GB2288385A - Refurbishment of lifts - Google Patents

Abstract

A method, whereby lifts using conventional drive mechanisms as shown in Fig. 1 may be converted to hydraulic operation, consists in excavating the lift shaft (3) base, or using an existing lift shaft well, for accommodating a ram (48), connecting the ram (48) to the base (12) of car (6) and removing the existing drive (4). Preferably, the original drive is retained until the conversion is complete so that the existing lift can remain in operation temporarily whilst conversion work is undertaken. The system is particularly useful in nursing and like homes. <IMAGE>

Description

Improved Lift Installations The present invention relates to improvements in lift installations, and especially to a means and method for the provision of improved drive systems for lift installations.

A problem is currently presented by existing lift systems in nursing homes across the United Kingdom. There are some eight thousand nursing homes in which a non-standard type of lift system is installed. These homes, mostly having been built in the late nineteenth century, present a common problem to the designer of a lift installation, in that the lift shaft facilities present are generally narrow to such an extent that a conventional lift installation, using both a lift car and counterbalance, was considered impractical by the designer of the existing installations.The existing installations are of a type in which a lift car is suspended by means of a chain which, at its highest point, runs through a worm-and-wheel gearing mechanism, and which is collected at the other side by vertical plastic piping attached to the side of the lift shaft and in which the loose end of the chain hangs freely. The lift car is moved within the lift shaft by the operation of an electrically-powered motor which engages the gearing mechanism. This existing installation will be referred to as an unbalanced lift installation, since the weight of the lift car is not countered by the use of a counterbalance on the suspender chain end opposite to that to which the lift is attached.

A major issue with the unbalanced lift installations is that a number of incidents have occurred in recent years, the worst of which were fatal. The gearing mechanisms are thought to have been the cause. Because of the unbalanced nature of the lift systems, much strain is put on the worm-and-wheel gear boxes and this is thought to cause an intolerable rate of wear of the mechanisms, subsequently resulting in their failure. Again, because of the unbalanced nature of the suspending means, if a gear mechanism wears to the extent that it breaks under the strain of the lift car below, the lift begins to free-fall.

Two safety devices are installed in the event of free-fall of the lift, one being that the lift is provided on its underside with a strengthening plate and the bottom of the lift shaft is provided with a rubber buffer, the two components designed to stop a falling lift in a more gentle fashion than is possible without the safety device. A second device is provided in the form of spiked metal balls working in conjunction with inclined protrusions from the side of the lift which, in the event of free-fall, cause the balls to grip the guide rails on which the lift car runs in the lift shaft to stop the lift in its place.

The effectiveness of these safety devices aside, danger and inconvenience is still posed to the users, especially inhabitants of the nursing home, in the case of failure of the gear box. For this reason, regulations regarding lift installations are altering to ensure that the present unbalanced lift systems are replaced in the near future, and there has been much thought and discussion over a suitable system with which to replace them.

The limited dimensions of the lift shafts rules out commercially available systems, as their components occupy valuable lift shaft space. In the case of a conventional system, which utilises an overhead drive and a counterbalance, the counterbalance occupies valuable shaft space. There exist systems using hydraulic rams, in which the hydraulic ram attaches to the lift car by means of a cantilever device, which too restricts the dimensions of the car in the lift shaft.

The lift in a nursing home is an essential facility, which must be operable at all times for the safety of its inhabitants. Its conversion is most difficult, since it must remain at least partially in service throughout the conversion. A possibility consistent with this requirement is the construction of an entirely new lift shaft. However, because of the formation of the nursing homes, with corridors converging on the lift facilities, such a new shaft would have to be constructed adjacent the existing one, and would render several bedrooms uninhabitable. Such a loss in bedroom capacity of a nursing home results in the loss of considerable income, and this, combined with the cost involved in the construction of the new shaft, makes such a scheme impractical.There is a need for a means and method of replacing only the existing drive mechanisms by new drives which are safe, do not occupy lift shaft space, and can be installed in such a way that the existing system can remain at least partially in service.

Further limitations of the existing installations are that they operate only at a single speed, that they move with excessive noise and unevenly, that they allow only limited head-room in cases where the lift shaft is not substantially higher than the highest lift level, and that the lift cars can be stopped at the various levels only to an accuracy of within 25mm, thus often creating imperfect floor levels which can be a further cause of accidents.

An object of the present invention is to provide a method for the installation in a lift shaft of a lift drive mechanism which occupies little space in the lift shaft and operates effectively without being liable to cause injuries, fatal or otherwise, in the event of failure of the drive mechanism.

The present invention provides a method for the conversion of a lift system comprising a lift shaft, a lift car, suspending means there for and a lift drive mechanism located above the lift car, wherein the base of the lift shaft is excavated, or, where present, the lift shaft well is used, to accommodate a vertical hydraulic ram which provides a new drive mechanism which works by supporting the lift car by its base and moving it vertically up or down by direct action.

The present invention will now be described, by exemplary means, with reference to the accompanying drawings, wherein: Fig. 1 is a sectional side view of an existing lift system; Fig. 2 is a sectional top view of the lift system shown in Fig. 1; Fig. 3 is a sectional side view of a lift system according to an embodiment of the present invention; Fig. 4 is a top view of the lift shaft base shown in Fig. 3.

Fig. 5 is a sectional side view of the borehole showing plastic lining sleeves; Fig. 6 is a sectional side view of a box-like base member, and Fig. 7 is a perspective view of the box-like member in Fig.

6.

Referring first to Fig. 1, in which an existing lift installation 2 in a private nursing home comprises a lift shaft 3 containing a drive mechanism 4, a lift car 6 and a buffer stop 8, the lift car 6 being suspended by a chain 10 and having fixed on the underside of its base a strengthening plate 12, and the buffer stop 8 having a rubber buffer 14 fixed atop a strong pole 16 which is secured in the base of the lift shaft 3.

The car 6 is normally suspended by the chain 10, but in the event of a chain break etc., when the car 6 is no longer supported in the lift shaft 3, the car 6 falls under the force of gravity towards the base of the lift shaft 3. When the car 6 hits the buffer, the rubber, having elastic properties, deforms to increase the amount of time over which the car 6 is decelerated, thus reducing the strain which the car 6 must endure. The strengthening plate 12 is fitted to the base of the car 6 to cooperate with the buffer stop 8 to prevent the car 6 from disintegrating at the bottom of such a fall, and the strengthening plate 12 is therefore designed to transmit much force to the car without it breaking under that force.

The existing unbalanced drive mechanism 4 consists of an electric motor, a worm-and wheel gear box, a plastic sheath 18. The chain 10 is attached to the lift car roof 20 and runs through the gear box above to hang down into the sheath.

The lift car, as shown in Fig. 2, is vertically movable in guide means consisting of two vertical guide rails 22 which are attached to opposite sides of the lift shaft 3 and which cooperate with projections 24 on the lift car 6 to ensure that the car 6 remains a constant distance from the sides of the lift shaft 3 at all times.

The lift is operated by control buttons inside the lift car 6 and by buttons next to the doors at the entrances to the lift, whereby the motor rotates to feed the chain 10 through the drive mechanism 4 and to move the car 6 up or down. The motor operates at a single speed and must therefore operate relatively slowly to prevent overly sudden stops as the lift comes to rest at a desired level.

It can be seen from Fig. 1 that the gear box mechanism of the existing system is under strain on one side only at all times; this unbalanced strain causes considerable wearing of the mechanism which results, in exceptional cases, of the failure of the gear box and subsequent free-fall of the lift car 6 to cause severe injury to the ocupants thereof.

Referring now to Fig. 3, in which there is shown a lift system 32 which itself is according to an embodiment according to the invention the subject of application No 2267888 from which the present application is divided; the lift system 32 comprises a modified lift shaft 33, a lift car 6 and a hydraulic ram drive 34. The lift car 6 is identical to that shown in Fig. 1. The lift shaft 33 is modified, compared to that shown in Fig. 1, in that it has a trench 38 dug in its base, from which a borehole 40 extends downwards completely to accommodate a hydraulic ram 42.The ram 42 is supported in the borehole by means of two bars 44 which are fixed at their ends in the foundations 45 of the lift shaft 33, and which extend across the trench 38 to support a strong metal plate 46 in which the cylinder 48 of the hydraulic ram 42 is securely mounted in a horizontal position so that the base thereof does not connect with the bottom of the borehole 40. The hydraulic ram 42, which is powered by a hydraulic power unit not shown in the diagram via suitable hydraulic connections, has a piston 50 upon which the lift car 6 is supported by a strengthening plate 12. Again, the lift car 6 is guided in the shaft by rails 22 cooperating with projections 24 from its sides as shown in Fig. 2.

The lift installation 32 described is operated, again, by buttons inside the lift car 6 and at entrances in the lift shaft 33 thereto, which operate the hydraulic power unit to push upwards or to lower downwards the hydraulic piston 50 upon which the lift car is mounted. This effects quiet and smooth travel of the car 6 within the lift shaft 33. The speed of the piston 50 can be varied allowing the relatively accurate stopping of the lift car 6 at an entrance, the stopping to be gradual rather than sudden, and the car 6 to travel between levels at around double the speed of that in the unbalanced lift system 2.

Further, the system has a considerable safety advantage over the unbalanced system 2 since, in the event of failure of the drive mechanism 34, e.g. the failure of any seals in the hydraulic ram 42, the lift car 6 cannot fall freely since it is supported at all times by the piston 50 below it and hydraulic fluid can only escape through any broken seals at a relatively small rate. The lift car 6, in the event of such failure, will slowly and safely fall to the base of the lift shaft 33.

Referring now to Fig. 5, a sleeve 54, preferably of plastics material, is accommodated in the borehole 40, thus providing a neat and clean shaft for the ram cylinder 48. The sleeve is preferably surrounded by filler material 56, such as grout or concrete, and may come in sections for ease of transport and installation. Three such sections 54a, 54b, 54c are shown in Fig. 4.

Fig. 5 shows an alternative way of securing the ram to the base of the lift shaft. A box-like member 58 is bolted to the foundations of the lift shaft by means of jacking screws 62 inserted through holes 64 in outturned flanges 66. In its base, box 58 is provided with a central aperture with which the aperture in plate 46 registers. Plate 46 is as before mounted at the upper edge of the ram cylinder 48, and in this case bolted to the base of box 58.

Fig. 6 is a perspective view of the box-like member in Fig.

5, clearly showing the fastening flanges 66 and arrangement of plate 46.

The lift system shown in Fig. 1 can be modified to that shown in Fig. 3 using a method providd by the present invention.

During modification, the old system 2 need not be taken out of service and the nursing home is provided with the use of a lift at all times during the modification. Firstly, the buffer stop 8 is removed and the trench 38 is cut into the lift shaft foundations 45. The hole 40 is then bored into the ground at the base of the trench 38. Holes are cut into the side of the trench to accommodate the ends of the crossbars 44, which are then securely concreted in place. The metal plate 46 is then attached across the bars 44 and fixed in place by bolts. The plate 46 has a hole in its centre through which the lower portions of the hydraulic ram 42 fit, and the upper portion of the ram cylinder 48 is fixed to the plate 46 to mount the ram 42 in a vertical position.The installation is completed by lowering the lift car 6 onto the ram piston head 52 and attaching same to the strengthening plate 12, thus rendering the overhead drive 4 and suspension means 10 unnecessary and which are then removed. It has been calculated that the strengtheining plate 12 is a sufficiently strong means of supporting the lift car on the piston head 52 during operation of the lift.

In some cases, in which the dimensions of the lift car 6 are restricted by the overhead space requirement of the old drive means, the lift car 6 may be extended to allow more headroom therein, once the old drive means has been removed.

During the conversion procedure, the lift installation to be replaced can, to a great extent, continue to be in service.

While work is actively carried out inside the shaft, the lift is temporarily taken out of use, the stationary lift car suitably being located at the top of the lift shaft. Before the new installation is completed, but while no work is carried out, e.g. at night, the existant lift system may be put back in service. The installation equipment is then removed from the shaft to the extent that is necessary, and the old system simply used as normal. This aspect of the conversion according to the invention is of course very convenient as minimum disruption during installation is caused.

Claims (5)

1. A method for the conversion of a lift system comprising a lift shaft, a lift car, suspending means therefor and a lift drive mechanism located above the lift car, wherein a vertical hydraulic ram is accommodated in the lift shaft, providing a new drive mechanism which works by supporting the lift car by its base and moving it vertically up or down by direct action.

2. A method according to claim 1, wherein the base of the lift shaft is excavated so as to accommodate said ram.

3. A method according to claim 1, wherein an existing lift shaft well is utilised for accommodating said ram.

4. A method according to any of claims 1-3, characterised in that the original lift drive mechanism is retained in working order until the conversion is about to be completed, such that the lift may be put into temporary service during the period of conversion.

5. A method according to Claim 1 substantially as hereinbefore described with reference to the Figs. 3 to 7 of the accompanying drawings.

5. A method for the conversion of a lift system substantially as hereinbefore described with reference to the Figs. 3 to 7 of the accompanying drawings.

Amendments to the claims have been filed as follows 1. A method for the conversion of a lift system comprising a lift shaft, a lift car, suspending means therefor and a lift drive mechanism located above the lift car, wherein the lift car is raised in the lift shaft, hydraulic ram to be used in place of lift drive mechanism is located in the bottom of the lift shaft, and is connected to the base of the lift car providing a new drive mechanism which works by supporting the lift car by its base and moving it vertically up or down by direct action.

2. A method according to claim 1, wherein the base of the lift shaft is excavated so as to accommodate said ram.

3. A method according to claim 1, wherein an existing lift shaft well is utilised for accommodating said ram.

4. A method according to any of claims 1-3, characterised in that the original lift drive mechanism is retained in working order until the conversion is about to be completed, such that the lift may be put into temporary service during the period of conversion.