US3225852A

US3225852A - Traction for earth movers and the like

Info

Publication number: US3225852A
Application number: US374882A
Authority: US
Inventors: Lovel R Simmons; Hollis H Travis; James T Monk; Andrew W Ogletree
Original assignee: MRS Manufacturing CO
Current assignee: MRS Manufacturing CO
Priority date: 1964-06-05
Filing date: 1964-06-05
Publication date: 1965-12-28
Anticipated expiration: 1982-12-28

Description

L. R. SIMMONS ETAL 3,225,852

TRACTION FOR EARTH MOVERS AND THE LIKE Original Filed May 22, 1960 Dec. 28, 1965 6 Sheets-Sheet 1 INVENTORS.

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TRACTION FOR EARTH MOVERS AND THE LIKE Original Filed May 22, 1960 6 SheetsSheet 2 Dec. 28, 1965 L. R. SIMMONS ETAL 3,225,852

TRACTION FOR EARTH MOVERS AND THE LIKE Original Filed May 22, 1960 6 Sheets-Sheet 5 Will 3A srsasmay MEWS JZzme: [Honk Dec. 28, 1965 1.. R. SIMMONS ETAL 3,

TRACTION FOR EARTH MOVERS AND THE LIKE 6 Sheets-Sheet 4 Original Filed May- 22. 1960 L. R. SIMMONS ETAL 3,225,852

TRACTION FOR EARTH MOVERS AND THE LIKE Original Filed May 22, 1960 Dec. 28, 1965 6 Sheets-Sheet 5 ENTOR5.

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TRACTION FOR EARTH MOVERS AND THE LIKE Original Filed May 22, 1960 6 Sheets-Sheet 6' glezree Emma/2,6

Andrew 80. 0

United States Patent TRACTION FOR EARTH MOVERS AND THE LIKE Lovel R. Simmons, Jackson, Miss., Hollis H. Travis,

Dallas, Tex., and James T. Monk, Louisville, and Andrew W. Ogletree, Clinton, Miss., assignors to M-R-S Manufacturing Company, Flora, Miss., a corporation of Delaware Continuation of application Ser. No. 32,195, May 27, 1960. This application June 5, 1964, Ser. No. 374,882

17 Claims. (Cl. 180-14) This application is a continuation of our application Serial 32,195, filed May 27, 1960, now abandoned, for Improved Tractor for Earth Movers and the Like. This invention is concerned with the movement of earth, coal, and the like, and is particularly concerned with improved traction for earth movers.

In order to move dirt and the like economically, it is necessary to carry very large loads. Although good highways or haul roads produce no particular problems, such loads must often be carried over terrain providing very poor traction, and often uphill over quite substantial grades, as from a borrow pit. Frequently material which is inherently of poor traction is combined with uphill movement.

There are three recognized types of rubber tired earth movers, respectively having two axles, three axles, and four or more axles. Each such earth mover or unit includes a trailer or semi-trailer, which may be provided with a blade or plate at the lower front end thereof to scrape dirt up for hauling in a bowl or hopper immediately to the rear of the blade or plate. The device then is frequently known as a scraper.

The two axle unit comprises a tractor having a single axle, and a semi-trailer having a single axle at the rear end and supported at the front on the tractor. The semitrailer has a gooseneck arrangement at the front in order to clear the wheels of the tractor when the tractor turns. This type of unit is relatively small, and is of restricted load carrying capacity.

The three-axle unit or earth mover is similar to the two axle unit, except that an additional axle is provided on the tractor for steering thereof. As in the two-axle unit, one axle of the tractor (the rear axle) usually provides the only driving force.

In the four-axle unit there is a two-axle trailer which is connect-ed to a two-axle tractor through a draw bar. Usually, driving force is provided only by the rear wheels of the tractor. However, it is known that some of the wheels of a trailer can also be driven, either through appropriate mechanical or electrical connections from the engine of the tractor, or by means of an auxiliary engine on the trailer.

For traction purposes relatively soft tires that will flatten out under load are best when maximum tract-ion is required, as on poor-tracti-on terrain, or on .rather substantial uphill grades. However, low-pressure traction tires are incompatible with high pay loads combined with high speeds. High pressure and high capacity are limited by commercially available tires available without special order, which enhances the value of having a multiplicity of tires, as is possible with a separate prime mover and load carrying vehicle for hauling the large loads desired for most economical operation.

It is not particularly difficult, nor is it particularly expensive to install an engine in an earth mover which engine develops more power than can be used at low speeds, traction being the limiting factor. Probably the 'best means heretofore available for securing improved traction on prime movers whereby to utilize more of the available power is that known in the trade as weight transfer. Such weight transfer is shown in many of the 3,225,852 Patented Dec. 28, 1965 "ice prior patents of L. R. Simmons, Simmons 2,459,098 being exemplary. In accordance with the weight transfer system, an inclined or semi-vertical hydraulic actuator is mounted at the lower rear part of the tractor and at the upper front part of the trailer. When the actuator is extended, part of the load of the trailer is transferred from the front wheels of the trailer to the wheels of the tractor. This can be to only the rear wheels, or it can be to all four wheels of the tractor when all four wheels thereof are driving wheels in accordance with Simmons Patent 2,899,004. The increased weight on the wheels of the tractor gives much better traction, and hence enhanced load hauling ability. The mere increase in weight on the Wheels would be sufficient in itself to increase the traction, since friction is a function of the coefiicient of friction and the normal force urging frictional surfaces together. However, in addition to this, the increased weight causes the tires of the tractor to flatten out rather substantially, thus causing them to conform better to the surface of the terrain, and to provide .a better grip thereon.

The weight transfer feature is generally used only at low speeds, and generally on poor-traction terrain or on grades. Once a reasonable speed is obtained on a relatively good road, the weight transfer is abandoned by releasing the pressure in the hydraulic actuator. This avoids continued flattening which would result in rapid wear of the tires on the tractor at high speed.

We have discovered that weight transfer plus drive of one or more trailer axles (in addition to the usual tractor drive) can be combined most advantageously. The result of this combination is rather surprising. One would rather expect that if the .two features were to be combined, there would be an arithmetic sum of their effectiveness. In other words, if one were to add weight transfer, a certain improvement in horizontal force transmission between the vehicle and the ground would be attained. Similarly, if one were to add trailer drive to an ordinary tractor drive, a certain improvement in traction would be found. It would be expected that if the two were utilized at the same time, that the two improve ments in traction would add together in a simple arithmetic manner. However, this is not the case. In a typical example, the total horizontal tractive force, or draw bar pull is over ten percent greater than the simple sum of the draw bar pull of the tractor with weight transfer plus draw bar pull of trailer drive.

Acordingly, it is an object of this invention to provide a machine for moving earth and the like having improved traction.

Specifically, it is an object of this invention to provide an earth moving machine having four axles and incorporating weight transfer from the trailer to the prime mover and further having in combination therewith drive of at least one trailer axle. Furthermore, it is an object of this invention to provide an earth moving machine having four axles incorporating weight transfer and trailer drive, and further including locking differentials to prevent spinning of any one drive wheel.

It is yet another object of this invention to provide a machine for moving earth and the like having four axles wherein the tractor can be attached to either end of the trailer, and including provision for weight transfer from the trailer to the tractor in combination with drive of at least one trailer axle.

Still another object of this invention is to provide a machine for hauling earth and the like including the aforementioned principles of weight transfer, trailer axle drive, and differential locks, and fuurther including common means to effect operation of all of the foregoing, and further including selectively operable override.

It is another object of this invention to provide a machine for hauling earth and the like incorporating the including a roof.

aforementioned principles of weight transfer, trailer drive,

and differential lock, and further including common means for effecting operation thereof and for simultaneously controlling the position of a transmission.

Other and further objects and advantages of the present invention will be apparent from the following description when taken in connection with the accompanying drawings wherein:

FIG. 1 is a side view of an earth moving machine constructed in accordance with the principles of the present invention;

FIG. 2 is a fragmentary view with a part broken away showing details of the construction of FIG. 1;

FIG. 3 is another side fragmentary view with parts broken away showing additional details;

FIG. 4 is a pneumatic circuit illustrating control of certain of the mechanisms of the foregoing figures;

FIG. 4a is a modification of a part of the pneumatic circuit;

FIG. 4b is a further modification of a part of the pneumatic circuit;

FIG. 5 is a somewhat schematic side view partially in section illustrating a pneumatic control;

FIG. 6 is a side view generally similar to FIG. 1 showing a modification of the invention;

FIG. 7 is another somewhat schematic view similar to FIG. 5 and accompanying FIG. 6;

FIG. 8 is a fragmentary side view with parts broken away showing a modification of the invention;

FIG. 9 is a top view of the apparatus in FIG. 8;

FIG. 10 is a fragmentary side view illustrating a further modification of the invention;

FIG. 11 is a top view accompanying FIG. 10;

FIG. 12 is a side view similar to FIG. 1 and illustrating another embodiment of the invention; and

FIG. 13 is a fragmentary side view illustrating details of the embodiment of the invention illustrated in FIG. 12.

Referring now in greater particularity to the drawings, and first to FIGS. 1-3, there is shown an earth moving machine designated generally by the numeral 20 and comprising a tractor 22 and a trailer 24, the trailer in this instance specifically comprising a scraper. The tractor is provided with a front axle having a pair of pneumatictired wheels 26 thereon, and with a rear axle having a pair of pneumatic-tired wheels 28 thereon. The tractor, sometimes known as the prime mover, comprises an engine 30 from which the rear wheels 28 are driven, as by the usual drive shaft and differential gears. The differential gears, as will be discussed hereinafter, are preferably of the locking type. In addition, the engine is provided with a chain drive in a chain box 32 driving a longitudinal shaft 34, which is connected by another chain box 36 to a hydraulic pump 38 and a pneumatic pump 40.

The tractor additionally preferably comprises a cab 42 Within the cab there is disposed a steering wheel 44, the front wheels 26 of the tractor being steerable. Also within the cab is an operators seat 46, a foot pedal control 48, and a hand lever control 50, all as will be discussed hereinafter in greater detail.

The trailer or scraper 24 is mostly of conventional construction including a yoke 52 having a gooseneck at the forward end thereof, and having supported at the forward end thereof in conventional fashion a pair of wheels 53. The wheels are rotatable, and also are pivotally or steerably mounted. A bowl 54 is pivotally mounted adjacent the rear wheels at 55, on the opposite sides of the bowl. The bowl is additionally connected to a frame 56. Within the bowl there is conventionally positioned a scraper blade 58. An ejector 60, comprising a floor 62 and a back wall 64 is pivotally mounted at 66 on the scraper blade. The ejector 60 is provided with ejecting mechanism 68 which is fully described and claimed in the co-pending application of James T. Monk, S.N. 717,706, filed February 26, 1958, for Scraper, now U.S. Patent No. 2,965,988. Briefly, this ejecting mechanism comprises a generally L-shaped link 70 having an upper horizontal arm pivotally connected at its rear end at 72 to the upper end of a link 74 which is pivoted at 76 at its lower end of the frame 56. The arm or lever 68 further comprises a generally vertical portion 78 pivoted at its lower end at 80 substantially at the junction of the floor 62 and back wall 64 of the ejector. Finally, a hydraulic actuator or piston 82 is pivotally connected at 84 at its lower end to the frame 56, and is pivotally connected at 86 at its upper end to the more or less vertical portion of the arm 68. Extension of the vertical actuator 82 pivots the arm 68 up with a compound motion to dump from the ejector 60 any dirt or the like within the bowl. Obviously, the weight transfer mechanism can be similar to that disclosed in Simmons 2,899,004, and the front wheels of the tractor can be driven as well as the back ones.

The bowl is provided at the forward end with hydraulic actuating mechanism 87 operable between the bowl and the upper forward portions of the yoke 52. This hydraulic mechanism is provided for lowering the bowl to the position shown in FIG. 1 wherein the scraper blade 58 will scrape up dirt from the ground. Conversely, it may be used to raise the bowl to traveling position away from the ground, as in FIG. 3.

The trailer or scraper is connected at the front end by means of a draw bar 88 to the tractor 22. The draw bar may be a straight through bar, or of the A-shaped variety, and is connected to the steering mechanism (not shown) of the trailer or scraper. At the front end the draw bar 88 is connected for vertical pivoting at 90 to a member 92 connected for horizontal pivoting at 94 to a hitch or clevis 96 on the back of the tractor.

In addition to the foregoing, the tractor is hitched to the trailer by means of a hydraulic actuator cylinder arrangement 98 which is connected at its lower front end to a pin 100 for vertical pivoting of the diagonally disposed actuator. The pin 100 is received in a member 102 mounted for horizontal pivoting about a pin 104 fixed at the rear of the tractor immediately above the clevis 96. The upper end of the actuator 98, comprising the piston or ram 106 has a pin 108 therein horizontally disposed in the lower end of a clevis 110 pivoted on a diagonally disposed pin 112 in a bracket 114 at the upper front end of the yoke 52. When the ram 106 of the hydraulic actuator 98 is extended,a substantial vertical component of force is developed which tends to lift the front end of the trailer relative to the rear end of the tractor. Accordingly, a substantial portion of the weight of the trailer is transferred to the rear wheels 28 of the tractor, thereby causing them to flatten out to a considerable extent, and to provide better traction. As will be understood, the wheels 53 generally are not lifted completely from the ground, but the front of the trailer is lifted sufliciently that the tires tend to round out from their normal somewhat flattened condition.

In addition to the foregoing, an engine 116 of suitable construction is supported at the rear of the trailer or scraper by any suitable means, such as supports 118. A transmission in a transmission housing 120 is fixed on the engine forwardly thereof, and drives a chain in a chain box 122. The engine and transmission are located substantially on the longitudinal median line of the trailer, and in this connection it will be understood that the arm 70 and associated parts of ejecting mechanism 68 is duplicated, there being one on each side of the trailer. The chain in the chain box drives a pinion 124, which in turn drives the ring gear 126 of a differential gear set 128. The difierential gear set is of the locking type, such as one having an axially shifted clutch element. Such differential gear sets are shown, for example in Mayer et al. 1,212,795 and in Miller 1,142,831. The differential gear set of the tractor (not shown) preferably is of the same locking type. The differential gears at 128 drive the two halves of the axle 130, and these in turn drive the rear wheels 132 of the trailer.

The chain drive can be eliminated in favor of gear drive by placing the transmission below the engine. The pinion 124 thus will engage the ring gear at the rear thereof, the rear end of the transmission being directly gear driven from the rear end of the engine.

Turning now to FIG. 4, the transmission (not shown) of the trailer 24 driven by the engine 116 is provided with a shifter element 134 shown somewhat schematically as a vertical bar 136 and a horizontal actuator 138. The various gear positions are indicated schematically by vertical lines adjacent the free end of the actuator 138. A spring 140 connected to the shifter 134 and to a fixed point 142 tends to hold the shifter in retracted position, which would correspond to reverse. A pneumatic cylinder 144 has a piston 146 therein which is biased by a spring 148. The piston rod 150 bears against the vertical bar 136, and the spring 148 is stronger than the spring 140, whereby to hold the shifter in neutral position.

The control of the trailer transmission further includes a first gear cylinder 152. This cylinder contains a piston 154 normally held in a retracted position by spring 156 surrounding the piston rod 158. When the piston is shifted to the right, the piston rod will engage the rod or bar 136 to move the actuator 138 to the first gear position.

There is a similar piston-cylinder arrangement 160 for the second gear position, and having a piston rod 162. The device 160 has a longer stroke, whereby to move to the second gear position. Similarly, there are third and fourth gear piston-cylinder devices, respectively indicated at 164 and 166, and respectively having

piston rods

168 and 170. The strokes of these two devices are progressively longer than the first two, and respectively serve to shift the gear shifter or selector 134 to the third gear and the fourth gear position.

An air control valve 172 is mounted in the cab 42 of the tractor 22 in a convenient position to be operated by the driver. The valve includes an air supply line 174 connected to the air compressor 40. The line 174 is connected to a relatively long arcuate valve port 176. The valve port is in a fixed valve body (not shown), and confronts a valve disc 178 having an operating lever or handle 180 thereon. The valve disc is provided with a diametral bore or passageway 182. The valve 172 is shown in full lines in the forward position, and the diametral passageway or bore 182 extends from the valve port 176 into alignment with an air line 184 extending to a junction at 186, as will be discussed hereinafter.

The valve disc 178 is provided in the upper right quadrant thereof with an elongated recess 188 which communicates with a reverse air line 190, except when the operating handle or lever 180 is in the reverse position. The reverse air line 190 communicates with the right end of the reverse cylinder 144. The recess 188 normally communicates with an exhaust line 192, with the operating lever or handle 180 in either the forward or the neutral position. The exhaust line 192 is never aligned with the diametral bore 182, as this would allow loss of pressure through the exhaust line. When the operating lever 180 is moved to the reverse position, then the bore 182 lines up with the reverse line 190, the bore 182 remaining in communication with the port 176. Accordingly, compressed air is applied to the right end of the cylinder 144, thereby retracting the piston 146 against the spring 148. This allows the spring 140 to retract the shifter or selector 144 to the reverse position.

The junction 186 is connected through an air line 194 to the air cylinder 196 of a governor unit 198 mounted at the back of the trailer or scraper. The governor unit is provided with a shaft 200 having a gear 202 thereon which is geared in any suitable manner (not shown) to the axle 130 to provide a function of the ground speed of the trailer. A fly-ball mechanism 204 is mounted on the shaft 200, and includes balls 206 which will centrifuge 6 outwardly as the shaft is rotated. The balls are conveniently integral with pivotally mounted levers 208 having hook shaped portions 210 underlying the bottom race of a ball bearing 212. The ball bearing is similar to a clutch throw-out bearing, and is arranged to lift a flange 214 at the top of a non-rotating shaft or stem 216. This shaft or stem is normally urged down by a spring 218 compressed between the flange 214 and an axial 'thrust bearing 220 mounted within the fly-ball unit 204. As the balls 206 centrifuge, the shaft or stem 216 will be lifted thereby, the distance depending on the speed of rotation of the balls. The shaft or stem is shown in its lowest position.

The shaft or stem 216 is provided relatively near its lower end with a flange 222 serving as a piston or closure member, and sliding closely within the cylinder 196. Below the flange 222, the shaft or stem extends out wardly through a transverse wall 224 in the cylinder. An axial bore 226 extends from the lower end of the stem to a position above the wall 224, and communicates with a lateral bore 228 opening at the side of the stem above said wall 224.

The sidewall of the cylinder above the transverse wall 224 is provided with a series of ports respectively numbered 230, 232, 234, 236 and 237. The port 230 is connected by an air line 238 to the left end of the first gear piston 152. The port 232 is connected by an air line 240 to the left end of the second gear cylinder 160. Similarly, the port 234 is connected by an air line 242 to the left end of the third gear cylinder 264. The port 236 is connected by an air line 244 to the left end of the fourth gear cylinder 166. The port 237 will be discussed hereinafter. The top of the cylinder 196 opens to the atmosphere about the shaft or stem 216. Accordingly, the

lines

240, 242 and 244 are automatically vented or exhausted to atmosphere as the stern 216 moves down.

As heretofore noted, the rest position of the fly-ball governor mechanism is such that the flange 222 lies above the transverse wall 224. Thus, the transmission is in first gear or higher any time the air control valve 172 is shifted to the forward position. As the trailer is moved faster and faster the balls 206 fly out farther, and the shaft or stem 216 is raised farther, whereby successively to uncover the

ports

232, 234, and 236, to effect shifting into the higher gears.

Neutral position is attained by shifting the valve 172 to neutral position, air is exhausted from the first gear cylinder 152 through line 238, through the cylinder 196 and

lines

194 and 184 to valve 172, and out through an exhaust line 239.

The junction 186 is connected through an air line 246 to an arcuate port 248 in a fixed valve body (not shown) of an air control valve 250. The air control valve comprises a disc 252 rotatable about its center by means of a lever or handle 253. An air line 254 leads from the valve 250, which will be understood as being in a convenient location in the cab of the tractor, to an air cylinder 256 having a piston rod 258 extending therefrom into engagement with a control member 260 for effecting locking and unlocking of the differential of the trailer. The control member, for example, may comprise a shifter fork or the like. By and large, it is desired that the differential of the tractor be locked at the same time as is the differential of the trailer, and to this end there is a lateral air line 262 leading from the air line 254 which connects to an air cylinder controlling the differential lock for the tractor.

The air line 254 is illustrated as leading from the top of the air control valve 250. Another air line 264 leads from the left side of the air control valve, at a location displaced from the line 254. The air line 264 leads to an air cylinder 266 which controls through its piston rod 268 a weight transfer valve 270. The weight transfer valve 270 is a hydraulic valve for admitting hydraulic fluid to the weight transfer cylinder 08. This valve is also shown in FIG. 2, as is the air cylinder 266. In addition, the control lever 50 previously mentioned is connected to operate the weight transfer valve 270 when it is desired to operate the weight transfer valve without use of the differential looks or trailer drive.

The valve disc 252 of the control valve 250 is provided with a radial bore 272 which at all times communicates with the arcuate port 248. A radial bore 274 aligned with the 'bore 272 connects with the air line 264 with the valve disc in the position shown. As will be understood, the two

bores

272 and 274 communicate with one another. They also communicate with a right angularly disposed bore 276 which, in the position shown, communicates with the air line 254. Thus, in the valve position shown, the

air cylinders

256 and 266 are energized, respectively, to lock the differentials and to energize the weight transfer valve for transferring the weight of the front end of the trailer to the back end of the tractor.

In addition, there is an intermediate radial bore 278 communicating with the nlet boe 272, for supplying air under pressure to only the air cylinder 256 for locking the differentials independently of the weight transfer valve. Similarly, there is another bore 280 communicating with the bore 272 which, for yet another position of rotation of the valve disc 252 by the handle 253 communicates with the air line 264 in order to energize the cylinder 266, for energizing the weight transfer valve 270 independent of locking of the differentials. The disc is also provided with suitable intervening exhaust ports 282 to bleed air from the

cylinders

256 and 266 when they are not energized.

Wtih the air control valve 250 in the position shown, and with the air control valve 172 shifted to the forward position, as shown, the weight transfer feature is provided, the differentials are locked, and the rear wheels of the trailer are driven, as are the rear wheels of the tractor by the conventional transmission. Of course, as will be understood, the transmission of the tractor could be shifted in the same way as that of the trailer, by an identical mechanism.

It has been noted heretofore that preferably the weight transfer feature is shut off and the differentials are unlocked when the tractor-trailer combination operates above a certain speed. An automatic control for effecting this is shown in FIG. 4a. The other parts remain as heretofore described, but an air control valve 284 is interposed in the air line 246. The valve 284 includes a disc 286 having a diametr-al bore 288, which normally leaves the air line 246 in a straight-through connection, as heretofore disclosed without the valve. An air cylinder 290 is connected to the disc by a piston rod 292, which is movable to the left to shift an exhaust port 294 into communication with the left portion of the air line 246, the right or pressure portion being cut off by the valve disc 286. The air supply to the cylinder 290 is indicated at x in 4a, and in FIG. 4 there is a branch air line x on the air line 242. Accordingly, whenever the fly ball governor reaches the third gear position, pressure will be applied through the branch line x to actuate the cylinder 290, and hence to deactivate the weight transfer feature and the differential locks. In this illustration, the weight transfer and differential locks are denergized at any speed above second gear (about 10 m.p.h.). However, the cylinder 290 could be actuated from other air lines to change the speed at which the weight transfer and differential locks are deenergized.

Arrangements also can be made for shifting the transmission of the trailer engine 116 into neutral once maximum speed has been attained. Thus, as is shown in FIG. 417, an air cylinder 296 is arranged to shift the disc 178 of the air control valve 172 from the forward position shown to the neutral position. This is done by means of an air supply line from port 237 in FIGI 4 to the cylinder 296 in FIG. 4b. Of course, once the transmission has been shifted into neutral the air control valve 172 will have to be manually reset to the forward position if it is desired for the trailer engine to effect driving of the trailer. Desirably, at the same time as the transmission is shifted to neutral, the engine 116 is dropped to idle speed. As will be understood, both supply lines x and y preferably are provided with manual shutoff valves so that all of the features, namely trailer drive, weight transfer, and differential locking may be utilized at maximum speed, if so desired. Furthermore, a manual shut-off valve is included in line 194 for independent operation of the weight transfer and differential locks. The valve 195 is of the same type as valve 284 (but is manually operated), having an air exhaust port from the governor, but is shown schematically in FIG. 4 for the sake of convenience.

Desirably, the speed of the trailer engine 116 is varied with that of the tractor engine 30. To this end, as is shown in FIG. 5, a pneumatic valve 298 is arranged beneath the floor board 300 of the tractor cab. A valve stem or plunger 302 projects up through the floor directly beneath the accelerator pedal 48. The accelerator pedal, as will be understood, is connected to the tractor engine 30 in any conventional fashion. The valve 298 is provided with an air pressure supply line 304, and with an outlet line 306 which extends to an air cylinder 308 on the trailer adjacent the engine 116. The piston rod 310 is connected to the fuel supply of the engine 116, or is otherwise connected to any suitable speed control mechanism of the engine. As the accelerator pedal 48 is depressed, it depresses the plunger 302, and hence opens the valve 298 farther. The farther the valve is open, the more pressure is supplied through the line 306 to the cylinder 308, whereby to move the piston rod 310 a greater distance, thus to speed up the engine 116. Alternatively the pedal 48 in FIG. 5 may be an independent to allow independent control of the tractor and trailer engines.

The present invention is adapted for electric drive of the trailer. Accordingly, as shown in FIGS. 6 and 7, an electric generator 312 is provided in the tractor, and is driven by the chain box 36a. Most of the parts remain as heretofore described, and similar numerals are utilized with the addition of the suffix a to obviate duplication of description. Individual electric motors 314 are provided for each of the rear wheels 132a, and a cable 316 leads from the generator back to the trailer and to the motors. The wheels preferably are mounted on half axles which rotate independently, and which also may be fixed together at the center of the trailer for rotation as a unit, in the same manner as with the locking differentials, whereby to prevent one of the driving wheels 132a from spinning. However, this is not as critical a problem as it is with a differential drive, since power will still be applied to the non-spinning wheel since little power is taken from that available at the generator to spin a wheel which starts to slip in poor traction material. Means for controlling the speed of the electric motor 314 is shown in FIG. 7. Thus, within the cab there is provided an additional foot pedal 318. This may be selectively locked to the accelerator pedal 48, or it may be placed directly side by side therewith so that both pedals may be depressed simultaneously with one foot, while only the accelerator pedal 48 need be depressed for highway or high speed driving. A battery 320 is provided, and one terminal of the battery is connected to the resistor 322 of a rheostat 324 including also a slider or brush 326 movable with the foot pedal 318. The slider or brush 326 is connected by a wire 328 to one end of the field coil 330 of the generator 312. The other end of the field coil is connected by a wire 332 back to the other terminal of the battery 320. As will be appreciated, the further the pedal 318 is depressed, the less will be the resistance of the rheostat 324, and hence the greater will be the energization of the field coil 330. Obviously,

the greater will be the voltage and power from the generator 312 through the cable 316 to the motors 314.

The embodiments of the invention have involved the provision of either a motor or an engine on the trailer. This is not essential, as mechanical linkages can be provided from the tractor, as is hereinafter described in connecttion with FIGS. 8-10. The machine is by and large similar to that heretofore shown and described, and similar numerals are utilized to identify similar parts with the addition of the sufiix b. For clarity of illustration, certain parts have been omitted, such as the wheels on the near side in FIG. 8, and the ejecting or dumping mechanism. In FIG. 9, certain parts of the supporting frame have been omitted for clarity.

More specifically, the tractor 22b has a propeller or drive shaft 334 with a pinion 336 thereon driving the ring gear 338 of a differential in order to drive the axle on which the rear tractor wheels 28b are mounted. In addition, the ring gear drives a pinion 340 mounted on the back side thereof, and fixed on a shaft 342. This shaft is connected through a power connect-disconnect unit 344 to a stub shaft 346. The unit 344 may, for example, be a clutch which is mechanically or hydraulically controlled from the cab, as by a pedal or a lever readily accessible to the operator.

The stub shaft 346 carries a bevel gear 348 which meshes with a bevel gear 350 pivotally mounted about a common axis with the horizontal pivot of the weight transfer mechanism linkage 98b and with the horizontal pivot of thed raw bar 88b. The bevel gear 350 meshes with and drives a bevel gear 352 fixed on a shaft 354 including a number of universal joints to drive a bevel gear 356. The bevel gear 356 meshes with a bevel gear 358 coaxial with the steering axis of the front wheels 53b of the trailer or scraper 24b. The bevel gear 358 is fixed on a vertical shaft 360 having a bevel gear 362 at the top thereof meshing with a bevel gear 364. The bevel gear 364 is connected through a universal joint 366 to a shaft length 368 leading rearwardly and downwardly, as well as off to one side along the frame member 52b. The shaft length 368 is connected through additional universal joints and shaft lengths, lumped together under the numeral 370, to a bevel gear 372 at the top rear center of the machine. This bevel gear meshes with a level gear 374 mounted on a semi-vertical shaft 376. This shaft drives a torque limiting device 378 which acts through a universal joint to drive a speed reducer 380. The speed reducer acts through a power connect-disconnect unit 382 to drive a bevel gear or pinion 384. The unit 382 is similar to the unit 344, and may be operated at the same time by a hydraulic or pneumatic throw out system. The pinion 384 drives the ring gear 386 of a differential driving the rear wheels 13212 of the trailer or scraper. Preferably, the differential is a locking type differential, as heretofore discussed.

It will now be apparent, as long as the

power connectdisconnect unit

344 and 382 are in connect position, the rear wheels 1321: of the trailer are driven at the same speed as the rear Wheels 28b of the tract-or. No problems of shifting gears or the like are involved, since both sets of wheels are driven through the tractor transmission from the tractor engine. Once the vehicle has come to speed, the power connect-disconnect units are shifted to the nondriving or disconnect position, so that the trailer is simply towed by the tractor. Preferably, means is provided whereby the weight transfer mechanism is actuated simultaneously with the power connect-disconnect units, and this obviously can be by means of mechanisms such as those heretofore shown and described.

Certain advantages can be obtained by driving the front wheels of the trailer, as well as the rear wheels, and mechanism for this purpose is disclosed in FIGS. 10 and 11. The apparatus in these two figures is substantially identical with that in FIGS. 8 and 9, and similar numerals are used with the addition of the sufiix c. The essential difference in the present form of the invention is that the vertical shaft 3600 at the front of the trailer has a worm 388 thereon. A clutch mechanism 390 is provided for selectively locking the worm to the shaft 3600 for rotation therewith, or for idling thereon. The clutch mechanism desirably is controlled by a hydraulic or pneumatic connection from the cab of the tractor, as by an air valve similar to those previously described in connection with FIG. 4. The worm 388 drives a worm gear 392 on an offset cross-shaft having a pair of pinions 394 thereon which respectively drive gears 396 on the half axles supporting and driving the wheels 53c of the trailer or scraper. As will be apparent, the clutch mechanism 390 may be connected to operate concurrently with the weight transfer and rear axle drive, if so desired. However, preferably the front wheel drive, as controlled by the clutch 390, is independently controlled, as will be brought out hereinafter in connection with a description of the operational advantages of front wheel drive.

In some instances, as in coal mining, it is desirable to move a trailer into a restricted space or area from which it cannot be turned around for removal. Vehicles of this size are not at all adapted to being backed up, and accordingly, it is desirable that a tractor can be attached to either end of such a trailer, whereby the trailer can be pulled in by a tractor, the tractor can be disconnected, and the tractor can subsequently be connected to the opposite end of the trailer to pull it from place once it has been loaded. As will be apparent, if such a tractor-trailer combination is to be used with weight transfer and rear wheel drive of the trailer, some means must be provided for more or less rendering the trailer symmetrical at both ends. Thus, there is shown in FIGS. 12 and 13 a further embodiment of the invention wherein the parts are generally the same, and wherein similar parts are identified with numerals similar to those heretofore used, with the additional of the suffix d. Specifically, the tractor 22d remains substantially as heretofore shown and described. The trailer 240. is specifically illustrated as being a coal hauler which is loaded from the top, and dumps from the bottom. The front wheels 53d are provided in tandem, as are the back wheels 132d. Actually, the front wheels are mounted on a truck 398 carrying the front end of the trailer, while the rear wheels are mounted on a truck 400 carrying the rear end of the trailer. It will be understood that reference to the front and rear end of the trailer is purely nominal, since the trailer is reversible. The trailer is provided at the front end with a hitch 402 for the draw bar 88d. A spring 404 is stretched between the draw bar and a turn buckle or other adjustment device 406, whereby the draw bar will be raised above the ground when it is released from the coupling 92 to the tractor. A similar spring 404 and turn buckle 406 are provided at the rear end of the trailer.

At a higher elevation on the front end of the trailer there is provided a coupling 408 for the weight transfer ram or cylinder mechanism 98d. A similar mechanism 408 is provided at the rear of the trailer. The foremost of the front wheels 53d is provided with an electric motor 410. A chain in a chain box 412 may drive the rearmost of the two wheels in synchronism with the foremost one. As will be understood, one such electric motor is provided on each side. A cable 414 runs from the motors 410 to a separable connection 416 at the rear of the trailer. Normally the front motor thus is not energized. Similarly, the rearmost of each tandem set of rear wheels 132d is provided with an electric motor 418. The foremost of each tandem pair of rear wheels may be driven by a chain in a chain box 420. A cable 422 extends from the motors 418 to a separable connection 424. A flexible cable 426 is detacha'bly connected to the connection 424, and leads from the generator 312d in the tractor.

Thus, the rear wheels of the trailer are driven the same manner as previously described in connection with FIGS. 6 and 7. When the tractor has pulled the trailer, with or without rear wheel drive of the trailer, into a desired loading position, the tractor readily is separated from the trailer simply by detaching the connections at 92d and at 408, along with the detachable electric connection 424. The tractor then is driven around to the opposite end of the trailer. The detachable draw bar connection 92d associated with the draw bar 88d at the rear end of the trailer is connected, the weight transfer connection is made at 408, and the cable 426 is plugged in at 416. The tractor and trailer then are driven away with the trailer moving in the reverse of its initial position, and with the now rear wheels ready to drive as desired.

It will now be apparent that there has been described in connection with several different modifications an earth moving machine or the like comprising in combination a two-axle or four-wheel prime mover or tractor with usually two of the four wheels driving, a trailer attached to the prime mover by draft or draw bar means, wherein the trailer has at least two axles with means provided for selectively driving at least one of the axles, and further including means for transferring weight from the trailer to the prime mover. In addition, means is provided for either independent or concurrent operation of the trailer drive, weight transfer, and differential lock. In the preferred form of the invention, a common control lever is provided for the transmission as well as for the trailer drive, weight transfer, and ditferential locks.

In a typical earth moving machine constructed in accordance with the principles of this invention, the following weight distribution is obtained with the use of the weight transfer feature:

EMPTY Prime Mover Trailer Total Weight Front Rear Front Rear Axle Axle Axle Axle Percentage 10. 45 36. 58 26. 48 26. 48 No Weight Transfer- 15, 000 52, 500 38,000 38. 000 143, 500 100% Percentage 10. 45 50. 52 4. 60 34. 42 With Weight Transfer 15, 000 72, 500 6,600 49, 400 143, 500 100% LOADED Percentage 5. 74 20. 11 33. 43 40. 71 No Weight Transfer- 15, 000 52, 500 87,300 106,300 261, 100 100% Percentage 5. 74 37.70 5. 81 50.74 With Weight Transfer 15, 000 98, 446 15, 164 132, 490 261,100 100% With the vehicle empty, and with no weight transfer, but with both the rear tractor and trailer wheels driving, it has been found that the draw bar pull of the tractor will amount to 28,875 pounds. The equivalent horizontal force, which for convenience will also be referred to as draw bar pull of the trailer amounts to 20,900 pounds. This gives a total draw bar pull of 49,775 pounds. In arriving at these figures, it must be borne in mind that sufiicient horsepower is provided for maximum tractive effort. The limiting factor is the gripping of the ground by the tires. It has been found that with an empty vehicle, the tractive coefficient of the tires will typically be .55 for both the trailer and for the tractor. The term tractive coefficient is used, since the factor involved is not truly a coefficient of friction, inasmuch as the tires flatten out to a certain extent to conform with the ground or terrain, thereby providing a gripping action in addition to friction.

Now when weight transfer is used, the rear wheels of the tractor are flattened out to a rather considerable extent, increasing the tractive coefficient to- .7 4. At the same time, the load on the tractor rear wheels, with the trailer empty, is increased to 72,500 pounds. A draw bar pull of 53,650 pounds thus is produced by the tractor. A simple addition of this 53,650 pounds and the previous draw bar pull of the trailer of 20,900 pounds would provide a total of only 74,550 pounds. However, with the combination of weight transfer and drive of the rear trailer wheels, the total draw bar pull or tractive force is actually 80,820 pounds, nearly ten percent greater than that which would be initially expected. This is due to the fact that the weight transfer also shifts a certain amount of the Weight of the trailer from the front wheels to the rear wheels of the trailer. In fact, in accordance with the table above, the weight on the rear wheels of the trailer becomes 49,400 pounds. Combined with the previously mentioned tractive coeflicient of .55, the draw bar pull of the rear wheels of the trailer is 27,170 pounds, an increase of 6,270 pounds over the tractive power of the trailer without weight transfer.

The improvement is even more marked with a loaded vehicle. With the loaded vehicle, and with no weight transfer but with the rear tractor wheels and the rear trailer wheels driving, the rear tractor wheels again provide a draw bar pull or tractive force of 28,875 pounds. However, since the rear wheels of the trailer now have 106,300 pounds on them, the trailer produces a draw bar pull or tractive force of 58,465 pounds. Thus, the total tractive force is 87,340 pounds.

With weight transfer, the tractive coefiicient of the tractor rear wheels again becomes .74, which times the 98,446 pound weight now on the rear tractor wheels produces a tractive effort or draw bar pull of 72,850 pounds. If the trailer tractive effort remains at 58,465 pounds as before weight transfer, the total tractive effort would be 131,315 pounds. However, since a part of the weight of the front wheels of the trailer is again trans ferred to the rear wheels, the trailer exerts a tractive force or draw bar pull of 72,869 pounds, thus producing a total tractive effort of the combination of 145,719 pounds. This produces an improvement of 14,404 pounds over the arithmetic sum of rear trailer wheel drive and tractor drive with weight transfer, over ten percent.

Thus, it will be seen that the combination of weight transfer and rear axle trailer drive produces more than a simple sum of the benefits of each.

It is appreciated that the coefficient of friction is determined by the nature of two contacting materials, and that at least theoretically the coefiicient of friction is independent of the area of force. However, the tractive coeflicient as used herein is not so limited. This is because the increased weight on the rear wheels of the tractor causes the tires to flatten out to a rather marked extent, thereby gripping the surface of the ground or terrain. Under adverse conditions, the very time when increased traction is desired, the surface of the terrain is apt to be quite irregular, hence providing better opportunity for gripping by the flattened out tires. A common example of this effect which is known to almost everyone is that when an automobile is stuck in sand, or sometimes on ice or in snow, it often can be driven away simply by letting a substantial amount of air out the rear tires. Since weight transfer greatly reduces the weight on the front wheels of the trailer, a superficial approach might well question the advantages of the combination of four-wheel trailer drive with weight transfer. It is believed that all that is necessary to support the advantage of this combination is to point out that the differen wheels of the combination may at any given time encounter different tractive conditions. For most circumstances, the combination of weight transfer and rear wheel trailer drive is excellent. However, it will be appreciated that there are circumstances in which little or no tractive effort could be applied by either the rear tractor wheels or the rear trailer wheels, should these wheels be in slick spots resulting from mud, ice, or the like, while the front trailer wheels might at the same time be on material of relatively good traction. In this instance, it is most desirable that the front trailer wheels be able to exert a tractive force. Of course, under such cir- 13' cumstances the weight transfer feature would be deenergized in order to leave as much weight as possible on the front .wheels of the trailer.

It has been observed heretofore that it is desirable to deenergize the weight transfer means, while still utilizing trailer drive. For example, when making a sharp turn of such nature that the tractor is at 90 to the trailer, energization of the weight transfer means has a tendency to tip the trailer. Obviously, under such circumstances it is desirable that the weight transfer feature be deenergized.

It is desired that the weight transfer system be switched out or deenergized at high speeds for at least two reasons. Although soft low-pressure tires can carry a rather substantial load at low speeds, if the weight transfer feature were utilized at high speeds terrific overloads would be imposed on the tractor drive tires, resulting in quick destruction of these tires. The soft low-pressure tires can be used on the tractor or prime mover since weight transfer is used only at low speeds, and since the tires have to carry only relatively low weight at higher speeds.

In addition, once the earth mover or the like has reached a speed where maximum traction and draw bar pull are no longer needed, it is undesirable to continue the weight transfer since the large portion of the trailer loads supported on top of the prime mover or tractor would result in great pounding and surging action on the tractor at high speeds, leading toshort service life.

In considering the generic nature of the present invention, it must be borne in mind that the tractor has two axles, the rearmost of which is always driven. The trailer has at least two axles, with provision for driving at least the rear axle thereof. To this end, the trailer is always provided with some sort of power means, whether it comprises an independent internal combustion engine, or electric motors driven by a generator in a tractor, or mechanical shafts or the like for driving from the engine in the tractor. Means is provided for transferring a part of the weight of the trailer onto the rear wheels of the tractor, and for simultaneously increasing somewhat the weight on the rear wheels of the trailer. In addition, locks are provided for the differentials of the tractor and the trailer drive axles. Common control means, in one example the gear shift lever, is provided for controlling simultaneously the trailer drive, the weight transfer, and the differential locks. However, individual control is also provided for to meet the exigencies of nearly every possible situation of traction.

It will be understood that the various examples of the invention as herein shown and described are for purposes of illustration only. Various changes in structure will no doubt occur to thosevskilled in the art, and will be understood as coming within the ambit of the present invention insofar as they fall within the spirit and scope of the appended claims.

This invention is claimed as follows:

1. A machine for moving earth and the like comprising a tractor having drive wheels, a power source and means for driving said drive wheels from said power source, means providing an operators station on said tractor, a trailer having front and rear wheels, power means on said trailer for selectively driving said trailer rear wheels, draft means interconnecting said trailer and said tractor for pulling of said trailer by said tractor, means interconnecting the rear of said tractor and the front of said trailer and operative for transferring at least a part of the weight of said trailer from said front to said rear wheels thereof and also to said drive wheels of said tractor, and

control means at said operators station of said tractor operatively connected to said weight transfer means and to said trailer power means for selectively operating said weight transfer means and said power means, means operatively interconnected with at least one of said wheels of said machine and providing a response proportional to the speed of said machine, and means operatively connected to said speed response means and to said weight transfer means and operable automatically to deenergize said weight transfer means when said machine reaches a predetermined speed.

2. A machine as set forth in claim 1 wherein said tractor includes a differential through which the tractor rear wheels are driven, means for locking said differential, and control means at the operators station for controlling said differential locking means, wherein the means operatively connected to the speed response means includes means for disabling said differential locking means when said machine reaches a predetermined speed.

3. A machine as set forth in claim 2 wherein the trailer also includes differential locking means, and further including means for operating said trailer differential locking means in synchronism with said tractor differential locking means.

4. A machine as set forth in claim 1 and further including means operatively connected to said speed response means and to said trailer power means and operable automatically to render said trailer power means ineffective when said machine reaches a predetermined speed.

5. A machine for moving earth and the like comprising a tractor having drive wheels, a power source and means for driving said drive wheels from said power source, means providing an operators station on said tractor, a trailer having front and rear wheels, fluid controlled power means on said trailer for selectively driving said trailer rear wheels, draft means interconnecting said trailer and said tractor for pulling of said trailer by said tractor, fluid controlled means interconnecting the rear of said tractor and the front of said trailer and operative for transferring at least a part of the weight of said trailer from said front to said rear wheels thereof and also to said drive wheels of said tractor, and fluid control means at said operators station of said tractor operatively connected to said weight transfer means and to-said trailer power means for selectively operating said weight transfer means and said power means, said fluid control means comprising a source of fluid under pressure, a first valve connected to said source, a second valve, means connecting said first valve to said second valve, exhaust means, said first valve having an operative position connecting said source to the valve connecting means and in inoperative position connecting said source and said valve connecting means to said exhaust means, means connecting said valve connecting means to said trailer fluid controlled power means to render said trailer power means effective with said first valve in operative position, and means connecting said second valve to said fluid controlled weight transfer means, said second valve having an operative position connecting said valve connecting means to the means connecting said second valve to said fluid controlled weight transfer means to operate said weight transfer means with both said first valve and said second valve in operative positions.

6. A machine as set forth in claim 5 and further includingmeans operatively interconnected with at least one of the wheels of sail machine and providing a response proportioned to the speed of said machine, and means operatively connected to said speed response means and to said first valve and operable to move said first valve to inoperative position when said machine reaches a predetermined speed, thereby to render said fluid controlled weight transfer means inoperative.

7. A machine as set forth in claim 6 and further including means operatively connected to said speed response means and to said valve connecting means to block said valve connecting means from communication with said means connecting the second valve to the fluid controlled weight transfer means when said machine reaches a predetermined speed.

8. A machine as set forth in claim 7 wherein the blocking means comprises a third valve in the valve connecting means disposed between the second valve and the connecting means connected to the trailer fluid controlled power means.

9. A machine as set forth in claim 7 wherein said blocking means operates at a lower predetermined machine speed than the predetermined machine speed at which the first valve moving means operates.

10. A machine as set forth in claim including means operatively connected to said speed response means and to said valve connecting means to block said valve connecting means from communication with said means connecting the second valve to the fluid controlled weight transfer means when said machine reaches a predetermined speed.

11. A machine as set forth in claim 5 wherein at least one of said tractor and trailer has a differential with fluid controlled means for locking said differential, wherein said second valve has a position for connecting said valve connecting means to said differential locking fluid controlled means for selectively locking said differential.

12. A machine as set forth in claim 11 wherein said second valve has operative positions for connecting said valve connecting means to either of said weight transferring fluid control means and to said differential locking fluid controlled means selectively independently of one another and concurrently.

13. A machine for moving earth and the like comprising a tractor having drive wheels, a power source and means for driving said drive wheels from said power source, means providing an operators station on said tractor, a trailer having front and rear wheels, power means on said trailer for selectively driving said trailer rear wheels, draft means interconnecting said trailer and said tractor for pulling of said trailer by said tractor, means interconnecting the rear of said tractor and the front of said trailer and operative for transferring at least a part of the weight of said trailer from said front to said rear wheels thereof and also to said drive wheels of said tractor, and control means at said operators station of said tractor operatively connected to said weight transfer means and to said trailer power means for selectively operating said weight transfer means and said power means, means operatively interconnected with at least one of said wheels of said machine and providing a response proportional to the speed of said machine, and means operatively connected to said speed response means and to said weight transfer means and operable automatically to deenergize said weight transfer means when said machine reaches a predetermined speed, said speed response means including a fluid valve having a plurality of ports and a movable fluid distributing member connecting a source of supply of fluid under pressure selectively to said ports, said member moving to different distributing positions according to the speed of said machine, said weight transfer deenergizing means being connected to one of said ports.

14. A machine as set forth in claim 13 and further including means connected to one of said fluid valve parts for rendering said trailer power means. ineffective to drive said trailer rear wheels when said machine reaches a predetermined speed.

15. A machine for moving earth and the like comprising a tractor having drive wheels, a power source and means for driving said drive wheel from said power source, means providing an operators station on said tractor, a trailer having front and rear wheels, power means on said trailer for selectively driving said trailer rear wheels and including a transmission having neutral and drive positions, draft means interconnecting said trailer and said tractor for pulling of said trailer by said tractor, means interconnecting the rear of said tractor and the front of said trailer and operative for transferring at least a part of the weight of said trailer from said front to said rear wheels thereof and also to said drive wheels of said tractor, and control means at said operators station of said tractor operatively connected tov said Weight transfer means and to said trailer power means for selectively operating said weight transfer means and said power means, means operatively interconnected with at least one of said wheels of said machine and providing a response proportional to the speed of said machine, and means operatively connected to said speed response means independently of said tractor power source and to said transmission and operable automatically to shift said transmission to neutral when said machine is operated above a predetermined minimum speed, said speed response means including a fluid valve having a plurality of ports and a movable fluid distributing member connecting a source of supply of fluid under pressure selectively to said ports, said member moving to different distributing positions according to the speed of said machine, said means for shifting said transmission to neutral being connected to one of said ports.

16. A machine as set forth in claim 15 and further including means for deenergizing said weight control means when said machine reaches a predetermined speed, said deenergizing means being connected to one of said ports.

17. A machine as set forth in claim 16 and further including a differential driving the rear wheels of at least one of said tractor and said trailer, means for locking said differential, and means connected to one of said ports for automatically unlocking said differential when said machine reaches a predetermined speed.

References Cited by the Examiner 4/1951 Austria.

BENJAMIN HERSH, Primary Examiner.

PHILIP ARNOLD, A. HARRY LEVY, Examiners.

Claims

1. A MACHINE FOR MOVING EARTH AND THE LIKE COMPRISING A TRACTOR HAVING DRIVE WHEELS, A POWER SOURCE AND MEANS FOR DRIVING SAID DRIVE WHEELS FROM SAID POWER SOURCE, MEANS PROVIDING AN OPERATOR''S STATION ON SAID TRACTOR, A TRAILER HAVING FRONT AND REAR WHEELS, POWER MEANS ON SAID TRAILER FOR SELECTIVELY DRIVING SAID TRAILER REAR WHEELS, DRAFT MEANS INTERCONNECTING SAID TRAILER AND SAID TRACTOR FOR PULLING OF SAID TRAILER BY SAID TRACTOR, MEANS INTERCONNECTING THE REAR OF SAID TRACTOR AND THE FRONT OF SAID TRAILER AND OPERATIVE FOR TRANSFERRING AT LEAST A PART OF THE WEIGHT OF SAID TRAILER FROM SAID FRONT TO SAID REAR WHEELS THEREOF AND ALSO TO SAID DRIVE WHEELS OF SAID TRACTOR, AND CONTROL MEANS AT SAID OPERATOR''S STATION OF SAID TRACTOR OPERATIVELY CONNECTED TO SAID WEIGHT TRANSFER MEANS AND TO SAID TRAILER POWER MNEANS FOR SELECTIVELY OPERATING SAID WEIGHT TRANSFER MEANS AND SAID POWER MEANS, MEANS TO THE SPEED OF SAID MACHINE, AND MEANS OPERATIVELY CONNECTED TO SAID SPEED RESPONSE AUTOMATICALLY TO DEENERGIZE TRANSFER MEANS AND OPERABLE AUTOMATICALLY TO DEENERGIZE SAID WEIGHT TRANSFER MEANS WHEN SAID MACHINE REACHES A PREDETERMINED SPEED.