FIELD OF THE INVENTION

This invention relates to a lift apparatus, in particular a lift apparatus for moving a lift car between two or more distinct positions.

BACKGROUND OF THE INVENTION

Conventional lift or elevator systems are driven by lifting mechanisms comprising either cables or a hydraulic piston. In both cases, the systems comprise a lift car mounted on a platform within a shaft. The lifting mechanism is also present within the shaft, alongside guide rails that prevent the car from rocking or deviating from its vertical path.

In the case of cable systems or traction lifts, a series of metal cables and pulleys connect the lift car to a motor that hoists the car up or down. Most traction lift systems have a control room above the shaft in which the motor and pulleys are housed, although in some smaller designs, they are located at the top of the shaft itself. The ropes are attached to the lift car and looped around a sheave or pulley, which is driven by the motor. The weight of the car is balanced by a counterweight located within the shaft and is guided by additional guide rails. The counterweight, along with various gears, helps to reduce the load on the motor. The lift car itself is very heavy and despite the gears and counterweight, a large powerful motor is still required to move the lift car. These types of lift system also comprises safety mechanisms in the form of governors and/or electromagnetic brakes. Governors ensure the lift car does not move too quickly by attaching an additional cable or rope that runs over a flywheel and attaches to the governor. If the safety rope moves too quickly, and/or there is a rapid change in acceleration (i.e. the car falling), pins in the mechanism fly outwards from the change in motion to engage a surrounding ratchet arrangement to stop the rope and therefore lift car from moving. Electromagnetic brakes prevent motion past certain predetermined locations, or brake the system if there is a loss of power.

Hydraulic lifts comprise a fluid reservoir and a piston or cylinder, powered by a pump. The pump is connected to a motor to raise and lower the car from below. The pump, motor and fluid reservoir are large systems and are placed in a space below the car at the base of the lift shaft. This type of lift is only used for short distances of travel (for example fewer than six stories) as the cylinder size is relative to the distance of travel, so high shafts would require a large piston. These systems are also fairly inefficient when compared to traction lifts as a large amount of energy is required to pump the cylinder full of fluid from the fluid reservoir when raising the car. Safety mechanisms in hydraulic lifts are normally overspeed valves and a manual slack/broken cable which can be attached to a switch to prevent operation of the lift.

In both types of systems, the presence of the guide rails (and ropes/counterweights) in the lift shaft limits the cross-sectional area of the lift car compared to that of the shaft. The presence of control rooms for the driving mechanisms means that the shaft must be made taller or have an additional space in order to accommodate them at either the top or bottom of the shaft (dependent on the type of lifting mechanism).

Thus, it would be desirable to provide a lift apparatus and system which addresses at least some of these issues.

SUMMARY OF THE INVENTION

Accordingly, in one aspect, this invention provides an elevator system comprising:

an elevator car;

a lift mechanism comprising:

an elongate support member located adjacent said elevator car and having a substantially vertical longitudinal axis;

a push drive mechanism comprising a flexible drive member maintained longitudinally around said support member and drive means

configured to drive said drive member relative to said support member about

an axis substantially orthogonal to said longitudinal axis; and a lifting member connected to the base of said elevator car wherein said lifting member is coupled to said drive means such that operation of said push-drive mechanism causes substantially vertical movement of said elevator car relative to said support member. In an exemplary embodiment, the drive member may comprise a chain or belt and, optionally, the drive means may be a motor. Operation of said drive means in a first direction may cause upward vertical movement of said elevator car relative to said support member and, operation of said drive means in a second, opposite direction may then cause downward relative movement of said elevator car relative to said support member. The lift mechanism may be located in one corner of an elevator shaft. Although it will be appreciated that one of the principal advantages of the present invention is the elimination, at least in some exemplary embodiments, of a formal shaft - as the guide rails of the prior art arrangements are entirely eliminated, an elevator shaft is not necessarily required.

The elevator car may have a substantially square or rectangular lateral cross- section with a portion of a corner thereof omitted to accommodate said support member adjacent thereto.

The drive member may comprise a continuous loop. The motor may be located within a recess at a lower end of a lift shaft or other space accommodating said system. The lifting member may be configured to push the elevator car upwards from below in response to the drive means driving the drive member in a first direction. Similarly, the lifting member may be configured to guide the elevator downwards in response to the drive means driving the drive member in a second direction. The lifting member may comprise a plate connected to the base of said elevator car. The lifting member or plate may comprise a security fork for providing a connection between the drive means and the elevator car. The lifting member or plate may also include one or more load cells for generating an electrical signal representative of a weight and/or force associated with said elevator car. The lifting member or plate may comprise a layer of anti-vibration material adjacent to the base of the elevator car.

The support member may comprise a plurality of substantially parallel vertical beams. The support member may comprise two pairs of vertical beams, and the drive member may extend lengthways between the first pair of beams, and lengthways between the second pair of beams. Each beam may comprise fixing points located at intervals along the length of the beam, and wherein brackets attach to the fixing points to separate the beams into pairs. The pairs of beams may be attached to each other by connecting members located at intervals along the length of each beam. At least one beam may be attached to a wall of a lift shaft (or other space accommodating the elevator system) via a fixing bracket.

The system may further comprise a plurality of sliding shoes attached to the base of the elevator car and a plurality of corresponding sliding shoes attached to the uppermost surface of the elevator car.

The lateral cross-section of the elevator car may be square in shape with one corner cut off at a substantially 45 degree angle. The lift mechanism may be located in the corner of a lift shaft (or other space accommodating the elevator system) adjacent to the corner of the elevator car cut off at a 45 degree angle.

The cross-sectional area of the elevator car may be at least 80% of the area of a lift shaft or other space accommodating said elevator system.

The lift mechanism may comprise a safety mechanism to control the movement of the elevator car. The elevator car may be supported from one side such that the elevator car is cantilevered. The elevator car may be formed of a composite material.

Whilst the invention has been described above, it extends to any inventive combination of the features set out above, or in the following description or drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be performed in various ways, and an embodiment thereof will now be described by way of example only, reference being made to the accompanying drawings, in which:

Figure 1 is a top view of a lift shaft with a lift mechanism, in accordance with embodiments of the present invention;

Figure 2a is a side view of the lift mechanism;

Figure 2b is an enlarged view of circle A of Figure 2a;

Figure 3a is a front view of the lift mechanism;

Figure 3b is an enlarged view of section E-E of Figure 3a; Figure 4a shows a cross-sectional view of the lift mechanism;

Figure 4a shows a cross-sectional and enlarged view of circle B of Figure 4a;

Figure 5a shows a side view of lifting posts in accordance with embodiments of the present invention;

Figure 5b shows an enlarged view of circle F of Figure 5a; and

Figure 6 shows a front view of the lifting posts and fixing locations.

DETAILED DESCRIPTION OF EMBODIMENTS

The term 'upward' as used herein will be understood to refer to extension or movement from a lower position to a relatively higher position. Whereas the term 'downward' as used herein will be understood to refer to extension or movement from a higher position to a relatively lower position. Above the lift car is to be taken to mean above the surface of the lift car furthest away from the motor. Below/beneath/underneath the lift car is to be taken to mean below the surface of the lift car closest to the motor.

Figure 1 shows a lift shaft 10 comprising a lift car 12 and a lift mechanism 20. The lift car 12 also comprises doors 13 and slam posts 16a, 16b, against which the doors locate.

The cross-section of the lift car 12 is square in shape with one corner 'cut off' at a substantially 45 degree angle. The cross-sectional area of the lift car 12 is around 80% of the cross-sectional area of the lift shaft 10. Advantageously, the cross-sectional area of the lift car 12 is significantly greater than the cross-sectional area of a conventional lift car, in respect of a comparably sized shaft. A greater cross-sectional area may increase, such as doubles, the capacity of the lift car.

The cross-sectional area of the lift car 12 fully complies with at least the European standards outlined in the Disability Discrimination Act 1995, which stresses the importance of having sufficient space available for wheelchair manoeuvring. A benefit of an increased cross-sectional area may be a greater manoeuvring area for wheelchair users, as demonstrated by the shaded circle in Figure 1.

The lift mechanism 20 is located between a corner of the lift shaft 10 and the cutoff corner of the lift car 12. It will be appreciated however that the lift car 12 could have any cross-sectional shape, as long as one corner of the lift car is sufficiently cut away to accommodate the lift mechanism 20.

The lift car 12 is made of a composite material, such as fibre glass or carbon fibre, or it could be formed of a honeycomb core sandwiched between sheets of aluminium or the like. Advantageously, composite materials are typically stronger (for example, around 10 times stronger), for the same mass of conventional materials such as steel.

This would allow the lift car to be lighter while still retaining a similar strength. For example, taking the average person to weigh 75kg, a conventional lift car with 10 people will weigh around 1500kg, whereas a lift car made of composite material with 10 people will weigh around 900kg.

The doors 13 are also made from a composite material, which reduces the weight from, for example, 100kg (for steel doors) to around 10 - 15kg (for composite doors).

As shown in Figures 1 - 6, and as will be described in more detail below, the lift mechanism 20 comprises a set of four vertical beams 40 - 43 arranged into a first pair 41,43 and a second pair 40,42, as shown in Figure 4. At least one of the beams 40 - 43 is secured to the lift shaft 10 via a fixing bracket 28. A continuous chain or a looped chain, such as a roller chain 50, extends lengthways between beams 41 and 43, and also extends lengthways between beams 40 and 42, such that the chain 50 rotates in use around both pairs of beams.

A motor 30 drives the chain 50 around the pairs of beams 40 - 43. The motor 30 moves in a first, or forward, direction; and a second, or backwards, direction. The motor 30 is located beneath the lift car 12 at the bottom 18 of the lift shaft 10 within a pit, or recess. Since the lift car 12 is much lighter than a conventional lift car, the motor does not need to provide as much power to drive the chain 50 to move the lift car 12 upwards and downwards. For example, a conventional lift typically requires around 240V of power, whereas the present lift requires 24V DC. This may allow the motor to be smaller, and thus take up less space within the lift shaft compared to conventional lift motors or hydraulic systems.

Attached to the chain 50 is a lifting plate 22. The lifting plate 22 is located underneath, and is attached to, the base of the lift car 12.

Figures 2a and 2b show a side view of the lift mechanism 20, including beams 40 and 43. The beams 40 - 43 comprise fixing points 44 to which brackets 54 attach to separate and secure the beams 40 - 43 into pairs, as shown in Figure 4. The chain 50 loops around gear 34 located at the bottom of the beams 40 - 43. As will be described in more detail below, gear 34 is rotated by the motor 30 in use, which in turn drives the lifting plate 22 via the chain 50.

Figures 3a and 3b illustrate how the lifting plate 22 is attached to the chain 50. The lifting plate 22 comprises a top plate 23 adjacent to the lift car 12. The top plate 23 comprises an anti-vibration material, such as polyurethane foam. The lifting plate 22 attaches to the chain 50 via three "prongs": a security fork 47 and two load cells

52. The security fork 47 applies load to the chain 50 only in one field, and the load cells 52 measure weight and force to ensure that there is no overload on the lift car 12.The three prongs 47, 52 attach the lifting plate 22 to the chain 50 by interlocking with the gaps between adjacent links of the chain 50. In an exemplary embodiment, a beam load cell is built in as a lower fork into the chain. This is attached to the lift car via an isolation mount. There may also be a second fork which is attached directly to the lift car which is configured to hold the lift car if the first fork fails (this would also show as a zero load on the load cell which could then be used to trigger a broken fork alarm, for example).

The lift mechanism 20 also comprises a safety mechanism 32, shown in Figure 1.

The safety mechanism 32 is located directly underneath the lift car 12, and helps to prevent any uncontrolled movement, particularly downward movement, of the lifting plate 22 and lift car 12. Sensors (not shown) are located at one or more locations within the lift mechanism 20 to detect, among other parameters, the speed of movement of the chain 50 in use. If the chain 50 is moving at a predetermined, or safe, speed, the safety mechanism 32 remains deactivated. The safety mechanism 32 is coupled to an electromagnetic device which is energised during normal operation (with the safety mechanism deactivated). However, if the sensors detect that chain 50 is moving too fast, an "over speed", or if the movement of the chain 50 is generally uncontrolled, particularly when the doors 13 are open (i.e. at landing), then the power to the electromagnetic device is cut and the safety mechanism 32 is activated. In use, when activated, the safety mechanism 32 clamps securely onto beams 40 - 43, which prevents any downwards or upwards movement of the lifting plate 22 and thus prevents any downwards or upwards movement of the lift car 12. It will be appreciated that safety mechanisms of his type exist, and suitable such devices will be known to a person skilled in the art.

Figures 4a and 4b show the arrangement of the beams 40 - 43 and the lifting plate 22 in more detail. In use, the lifting plate 22 only moves upwards and downwards between beams 41 and 43. The beams 41 and 43 form one pair, and are connected together by brackets 54. The beams 40 and 42 form the other pair, and are also connected together by brackets 54. The brackets 54 attach to fixing points 44, shown in Figures 5 and 6, spaced at intervals 49 along the length of the beams 40 -

43. Brackets 54 are substantially "C"-shaped, with the chain 50 running up and down the hollow, "middle", section of the "C", with the lifting plate 22 extending perpendicularly outwards from the opening of the "C". Figure 5 also shows support members 48 spaced at intervals along the beams 40 - 43 to attach beam 40 to 43, and also beam 41 to 42. In other words, the first pair of beams 41,43 and the second pair

40,42 are secured to each other via support members 48. This adds additional strength and stability to the lift mechanism 20, so it can better support the weight of the lift car 12 on the lifting plate 22.

The lift car 12 is stabilised within the lift shaft 10 via sliding shoes 24, as shown in Figure 1. There are two sliding shoes 24 attached to the top of the lift car 12 and two corresponding sliding shoes 24 attached to the bottom of the lift car 12. Further sliding shoes 26 are attached to the right hand corner of the lift car 12 (as shown in Figure 1). One sliding shoe 26 is attached to the top of the lift car 12, and one corresponding sliding shoe 26 is attached to the bottom of the lift car 12. In use, the sliding shoes 24, 26 interlock with stationary vertical rails 27, and slide upwards and downwards along the rails 27 as the lift car 12 moves upwards and downwards respectively.

The sliding shoes 24,26 advantageously help to minimise any lateral or rotational movement of the lift car 12. The lifting plate 22 itself does not prevent the side-to- side movement of the lift car 12, therefore it is beneficial to provide sliding shoes 24,26 to prevent, or at least minimise, such movement.

The lift car 12 is picked up, and supported, from one side by the lifting plate 22 and sliding shoes 24,26. In other words, the lift car 12 is cantilevered within the lift shaft 10. The lift car 12 is guided up and down the lift shaft 10 due to the walls of the lift car 12 being adjacent to the walls of the lift shaft 10. This is in direct contrast to conventional lift systems where the lift car is supported along its central axis from above by a system of ropes, pulleys and counterweights, and is guided up and down the lift shaft by additional guide rails. For example, conventional lifts typically have counterweights which are around 1.5 times the maximum weight limit for that particular lift car. Sufficient space must be left between the walls of the lift car and the walls of the lift shaft to accommodate the ropes, pulleys, counterweights and guide rails, which means that the cross-sectional area of the lift car is smaller and its capacity is therefore reduced.

In use, to move the lift car 12 from a lower height to a greater height, the motor 30 activates and turns in a forwards direction. The activation of the motor 30 causes gear 34 to rotate, which in turn causes chain 50 to rotate in an anticlockwise direction around the beams 40 - 43. The lifting plate 22, which is attached to chain 50, is subsequently caused to move in an upwards direction. The upwards movement of the lifting plate 22 pushes the attached lift car 12 from below to move the lift car 12 in an upwards direction from the lower height to the greater height. The motion of the lift car 12 is stabilised by the sliding shoes 24,26, so that the lift car 12 does not rotate as it is pushed upwards.

Furthermore, to move the lift car 12 from a greater height to a lower height, the motor 30 firstly stops, and then begins turning in a backwards direction. Gear 34 also stops and rotates in the opposite direction, which in turn rotates the chain 50 in an opposite, or clockwise, direction around the beams 40 - 43. The lifting plate 22 is subsequently caused to move in a downwards direction. The downward movement of the lifting plate 22 guides the attached lift car 12 from below to move the lift car 12 in a downwards direction from the greater height to the lower height. Again, the motion of the lift car 12 is stabilised by the sliding shoes 24,26, so that the lift car 12 does not rotate as it is guided downwards. The motion of the lift car 12 (in both an upwards and downwards direction) is guided by the walls of the lift shaft 10.

The lift mechanism 20 further comprises a control panel (not shown). The control panel communicates with various sensors to continuously monitor several different parameters of the lift car 12, and also the movement of the lift car 12, such as its speed, the time it takes for the lift car 12 to travel from one stop/floor to another, the voltage and current drawn by the motor 30, and the weight of the lift car 12. The data is wirelessly communicated to an operator, typically in a location remote from the lift shaft 10, where it can be analysed. The data is either communicated continuously in real-time, or stored in memory in the control panel and communicated at a later time, for example on request of an operator.

The values for each of the parameters monitored are predetermined to within certain tolerance levels, and if the parameters are found to fall outwith these set tolerance levels, this could indicate, for example, that there is wear in the lift mechanism 20, or the chain 50 requires lubricating. Remedial and preventative action can then be taken to ensure the safety of the lift mechanism 20 and lift car 12.

In use, after the lift car 12 is installed, initial tests are carried out to collect base data, such that the normal operating parameters of the lift mechanism 20 and lift car 12 are known. At set intervals, such as fortnightly or monthly, the same tests are run and the same data collected, and compared with the base data. If any parameters are outside the accepted tolerance levels, this can immediately be identified and appropriate action taken.

Conductive rails (not shown) may be provided on the guide rails 27 for example, to carry 24DC power to the inside of the lift car 12 to power, for example, the internal lighting. This configuration provides a significant advantage in respect of prior art lift/elevator systems, because it eliminates the need for trailing cables.

The lift mechanism 20 described herein is suitable for use with small lift cars, for example with an 8 person capacity, to much larger lift cars, such as a 26 tonne goods lift.

For the avoidance of doubt, the terms 'lift' and 'elevator' are utilised interchangeably herein to refer to a platform or compartment housed in a shaft for raising and lowering people or things to different levels.

Although the invention has been described above with reference to an exemplary embodiment, it will be appreciated that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims.