CA2104343C - Fifth wheel slip plate - Google Patents

Abstract

A novel improved fifth wheel structure is provided of the type including a fifth wheel plate having an upper bearing face and a rearwardly opening slot having a closed forward end for use in conjunction with a kingpin plate of the type including a lower bearing face from which a kingpin projects downwardly, the fifth wheel plate being adapted to have the kingpin plate disposed thereover with the respective bearing faces in contact with each other and with the kingpin rotatingly and captively disposed in the forward end of the slot. The improvement comprises a plurality, e.g., preferably three, four or five, self-lubricating slip pads, each such slip pad being formed of self-lubricating plastic polytetrafluoroethylene or ultra-high molecular weight polyethylene. Each slip pad is substantially rectangular in shape with four rounded corners and has only its peripheral edges tapered or rounded to be lower than its central region. Each slip pad has a plurality of circular counterbored holes therein, each circular counterbored holes terminating in a circular hole. Each slip pad is secured into its respective rectangular recess within the upper bearing face of the fifth wheel plate, by means of an associated one of a plurality of weld washers, each of which has been placed in its respective circular counterbored hole in its associated slip plate and then welded to the fifth wheel plate.

Description

t 210q~3 This invention relates to an improved fifth wheel structure. In particular it relates to fifth wheel pads in the form of at least one self-lubricating slip pad and preferably three, four or five such pads, secured to a fifth wheel.
The trucking industry utilizes automotive vehicles, commonly referred to as truck rigs consisting of a motorized tractor and one or more trailers connected in tracking relation thereto for the transportation of heavy loads over great distances. It is well known that in order to achieve the maximum economic benefit from the use of such equipment it is desirable to maintain it in as nearly continuous use as possible. Unfortunately such equipment requires a substantial amount of maintenance to keep it in operating condition and to avoid breakdowns enroute.
Such vehicles commonly employ a coupling device known as a fifth wheel in order releasably to couple the trailer to the tractor. A fifth wheel is used pivotally to couple a semi-trailer to a tractor. It generally includes an upper bearing face, front and opposite side marginal edge portions and a rearwardly opening slot. Such fifth wheel is adapted to be used in conjunction with a kingpin plate of the type which includes a lower bearing face downwardly from which a kingpin projects. The fifth wheel plate is adapted to have the kingpin plate disposed thereover with the faces in contact with each other and with the kingpin rotatably and captively disposed in the inner forward end of the slot.

21043~
_ 2 Such fifth wheels provide releasably engaged bearing surfaces, one being mounted on the underside of the forward portion of the trailer. The bearing surface of the tractor supports the weight of the trailer resting against it and acts as a surface against which the bearing surface of the trailer rotates as necessary during towing operations.
Lubrication of the engaged bearing surfaces has normally been provided by the application of a lubricant, usually grease, to the bearing surface of the tractor. Because of long hours of use and the rather rapid dissipation of the lubricant, frequent disconnection of the trailer from the tractor for reapplication of the lubricant was required in order to maintain the equipment in optimum working condition. This reapplication process, when done correctly, requires recleaning of the bearing surfaces to remove residue and accumulated dirt prior to the reapplication of the lubricant. Since nearly continuous operation is economically desirable and since the task is onerous and time consuming, such maintenance is often not performed as frequently as would be desirable. This results in aggravated wearing of the bearing surfaces and progressively worse handling characteristics for the truck rig. This is costly to the trucking business, and annoying to the operator of the vehicle. Further, when the bearing surfaces become worn, they must be replaced. This necessitates removal and replacement of the fifth wheels, a time consuming and expensive undertaking.

_ 3210~3~3 It has also been found that the presence of dirt and moisture between the upper surface of a fifth wheel plate and the opposing undersurface of a kingpin plate of an associated trailer results in excessive wear of the opposing bearing surfaces defined by the fifth wheel plate and the kingpin plate with the result that the pivot connection established between the fifth wheel and the fifth wheel pin or kingpin becomes sloppy and thus enables greater shock loads to be transmitted from the associated tractor to-the semi-trailer.
Fifth wheel lubrication heretofore has been difficult to maintain. Rocking and turning action between a trailer and fifth wheel squeezes the grease off the fifth wheel surface and renders the steering progressively more difficult as the break away friction between the fifth wheel and the trailer bed plate increases. Steering tires deflect laterally during steering maneuvers and this deflection and relative force increase in proportion to the fifth wheel friction. As the static friction breaks loose, the laterally deflected tires rebound re~uiring an immediate steering correction. The result is trailer swing and vehicle yawing.
one attempt to improve the lubrication on the bearing surface has been the use of a TEFLONTM plate attached to the bearing surface on the underside of the trailer so that the TEFLONTM provides lubrication for the fifth wheel unit.
Such a plate avoids the necessity of grease or other types of lubricant as the TEFLONTM itself has lubrication 21~4~3 properties. It has been found, however, that~if a TEFLONTM
disc is placed on the trailer, then one requires far more discs because there are more trailers than there are tractors. TEF10NTM is an expensive material and as the trailer can sit for days without moving, the use of this TEFLONTM disc on the traller is an expensive item.
Another approach to improve the lubrication on the bearing surface was by the ~d'dition of a sheet of a low friction plastic covering, e.g., coverings of certain ultra high molecular weight polyethylenes and polypropylenes.
Such coverings were particularly preferred due to their exceptionally low coefficient of friction and durability.
These plastic coverings were commonly held in place on the fifth wheel bearing surface by screws,- rivets and/or adhesives. Such a sheet improved the lubrication between the two bearing surfaces of the fifth wheel attachment.
Unfortunately, the sheet was often damaged when the tractor was coupled to the trailer because of the impact occurring when the tractor is backed up to the trailer. This impact can often rip off a portion of the sheet, and, in some instances, can rip off the entire sheet.
To protect these plastic coverings, it was proposed to provide two protective "riser bars" on the outsidé
peripheral edges of the fifth wheel bearing plate of the tractor and its associated sloped flanges. Such riser bars were substantially flush with the surface of the plastic covering and extended from the forward edge of the sloped flanges backwards along the circular portion of the bearing 21Q~3~3 _ 5 plate to a point at which the bearing plate was pivotally mounted to the tractor body. The riser bars were positioned in cutout portions of the plastic covering to allow replacement of the covering without disturbing the riser bars. Such peripherally located riser bars were intended both to guide and to pivot the fifth wheel attachment of the tractor so that it was at the correct alignment and location with respect to the trailer during coupling.
In utilizing fifth wheel assemblies having protective riser bars of the type described above, it had been observed that the riser bars, owing to their location, thickness and shape, eventually wore arcuate grooves in the mating bearing surface (commonly known as the "bolster"
plate) of the trailer. Moreover, it had been observed perhaps as a result of the bolster plate wearing unevenly and the fact that the riser bars did not extend rearwards beyond the bearing plate pivot axis, that there was a tendency for the bolster plate to gouge and tear the protective plastic covering on the fifth wheel bearing plate of the tractor. Being located along the outer edge of the substantially circular portion of the bearing plate of the tractor, and being flush with the upper surface of the plastic covering of the bearing plate, the riser bars frequently contacted the bolster plate of the trailer at times other than tractor/trailer coupling. For example, normal rocking of the trailer about a hori~ontal axis extending parallel to the trailer length caused the riser 2~ a~3~3 bars repeatedly to impact against the bolster plate. Also, as the tractor turned relative to the trailer to follow curves in the road, the risers bars rubbed against, and thereby scraped, the bolster plate of the trailer. This action was believed to give rise to the observed arcuate grooves in the bolster plate. Further, since the riser bars did not extend beyond the pivot axis, they afforded no protection from the bolster plate of the trailer after the bearing plate of the trailer tipped (pivotal) to a horizontal seating position during tractor/trailer coupling.
To overcome the above-described difficulties, many proposals have been made in the patent literature.
U.S. Patent No. 3,511,523 patented May 12, 1970 by L.
T. Fuller purported to provide one solution to this problem by means of a seal-forming attachment for the fifth wheel.
The attachment included an elongated resilient seal structure adapted to be secured about, and to extend slightly above, the forward and opposite side marginal edge portions of a fifth wheel. This was alleged to provide fluid-tight sealed engagement with the under-surface of the king pin plate on the associated semi-trailer as the tractor was advanced rearwardly beneath the forward end of the semi-trailer.
U.S. Patent No. 3,704,924 patented December 5, 1972 by R. W. Lowry purported to provide another solution to this problem by means of a replaceable wear plate for the fifth wheels. The wear plate was a substantially flat sheet of 3 '1 3 disposable material having a low coefficient of friction which was releasably secured in fixed position on one of the bearing surfaces for engagement with the other bearing surface and was removable from its respective surface for replacement.
U.S. Patent No. 3,801,136 patented April 2, 1974 by J.
J. Cunha purported to provide another solution to this problem by means of an impervious trough surrounding a portion of the periphery of a fifth wheel. The trough was V-shaped, one side being formed by the edge surface of the fifth wheel, the other side being formed by a band fastened to the edge surface. The band resided at an angle to the edge surface of about 45~ to facilitate cleaning the trough. The upper edge of the band resided below the bearing surface of the fifth wheel to avoid interference therewith.
U.S. Patent No. 3,924,909 patented December 9, 1975 by J. A. Kent et al purported to provide yet another solution to this problem by means of a cover plate which was adapted to fit over the upper surface of a fifth wheel and substantially to conform to the shape of the fifth wheel.
Interposed between the upper surface of the fifth wheel and the lower surface of the cover plate was a low friction material. The cover plate and low friction material were allowed to rotate about the kingpin centre through an angle of approximately 5~ each side of centre. When turns were negotiated which required greater than 5~ of rotation, the trailer pivoting continued between the upper surface of the 210~ 3 cover plate and the trailer bed plate. A pivot centre was provided to attach the cover plate to the fifth wheel and to hold it secure when a trailer was not attached.
U.S. Patent No. 4,169,635 patented October 2, 1979 by F. Szalay et al purported to provide still another solution to this problem by means of a bearing plate cover for the fifth wheel of a vehicle engaging the entire bearing and non-bearing surfaces thereof. The bearing plate cover was composed of a flat sheet plastic material having a low friction coefficient and high deflection characteristics so as to provide a wear-resistant slippery surface for contact with another bearing surface.
U.S. Patent No. 4,542,912 patented September 24, 1985 by A. St.-Louis purported to provide a further solution to this problem by means of a fifth wheel bearing attachment for mounting on a tractor to avoid the necessity of providing oil or grease to lubricate the attachment. The improvement to the attachment included an antifriction polyolefin plastic sheet covering to fit over a circular fifth wheel metal bearing plate and over two-sloped flanges of the fifth wheel attachment. The plastic sheet was attached to the bearing plate and the flanges. Two protective riser bars located on the outside of the two-sloped flanges acted as protection for the sheet when the tractor was coupled to the trailer.
U.S. Patent No. 4,752,081 patented June 21, 1988 by D.C. Reeners et al purported to provide another solution to this problem by means of protection from damage of a low-2 ' ~ ~3~3 .~ g friction plastic covering on the fifth wheel bearing plate of a tractor by a pair of elongated metal "skip" plates.
Such plates were preferably rectangular in shape and were positioned in the interior region of the plastic covering, one on each side of a tapered slot adapted to receive the kingpin of a fifth wheel tongue attachment of the trailer.
The size, shape and position of such skip plates were said to minimize wear on the bolster plate of the trailer, and to minimize any tendency for tearing of the plastic covering during tractor/trailer coupling and normal use of the tractor-trailer.
U.S. Patent No. 5,165,713 patented November 24, 1992 by G. N. Picard purported to provide still another solution to this problem by means of a fifth wheel cover comprising a substantially sheet-like member having a circular portion and a pair of tail portions extending from one side'of the circular portion for covering the bearing plate and sloped flanges of a fifth wheel of a tractor. It also had a central kingpin opening between the tail portions. A cup portion was provided at the end of each tail portion for receiving the rear ends of the sloped flanges therein. At least one hook formation on the side of the circular portion opposite the tail portions was provided for engaging with the rim of the fifth wheel, in order to secure the cover on the fifth wheel. The circular and tail portions and the cup and hook formations were integrally moulded from an anti-friction synthetic plastic material.

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U.S. Patent No. 5,165,714 patented November 24, 1992 by J. W. Kaim ~u~ul~ed to provide yet another solution to this problem by means of a fifth wheel assembly which had a bearing plate with a lubricating plate. A peripheral wall was provided with ~i~metrically-opposed notches extending above the bearing plate Ss~ ce. A non-met~llic lubri~ting wear liner was provided with diametrically-opposed ears notchable with the notches to resist rotational motion by the liner. The liner extended above the peripheral wall and was secured against the bearing plate as a lubrir~ting liner but was retained within the bearing plate cavity against radially outward displacement by the peripheral wall.
10It has been found that these purported solutions were not entirely successful.In view of the foregoing, it is an object of one aspect of this invention to minimi7e the above-noted wear on a fifth wheel bearing surface of the trailer and the ~tten~l~nt deterioration of the fifth wheel bearing surface of the tractor.
An object of another aspect of the present invention is to provide a fifth wheel15attachment assembly having sufficient lubrication properties to avoid the necessity of providing grease or other lubrication to the fifth wheel attachment.
An object of yet another aspect of the present invention is to provide an improved fifth wheel construction whicfi mitig~tes the above-mentioned difficulties.
The present invention provides an improved fifth wheel structure fûr a fifth 20wheel of the type including a fifth wheel plate having an upper bearing face and a rearwardly opening slot having a closed fo~ rd end for use in conjunction with akingpin plate of the type including a lower bearing face from which a kingpin projects downwardly, the fifth wheel plate being adapted to have the kingpin plate disposed thereover with the respective bearing faces in contact with each other and with the ~ ' f ~ "' ~ ,-,, c ~
.........

kingpin rotatingly and captively disposed in the forward end of the slot, the improvement, in combination with the fifth wheel plate, comprising: a plurality of self-lubri~ting slip pads, each slip pad being formed of a self-lubricating plastic selected from the group con~isting of polytetrafluoroethylene and ultra-high molecular 5 weight polyethylene, each slip pad being substantially rectangular in shape with four rounded corners and having only its peripheral edges tapered or rounded to be lower than its central region j each slip pad having a plurality of circular counterbored holes therein each circular counterbored hole termin~ting in a circular hole; and each slip pad being secured into its respective rectangular counterbored hole within the upper bearing face of the fifth wheel plate, by means of an associated one of a plurality of weld washers, each of which has been placed in its respective circular counterbored hole in its associated slip plate and then welded to the fifth wheel plate.
Optimally, by a pl~fell~d variant thereof, three such pads are provided which are secured within associated recesses in the fifth wheel by means of three weld washers. Four or five slip pads can also be provided. By a variant thereof, each slip pad is 0.280" thick and wherein each the recess is 0.125" thick.
In the acco~l~panying drawings, Fig. 1 is a perspective view of the fifth wheel modified according to one embodiment of the present invention;
Fig. 2 is a perspective view of one embodiment of a slip pad; and Fig. 3 is a perspective view of the assembled improved fifth wheel structure of one embodiment of this invention; and Fig. 4 is an enlarged section along the line IV-IV of Fig. 3.

,,y~' As seen in Fig. 1, the fifth wheel plate 10 is of the usual shape, having a curved rear portion 11, and a pair of arms 12 defining a slot 13 therebetween.
A plurality, in this case three, recesses 14, 15, and 16 are provided on the upper face 17 of the fifth wheel plate 10. Each of the recesses 14, 15, 16 in this 5embodiment is provided with locating apertures 18, 19, 20 for the weld washers (not shown) used to secure the slip pad 30 the fifth wheel plate 10.
As seen in Fig. 2, the slip pad 30 is rectangular, but is provided with rounded corners 31 to facilitate the engagement of the tractor into the fifth wheel 10. The upper surface 32 of each slip pad 30 is provided with three countersunk bores, 33, 1034, 35, terrnin~ting in bores 36, 37, 38 to enable securement by the weld washers, (see Fig. 3 and Fig. 4).
Fig. 3 and Fig. 4 show the assembled fifth wheel structure. Each slip pad 30 is secured into its respective recess 14, 15, 16 by means of weld washers 40, which are placed in the countersunk bores 33, 34, 35 and then welded to the fifth wheel 15plate 10 by conventional welding means, e.g., welds 43, 44, 45 in bores 36, 37, 38.
This embodiment of the invention shows the attachment of the slip pads by weld washers.
As described for this embodiment, the weld washer securement technique involves a drilling a counterbored hole in the slip pad, placing a washer on top in the 20counterbored hole and welding the washer to the fifth wheel plate by welding means.
Thus, the present invention provides an improved fifth wheel structure by including three or more self-lubricating slip pads which are firmly secured within sized recesses on the fifth wheel. Such slip pads are substantially-grease-free sliding plates forrned of a self-lubricating plastic, e.g., ultra-high molecular weight .

13 ~ 3 4 ~ ~

polyethylene or polytetrafluoroethylene (TEFLONTM). Such m~teri~l wears longer than steel and requires no grease or other lubrication and remains slippery even in extremely cold weather.
Present coverings for fifth wheels are of approximately 0.280" thick which is appa,ently an absolute maximum having regard to the manufacturers concerns giventhe standardized dimensions prevalent in conventional/pin fifth wheel arrangements.
It is, of course, not desired to be restricted to any particular dimension. However, to provide one useful example, in one specific embodiment, the recesses provided in the fifth wheel each are 0.125" thick. The slip plate itself is 0.280" thick, giving 0.155" of clearance. The slip pad is preferably tapered or rounded at its extremities to f~cilit~te the engagement of a tractor onto the wheel (i.e. to prevent damage).
A further feature of the present invention is that the slip pad is of a single "size" so that it becomes universal. Its particular shape may vary to being square, round, rectangular or curved on one side. The recess may be configured such thatthe configuration in combination with the slip pad could present a mechanical gripping locking mech~nicm.
Three or more slip pads are believed to be required to cover the respective main areas of the fifth wheel.
Among the many advantages to this invention are the ability to do a "quick fix" on the highway involving the unhooking of the trailer, using a chisel to remove a worn slip pad to be replaced by a new slip pad. Additionally, this particular system for a slip pad would elimin~te any damage caused by impact damage during coupling and uncoupling of trailers by tractor drivers. Another feature in the invention . f ~, 14 2~ 4 3 ~ 3 includes a method of adapting existing fifth wheel plates by providing recesses therein to accommodate the slip pads disclosed herein.

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Claims (3)

1. An improved fifth wheel structure of the type including a fifth wheel plate having an upper bearing face and a rearwardly opening slot having a closed forward end for use in conjunction with a kingpin plate of the type including a lower bearing face from which a kingpin projects downwardly, said fifth wheel plate being adapted to have said kingpin plate disposed thereover with said respective bearing faces in contact with each other and with said kingpin rotatingly and captively disposed in said forward end of said slot, the improvement, in combination with said fifth wheel plate, comprising: a plurality of self-lubricating slip pads, each said slip pad being formed of a self-lubricating plastic selected from the group consisting of polytetrafluoroethylene and ultra-high molecular weight polyethylene, each said slip pad being substantially rectangular in shape with four rounded corners and having only its peripheral edges tapered or rounded to be lower than its central region, each said slip pad having a plurality of circular counterbored holes therein, each said circular counterbored holes terminating in a circular hole; and each said slip pad being secured into its respective rectangular recess within said upper bearing face of said fifth wheel plate, by means of an associated one of a plurality of weld washers, each of which has been placed in its respective circular counterbored hole in its associated slip plate and then welded to said fifth wheel plate.

2. The improved fifth wheel structure of claim 1 wherein three slip pads are secured within associated recesses in said fifth wheel by means of three weld washers.

3. The improved fifth wheel structure of claim 1 or claim 2 wherein each said slip pad is 0.280" thick and wherein each said recess is 0.125" thick.