GB2106459A - Chassis for mobile lifting mechanisms - Google Patents

Abstract

A mobile boat lift 10 comprises a chassis 12 having two trailing main arms 34 each supported at its rear end by a wheel 46 and pivotally connected at its leading end to a link arm 24 which is in turn pivoted to a draw bar 15. A beam 48 is mounted above each arm on a forward strut 52 and a rear strut and is raisable by a hydraulic ram 56. A boat may be slung between the arms 34 by straps suspended between hooks 50. With lockings 26, 38 removed, forward movement of the lift 10 causes the arms to close together from the lifting position shown in Figure 3 to reduce the overall width of the chassis 12 for trailing on public roads. <IMAGE>

Description

SPECIFICATION Chassis for mobile lifting mechanisms This invention relates to chassis for mobile lifting mechanisms and particularly, but not exclusively, to trailer chassis for mounting mobile boat lifts.

If it is required that a lifting mechanism such as a boat lift, crane or loading platform may be taken on the public roads to move it from one location to another without making special arrangements, it must not exceed a certain width which in the United Kingdom is currently 8 feet 2 inches. This width is insufficient to endow the chassis with sufficient lateral stability if a load is being lifted outside the wheel base and imposes a severe restriction on the width of loads that can be accepted within a lifting framework having this external width. In the case of boats, lifts with an overall width of only 8' 2" will hardly permit the acceptance of a boat having a beam of 7 foot, which is a common maximum beam for canal craft dictated by the width of the locks on narrow waterways, let alone the small craft which are not subject to this restriction and have slightly wider beams.

According to the present invention the problem is overcome by mounting the lifting mechanism on a chassis in which the wheel or wheels on one side are arranged to be laterally displaceable with respect to the wheels on the other side between a retracted, transport position and an extended, lifting position. Preferably the wheels on each side of the chassis are both displaceable so as to preserve the symmetry of the chassis in both the retracted and extended positions.

The wheel or wheels on each side may be mounted on a member arranged for sliding or similar sideways movement but are preferably mounted on respective pivoted longitudinal members. In certain applications the members may be pivoted at each end but in cases such as boat lifts where the chassis has to be open at the rear so as to allow it to be manoeuvred around a boat, then the members are preferably pivoted only at their leading ends. If a short link arm is interposed between the pivoted end of each said member and the main chassis structure, then the members may be maintained parallel in both the retracted and extended positions.

The advantage of mounting the wheels on longitudinal pivoted members is that no additional means is required to effect the movement between the extended and retracted positions: forward movement of the chassis closes the members together towards the retracted position and rearward movement of the chassis forces them apart towards the extended position. If each member is supported by only one wheel then little resistance is presented to their lateral movement: if however, each member is supported on two or more longitudinally spaced wheels then provision must preferably be made to allow at least some of the wheels to pivot.

Any suitable elevatable sting- or cradle-carrying structure may be mounted on the chassis according to the present invention in order to form a mobile boat lift; in other applications the chassis may be used to impart improved laterial stability to a crane installed thereon or to provide a variable-width loading platform which may, for example, have a trellis structure so as to be laterally extensible to accommodate different chassis widths.

Although the invention may be carried out in a great variety of ways, one particular embodiment thereof will now be described, by way of example, with reference to the accompanying drawings in which Figure 1 is a side elevation of a mobile boat lift according to the invention with the chassis extended and the lifting frames partly lowered: Figure 2 is an elevation similar to that of Fig. 1, but with the frames raised; Figure 3 is a plan, with parts omitted, of the lift as shown in Fig. 2; Figure 4 is a plan of the lift of Figs. 1 to 3 with the chassis retracted; and, Figure 5 is an end elevation of the lift as shown in Fig. 2.

A mobile boat lift 10 as shown in Figs. 1 to 5 essentially comprises a chassis 1 2 and two identical lifting frames 1 4 mounted one on each side of the chassis.

The chassis 12 has a draw bar 1 5 to the front end of which is fitted a conventional towing attachment 1 6 and to the rear end a pivot housing 1 8 which has a hydraulically-adjustable support foot 20 extending from the base thereof. The housing 1 8 is apertured to receive two pivot pins 22 on each of which a trailing link arm 24 is mounted for pivotal movement between an extended position as shown in Figs. 1 to 3 and 5 and a retracted position as shown in Fig. 4.The arms 24 may each be locked in the extended position by passing a pin 26 through apertures 27 in the housing 18 and an aperture 28 in the arm 24, when all the apertures are in register; and in the retracted position by passing the pin 26 through apertures 30 in the housing and an aperture 32 in the arm 24, again when all the apertures are in register.

To the rear of each arm 24 is pivotally attached a trailing, laterally-displaceable main arm 34, each arm 34 having a pivot housing 36 at its forward end through which is fixed a pivot pin 37 passing through an aperture in the end of the arm 24. Each arm 24 is locked to the respective arm 34 in the extended position by passing locking pin 38 through apertures 40 in the housing 36 and an aperture in the arm 24 when the apertures are in register; and in the retracted position by passing the pin 36 through apertures 42 in the housing and the same aperture in the arm 24. At its rear end each arm 34 terminates in a casing 44 in which is mounted a wheel 46.

The lifting frames 14 each comprise a main beam 48 carrying a set of lifting strap hooks 50 and being hingedly mounted above the respective main arm 34 by a front leg 52 and a rear leg 54; simultaneous raising and lowering of the beams 48 is effected by a pair of hydraulic rams 56 connected between a respective one of the front legs 52 and of the main arms 34. Each frame 12 is lockable in the raised position by means of a tongue 58 projecting from near the foot of each leg 52 and securable between a pair of apertured lugs 60 by a pin 62.

In use, in a typical operation, the lift 10 is connected by means of the towing attachment 1 6 to the tow bar of suitable tractor having a hydraulic take-off to which the lift 10 is also connected. The chassis 12 is then towed, with the arms 24, 34 locked in the retracted position shown in Fig. 4 and the frames 14 lowered, along public roads to a slipway where a boat is to be taken out of the water. After removal of the locking pins 26, 38 the lift 10 is reversed towards the slipway causing the two sets of opposed arms 24, 34 to diverge outwardly. When the arms 24, 34 have reached their extended positions the pins 26, 38 are dropped through the registering apertures and the lift 10 then backed down the slipway until the two sets of opposed arms 24, 34 embrace the craft waiting to be lifted out of the water.When webbing straps (not shown) have been passed underneath the hull and their ends hooked onto the hooks 50, the hydraulic system of the tractor is operated, firstly to stabilse the chassis 1 2 by lowering the support foot 20 and, secondly, by actuating the rams 56 to raise the beams 48, and consequently the boat, which is cradled in the lifting straps.

Before the suspended boat is trailed to its destination within the yard the pins 62 are passed through the respective lugs 62 and tongues 60 as a safety measure and the foot 20 is raised. On arrival at the desired location the boat is gently lowered onto blocks, chocked up and the straps removed from the hooks 50. The lift 10 may then be towed clear of the boat and the frames 14 lowered; and then towed a further short distance after the locking pins 26 38 have been removed to allow the arms 24, 34, to close together. After replacing the pins to lock the arms in the retracted position the lift 10 may then be taken onto the public roads.

For lifting narrow beam craft it may be more convenient to use the lift 10 with the arms in the retracted position shown in Fig. 4.

Claims (14)

1. A chassis for mounting a mobile lifting mechanism and having at least one wheel which is arranged to be laterally displaceable with respect to the main chassis structure between a retracted, transport position and an extended, lifting position.

2. A chassis as claimed in Claim 1, in which one or more wheels on each side are arranged to be laterally displaceable.

3. A chassis as claimed in Claim 1 or 2, in which the one or more laterally-displaceable wheels on each side are mounted on a laterally displaceable member.

4. A chassis as claimed in Claim 3, in which the or each member is pivotally connected to the main chassis structure.

5. A chassis as claimed in Claim 4, in which the member is pivotally connected only at one end thereof.

6. A chassis as claimed in Claim 5, in which the member is pivotally connected at its leading end.

7. A chassis as claimed in Claim 5 or 6 and additionally comprising a link arm pivotally interconnecting said one end and the main chassis structure.

8. A chassis as claimed in Claim 3 or any one of Claims 4 to 7 and appendent thereto, in which the space between the laterally-displaceable member and the main chassis structure or the other laterally-displaceable member is unobstructed and accessible from the rear.

9. A chassis as claimed in any preceding Claim and so arranged that movement in one of the forward and reverse directions will cause the laterally-displaceable wheel or wheels to assume the transport position and movement in the other of said directions will cause the wheel or wheels to assume the lifting position.

10. A chassis as claimed in Claim 1 and substantially as herein described.

11. A chassis for mounting a mobile lifting mechanism, substantially as herein described with reference to the accompanying drawings.

12. A chassis as claimed in any preceding Claim and having a lifting mechanism mounted thereon.

13. A chassis as claimed in Claim 12, in which the lifting mechanism comprises two elevatable beams between which a boat may be slung.

14. The features as herein disclosed, or their equivalents, in any novel selection.