GB1561509A - Lift systems - Google Patents

Description

PATENT SPECIFICATION

( 11) 1 561 509 ( 21) Application No 3629/77 ( 22) Filed 28 Jan 1977 ( 23) Complete Specification Filed 30 Dec 1977 ( 44) Complete Specification Published 20 Feb 1980 ( 51) INT CL B 66 B 5/16 ( 52) Index at Acceptance B 8 L 11 4 8 X CD X 3 F 25 CM ( 72) Inventor: STANLEY LEWIS ( 54) LIFT SYSTEMS ( 71) We, COAL INDUSTRY (PATENTS) LIMITED, a company organised in accordance with the laws of Great Britain of Hobart House, Grosvenor Place, London, SW 1 X 7 AE do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly

described in and by the following statement:

This invention relates to lift systems, and in particular, but not exclusively, to lift systems used in mining operations.

If, due to a failure in a lift system, a lift cage falls freely to the bottom of the shaft in which it is travelling the impact can cause a great deal of damage to the cage, the shaft bottm, and, more importantly, to the occupants of the cage The damage on impact is caused by the nearly instantaneous conversion of the cage and its occupants' kinetic energy into other forms of energy where the lift system is used in a deep mine or a tall building, the kinetic energy generated during a free fall of the cage is considerable, and the impact can cause loss of life or very serious injury to the occupants.

To prevent as far as possible the occurrence of such accidents, most lift systems are provided with numerous safety devices For instance the lift cage is usually suspended from at least two cables so that the cage can be supported even though one cable breaks.

Braking devices are also put in the system to stop the movement of the cables should the winding gear which moves the cage become inoperative The braking systems act independently of the winding gear and are usually backed up by further braking devices Therefore in most cases travel in lift cages is relatively safe.

However, in spite of all these safety precautions, there is still a possibility, although fairly remote, that there will be a multiple failure in the lift system which will allow the lift cage to fall freely in the shaft This may for example occur because of a major disaster such as an earthquake or a very extensive fire.

It is therefore an object of the present invention to provide a fail-safe lift system which will substantially reduce or prevent the damage which is usually associated with the free-fall of a lift cage to the bottom of the shaft.

According to the present invention a lift system comprises a lift cage movable in a shaft by winding gear, which cage has a blade secured thereto, and a column of cuttable energy-absorbing material located in the shaft in such a manner that the blade is capable of cutting into the material.

The energy-absorbing material is of a nature such that it will yield when a predetermined force is applied to it by the blade and must exert a retarding force on the blade.

Conveniently the material is able to support the unladen cage when the cage is stationary.

However if the cage is moving downwards when the blade contacts the material, the material should yield The energy exerted to cause the material to yield will come from the kinetic energy of the cage Therefore the kinetic energy of the cage will be dissipated as the blade moves downwardly through the material, and the cage is eventually brought to rest In this way there should be no major impact, providing all the kinetic energy is dissipated and the cage stops before the blade has cut through all the materials in the column, and certainly there should be no impact large enough to cause any substantial damage either to the cage or its occupants as the blade engages with the column.

The composition of the material will vary depending on the applications For instance miners are used to fairly abrupt deceleration and so a relatively strong material may be used in mines, whereas in a building a less strong material may be used for the convenience of the cage's occupants However the ( 19) 1,561,509 weaker the material, the larger must be the column The material to be used and the length of the column must be determined for each separate application.

Suitable materials include autoclaved aerated concrete, concrete including a lightweight aggregate, straw, wood wool blocks, synthetic wood and foamed reinforced plastics materials.

The column may be enclosed in a guide, which may extend the whole length of the shaft.

If the blade is fixedly secured to the cage the column will only extend up to the lowest level to which the lift cage normally descends The guide may, in use, at all times be engaged with the blade, or may only engage with the blade if the lift cage descends below its normal lowest level In the latter case the guide may taper from top to bottom, to ensure that the blade en gages therewith and that the blade passes through the column Since when a fixed blade is used the column only extends up to the normal lowest level of the lift cage, the retarding action of the material will not come into play unless the lift cage passes this level downwardly, and in most cases this will only occur if the lift is not being controlled.

Alternatively the column of material may extend all the way up the lift shaft In this case the blade must be movable from a retracted position, in which the blade does not project beyond the sides of the lift cage, to an extended position, in which the blade projects into the column of material The blade may be activated to move from the retracted position to the extended position by the operation of an overspeed device, a device which measures the tension on the cables, or manually by activating an emergency switch in the lift cage The means whereby the blades is moved into the extended position should be powered independently of any power supply to the cage, and may for instance comprise an explosive bolt type of device or a self-contained pneumatic ram system Preferably the movement means locks the blade into the extended position after it has been activated.

Preferably the guide and the blade have complementary shapes but this is not necessarily the case The blade may be a single blade, or may where the blade is fixedly secured to the cage, comprise a T-shaped piece having sharpened lower edges Preferably there is a plurality of complementary guides and blades disposed symmetrically in the shaft and on the cage respectively The blade(s), are preferably made of a strong metal such as mild steel or key steel The guides must be located such that only the blades are engageable therewith, leaving enough clearance for the cage to pass unhindered.

The guide may be composed of any substance and may define a space into which the material is to be placed, or may be made of the material itself The material may be flowable, for instance a powder, and in this case a portion of the guide must be made of easily yieldable material so that the blade can pass therethrough.

The remaining parts of the lift system are well known in the art, and the system may also include braking systems and other conventional safety devices, but these parts are not further described as they do not form part of the invention.

The present invention may be incorporated into any existing lift system, but is envisaged as being of special use in the mining industry.

The invention will now be more specifically described, by way of example only, with reference to the accompanying drawings, in which; Figure 1 is a schematic sectional view of a coal mining operation incorporating a lift system according to the invention; Figure 2 is a perspective view of a guide as used in the system of Figure 1; Figure 3 is a perspective view of a blade as used in the system of Figure 1; and Figure 4 is a perspective view of an alternative blade for use in the system of Figure 1.

Referring to Figure 1, a coal mining operation includes a mine shaft 1 from which several roadways 2 are driven The roadways 2 lead to or run alongside the coal seams (not shown) which are being mined A lift cage 3 suspended from a cable 4 is movable up and down in the shaft 1 by winding gear 10 The winding gear 10 includes various safety and braking devices, but these are not shown.

Two blades 5 are mounted diametrically opposite one another at the bottom of the cage 3 and projecting outwardly therefrom.

(only one blade 5 is shown in Figure 1).

Located on orin the sides of the shaft 1 and in engagement with blades 5 are two guides 12 (only one of which is shown in Figure 1) If the cage 3 descends below the lowest of the roadways 2 the blades 5 cut into a column of material 18 therein to retard the cage 3.

Normally the bottom of shaft 1 contains spoil from the mine and this may also retard the fall of the cage 3.

Referring now also to Figure 2 each guide 12 comprises a box of rectangular cross section having an opening 16 in one side, located on or in the wall of shaft 1 The box may be made by bending a flat plate into the shape shown in Figure 2, or by any other suitable method The box is filled with autoclaved aerated concrete 18 up to the level of the lowest of the roadways 2 Thus during normal operation of the lift the blades 5 move unhindered up and down in the guide 12, but as soon as the cage 3 descends below 1,561,509 the lowest roadway the blades 12 contact the material 18.

Referring also to Figure 3 each blade 5 is made of steel and is wedge shaped in both the vertical and horizontal directions An alternative form for the blade is shown in Figure 4 and comprises a T-shaped blade 5 ' having a triangular sharpened T-piece 20 and a sharpened stalk 21, which is mounted on the lift cage 3.

The system herein described allows a lift cage to be brought to rest gradually from free fall without doing any substantial damage to either the cage or its occupants.

Claims (22)

WHAT WE CLAIM IS:-

1 A lift system comprising a lift cage movable in a shaft by winding gear, which cage has a blade secured thereto, and a column of cuttable energy-absorbing material located in the shaft in such a manner that the blade is capable of cutting into the material.

2 A lift system according to claim 1, wherein the material is capable of supporting the unladen cage when the cage is stationary.

3 A lift system according to either one of claims 1 and 2, wherein the material is selected from autoclaved aerated concrete, concrete including lightweight aggregate, straw, wood wool blocks, synthetic wood and foamed reinforced plastics materials.

4 A lift system according to any one of the preceding claims, wherein the material is enclosed in a guide.

A lift system according to claim 4, wherein the guide extends substantially the whole length of the shaft.

6 A lift system according to claim 4, wherein the guide only extends up to the lowest level to which the lift cage normally descends.

7 A lift system according to claim 6, wherein the guide tapers from top to bottom.

8 A lift system accordind to any one of claims 1 to 7, wherein the column of material only extends up to the lowest level to which the lift cage normally descends.

9 A lift system according to claim 8, wherein the blade is fixedly secured to the outside of the cage.

10 A lift system according to claim 9, wherein the blade is T-shaped.

11 A lift system according to any one of claims 1 to 5, wherein the column of material extends substantially the whole length of the shaft.

12 A lift system according to any one of claims 1 to 8 and 11, wherein the blade is movable from a retracted position, in which the blade does not project beyond the sides of the lift cage, to an extended position, in which the blade projects into the column of material or the guide.

13 A lift system according to claim 12, wherein the blade is activated to move from the retracted position to the extended position by means powered independently of the winding gear.

14 A lift system according to claim 13, wherein the means comprises an explosive bolt.

A lift system according to claim 13, wherein the means comprises a selfcontained pneumatic ram system.

16 A lift system according to any one of claims 13 to 15 wherein the means is actuated by the operation of an overspeed device.

17 A lift system according to any one of claims 13 to 15 wherein the means is actuated by the operation of a device which measures the tension in the winding gear's cables.

18 A lift system according to any one of claims 13 to 15 wherein the means is operated manually using a switch in the lift cage.

19 A lift system according to any of claims 12 to 18, and including a locking means which prevents the blade from moving from the extended to the retracted position.

A lift system according to any one of the preceding claims, and including a plurality of blades, complementary columns of material and, where appropriate, guides.

21 A lift system according to claim 21, wherein the blades are symmetrically disposed around the lift cage.

22 A lift system according to claim 1, substantially as hereinbefore described with reference to the accompanying drawings.

For the Applicants J I WOOD Chartered Patent Agent Printed for Her Majesty's Stationery Office, by Croydon Printing Company Limited, Croydon, Surrey, 1980.

Published by The Patent Office, 25 Southampton Buildings, London, WC 2 A l AY, from which copies may be obtained,