AU5449500A - Double-acting trailer hitch - Google Patents

Description

WO 00/71368 PCT/USOO/14839 1 DOUBLE-ACTING TRAILER HITCH FIELD OF THE INVENTION This invention relates to a double-acting trailer hitch that requires the use of significantly less tongue weight than is required in previously known trailer hitches and which may be used effectively with trailers having various tongue weights and with tow vehicles having various frame strengths. BACKGROUND OF THE INVENTION During the 1920s and 1930s, trailer hitches began incorporating a hitch ball attached to an extension of the tow vehicle and a ball coupler carried by the forward end of the trailer. The coupler was engaged with the ball so that the tow vehicle could pull the trailer along the highway. A number of developments, including improved highways, more powerful automobiles and trucks, and the advent of electromagnetic trailer brakes allowed the vehicles and attached trailer to achieve greatly increased highway speeds. These developments also permitted much heavier trailers to be towed. The traditional ball hitch was soon found to be unacceptable for handling such increased speeds and trailer weights. In particular, the rig tended to be very unstable. The most significant source of instability was the upward hinging and toggling that occurred between the tow vehicle and the trailer at the point of the coupling ball. This was especially noticeable during braking. At such times, a portion of the linear momentum of the tow vehicle is converted to angular momentum. This causes the front of the tow vehicle to dip WO 00/71368 PCTIUSOO/14839 2 downwardly and the rear of the vehicle to pitch upwardly. In the case of the original ball hitch, the delay in activation of the trailer's electromagnetic brakes caused the significant weight of the trailer to push against the trailer ball. This tended to push the rear of the tow vehicle upwardly with even greater force. The height of the ball at the top of the hinge point effectively formed a toggle with front axle of the tow vehicle and the rear axle of the trailer. Accordingly, the linear momentum of the trailer was also converted into upward force on the ball. The toggle effect was exacerbated when the rig encountered bumps or dips on the highway. All of this made the traditional ball coupling highly unstable and contributed to serious highway accidents. To counteract the instabilities of the original ball hitch, the weight-distributing hitch was introduced during the 1950s. Initially, the upward hinging exhibited between the tow vehicle and trailer was addressed by adding weight to the tongue of the trailer proximate the ball. It was determined that "a tongue weight" of approximately 10 to 15 percent of the gross trailer weight was generally adequate to prevent excessive upward hinging about the trailer ball. However, simply adding tongue weight was and still is, by itself, an inadequate remedy. This weight must be effectively distributed among the axles of the tow vehicle and the trailer so that the rear of the tow vehicle does not sag and a level, stable ride is maintained. Weight distributing trailer hitches that perform this function have been available for many years. Notwithstanding their current widespread use, conventional weight distributing hitches still exhibit a number of disadvantages. The forces that these hitches generate to counteract the heavy tongue weight of the trailer tend to exert significant stress on the suspension of the tow vehicle. As a result, trucks, sport utility vehicles and full frame automobiles normally must be used as the tow vehicle. Smaller automobiles WO 00/71368 PCTIUSOO/14839 3 without a full frame are generally inadequate to support the force produced by the weight-distributing hitch. Such smaller vehicles normally cannot be used to pull a large trailer, which is equal to or heavier than the tow vehicle. Moreover, the heavy tongue weights exhibited in present weight distributing hitches can create serious instabilities when the rig is driven at highway speeds. In particular, during a sudden lane change, which may result when the driver takes evasive action, the tongue weight carried by the overhang of the trailer behind the rear axle of the tow vehicle often creates a large X-axis moment transverse to the direction of travel. This moment can cause the tow vehicle and trailer to jackknife or flip. Serious accidents often result from such instability. Trailer instabilities are inherent at all speeds of travel. At speeds below 40 mph they are usually not yet of such significance as to create unsafe travel. Instability increases as a function of speed of travel. At 50 mph some kind of control must be introduced or it is simply so unsafe that the speed cannot be maintained. The upper threshold of safe travel of a tow vehicle towing a heavy trailer by means of a ball coupler alone is approximately 35 mph for the heavy trailers to approximately 45 mph for lighter trailers. These figures are approximate. The greater the trailer weight is in proportion to the tow vehicle's weight, the lower the speed at which the coupled vehicles can safely travel. The free hinging movement at the trailer ball is also a factor in trailer instability. The height of the trailer ball is another factor, because the higher the ball above the axles of the vehicles, the greater is the upward thrust of the toggle at the ball. Where the ball pitches upward during tow car braking (and before trailer braking is effective due to the magnet delay) the toggle is increased significantly. A heavy WO 00/71368 PCT/USOO/14839 4 trailer thrusting forward on the rear arm of the toggle, and is pushing upwardly on the ball lifts the rear end of the tow vehicle which causes dangerous loss of traction on the road surface. Conventional weight distributing trailer hitches also normally require that the trailer axles be positioned fairly close together and located a significant distance from the trailer tongue. This is needed in order to provide the trailer with the necessary tongue weight. If the trailer axles are positioned close together, optimal trailer stability may not be exhibited. One known trailer hitch designed for use with relatively lightweight frameless automobiles employs a dolly that is mounted beneath the hitch. The dolly travels along the roadway with the rig and supports the tongue weight without distributing the weight to the tow vehicle. This apparatus is unduly complicated and introduces additional wheels that must engage the highway. A failure of the dolly wheels will render the entire rig inoperable.

WO 00/71368 PCT/USOO/14839 5 SUMMARY OF INVENTION It is therefore an object of the present invention to provide a trailer hitch in which tongue weight is not a factor in towing stability, thus permitting the use of a significantly reduced tongue weight. It is a further object of this invention to provide a trailer hitch, which joins the frame of the tow vehicle and the frame of the trailer such that they behave as a single piece along an axis extending in the direction of travel. It is a further object of this invention to provide a trailer hitch that eliminates the upward hinging and toggle action between the tow vehicle frame and the trailer frame so that significantly improved and more stable towing is achieved. It is a further object of this invention to provide a trailer hitch that permits the tongue weight to be greatly reduced so that less stress is placed on the springs and suspension of the tow vehicle. It is a further object of this invention to provide a trailer hitch that reduces the dangerous instability and risk of jackknifing often accompanying evasive maneuvers and sudden lane changes. It is a further object of this invention to provide a trailer hitch, which exhibits extremely stable operation, but without requiring the use of a heavy tongue weight. It is a further object of this invention to provide a trailer hitch that minimizes the transverse moment at the trailer ball and resulting instability caused when a tow vehicle and trailer swerve on the highway. It is a further object of this invention to provide a trailer hitch apparatus that reduces the tongue weight of the trailer so that additional accessories and/or equipment are not required to be mounted to the forward end of the trailer.

WO 00/71368 PCT/USOO/14839 6 It is a further object of this invention to provide a weight distributing trailer hitch apparatus that employs an effective coil spring dampening system to control and reduce bounce and greatly improve ride stability. It is a further object of this invention to provide a weight distributing trailer hitch employing an easy to operate cam that adjusts the hitchhead quickly and reliably so that the hitchhead and the drawbar can be coupled and the tongue weight is properly and evenly distributed to the tow vehicle. It is a further object of this invention to provide a trailer hitch of both the weight distribution kind and the low weight kind which converts the toggling upward force at the trailer coupling (which force is generated by the trailer pushing against the coupling means such as during braking) into a downward force at the coupling and thus causing this force to become a force which increases stability, instead of being a force which increases instability as in previous practice. It is a further object of this invention to provide control of the angular forces of momentum in the tow vehicle during the short period of early braking which occurs before the electric brakes of the trailer become effective. This invention results from a realization that the normally high tongue weights used in weight-distributing trailer hitches may be significantly reduced by employing preloaded, double-acting spring means for dampening the relative movement between the tow vehicles and the trailer about a horizontal (X) axis transverse to the direction of travel. This invention results from the further realization that tongue weight may be reduced and stability improved by pivotably overlapping the forward end of the trailer and the X-axis coupling and joining the drawbar extension of the tow car hitch to the trailer at a point rearwardly of and below the hitch ball. This enables the tow vehicle WO 00/71368 PCT/USOO/14839 7 and trailer to act essentially as a unified beam, which is controlled by a preloaded double-acting spring so that hinging and toggling are eliminated when the rig is driven at highway speeds. Conversely, hinging is allowed to occur between the tow vehicle and trailer when bumps and dips are encountered at low speeds. The overlapping of the drawbar extension and the trailer frame, as well as the use of a preloaded spring assembly also helps to safely control the force of angular momentum normally generated in the tow vehicle during braking. As used herein "double-acting" means that the spring assembly controls both upward and downward motion of the tow vehicle and trailer at their point of interconnection, which is located proximate the rearward end of the drawbar extension significantly behind and below the hitch ball. This invention features a double-acting trailer hitch for interconnecting a trailer to a tow vehicle. The hitch includes a drawbar assembly that is selectively attached to the tow vehicle. A first coupling component is attached to a rearward end of the drawbar. A hitchhead assembly includes a ball element that carries a clevis and is suspended by a ball coupling supported by the trailer. The hitchhead also includes a yoke that is pivotally connected to the clevis by a first horizontal pivot that is axially transverse to the direction of travel. A drawbar extension is interengaged with and extends generally rearwardly from the horizontal pivot. A second coupling component is pivotally connected to the yoke along a generally vertical axis. The second coupling component may include means for interengaging complementary means in the first coupling component such that the first and second coupling components are coupled and the drawbar is held at a predetermined axial angle relative to the ground. There are also means for interconnecting a rearward portion of the drawbar extension to the trailer. Such means for interconnecting may include a horizontal pivot that is substantially WO 00/71368 PCTUSOO/14839 8 parallel to the horizontal axis and perpendicular to the direction of travel. The means for interconnecting further include preloaded double-acting spring means connected to the horizontal pivot for dampening upward and downward movement of the drawbar extension relative to the trailer. While the tow vehicle and trailer travel in a straight line on a relatively level highway, the spring means resist pivoting of the drawbar extension and the tow vehicle and frame move forwardly as a single unified structure. When the tow vehicle engages bumps and dips in the roadway, the preloaded spring means permit the drawbar extension to temporarily pivot relative to the trailer, until the undulation is crossed. The preloaded spring means then return the drawbar extension to its original condition. In a preferred embodiment, the first coupling component is fixedly interconnected to the drawbar. The first and second coupling components may include elements that prevent hinging or pivoting movement between the first and second coupling components. For example, the first coupling component may include an upper and a lower hitchpin hole. The second coupling component may include a horn featuring an upper slot or recess and a lower hitchpin hole. The horn may also include a ramp that is connected to the upper slot. The drawbar assembly may be directed against the horn such that the upper hitchpin rides up the horn and drops into the slot of the second coupling component. The second coupling component may include means for adjusting the height of the second coupling component. Such means may include a vertical channel element that is slidably interengaged with the horn. Means may be provided for interlocking the horn in the channel element at a selected height. The height adjustment allows the user to fine-tune the hitch to accommodate differing tow vehicle heights. Additionally, WO 00/71368 PCT/USOO/14839 9 the drawbar assembly may be constructed so that the first coupling component is disposed at an angle to the drawbar. As a result, the drawbar assembly may be inverted to position the first coupling component at differing heights relative to the hitchhead assembly. The drawbar assembly is selectively inverted, depending upon the height of the tow vehicle, so that the first coupling component is held at a height that conveniently interengages the second coupling component carried by the hitchhead. The spring means preferably include at least one generally helical coil or compression spring and linkage that are interconnected between the horizontal pivot, located at a rearward portion of the drawbar extension, and the trailer. Each spring may be disposed in a housing that is mounted in the trailer frame. A single spring may be utilized for relatively low tongue weights; a pair of springs may be employed for medium tongue weights; and three springs may be used for heavy tongue weights. The spring assemblies may be adjustably preloaded to dampen pivoting of the drawbar extension about the horizontal axis by a selected or predetermined amount. The spring assembly may include a connector link that is slidably mounted within the housing and resiliently engaged with each spring. The depending connector link may be pivotably interconnected to a distal portion of the drawbar extension. The spring means minimize the hinging motion or toggle effect normally exhibited between the trailer and the town vehicle and thereby reduce the need for using heavy tongue weights to counteract this effect.

WO 00/71368 PCT/USOO/14839 10 BRIEF DESCRIPTION OF THE DRAWINGS Other objects, features and advantages will occur from the following description of preferred embodiments and the accompanying drawings, in which: FIG. 1 is an elevational, side view of a preferred trailer hitch according to this invention with the hitchhead assembly suspended from the front end of a trailer and the drawbar assembly extending from a tow vehicle (not shown); the hitchhead assembly and the drawbar assembly are depicted prior to coupling in accordance with this invention; FIG. 2 is a top plan view of the trailer hitch in an assembled condition; FIG. 3 is an elevational, party cross sectional and partly cut away view of the drawbar extension, the yoke, the rearward end of the channel, and the ball component and clevis by which the foregoing components are suspended from the trailer; FIG. 4 is a plan view of the drawbar extension, the yoke and the second coupling component; FIG. 5 is a rear, cross sectional view of the lower portion of a preferred single coil spring assembly used in the hitch of this invention; FIG. 6 is a rear, cross sectional view of the upper portion of the spring assembly; and FIG. 7 is an elevational side view of the hitch in a fully assembled and operating condition. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS There is shown in shown in FIGS. 1 and 2 a preferred double-acting, weight distributing hitch apparatus 10. It should be understood that a number of the WO 00/71368 PCT/USOO/14839 11 components featured in the hitch are analogous and constructed similarly to corresponding features disclosed in pending PCT International Publication No. W000/01546, United States Application Serial No. 09/109,740 filed July 2, 1998 and United States Patent No. 5,951,036, as well as United States Application Serial No. 09/444,483 filed November 19, 1999. The descriptions contained in these specifications are incorporated herein by reference. Components described herein may also be constructed in the manner shown for analogous components and those referenced applications. In particular, hitch 10 is designed for attaching an A-frame trailer 12 to a tow vehicle, not specifically shown. Hitch 10 is suited for use in connection with various types of trailers, as well as all types and sizes of tow vehicles. Neither the type of tow vehicle nor the type of trailer should be construed as a limitation of this invention. It should also be understood that the axles and wheels of both the trailer and the tow vehicle are not depicted. These are standard components that do not comprise a part of the invention. Their relative positioning and operation should be understood to those skilled in the art. Nonetheless, through the use of the invention disclosed herein, the axles of the trailer may be spaced further apart than in conventional trailers. This is possible because of the significantly reduced tongue weight required by this trailer hitch. Repositioning the forward trailer axle closer to the tongue reduces the leverage of the tongue and thereby the tongue weight. This shall become more evident from the following description. Hitch apparatus 10 includes a forward drawbar assembly 14 and a rearward hitchhead assembly 16. The hitchhead assembly is attached to and suspended from trailer 12 in a manner described in the above-referenced applications and further WO 00/71368 PCT/USOO/14839 12 described below. The drawbar assembly is disposed beneath the tow vehicle bumper (not shown) and includes an elongate drawbar, 20 which preferably has a square cross sectional shape. Bar 20 is selectively inserted in a complementary shaped receiver tube 22. The receiver tube is secured to and extends from a transverse mounting bar 24. This bar extends between and is attached to the longitudinal frame components of the tow vehicle. In tow vehicles not employing a frame, the transverse bar can be attached to various other structural components of the tow vehicle. Bar 20 is secured to tube 22 by a transverse pin 26. A first coupling component 30 is permanently and preferably unitarily fixed to drawbar 20. Component 30 comprises a shank that extends angularly from drawbar 20 and has a pair of spaced apart flanges 32 and 34, best shown in FIG. 2. These flanges include a pair of aligned upper holes and a pair of aligned lower holes. Each pair of aligned holes receives a respective hitchpin 40, 41. The lower pin should be removable. The upper pin may be permanently or removably carried by component 30. The operation of the coupling component 30 and the hitchpins is described more fully below. Each pin is secured in its respective hole by a spring clip 44. The axis 50 of drawbar 20 is perpendicular to the line interconnecting the centers of the holes receiving pins 40 and 41. In alternative embodiments a pivotably adjustable first coupling component may be used as shown in United States Patent No. 5,951,036 and PCT International Publication No. W000/01 546. Hitchhead assembly 16, also shown in FIGS. 3 and 4, includes a standard ball element 46 that is threadably attached to a clevis 64. Alternatively, the ball may be welded or otherwise secured to the clevis. The ball element comprises the Y-axis coupling about which the rig rotates when one of the wheels strike a curb, for example. The ball is mounted in and suspended from ball coupler 60 (FIGS. 1 and 2) in a WO 00/71368 PCTUSOO/14839 13 conventional swiveling manner and, more particularly, in the manner shown and described in the above-referenced applications. The Y-axis is in the line of travel. The hitchhead further includes a yoke device 72 that is pivotally connected to the lower end of clevis 64 by a horizontal pivot or bolt 68. Yoke 72 includes a forward bearing 65 and a generally rearwardly extending shank 69. As shown in FIGS. 1, 3 and 4, a drawbar extension 66 is pivotally interconnected to pivot 68 at the lower end of clevis 64. More particularly, drawbar extension 66 includes a pair of elongate spaced apart elements 71 and 73 interconnected by transverse struts 75. A hole is formed proximate the forward end of each elongate element 71, 73. These holes, which are aligned interengage clevis pivot 68 such that drawbar extension 66 is pivotably connected to clevis 64 as shown in FIGS. 3 and 4. As best shown in FIG. 4, elements 71 and 73 are sandwiched about shank 69 of yoke 72. Threaded connector element 79 extends between elements 71 and 73 and through shank 69. By tightening component 79 elements 71 and 73 of drawbar extension 66 are tightened against the shank. Horizontal pivot 68 permits the drawbar extension and the yoke to pivot or rotate about a horizontal axis that is generally transverse to the direction of travel. As a result, the drawbar extension is permitted to pivot relative to the hitch ball in the manner indicated by doubleheaded arrow 70 in FIG. 1. A channel member 80, FIGS. 1 - 7, is pivotally connected to yoke 72 by a generally vertical pin or shaft 82. More particularly, channel 80 is attached integrally to a pair of spaced apart bearings 84, 85 that are sandwiched about the forward bearing 65 of yoke 72. See the analogous construction disclosed in United States Patent Application Serial No. 5,951,036 and PCT International Publication No. W000/01546.

WO 00/71368 PCT/USOO/14839 14 The bearings have aligned holes that receive pin 82. As a result, channel member 80 is pivotal about a Z-axis defined by pin 82 relative to hitchhead 16 and drawbar extension 66, in the manner indicated by doubleheaded arrow 86 in FIG. 2. The pin 82 effectively forms a Z-axis coupling. A horn 88, best shown in FIGS. 1 and 2, is slidably mounted in channel 80 in the manner described in the previously referenced applications. As a result, horn 88 may be adjusted vertically within channel 80 as indicated by doubleheaded arrow 90 in FIG. 1. Horn 80 includes an upper recess or slot 92 and a lower hitchpin hole 94. An incline or ramp 96 extends from the forward end of the horn to a point adjacent recess 92. The channel member and its adjustable attached horn comprise a second coupling component that is interengaged with the first coupling component in a manner more fully described below. Drawbar extension 66 is interconnected to trailer frame 52 proximate the rearward distal end of the drawbar extension. More particularly, drawbar extension 66 is interconnected to the trailer frame by a vertically disposed dampening spring assembly 300, FIGS. 1, 2, and 5 - 7. The distal end of the drawbar extension is pivotably connected to a connecting link 301 of spring assembly 300 at X-axis pivot 302. In the version described herein, the spring assembly employs a single coil spring assembly 300. Alternative embodiments may employ other numbers and types of spring assemblies. Spring assembly 300 is shown in detail in FIGS. 5 and 6. The spring assembly is mounted by plates 297 and 315 to a spring assembly support component 299 of trailer frame 52. See also FIG. 2. A linkage 316 depending from assembly 300 and WO 00/71368 PCT/USOO/14839 15 extending through component 299 interconnects the spring assembly with a pivot 302 formed through drawbar extension 66 (FIGS. 5 and 6). Spring assembly 300 comprises a vertically disposed helical coil spring 304 that is arranged vertically and mounted within a cylindrical spring housing 306. The housing comprises a pair of telescopically interconnected cylindrical components 307 and 309. The spring is wound about a central tube 308 and extends between a lower movable base 310 and an interior surface at the top end of spring housing 306. The lower end of tube 308 is fixed to a drive block 314. Drive block 314 is received slidably through a central opening in a plate 315. The distal end of drawbar extension 66 is pivotably connected by pivot 302 to connecting link 301 of spring assembly linkage 316. Connector link 301 is received in the lower end of a generally cylindrical linking component 320 and is secured therein by appropriate means such as, for example, a threaded sleeve or bushing 322, which is fastened to link connector 301 and threadably engaged with interior threads of link component 320. Component 320 extends upwardly through a bottom bracket 324 and into a vertical opening 326 in spring assembly support 299. The link component carries a projection 330 at its upper end. A pin 332 pivotably interconnects projection 330 to block 314. As shown in FIG. 6, the upper end of tube 308 receives a threaded shaft 334 that carries a nut 338 that is welded to the upper end of tube 308. Shaft 334 extends through a central opening in a movable cap 335 received in an opening at the top of cylindrical component 309. The upper end of shaft 334 carries a fixed head 339 that is received in a clearance 341 of upper plate 340. That plate is supported above housing 306 by vertical posts 342. The normal bias of spring 304 urges cap 335 against the WO 00/71368 PCT/USOO/14839 16 lower surface of plate 340, as shown in FIG. 6. As best shown in FIG. 6, the lower ends of posts 342 are fastened to plate 315. Spring assembly 300 dampens relative movement between the trailer and the rearward end of drawbar extension 66, located at the X-axis couple or pivot 302. When the rig engages a bump in the road, connector link 301 urges link assembly 316 upwardly, as indicated by arrow 370 in FIG. 5. This urges block 314 upwardly. The block pushes movable base 310 upwardly to resiliently compress coil spring 304 within housing 306. At the same time, block 314 drives tube 308 and attached shaft 334 upwardly such that the shaft slides through cap 335 and plate 340. The coil spring thereby dampens the upward hinging movement between the tow vehicle and the trailer. Conversely, when the rig engages a dip in the road, the connector link and attached link assembly are pulled downwardly in the direction of arrow 374. This pulls tube 308 and shaft 334 downwardly. As a result, upper cap 335 pushes cylindrical component 309 resiliently downwardly against coil spring 304. Downward movement of the drawbar extension relative to the trailer and therefore dampened hinging between the tow vehicle and trailer are also dampened. It should be noted that the spring may be selected and preloaded to accomplish desired dampening. The preloaded compression spring largely replaces the pressure required by conventional heavy tongue weights and serves to significantly reduce bounce-related hinging and toggling effects. Various alternative types of dual acting spring constructions may be employed within the scope of this invention. Preloading the coil springs eliminates the tedious and often difficult task of preloading conventional trailer hitch spring bars.

WO 00/71368 PCT/USOO/14839 17 Spring assembly 300 is typically constructed to permit some degree of play or movement in linkage 316 as the trailer is pulled. Lateral play is provided by pivot 332. That pivot may be disposed on a tapered, fulcrum-like surface (not shown) of projection 330 so that play is also provided in forward and rearward directions. In such embodiments, a slight gap should be formed between link component 320 and surrounding brackets or structure carried by the trailer (e.g. lower bracket 324, FIG. 6). Hitch apparatus 10 is installed in the following manner. Initially, drawbar 20 is inserted into receiver tube 22. The trailer is then leveled with respect to the ground using conventional leveling means. Next, the installer selects the orientation of the drawbar. This will depend upon the height of the tow vehicle. Normally, the receiver tube is mounted to the tow vehicle such that its axis is positioned anywhere from 10" to 17" above the ground. For low heights (e.g. 10" to 13.5") the drawbar assembly is orientated in the manner shown in FIG. 1. Coupling component 30 is angled upwardly and positioned proximate hitchhead assembly 16. Alternatively, in cases where a larger tow vehicle and a higher positioned receiver tube are used, the drawbar assembly may be inverted so that the coupling component is angled downwardly to meet the hitchhead assembly 16. It should be noted that in most cases the hitchhead assembly is positioned such that there is a distance of approximately 17" to 19" from the ground to the center of the ball. After the drawbar assembly is oriented properly, the bar 20 is inserted into receiver tube 22 and the pin 26 is connected to secure the drawbar assembly to the tow vehicle. The user then installs an upper hitchpin 40 through the aligned holes in component 30 and secures that hitchpin in place with an appropriate hitchpin clip 44.

WO 00/71368 PCT/USOO/14839 18 Hitchhead assembly 16 is mounted to trailer 12 by suspending the ball element from the ball coupler. The drawbar extension 66 is interconnected to spring assembly 300 by pivot 302. A connecting strap 400 is installed to connect trailer frame 52 and shank 69. Horn 88 is vertically adjusted within channel 80 so that the center of recess 92 is approximately equal to the height of the center of the upper holes (i.e. hitchpin 40) in coupling component 30. The horn is then locked in place in the manner described in the referenced applications. In some cases, the horn may be tack welded so that it is permanently fixed in the channel. At this point, the hitch installer's task is normally completed. In some cases, skilled laymen or homeowner may be able to undertake the above referenced installation procedures. To complete installation and coupling of the tow vehicle and trailer, the user operates jack 56, FIG. 1, so that the center of recess 92 is positioned approximately .75 inches above the center of holes 36. The apparatus is then coupled by simply driving the tow vehicle rearwardly toward the trailer. The upper hitchpin 40 interengages ramp 96 and rides up the ramp until it drops into horn recess 92. At this point, lower holes 38 of component 30 and lower hole 94 of horn 88 are separated by an angle of approximately 1*. This amount is determined because the center if the lower horn hole 94 is disposed approximately 1* rearwardly (i.e. toward the trailer) of the center of recess 92. The user then raises jack 56 until holes 38 and 94 are aligned. A lower hitchpin 41, FIG. 1, is then inserted through the aligned lower holes and coupling is completed. The jack is then used to lower the trailer and removed. At this point, the apparatus is attached to and is fully coupled as illustrated in FIGS. 2 and 7. Due to the offset construction between the upper recess and the lower hole of horn 88, the WO 00/71368 PCT/USOO/14839 19 drawbar of assembly 14 is tilted 1'. This imparts the necessary torsion to the tow bar assembly. It has been determined that 10 provides more than sufficient weight distribution because of the reduced amount of tongue weight needed by this apparatus. In operation as the tow vehicle is driven, drawbar extension 66 pulls trailer at a point located behind and below the trailer ball. The towing force is applied to the trailer at the distal end of the drawbar extension and not at the hitch ball. The trailer and drawbar extension overlap and effectively act as a unified beam. There is significantly less need to use a heavy tongue weight because a toggle or hinge effect is not exhibited at the hitch ball. Instead the toggle is formed at pivot 302, behind and below the ball and is level or directed downwardly. The rear end of the tow vehicle, therefore, resists being lifted upwardly. Moreover, because a double-acting spring is used, a heavy tongue weight is not required to offset trailer bounce. Instead, the unique form of interconnection between the trailer and the hitch, as well as the spring force of assembly 300 accomplishes this. During normal operation on a level surface, virtually no hinging is permitted. If a bump or dip is struck, the spring assembly allows the drawbar extension to pivot (about pivots 68 and 302) and this permits the requisite hinging between the tow vehicle and the trailer. Preloaded spring assembly 300 then quickly returns the drawbar extension to its original position (i.e. the spring assembly restricts pivoting of the drawbar extension about pivots 68 and 302) after the bump or dip is traversed and thereby serves to dampen hinging movement between the tow vehicle and the trailer. An improved, stable ride is achieved. At the same time, the resulting tongue weight normally needed is reduced substantially. The new hitch eliminates the free hinging in every direction and the toggling by extending the drawbar back under the trailer frame and providing the application of the WO 00/71368 PCT/USOO/14839 20 towing force at a coupling joint which is below the line joining the axles of the tow vehicles and the trailer. This means that any toggle force generated by the trailer is downward and increases traction on the tow vehicle. Reducing the tongue weight yields several important advantages. Less stress is exerted on the suspension and springs of the tow vehicle. Additionally, the transverse moment that is otherwise generated when the rig swerves, such as during lane changes or when taking evasive action, is significantly reduced. The risk of jackknifing and flipping is therefore minimized. Moreover, reducing the tongue weight reduces the need for additional items, such as propane tanks and tools, to be stored proximate the tongue. The precise reduction in tongue weight that is possible through the use of the invention may vary. However, the spring assembly is typically preloaded to reduce hinging sufficiently so that the tongue weight may be reduced to a level not exceeding 1.5 times the average weight per foot of the trailer. Ideally, the tongue weight that is required is between /2 and 1 1 % times the average weight per foot. This means that the tongue weight should ideally be approximately 120 to 300 pounds. One half of that weight is transmitted to the tow vehicle. Accordingly, through the use of this hitch, only 60 to 180 pounds of tongue weight acting on the tow vehicle. This is less than the average weight per foot of virtually all trailers. This is a negligible force, which should have virtually no effect on the tow vehicle or its suspension. Such a low force also permits the hitch of this invention to be utilized on vehicles that do not have a frame. The dolly required in the prior art is eliminated. By reducing the tongue weight required, the forward axial of the trailer may be moved forwardly along the trailer, which increases further the stability of the trailer.

WO 00/71368 PCT/USOO/14839 21 It should be noted that in alternative embodiments of this invention, a plurality of coil springs may be utilized to dampen upward and downward movement of trailers having even heavier tongue weights. Alternative spring assemblies and means for mounting those assemblies to the trailer may also be employed. For example, one or more stacks of disc springs may be utilized. See the above referenced United States applications. Such assemblies are particularly effective for heavier tongue weights. In either version, the double-acting spring assembly serves to dampen both upward and downward hinging movement between the tow vehicle and the trailer. The forward end of the trailer overhangs the rearward end of the drawbar extension. As a result, the vehicles act essentially as a unified beam while traveling down the highway. A heavy tongue weight is therefore not needed to offset a hinge or toggle effect. Instead, the unique form of interconnection between the trailer and the hitch, as well as the spring force of assembly 300 accomplishes this. The hitch of this invention provides an improved stable ride. The tongue weight may be reduced to a level between %/ and 1 /2 times the average gross weight per foot of the trailer. This translates to a tongue weight of approximately 300 pounds or less. A force comparable to only 2 of this weight is transmitted to the tow vehicle. A significantly improved, stable ride is achieved. Although specific features of the invention are shown in some of the drawings and not others, this is for convenience only, as each feature may be combined with any and all of the other features in accordance with this invention. Other embodiments will occur to those skilled in the art and are within the following claims:

Claims (11)

1. A double-acting trailer hitch for interconnecting a trailer to a tow vehicle, said hitch comprising: a drawbar assembly including a bar attachable to the tow vehicle and a first coupling component carried proximate a distal end of said bar; a hitchhead assembly that is mountable to the trailer, said hitchhead assembly including a ball component that is swivelably suspendable from the trailer, a drawbar extension connected to said ball component such that such drawbar extension is pivotable along a generally horizontal first axis that is transverse to the direction of travel, and a second coupling component pivotably connected to said drawbar extension along a generally vertical second axis, said first and second coupling components including complementary interengagable means for selectively coupling said first and second coupling components together and holding said drawbar assembly at a pre-determined axial angle relative to the ground; and means for interconnecting a rearward portion of said drawbar extension to the trailer, said means for interconnecting including a pivot that mounted to said drawbar extension and having a substantially horizontal axis of rotation extending transversely to the direction of travel, and a double-acting spring assembly for joining said pivot to the trailer and dampening movement of the trailer upwardly and downwardly relative to the tow vehicle during travel.

2. The hitch of claim 1 wherein said hitchhead assembly further includes a yoke for pivotably interconnecting said drawbar extension and said second coupling component along said second axis, said yoke being pivotably connected to said ball component along said first axis. WO 00/71368 PCTIUSOO/14839 23

3. The hitch of claim 1 in which said first coupling component is fixedly interconnected to said bar.

4. The hitch of claim 1 in which said interengagable means include upper and lower hitchpins carried by said first coupling component, at least said lower hitchpin being removably connected to said first coupling component, and an upper recess and a lower hitchpin hole formed in said second coupling component for respectively receiving said upper and lower hitchpins when said coupling components are interengaged.

5. The hitch of claim 4 in which said second coupling component includes a horn having a ramp that is connected to said recess, said drawbar assembly being directed against said horn such that said upper hitchpin rides up said ramp and enters said recess, the height of the trailer being adjusted to align said lower hitchpin hole in said first coupling component with said lower hitchpin hole in second coupling component such that said lower hitchpin may be inserted through said aligned holes to fixedly interconnected said first and second coupling components.

6. The apparatus of claim 5 in which said second coupling component includes means for adjusting the height of said horn, said means for adjusting including a vertical channel element that is pivotally connected to said drawbar extension and slidably interengagable with said horn and means for interlocking said horn in said channel element at a selected height.

7. The hitch of claim 5 in which said lower hitchpin hole of said horn is disposed at a predetermined vertical angle relative to said slot to impart a desired angle to said drawbar and a corresponding torsion to the frame of the tow vehicle when coupling is completed. WO 00/71368 PCTIUSO0/14839 24

8. The hitch of claim 1 in which said drawbar assembly and said first coupling component are interconnected at an angle such that said drawbar assembly is invertible to position said first coupling component at a different height relative to said second coupling component.

9. The hitch of claim 1 in which said spring assembly includes a coil spring disposed in a collapsible housing that is mounted on said trailer and a linkage that operably interconnects said assembly with said pivot.

10. The hitch of claim 2 in which said yoke and said drawbar extension are fixedly interconnected.

11. A hitch for interconnecting a trailer to a tow vehicle, said hitch comprising: a drawbar assembly including a bar attachable to the tow vehicle and a first coupling component carried proximate a distal end of said bar; and a hitchhead assembly that is mountable to the trailer, said hitchhead assembly including a ball component that is swivelably suspendable from the trailer, a drawbar extension connected to said ball component such that such drawbar extension is pivotable along a generally horizontal first axis that is transverse to the direction of travel, and a second coupling component pivotably connected to said drawbar extension along a generally vertical second axis, said first and second coupling components including complementary interengagable means for selectively coupling said first and second coupling components together and holding said drawbar assembly at a pre-determined axial angle relative to the ground; said drawbar extension being connected to said trailer rearwardly of said ball component for pivoting about a pivot having a substantially horizontal axis of rotation extending transversely to the direction of travel.