CA2714047C

CA2714047C - Vehicle lifting system, apparatus and method

Info

Publication number: CA2714047C
Application number: CA2714047A
Authority: CA
Inventors: Imran Habib Malik
Original assignee: Suncor Energy Inc
Current assignee: Suncor Energy Inc
Priority date: 2010-08-31
Filing date: 2010-08-31
Publication date: 2014-01-07
Anticipated expiration: 2030-08-31
Also published as: CA2714047A1

Abstract

Systems, apparatuses and methods relating to lifting a vehicle and providing a safety lock to prevent unintentional lowering thereof. One embodiment of the apparatus may comprise first and second lock assemblies capable of being remotely actuated to cause vertically movable lifting members to be locked with respect to associated support frames thus effectively converting the lifting apparatus into a fixed stand for supporting the vehicle.

Description

VEHICLE LIFTING SYSTEM, APPARATUS AND METHOD
BACKGROUND OF THE INVENTION
1. Field of Invention This invention relates generally to lifting systems, apparatuses, assemblies and methods, and in particular, to remotely-lockable lifting systems, apparatuses, assemblies and related methods for safely lifting heavy vehicles or equipment such as dozers.

2. Description of Related Art In many fields of mining, such as oil sands mining, mobile equipment units and vehicles are subject to considerable wear and tear as a result of continual operation in harsh conditions and in rugged terrain. In the case of a dozer (i.e., bulldozer) operating in such circumstances, it is important to constantly inspect and maintain the undercarriage of the dozer. A dozer typically has a relatively low clearance as well as a dozer blade at its front end and a ripper at its rear end, all of which tend to interfere with access to the undercarriage.
Consequently, a dozer is ordinarily raised off the ground to carry out maintenance work on the undercarriage. Once the dozer is raised to a sufficient height, mechanics can freely perform important tasks underneath such as replacing rollers, tracks or changing out side frames, for example.
One current method of lifting a dozer, sometimes referred to as powering down, involves a dozer operator lowering the dozer blade and ripper so as to push both against the ground, in effect, to cause the dozer to raise itself upwards. As the dozer is raised, mechanics crawl underneath the dozer to place heavy stands to support the front and rear ends of the dozer. This method has numerous disadvantages. Undesirably, by requiring mechanics to work in the vicinity of an active dozer while it is lifting itself, the method may create safety risks. For example, mechanics need to work in the confined space between the body of the dozer unit and its front blade while the unit is raised in the air. The dozer is constantly shaking when in motion, yet the mechanics must work in the blade hydraulics area to adjust the position of the stands. Not only is it difficult to place the stands accurately under such conditions, but there is a possibility that the blade cylinder or ripper cylinder hydraulics could fail or the ripper itself could break while the mechanic is under the dozer, thereby causing severe injury or even death. Moreover, this method requires extra time for communication between the mechanics and the dozer operator to correctly place the stands and set the dozer onto the stands. The stands may not be accurately placed in the first instance due to the inaccuracy of the mechanics' visual inspection of the stands' position in such a confined space. Moreover, mechanics may need to forcibly pry or pull the heavy stands which could lead to fatigue or even back injury occasionally.
A second method of lifting a dozer involves placing four separate hydraulic jacks under the dozer, each being placed independently of the others. The two jacks at the front of the dozer are connected to one pump cart, while the two jacks at the rear of the dozer are connected to a separate pump cart. The two separate pump carts are respectively operated by two mechanics, who independently regulate the flow of each pump cart so as to lift or lower the dozer evenly. This method has a number of disadvantages. Extra time is required to place four independent jacks into position. Two mechanics are required to lift the dozer. Moreover, it is difficult to lift or lower the dozer evenly as the two mechanics need to coordinate their respective adjustments of the hydraulic flow of the two pump carts to avoid one end of the dozer lifting or lowering faster than the other end. Once the dozer is lifted into position and mechanics begin to work on the undercarriage, for example, by removing heavy parts, the dozer may sway from side to side, as the four independent jacks act as concentrated point loads, leading to concerns about stability and safety. The possibility of jack failure also raises safety issues. A failure of even one of the hydraulic jacks while repairs are being carried out could

-3-potentially be catastrophic for any mechanics who happen to be under the dozer at that time. Although it is possible for mechanics to crawl under the dozer to mechanically secure the lifted portion of the jacks using locking collars before starting repairs, doing so exposes the mechanics to potential danger at least while the locking collars are being manually secured.
It would be desirable to provide a system, method or apparatuses that at least partially address these and other known problems in the field of the invention.
SUMMARY OF THE INVENTION
In accordance with one aspect of the invention, there is provided a vehicle lifting apparatus. The apparatus includes first and second hydraulic lift cylinders comprising respective first and second hydraulic lift cylinder shafts operably configured to extend along respective first and second lifting axes.
The first and second hydraulic lift cylinders each have a respective first and second end. The vehicle lifting apparatus includes first and second lifting members having respective first and second vehicle engaging ends for engaging corresponding first and second portions of the vehicle. The first and second lifting members are connected to the respective first ends of the first and second hydraulic lift cylinders, respectively. The vehicle lifting apparatus also includes first and second support frames connected to the respective second ends of the first and second hydraulic lift cylinders, respectively, and comprising respective first and second guide channels to guide telescoping movement of the first and second lifting members along the first and second lifting axes, respectively. The vehicle lifting apparatus further includes a first support frame connector fixedly connecting the first and second support frames in generally parallel, spaced apart relation such that the first and second lifting axes are generally parallel to each other. The apparatus further includes first and second lock assemblies, mounted on the first and second support frames, respectively, each lock assembly comprising at least one lock and at least one lock actuator that are powered and controlled remote from

-4-the lock assembly and operably configured to selectively cause the at least one lock to move between an unlocked position in which the associated lifting member can extend away from or retract towards the associated support frame, and a locked position in which the at least one lock interferes with retraction of the associated lifting member toward the associated support frame.
The first lock assembly may include a first pair of linear actuators mounted on opposite sides of the first support frame and a lock coupler coupling movement of the first pair of linear actuators to the at least one lock of the first lock assembly.
The at least one lock may include a pair of pins operably configured to be placed into the locked position by insertion into respective openings of the first support frame on opposite sides of the first hydraulic lift cylinder shaft in response to movement of the first pair of linear actuators in a first, locking direction.
The at least one lock actuator may include a linear actuator having an axis of movement perpendicular to the first and second lifting axes.
The lock actuators mounted on the first and second support frames may each have an axis of movement parallel to a longitudinal axis of the support frame connector.
The lock actuators mounted on the first and second support frames may each have an axis of movement that is disposed in a common single plane parallel to the longitudinal axis of the support frame connector.
The apparatus may include a lock coupler coupling the at least one lock actuator with the at least one lock.
The lock coupler may include a rod and the at least one lock may include at least one pin connected to or threaded onto the rod.
The first and second support frames may be spaced apart sufficiently and the first and second extendable lifting members may be extendable sufficiently to provide an undercarriage access opening to permit mechanic

-5-access to the undercarriage of the vehicle through the undercarriage access opening.
The apparatus may be configured in some embodiments as follows:
(a) the support frame connector, and first and second support frames, and the first and second lifting members may be dimensioned to provide an undercarriage access space sufficient to provide a mechanic with access to the vehicle undercarriage when the first and second lifting members are extended;
(b) in their locked position, the first and second lock assemblies may occupy an insubstantial amount of the undercarriage access space such that mechanic access to the undercarriage through the undercarriage access space is substantially unimpeded; and (c) when in their unlocked position, the first and second lock assemblies may occupy a substantial portion of the access space such that mechanic access to the undercarriage through the undercarriage access space is impeded.
The first and second lock assemblies may include respective first and second sensors operable to detect locking engagement of the first and second locks, respectively, for use in disabling the operation of the first and second hydraulic cylinders until the first and second locks are disengaged (e.g., to the unlocked position).
The respective lock actuators of the first and second lock assemblies may include respective first and second hydraulic lock cylinders.
The first locking assembly may include a first lock guide, mounted on the first support frame, for guiding the associated lock as it moves between the locked position and the unlocked position, wherein at least a portion of the associated lock may be disposed in the first lock guide.
The first and second hydraulic lift cylinders may be in hydraulic communication with respective load holding valves operably configured to

-6-prevent the first and second hydraulic lift cylinders from suddenly lowering in the case of hydraulic pressure loss.
Extension of the first and second hydraulic lift cylinder shafts may cause the first and second lifting members to extend away from the first and second support frames, respectively, and retraction of the first and second hydraulic lift cylinder shafts may cause the first and second lifting members to retract towards the first and second support frames, respectively; and the first and second support frames may be configured to facilitate sliding engagement with the first and second lifting members, respectively, during the extension and retraction thereof.
The support frame connector may include lifting receptacles to facilitate lifting of the vehicle lifting apparatus.
The apparatus may further include first and second wheel assemblies mounted on the first and second support frames, respectively, each of the first and second wheel assemblies having a spring-loaded suspension and at least one lockable wheel.
The apparatus may include a pump cart operable to pressurize first and second hydraulic fluid circuits in fluid communication with the first vehicle lifting assembly and a second vehicle lifting assembly, respectively, wherein the first and second vehicle lifting assemblies are configured for use in lifting the front and rear ends, respectively, of the vehicle, the pump cart including:
(a) first and second hydraulic fluid conduit pairs for powering the first and second hydraulic lift cylinders of the first vehicle lifting system, respectively;
(b) a third hydraulic fluid conduit pair for powering the first and second lock assemblies of the first vehicle lifting system, respectively;
(c) fourth and fifth hydraulic fluid conduit pairs for powering first and second hydraulic lift cylinders of the second vehicle lifting system, respectively; and

-7-(d) a sixth hydraulic fluid conduit pair for powering first and second hydraulic lock cylinders of the second vehicle lifting system, respectively.
In some embodiments, the apparatus may include a pump cart operable to pressurize hydraulic fluid circuits in fluid communication with the first vehicle lifting assembly and a second vehicle lifting assembly, the first and second vehicle lifting assemblies configured for use in lifting the front and rear ends, respectively, of the vehicle. The pump cart may include first and second hydraulic fluid conduit pairs for powering the first and second hydraulic lift cylinders of the first vehicle lifting system, respectively.
The pump cart may also include third and fourth hydraulic fluid conduit pairs for powering first and second hydraulic lift cylinders of the second vehicle lifting system, respectively and a fifth hydraulic fluid conduit pair for powering at least one hydraulic lock cylinder.
The pump cart may include six sets of hydraulic hose pairs operable to be connected to the respective hydraulic fluid conduit pairs.
The six sets of hydraulic hose pairs may be arranged into first and second manifold-type plugs, each comprising three sets of hydraulic hose pairs, corresponding to the first and second vehicle lifting systems, respectively.
The pump cart may include a four-piston hydraulic pump for providing hydraulic pressure to each of the hydraulic lift cylinders in the first and second vehicle lifting systems.
The apparatus may include a pump cart and a remote control operably connected to the pump cart, the remote control having at least one user control operable to cause selective hydraulic activation of at least one conduit in fluid communication with the pump cart.

-8-In some embodiments, the apparatus may include a remote control operably connected to the pump cart, the remote control having at least one user control operable to cause selective activation of at least one lock cylinder.
The remote control may include a wired pendant electrically connected to the pump cart.
The remote control may include a wireless pendant having a wireless connection with the pump cart.
In response to receiving signals from lock sensors on the first and second vehicle lifting assemblies, each vehicle lifting assembly may be operably configured to disable hydraulic activation of its lifting cylinders, and the remote control may be operably configured to indicate that the lifting cylinders have been disabled.
The remote control may include an emergency stop button operably configured to cause the lift cylinders to cease movement.
The pump cart may include brackets for holding hydraulic hoses.
The first lock assembly may be operable to cause at least one lock to pass substantially through the first support frame from a first side of the first support frame to a second side of the first support frame, the first and second sides enclosing an intermediate space within the first support frame.
In some embodiments, the first lock assembly may be operable to cause at least one lock to pass completely through the first support frame from a first side of the first support frame to a second side of the first support frame, wherein the first and second sides enclose at least a portion of the first lifting member within an intermediate space of the first support frame.
The at least one lock of the first lock assembly may be operably configured to interlock the telescoping movement of the first lifting member with respect to the first support frame.

-9-The at least one lock of the first lock assembly may intersect the first lifting member at at least two points and may also intersect the first support frame at at least two points.
The first lock assembly may be operably configured to interfere with sliding movement of the first support frame relative to the first lifting member by causing first and second pins of the first lock assembly to intersect the first support frame and the first lifting member.
The apparatus may be configured such that:
(a) the first and second pins may be inserted respectively on first and second opposite sides of the first lifting axis;
(b) the first pin may intersect the first support frame and the first lifting member on the first side of the first lifting axis; and (c) the second pin may intersect the first support frame and the first lifting member on the second side of the first lifting axis.
The apparatus may be configured such that:
(a) the first pin may intersect the first support frame at a first and second location;
(b) the first pin may intersect the first lifting member at a third and fourth location;
(c) the second pin may intersect the first support frame at a fifth and sixth location;
(d) the second pin may intersect the first lifting member at a seventh and eight location; and (e) the first, second, fifth, and sixth locations may be proximate to the third, fourth, seventh and eighth locations, respectively.
The first lock assembly may be operable to pull away or remove at least a portion of one lock of the first lock assembly from an access area for accessing the underside of a vehicle, wherein the access area is located between the first and second support frames.

-10-The first and second lock assemblies may include respective first and second lock assembly hydraulic cylinders which are both powered from a single hydraulic power connector on the apparatus.
The first and second lock assemblies and the first and second hydraulic lift cylinders may all be powered by hydraulic power received from a single multi-coupling hydraulic connector.
The top surfaces of the first and second lifting members may be operable to be raised from a first height to a second height, and the third and fourth lifting members may be operable to be raised from a third height to a fourth height, wherein the second height may be substantially different than the fourth height.
In accordance with another aspect of the invention, there is provided a method of lifting a vehicle. The method involves positioning a first lifting assembly (or apparatus) underneath a first end of the vehicle. The first lifting assembly includes first and second support frames in sliding engagement with respective first and second lifting members, first and second lock assemblies mounted on the first and second support frames, respectively, each lock assembly operable to selectively interfere with sliding movement of the support frame on which it is mounted relative to its associated lifting member.
The first lifting assembly also includes first and second hydraulic lift cylinders connected to the first and second support frames, respectively, and also connected to the first and second lifting members, respectively. Each lift cylinder is operable to cause telescoping movement of the corresponding lifting member with respect to the corresponding support frame. The first lifting assembly also includes a support frame connector connecting the first and second support frames. The method further involves positioning at least

-11-one lifting device underneath a second end of the vehicle and, using a remote control, causing hydraulic power to be supplied to the first lifting assembly at the first end of the vehicle and the at least one lifting device at the second end of the vehicle, to cause the first and second ends of the vehicle to be lifted.
The method further involves, using the remote control, causing the first and second lock assemblies to interfere with relative movement of the respective associated support frames and lifting members, to prevent the associated lifting members from retracting toward the respective associated support frames.
The method may further involve using the remote control to also remotely activate a locking system on the at least one lifting device, the locking system being operable to prevent lowering of the vehicle at the second end thereof.
In accordance with another aspect of the invention, there is provided a locking system for a vehicle lifting apparatus. The system includes a support frame of the vehicle lifting apparatus, the support frame being configured to guide telescoping movement of a lifting member of the vehicle lifting apparatus in sliding engagement with the support frame along a lifting axis. The lifting member has a distal end for lifting a vehicle. The system also includes at least one lock mounted on the support frame, the at least one lock being operable to move between an unlocked position in which the lifting member can extend away from or retract towards the support frame, and a locked position in which the at least one lock interferes with retraction of the lifting member toward the support frame. The system further includes at least one lock actuator operably configured to selectively cause the at least one lock to move between the unlocked position and the locked position, wherein the at least one lock actuator is powered from a power supply at a remote location.
In some embodiments, the at least one lock actuator selectively receives

-12-power for actuation from a power supply in response to a remote control operated from a further remote location.
The system may further include a pair of linear actuators mounted on opposite sides of the support frame, and a lock coupler coupling movement of the pair of linear actuators to the at least one lock.
The lock coupler may include a rod and the at least one lock may include at least one pin connected to or threaded onto the rod.
The at least one lock may include a pair of locking pins operably configured to be placed into the locked position by being inserted into respective openings of the support frame on opposite sides of the lifting axis in response to movement of the pair of linear actuators in a first, locking direction.
The at least one lock actuator may have an axis of movement perpendicular to the lifting axis.
The at least one lock actuator may have an axis of movement parallel to a longitudinal axis of a support frame connector which connects the support frame with a spaced apart, second support frame configured to support telescoping movement of a second lifting member along a second lifting axis, parallel to the first lifting axis.
The support frame, support frame connector, and second support frame, may at least partially frame a vehicle access space for allowing mechanics access to the vehicle undercarriage. The at least one lock actuator may be operable to withdraw at least a portion of the at least one lock from the vehicle access space.
The system may further include at least one sensor operable to detect a current position of the at least one lock, and in response to detecting the current position of the at least one lock, to send a signal representative of the current position for use in disabling the operation of at least a portion (e.g., in some embodiments, at least one lift cylinder) of the associated vehicle lifting apparatus.

-13-The at least one lock actuator may include at least one of a hydraulic cylinder, a pneumatic cylinder and an electric cylinder.
The system may further include at least one lock guide, mounted on the support frame, for guiding movement of the at least one lock as it moves between the locked position and the unlocked position.
The at least one lock actuator may be operable to cause the at least one lock to pass through the support frame from a first side of the support frame and to pass through the first support frame to a second side of the support frame, the first and second sides enclosing an intermediate space within the support frame. In some embodiments, the lock may protrude from the second side when fully inserted.
The at least one lock may be configured to interfere with telescoping movement of the lifting member with respect to the support frame by intersecting both the support frame and lifting member.
The system may further include first and second pins operable to be inserted into respective first and second openings on a first side of the support frame, when the first and second openings are aligned with respective third and fourth openings in the lifting member, to interfere with sliding relative movement of the support frame and lifting member.
The first and second pins may be operable to be inserted further into the first and second opening so as to pass through respective fifth and sixth openings in the lifting member and to protrude through respective seventh and eight openings on a second side of the support frame, opposite to the first side of the support frame, to interfere further with sliding relative movement of the support frame and lifting member.
In some illustrative embodiments of the invention described herein, a system is provided that allows the front and rear ends of a heavy vehicle such as a dozer to be raised without placing mechanics underneath the dozer or between the dozer blade and the unit. The system may use four hydraulic cylinders: two cylinders in a vehicle front lifting apparatus and two cylinders in

-14-a vehicle rear lifting apparatus. Both lifting apparatuses may be connected to an integrated single pump cart to allow the front and rear of the dozer to be lifted equally without having to manually adjust valves during operation. Once raised, the two lifting apparatuses in this embodiment are, in effect, converted into fixed stands by hydraulic actuation of locking pins mounted on the lifting apparatuses. Once the lifting apparatuses are locked, mechanics may freely work under the dozer even if the hydraulic pump cart hose attachments to the lift cylinders are disconnected. When it is desired to lower the vehicle, the locking pins are unlocked, and then the hydraulic cylinders are retracted. The lifting apparatuses may include spring loaded locking wheels and forklift inserts to facilitate moving the lifting apparatuses to different locations.
Such a design tends to provide increased stability by inhibiting the dozer from swaying from side to side when large components such as side frames are removed from the undercarriage. The remote locking mechanism provides protection against hydraulic failures. The mobility of the components of the system allows mechanics to reposition them with ease.
It will be appreciated that the remote locking method and mechanism described herein can be used in jacking systems that have only one lifting cylinder or which have more than two lifting cylinders.
For example, the disclosed remote locking method could be used on a standalone lifting device having only a single hydraulic lift cylinder and a single lifting member held within a single support frame, the support frame not being connected by a cross-beam or connector to any counterpart lifting device.
As a further possibility, such a standalone lifting device could be used in combination with the preferred embodiment of a dual cylinder lifting apparatus, for example, by using the dual cylinder lifting apparatus at the front of a vehicle in combination with two standalone lifting apparatuses at the rear of the vehicle. While the standalone lifting apparatuses are inherently less stable than a dual lifting apparatus, the use of even one dual lifting apparatus

-15-at one end of the vehicle provides some lateral stability, while retaining the benefit of flexible placement of the standalone lifting devices. With such an arrangement, a wider variety of vehicles may be lifted, since some vehicles may share the same dimensions and lifting point profile at one end (e.g., their front) while having different dimensions or differently placed lifting points at the other end (e.g., the rear).
However, any combination of single-point and multi-point lifting devices could still be locked against accidental lowering from a single remote control using the methods and mechanisms described herein and adaptations thereof.
Other embodiments, aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.
BRIEF DESCRIPTION OF THE DRAWINGS
In drawings which illustrate embodiments of the invention, Figure 1 is a general schematic depiction of a remotely controllable locking vehicle lifting system 50 according to one embodiment of the invention, the vehicle lifting system including first and second vehicle lifting apparatuses 100 and 150, a hydraulic power unit or hydraulic power system 180 and a remote control 190;
Figure 2A is an isometric view of the first vehicle lifting apparatus 100 shown in Figure 1 in accordance with one exemplary embodiment of the

-16-invention, the first apparatus being operable to lift the rear portion of a vehicle;
Figure 2B is an isometric view of the second vehicle lifting apparatus 150 shown in Figure 1 in accordance with one exemplary embodiment of the invention, the second apparatus being operable to cooperate with the first apparatus 100 shown in Figure 2A to lift the front portion of the vehicle, the first and second apparatuses 100 and 150 being shown in Figures 2A and 2B in a fully extended and locked lifting position but with certain items removed (e.g., hydraulic connection ports and electrical parts) for clarity;
Figure 3 is a front view of the first vehicle lifting apparatus shown in Figure 2A;
Figure 4 is a side view of the first vehicle lifting apparatus shown in Figure 2A;
Figure 5A is a partial sectional view of the first vehicle lifting apparatus shown in Figures 2A and 3 along the lines 5A-5A;
Figure 5B is a top view in partial cross-section of the first vehicle lifting apparatus shown in Figures 2A and 5A along the lines 5B-5B;
Figure 6 is a top view in partial cross-section of the first vehicle lifting apparatus shown in Figure 2A in a locked position;
Figure 7 is an isometric view of a support frame of the first vehicle lifting apparatus shown in Figure 2A, the support frame being shown in a partial state of disassembly for clarity, with several hidden openings shown in dotted outline;

-17-Figure 8 is an isometric view of a first (rear) lifting member operable to telescopically engage the support frame shown in Figure 7;
Figure 9 is an isometric view of a second (rear) lifting member operable to telescopically engage a second support frame analogous to that shown in Figure 7;
Figure 10 is an isometric view of a support frame of the second vehicle lifting apparatus shown in Figure 2B, the support frame being shown in a partial state of disassembly;
Figure 11 is an isometric view of a first (front) lifting member operable to be inserted into the support frame shown in Figure 10 and to engage in telescopic movement therein;
Figure 12 is an isometric view of a second (front) lifting member operable to be inserted into the support frame shown in Figure 10 or an equivalent frame and to engage in telescopic movement with respect to the support frame;
Figure 13A is an isometric view of a support frame connector connecting the first and second support frames of the first vehicle lifting apparatus shown in Figure 2A;
Figure 13B is atop view of the support frame connector shown in Figure 13A;
Figure 14A is an isometric view of a support frame connector connecting the first and second support frames of the second vehicle lifting apparatus shown in Figure 2B;

-18-Figure 14B is a top view of the support frame connector shown in Figure 14A;
Figure 15A is an isometric view of a spring-loaded lockable wheel assembly used on the first and second vehicle lifting apparatuses shown in Figure 2;
Figure 15B is a side sectional view of the wheel assembly shown in Figure 15A;
Figure 16A is a top view of a locking pin used to lock the lifting members shown in the preceding Figures to prevent retraction of the lifting members with respect to the associated support frames, the pin being shown contacting a limit switch depicted in broken outline;
Figure 16B is a side view of the locking pin shown in Figure 16A;
Figure 17 is an isometric view of an interface element (for example, a spacer attachment) optionally used in conjunction with the lifting members shown in Figures 8 and 9 as a vehicle engaging surface in cases where the vehicle to be lifted lacks an attached ripper unit;
Figure 18 is a side view of the vehicle lifting assemblies shown in Figure 2 lifting a dozer having no ripper assembly installed at its rear;
Figure 19 is a side view of the vehicle lifting assemblies shown in Figure lifting a dozer having a ripper assembly installed at its rear;
Figure 20A is a rear view of the dozer shown in Figure 18 (i.e., without a ripper assembly installed), just before it is lifted by the vehicle lifting apparatus of Figure 2A, wherein the lock assemblies are

-19-shown to be in an unlocked position such that a substantial portion of the respective locks are located between the support frames;
Figure 20B is a rear view of the dozer shown in Figure 18, just after it is lifted by the vehicle lifting apparatus shown in Figure 2A after the lock assemblies have been moved into a locked position to prevent any retraction or lowering of the lift members toward the ground;
Figure 21A is a front view of the dozer just before it is lifted by the vehicle lifting apparatus shown in Figure 2B, the lock assemblies being shown in an unlocked position such that a substantial portion of the respective locks are located between the support frames;
Figure 21B is a front view of the dozer, just after it is lifted by the vehicle lifting apparatus shown in Figure 2B and after the lock assemblies have been moved into a locked position, thereby opening up front end access to the underside of the dozer;
Figure 22A is a top plan view of an embodiment of a lifting apparatus having multiple quick connecting interfaces for hydraulics and/or electrical connections mounted on both the left lifting assembly and on the right lifting assembly of the lifting apparatus;
Figure 22B is a top plan view of an embodiment of a lifting apparatus having a consolidated multi-coupling quick connector(s) for all hydraulic and electrical connections on the left hand side lifting assembly only;
Figure 23 is a schematic depiction of one embodiment of a sensor circuit based on four limit switches in series and connected to a hoist disable controller operable to disable retraction of the lift cylinders in response to at least one limit switch detecting that at least one

-20-locking pin has been partially inserted into a corresponding locking pin receptacle provided in the support frames;
Figure 24 is a schematic depiction of one embodiment of an electrical circuit that could be used to control a vehicle lifting apparatus.
DETAILED DESCRIPTION
Referring to Figure 1, a vehicle lifting system according to one embodiment of the invention is shown generally at 50. The vehicle lifting system 50 includes first and second vehicle lifting apparatuses (100 and 150), a hydraulic power system 180, and a remote control 190, such as a wired or wireless pendant, to allow an operator to remotely control the hydraulic power unit and thus the first and second vehicle lifting apparatuses from a safe distance.
The first vehicle lifting apparatus 100 includes first and second vehicle lifting assemblies 120 and 130, and the second vehicle lifting apparatus 150 includes third and fourth vehicle lifting assemblies 160 and 170. The first vehicle lifting assembly 120 includes a first lift system 122, cooperating with a first lock system 124 for locking the first lift system against unsafe retraction, and at least one sensor 126 for providing feedback about the position or status of at least one component of the first lift system (e.g., a lock position).
Similarly, the second vehicle lifting assembly 130 includes a second lift system 132, cooperating with a second lock system 134, and at least one sensor 136. The third and fourth vehicle lifting assemblies (160 and 170) similarly each include a respective lift system (162 and 172), lock system (164 and 174), and at least one sensor (166 and 176). Figure 1 shows a general schematic depiction of hydraulic connections (e.g., 140, 142) and electrical connections (e.g., 144, 146, 148) among system components (one line may represent a plurality of connections).

-21-The components of the system 50 may be designed to be mobile. The first and second vehicle lifting apparatuses 100 and 150 may be wheeled up to the corresponding rear and front ends of a vehicle, which in this embodiment is a Caterpillar dozer, such that the first, second, third and fourth vehicle lifting assemblies are positioned, respectively, at the rear left, rear right, front left, and front right portions of a vehicle. Vehicle engaging portions of the lifting apparatuses are designed to have a shape complementary to suitable lifting points on the vehicle and are positioned to be subjacent to these lifting points.
The first and second vehicle lifting systems 100 and 150 are hydraulically connected to and operable to be powered by hydraulic fluid pumped from the hydraulic power system 180. The hydraulic power system 180 is controlled by and is responsive to control signals sent by the remote control 190 and/or in response to input received from status and position sensors (e.g., 126, 136, 166, 176) on the lifting assemblies. The remote control 190 generates control signals for controlling hydraulic flows in response to input received from an operator and/or in response to input received from status or position sensors (e.g., limit switches) mounted on the various vehicle lifting apparatuses.
The hydraulic power system 180 includes one or more hydraulic power sources 182 coupled to one or more valves 184, and a reservoir 188, wherein at least some of the hydraulic power sources and at least some of the valves are controlled by a control unit 186 operable to receive signals from the remote control 190. The control unit 186 could include a PLC controller, a microcontroller, or a mechanical controller, for example, for controlling the valves. In this embodiment, the hydraulic power system 180 includes at least one mobile hydraulic pump cart. In some embodiments, the hydraulic power unit may not need to be mobile. The hydraulic power sources 182 may include a multi-piston hydraulic pump capable of supplying an even flow to a plurality of hydraulic cylinders. In this embodiment, a four-piston hydraulic pump is used to power four hydraulic circuits respectively associated with four

-22-lift cylinders, with each piston powering a lift cylinder, and the system is rated to handle hydraulic pressures of up to about 10,000 psi. In this embodiment, the four pistons are connected to the vehicle lifting assemblies 120, 130, 160, 170, respectively, however, it will be appreciated that the pump cart may provide more or fewer pistons with the respective hydraulic circuits being adapted accordingly. The hydraulic valves 184 includes flow valves controlled by the control unit which may be configured to cause each of the lift cylinders to be raised or lowered evenly by adjusting the flow valves. In some embodiments the valves 184 may be integrated with the power sources 182.
Each of the lifting cylinders is associated with at least one check valve or load holding valve operably configured to prevent the lifting cylinder from lowering suddenly in case of a hydraulic leak or pressure loss. Each load holding valve (e.g., 649 in Figure 22A) is connected to its associated lifting cylinder (e.g., 640) at a point proximate to the associated lifting cylinder. The load holding valves also allow the hydraulic hoses of the system to be disconnected from the lifting assemblies after a dozer has been hoisted, by enabling each lift cylinder to continue to safely hold its respective load. Consequently, the hydraulic equipment used to raise the dozer (e.g., a pump cart, as described below), can be used to power a second vehicle lifting system to lift a second dozer, while the first dozer remains hoisted for repairs or maintenance work.
The remote control unit 190 generally includes controls 192 and indicators 194. The controls 192 may include various types of switches, toggles, dials, buttons, sliders and the like, which an operator can manipulate to cause appropriate control signals to be sent to the hydraulic power system 180.
Examples of controls may include buttons or toggle switches for causing the front or rear vehicle lifting apparatuses to begin lifting a vehicle or to lower the vehicle, buttons or switches for causing the lock assemblies of the vehicle lifting apparatuses to assume an engaged (locked) position or a disengaged (unlocked) position, and an emergency stop button operably configured to

-23-cause the hydraulic power system 180 to suspend operation by disabling its hydraulic power source 182 or by causing the control valves 184 to cease to supply further hydraulic fluid to one or more cylinders, for example. Some user controls may have multiple functions which vary depending on user input received from other user controls. In some embodiments, at least some of the user controls may be located or duplicated on the pump cart.
In one embodiment, the controls on the remote control may include a first three position switch having positions corresponding to "PINS", "OFF" and "HOIST", and a second three position switch having positions corresponding to "ADVANCE", "HOLD" and "RETRACT", the second switch being biased to return by default to the middle HOLD position. The first switch is operable to selectively direct and connect hydraulic power either to the lifting cylinders (in the HOIST position) or to the hydraulic cylinders for actuating a lock (in the PINS position), wherein the lock may include locking pins. In effect, the first switch functions is operable to select a set of cylinders for possible activation.
When the first switch is set to OFF, input from the second switch is ignored, and none of the cylinders receive power.
The second switch is operable to cause the set of cylinders selected by the first switch to either advance (in response to the ADVANCE position of the second switch) or retract (in response to the RETRACT position). If the user ceases to physically operate the second switch, it returns by default to the HOLD position, in which the cylinders are held in position but are neither advanced nor retracted. The first and second switches are operable to cause relays and/or solenoid operated flow valves and/or solenoid operated directional valves (in an embodiment that uses double-acting cylinders) to configure the hydraulic system to direct hydraulic power either to the lift cylinders or to the pin cylinders. One exemplary embodiment of a possible electrical control circuit is shown in Figure 24, more fully described below.

-24-The remote control 190 also includes indicators 194 which may be visual, auditory and/or tactile indicators for indicating one or more statuses or states of the vehicle lifting systems 100 or 150 or of the hydraulic power system 180.
Without limiting the generality of the indicators that could be used, some examples of possible indicators include lights, gauges, LCD displays, speakers, and vibration feedback mechanisms. It will be appreciated that other types of controls 192 and indicators 194 may also be used to alert the operator of relevant information such as the position of the hydraulic lift cylinders or the lock assemblies, for example, in response to information received from sensors (e.g., limit switches) mounted on the lifting assemblies.
To give one example, a visual indicator may inform the mechanic that the lift cylinders are raised to their maximum height. Another visual indicator may show that the locking pins are completely engaged. Yet another visual indicator may show that all the locking pins have been released and that it is now safe to lower the dozer. Alternatively or in addition, a plurality of visual indicators may be combined into a display, for example, an LCD display. For example, the LCD display may indicate whether the lift cylinders have been fully raised, and also whether the lock has been fully engaged (e.g., pin cylinders have been extended) such that it is safe for the mechanic to crawl under the dozer. Additional sensors, such as position sensors or limit switches, may be installed on the lifting system to facilitate other types of feedback to the operator. In some embodiments, at least some of the status indicators may be located (or duplicated) on the pump cart.
Referring now to Figures 2A, 2B and 3-6, a first embodiment of a first vehicle lifting apparatus for lifting the rear of a vehicle is shown generally at 100, and a first embodiment of a second vehicle lifting apparatus for lifting the front end of the vehicle is shown generally at 150. For the illustrated embodiment, the vehicle intended to be lifted is a Caterpillar D8T dozer.

-25-Each vehicle lifting apparatus (100, 150) in this embodiment includes at least one hydraulic lift assembly (e.g., 122, 132, 162, 172), at least one hydraulic lock assembly (e.g., 300, 302, 304, and 306), and at least one sensor or limit switch (e.g., 400, 402, 404, 406) for sensing the position of the hydraulic lift assemblies and/or the hydraulic lock assemblies, and signaling this information to the remote control (190 in Figure 1) and/or hydraulic power system (180 in Figure 1), possibly to cause a safety circuit or other mechanism to disable at least one associated hydraulic lift system.
The first vehicle lifting apparatus 100 includes a first support frame 200 in telescopic engagement with a first lifting member 210, a second support frame 202 in telescopic engagement with a second lifting member 212, and a first support frame connector 230 (also shown in Figure 13), generally perpendicular to the first and second support frames, and fixedly connecting and holding the first and second support frames in generally parallel, spaced apart relation. By connecting the first and second support frames, the connector provides substantial lateral stability for the overall apparatus. In addition, the lifting members 210 and 212 are about the same height as their associated support frames 200 and 202, thereby maximizing the area of contact between the outer walls of the lifting members and the corresponding inner walls of the associated support frames, thus further enhancing stability.
Put another way, in this embodiment, lift cylinders raise an inner generally tubular structure (the lift members 210 and 212) which is configured to slide concentrically along a respective lifting axis inside a outer generally tubular structure (the support frames 200 and 202), wherein the outer tubular structure is dimensioned to accommodate the inner tubular structure, and because the tolerances between the inner and outer tubular structures are tight, the outer tubular structure (support frame) provides extra support to the inner tubular structure (lifting member) to prevent side-to-side and front-to-rear loading as it guides the telescoping movement of the inner structure relative to the outer structure. In view of these structural features to enhance

-26-stability, it is unnecessary to have a stabilizing connector or cross-brace connected toward the top of the lifting members, which would tend to impede mechanic access to the undercarriage.
In this embodiment, the first support frame 200 and first lifting member 210 enclose a first hydraulic lifting cylinder (640 in Figure 22), whereas the second support frame 202 and second lifting member 212 enclose a second hydraulic lifting cylinder (642 in Figure 22). The first and second hydraulic lift cylinders (640 and 642) include respective first and second hydraulic lift cylinders shafts operably configured to extend along respective first and second lifting axes (220 and 222 in Figure 3), the first and second hydraulic lift cylinders each having respective first and second (opposite) ends. The first vehicle lifting apparatus 100 further includes at least first and second wheel assemblies (250, 252, 254, 256) mounted on the first and second support frames (200 and 202), respectively, each of the first and second wheel assemblies having at least one spring loaded suspension (Fig. 15), which may include at least one lockable wheel. Figure 2A also shows an optional protective shroud 259 for protecting a portion of the locking mechanisms located in the intermediate space between the first and second support frames.
The first hydraulic lifting cylinder 640 is connected at its two opposite ends to the first support frame 200 and the first lifting member 210, respectively, and the second hydraulic lifting cylinder 642 is connected at its opposite ends to the second support frame 202 and the second lifting member 212, respectively. The first and second support frames (200 and 202) include respective first and second guide channels (e.g., 260 in Fig. 10) to guide telescoping movement of the first and second lifting members 210 and 212 along the first and second lifting axes 220 and 222, respectively.
Referring to Figure 10, in this embodiment, the guide channel 260 includes the inner surfaces of first and second walls 262 and 264 oriented in a first

-27-orientation, and the inner surfaces of third and fourth walls 266 and 268, oriented in a second orientation perpendicular to the first orientation. The first, second, third, and fourth walls 262, 264, 266, and 268 are interconnected to form a generally tubular structure enclosing an intermediate space and defining the guide channel operable to direct the telescoping movement of a lifting member held therein. In other embodiments, the guide channel may be implemented at least in part by utilizing rails, rollers, and the like, to guide the telescoping movement of the lifting member with respect to the support frame.
In particular, actuation of the first and second cylinders 640 and 642 in first (extension) direction causes extension of the first and second hydraulic lift cylinder shafts, which in turn causes the first and second lifting members 210 and 212 to extend away from the first and second support frames (200 and 202), respectively (in a motion corresponding to "hoisting" a vehicle), whereas movement of the cylinders in a second (retraction) direction causes retraction of the first and second hydraulic lifting cylinder shafts, which in turn causes the first and second lifting members to retract towards the first and second support frames, respectively (in a motion corresponding to "lowering" a vehicle). In this embodiment, the first and second support frames 200 and 202 are dimensioned and configured to facilitate sliding engagement with the first and second lifting members 210 and 212, respectively, during such extension and retraction. Sliding engagement is further facilitated by lubrication which may be provided by numerous grease fittings (e.g., 270, 272, and 274 in Fig. 10) embedded in each support frame. Relatively tight tolerances are used as between the support frames and the associated lifting members in order to prevent forward-backward and side-to-side movement of the load. In general, the lifting apparatus is constructed of plates and hollow structural sections which are preferably welded or bolted together using structural quality steel with a suitable load rating.

-28-While the above embodiment uses square or rectangular shaped tubular structures for the support frames and lifting members, in other embodiments these structures could be provided in a different shape such as hexagonal, octagonal or circular, for example, providing that the support frames and lifting members were closely mated to provide a guide channel in the support frames for the respective lifting members.
The hydraulic lift cylinders may be double-acting hydraulic cylinders operable to provide at least about 36,000 lbs of lifting force per cylinder (in the case of an embodiment intended to lift a D8 dozer), however, cylinders with a lesser or greater lifting ability, or single acting cylinders with spring or gravity return, may be used in some embodiments depending on the specific nature of the vehicle lifting task at hand. As single acting cylinders typically require only one port, the number of hydraulic fluid connections may be reduced at the expense of losing the ability to apply controlled hydraulic pressure in both the extension and retraction directions. In such an embodiment, for example, a lift cylinder could be driven by a single hydraulic port and hose, instead of a pair of ports and hoses. It will be appreciated that the hydraulic lift cylinders are typically connected by conventional hydraulic mountings to the support frames and the lifting members using fasteners, for example, bolts.
The second vehicle lifting apparatus 150 is similar in structure to the first vehicle lifting apparatus 100. The apparatus 150 includes a third support frame 204 in telescopic engagement with a third lifting member 214, a fourth support frame 206 in telescopic engagement with a second lifting member 216, and a second frame support connector 232 (also shown in Figure 14), fixedly connecting and holding the first and second support frames in generally parallel, spaced apart relation. In this embodiment, the third support frame 204 and third lifting member 214 enclose a third hydraulic lifting cylinder, and the fourth support frame 206 and fourth lifting member 216 enclose a fourth hydraulic lifting cylinder. The third and fourth hydraulic lift

-29-cylinders include respective third and fourth hydraulic lift cylinders shafts operably configured to extend along respective third and fourth lifting axes, the third and fourth hydraulic lift cylinders each having respective first and second (opposite) ends. The second vehicle lifting apparatus 150 further includes at least first and second wheel assemblies (280, 282, 284, 286) mounted on the third and fourth support frames (204 and 206), respectively, each of the third and fourth wheel assemblies having a spring loaded suspension and at least one lockable wheel (e.g., 258 in Figure 15).
At least one lockable wheel is located on the "outside" of the vehicle lifting apparatus (i.e., on the side of the vehicle lifting apparatus accessible to the mechanic). Alternatively, at least two outwardly facing wheels of each vehicle lifting assembly will be equipped with a locking mechanism to secure them in place. Referring to Figure 15, in one embodiment, a locking wheel includes a wheel 258 cooperating with a suspension, for example, a spring loaded suspension including a spring-engaging platform 499, a compressible spring 498, and a wheel extension member 496, the spring loaded suspension being operably connected to the support frame (e.g., 204) by at least one strut (279 in Figure 10) and configured to raise the lifting apparatus off the floor at least about half an inch when no load is being lifted. The wheels are preferably able to rotate up to 360 degrees as the vehicle lifting assembly is moved across a floor. Consequently, a mechanic is able to push the vehicle lifting assemblies into position. Once the vehicle lifting apparatuses are correctly positioned underneath the dozer, the mechanic locks their wheels to keep them correctly positioned as the lifting operation begins. One method of locking the wheels involves, positioning the lifting apparatus underneath a vehicle, activating the lifting cylinders to cause the lifting members (or lifting interface elements mounted on the lifting members) to contact the vehicle, activating the lifting cylinders further to compress the springs inside the wheels to cause the lifting apparatus to be lowered to the ground. Once the base of the support frame touches the ground, the lifting apparatus is

-30-effectively locked in place. When a sufficient load lifting force is applied, the spring loaded suspension collapses enough to cause the vehicle lifting apparatus to rest its frame fully on the floor thereby providing support and stability. In another embodiment, the wheels may have manually operable locking mechanisms on the wheels themselves.
Referring to Figures 2, 8, 9, 10 and 11, the lifting members (210, 212, 214, 216) include respective first, second, third and fourth vehicle engaging portions (211, 213, 215, 217) for engaging respective first, second, third and fourth portions (i.e., lifting areas) of the vehicle undercarriage. Each of the vehicle engaging portions have a complementary shape to and are positioned to line up with corresponding lifting points located on the frame of at least one particular type of vehicle that the lifting system is intended to lift (e.g.
see Fig.
18). In the embodiment shown in Figure 2, the vehicle engaging portions 211 and 213 may include respective vehicle interface elements or spacers 218 and 219 as shown for the case where the first vehicle lifting apparatus 100 is being used to lift the rear end of a Caterpillar D8T dozer without a ripper assembly installed. The vehicle engaging portions and/or the interface elements may be diamond knurled to provide added traction. In this embodiment, the interface elements 218 and 219 are designed to be removable and may be stored in respective pockets or holders on the support frame connector when they are not needed (e.g., when the apparatus is being used to lift a D8T dozer with a ripper).
The vehicle interface element or spacer 219 is (shown in an isometric view in Figure 17 looking up at its bottom side) may have at least one protrusion 221 operable to be received in at least one corresponding receptacle (e.g., 223 in Figure 9) to secure the spacer 219 onto the corresponding lifting member 213.
In this embodiment, the spacers 218 and 219 compensate for the space that would be otherwise taken up by the ripper assembly attachment plate if a ripper assembly attachment was installed. If the ripper assembly is installed

-31-on the dozer, however, the ripper assembly attachment plate will be present (340 in Fig. 19) and thus the spacers 218 and 219 are removed and placed in a holder 308 on the support frame connector 230 for convenient safekeeping.
In an alternative embodiment, the rear lifting surfaces of the vehicle engaging portions 211 and 213 may be configured to engage a pivot shaft housing at the rear of the vehicle. The pivot shaft housing may have different shapes for different vehicles (e.g., curved for D8 and D11 dozers, and substantially flat for the D10 dozer), and thus permanent or detachable rear lifting surfaces which have a suitable complementary shape may be provided on the vehicle engaging portions 211 and 213. In addition, the shape of the lifting area may vary depending on whether certain equipment has been installed on the vehicle. A complementarily shaped removable adapter may be used to enable the lifting surface to properly interface to the lifting location on the vehicle. For example, a D8 dozer without a ripper (e.g., Figure 18) may require the custom designed spacer or interface element 218 and 219 to be connected to the lifting members 210 and 212 associated with the rear lifting apparatus. The spacers may be removed when lifting a D8 dozer with a ripper (342 in Fig. 19).
Referring to Figures 2 through 6, the first vehicle lifting apparatus 100 further includes first and second lock assemblies 300 and 302, mounted on the first and second support frames 200 and 202, respectively, each lock assembly comprising at least one lock (e.g., 310 and 312) and at least one lock actuator (e.g., 320 and 322 or 324 and 326) operably configured to selectively cause the at least one lock to move between an unlocked position (e.g., see locks in Figs. 20A and 21A) in which the associated lifting member (e.g., 210) is able to extend away from or retract towards the associated support frame (e.g., 200), and a locked position (e.g., see locks in Figs 20B and 21B) in which the at least one lock interferes with retraction of the associated lifting member toward the associated support frame. The at least one lock may cooperate

-32-with at least one receptacle of complementary shape to the lock and operable to receive the at least one lock. For example, a receptacle may be formed by an alignment of the support frame 200 relative to the lifting member 212, to interfere with retractive movement of the lifting member toward the support frame. In one embodiment, a lock receptacle may be formed by two openings (480 and 484 in Fig. 7) on opposite sides of the support frame (e.g., 200) coinciding with two corresponding openings (e.g. 481 and 485 in Fig. 9) on opposite sides of the lifting member (e.g., 212), such that the lock is operable to intersect the support frame and lifting member twice each. The movement of the support frame and lifting member is interlocked at the points where the lock passes from the support frame into the lifting member.
In an alternative embodiment, a lock receptacle may be formed by two openings on opposite sides of the support frame (e.g., 200) coinciding with two corresponding notches on opposite sides of the lifting member (e.g., lifting member 210 in Figure 8). As a further alternative, a lock receptacle may be formed simply by the two openings (e.g., 480 and 484 in Figure 7) on opposite sides of the support frame 200, for example, where the lock has a flat surface and thus does not require corresponding receptacle to be machined to the bottom portion of the lifting members (e.g., 210 and 212). In the latter embodiment, the lifting members 210 and 212 are nevertheless prevented from lowering when at least one lock has passed through the support frame 200 from one side to the other and thus presents an obstacle that prevents a lower straight edge of the lifting member from passing below the at least one lock. As will be described below, the locking assembly may use a plurality of locks per support frame and the lifting member. For example, if two lock receptacles are used as described above, a lock is operable to intersect the support frame and lifting member four times each.
In the embodiment shown in Figure 2, the first lock assembly 300 includes a first pair of linear lock actuators (320 and 322) mounted on opposite sides of

-33-the first support frame by using mounts (e.g., brackets or spacers such as 276 in Figure 10), and a lock coupler 360 coupling movement of the first pair of linear actuators to the at least one lock (310) of the first lock assembly.
The linear actuators (320 and 322 in Figure 6) in this embodiment each have an axis of movement that is generally perpendicular to the first and second lifting axes (220 and 222 in Figure 3) and generally parallel to a longitudinal axis (224 in Figure 3) of the support frame connector 230.
In this embodiment, the linear actuators are hydraulically powered cylinders, which may be rated for up to 3,000 psi of pressure and capable of producing up to about 250 lbs of actuation force. Other pressure- and force-rated cylinders may be used in alternate embodiments. Although typically the lock assemblies require far less power to operate than the lift cylinders, any hydraulically powered linear actuators associated with the lock assemblies may be fed from a high-pressure hydraulic source for the lift cylinders by using a suitable pressure-reducing valve such as the Power Team 9604 valve which is operably configured to provide anywhere from 1000 to 5000 psi adjustable outlet pressure based on a user-adjustable control. In alternative embodiments, the lock actuators could be pneumatically powered or electrically powered, for example, the lock actuators could be electric cylinders driven by an electric motor.
In this embodiment, the at least one lock 310 may include a pair of pins 340 and 342 operably configured to be placed into the locked position by insertion into and movement within at least one lock guide such as lock guides 370 and 372 including the corresponding openings 480 and 482 of the first support frame 200 offset on opposite sides of the first hydraulic lift cylinder shafts, in response to movement of the first pair of linear actuators 320 and 322 in a first, locking direction. Conversely, the at least one lock 310 (including pins 340 and 342 in this embodiment) may be removed from the locked position and placed into an unlocked position by the linear actuators 320 and 322

-34-causing the pins to be withdrawn from the openings 480 and 482 sufficiently to remove the pins from interfering with movement of the lifting member (210 or 212) inside the support frame 200. In this embodiment, the pins of the locking assembly effectively provide four locking locations per lifting cylinder.
Movement from the lock actuators 320 and 322 may be transferred to the at least one lock 310 with a lock coupler 360, which may include a rod in this embodiment. In this embodiment, the pins 340 and 342 are threaded onto the rod using a throughole (490 in Figure 16). The length of the pins 340 and 342 is sufficient to pass completely through the lifting "box" formed by the support frame 200 and the lifting member (210 or 212) concentrically disposed within the support frame, with some additional length to allow the pin to be connected to the lock coupler 360.
The locking assembly 300 further includes at least one lock guide, which in this embodiment includes two circular tubes 370 and 372 in communication with corresponding openings into the support frame 200, to facilitate the pins 340 and 342 being inserted into and passed through the support frame or withdrawn therefrom along a locking axis. The pins in their locked position in effect intersect the support frame and thereby lock the lifting member against retraction with respect to the support frame. As can be seen in Figures 20A
and 21A, the lock guide allows the lock to remain at least partially inserted in the guide at all times in preparation for movement at any time. Thus, the lock guide (370 and 372) serves to guide the associated lock as it moves between the locked position and the unlocked position, and in this embodiment, at least a portion of the associated lock is disposed in the lock guide.
In this embodiment, when the lock (e.g., 340 or 342) is completely inserted, it passes through a first wall of the support frame (and possibly the lifting member), and passes through a second wall of the support frame (and possibly the lifting member) on the opposite side. In the case of the preferred

-35-embodiment, which inserts first and second locking pins into respective first and second openings in the support frame, these first and second pins when fully inserted protrude at least in part from the opposite side of the support frame (e.g., 430, 432, 434 and 436 in Figure 6). In one embodiment, when the lifting member (e.g., 212) is fully extended and positioned to be locked, the first and second pins are caused to pass through the lifting member, the openings (e.g., 481, 483, 485, 487 in Figure 9) of which align with proximate corresponding openings in on both sides of the support frame 200. When the locking pins protrude slightly at the outer ends of the support frame, they serve as a visual indication that the pins have been fully inserted.
In this embodiment, the second lifting assembly 130 of the first lifting apparatus 100 includes a second lock assembly 302 similar to the first lock assembly 300 on the first lifting assembly 120. The second lock assembly 302 includes at least one lock 312 (including locking pins 344 and 346 in this embodiment), the at least one lock being movable along a locking axis defined by at least one lock guide 374 and 376, and at least one lock actuator (324 and 326), coupled to the at least one lock with a lock coupler 362, the at least one lock actuator being operably configured to move the at least one lock between a locked position and an unlocked position. In the locked position (shown in Figure 6), the at least one lock passes through the support frame 202 to emerge on the opposite side, and is disposed to prevent the lifting member 212 from retracting. More particularly, actuation of the lock actuators 324 and 326, causes a force to be transferred from the lock actuators via the lock coupler 362 to the locking pins 344 and 346 in the direction of a first locking axis coaxial with the locking pin and parallel to the lock actuators. Guided by the lock guide 374, one lock, namely, the locking pin 344 moves along the locking axis to engage the support frame 202 and lifting member 212 at a first locking area 450 on an inner side of the lifting assembly 130 and also at a second locking area 454 on an outer side of the lifting assembly 130. Similarly, actuation of the lock actuators 324 and 326

-36-causes the locking pin 346 to move as directed by the lock guide 376 along a second locking axis coaxial with the locking pin 346 and lock guide 376 and parallel to the first locking axis. In a fully locked position, the locking pin 346 engages the support frame 202 and lifting member 212 at a third locking area 452 on an inner side of the lifting assembly 130 and also at a fourth locking area 456 on an outer side of the lifting assembly 130.
Figure 4 provides a side view of the lifting apparatus 100 with several hidden surfaces shown in dotted outline to better illustrate how the locks in this embodiment interfere with retractive movement of the lifting member 212. As will be observed from Figure 4, the lifting member 212 has lock engaging surfaces 478 and 480 configured to engage corresponding locking surfaces on respective locks, for example, locking pins 344 and 346. The lock engaging surfaces 478 and 480 in one embodiment are lock receptacles formed by notches complementary in shape to the locking pins 344 and 346, the lock receptacles being formed in the bottom portion of the lifting member 212. In an alternative embodiment, shown in Figure 9, the lock receptacles may be openings (481, 483, 485, and 487) formed in the bottom portion of the lifting member 212. In a still further embodiment, the lock engaging surface may simply be a straight bottom edge of the lifting member, for example, in the case where the lock itself has a complementary shaped straight edge.
Referring back to Figure 4, retractive movement of the lifting member 212 is prevented because the lock engaging surfaces 478 and 480 of the lifting member encounter an opposing force from the locking pins 344 and 346. The locking pins 344 and 346 in turn receive support at the point of their engagement with the walls of the support frame 202, for example, at openings 480, 482, 484 and 486 shown in Figure 7. The walls of the support frame 202 in turn communicate the weight of the load to the ground.
The inner surface of opposing walls of the support frame (e.g., 470 and 472 in Figure 4) engage in this embodiment with corresponding outer surfaces of

-37-opposing walls (e.g., 474 and 476) of the lifting member (e.g., 212), thereby providing front-to-back stability, whereas similar engagement between the perpendicularly oriented respective opposing walls of the support frame and lifting member provides side-to-side stability for the lifting assembly 130.
In this embodiment, the dual locks on each lifting assembly (e.g., 374 and 376) do not intersect the path of a piston rod of the associated lift cylinder as it extends or retracts along a lifting axis of the respective lifting assembly (e.g., 130); rather, the dual locks are spaced apart to be approximately equidistant from the lifting axis and on opposite sides thereof. In addition, the lock actuators of a first lifting assembly (e.g., 120) are configured so as not to intersect the path of the lock actuators of the complementary lifting assembly (e.g., 130) to which the first lifting assembly is conjoined. As shown in Figures 20A and 21A, in this embodiment, the lock actuators, lock couplers and locks of the left and right lifting assemblies of a lifting apparatus are configured to move along different parallel, spaced apart planes, thus even when all locks are fully unlocked, there is no interference between the lock mechanisms of the left and right lifting assemblies. In another embodiment, the left and right lock assemblies may be configured to operate in a common plane, for example, if the relative distance between the left and right lifting assemblies is sufficiently large and/or the support frames are sufficiently narrow.
Advantageously, the use of dual locking pins provides four locking areas per hydraulic lift cylinder (e.g., 640) at which protection is provided against accidental lowering. Thus, one lifting apparatus (e.g., 100) which includes left and right lifting assemblies (120 and 130) in effect has eight locking areas in total (e.g., areas 440, 442, 444, 446 for left lifting assembly 120, and areas 450, 452, 454, 456 for right lifting assembly 130). Thus, a system 50 which includes similar first and second lifting apparatuses 100 and 150 has a total of sixteen locking areas for guarding against accidentally lowering the lifted load.

-38-The present embodiment uses locking pins which are made of AISI 4140 HTSR material of about 1 1/4 inches in diameter. In alternative embodiments, it is possible to use just one locking pin, however, one pin provides only two locking areas for interfering with relative movement between the support frame and associated the lifting member, thus it is important to ensure that the load rating of the single pin is sufficient to support the more concentrated forces. In other words, thinner locks can be used if a plurality of locks are used per hydraulic lift cylinder.
In this embodiment, the second lifting apparatus 150 includes dual lifting assemblies 160 and 170 each associated with a respective lock assembly (304 and 306 in Figure 2B) capable of locking the respective lifting assembly, the lock assemblies 304 and 306 being similar to the lock assemblies 300 and 302 installed on the first lifting apparatus 100. Accordingly, it is unnecessary to describe the lock assemblies 304 and 306 in detail. It will be appreciated that the second lifting apparatus may not be identical with the first lifting apparatus 100. For example, the second lifting apparatus 150 may be dimensioned differently and/or have a different range of lifting motion and/or height, and may be equipped with different vehicle or equipment engaging surfaces or interface elements, as appropriate for lifting the portion of the vehicle or equipment for which the second lifting apparatus is designed.
In this embodiment, the first and second support frames 200 and 202 are spaced apart sufficiently and the first and second lifting members 210 and 212 are extendable sufficiently to provide an undercarriage access opening 460 to permit a mechanic to access the undercarriage of the vehicle. In other words, the support frame connector 230, the first and second support frames 200 and 202, and the first and second lifting members 210 and 212 are dimensioned to frame an undercarriage access space sufficient to provide the mechanic with access to the vehicle undercarriage when the first and second lifting members are extended (i.e., raised). When in their locked position (e.g., Figs. 2, 3,

-39-and 21B), the first and second lock assemblies 310 and 312 occupy an insubstantial amount of the access space 462 between the first and second structural frames, such that the mechanic has substantially unimpeded access to an area underneath 464 the vehicle. However, when the first and second lock assemblies are in their unlocked position (e.g., Figs. 20A and 21A), it can be seen that mechanic access to the undercarriage area 464 is impeded as a substantial portion of the at least one lock mounted on the first and second support frames is disposed across the space therebetween. Designing the lock assemblies to block access to the undercarriage of a vehicle being lifted until the lock assemblies have fully locked provides not only a visual indication of when it is safe for a mechanic to go underneath the vehicle being lifted, but also provides a physical impediment to going underneath the vehicle when it is unsafe to do so. While the above description pertains to only the first lifting apparatus 100, it will be appreciated that the same principles apply to the second lifting apparatus 150 due to its similar structure.
For example, an embodiment designed to lift a D8 dozer may have a support frame connector (230 in Fig. 13 or 232 in Fig. 14) that is about 2.3 feet long along its longitudinal axis, such that the left and right support frames are spaced apart by approximately this amount. In this embodiment, when the front lifting assembly is fully extended, about 3 feet of vertical clearance is provided for mechanic access between the top of the front support frame connector and the bottom of the D8 dozer undercarriage. When the rear lifting assembly is fully extended, about 2.2 feet of vertical clearance is provided for mechanic access between the top of the rear support frame connector and the D8 undercarriage. When the two locking assemblies of a lifting apparatus (100 or 150) are caused to lock, the right and left locks and lock couplers retreat apart as their respective locks (e.g., pins) are embedded in corresponding receptacles (i.e., complementary-shaped openings) of the support frame and/or lifting member, thus providing access to the undercarriage from the front and rear ends of the vehicle. The tips of the

-40-respective locks, which may optionally be colour-coded, may protrude from the outer edge of the lifting apparatuses (e.g., 430, 432, 434, 436), where they act us a visual indicator that it is safe to service the vehicle. While in this position, the lock couplers (360 and 362) continue to protrude to a limited extent to occupy some space between the left and right support frames 200 and 202 even when the locks have been fully inserted, however, this does not substantially obstruct mechanic access, permitting mechanics to go underneath the dozer to perform roller change outs and other repairs after it is lifted. In contrast, when the two locking assemblies 300 and 302 are actuated to move into an unlocked position, the respective left and right hand side locks extend horizontally in the centre section of the front and rear lifting assemblies and overlap to span substantially the entire width of the space between the left and right support frames 200 and 202 (e.g., see Fig. 21A), thereby interfering with mechanic access through the intermediate access space between the left and right support frames of the lifting apparatus. Omitting or removing the optional protective shroud 259 provides a larger mechanic access opening.
In this embodiment, the support frame connector (230 in Fig. 13 or 232 in Fig.
14) includes lifting receptacles 470, 472, 474, 476, adapted to be engaged by a forklift to facilitate the forklift lifting and moving or repositioning each vehicle lifting assembly. The lifting receptacles may also be designed to be compatible with a pallet truck. In one embodiment, the lifting receptacles may be about 4 inches tall by about 8 inches wide. Advantageously, the support frame connector (e.g., 230) not only enhances the stability of the lifting assemblies 120 and 130 connected thereto, but it also facilitates transportation of the first and second vehicle lifting assemblies, and provides a predetermined spacing between the first and second vehicle lifting assemblies that is suitable for engagement of the lifting assemblies with matching lifting surfaces on the vehicle to be lifted, thus saving time in setting up the system. Furthermore, as will be described below, the support frame

-41-connector may provide a conduit for passing hydraulic and electrical connections between the first and second vehicle lifting assemblies, thereby reducing the overall number of external connections required by the overall lifting apparatus.
The first and second lock assemblies 300 and 302 may include at least respective first and second sensors (e.g., 400 and 404) operable to detect locking engagement of the first and second locks 310 and 312, respectively, for use in disabling the operation of the first and second hydraulic cylinders 640 and 642 until the first and second locks are disengaged into the unlocked position. In this embodiment, the sensors include limit switches, but in other embodiments other provisions for detection of the state of the lock could be used such as optical or electronic sensors (e.g., analog or digital position sensors), for example.
In this embodiment, limit switches (e.g., 400, 402, 404, 406 and 630, 632, 636, 638) in the first and second lifting apparatuses are connected to the control unit 186 of the hydraulic power system 180. As shown in Figures 6 and 16A, each limit switch has an extended contact portion which extends into a receptacle (e.g., a groove 492) of a locking pin 340 when the pin is retracted. When the pin 340 begins to be inserted even slightly, the extended contact portion of the limit switch is pushed in as it no longer sits in the pin groove 492, thus breaking an electrical circuit within the limit switch. When the limit switch once again is aligned with the groove 492 in the pin 340, the limit switch again provides a continuous electrical path. In response to the locking pins being moved towards a locked position, the limit switches in this embodiment break a series electrical circuit, thus causing the control unit to disable the lift cylinders from lowering to prevent the locking pins from getting damaged. An exemplary control circuit is shown in Figure 23, although it will be appreciated that alternative control schemes could

-42-accomplish the same function of disabling the lift cylinders of a lifting system when any of the lift member locks are not in a fully unlocked state.
Referring to Figure 23, an embodiment of a simple limit switch based hydraulic safety circuit is shown generally at 700. The circuit 700 includes an electrical power source 702, a lift cylinder disable controller 704, both of which are electrically connected in series to limit switches 706 and 708 on the first and second lifting assemblies, respectively, of a front vehicle lifting apparatus (710 or 150), and to limit switches 712 and 714 mounted respectively on the first and second lifting assemblies of a rear vehicle lifting apparatus (720 or 100). The first and second lifting apparatuses 710 and 720 include electrical connectors 716 and 718, respectively, for connecting the limit switches to the electrical power source 702 and the hoist disable controller 704. The limit switches are mounted to interface with a limit switch receptacle such as a groove on respective locking pins on the first and second lifting assemblies.
When the locking pins are fully withdrawn, the limit switches are able to extend into the respective grooves of the locking pins, thereby closing a contact of the limit switch. Since all of the limit switches 706, 708, 712, are in series, if all of the locking pins are fully unlocked (i.e., retracted), a continuous circuit is formed which is detected by the lift cylinder disable controller 704 as an indication that it is safe for lifting cylinders to be either advanced or retracted. In this case, the controller 704 permits the lift cylinders to function normally. However, if at least one locking pin is not in a fully unlocked state, then that limit switch breaks the continuity of the series electrical circuit. A break in the continuity of the series circuit is detected by the lift cylinder disable controller 704, which in response disables the functionality of advancing or retracting the hydraulic lift cylinders. The safety circuit 700 reduces the risk that the lift cylinders will be lowered by accident while the lift system is locked.

-43-The limit switch may be mounted on a mounting plate, such as a 3/8 inch plate, (shown in Figure 5A with mounting holes but no limit switch mounted).
Figure 6 illustrates in dotted outline how two limit switches may be mounted to interface with two respective locking pins. Alternatively, only one limit switch may be mounted, or more than two limit switches may be mounted at various locations of the lifting apparatus. For example, in some embodiments, limit switches may be used to indicate if the pins are engaged 100% and/or to detect whether or not the lift cylinders have been fully raised or lowered.
Referring to Figure 24, an embodiment of a control circuit for controlling an exemplary hydraulic system associated with the first and second lifting apparatuses 100 and 150, is shown generally at 800. The electrical control circuit 800 includes an electrical power supply 802 operable to power a three phase motor 804 for driving a hydraulic pump 806. The power supply 802 is connected to a transformer 808 which provides electrical power at a lower voltage to a control circuit shown generally at 810. In this embodiment, the power supply is 460VAC and the transformer 808 produces a stepped down voltage of 120VAC. The motor 804 is disconnected from the power supply 802 until a user presses a start switch 812, thereby activating a main contactor 814. The contactor 814 is associated with a set of associated contacts 816 which are closed in response to the contactor being activated, to supply power to the motor 804. The circuit 810 includes an emergency stop switch 818 operable to cut off power to the contactor 814, thereby causing the associated contacts 816 to become an open circuit to disconnect and shut off the motor 804.
The circuit 810 further includes a three-way cylinder selection switch 820 operable to be switched between three positions, namely, a first position in which a hoist relay (i.e., lifting cylinder relay) 822 is powered up, a second intermediate "off' position, and a third position in which a pin relay 824 is powered up. In the "off' position, neither relay (822 or 824) is powered up.

-44-The switch can toggle from the "off' position to either the first position or the third position, but cannot toggle directly between the first and third positions.
The hoist relay 822 operates a set of associated contacts, namely, contacts 834 and 840. The hoist relay 822 is operable to cause the set of associated contacts, namely, contacts 834 and 840, to close when the hoist relay is powered up. The contacts 834 and 840 open by default when no power is supplied to the hoist relay 822. In a similar manner, the locking pins relay controls a set of associated contacts, namely, contacts 836 and 838.
The circuit 810 further includes a direction control switch 830 for controlling the direction in which an active set of hydraulic cylinders is moving. The direction control switch 830 has a first (advance) position, an intermediate second (hold) position, and a third (retract) position, and is biased toward the hold position. In the advance position, the direction control switch 830 causes power to be supplied on line 832, whereas in the retract position, the direction control switch causes power to be supplied on line 834. If the user releases the switch 830, it automatically moves to its intermediate position, associated with holding the present position of the active cylinders, and in this position, neither line 832 nor line 834 are supplied any power.
The cylinder select switch 820 and the cylinder direction switch 830 cooperate to configure and reconfigure directional valves 842 and 844 and are operable to cause advancement or retract the user-selected set of cylinders, in accordance with the respective positions of the switches 820 and 830. When the cylinder selection switch 820 is in the off position or when the cylinder direction switch 830 is in its neutral position, the directional valves 842 and 844 are configured to circulate hydraulic fluid back to the reservoir 188 thus causing the respective cylinders to hold their current position. When the cylinder selection switch 820 is in the first position (i.e., set to activate the hoist relay 822), and the direction control switch 830 is in the advance position, power is supplied through the switch 830 and the hoist advance

-45-contact 834 to configure the hoist directional valve 844 to advance the lift cylinders. When the direction control switch 830 is in the retract position, power is supplied through the switch 830 and the hoist retract contact 840 to configure the hoist directional valve 844 to retract the lift cylinders. In a similar manner, when the cylinder selection switch 820 is in the third position (i.e., set to activate the pins relay 824), the direction control switch 830 is operable to configure the pins directional valve 824 to either advance or retract the locking pin cylinders depending on whether the switch 830 is in the advance or retract position. When the pins relay 824 is energized, this allows the switch 830 to selectively supply power through either the pins advance contact 836 or the pins retract contact 838, in response to the direction control 830 being in its advance or retract position, respectively. Depending on whether current is flowing through the pins advanced contact 836 or the pins retract contact 838, the directional valve 842 directs hydraulic fluid to either advance or retract the pin cylinders.
As will be observed, the circuit 810 is designed to prevent the lifting cylinders and the locking pin cylinders from operating simultaneously. As a further safety feature, the hoist disable controller 704 is operable to disable the lifting cylinders in response to signals received from sensors indicating that at least one locking pin is not fully unlocked. In effect, the controller 704 disables the lift cylinders while the lifting system is locked. A main manifold controller is further operable to control hydraulic fluid flow in the various circuits.
The support frame may include at least one bottom opening, for example, opening 278 in Figure 10. The support frame bottom opening 278 allows hydraulic plumbing into the "box" surrounding the hydraulic lift cylinders to supply the lift cylinders with hydraulic fluid. The support frame opening 278 also allows hydraulic fluid to escape should there be a leak (e.g., due to a lift cylinder malfunction), alerting the mechanic to shut down the lifting system.

-46-A system using the lifting apparatuses of the present invention may further include a hydraulic power system including a pump cart with at least one hydraulic power source operable to pressurize hydraulic fluid circuits in fluid communication with the first vehicle lifting assembly and a second vehicle lifting assembly, respectively, wherein the first and second vehicle lifting assemblies are configured for use in lifting the front and rear ends, respectively, of a certain type of heavy vehicle or particular equipment. The pump cart may include a set of wheels, a chassis or frame mounted on the set of wheels, and at least one hydraulic power source mounted on the chassis or frame. Other hydraulic equipment such as valves, gauges and hydraulic controls (e.g., flow control valves, a main contactor for initiating hydraulic power, and/or an emergency stop or shutoff for disabling hydraulic power) may be mounted directly or indirectly on the pump cart frame.
The hydraulic power system may include a hydraulic pump having at least one piston. In one embodiment, the pump cart provides independent hydraulic power sources to each of the hydraulic lifting cylinders in the overall system.
For example, the pump cart may have a hydraulic pump with four pistons operated by one or more motors, and operable to independently supply hydraulic power to the four hydraulic lift cylinders, respectively. As one example, the pump cart may use a DynexTM split-flow multiple piston pump, which uses a checkball design to allow the output of each piston to be used separately to provide relatively even flow to facilitate synchronous movement of the hydraulic lift cylinders without using a flow divider. Information about DynexTM multiple outlet hydraulic pumps may be found at the DynexTM
website (www.dynexhydraulics.com/split.htm), the disclosure of which is incorporated herein by reference. As an alternative to using a single pump with multiple outlets, it may be possible in some embodiments to use a single pump cart with a single piston pump, if the flow from the single piston pump is multiplexed among the four lifting cylinders so as to provide a relatively synchronized lifting motion among the four lifting cylinders. As a further

-47-possibility, providing system pressure is not too high, flow dividers may be used to facilitate evenly splitting hydraulic pressure of the one pump between the four lifting cylinders. In one embodiment, the normal working pressure may be on the order of about 6,000 to 6,500 psi, although the system is rated for a maximum pressures of 10,000 psi. However, at pressures above about 4,000 to 7,000 psi, many flow dividers may not work reliably. As a further possibility, multiple pump carts may be used to drive the lift cylinders, however, the lifting operation of the multiple pump carts must be coordinated.
In one embodiment of a lifting system having double acting cylinders, the pump cart further includes:
(a) first and second hydraulic fluid connector pairs for powering the first and second hydraulic lift cylinders of the first vehicle lifting system, respectively;
(b) a third hydraulic fluid connector pair for powering the first and second lock assemblies of the first vehicle lifting system, respectively;
(c) fourth and fifth hydraulic fluid connector pairs for powering first and second hydraulic lift cylinders of the second vehicle lifting system, respectively; and (d) a sixth hydraulic fluid connector pair for powering first and second hydraulic lock cylinders of the second vehicle lifting system, respectively.
With regard to the third hydraulic fluid connector pair for powering the first and second lock assemblies of the first vehicle lifting system, respectively, the connector pair includes a first lock cylinder inlet and a first lock cylinder outlet.
The first lock cylinder inlet receives hydraulic fluid for all four hydraulic cylinders associated with the first and second lock assemblies, and the first lock cylinder outlet returns hydraulic fluid to the reservoir. The sixth hydraulic fluid connector pair operates analogously. In this embodiment, hydraulic plumbing is passed through the crosswise support frame connector

-48-connecting the two support frames to allow hydraulic fluid to activate the pin cylinder which is on the side opposite the hydraulic pin external coupling. In other embodiments, the pair of linear actuators which drive a lock assembly need not share a hydraulic power connection with the pair of linear actuators on the counterpart lock assembly on the neighbouring lifting assembly, nor even share a hydraulic power connection with each other; rather, independent hydraulic connections could be provided albeit at the expense of having to use additional ports and hoses. On the other hand, implementing the hydraulic cylinders of the lock assemblies as single-acting cylinders with a spring return could reduce the number of hydraulic connections to one port.
In an embodiment with double-acting cylinders, the pump cart further includes six sets of hydraulic hose pairs (12 hoses in total) operable to be connected to respective hydraulic fluid connector pairs. The six sets of hydraulic hose pairs may be arranged into first and second hose bundles with corresponding manifold-type plugs, each bundle including three sets of hydraulic hose pairs, corresponding to the first and second vehicle lifting systems, respectively.
In an alternative embodiment where the lifting system uses single-acting cylinders, the pump cart may include at least one hydraulic fluid connector connected to each vehicle lifting system, for example, the pump cart may include one hydraulic fluid connector for each lifting cylinder of the first and second vehicle lifting systems. In addition, the pump cart may include at least one hydraulic fluid connector for powering at least one lock of the first vehicle lifting system and at least one hydraulic fluid connector for powering at least one lock of the second vehicle lifting system. In other embodiments, the lifting system could use a combination of double-acting cylinders and single-acting cylinders, for example, single-acting cylinders (with or without a spring return) for lifting but double-acting cylinders for the lock mechanisms. Depending on the number and type of hydraulic cylinders used in the system, the number and type of hydraulic hoses would be likewise adjusted appropriately.

-49-The first and second vehicle lifting systems may have quick connectors or multi-coupling quick connectors, operable to quickly connect to complementary connectors on the hoses, or to manifold-type plugs on the first and second hose bundles described above. Multi-coupling connectors may include multi-coupling plates produced by StucchiTM USA, for example, and may be configured to connect to the manifold-type plugs in only one orientation. Furthermore, the multi-coupling plates may be mounted on the lifting assemblies in a convenient location and in a convenient orientation such as at an oblique angle to facilitate fast connections.
In one embodiment, a plurality of single hydraulic quick connectors may be used as illustrated in Figure 22A. Referring to Figure 22A, a top plan view of one embodiment of a lifting apparatus is shown generally at 600. The apparatus includes first and second lifting assemblies (610 and 620) connected together by a tubular support frame connector 615. In this embodiment, the first lifting assembly 610 includes first and second quick connectors 602 and 604. Connector 602 includes hydraulic ports 616 and 618 for providing hydraulic power to a lift cylinder 640 of the first lifting assembly 610. The second lifting assembly 620 includes a similar quick connector 606 aggregating two hydraulic ports 622 and 624 which can be connected simultaneously to provide hydraulic power to a second hydraulic lift cylinder 642 associated with a second lifting assembly 620. Additional hydraulic components such as load holding valves (e.g., 649) may be connected between the quick connectors and the lifting cylinders 640 and 642.
In this embodiment, the second lifting assembly 620 includes an electrical connector 608 which provides at least one set of electrical ports 626 for transmitting sensor signals to a remote control or pump cart. In this embodiment, the sensor signals include one or more signals from limit

-50-switches 630, 632, 636, and 638, mounted so as to physically interface with and measure the position of locking pins on the first and second lifting assemblies 610 and 620. In one embodiment, a sensor signal could be as simple as a continuous voltage indicating a particular status of at least one component on the device, as opposed to an open circuit or different voltage which would represent a different status. In another embodiment, the sensor signal could be a digital signal encoded with information about the state or status of one or more components.
The first lifting assembly 610 further includes hydraulic connector 604.
Hydraulic connector 604 provides hydraulic inlet and outlet ports 612 and 614 which are connected to the linear hydraulic actuators 641, 643, 645, and 647.
The hydraulic actuators 641, 643, 645, and 647 are operable to advance or retract locking pins mounted on the first and second lifting assemblies.
Because in this embodiment, a single connector 604 on the first lifting assembly 610 is used to supply power to two linear hydraulic actuators 645 and 647 on the second lifting assembly 620, a hydraulic conduit 644 hidden within the connector 615 is used to pass hydraulic fluid from the connector 604 on the first lifting assembly to the cylinders 645 and 647 on the second lifting assembly. Similarly, because the electrical connector 608 is provided only on the second lifting assembly 620 whereas there are sensors (e.g., limit switches 630 and 632) on the first lifting assembly 610, a bundle of electrical conductors 634 is passed through the connector 615 from the connector 608 on the second lifting assembly 620 to the sensors on the first lifting assembly 610. A suitable hydraulic connector for making dual hydraulic connections quickly (e.g., 602, 604, and 606) is the HP series connector produced by StucchiTM USA. In another embodiment, the hydraulic actuators 645 and 647, rather than sharing port 604, could be powered by an independent hydraulic port, which could be mounted on the second lifting assembly 620, thereby making the hidden hydraulic conduit 644 unnecessary. Similarly, the sensors

-51-mounted on the left and right lifting assemblies could have separate connectors mounted on the respective lifting assemblies thus making the conductor path 634 unnecessary.
In an alternative embodiment, a multi-coupling plate quick connector may be installed to allow easy simultaneous connection of all six hydraulic hoses (and more, if required). Preferably the multi-coupling connection is located on one side of the vehicle lifting assembly as shown in Figure 22B, and all the hydraulic circuits needed for the other side are plumbed through the support frame connector 615. In some embodiments, at least some electrical quick connectors may be combined in a multi-coupling connector bearing a plurality of hydraulic connections. Such an alternative embodiment of the lifting apparatus 650 will now be described with reference to Figure 22B.
In this alternative embodiment, all the hydraulic connections are consolidated at a single central location 660 which utilizes a multi-coupling plate connector 670 configured to allow quick connection of a plurality of hydraulic hoses.
The multi-coupling connector 670 includes a plurality of hydraulic ports such as ports 672 and 674, for example. In this embodiment, the hose pair that feeds the lift cylinder 640 of the first lifting assembly 610, the hose pair that feeds the second hydraulic lift cylinder 642 of the second lifting assembly 620, and the hose pair that feeds the four lock cylinders (641, 643, 645, and 647) on the first and second lifting assemblies, are all consolidated in the multi-coupling connector 670. Because this embodiment consolidates all hydraulic ports in a single connector on one side of the lifting apparatus 650, it is necessary to run additional hydraulic conduits 646 to provide hydraulic power to the lift cylinder 642 on the second lifting assembly 620 through the tubular connector 615 connecting the first and second lifting assemblies 610 and 620.
In addition, it is possible to provide one or more electrical connectors 676, either as part of the connector 670 or separate from it in a separate electrical

-52-connector. The number of electrical conductors that are connected will depend on the number of sensors provided on the overall lifting apparatus.
In this embodiment, the pump cart may include a four-piston hydraulic pump and hydraulic circuitry rated for up to about 10,000 psi for providing controlled hydraulic power to each of the hydraulic lift cylinders in the first and second vehicle lifting systems. The use of quick connectors on the pump cart and/or lifting system, capable of connecting a plurality of hydraulic ports and/or electrical circuits at one time, can save considerable time when setting up the lifting system for operation. Also, the pump cart may include one or more brackets or hose reels for holding and storing bundles of hydraulic hoses.
The pump cart further includes or is connected to a remote control having controls operable to cause selective hydraulic activation of any combination of the hydraulic connectors. The remote control may include a wired pendant or a pendant having a wireless connection with the pump cart. The remote control is operably configured to receive signals from sensors or limit switches on the first and second vehicle lifting systems, and the vehicle assembly is operably configured to disable hydraulic activation of each of the lifting cylinders connected to the pump cart in response to the sensors or limit switches being actuated, until the sensors or limit switches are deactuated.
The remote control may include an emergency stop button operably configured to cause the hydraulic lift cylinders to cease their movement.
If a wired pendant is used as the remote control, it is preferable to use a wire length of about 35 feet or more to permit the mechanic who operates the wired pendant to stand safely clear of the dozer perimeter while also permitting the mechanic to move around the dozer to better observe the lifting process. A wireless pendant provides even greater flexibility in being able to control the entire vehicle lifting system from a centralized location while moving around the vehicle, if needed.

-53-Operation In operation, the following sequence may be followed to replace the conventional dozer lifting procedures. First, the front blade of the dozer is lifted and placed on fixed stands. The front blade is then lowered and the dozer can be turned off. The first and second vehicle lifting apparatuses are then wheeled directly under the dozer, and positioned such that the vehicle engaging surfaces of the lifting apparatuses correspond to the designated lifting points on the frame of the dozer. The vehicle engaging surfaces are designed to conform to the shape of the corresponding lifting point on the dozer to avoid point loading. The vehicle lifting apparatuses will always be placed in the same position on a flat surface to ensure a maximum contact surface between the apparatus and the dozer. For the front of a Caterpillar dozer, this contact area is located just behind the curved surface of the frame.
The lifting point at the rear may be located on the pivot shaft housing.
In this embodiment, four hydraulic cylinders are preferably connected to a single pump cart. A wired or wireless remote control pendant is used by the mechanic to control the pump cart. As the pump cart supplies hydraulic fluid in response to the mechanic's input, the four hydraulic cylinders are operable to lift the unit evenly (front and rear) to ensure a flat contact surface (i.e., avoid point loading) and to enhance stability (e.g., side loading). Once the unit is lifted, the same pump cart is used to activate the hydraulic locking pins.
The locking pins are inserted through the lift system frame to prevent the cylinders from dropping due to a possible loss of hydraulic pressure. In effect, the lift system is converted to a fixed stand. When lowering the dozer, the process is repeated in reverse order. Furthermore, the cylinders are connected to hydraulic load holding valves that do not allow any fluid to escape when the hydraulic hoses are disconnected from the pump cart. In addition, the load holding valves prevent the jacks from lowering suddenly in case of an unexpected leak or pressure loss due to a hydraulic malfunction.

-54-For example, in one embodiment, using the remote control, the user may set a cylinder selection switch (having positions corresponding to HOIST, OFF
and PINS) to the HOIST position, and then operate a cylinder direction switch (having positions corresponding to ADVANCE, HOLD, and RETRACT) to the ADVANCE position, thus causing the lift cylinders to lift a vehicle until the lift cylinders are fully extended. The fact that the lift cylinders are fully extended may be discerned either visually, by the fact that the pump cart motor changes its pitch, in response to a visual indicator on the remote control (e.g., pendant) based on a signal received from a sensor adapted to measure the position of the lift cylinders, or by any other suitable method.
At this point, the user may put the cylinder selection switch into the PINS
position, thus selecting the cylinders associated with the locking pins. The user may then place the cylinder direction switch in its ADVANCE position to cause the locking pins to advance. As a safety feature, the second switch may be biased to return to the middle HOLD position, such that the lift cylinders are advanced or retracted only while the user holds the second switch in the ADVANCE or RETRACT positions. When the user lets go of the cylinder direction switch, lift cylinder movement is suspended. The cylinder selection switch is placed in the OFF position while the vehicle is being serviced.
The vehicle can be lowered by performing the above operations in reverse.
The cylinder selection switch is placed into the PINS position, and the cylinder direction switch is placed into the RETRACT position until the lifting apparatuses are fully unlocked. Then the cylinder selection switch is placed into the HOIST position, and the cylinder direction switch is placed into the RETRACT position until the vehicle is fully lowered.

-55-In this method, it is evident that mechanics are not required to be within the vicinity of an active dozer while it is being raised. This eliminates numerous safety risks should the dozer hydraulics ever fail.
Furthermore, it is unnecessary to have an operator running the dozer simply to adjust the height of the dozer, nor is there any need for time-consuming communication between the dozer operator and the mechanics below. The structural design of the lifting system avoids creating point loads and interferes with side to side movements of the dozer, even when heavy parts are being removed from the undercarriage. Consequently, this approach proves to be safer and faster than many known approaches to lifting a heavy vehicle such as a dozer.
In order to support the safe and reliable operation of the vehicle lifting system, the components of the system are periodically inspected for wear and tear.
Certain key components, such as the hydraulically activated pins, load holding valves, quick connections and lift cylinder inserts may be monitored to project long term wear effects and to establish preventative maintenance requirements and intervals.
In addition to the exemplary embodiments described herein and the many variants thereto, numerous other embodiments of the invention may fall within the scope of the accompanying claims.
It will be appreciated that the dimensions and specifications of the described vehicle lifting systems can be readily adapted to lift various models of other dozers produced by Caterpillar (in addition to the D8, D10, and D11 models), or to lift heavy vehicles or other equipment produced by Caterpillar or another manufacturer by making allowances for differences in dimensions, and load, height and interface requirements.

-56-The approximate minimum and maximum heights required for several exemplary lifting systems designed for several particular models of Caterpillar dozer are described in millimeters (mm) in Table 1 below.
Table 1. Exemplary Cat Dozer Lifting System Height Requirements Cat Dozer Front Rear Front Rear D8 718 (min) 477 (min) 1012 (max) 809 (max) D10 866 (min) 536 (min) 1201 (max) 883 (max) D11 1005 (min) 527 (min) 1391 (max) 909 (max) The minimum height refers to about how low the lifting systems need to be to fit under a dozer with a worn undercarriage. The maximum height refers to about how high the lifting systems should lift in order to facilitate performing undercarriage work. Note that the minimum height does not take into account the material (i.e., metal plates) at the top and bottom of the lifting systems, nor the clearance from the floor due to the spring loaded wheel assemblies.
While specific embodiments of the invention have been described and illustrated, such embodiments should be considered illustrative of the invention only and not as limiting the invention as construed in accordance with the accompanying claims.

Claims

What is claimed is:

1. A vehicle lifting apparatus, comprising:
(a) first and second hydraulic lift cylinders comprising respective first and second hydraulic lift cylinder shafts operably configured to extend along respective first and second lifting axes, the first and second hydraulic lift cylinders each having a respective first and second end;
(b) first and second lifting members having respective first and second vehicle engaging ends for engaging corresponding first and second portions of the vehicle, the first and second lifting members being connected to the respective first ends of the first and second hydraulic lift cylinders, respectively;
(c) first and second support frames connected to the respective second ends of the first and second hydraulic lift cylinders, respectively, and comprising respective first and second guide channels to guide telescoping movement of the first and second lifting members along the first and second lifting axes, respectively;
(d) a first support frame connector fixedly connecting the first and second support frames in generally parallel, spaced apart relation such that the first and second lifting axes are generally parallel to each other; and (e) first and second lock assemblies, mounted on the first and second support frames, respectively, each lock assembly comprising at least one lock and at least one lock actuator that are powered and controlled remote from the lock assembly and operably configured to selectively cause the at least one lock to move between an unlocked position in which the associated lifting member can extend away from or retract towards the associated support frame, and a locked position in which the at least one lock interferes with retraction of the associated lifting member toward the associated support frame.

2. The apparatus of claim 1 wherein the first lock assembly comprises a first pair of linear actuators mounted on opposite sides of the first support frame and a lock coupler coupling movement of the first pair of linear actuators to the at least one lock of the first lock assembly.

3. The apparatus of claim 2 wherein the at least one lock comprises a pair of pins operably configured to be placed into the locked position by insertion into respective openings of the first support frame on opposite sides of the first hydraulic lift cylinder shaft in response to movement of the first pair of linear actuators in a first, locking direction.

4. The apparatus of claim 1 wherein the at least one lock actuator comprises a linear actuator having an axis of movement perpendicular to the first and second lifting axes.

5. The apparatus of claim 4 wherein the lock actuators mounted on the first and second support frames each have an axis of movement parallel to a longitudinal axis of the support frame connector.

6. The apparatus of claim 5 wherein the lock actuators mounted on the first and second support frames each have an axis of movement that is disposed in a common single plane parallel to the longitudinal axis of the support frame connector.

7. The apparatus of claim 1 further comprising a lock coupler coupling the at least one lock actuator with the at least one lock.

8. The apparatus of claim 7 wherein the lock coupler comprises a rod and the at least one lock comprises at least one pin threaded onto the rod.

9. The apparatus of claim 1 wherein the first and second support frames are spaced apart sufficiently and the first and second extendable lifting members are extendable sufficiently to provide an undercarriage access opening to permit mechanic access to the undercarriage of the vehicle through the undercarriage access opening.

10. The apparatus of claim 1:
(a) wherein the support frame connector, and first and second support frames, and the first and second lifting members are dimensioned to provide an undercarriage access space sufficient to provide a mechanic with access to the vehicle undercarriage when the first and second lifting members are extended;
(b) wherein in their locked position, the first and second lock assemblies occupy an insubstantial amount of the undercarriage access space such that mechanic access to the undercarriage through the undercarriage access space is substantially unimpeded; and (c) wherein when in their unlocked position, the first and second lock assemblies occupy a substantial portion of the access space such that mechanic access to the undercarriage through the undercarriage access space is impeded.

11. The apparatus of claim 1 wherein the first and second lock assemblies include respective first and second sensors operable to detect locking engagement of the first and second locks, respectively, for use in disabling the operation of the first and second hydraulic cylinders until the first and second locks are disengaged to the unlocked position.

12. The apparatus of claim 1 wherein the respective lock actuators of the first and second lock assemblies include respective first and second hydraulic lock cylinders.

13. The apparatus of claim 1 wherein the first locking assembly comprises a first lock guide, mounted on the first support frame, for guiding the associated lock as it moves between the locked position and the unlocked position, wherein at least a portion of the associated lock is disposed in the first lock guide.

14. The apparatus of claim 1 wherein the first and second hydraulic lift cylinders are in hydraulic communication with respective load holding valves operably configured to prevent the first and second hydraulic lift cylinders from suddenly lowering in the case of hydraulic pressure loss.

15. The apparatus of claim 1 wherein extension of the first and second hydraulic lift cylinder shafts causes the first and second lifting members to extend away from the first and second support frames, respectively, and retraction of the first and second hydraulic lift cylinder shafts causes the first and second lifting members to retract towards the first and second support frames, respectively, and wherein the first and second support frames are configured to facilitate sliding engagement with the first and second lifting members, respectively, during the extension and retraction thereof.

16. The apparatus of claim 1 wherein the support frame connector comprises lifting receptacles to facilitate lifting of the vehicle lifting apparatus.

17. The apparatus of claim 1 further comprising first and second wheel assemblies mounted on the first and second support frames, respectively, each of the first and second wheel assemblies having a spring-loaded suspension and at least one lockable wheel.

18. The apparatus of claim 1 further comprising a pump cart operable to pressurize first and second hydraulic fluid circuits in fluid communication with the first vehicle lifting assembly and a second vehicle lifting assembly, respectively, wherein the first and second vehicle lifting assemblies are configured for use in lifting the front and rear ends, respectively, of the vehicle, the pump cart comprising:
(a) first and second hydraulic fluid conduit pairs for powering the first and second hydraulic lift cylinders of the first vehicle lifting system, respectively;
(b) a third hydraulic fluid conduit pair for powering the first and second lock assemblies of the first vehicle lifting system, respectively;
(c) fourth and fifth hydraulic fluid conduit pairs for powering first and second hydraulic lift cylinders of the second vehicle lifting system, respectively; and (d) a sixth hydraulic fluid conduit pair for powering first and second hydraulic lock cylinders of the second vehicle lifting system, respectively.

19. The apparatus of claim 18 wherein the pump cart further comprises six sets of hydraulic hose pairs operable to be connected to the respective hydraulic fluid conduit pairs.

20. The apparatus of claim 18 wherein the six sets of hydraulic hose pairs are arranged into first and second manifold-type plugs, each comprising three sets of hydraulic hose pairs, corresponding to the first and second vehicle lifting systems, respectively.

21. The apparatus of claim 19 wherein the pump cart comprises a four-piston hydraulic pump for providing hydraulic pressure to each of the hydraulic lift cylinders in the first and second vehicle lifting systems.

22. The apparatus of claim 1 further comprising a pump cart and a remote control operably connected to the pump cart, the remote control having at least one user control operable to cause selective hydraulic activation of at least one conduit in fluid communication with the pump cart.

23. The apparatus of claim 22 wherein the remote control comprises a wired pendant electrically connected to the pump cart.

24. The apparatus of claim 22 wherein the remote control comprises a wireless pendant having a wireless connection with the pump cart.

25. The apparatus of claim 22 wherein, in response to receiving signals from lock sensors on the first and second vehicle lifting assemblies, each vehicle lifting assembly is operably configured to disable hydraulic activation of its lifting cylinders, and the remote control is operably configured to indicate that the lifting cylinders have been disabled.

26. The apparatus of claim 25 wherein the remote control includes an emergency stop button operably configured to cause the lift cylinders to cease movement.

27. The apparatus of claim 25 wherein the pump cart comprises brackets for holding hydraulic hoses.

28. The apparatus of claim 1 wherein the first lock assembly is operable to cause at least one lock to pass substantially through the first support frame from a first side of the first support frame to a second side of the first support frame, the first and second sides enclosing an intermediate space within the first support frame.

29. The apparatus of claim 1 wherein the at least one lock of the first lock assembly is operably configured to interlock the telescoping movement of the first lifting member with respect to the first support frame.

30. The apparatus of claim 29 wherein the at least one lock of the first lock assembly intersects the first lifting member at at least two points and also intersects the first support frame at at least two points.

31. The apparatus of claim 1 wherein the first lock assembly is operably configured to interfere with sliding movement of the first support frame relative to the first lifting member by causing first and second pins of the first lock assembly to intersect the first support frame and the first lifting member.

32. The apparatus of claim 31 wherein:
(a) the first and second pins are inserted respectively on first and second opposite sides of the first lifting axis;
(b) the first pin intersects the first support frame and the first lifting member on the first side of the first lifting axis; and (c) the second pin intersects the first support frame and the first lifting member on the second side of the first lifting axis.

33. The apparatus of claim 32 wherein:
(a) the first pin intersects the first support frame at a first and second location;
(b) the first pin intersects the first lifting member at a third and fourth location;
(c) the second pin intersects the first support frame at a fifth and sixth location;
(d) the second pin intersects the first lifting member at a seventh and eight location; and (e) the first, second, fifth, and sixth locations are proximate to the third, fourth, seventh and eighth locations, respectively.

34. The apparatus of claim 1 wherein the first lock assembly is operable to pull at least a portion of one lock of the first lock assembly away from an access area for accessing the underside of a vehicle, wherein the access area is located between the first and second support frames.

35. A method of lifting a vehicle, the method comprising:
(a) positioning a first lifting assembly underneath a first end of the vehicle, the first lifting assembly comprising:
(1) first and second support frames in sliding engagement with respective first and second lifting members;
(2) first and second lock assemblies mounted on the first and second support frames, respectively, and operable to selectively interfere with sliding movement of the support frame on which it is mounted, relative to its associated lifting member;
(3) first and second hydraulic lift cylinders connected to the first and second support frames, respectively, and also connected to the first and second lifting members, respectively, each lift cylinder being operable to cause telescoping movement of the corresponding lifting member with respect to the corresponding support frame;
(4) a support frame connector connecting the first and second support frames;
(b) positioning at least one lifting device underneath a second end of the vehicle;
(c) using a remote control, causing hydraulic power to be supplied to the first lifting assembly at the first end of the vehicle and the at least one lifting device at the second end of the vehicle, to cause the first and second ends of the vehicle to be lifted;
(d) using the remote control, causing the first and second lock assemblies to interfere with relative movement of the respective associated support frames and lifting members, to prevent the associated lifting members from retracting toward the respective associated support frames.

36. The method claim 35 further comprising using the remote control to also remotely activate a locking system on the at least one lifting device, wherein the locking system is operable to prevent lowering of the vehicle at the second end thereof.

37. A locking system for a vehicle lifting apparatus, the system comprising:
a support frame of the vehicle lifting apparatus, the support frame being configured to guide telescoping movement of a lifting member of the vehicle lifting apparatus in sliding engagement with the support frame along a lifting axis, the lifting member having a distal end for lifting a vehicle;
at least one lock mounted on the support frame, the at least one lock being operable to move between an unlocked position in which the lifting member can extend away from or retract towards the support frame, and a locked position in which the at least one lock interferes with retraction of the lifting member toward the support frame; and at least one lock actuator operably configured to selectively cause the at least one lock to move between the unlocked position and the locked position, wherein the at least one lock actuator is powered from a power supply at a remote location.

38. The system of claim 37 further comprising a pair of linear actuators mounted on opposite sides of the support frame, and a lock coupler coupling movement of the pair of linear actuators to the at least one lock.

39. The system of claim 38 wherein the lock coupler comprises a rod and the at least one lock comprises at least one pin threaded onto the rod.

40. The system of claim 38 wherein the at least one lock comprises a pair of locking pins operably configured to be placed into the locked position by being inserted into respective openings of the support frame on opposite sides of the lifting axis in response to movement of the pair of linear actuators in a first, locking direction.

41. The system of claim 37 wherein the at least one lock actuator has an axis of movement perpendicular to the lifting axis.

42. The system of claim 37 wherein the at least one lock actuator has an axis of movement parallel to a longitudinal axis of a support frame connector which connects the support frame with a spaced apart, second support frame configured to support telescoping movement of a corresponding second lifting member along a second lifting axis, parallel to the first lifting axis.

43. The system of claim 42 wherein the support frame, support frame connector, and second support frame, at least partially frame a vehicle access space for allowing mechanics access to the vehicle undercarriage, and wherein the at least one lock actuator is operable to withdraw at least a portion of the at least one lock from the vehicle access space.

44. The system of claim 37 further comprising at least one sensor operable to detect a current position of the at least one lock, and in response to detecting the current position of the at least one lock, to send a signal representative of the current position for use in disabling the operation of at least a portion of the associated vehicle lifting apparatus.

45. The system of claim 37 wherein the at least one lock actuator comprises a hydraulic cylinder.

46. The system of claim 37 further comprising at least one lock guide, mounted on the support frame, for guiding movement of the at least one lock as it moves between the locked position and the unlocked position.

47. The system of claim 37 wherein the at least one lock actuator is operable to cause the at least one lock to pass through the support frame from a first side of the support frame and to pass through the first support frame to a second side of the support frame, the first and second sides enclosing an intermediate space within the support frame.

48. The system of claim 37 wherein the at least one lock is configured to interfere with telescoping movement of the lifting member with respect to the support frame by intersecting both the support frame and lifting member.

49. The system of claim 37 further comprising first and second pins operable to be inserted into respective first and second openings on a first side of the support frame, when the first and second openings are aligned with respective third and fourth openings in the lifting member, to interfere with sliding relative movement of the support frame and lifting member.

50. The system of claim 49 wherein the first and second pins are operable to be inserted further into the first and second opening so as to pass through respective fifth and sixth openings in the lifting member and to protrude through respective seventh and eight openings on a second side of the support frame, opposite to the first side of the support frame, to interfere further with sliding relative movement of the support frame and lifting member.

51. The apparatus of claim 1 wherein the first and second lock assemblies comprise respective first and second lock assembly hydraulic cylinders which are both powered from a single hydraulic power connector on the apparatus.

52. The apparatus of claim 1 wherein the first and second lock assemblies and the first and second hydraulic lift cylinders are all powered by hydraulic power received from a single multi-coupling hydraulic connector.

53. The apparatus of claim 1 wherein the top surfaces of the first and second lifting members are operable to be raised from a first height to a second height, and wherein the third and fourth lifting members are operable to be raised from a third height to a fourth height, wherein the second height is substantially different than the fourth height.