Note: Descriptions are shown in the official language in which they were submitted.
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T~ O WAY CUSHIONING TRAILER HITCH
2 The preserlt invention relates to improvements in trailer hitches. Specifically,
3 the present invention is directed to an improved trailer hitch which provides for the
4 dampening of shock and vibration normally associated with towing a trailer. The hitch has
the ability to dampen shock and vibration in a longitudinal d*ection while simultaneously
6 providing for dampening in the vertical direction.
7 Conventional trailer hitches generally include a rigid support structure attached
8 to a towing vehicle. .~ ball hitch connector mounted to the rigid structure engages a
g correspondingly shaped coupling, generally referred to as a tongue, on the towed vehicle or
trailer. This creates a pivotal but rigid towing system. This rigid system transmits shock and
11 vibration between the trailer and the towing vehicle.
12 The shock and vibration have numerous sources. Upon acceleration or
13 deceleration of the towi~g vehicle, fore-and-aft loads are longitll-lin~lly transmitted from the
14 trailer to the towing ve~icle. A driver commonly experiences theses forces as jerking starts
1~ and stops. Further, bumps and ruts in a towing surface subject a towing vehicle and trailer
16 to vertical shock and vibration. These vertical forces are transferred between the vehicle and
17 trailer through the trailer hitch. It is well known that undue wear and damage to the towing
18 vehicle, the hitch and the trailer result from the continuous shock and vibration commonly
19 associated with towing a trailer.
To overcome the problems associated with shock and vibration, trailer hitches
21 with various dampening mechanisms have been proposed in the prior art. Previously
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proposed hitches with dampening mechanisms have addressed vibration and shock
2 absorption in either the vertical or longitudinal direction. One such system has been
3 disclosed in U.S. Patent No. 4,817,978 by James. The system disclosed therein includes a
4 series of resilient blocks within the towing bar to dampen fore-and-aft vibration. Another
system as disclosed in U.S. Patent No. 4,773,668 by Muonro provides for dampening on a
6 vertical axis by means for a resilient bushing inserted into the draw bar of a trailer hitch.
7 It is a primary object of the present invention to provide an improved trailer
8 hitch whereby vertical and fore-and-aft vibration and shock are absorbed or reduced
9 simultaneously.
Another object is to provide for an improved trailer hitch capable of
1 1 simultaneously absorbing vertical and fore-and-aft vibration and shock which is of simplistic
12 design with a minimum number of components allowing for a low manufacturing cost.
13 Yet another object of the invention is to provide an improved trailer hitch
14 which is easily attached to and removed from a receiver tube of a towing vehicle.
Still another object of the invention is to provide an improved trailer hitch with
16 a load gauge capable to displaying the vertical load on the hitch.
17 It is still another object of the invention to provide an improved trailer hitch
18 which is adapted to receive a conventional ball hitch connector.
19 These and other objects will become apparent upon reading the following
detailed description of the present invention, while referring to the attached drawings, in
2 1 which:
22 FIGURE 1 is a three dimensional view of the trailer hitch apparatus and
23 receiving tube.
24 FIG. 2 is a cross sectional side view of the apparatus taken generally along line
2-2 of FIG. 1.
26 FIG. 3 is an exploded view of the apparatus.
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2 DETAILED DESCRIPTION OF THE INVENTION
3 The present invention relates to an improvement in the design of a trailer hitch
4 whereby shock and vibration between a towed vehicle and trailer are dampened in both the
longitudinal and vertical direction. This invention has the advantage of offering maximum
6 reduction in vibration and shock because of its two way cushioning effect. Further, the
7 simplicity of the invention's design allows for cost effective manufacture.
8 Broadly stated, the present invention provides for an apparatus to be removably
9 coupled to a vehicle mounted receiver tube with at least one aperture. The a~palal~ls consists
of an elongated hollow draw bar tube with at least one aperture. A slide block with a bore
11 inside the draw bar tube is adapted to move longit~1-1in~lly relative to the draw bar tube. A
12 retaining means through the apertures and bore holds the slide block stationary relative to the
13 receiving tube. This allows the draw bar to move longit~l~lin~lly relative to the receiving
14 tube. A biasing means within the draw bar tube provides a resistance against longitudinal
movement. This provides for dampening of fore-and-aft vibration and shock. The apparatus
16 further has a ball hitch assembly carried by a traverse support bar attached to an outer end
17 portion of the draw bar tube. The ball hitch assembly is biased against vertical movement
18 thereby dampening shock or vibration in the vertical direction. The combination of the
19 longitudinal and vertical biasing mechanisms provides for superior shock and vibration
absorption. The hitch also includes a load gauge for estim~ting the vertical load on the trailer
2 1 hitch.
22 Turning now to the drawings, FIG. 1 generally shows the apparatus 10 and a
23 receiving tube 12. A pair of transverse apertures 14 and 16 (shown hidden) are present in the
24 walls of the receiving tube 12. The receiving tube 12 may be mounted on a towing vehicle
in any number of ways depending upon the configuration of the towing vehicle. Most
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commonly, it is bolted to the frame of the towing vehicle and it is contemplated that it any
2 means which provides a safe and secure connection is approl)liate.
3 FIGS. 1, 2 and 3 show a hollow draw bar tube 18 with a pair of transverse
4 apertures 20 and 22 present in a first side wall 24 and a second side wall 26 (not shown) of
the draw bar tube 18. A first side wall extension 28 and a second side wall extension 30
6 extend from one end of the draw bar tube 18. The draw bar tube 18 is configured to be
7 closely and slidably received by the receiving tube 12 as depicted in FIG. 1. The draw bar
8 tube 18 is contemplated to be made of heavy gauge metal tubing which provides an
9 al~pl o~l iate strength for the application. It should be understood that while the receiving tube
12 and the draw bar tube 18 are shown to be generally square, they can have many cross
11 sectional profiles including round, triangular, hexagonal and the like. Further, the two
12 apertures 14 and 16 defining circles and the two apertures 20 and 22 defining elongated slots
13 constitute the preferred embodiment of the invention. However, certain applications may
14 require only one aperture 14 or 16 and one aperture 20 or 22 as well as various other aperture
shapes.
16 Within the draw bar tube 18 is a slide block 32. A bore 34 in the slide block
17 32 is axially aligned ~ith the slots 20 and 22. A front dampening member 36 is retained
18 within the draw bar tube 18 by a front wall 38 and the slide block 32. Likewise, a rear
1~ dampening member 40 is retained in draw bar tube 18 by slide block 32 and a transverse
support bar 42 which defines a rear wall of draw bar tube 18.
21 Once draw bar tube 18 is inserted into the receiving tube 12, the draw bar tube
22 18 is retained within the receiving tube 12 with a conventional hitch pin 44. The hitch pin
23 44 extends through the apertures 14, 16, 20, and 22 and the bore 34. Accordingly, the slide
24 block 32 is held stationary relative to the receiving tube 12 while moving longitudinally
relative to the draw bar tube 18. This allows for the draw bar tube 18 to be longitudinally
26 movable within the receiving tube 12. The dampening cushions 36 and 40 bias the
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movement of the draw bar tube 18. Additionally, the size of the apertures 20 and 22
2 determine the limits of the longitudinal movement of the draw bar tube 18 relative to the
3 receiving tube 12 assuring that the receiving tube 12 does not contact the transverse support
4 bar 42. The hitch pin 44 is secured with a hair pin 46.
The transverse support bar 42 has an upper end 48 and a lower end 50. The
6 support bar 42 is secured to the outer end of the draw bar tube 18 between the first side wall
7 extension 28 and the second side wall extension 30. It is preferred that transverse support
8 bar is solid steel stock and attached to the draw bar tube 18 by conventional weldment.
9 A ball hitch assembly indicated generally at 52 includes an upper housing 54,
a lower housing 56 and a mounting element 58. The upper and lower housings 54 and 56 are
11 suitable heavy gauge steel stock tubing similar to the draw bar tube 18. Each housing 52 and
12 54 are open at one end and closed at the other by plates 60 and 62 with conventional
13 weldment. The upper housing 54 closely and slidably receives the upper end 48. The lower
14 housing 56 closely and slidably receives the lower end 50. An upper dampening cushion 72
is confined within the upper housing 54 and a lower dampening cushion 74 is confined
16 within the lower housing 56.
17 The mounting element 58 is attached to the upper housing 54 and the lower
18 housing 56 by conventional weldment. Accordingly, the ball hitch assembly 52 is biased
19 against vertical movement by the upper cushion 72 and the lower cushion 74. A horizontal
ball plate 76 extends from the mounting element 58. A bore 78 in ball plate 76 allows for
21 a ball hitch connector (shown in dotted lines) to be attached to the ball plate 76 for
22 connection to a conventional trailer tongue (not shown).
23 The dampening members 36, 40, 54 and 56 are bullet-shaped polyurethane
24 cushions. The bullet shape allows for the cushions to be resiliently deformed providing a
partial resistance to the movement of the draw bar tube 18 or the ball hitch assembly 52. The
26 durometer of the polyurethane cushions is preferably between 68 and 100. Clearly, it should
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be appreciated that, in place of the cushions, any number of resilient materials or structures
2 could be used including springs. Further, although support bar 42 and housings 54 and 56
3 are preferably rectangular in nature, any a~prol~liately dimensioned material can be used as
4 described for draw bar tube 18.
In the preferred embodiment of the invention, the ball hitch assembly 52 is
6 assembled in a manner which places a preload on the cushions 72 and 74. The preload limits
7 the movement of the ball hitch assembly and prevents the ball hitch assembly from moving
8 to far in one direction which would cause either the upper or lower housing to disengage
9 from the transverse support bar.
A load gauge comprises an indicator 80 and a scale 82. The scale 82 is marked
11 on the first or second side wall extensions 28 or 30. The indicator 80 is attached to the
12 transverse support bar 42 as the same side as the scale 82. Ideally, a load on a trailer is
13 balanced over the wheels of the trailer and no vertical load is placed on the trailer hitch.
14 Therefore, the load gauge will maintain a position in the middle of the scale. A load that is
too far forward on a trailer will cause the indicator 80 to move downwardly along the scale
16 82. In the event a trailer load is too far rearward, the indicator will have move upwardly.
17 Increments on the scale show the estimated the load in pounds.
18 While various embodiments of the present invention have been shown and
19 described, it should be understood that other modifications, substitutions and alternatives are
apparent to one of ordinary skill in the art. Such modifications, substitutions and alternatives
21 can be made without departing from the spirit and scope of the invention, which should be
22 determined from the appended claims.
23 Various features of the invention are set forth in the appended claims.
