Trailer landing gear cushion foot

Abstract: A cushioned landing gear foot (40) is attached to the landing gear leg (12) by a tubular suspension axle (32) within a housing abutment member (26) on the lower end of the leg, and which abutment engages a resilient pad (50) in a pocket on the foot when under compression load. The abutment member (26) has a rectangular cross section including a flat bottom surface for abutting the pad. The clearance between this flat surface (in elevated condition) and the resilient pad is less than the potential vertical movement of the hollow suspension axle in a pair of slots (48) into which it extends. The pad retaining pocket includes a pair of fore-and-aft inverted L-shaped retaining walls (52) allowing approximately 20 degree fore-and-aft articulation of the foot on the leg, and approximately five degree side-to-side articulation. When the leg and foot are put under load, the pad will be deformed until a predetermined maximum force is applied to it, and then the axle will bear all load exceeding this predetermined amount.

Description: This invention relates to a cushion foot assembly for a trailer landing gear support. Cushioned feet for landing gears have been generally known for some years. It was proposed in US-A-3219362 to use resilient blocks between upper and lower plates that were bolted together. The upper plate was bolted to a frustum welded on the lower end of the landing gear leg. US-A-3666190 shows the insertion of a resilient toroid between the leg and the foot, the latter being crimped onto or bolted onto the leg. In US-A-4462612 the foot is retained with crimping onto the leg portion, holding an elastic pressure body in place. In US-A-4634144 the foot is crimped over the leg to retain a wedge-shaped resilient member. In US-A-4824136 the foot is bolted to the leg, with a resilient pad enclosed therebetween. It will be noted that in all of these except US-A-3219362 the pad is enclosed so that it is not visible to evaluate its condition or potential replacement. Most of them, moreover, do not have the foot readily removable from the leg for replacement in case of damage to the foot. Such damage can readily occur, for example, if the trailer supported on a landing gear shifts, or the landing gear foot is lowered onto an uneven surface as on a rock, or a partially elevated foot strikes something during movement of the trailer. The typical marketed landing gear foot of the padded type has afore-to-aft articulation of about five degrees, and a side-to-side articulation of about five degrees, such that placement on an uneven surface more than this angle can readily damage the foot and/or leg structure under the heavy load of the trailer. Replacement of deteriorated rubber pads is a problem with these prior units as can be readily envisioned. Rubber pads do deteriorate as by entry of mud, dirt, etc. into the housing, and by ageing of the rubber, so that they should be periodically replaced. Damage to the foot also calls for replacement. Removal of the foot too often requires use of a cutting torch, followed by the problem of mounting another foot on the leg or alternatively replacement of the entire leg. These actions require specially trained repairmen. While the foot of the support of US-A-4634144 can be removed for replacement, it only fits on the special leg as there shown. US-A-3666290 discloses the features of the pre-charactersing portion of claim 1. According to the present invention, there is provided a landing gear assembly with the features of claim 1. The invention provides a number of advantages and make it possible, where required, to design a landing gear assembly which overcomes one or more of the disadvantages of previous constructions as mentioned above. Thus, it is possible to produce an effective cushioned landing gear foot which allows ready visibility of the resilient cushion to enable evaluation of the condition thereof, and which enables the foot to be readily removed for replacement of the rubber cushion or to substitute another foot in the event of damage to the existing one, without having to use a cutting torch. The foot is attached to the leg by a suspension axle which may be arranged such that it does not have any initial compression load applied to it when the landing gear is lowered to support a trailer. The lower end of the leg has an abutment member which engages the resilient pad under compression load. Preferably, the abutment member has a rectangular cross section including a flat bottom surface for abutting the pad. In a preferred construction, the pad has sufficient clearance with respect to a pair of front and rear inverted L-shaped retaining walls to allow an approximately 20 degree fore-and-aft articulation of the foot on the leg, and an approximately five degree side-to-side articulation. In the preferred construction the clearance between this flat surface (in elevated condition) and the resilient pad is less than the potential vertical movement of the hollow suspension axle in a pair of slots into which it extends, so that when the landing gear is lowered, the abutment member first engages the pad and compresses it without the suspension axle being put into compressive load. When the resilient pad is resiliently distorted under a load on the assembly approaching a predetermined partial load, preferably about 6,800 to 9,100 kg, the axle begins to bear some load. When the load on the pad exceeds a predetermined maximum, preferably no more than about 11,300 kg, the axle bears all of the excess load. The invention may be carried into practice in various ways but one landing gear assembly embodying the invention will now be described by way of example with reference to the accompanying drawings, in which: Fig. 1 is a side view of the landing gear assembly; Fig. 2 is a rear view of one of the landing gear leg and foot assemblies of the landing gear assembly; Fig. 3 is an enlarged side view of the lower end of the landing gear leg and cooperative foot of the landing gear leg; Fig. 4 is a side view of the components in Fig. 3 showing the fore-to-aft articulation range; Fig. 5 is a rear view of the components shown in Figs. 3 and 4, showing side-to-side articulation; Fig. 6 is a plan view of the resilient compressible cushion or pad in the foot; and Fig. 7 is an end view of the cushion or pad shown in Fig. 6. Referring now specifically to the drawings, the landing gear assembly 10 typically comprises a pair of like landing gear legs, a gear box adjacent one of these legs, an input drive shaft to the gear box for engagement with a hand crank, and a cross shaft to the second leg. The combination will be described herein relative to one leg assembly, it being understood that the novel features on the second leg assembly are identical. More specifically, referring to the drawings, the single leg assembly 12 of the landing gear assembly 10 is shown to include a telescopic leg employing an upper outer tubular leg member 14 and a lower inner tubular leg member 16. Each leg assembly is extendable and contractible by a screw mechanism comparable to that, for example, set forth in US-A-3518890, such that when the telescopic leg is vertically extended, it can support a trailer on the foot mechanism, and when retracted upwardly can be suspended beneath a semi-trailer or the like. Operation of the screw mechanism is through a conventional gearbox 20 actuated as by a crank (not shown) through an input shaft 22. An output shaft 26a can connect to a cross shaft (not shown) to the second leg (not shown) in conventional fashion. The lower outer end of inner tubular leg 16 has a plate 18 affixed thereto as by welding. Beneath this plate and welded thereto is a tubular abutment member 26 elongated transversely relative to the vehicle direction of movement. As shown, it is rectangular in cross sectional configuration, preferably square. This hollow abutment member serves as a housing for an elongate tubular axle 32 extending through the abutment housing. It has an inner width and height just larger than the outer diameter of the axle it receives, and a length less than that of the axle, so that the axle ends protrude therefrom. Suspended from the ends of the axle 32 is a foot subassembly or shoe 40. This foot subassembly 40 includes a ground engaging base plate 42 having a pair of spaced side flanges or plates 44 extending upwardly therefrom and made integral therewith as by welding. The lower ends of plates 44 preferably extend outwardly diagonally, as shown, for reinforcement. These side plates 44 have horizontally aligned orifices 48, each of vertical slot-type configuration. The width of the orifices is slightly larger than the outer diameter of axle 32 and the height considerably greater than the diameter of axle 32 to allow vertical "play" movement of this axle. When the foot is suspended by an elevated leg, the dimension by which these orifices 48 is vertically longer than the diameter of axle 32 is significantly greater than the vertical clearance between the lower abutment surface of abutment housing 26 and the top of the underlying resilient pad 50 to be described. This is for purposes hereinafter noted. The bottom surface of abutment housing 26 is flat, the corner portions being radiused as depicted in Figs. 3 and 4. When the landing gear leg is elevated, shoe 40 is suspended on axle 32 via side plates 44, the axle resting against the inside bottom surface of abutment housing 26. Side plates 44 form two parallel walls of a pocket at the upper surface of the base plate 42 of foot 40. The front and rear walls of this pocket are defined by a pair of inverted L-shaped plates 52 of a height preferably somewhat greater than the height of resilient pad 50. The upper outwardly extending flanges of these inverted L-shaped plates have been found highly effective in providing the strength necessary to resist deformation thereof when the resilient pad is under compression due to the weight of a loaded trailer. Specifically, the structure can accommodate a load even up to 45000 kg, although using a hollow housing. This is in contrast to prior landing gear devices. Resilient cushion 50 has an at rest configuration basically like that depicted in Figs. 6 and 7. More specifically, it comprises a generally rectangular rubber member approximately twice as long in its transverse dimension, i.e., crosswise of the trailer to be supported, than in its fore-to-aft dimension. The side walls 50' are tapered upwardly inwardly, especially at the front and rear walls thereof. The resilient pad is retained in its pocket by a friction fit achieved with four small protrusions 50a extending forwardly and rearwardly, to be deformed when the pad is pressed into position. Preferably, the front and rear walls of the pad also have central notches 50b, and there is a tapered orifice 50c in the centre of both ends thereof. The tapered walls 50', notches 50b and tapered orifices 50c enable temporary rubber position transfer laterally when the unit is under vertical load. Axle 32 is held in abutment housing 26 by locking pins 60 extending through orifices 32' through the opposite ends of the axle extending beyond the ends of housing 26. Drain holes in the foot at the bottom of the pad allow water to drain out of the pocket. When the telescopic leg is vertically extended and put under load, this load is not initially applied to a leg 32 since the clearance between the bottom surface of abutment housing 26 and the top of pad 50 is significantly less than the clearance between the outer diameter of axle 32 and the top of slot orifices 48. Application of the full load to abutment 26 causes it to depress into the resilient pad, forcing portions of the rubber pad laterally outwardly into the clearances for and aft of abutment 26, i.e., between it and front and rear support walls 52 (Fig. 3). This condition is shown somewhat exaggerated in Fig. 3. As load is progressively increased on the assembly, by cranking down of the inner leg and the attached foot, some of the load begins to be applied to axle 32 because the pad is then sufficiently deformed to cause axle 32 to approach the bottom ends of slots 48. This preferably begins to occur when the load applied is a predetermined amount preferably in the amount of about 6,800 to 9,100 kg applied to each leg, i.e., 13,600 to 18,200 kg on both legs. As the load exceeds about 11,300 kg per leg, the axle bears all of the excess load above the predetermined maximum load, i.e., preferably above the 11,300 kg amount, with the resilient pad still bearing the remaining 11,300 kg load, but not more. This controlled loading is achieved by selecting the difference between the clearance of abutment 26 from the top of pad 50, and axle 32 from the bottom of slots 48. It has been found that the polygonal configuration of the abutment housing, particularly the square cross sectional configuration as illustrated, resists deformation under the inward pressure of the resilient material against the walls thereof under load conditions better than a cylindrical housing of circular cross sectional configuration. In the illustrated embodiment, the distance front to rear between the inner surfaces of fore-and-aft support walls 52 is 76.2 mm (three inches), while the front to rear outer dimension of housing abutment 26 is 63.5 mm (two and one-half inches), thereby leaving approximately a 6.35 mm (one-quarter inch) clearance at the front and at the rear. Further, the taper on the edges of the 25.4 mm (one inch) thick pad is approximately 6.35 mm (one-quarter inch) across on each of the front and rear sides thereof. The wall taper is offset, therefore, about 25 percent of the pad height, for an angle of taper of about 22 1/2 degrees. These combined features enable up to about 20 degrees articulation fore-to-aft of the foot relative to the leg as depicted in Fig. 4. Yet the structure has fully adequate support in such condition for heavy loads. The rubber pad is preferably an SBR (styrene-butadiene copolymer), such as SAE J200 5AA 725A13B13F17. Other suitable resilient elastic materials, preferably rubber, can be employed, such as GR-S or Buna-S. The side clearance between the ends of abutment housing 26 and side plates 44 is relatively small, permitting articulation side-to-side of up to about five degrees. The exposed rubber cushion can be readily visually observed to determine its condition. If the resilient member deteriorates and/or the foot of the structure is damaged, the foot can be quickly removed for replacement of the pad and/or replacement of the entire foot subassembly. More specifically, one or both locking pins 60 extending through orifices 32' (Fig. 5) in the ends of axle 32 can be driven out as by a punch, allowing axle 32 to be removed, thereby dropping the foot subassembly 40 from the leg for replacement of the pad and/or foot. The new one is installed simply by inserting the axle back into position and driving in a new locking pin.

Claims: A landing gear assembly comprising a telescopic leg (12), a foot (40), a suspension axle (32) suspending the foot from the leg in a manner allowing a vertical movement therebetween, a load support abutment (26), and a resilient pad (50) beneath the abutment and engageable to be depressed by the abutment when the assembly is under compressive load, characterised by the abutment (26) being in the form of a housing around the suspension axle, and by the suspension axle, foot, and leg being adapted to restrict the said vertical movement to limit the maximum load applied to the pad by the abutment and to cause load amounts exceeding the said maximum load to be transmitted from the foot to the leg via the suspension axle. A landing gear assembly according to claim 1 wherein the potential amount of the said vertical movement is significantly greater than the amount of vertical abutment movement which causes depression of the resilient pad. A landing gear assembly according to claim 1 or claim 2 wherein the resilient pad (50) is on the foot (40) and the abutment is on the leg (12). A landing gear assembly according to claim 3 wherein the foot (40) has a pocket retaining the resilient pad (50), the pocket having front and rear walls (52) with clearance relative to the abutment (26) to allow substantial fore-and-aft articulation between said foot and said leg. A landing gear assembly according to claim 4 in which the front and rear walls (52) are of inverted L-shape and the pad (50) has upwardly inwardly tapered front and rear walls. A landing gear assembly according to claim 4 or claim 5 including a clearance between the abutment (26) and the pocket retention walls (52) sufficient to allow approximately 20 degrees fore-to-aft articulation of the foot relative to the leg when under compressive load, and the foot (40) has approximately five degrees side-to-side articulation under compressive load. A landing gear assembly according to any of claims 3 to 6 wherein the suspension axle (32) fits into vertically elongated slots (48) to allow the said vertical movement. A landing gear assembly according to any one of claims 1 to 6 including vertical plates (44) on the foot having a pair of vertical slots (48) receiving the ends of the axle (32) for vertical movement of the axle in the slots, the abutment (26) being spaced from the pad a certain distance when the foot is suspended beneath the leg and the assembly is not under compressive load, the certain distance being less than the potential movement of the axle in the slots. A landing gear assembly according to any of claims 1 to 8 wherein the abutment (26) is a tubular member of polygonal cross sectional configuration, preferably of rectangular cross section. A landing gear assembly according to claim 1 in which the foot (40) comprises a base plate (42), a pair of spaced vertical plates (44) having vertically extending slots (48) therein receiving the opposite ends of the axle (32), and a pair of walls (52) extending between the vertical plates (44) to form a pocket receiving the pad (50). A landing gear assembly according to claim 10 in which the abutment (26) has a flat bottom surface for engaging the pad (50). A landing gear assembly according to any of claims 4, 5, 6, 10 and 11 in which the pad (50) has a friction fit in the pocket. A landing gear assembly according to any of claims 1 to 12 in which the pad (50) is visible from the exterior of the assembly for determining the condition thereof. A landing gear assembly according to any of claims 1 to 13 in which, when the leg is unloaded, there is clearance between the abutment (26) and the pad (50).

Inventors: HEEB JOHN P, HUNGERINK GERALD W, HEEB, JOHN P., HUNGERINK, GERALD W.
Applicants: HOLLAND HITCH CO, HOLLAND HITCH COMPANY
Application year: 1990
Main classification: B60S9
IPC codes: B60S9