolting or pitching movements of the vehicle when obstructions are encountered.

While the described embodiments of the invention could be operated as wheel vehicles when the track system is removed, it is recognized that some users might require a more readily changeable system. FIG. 4 illustrates a track and steering system of the type disclosed herein as applied to a conventional truck vehicle. The main frame 106 of the truck 105 provides supports 112 to which a track steering and support system 107 is applied. This steering and support system 107 incorporates structural support features as shown in FIGS. 2, 3 and 10 assembled in such manner that the steering components may be interconnected to the steering apparatus 111 of the truck 105. The track operations of this vehicle then will be similar to those previously described. When severe use requirements have been satisfied, the front wheel assembly 108 and the rear wheels 109 may be lowered to the alternate position illustrated, and the vehicle could then be moved over roads as a wheel vehicle with the front wheel assembly 108 being steered in conventional manner through an alternate engagement with the steering apparatus 111. A vehicle of the described type could have extensive use for utilities and other service industries where potential off-the-road work sites might be disposed at widely dispersed locations.

FIG. 10 presents an alternate steering system which can be used to control the movement patterns for the wheels and axles in satisfaction of the operational requirements previously set forth. In this embodiment of the invention the axles 126, 127, 128 and 129 disposed from front to rear are positioned similar to the comparable components of the FIG. 2 disclosure. The axle 127, however, is provided with an offset fifth wheel or pony truck-type of mounting so that the vertical or twisting movements of this axle will at all times correspond to the movements of the crossbar 131 and vehicle frame. As in the previous installation, the axle 127 will turn about the front pivot 133 with the fifth wheel assembly 130 confining movements of the axle 127 to the plane of the fifth wheel 130 and the crossbar 131. All of the remaining axles of the vehicle assembly are provided with pivots or flexible coupling elements 136, 138 and 139. Accordingly, these axles may be rotated with respect to a longitudinal axis of reference independently of the crossbars 131--132, the pivots 133--134, or the frame components of the vehicle. Such independent movement patterns will be restrained by separate spring systems (not shown) or by torque absorption capabilities of the described flexible coupling elements. This additional restrained freedom of motion will provide greater support system flexibility so that the unit when operated as a wheel vehicle or as a track vehicle will have better ride characteristics.

The steering components of the vehicle are also changed. First, a modified linkage assembly is provided for the front axles 126--127. In this embodiment of the invention lever assembly 147, which rotates about a bolt 148, has angularly disposed arms 149--151. These arms are connected respectively by the links 152--153 to cross arms for the axle assemblies 126--127 in a manner similar to that previously described for the previous embodiment and directly similar to the connection pattern for the lever 47 and links 52 and 53 used to control the movement patterns for the rear axles 128 and 129. In other words, the crank arm distance from the pivot 133 to the point of attachment on the torque tube 36 is approximately one-third the crank arm distance from the pivot 133 to the point of attachment on the torque tube 37. As in the previous construction, the resulting crank arms are disposed for near tangent connection to said links and the movement patterns for said lever arms 149--151. The rear lever assembly 47 is similar to that previously described. Parts thereof have been given the previous identification numbers.

This embodiment of the invention is again designed to be driven by hydraulic motors 66 and 69 with the fluid power being connected through the lines 64 and 65. Since many hydraulic pumps for vehicle drive systems now provide for implement power auxiliaries, the present embodiment of the invention is provided with a hydraulic vehicle steering system. Hydraulic cylinders 140 and 141 are positioned at the front and rear of the vehicle with the front hydraulic cylinder 140 being operative between the front crossbar 131 and the front axle 126, while the rear hydraulic cylinder 141 is coupled between the rear crossbar 132 and rear axle 129. If a drag link similar to the solid drag links 142 of the previous embodiment is interconnected between the axles 127 and 128, or if the modified drag link 142 as illustrated is considered to be of constant length, operation of either of the cylinders 140 or 141 would be adequate to move the axles and wheels to the various steered positions.

Alternately, the two hydraulic cylinders illustrated can be coupled together to more efficiently produce the type of turning maneuver disposition as shown in FIG. 3. For the present embodiment, however, it is intended that the drag link 142 be provided with a length adjusting feature through incorporation of the adjusting cylinder 143. If the cylinder is kept in a neutral extension position, the fixed full track length turning maneuvers previously described will result. If the effective length of the drag link 142 is changed by addition or removal of hydraulic fluid from the cylinder 143, the on-the-ground turn configuration of the track can be changed over less than the length of the full track. With contraction of the link 142 and contraction of the cylinder 140, the track could be bent into the pattern as shown in FIG. 11. With extension of the link 142 and extension of the cylinder 140, the track could be moved to the configuration shown in FIG. 12 at A for the start of a left turn. Through use of the multiple cylinders 140 and 141 and the extensible link 142, the separate halves of the track may be controlled independently.

This capability to bend only a portion of the track can have beneficial use in connection with some vehicle operations. As indicated in FIG. 11, a portion of the track could be bent in a steering maneuver to compensate for laterally directed resistance forces, while the main force of the track was still exerted in a straight ahead direction. If an angle dozer 144 is mounted on the frame 116, the front half of the track can be bent inwardly toward the work point of the blade 145 so that the dozer can be maintained on an efficient straight ahead course as materials are being cut way from an earth embankment 146. With this track control feature a greater portion of the full tractive power of the vehicle could be applied to an eccentric work load than is now available with the conventional clutch and brake control steering systems used on two track vehicles.

In addition to potential uses where offset load resistances can be countered by a bending of the track, this half track control feature would also be available to help maintain a track vehicle on course when sidehills are being negotiated. The lead or the rear half of the track could be bent to compensate for any downhill force component that would act to cause the vehicle to drift downhill. In these offset work operations some track slippage or soil sheer forces would be introduced by the partially bent track. The same features, however, can serve to further decrease such ground reaction forces when the half track steering components are used in the manner shown in FIG. 12 to negotiate turns. Beginning at A, the front half of the track can be initially bent as the vehicle is guided into a left turn. At position B as shown in dotted outline, both the front and rear halves of the track would be bent. At position C, as the vehicle comes out of the turn, only the rear half of the track os bent.

With progressive control of the track steering operations, an efficient turn can be made and the soil sheer forces introduced due to the forcible bending of the track preparatory to making a prescribed turn will be less than where a full track is bent. If the whole track is bent at one time, some track cleats that are already in contact with the ground surface must be forcibly moved laterally in order to attain the curved disposition as shown in FIG. 3. With the type of track steering control available through use of the combined elements shown in FIG. 10, each track cleat on a moving vehicle can be brought into contact with the ground substantially at the position that the individual cleat will maintain until the full vehicle turn maneuver is completed.

With the greater maneuvering flexibility available through separate control of individual or paired axles, longer tracks can be used without excessive changes in the arcuate length of the track due to turn bending. In fact, a separate vehicle could be connected to the unit illustrated in FIG. 10 by connecting a drag link 242 to the forward axle of a next paired axle system or next vehicle steering system. With such interconnection the steering control movements of the forward vehicle will have an effect on the controlled steering of following axle systems. A train of vehicles could actually be provided in which the tracks were separate to each vehicle, or a single track assembly could be stretched over the full length of the train vehicles with the individual platform beds of the vehicles being hinged one to the other to accommodate the vehicle support beds to the bendable movement patterns of the track.

If separate tracks are to be used individual vehicles in a train combination, some substitute linkage between the vehicles will be necessary in place of the drag link 242. A simple hitch disposed at the centerline line of the platform bed and extending behind the rear axle a distance equal to or slightly greater than the distance of said axles away from their respective crossbars or pivots would provide an efficient hitch between vehicles. Preferably, such hitch should be disposed at the level of the vehicle axles. With this arrangement a trailing vehicle would be able to follow in the path of the lead vehicle without interference between the separate tracks and without excessive lateral displacement of one vehicle bed with respect to the other as the turn is negotiated.

FIG. 13 presents a graphic analysis of the length of the wheel base as measured along the longitudinal axis of the vehicle or along an arc of curvature passing through the centers of all the support axles against various vehicle turn radii. The results tabulated are characteristic and can be substantially duplicated by all of the embodiments shown and described. The axle to pivot distances are set forth for various vehicle configurations inclusive of a three-axle combination D. For the A. configuration it should be noted that the wheel base measurements increases only .454 inches for a 20-inch radius and only by .029 inches for a 40-inch radius turn. From this analysis it can be seen that the difference in the curved or the straight length of the track as measured at the centerline is not excessive for turns of required operational radius. Track tension and, accordingly, track retention can be maintained with such minor deviations in operational track length for many and varied vehicle configurations.

Claims

I claim:

1. A vehicle for guided movement along the supporting ground comprising a frame, a power source for the drive propulsion of said vehicle, a plurality of longitudinally spaced axle components for said vehicle, rotatable elements on said axles disposed adjacent the lateral sides of said vehicle for progressively moving and/or supporting said vehicle as the vehicle moves along the ground, pivots for more than one of said axles, said pivots being offset with respect to the axis of said axles whereby the pivoted axles may be laterally displaced with respect to the centerline of said vehicle, steering means for disposing the axis of said axles and the rotatable elements associated therewith radially with respect to the center of turns being executed by said vehicle and for aligning the movement paths of longitudinally spaced rotatable elements at either side of said vehicle in positions for following arcs of curvature having a center at the center of vehicle turn, and a single laterally bendable endless track for disposition about said axles and said rotatable elements for the exclusive ground contacting support and steering of said vehicle.

2. Structure as set forth in claim 1 wherein at least two pivoted axles are provided.

3. Structure as set forth in claim 1 wherein said steering means is interconnected to the pivoted axles for moving the pivoted axles disposed forwardly and rearwardly of said vehicle in opposite rotative directions.

4. Structure as set forth in claim 1 wherein at least two pivoted axles are disposed in pairs having a common pivot.

5. Structure as set forth in claim 4 wherein said steering means is inclusive of elements interconnecting paired axles for rotating said axles about said common pivots in the same rotative direction but in nonequal degree.

6. Structure as set forth in claim 5 wherein axles disposed furthest from the fore and aft center of the vehicle are rotated more than axles disposed closer thereto.

7. Structure as set forth in claim 4 wherein said vehicle has at least two axle pivots.

8. Structure as set forth in claim 7 wherein at least two axle pivots have paired axles moving thereabout.

9. Structure as set forth in claim 8 wherein said steering means is inclusive of linkage elements for moving the paired axles disposed forwardly of said vehicle in rotative directions opposite to the direction of movement for paired axles disposed rearwardly of said vehicle.

10. A vehicle for movement along a supporting surface comprising a frame, axles supporting the frame, at least two of said axles including an arm secured to the axle and pivotally attached to the frame at a point spaced from the principal axis of the axle, disposed linkage interconnecting at least said two axles for movement about said points form a first position wherein said axles are parallel to a second position wherein the principal axis of all said axles are aligned radially with a center of curvature, and the center of each axle is arranged substantially in an arc about the center of curvature, wheels rotatably mounted on the axles, a single track bendable in the plane of the supporting surface extending around the axles and wheels, said track including a plurality of elongated members generally parallel to said axles and a tension transmitting centrally disposed spine bendably connecting the elongated members, said spine defining a fixed maximum center circumference for said track, means for maintaining each elongated track member substantially in alignment with said axles and means for driving a pair of said wheels.

11. A vehicle for guided movement along the supporting ground comprising a frame, a power source for the drive propulsion of said vehicle, rotatable elements for progressively moving and/or supporting said vehicle as the vehicle moves along the ground with a plurality of said elements arranged in longitudinally separated and axially aligned pairs disposed forwardly and rearwardly of said vehicle for the steering control of said vehicle, pivots for said paired steering control elements, said pivots being offset with respect to the axis of said elements, steering means for disposing said paired elements in in position aligning the rotational axes of separate pairs radially with respect to the center of turns being executed by said vehicle and the movement paths of longitudinally spaced pair elements to correspond with an arc of curvature having a center at the center of vehicle turn, and a single laterally bendable endless track for disposition about said paired elements at the front and rear of said vehicle for the exclusive ground contacting support and steering of said vehicle.

12. Structure as set forth in claim 11 and further comprising means interconnecting said power source and at least one of said end pairs for the drive propulsion of said vehicle.

13. Structure as set forth in claim 11 wherein said linkage elements rotate said longitudinally spaced pairs about their respective pivots in equal but in opposite directions.

14. A vehicle for movement in straight or curved paths along the supporting ground comprising a frame, a power source for the propulsion of said vehicle, a single laterally bendable endless track for ground contacting support and steering of said vehicle, track guide elements on said vehicle for engagement with said bendable track to control the positioning thereof, and means useful when vehicle turns are to be when vehicle turns are to be made for moving at least two of said track guide elements to orient all of said track along an arc of curvature having a center at the center of vehicle turn.

15. Structure as set forth in claim 14 wherein a plurality of said track guide elements additionally provide track supports for transmission of the vehicle weight to the track and the supporting ground.

16. Structure as set forth in claim 15 and further comprising a plurality of cleat elements for said track, a tension member disposed intermediate the ends of said cleat elements and connected thereto providing a drive propulsion spine for said track, and means interconnecting said power source and said drive propulsion spine for moving said track.

17. Structure as set forth in claim 16 wherein movable track guide elements are track supports disposed adjacent the lateral sides of said vehicle and wherein said track cleats extend laterally from said drive spine for contacting relationship with the support elements on opposite sides of said vehicle.

18. Structure as set forth in claim 16 nd further comprising a center segment on said cleat elements of greater width than the outboard ends of said cleat elements whereby operative clearance is provided between adjacent cleat elements.

19. Structure as set forth in claim 18 and further comprising steering means for laterally displacing said track guide elements, the drive spine of said track and said cleat element s whereby all the individual cleats may be disposed in positions radially aligned with respect to the center of turn for the vehicle.

20. Structure as set forth in claim 16 wherein said tension member is inclusive of segments holding said cleat elements in space apart relationship and wherein the width of longitudinally extending components of the cleat elements at any planar elevation is less than the longitudinal length of said segments whereby operative longitudinal clearance is provided between adjacent cleat elements.

21. Structure as set forth in claim 20 and further comprising steering means for laterally displacing said track guide elements, the drive spine of said track and said cleat elements whereby all the individual cleats may be disposed in positions radially aligned with respect to the center of turn for the vehicle.