WO2021185923A2

WO2021185923A2 - A lifting device

Info

Publication number: WO2021185923A2
Application number: PCT/EP2021/056853
Authority: WO
Inventors: Nicholas FRIENDLAY; Robert Nagy
Original assignee: Spinlock Lifting Equipment Ltd
Priority date: 2020-03-17
Filing date: 2021-03-17
Publication date: 2021-09-23
Also published as: WO2021185923A3

Abstract

A lifting device, comprising: a load bearing surface; a movement mechanism comprising a hydraulic or pneumatic cylinder assembly for moving the load bearing surface, the cylinder assembly including a cylinder body containing a rod configured to extend from the cylinder body thereby to raise the load bearing surface; and a locking mechanism for restricting movement of the movement mechanism, wherein the locking mechanism comprises: an externally-threaded inner sleeve, an internally- threaded locking ring, and an outer sleeve coupled with the rod of the movement mechanism.

Description

A LIFTING DEVICE

FIELD OF THE INVENTION

The present invention relates to a lifting device. More specifically, the invention relates to a lifting device, such as a trolley jack or bottle jack, with a failsafe mechanism.

BACKGROUND OF THE INVENTION

Lifting devices, commonly known as “jacks” are often used in commercial and domestic workshops to lift vehicles, and other heavy loads. Such lifting devices are often configured as either bottle jacks or trolley jacks depending on the required usage, the construction and operation of both being well known. Both configurations typically use either a hydraulic or pneumatic “cylinder assembly” as an actuator to lift the loads, said cylinder assembly comprising a cylinder body and piston rod arranged to move within the cylinder body under hydraulic or pneumatic pressure. However, standard jacks, e.g. hydraulic trolley jacks of the type typically used in commercial and domestic workshops, have no integral failsafe mechanism to prevent catastrophic retraction of the lifting arm in the event of a sudden hydraulic pressure loss.

And while previous commercial solutions have been brought to market, there are a number of functional drawbacks limiting their user-appeal. For a variety of reasons (e.g. tedium, lack of time or lack of equipment) users of such (e.g. trolley) jacks sometimes fail to heed safety recommendations and omit to use a dedicated mechanical support such as an axle-stand when jacking, leaving them dependent on a single hydraulic seal to support the weight of the vehicle.

This results in dozens of fatalities and thousands of serious injuries every year. Statistics show that while 80% of hospitalisations occur as a consequence of vehicles coming off jacks - 20% are attributable to hydraulic or mechanical failure of the jack itself.

The present invention provides an integral failsafe mechanism that protects the user (and vehicle) in the event of a sudden hydraulic pressure loss.

SUMMARY OF THE INVENTION

Described herein is a lifting device, comprising: a load bearing surface; a movement mechanism comprising a (e.g. hydraulic or pneumatic) cylinder assembly for moving the load bearing surface, the cylinder assembly including a cylinder body containing a rod configured to extend from the cylinder body thereby to raise the load bearing surface; and a locking mechanism for restricting movement of the movement mechanism; wherein the locking mechanism comprises an externally-threaded inner sleeve, an internally-threaded locking ring, and an outer sleeve coupled with the rod of the movement mechanism.

By providing such a lifting device with said locking mechanism, in the event of a sudden pressure loss in the cylinder body, for example, the locking mechanism will inhibit the rod from retracting back into the cylinder body, thereby helping to prevent injury to the user and/or damage to a load being lifted.

A skilled person will of course understand that the cylinder assembly operates under pressure (i.e. it is part of a pressurised system, which may comprises a pump, reservoir, etc., to increase and decrease pressure within the cylinder body), such that the rod is extended due to an increase in pressure within the cylinder body, and is able to retract when there is a decrease in pressure within the cylinder body.

The inner sleeve may be arranged to surround the cylinder body such that relative movement is limited therebetween, and the locking ring is threadedly engaged with the inner sleeve, such that the locking ring can be rotated relative to the inner sleeve to bring it into contact with the outer sleeve thereby to inhibit retraction of the rod of the cylinder assembly into the cylinder body. The outer sleeve may be coupled to the rod of the cylinder assembly via a connecting- pin that passes through both the rod and the outer sleeve.

The lifting device may be a “bottle” jack.

The load bearing surface may be spaced at least 10mm from the outer sleeve, preferably wherein the load bearing surface projects (or extends) at least 10mm further from (e.g. above, in use) the cylinder assembly than the outer sleeve. This spacing prevents contact of a load being lifted with the outer sleeve. The lifting device may comprise a spacer located between the load bearing surface and the outer sleeve, wherein the spacer has a length of at least 10mm. Preferably, the spacer is located between the load bearing surface and the connecting pin. The spacer may comprise a hollow cylindrical member arranged to receive the rod of the cylinder assembly therethrough.

The lifting device may comprise an extension member that is threadedly engaged with the rod of the cylinder assembly, wherein the extension member is also coupled to the outer sleeve, such that rotation of the outer sleeve causes the extension member to rotate relative to the rod and thereby change a spacing between the load bearing surface and the cylinder body. A load being lifted may thereby be raised a further distance than a conventional lifting device may permit, even when the rod is fully extended from the cylinder, thereby providing a larger maximum lifting height of the lifting device.

The lifting device may be a trolley jack having a lifting arm.

The rod of the cylinder assembly may be directly connected to the lifting arm of the trolley jack. In this arrangement, the cylinder may be pivotally attached to a chassis. By providing a lifting device with a pivoting cylinder where the rod is directly connected to the lifting arm, a simplified mechanism suitable for lifting loads up to about 2 tonnes may thereby be provided. The inner sleeve and/or a chassis in which the cylinder assembly is located, may be elongated to allow a user suitable access to rotate the locking ring.

Alternatively, the lifting device may comprise a link arm, wherein the rod of the cylinder assembly is indirectly connected to the lifting arm of the trolley jack by the link arm. By coupling the rod to the lifting arm using a link arm, the cylinder may be rigidly fixed to the chassis, and a stronger lifting device capable of lifting heavier loads may thereby be provided.

The lifting arm may be a skeletal lifting arm arranged to provide an opening through which the locking mechanism can be accessed. By using a skeletal lifting arm, the user is able to access and rotate the locking ring by reaching through the lifting arm.

The inner sleeve may comprise an end-plate with an opening through which the rod extends. The end-plate can help maintain alignment of the rod with the cylinder. The end plate may comprise a ring of material configured to inhibit scratch damage to the rod at the circumference of the opening. The lifting device may comprise a motor configured to drive rotation of the locking ring along the inner sleeve. The locking system may thereby be remotely operated.

The motor may be a torque sensing motor. Such a motor will automatically stop screwing the locking ring along the inner sleeve when the torque resistance experienced by the locking ring exceeds a setpoint threshold. The motor may be remotely operated to change its direction of rotation. By changing the direction of rotation of the motor, the locking ring can automatically be moved in the opposite direction along the locking sleeve, allowing the locking mechanism to be deactivated using the motor.

The motor may be coupled to the locking ring via a drive cylinder, wherein rotation of the drive cylinder causes movement of the locking ring along the inner sleeve. The drive cylinder may surround the inner sleeve, coaxially, and has internal splines which mesh with external splines on the locking ring, whereby rotation of the drive cylinder leads to rotation of the locking ring, and subsequent movement of the locking ring along the inner sleeve.

According to a specific example, there may be provided a lifting device comprising: - a) - a load bearing surface b) - a movement mechanism consisting of a hydraulic or pneumatic cylinder for moving the load bearing surface c) - a locking mechanism for restricting movement of the movement mechanism, the locking mechanism comprising an externally-threaded inner sleeve, an internally-threaded locking ring and an outer sleeve coupled with the hydraulic rod of the movement mechanism in some fashion.

Also described herein is a method of lifting a load using a lifting device according to any preceding claim, comprising: arranging the lifting device underneath a load to be lifted such that the load bearing surface engages with the load; lifting the load to a desired height using the movement mechanism; and engaging the locking mechanism once the desired height of the load has been reached, so as to inhibit retraction of the rod of the cylinder assembly back into the cylinder body.

Retraction of the rod of the cylinder assembly back into the cylinder body can thereby be inhibited until such time as retraction of the rod is desired, thereby to help prevent injury in the event that the cylinder body should lose pressure, in use.

As used herein, the term “cylinder assembly” preferably connotes an arrangement of a hydraulic or pneumatic cylinder comprising a hydraulic rod or a pneumatic rod (“rod”) moveable under pressure within a hydraulic cylinder or a pneumatic cylinder (“cylinder body”) respectively. The operation and construction of such cylinder assemblies and their components is well-known, and therefore need not be described in detail herein. As used herein, the term “movement mechanism” preferably comprises a cylinder assembly as described above. In some embodiments, the movement mechanism may be considered to consist of said cylinder assembly or its components (e.g. the “cylinder” and “rod”). As used herein, the term “extendable rod” preferably means the above described rod being configured to extend from and retract back into the cylinder body, be it in under hydraulic or pneumatic pressure.

As used herein, the term “threadedly engaged” preferably means to engage via screw threads, such that relative rotation of two components that are “threadedly engaged” will cause relative movement between those components. For example, a nut and a bolt having inner and outer screw threads, respectively, may be considered to be “threadedly engaged” when the nut is screwed onto the bolt.

It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present invention and without diminishing its attendant advantages.

BRIEF DESCRIPTION OF THE DRAWINGS

Example embodiments of the present invention will now be described with reference to the accompanying figures, in which: Figure 1 shows a side view of an embodiment of a lifting device in which the lifting device is a locking bottle jack;

Figure 2 shows a side view of an embodiment of a lifting device n which the lifting device is a locking bottle jack with an adjustable hydraulic rod extension;

Figure 3A shows a side view of an embodiment of a lifting device in which the lifting device is a locking trolley jack with a skeletal lifting-arm; Figure 3B shows a view of the locking mechanism of the locking trolley jack of Figure 3 A;

Figure 3C shows a view of an embodiment of the trolley jack of Figure 3A with a locking cylinder that has a blind sleeve; Figure 4 shows a side view of an embodiment of a lifting device in which the lifting device is a locking trolley jack with a solid lifting-arm in which the sleeved locking mechanism sits within the lifting arm;

Figure 5A shows a side view of an embodiment of a lifting device in which the lifting device is a locking trolley jack with a solid lifting-arm in which the sleeved locking mechanism sits behind the lifting arm rather than within it;

Figure 5B shows a view of the trolley jack of Figure 5A having a chassis with slotted sidewalls;

Figure 5C shows a top view of a wheeled hydraulic rod connecting-pin of the locking trolley jack of Figure 5A; Figure 6A shows a view of a pivoting cylinder body in a conventional trolley jack;

Figure 6B shows a side view of an embodiment of a lifting device in which the lifting device is a locking trolley jack with a pivoting locking mechanism

Figure 7 shows a cut-away side view of an embodiment of a lifting device in which the lifting device has an automatically-actuated, motorized locking cylinder (with its outer sleeve removed for clarity).

DETAILED DESCRIPTION

In the following description and accompanying drawings, corresponding features may preferably be identified using corresponding reference numerals to avoid the need to describe said common features in detail for each and every embodiment. The present invention may be implemented in at least two main configurations, each with a number of embodiments for a mechanically-locking hydraulic or pneumatic cylinder - as well as a motorized configuration applicable to all embodiments.

1 ) - A mechanically locking hydraulic or pneumatic bottle jack.

2) - A mechanically locking hydraulic or pneumatic trolley jack.

3) - An automatically-actuated, motorized configuration of both (1) and (2).

All the configurations are applicable to both hydraulic and pneumatic cylinders. Thus, as used herein the term “cylinder” may refer to a hydraulic or pneumatic cylinder (or “cylinder body”).

Unless otherwise stated, all mechanical components may be fabricated from ferrous, engineering-grade metals such as stainless steel - or non-ferrous, engineering-grade metals such as alloyed aluminium, for example.

Locking bottle jack

Figure 1 shows a lifting device according to the invention, in the form of a locking bottle jack 100. With particular reference to Figure 1 : This design is based on a conventional hydraulic bottle jack, though it will be appreciated that the design could alternatively be based on a conventional pneumatic bottle jack.

The bottle jack 100 has a load bearing surface in the form of a saddle 124 arranged to provide an interface between the bottle jack 100 and a load being lifted. The bottle jack 100 has a movement mechanism (i.e. for moving the saddle 124) in the form of a conventional cylinder assembly that has a cylinder 112 coupled to a jack handle (not shown), where pumping of the jack handle drives a rod 116 to extend from the cylinder 112. There is also a pressure release valve (not shown) which, when opened, releases pressure from the cylinder 112 and allows the rod 116 to retract into the cylinder 112. The cylinder 112 is mounted onto a base-plate 114 that rests on the ground during use of the bottle jack 100. A locking mechanism for the bottle jack 100 will now be described. A tight-fitting, externally-threaded sleeve 110 is secured around the body of the cylinder 112 (for instance with a thin cylindrical collar fitted between the sleeve 110 and the cylinder 112 at each end). The sleeve 110 may also be referred to herein as the “inner” sleeve 110. A locking ring 118 is threaded onto the inner sleeve 110 and spun to the end of the thread of the inner sleeve 10, so that it abuts the base-plate 114 of the cylinder 112. The locking ring 118 is internally threaded so as to engage with the inner sleeve 110. A knurl (not shown) may be machined onto the external surface of the locking ring 118 to allow it to be easily gripped and rotated by an operator. An unthreaded “outer” sleeve 120 is slid over the inner sleeve 110 that extends from the locking ring 118 to a point say (e.g. about) 10mm beyond the end of the cylinder's 112 retracted rod 116 (e.g. for a cylinder assembly with an unextended length of approximately 250mm). There should be sufficient clearance (e.g. circa 1 mm) between the inner sleeve 110 and the outer sleeve 120 to allow easy movement of one over, or past, the other. The movement of the rod 116 is transmitted to the outer sleeve 120 by coupling them both to a connecting-pin 122, which is preferably cylindrical.

It will be desirable for the saddle 124 (rather than the top of the outer sleeve 120) to contact the supported load. The saddle 124 should therefore sit at least 10mm higher than the top of the outer sleeve 120 (e.g. in a jack 100 with an unextended height of approximately 250mm). This can be effected by fitting a tubular spacer 126 between the connecting-pin 122 and the saddle 124.

Locking bottle jack - with adjustable hydraulic rod extension

Figure 2 shows a lifting device according to the invention, in the form of a locking bottle jack 200 that has the same construction to the bottle jack 100 shown in Figure 1 , but with a modification in the form of an adjustable rod extension 217 (equivalently referred to as an “extension member”). The rod extension 217 has an external thread that is configured to engage with the internal thread of the rod 216 of the cylinder assembly.

With particular reference to Figure 2: In bottle jacks with an adjustable rod extension 217 the connecting-pin 222 is secured to the spacer 226 by cutting a threaded hole across the diameter of the connecting-pin 222, screwing it up the thread of the rod extension 217 and tightening the connecting-pin 222 against the spacer 226, thereby locking them in place against the underside of the saddle 224.

This allows the operator to screw the rod extension 217 in or out of the rod 216 by rotating the outer sleeve 220, which increases the height to which the locking bottle jack 200 can raise a load.

Operation

During use of the locking bottle jack 100, an operator pumps the jack handle to raise the rod 112 - and when a supported load reaches a desired working height, the operator rotates the locking ring 118 along the thread of the inner sleeve 110 and tightens it against the end of the outer sleeve 120.

In this way, the rod 116 is prevented from retracting back into the cylinder 112 and thus locks a supported load in place.

Locking inner sleeve 110 and outer sleeve 120 together in this way effectively creates a single sleeve, through which the weight of a supported load is transferred to the base-plate 114 of the jack 100. To lower a supported load, rotate the locking ring 118 back along the inner sleeve 110, so that the rod 116 can retract unimpeded back into the cylinder 112 when the pressure-release valve is opened.

The locking bottle jack 200 is operated in an identical way, expect that the saddle 224 can be further raised by rotating the outer sleeve 220 as previously described.

Locking Trolley Jack

Figures 3A and 3B depict a locking trolley jack 300.

Locking trolley jack with a skeletal lifting-arm

Figure 3A shows a lifting device according to the present invention in the form of a locking trolley jack 300. Figure 3B depicts a close up of a locking mechanism for the trolley jack 300, which is similar to the locking mechanism of the locking bottle jacks 100, 200 described above in reference to Figures 1 and 2, respectively.

With particular reference to Figure 3A: The following design of the present invention is based on a conventional hydraulic or pneumatic trolley jack - e.g. of the type with a skeletal lifting-arm. The trolley jack 300 has a load bearing surface (not shown) mounted to a lifting arm 328, and arranged to provide an interface between the trolley jack 300 and a load being lifted.

The trolley jack 300 has a movement mechanism (i.e. for moving the lifting arm 328, and thus the load bearing surface) in the form of a conventional cylinder assembly. The cylinder assembly comprises a cylinder 312 attached to a pump body 315, which is housed within a chassis 330 of the trolley jack 300 having two side walls 330a (330b not shown). When a jack handle 326 is pumped by the operator, a rod 316 extends from the cylinder 312, thereby moving the lifting arm 328, and thus the load bearing surface mounted thereto.

With particular reference to Figure 3B, the locking mechanism for the trolley jack 300 will now be described. Similar to the locking mechanism of Figure 1 , a tight-fitting, externally-threaded sleeve 310 is secured over the body of the cylinder 312 (e.g. for instance with a thin cylindrical collar fitted between the externally-threaded sleeve 310 and the cylinder 312 at each end). The sleeve 310 may also be referred to herein as the “inner” sleeve 310. A locking ring 318 is threaded onto the inner sleeve 310 and spun to the end of the thread of the inner sleeve 310, so that it abuts the pump-body 315 at the base of the cylinder 312. The locking ring 318 is internally threaded so as to engage with the inner sleeve 310. A knurl (not shown) may be machined onto the external surface of the locking ring 318 to allow it to be easily gripped and rotated by an operator. An unthreaded “outer” sleeve 320 is slid over the inner sleeve 310 that extends from the locking ring 318 to a point say (e.g. about) 10mm beyond the end of the cylinder's 312 retracted rod 316 (e.g. for a cylinder assembly with an unextended length of approximately 250mm). There should be sufficient clearance (about 1 mm) between the inner sleeve 310 and the outer sleeve 320 to allow easy movement of one over, or past, the other. The movement of the rod 316 is transmitted to the outer sleeve 320 by coupling them both to a connecting-pin 322, which is preferably cylindrical.

A link arm 323 (equivalently referred to as a linkage) couples the connecting pin 322 to a first lifting arm pivot 325 on the lifting arm 328. The lifting arm 328 is pivotally connected to the side walls 330a, 330b of the chassis 330, such that the lifting arm 328 can pivot, or rotate, about the second lifting arm pivot 329 when the rod 316 extends from the cylinder 312. Ideally, unless otherwise stated, the pivots 325, 329 are provided with pivot-pins passing through holes in the two components which are pivotally connected together. In this embodiment, the lifting arm 328 is “skeletal”. Unlike a “solid” lifting arm, a skeletal lifting arm 328 lacks a horizontal top plate along its middle section, which allows the user access to the locking ring 318 beneath. Operation

During use of the locking trolley jack 300, an operator pumps the jack handle 326 to raise the lifting arm 328 - and when a supported load reaches a desired working height, the operator rotates the locking ring 318 along the thread of the inner sleeve 310 and tightens it against the end of the outer sleeve 320. In this way, the rod 316 is prevented from retracting back into the cylinder 312 and thus, any downward movement of the lifting arm 328 is prevented - locking the supported load in place.

Locking inner sleeve 310 and outer sleeve 320 together in this way effectively creates a single sleeve, through which the weight of a supported load is transferred via the lifting arm 328 to the base of the cylinder assembly (in this case, the jack pump- body 315).

To lower the supported load, the operator reaches through the skeletal lifting-arm 328 - and rotates the locking ring 318 back along the inner sleeve 310, so that the rod 316 can retract back into the cylinder 312 unimpeded when a pressure-release valve (not shown) is opened.

Locking trolley jack with a skeletal lifting-arm and blind sleeve

Figure 3C depicts a variation of a locking mechanism for the trolley jack 300, which has a blind sleeve. This variation is similar to the locking mechanism described in relation to Figure 3B. With particular reference to Figure 3C: the rod 316 in this configuration is longer than in the standard jack on which it is based - and it may be that additional vertical and lateral support to maintain alignment of the rod 316 within the cylinder 312 is desirable.

This additional support is provided by making the inner sleeve 310 “blind” rather than leaving it as an open-ended cylinder - and machining a hole in a sleeve end-plate 311 (e.g. that is attached to the end of the inner sleeve 310 closer to the rod 316) to accommodate and support the rod 316... with a ring of protective material around the circumference of the hole to protect the rod 316 from scratching. The hole in the sleeve end-plate 311 may alternatively be referred to herein as an opening.

Locking trolley jack with a solid lifting-arm

The term “solid lifting-arm” is used herein to denote that the lifting-arm has a top- cover preventing access through it - not that it has a bottom cover.

In this embodiment, the lifting arm 428 of the jack 400 is “solid” rather than “skeletal” (i.e. the trolley jack 400 does not have a lifting arm aperture through which an operator can access the locking ring 418. With particular reference again to Figure 4: In trolley jacks without a lifting-arm aperture, the user (i.e. operator) cannot access the locking ring 418 through the arm - and must do so in the space between the rear of the arm 428 and the pump-handle 426 (in other words, the region between the lifting arm pivot pin 429 and the pump-handle 426). That region may herein be referred to as the region “behind” the lifting arm 428.

This requires elongation of the inner sleeve 410 and the sidewalls 430a, (430b not shown) of the chassis 430 within that space, in order to allow the user access to the locking ring 418 along the full length of its travel - from lowest to highest locking elevation along the inner sleeve 410. Construction of the locking mechanism is otherwise identical to that in the skeletal lifting-arm configuration.

Operation

Operation of the jack 400 is the same as it is in the skeletal lifting-arm configuration - but the locking ring 418 must be accessed behind the lifting-arm 428 rather than through it.

Locking trolley jack with a solid lifting-arm and wheeled rod connecting-pin

Figure 5A depicts a locking trolley jack 500 with a solid lifting-arm 528 and a wheeled rod connecting pin 531. With particular reference to Figure 5A: The rod 516 in this configuration is longer than the rod in the standard jack on which it is based - and it may be that additional vertical and lateral support to maintain alignment of the rod 516 within the cylinder 512 is desirable.

This additional support would be provided by lengthening the frontmost rod connecting-pin 531 , so that each end passes through a slot machined in the chassis sidewalls 530a, 530b- and (as depicted in Figure 5C) attaching a grooved wheel 534a, 534b that runs within the slots 532a, 532b to each end of the connecting- pin 531 - providing easy fore-aft movement of the connecting-pin 531 while constraining vertical and lateral movement of the rod 516, thereby maintaining the rod's 516 alignment within the cylinder 512. In other words, a second connecting-pin 531 may be connected to the end of the lengthened rod 516. Figure 5B shows a lifting jack 500 with a slots 532a, 532b in each of the side walls 530a, 530b of the chassis 530. This configuration can be used as an alternative or in addition to the blind inner sleeve 310 described in relation to Figure 3C. Locking trolley jack with a solid arm and pivoting cylinder

Figure 6A shows a view of the pivoting cylinder 612 with a pivot 634 in a conventional trolley jack. The thickness of the cylinder cup wall 640 may be increased to provide a broad shoulder for inner sleeve (610 not shown) to bear against.

Figure 6B depicts another variation of a trolley jack 600, which uses a pivoting cylinder. Pivoting cylinders are generally used in light-duty trolley jacks with a typical maximum weight-rating of 2-tons. This constraint is imposed by the tall, narrow aspect ratio of the lifting-arm 628.

In this embodiment, the cylinder 612 has a pivot 634 which allows it to pivot relative to the chassis (not shown) when the jack handle (not shown) is pumped to extend the rod 616. The end of the rod 616 is pivotally attached directly to the first lifting arm pivot 625 of the lifting arm 628 with a second connecting-pin 631 , so that extension of the rod 616 from the cylinder 612 raises a load bearing surface (not shown) on the lifting arm 628, as the lifting arm 628 pivots about its second lifting arm pivot 629.

In order for an operator to access the locking ring 618, and with particular reference to Figure 6: the locking mechanism must therefore sit behind the lifting arm 628 rather than within it - and requires elongation of the jack chassis between the pivot-pin 629 of the lifting-arm 628 and the pump body 615.

Construction of the locking mechanism is otherwise identical to that in the skeletal lifting-arm configuration, e.g. as described with reference to Figures 3A-3C.

Operation

Operation of the trolley jack 600 is the same as it is in the solid lifting-arm configuration - wherein the locking ring 618 is accessed behind the lifting-arm 628.

Locking cylinder with an automatically-actuated, motorized locking ring

Certain applications may require remote operation of the cylinder lock (or “locking mechanism”) - and for this, a torque-sensing electric motor 744, drive gear 742 and drive cylinder 740 can be used to actuate the locking ring 718 automatically in the absence of a human operator.

Figure 7 depicts an automatically actuated locking mechanism 700 that could be used in one of the locking bottle jacks 100, 200 or one or the locking trolley jacks 300-600 previously described. With particular reference to Figure 7: Take the locking bottle jack or trolley jack and replace its manual hydraulic or pneumatic pump with an electrically powered (or actuated) one. Replace its manual pressure-release valve with an electrically-actuated one.

The automatically actuated jack has a locking mechanism 700 similar to those already described, except for the following difference: instead of machining a knurl round the outer circumference of the locking ring 718, a gear-spline is machined instead. Next, a drive cylinder 740 that rotates the locking ring 718 up and down the threads of the inner sleeve 710 can be made.

For this, for example, take a cylindrical sleeve of approximately 5mm wall-thickness (in a jack with an unextended height of approximately 250mm) and machine splines down the length of its inner circumference - to mesh with and encapsulate the locking ring 718, in use. In other words, the drive cylinder coaxially surrounds the inner sleeve. The outer sleeve (720 not shown) is configured to fit between the drive cylinder 740 and the inner sleeve 710 so that it can contact the locking ring 718 during use of the lifting jack. Now machine a gear-spline 741 (say, e.g. about, 20mm long) on the outer circumference of the drive cylinder 740, near the midpoint of its length. This gear- spline 741 will mesh with a splined (e.g. drive) gear 742 of an electric motor 744 mounted on the jack's base-plate (not shown). Thus, the motor 744 rotates its splined (e.g. drive) gear 742 - which rotates the drive cylinder 740- which rotates the locking ring 718 up and down the threads of the inner sleeve 710.

An electronic module (not shown) may be used to control power to the pump, pressure-release valve and electric motor 744, and also to create a torque setpoint at which the controller cuts or delivers power to the drive motor 744.

Next, to allow the drive cylinder 740 to freely rotate, attach a thrust bearing 746 of the same diameter as the drive cylinder 740 , to the base-plate of the jack (for instance, with spot-welds) - which will allow the drive cylinder 740 to rotate freely on the base plate. For mobile applications, the electrical power requirements are supplied by a battery pack (not shown) of an appropriate rating.

Operation To raise the supported load (i.e. to operate the jack), a pump is switched on (e.g. by an operator) - whence the control module closes the pressure-release valve ... causing the rod 716 to egress from the cylinder 712, drawing the outer sleeve (720 not shown) with it.

As the outer sleeve 720 moves away from the locking ring 718, friction between them disappears - causing torque resistance felt at the motor 744 to fall below its setpoint threshold - at which point the controller delivers power to the motor 744 which rotates the locking ring 718 up the thread of the inner sleeve 710. When the supported load reaches the desired height, the controller cuts power to the pump and the rod 716 stops moving. And as the locking ring 718 rotates up to (e.g. and contacts) the end of the outer sleeve 720, torsional resistance felt at the motor 744 rises above its setpoint threshold - and the controller cuts power to the motor 744.

The abutment of the locking ring 718 against the outer sleeve 720 prevents the rod 716 from retracting into the cylinder 712 - thereby locking the supported load in place.

In order to lower the supported load, the controller is programmed to power the electric motor 744 in the opposite direction when the pressure-release valve is open. The controller commences lowering by closing the pressure-release valve and momentarily powering the pump to raise the rod 716 by approximately 1 mm, in order to separate the locking ring 718 from the outer sleeve 720.

This causes torsional resistance felt at the motor 744 to fall below its setpoint threshold, whence the controller delivers power to the motor 744 to rotate the locking ring 718 back down the thread of the inner sleeve 710.

The controller then opens the pressure-release valve - and with the locking ring 718 rotating back down the thread of the inner sleeve 710, the rod 716 is free to retract unimpeded into the cylinder 712- and the supported load is lowered. When the locking ring 718 abuts the base plate 714, torsional resistance felt at the motor 744 rises above its setpoint threshold, and the controller cuts power to the motor 744. It will be appreciated that any feature of a particular embodiment described herein may be applied to another embodiment, in any appropriate combination. It will also be appreciated that particular combinations of the various features described and defined in any aspects described herein can be implemented and/or supplied and/or used independently. Any apparatus feature described herein may also be incorporated as a method feature, and vice versa.

While the foregoing is directed to exemplary embodiments of the present invention, it will be understood that the present invention is described herein purely by way of example, and modifications of detail can be made within the scope of the invention. Indeed, other and further embodiments of the invention will be apparent to those skilled in the art from consideration of the specification, and may be devised without departing from the basic scope thereof, which is determined by the claims that follow.

Claims

1 . A lifting device, comprising: a load bearing surface; a movement mechanism comprising a hydraulic or pneumatic cylinder assembly for moving the load bearing surface, the cylinder assembly including a cylinder body containing a rod configured to extend from the cylinder body thereby to raise the load bearing surface; and a locking mechanism for restricting movement of the movement mechanism, wherein the locking mechanism comprises: an externally-threaded inner sleeve, an internally-threaded locking ring, and an outer sleeve coupled with the rod of the movement mechanism.

2. The lifting device of claim 1 , wherein the inner sleeve is arranged to surround the cylinder body such that relative movement is limited therebetween, and the locking ring is threadedly engaged with the inner sleeve, such that the locking ring can be rotated relative to the inner sleeve to bring it into contact with the outer sleeve thereby to inhibit retraction of the rod of the cylinder assembly into the cylinder body.

3. The lifting device of claims 1 or 2, wherein the outer sleeve is coupled to the rod of the cylinder assembly via a connecting-pin that passes through both the rod and the outer sleeve.

4. The lifting device of any of claims 1 to 3, wherein the lifting device is a bottle jack.

5. The lifting device of claim 4, wherein the load bearing surface is spaced at least 10mm from the outer sleeve, and preferably wherein the load bearing surface projects at least 10mm further from the cylinder assembly than the outer sleeve.

6. The lifting device of claim 4 or 5, further comprising a spacer located between the load bearing surface and the outer sleeve, preferably wherein the spacer is located between the load bearing surface and the connecting pin, wherein the spacer has a length of at least 10mm.

7. The lifting device of claim 6, wherein the spacer comprises a hollow cylindrical member arranged to receive the rod therethrough.

8. The lifting device of any preceding claim, further comprising an extension member that is threadedly engaged with the rod of the cylinder assembly, wherein the extension member is also coupled to the outer sleeve, such that rotation of the outer sleeve causes the extension member to rotate relative to the rod and thereby change a spacing between the load bearing surface and the cylinder body.

9. The lifting device of any of claims 1 to 3, wherein the lifting device is a trolley jack having a lifting arm.

10. The lifting device of claim 9, wherein the rod of the cylinder assembly is directly connected to the lifting arm of the trolley jack.

11. The lifting device of claims 9 or 10, wherein the inner sleeve and/or a chassis in which the cylinder assembly is located, is elongated to allow a user the required access to rotate the locking ring.

12. The lifting device of claim 9, further comprising a link arm, wherein the rod of the cylinder assembly is indirectly connected to the lifting arm of the trolley jack by the link arm.

13. The lifting device of claim 12, wherein the lifting arm is a skeletal lifting arm arranged to provide an opening through which the locking mechanism can be accessed.

14. The lifting device of claims 9 to 13, wherein the inner sleeve further comprises an end-plate with an opening through which the rod extends.

15. The lifting device of claim 14, wherein the end plate further comprises a ring of material configured to inhibit scratch damage to the rod at the circumference of the opening.

16. The lifting device of any preceding claim, further comprising a motor configured to drive rotation of the locking ring along the inner sleeve.

17. The lifting device of claim 16, wherein the motor is a torque sensing motor.

18. The lifting device of claims 16 or 17, wherein the motor is coupled to the locking ring via a drive cylinder, wherein rotation of the drive cylinder causes movement of the locking ring along the inner sleeve.

19. The lifting device of claim 18, wherein the drive cylinder surrounds the inner sleeve, coaxially, and has internal splines which mesh with external splines on the locking ring, whereby rotation of the drive cylinder leads to rotation of the locking ring, and subsequent movement of the locking ring along the inner sleeve.

20. A method of lifting a load using a lifting device according to any preceding claim, comprising: arranging the lifting device underneath a load to be lifted such that the load bearing surface engages with the load; lifting the load to a desired height using the movement mechanism; and engaging the locking mechanism once the desired height of the load has been reached, so as to inhibit retraction of the rod of the cylinder assembly back into the cylinder body.