WO1989006199A1

WO1989006199A1 - Loading ramp

Info

Publication number: WO1989006199A1
Application number: PCT/GB1989/000007
Authority: WO
Inventors: Woldemar Reinhold Petri; Howard Gallup
Original assignee: Canaramp Corp; Asquith, Anthony
Priority date: 1988-01-09
Filing date: 1989-01-06
Publication date: 1989-07-13
Also published as: GB2213463A; GB8800432D0; AU2933989A; GB8900299D0; GB2213463B

Abstract

The ramp (2) is for use in loading/unloading a pick-up truck. The ramp is foldable about a central hinge (5). When folded, a pair of the ramps constitute the tailgate of the truck. When unfolded, the ramp is 3 m long by 25 cm wide by 6 cm deep, has a load capacity in excess of that of the truck, and is light enough to be manhandled easily by one person. The ramp is made from extruded aluminum sections: in one embodiment, extruded channels (7) are welded lengthwise to a platform (6); in another, the ramp is a one-piece extrusion. The cross-section of the ramp includes upper and lower flanges, held together with four webs (10; 81).

Description

LOADING RAMP

This invention relates to loading ramps, of the kind used for loading and unloading transportable equipment of various kinds from pick-up trucks and trailers.

BACKGROUND TO THE INVENTION

A loading ramp for use in this kind of application should be:-

(a) Of adequate load capacity: the ramps should be designed to have at least as high a load capacity as that of the pick-up truck or trailer.

(b) Of adequate length: the angle at which the ramp rests should not be too steep;

(c) Easily stowable on the truck or trailer. Also, the ramps should be light in weight, and easily movable into position;

(d) Safely and securely attached to the truck or trailer during use; not only for safety reasons, but to avoid damaging the load.

The use of a pair of wooden planks as loading ramps has lo g been recognised as too crude and too dangerous. However, although improvements of course have been made, the typical loading ramps used at the present time on pick-up trucks and small trailers really amount to no more than planks. THE PRIOR ART

US patents 3580404 (MOSER, Hay 71) and 2900094 (FERGUSON, Aug 59) show ramps that are hinged permanently to the truck. The ramps fold up about an axis that lies transversely to the truck. Such an arrangement is far too expensive for use on a pick-up truck, and also the folded ramps protrude upwards above the general level of the truck, which is not acceptable in a pick-up truck. That this is so is borne out by the ramp shown on the pick-up truck in US patent 2727781 (D'EATH, Dec 55).

US patent 4527941 (Jly 85) shows a concertina-type of extendable ramp, and is an example of how, once the design of a ramp starts to go away from a simple plank, the load capacity of the ramp is much reduced.

US patent 4478549 (STELLY, Oct 84) shows a ramp attached to the folded-down tailgate of a pick-up truck, in which the load capacity of the ramp and tailgate assembly is unacceptably small.

US patents 3642156 (STENSON, Feb 72) and 4601632 (AGEE, Jly 86) also show ways of attaching ramps to the tailgate, but again the load capacity of the ramps shown must be very small.

There are many examples also of ramps which include intermediate supports, ie supports ion the form of posts or legs which extend down to the ground from various points along the length of the ramp. Such legs are not suited for general purpose ramps of the kind that are suitable for use with pick-up trucks and small trailers, where ease of use is very important.

GENERAL DESCRIPTION OF THE INVENTION

The invention lies mainly in the form or shape of the cross-section of the ramp. The form includes an upper flange element, a lower flange element, and web elements.

It is of the essence of the invention that the ramp be light, yet strong. In order to keep the weight of the ramp down to a minimum, the upper flange element doubles as the platform or roadway of the ramp, which directly receives the load. A ramp under load of course is stressed predominantly in the bending mode, and the upper flange element is also the component of the ramp which supports the compressive component of the bending stress. Similarly, the lower flange element supports the tensile component of the bending stress. The main function of the webs is to hold the two flanges apart, so that each may play its part in supporting the overall stress.

As a beam, a ramp is characterized as very wide in relation to its depth. In any beam, there is a tendency, when under a bending load, for the unsupported portions of the flanges to deflect inwards, ie towards each other. This is especially a tendency in wide beams. It is therefore important; in the invention, that the cross-sectional shape should include a number of webs, whereby the unsupported portions of the flanges are kept to a minimum. Preferably, in the invention, four webs are provided, spaced apart equally across the width of the cross-section; less than three webs would mean that the flanges would not be supported properly to accommodate bending stresses, and less than three webs is therefore outside the invention.

The theoretical strength performance of any beam can only be realised if the flanges of the beam can be kept properly spaced apart. If the beam is relatively very wide in relation to its depth, ie if the beam is more than twice as wide as it is deep, as is the case with a ramp, the problem of the flanges deflecting inwards towards each other, needs careful attention. The Invention provides the several webs, disposed across the width of the beam, to permit the flanges to achieve the full bending-resistance performance of which they are capable. Any portions of the upper or lower flanges that were to lie a long way from a web could not contribute efficiently to the strength of the beam.

The several webs also serve to hold the cross-sectional shape steady against other kinds of buckling: for example against lateral shearing or splaying.

It is important that the two flanges be not too disparate as regards their cross-sectional areas. Thus, ideally, there should be as much metal in the lower flange element as in the upper flange element, so that the compressive and tensile stresses are numerically equal. However, the upper flange can be permitted to be of greater area, because the compressive forces in the upper flange can lead to buckling of the upper flange, which is not possible in the lower flange, and also because the upper flange may suffer extra abuse as a result of its role as the load-receiving roadway or platform of the ramp. In the invention, however, the upper flange element of the cross-section should not contain more than about twice the amount of metal as is contained in the lower flange element. If the upper flange were to be heavier than that, in relation to the lower flange, the material of the ramp would not be used efficiently, and would be outside the inventon.

Basically two arrangements of the cross-section of the ramp are contemplated in the invention. First, the ramp section may be formed by providing the upper flange element or roadway as a flat sheet, by providing two extruded channel sections, and by welding the two channel sections in a spaced apart, side-by-side relationship lengthwise along the upper flange element. The side walls of the channel sections comprise the web elements, and the bases of the channel sections comprise the lower flange elements, in the second arrangement, the ramp section is formed as a one-piece extrusion, with all the elements present in the shape of the extruded section.

For the purposes of this specification, the expression "integral and unitary" is used in relation to two components where the two components are both present in a single piece of metal, or where the two components are joined together in such a way (for example by welding) that it is as if the components were both present in a single piece of metal.

In the welded-channel arrangement, the sides of the channel are welded to the platform, and serve to keep the platform flat, under load. The result is that the stresses and strains may be fed efficiently to all areas and zones of the platform, which then may all play their part in effectively supporting the stresses in the platform. If the loads were to be fed into the platform in an inefficient manner, only a portion of the platform would support the stresses, and the rest would be wasted.

The channels act also to keep the ramp rigid against possible torsional distortions, and make the ramp generally well able to cope with off-centre loads, and other spurious effects.

Preferably, in the invention, the material in the base of the channel is thicker than the material of the walls of the channel and of the platform. With the thicker bases, the ramp is able to support the bending stress with a good efficiency of use of material, since the platform is correspondingly wider than the bases. In order that the base of the channel may be of a different thickness fzom the walls of the channel, preferably the channel is of extruded form.

It is an aim of the invention to provide a ramp which has an adequate load capacity, which is light in weight, inexpensive, and capable of not compromising the design parameters mentioned above. It is recognised in the invention that the platform with welded-on channels, as described, achieves that aim.

One of the main advantages of the ramp design of the invention lies in the manner in which hinges can be incorporated into the ramp structure. The typical pick-up truck is about 150 cm wide, and it is recognised that a ramp with a length of 300 cm will have a gentle enough slope, in use, to permit loads on the ramp to be easily controlled. A ramp that folds into two halves (or into one half and two quarters) where the half is roughly 150 cm long, is therefore easy to stow on the truck, yet not too steeply sloping when in operative use.

The ramp of the invention is such that hinges may be incorporated without unduly increasing the cross-sectional depth of the ramp. As with the ramp itself, in the invention, the forces on the hinge when the ramp is under load are fed into the flange elements in a most efficient way, so that virtually all regions and zones of especially the lower flange elements are stressed evenly.

Also, in the invention, the hinges may be so arranged that the ramp may be folded flat, for easy stowage when not in use.

In order that the invention may be further understood, a practical embodiment of the invention will now be described.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

In the drawings -

Fig 1 is a pictorial view of the underside of a folding ramp which embodies the invention; Fig 2 is a side elevation of the ramp of Fig 1; Fig 3 is a cross-section on line 3-3 of Fig 2; Fig 4 is a view of a portion of the ramp of Fig 1 from underneath; Fig 5 is a cross-section on line 5-5 of Fig 4; Fig 6 is a cross-section on line 6-6 of Fig 4; Fig 7 is a pictorial view of the tail of a pick-up truck, showing the manner in which a pair of the ramps are used, and stowed, on the truck; Fig 8 is a view corresponding to the view of Fig 7, but shows the ramps in a stowed position; Fig 9 is a view corresponding to the view of Fig 8, but shows the stowed ramps moved to a tailgate position; Fig 10 is a side elevation of an end of an alternative ramp; Fig 11 is a cross-sectional view of another alternative ramp.

The ramps shown in the accompanying drawings and described below are examples of ramps which embody the invention. It should be noted that the scope of the invention is defined by the accompanying claims, and not necessarily by features of specific embodiments.

The ramp 2 in Fig 1 comprises a top section 3 and a bottom section 4. The two sections are hinged together about a hinge 5.

Each section 3,4 comprises a platform 6 and two channels 7. The platform is of sheet aluminum.

Each channel 7 comprises a base 9 and two side walls 10. The channel 7 is formed as an aluminum extrusion. The channels 7 are continuously-welded along the tops of all four of the side walls 10 to the underside of the platform 6, to form a unitary structure. Spacers 12 are welded between the pairs of channels 7.

The hinge 5 includes a hinge-pin 14. The manner of attaching the leaves of the hinge 5 to the respective sections 3,4 of the ramp will now be described. A single leaf 16 is provided for the bottom section 4. The leaf 16 is formed as an aluminum extrusion, the extruded cross-section having a flat portion 18 and a boss 20.

The leaf 16 is cut to such a length as to fit between the bases 9 of the pair of channels 7 of the bottom section 4, and the leaf is welded in place between the two channels.

The top section 3 of the ramp 2 is provided with two leaves 21. The same extrusion as was provided for the leaf of the bottom section is used for the leaves of the top section. In the hinge area, the bases 9 of the channels 7 of the top section 3 are cut away to the tapered shape 23 as shown in Fig 3. The flat portion 18 of the leaf 21 is formed to a complementarily tapered shape, and the leaf 21 is welded into the cut-out shape 23 of the base 9.

The thickness of the flat portion 18 of the leaves 16,21 is nominally equal to the thickness of the base 9 of the extruded channel 7.

The hinge-pin 14 passes through aligned holes in the bosses 20 of the leaves 16,21. Reinforcing plates 25 are welded to outer side walls 10 of the channels of the bottom ramp, to locate the ends of the hinge-pin 14.

A hinge constructed in the above manner will usually be stronger than the rest of the ramp. If a ramp with such hinges is loaded to destruction, it will usually be found that the ramp falls at some area other than the hinge, even though the bending moment on the ramp is greatest at the hinge area of the ramp.

The reason for the very high strength of the hinge may be explained as follows. The main type of stress to which the ramp is subject is bending stress. The platform 6 supports the compression, and the bases 9 of the channels 7 support the tension, associated with the bending stress. The axis of the hinge-pin 14 is located in the plane of the tension-supporting bases 9 of the channels. The forces on the hinge, therefore, when the ramp is opened out and in use, tend to reduce down to a simple transfer of tension from the bases 9 of the channels of the top section 3 to the bases 9 of the channels of the bottom section 4. The rigidity of the overall cross-sectional shape of the ramp sections is such that any spurious side forces or twisting moments on the hinge may be ignored. This absence of spurious forces means that the hinge may be designed to support simple tensile forces, which are fed directly into the leaves. It is this simplicity in the manner in which the forces are applied to the hinge that gives the hinge its strength.

The ramp sections themselves are also strongly resistant to the kinds of bending and other stresses and distortions likely to be encountered during use of the ramps. The compression induced by the bending stresses imposed on the ramp during use, is taken by the platform 6. The bending- induced tension is taken by the bases 9 of the channels. Both the platform and the bases are amply strong enough to support these forces, and the side walls 10 act as webs to maintain the platform and bases in the correct relationship to each other to enable them to support the said stresses without buckling or other distortion.

The ramps of the invention may be used in pairs, for the purpose, for example, of unloading equipment from pick-up trucks and the like. Fig 7 shows an example of a manner in which the ramps may be mounted on the truck.

When modifying a pick-up truck for use with the ramps of the invention, the tailgate of the pick-up truck 30 is removed and set aside. The tailgates of pick up trucks are generally pivoted about a pair of pins set one each in the left and right side members 32 at the rear of the truck body. One such pin is illustrated at 34. It will be noted that if the tailgate were to be left in place, and if the ramps were to be supported on the tailgate, all the stresses of loading and unloading would be taken by such pins, and the pins, and indeed the side members 32, were not designed to support such loads.

Similarly, if the ramps were to be supported by the floor 36 of the truck, the operations of loading and unloading would apply concentrated stresses at the ramp-resting locations in the floor, which again would far exceed the designed capacity of that location of the floor.

It is preferred, in the invention, therefore, that the ramps be attached, not to the tailgate, nor to the floor of the truck, but to the bumper 38 of the truck. The bumpers of pick-up trucks are generally provided with a flat top-surface 40, which is set a small distance below the level of the truck floor 36. The Fig 7 arrangement, of the bumper in relation to the floor, is virtually universal in pick-up trucks.

Four brackets 41 are bolted to the top 40 of the bumper 38. These brackets carry a bar 43, on the ends of which respective left and right channels 45 are carried, the channels being pivotable with respect to the bar 43.

As shown in Fig 2, the upper end of the top section 3 of the ramp is provided with a hook 27, and the lower end of the bottom section 4 is tapered.

In use of the ramps, the hooks 27 are placed over the bar 43. Preferably, the brackets 41 should be so placed as to straddle the hooks 27, but it does not matter too much if the hook actually rests on one of the brackets, since the ramp is wide enough still to be stable. The bar 43 is strong enough that the ramps may be placed at any location along the bar.

After use, the operator folds the ramps about their hinges 5, and slides the two ramps within the channels 45. The assembly of the ramps 2 in the channels 45 thus comprises a tailgate for the truck, which may be lifted up, and secured in position, like a conventional tailgate.

It may be noted that this manner of stowing the ramps provides no more restriction than would a conventional tailgate as to whether the truck may be provided with a cap.

It will be inferred that the dimensions of the ramps are to some extent dictated by the dimensions of conventional pick-up trucks. Thus, the width of the ramp should be such that the two ramps placed side by side in the channels 45 are roughly equal to the height of sides 32 of the truck. It has been found that a ramp width of about 23 cm serves for many different makes of truck.

Similarly, the length of the ramp is dictated by the width of the truck, since the folded length of the ramp fits widthwise across the truck. A ramp length (overall) of 304 cm, ie a folded length of 152 cm, fits most trucks. Trucks do vary a few cm as regards width: for all but the narrowest truck, the ramps would have some clearance side to side in the channels 45. The designer must of course see to it that the ramps cannot inadvertently fall out of the channels, and the appropriate dimensional checks must be carried out in respect of each truck installation.

The height of the top 40 of the bumper also varies only slightly truck to truck. A ramp with a length of 304 cm rests at an angle of about 12 degrees to the ground, which is a gentle enough slope that items of equipment may be rolled up and down the ramps under an adequate degree of control.

It is important, for safety reasons, that the top of the ramp should be securely and firmly anchored to the truck during loading and unloading. As described, the hook 27 of the ramp of the invention is hooked over the bar 43, and it is recognised that this is an adequately secure manner of attachment. The bar 43 therefore serves two purposes: not only to define the pivot axis of the "tailgate" (the channels/ramp assembly) but also to provide a secure structure upon which the hook 27 may be attached.

As may be inferred from Fig 7, the structure of the truck bed, in the region where the ramp is to be attached, offers very little facility for securely attaching the ramp. Thus, if the bar 43 were not present, it would be quite difficult to arrange that the ramps would do anything more than mrerly rest against the end of the truck floor 36. Clearly, it would be dangerous to use ramps that merely rest against the truck.

The ramp described is, as mentioned, over 3 metres long when unfolded. It might be thought that such a ramp, if it is to be strong enough to support a reasonably heavy weight, would have to be of a heavy, cumbersome construction, and that the cross sectional dimensions would have to be large. However, this is not the case in the invention. The 3-metre ramp weighs about 15 kg, and its cross section has a depth of 6 or 7 cm; and yet the rated load capacity would be in the 1000 kg category, with a perfectly adequate safety factor. Thus, the load capacity of the pair of ramps exceeds the load capacity of most pick-up trucks.

This degree of strength, coupled with lightness and a low cross sectional height, arises because of the very efficient structure of the ramp. The platform of the ramp does not just act as a roadway, but helps to support some of the stresses induced in the ramp. The bases 9 of the channels are thicker than the material of the platform, because the width of the bases is less than the width of the platform. The rest of the structure of the ramp is aimed at isolating the platform and bases from other forms of stress, so that these areas can concentrate on the tension and compression stresses induced in the ramp by the bending loads. The side walls of the channels take proportionately less stress, and so the side walls may be thinner than the bases. It is recognised that the requirements of the ramp are met very conveniently by extruding the channels in aluminum.

It has been found that a ramp with the following dimensions is light enough to be easily picked up and manhandled by a single person without assistance, and yet the ramp has a load capacity such that any load that can legitimately be placed in a pick up truck can be loaded and unloaded with the ramp:

- width of platform = 220 mm;

- height of side walls = 60 mm;

- thickness of platform and side walls = 2.6 mm;

- width of base walls = 45 mm;

- thickness of base walls = 3.2 mm;

- spacing between adjacent channels = 100 mm.

In the above ramp, the channels are secured to the paltforra by continuous welding. Access is provided for welding the inner side walls by virtue of the space between the two side channels.

Apart from the need that the ramp cannot be very deep in cross-section, the ramp must also fold quite flat, ie through a complete 180 degrees. The layout of the hinge must not compromise this requirement, and it will be noted that the the hinge 5 as described permits the ramp to fold quite flat. At the same time, the hinge must be strong enough to support the loads placed on it, bearing in mind that the bending moment on the ramp is at its greatest at the midpoint of the ramp, which is where the hinge is located.

Fig 11 shows an alternative manner (to that of Fig 2) in which the form of the ground-end of the ramp may be made. The designer must see to it that the extreme end of the ramp is actually touching the ground, or almost so: because, if the end were clear, it could happen that when a load was placed on that end, the other or top end of the ramp might tip upwards. It is somewhat inconvenient to cut the channel off at an angle more acute than about 20 degrees, but in fact it would be possible for the ramp of the invention to be used at much smaller angles than that. The nose 76 in Fig 11 is shaped to suit, and is simply welded in place on the square-cut end of the section.

Fig 12 shows an example of a ramp which is made entirely as a one-piece extrusion of aluminum, not as a composite of welded components.

The cross-section includes an upper flange element 78, a lower flange element 80, and four web elements 81. The dimensions of the cross-section, which has been found to be highly satisfactory in terms of lightness as against load carrying capacity, are as follows:-

- width of upper flange element = 250 mm

- height of web elements = 60 mm

- space between adjacent web elements = 55 ^~m

- thickness of all said elements = 2.6 mm

This is a much more demanding extrusion than a simple channel, of course, since the cross-sectional shape includes completely-surrounded holes; but the extra expense of the one-piece extrusion is offset by the elimination of the welding operations. Because there is no welding, there is no need to povlde access for welding, so that the lower flange element 80 may extend continuously right across the width of the ramp. Because the lower flange element has so much width, it need not have so much thickness, and in the extrusion of Fig 12 the elements can all be extruded to the same thickness.

Also, in the one-piece extrusion, there is no need for the spacers 12 to be provided. One purpose of the spacers 12 was to ensure that the bases of the channels could not spread apart laterally when the ramp was under load, and that function is already catered for in the one-piece extrusion.

Claims

CLAIM 1. Loading ramp, wherein:

the ramp is suitable for facilitating the movement of a load up to, or down from, a height;

the ramp includes an upper flange element, a lower flange element, and web elements;

the upper flange element includes a roadway, which is suitable for receiving the load directly thereupon;

in use, under load, the ramp is so arranged as to be subject to heavy bending stress;

the arrangement of the ramp is such that the upper flange element is subject to, and supports, the compressive component, and the lower flange element is subject to, and supports, the tensile component, of the said bending stress;

the width of the ramp is several times greater than the depth of the ramp;

each web element is unitary and integral with both the upper flange element and the lower flange element;

the web elements are spaced from each other across the width of the ramp; the ramp includes at least three of the said spaced web elements;

and the tension-supporting cross-sectional area of the lower flange element is not less than half the compression- supporting cross-sectional area of the upper flange element.

CLAIM 2. Ramp of claim 1, wherein the ramp includes four of the said spaced webs.

CLAIM 3. Ramp of claim 1, wherein the web elements are unitary and integral with at least one of the said flange elements by virtue of the fact that the web elements are continuously welded lengthwise onto that flange element.

CLAIM 4. Ramp of claim 3, wherein:

the ramp includes a platform, having a topside and an underside, and two U-shaped channels, each having a pair of side walls and a base wall;

the two U-shaped channels are welded, in a spaced-apart, side-by-side relationship, lengthwise along the underside of the platform; whereby the platform comprises the upper flange element, the said four side walls of the channels comprise the web elements, and the two base walls of the channels together comprise the lower flange element.

CLAIM 5. Ramp of claim 4, wherein, in respect of each channel, the side walls are thinner than the base wall.

CLAIM 6. Ramp of claim 5, wherein the cross-section of the ramp has substantially the following dimensions:

- width of platform = 220 mm;

- height of side walls = 60 mm;

- thickness of platform and side walls = 2.6 mm;

- width of base walls = 45 mm;

- thickness of base walls = 3.2 mm;

- spacing between adjacent channels = 100 mm.

CLAIM 7. Ramp of claim 2, wherein the web elements are unitary and integral with both the upper and lower flange elements by virtue of the fact that the web elements and the flange elements are formed together in one single extruded section.

CLAIM 8. Ramp of claim 7, wherein the lower flange element extends uninterruptedly across the width of the ramp.

CLAIM 9. Ramp of claim 8 wherein the cross-section of the ramp has substantially the following dimensions:

- width of upper flange element = 250 mm

- height of web elements = 60 mm

- space between adjacent web elements: 55 mm

- thickness of all said elements = 2.6 mm

CLAIM 10. Ramp of claim 7, wherein:

the ramp is provided with side wings, which, in use, protrude above the level of the upper flange element;

the ramp includes lengthwise-extending slots, and the side wings include complementary tongues, the arrangement being such that the side wings may be assembled and disassembled lengthwise with repsect to the ramp.

CLAIM 11. Ramp of claim 1, wherein:

the ramp includes hinges, the axis of which lies across the width of the ramp;

and the ramp is in two sections, which are relatively foldable about the hinge axis.

CLAIM 12. Ramp of claim 11, wherein:

the axis of the hinges lies in the plane of the lower flange element;

and the hinges include leaves, which are welded to the lower flange element.

CLAIM 13. Ramp of claim 1, wherein the ramp is of aluminum.

CLAIM 14. Ramp of claim 11, wherein the ramp is provided with a hook at one end, and is provided with an angled nose at the other end.

CLAIM 15. A combined ramp and tailgate assembly for a vehicle, wherein:

the assembly includes a pair of the ramps as claimed in claim 11;

the ramps are stowable on the vehicle when not in operative use; the assembly includes left and right channel members, and a bar upon which the channel members are pivoted;

when stowed, the ramps are folded, and the folded ramps are stowed in, and between, the channel members and the ramps are disposed one above the other across the width of the vehicle, the assembly being so arranged on the vehicle as to comprise the tailgate of the vehicle.

CLAIM 16. Assembly of claim 15, wherein:

the bar is attached firmly to the rear of the vehicle;

each ramp is provided with a hook at one end, which is engageble, when the ramp is ready for operative use, with the said bar.