GB2380712A

GB2380712A - Trailer with two sets of wheels

Info

Publication number: GB2380712A
Application number: GB0124085A
Authority: GB
Inventors: Robert Ager
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-10-08
Filing date: 2001-10-08
Publication date: 2003-04-16
Anticipated expiration: 2021-10-08
Also published as: GB2380712B; GB0124085D0

Abstract

A trailer comprises a chassis, a first set of wheels 30'' mounted on the chassis such that the chassis is supported only by the first set of wheels at a first level of ground clearance, and a second set of wheels 44 removably mounted on the chassis such that when the chassis is supported only by the second set of wheels it has a different level of ground clearance. The second set of wheels preferably provide a greater level of ground clearance and are supported by means of stub axles (42, figure 1). The trailer may be intended for carrying/launching a boat, whereby the first set of wheels are suitable for immersion in water and the second set of wheels are attached to the trailer when the trailer is to be towed along a road. The trailer may also be provided with brakes, suspension units for the wheels and means 62 for raising the chassis.

Description

The present invention relates to trailers and is particularly relevant to trailers that are used for transporting and launching boats.

Road trailers for boats are required to support a boat in a safe and secure manner when towed behind a towing vehicle, especially when used on public roads. When the boats in question are relatively small, for example less than 7 metres in length, it is also often desirable to be able to use a trailer for launching and recovering the boat directly from a trailer in the water without the need for cranes or other such lifts near a dock or jetty. When launching a boat from a trailer, the trailer with the boat on it is advanced into the water until the boat floats off, and is then removed from the water until it is desired to recover the boat at which time the operation is reversed. When using a trailer to launch a boat directly, it is desirable that the ground clearance is as low as possible so that the dept of water required to float the boat from the trailer is minimised. This means that generally trailers used for launching boats have relatively small wheels. However, for road use a greater ground clearance is preferred since this allows the use of flexible suspension units and larger wheels which can incorporate braking systems, inflatable tyres, etc. , and reduces rotation rates when towed at normal road speeds. While it is possible to launch from a road trailer, it is undesirable since advancing the trailer into the water generally means that the wheels and associated bearings, suspension and braking systems are also immersed in the water. This can lead to corrosion and damage or failure of these components which can be particularly dangerous, especially if failure occurs when towing a loaded trailer on a public road.

When the boats in question are relatively small and light, for example less that 250 kg, it is relatively easy to manhandle a boat from a road trailer onto a launching trolley (typically relatively lightweight wheeled chassis with supports for a boat) which can then be manhandled for launching and recovery. However, for convenience or when the boat is greater than 250 kg, it is desirable to avoid the need to manhandle a boat between a road trailer and a launching trolley.

One approach which is in common use to allow road towing and launching directly from a launching trolley is the so-called"combination trailer", a combination of a road trailer and a launching trolley. The boat is carried by the launching trolley (which typically includes

supports or cradles specifically for that purpose), and the launching trolley carrying the trolley is loaded directly onto the road trailer for towing. The road trailer can be fitted with road wheels and associate systems and a towing attachment, at is configured so that the launching trolley can be secured safely to it. Clearly it is necessary for launching trailer to be able to support the boat, and the road trailer to be able to support both the boat and the launching trolley. When the boat is still relatively light, for example less than 500 kg, the launching trolley can still be relatively lightweight since the loads involved in launching are relatively low. Consequently, the additional weight of the trolley to be supported by the trailer is not a significant issue in the construction of the road trailer since road trailers are already substantially constructed to deal with the loads of towing on normal roads. However, as the boat becomes larger, the weight of the launching trolley increases such that it makes a significant contribution to the overall weight of the boat, trolley and trailer combination. Since any vehicle will have a limit to the weight it can tow, the use of relatively heavy trolleys and trailers reduces the possible payload and so limits the size of boat that can be safely trailed on normal roads, especially when using normal road vehicles such as cars.

It is an object of the present invention to provide a trailer which can give both road trailer and trolley functions while optimising the useful payload.

The present invention provides a trailer having a chassis, a first set of wheels mounted on the chassis such that when the chassis is supported only by the first set of wheels it has a first level of ground clearance, and a second set of wheels removably mounted on the chassis such that when the chassis is supported only by the second set of wheels it has a second level of ground clearance that is different from the first level.

Preferably, the second set of wheels can be a pair of units each of which includes a suspension arrangement on which the wheel is mounted and optionally including a braking system. It is preferred that the second level of ground clearance is greater than the first level. Where the wheels of the second set are road wheels and the wheels of the first set can be of smaller diameter that those of the second.

By providing the trailer with a set of removable wheels, it is possible to provide wheels suitable for towing on normal roads which can be removed before the trailer is immersed in

water or otherwise manoeuvred on the first set of wheels while reducing the possibility of damage to the second set of wheels or of their interfering in manoeuvring.

The chassis can be of A section, T section, cruciform, or any other suitable configuration. It is particularly preferred that the chassis includes a hollow cross member. This cross member can be formed as a box section. In such a case, the second set of wheels can be mounted on the chassis by means of stub axles that are inserted into the hollow cross member. The stub axles themselves can have a cross section that prevents their rotation when inserted in the cross member, for example box section or similar or slightly smaller outer dimension than the inner dimension of the hollow cross member. The small amount of relative twist permitted between the hollow cross member and the stub axle can be particularly effective in preventing the stub axle from sliding relative to the cross member when placed under load. For further security, an inter-engaging retaining mechanism can be formed on the wheels and chassis to prevent unwanted separation of the second set of wheels and the chassis.

The chassis can include a braking system having a first part that is permanently attached to the chassis and a second part that is permanently connected to the second set of wheels and releasably connected to the first part.

For ease of operation, the trailer can include an operable support system, such as a jacking system, that can support the chassis while the wheels of the second set are raised clear of the ground for attachment or removal. This system can be separate or can be mounted integrally on the chassis.

Where the trailer is used for a boat, the first set of wheels can be of a type suitable for immersion in water and the chassis can include a cradle or other support structure for the boat.

The trailer of the present invention optimises the useful payload by avoiding the need for a separate trolley for manhandling or manoeuvring, while still allowing full sized road wheel and suspension a braking to be provided on the trailer. The use of such a trailer is not confined to boats, but can also be useful when a low loading trailer is needed for ease of handling of equipment on site, but greater ground clearance is needed for road trailing at normal speeds.

The invention will now be described by means of a specific example as shown in the accompanying drawings, in which : Figure 1 shows a schematic plan view of a trailer according to one example of the invention; Figure 2 shows a schematic side view of the trailer of Figure 1 when supported on road wheels; and Figure 3 shows a schematic side view of the trailer of Figure 1 when supported on trolley wheels.

The trailer shown in the drawings is a boat trailer suitable for use with boats of up to around 7 metres in length. It has an A frame chassis 10 with side members 12 and cross members 14. A front beam 22 carries a towing attachment 16, a jockey wheel 18 with a lowering and raising mechanism 20, and a braking system 21. The towing attachment 16 is typically a socket for use with a ball mounted on the towing vehicle (not shown). Such arrangements are commonly used for towing using normal road vehicles and can include appropriate pivots to allow relative twisting movement of the trailer and towing vehicle. The braking system 21 can be one which automatically applies braking to the trailer if the trailer pushes on the towing vehicle for any reason and can include a lever for manual operation when not attached to the towing vehicle.

The front beam 22 also carries a bow support 24 for a boat to be carried on the trailer, and a cradle 26 is fixed to the front cross member 14. A pair of keel supports 28 are fixed to the rear cross members 14', 14"to complete the supporting arrangement for the boat. It will be appreciated that any suitable arrangements of support pads, cradles and/or rollers can be fixed to the chassis 10 according to the form of the hull to be transported.

Trolley wheels 30 are fixed to the chassis 10 at various positions to allow manoeuvring of the trailer. A front pair of trolley wheels 30'are connected by simple stub axles 32 on either side of the front beam 22. Two pairs of rear trolley wheels 30"are located inside the chassis side members 12 between rear cross members 14', 14"on simple cross axles 34 mounted between pairs of supporting beams 36. The trolley wheels 30 are of relatively small diameter and simple construction. Since the movements of the trailer when supported on the trolley wheels 30 are relatively slow and may involve immersion in water, the wheels 30 can be mounted on the axles 32,34 on simple journals.

A hollow cross member 38 is located at the rear of the chassis 10 between the rear cross members 14', 14". The hollow cross member 38 is formed from a box section beam extending across the chassis 10 between and below the side members 12. Road wheel units 40 are mounted on the chassis by way of box section stub axles 42 which are inserted into the open ends of the hollow cross member 38. The outer dimension of the stub axle 42 is preferably slightly smaller than the inside dimension of the hollow cross member 38, for example a clearance of around 2mm can be sufficient for the purposes of this invention as will be explained below. While the stub axle 42 in this case is also a box section, it is not necessary that this be so. For example, the stub axle 42 could be of I beam or H beam section or any other suitable shape. Waterproof lubricating grease can be applied to the inside of the hollow cross member and the outside of the stub axle 42 to facilitate insertion and removal. The wheel units 40 include road wheels 44, optional mudguards (not shown), flexible suspension units 46 and brakes (also not shown). Inter-engaging loops 48 are provided on the chassis 10 and the wheel unit 40 such that a cotter pin 50 can be inserted to prevent accidental separation of the wheel unit 40 from the chassis 10. A chain 52 can also be provided to further secure the wheel unit 40 to the chassis 10.

Cables 54 extend between the brakes on the wheel units 40 and the braking system 21 on the

chassis. The cables 54 are provided in two parts 56', 56". A front part 56'is connected to the chassis 10 and rear parts 56"are connected to the wheel units 40. The rear parts can be held on the chassis 10 by a locating fixture 58 on a rear cross member 14'and the front and rear parts 56', 56"are joined by a releasable connector 60.

Figure 2 shows the trailer in its configuration for towing on the road. The weight of the trailer (and boat, when present) is carried by the road wheels 44. The front of the trailer is supported by the jockey wheel 18 which is shown in its lowered position to maintain the trailer relatively level. When connected to a vehicle for towing by the towing attachment 16, the jockey wheel 18 is raised clear of the ground in the normal manner.

A jack 62 is positioned under the side member 12. Various jacking arrangements can be used.

A single jack can be used to raise one side at a time, as is shown. Alternatively, a pair of jacks can be used to raise both sides together. The jack (s) can be separate from the trailer (as shown) or integral with the chassis 10.

In order to remove the road wheel units 40, the two parts of the brake cable 56', 56"are disconnected from each other at the connector 60 and the rear part 56"is removed from the locating fixture 58. The cotter pin 50 is removed from the loops 48 and the chain 52 is disconnected. The jack 62 is then operated to raise the wheel 44 clear of the ground, at which point it can be removed by sliding the stub axle 42 from the hollow cross member 38 (Figure I shows the right hand wheel partly withdrawn). The jack 62 is then lowered until the chassis 10 is supported by the trolley wheels 30 (since there can be considerable difference in clearance between the road wheel and trolley wheels, it can be desirable to lower the trailer onto wedges, not shown here, to ease lateral stresses on the trolley wheels while the other road wheel in being removed). This operation is repeated on the other side such that the whole weight of the trailer is carried by the trolley wheels 30 (the jockey wheel 18 is raised such that the front of the trailer is supported by the front trolley wheels 30'). This configuration is shown in Figure 3. The trailer can then be wheeled into position, for example by being pushed into the water to load or unload a boat.

The road wheel units 40 are re-attached by reversing the process described above.

In the example described above, both the hollow cross member 38 and the stub axle 42 are of box section. When the chassis 10 is supported on the jack 62 and the wheel 44 is clear of the ground, the stub axle 42 is easily withdrawn from the hollow cross member 38. The suspension unit 46 mounts the wheel 44 such that its axle is offset slightly ahead of (or behind) the long axis of the stub axle 42. When the wheels 44 support the chassis 10 (and any payload), the offset causes the stub axle 42 to twist slightly in the hollow cross member 38 until the edges of the stub axle 42 engage the inner surfaces of the hollow cross member 38 so as to lock against them. The greater the load, the greater the locking action. If the length of the stub axle 42 is sufficient (in the example described above, each stub axle 42 projects into the hollow cross member 38 by an amount that is about 1/3 of the total length of the hollow cross member 38), this locking effect can be sufficient to hold each wheel unit 40 securely in place while the trailer is being towed, with or without any payload. In such a case, the other retaining mechanisms (pin 48, chain 50) are essentially backups for additional safety. The same locking effect can be obtained with other straight-sided sections for the stub axles 42, for example I-beam, H-beam, etc.. When the wheel 44 is unloaded as the chassis 10 is raised on the jack 62, the offset of the wheel axle and stub axle axis means that the weight of the

wheel 44 unlocks the stub axle 42 from the hollow cross member 38 such that it is easily withdrawn.

The trailer described above is just one example of the invention and various changes can be made while still staying within the scope of the invention. For example, multiple road wheels can be provided on each side, either on a single stub axle and hollow cross member, or each with its own stub axle and hollow cross member. Another variation is that the trolley wheels can be raised and lowered to support the chassis when the road wheels are removed.

The invention is not restricted to boat trailers, but can find use in other forms of trailer where it can be advantageous to load and unload the trailer close to the ground and then increase the ground clearance for towing. Such uses can include, for example, vehicle-carrying trailers, or trailers for heavy plant equipment.

Claims

CLAIMS 1 A trailer, including : i) a chassis ; ii) a first set of wheels mounted on the chassis such that when the chassis is supported only by the first set of wheels it has a first level of ground clearance; and iii) a second set of wheels removably mounted on the chassis such that when the chassis is supported only by the second set of wheels it has a second level of ground clearance that is different from the first level.
2 A trailer as claimed in claim 1, in which the second level of ground clearance is greater than the first level.
3 A trailer as claimed in claim 1 or 2, in which the second set of wheels has a pair of units, and each unit includes a suspension arrangement on which a wheel is mounted.
4 A trailer as claimed in claiml, 2 or 3, in which the chassis includes a hollow cross member and the second set of wheels are mounted on the chassis by stub axles that are inserted into the hollow cross member.
5 A trailer as claimed in claim 4, in which the hollow cross member is of box section, and the stub axles are of a section that cannot be rotated when inserted into the hollow cross member.
6 A trailer as claimed in claim 4 or 5, in which the chassis and the second set of wheels include an inter-engaging retaining mechanism to prevent removal of the stub axles from the hollow cross member.
7 A trailer as claimed in any preceding claim, further including a braking system having a first part that is permanently attached to the chassis and a second part that is permanently attached to the second set of wheels and releasably connected to the first part.

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8 A trailer as claimed in any preceding claim, further including an operable support system which, when operated, supports the chassis such that at least one of the second set of wheels is clear of the ground.
9 A trailer as claimed in claim 8, in which the support system includes a jack.
10 A trailer as claimed in claim 8 or 9, in which the support system is permanently attached to the chassis.
11 A trailer as claimed in any preceding claim, in which the second set of wheels are road wheels suitable for supporting the trailer when towed behind a towing vehicle.
12 A trailer as claimed in any preceding claim, in which the first set of wheel are suitable for immersion in water and the second set of wheels are unsuitable for immersion in water.
13 A trailer as claimed in any preceding claim, in which the chassis includes a support arrangement for carrying a boat.
14 A trailer which is substantially as described in relation to the accompanying drawings.