GB1601809A

GB1601809A - Linear arrestors

Info

Publication number: GB1601809A
Application number: GB7291/77A
Authority: GB
Original assignee: SELTRUST ENG Ltd
Current assignee: SELTRUST ENG Ltd
Priority date: 1977-02-22
Filing date: 1977-02-22
Publication date: 1981-11-04
Also published as: AU3353078A; ZA781049B; CA1098881A; SE7801837L; DE2807267C2; FR2380928B1; AU519936B2; BE864174A; FR2380928A1; DE2807267A1

Description

(54) LINEAR ARRESTORS (71) We, SELTRUST ENGINEERING LIMITED, a British Company, of Fleet House, 57/61, Clerkenwell Road, London EC1M 5SP, 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 arrestors for vehicles, such as mine cages, trains, aircraft and ships, such arrestors comprising a length of deformable ductile material and a device defining a non-straight path through the device for the length of ductile material.

When the device moves longitudinally relative to the length of material or vice versa, a substantially constant retardation force opposing such movement is generated partly by friction and partly by the work needed to effect any plastic deformation of the material that takes place as it is moved along the nonstraight path.

In most potential applications for such arrestors, it is essential that the value of the retardation should, in addition to remaining substantially constant, lie consistently within narrow limits. If the deceleration or retardation is too great, people travelling in the vehicle will be killed or injured and if the deceleration or retardation is too small, the vehicle will not be brought to rest within the available distance, leading to impact of the vehicle at the end of its travel again with consequent death or injury. Generally, the arrestor will lie dormant, often for many years, but must be immediately available and operate consistently at its designed retardation in the event of a sudden emergency.

Proposals for arrestors of the kind with which the invention is concerned have existed for over seventy years.

More recently, arrestors have been proposed in U.S. Specifications Nos. 2578753, 2979163, 2980213, 3017163, 3211260 and 3377044 in which a coil of strip is contained in a housing and has its outer end passed around a large number of rollers or pegs. At the start of an arresting operation, at least the leading portion of the strip (and all of the rollers) have to be rapidly accelerated up to the initial speed of the object to be decelerated, resulting in a violent jerk. The large number of rollers or pegs and the complex path to be followed by the strip as it is unwound and drawn over the rollers or pegs result in high friction and thus possibly inconsistent operation if the device has been neglected for many years while the inevitable bulk and weight of the housing and strip render such devices unsuitable for a large number of applications such as on railways and in lift shafts where the space between the vehicle and surrounding structure is to be minimal and where the thickness and width of the strip required for a scaled-up version suitable for mine lift cages, ships and trains would require impossibly massive and heavy installations to support and guide the strip.

Accordingly, none of these known arrestors has been widely used for arresting vehicles.

According to the present invention, there is provided an installation comprising a vehicle movable along a substantially predetermined path and an arrestor for stopping or slowing the vehicle in a portion of the path, the arrestor comprising a flat strip of ductile material extending in the direction of the path in which the arrestor is to operate, the strip being of width greater than thickness and of uniform thickness across its width, the strip being threaded through a set of not more than five rollers carried on a frame for plastic deformation of successive elements of the strip around the rollers when the strip is moved through the set of rollers during an arresting operation, each roller being rotatably mounted on the frame, each roller being rotatable about its axis by the strip when the strip is drawn through the set of rollers with alternate rollers in contact with alternate sides of the strip, the spacing between adjacent roller surfaces being greater than the strip thickness, the axes of all rollers in the set being fixedly located on said frame and with respect to each other, the rollers continuously maintaining a portion of the strip in a deformed condition and the maximum deformation of successive elements of the strip during relative strip-roller movement being constant, the strip extending substantially in the same direction along the path as it leaves the set of rollers, the arrestor being mounted on the vehicle or a stationary structure and having one of its frame and the leading end of the strip secured thereto, the other of the frame and strip leading end being engageable by the stationary structure or vehicle respectively as the vehicle reaches the said portion of the path.

With this arrangement, a major part of the retardation force is generated by work done in plastic deformation of the strip as it passes through the set of rollers. Since each bending operation occurs around a roller there is substantially no frictional slipping contact with the strip so that the state of the strip surface (oily, rusty or painted) does not matter.

The bearings of the rollers will have a smaller radius than the roller surfaces so that the drag exerted on the strip by friction in the rollers will be appreciably less than that which would be exerted on the strip by fixed pegs in place of rollers. The frictional drag can be further reduced by appropriate choice of bearing materials. Improved consistency can be achieved by using self-lubricating materials for the bearings, for example bearings incorporating polytetrafluoroethylene.

Alfternatively, bearings of hard aluminium alloy with perhaps a smear of lubricant may be used.

By keeping the number of rollers in the set small, i.e. not more than five and preferably three, the contribution of friction to the retardation, for example in the bearings of the rollers, is also reduced. By having an odd number of rollers, the emerging strip is codirectional with the strip entering the set of rollers, thereby helping to ensure that the angle of wrap of the strip with each roller can be maintained constant.

In one form of embodiment the strip is mounted on stationary structure adjacent the portion of the vehicle path over which the retardation is to take place, for example above the normal upper position of the lift cage in a mine shaft. The frame carrying the set of rollers is then mounted on a light carriage which can be engaged by the cage or other vehicle on overwind or overshooting.

Advantageously, where the vehicle to be arrested has guides for example ropes or rails, the carriage is itself guided on these guides.

In another form of embodiment, the strip in its straight form is carried by the vehicle with the rollers engaged with the leading end of the strip and a suitable device is provided for engaging the roller frame when the arresting operation is required. This device may be in the form of a fixed projection in an overrun part of the vehicle path or a velocity or lack-of-tension sensitive device arranged to extend latches or to fire explosive bolts into structure alongside the path of the vehicle.

Where the strip cross-section is constant along the whole length of the strip, the retardation will be constant. However, by varying the cross-section of the strip along any portion of its length or if required along the whole length of the strip, the retardation may be varied. Thus, for example, the retardation may be arranged to increase along the strip path so as to accommodate vehicles where the load carried by the vehicle may appreciably vary. The variation in strip cross-section is achieved by using a strip of constant thickness, but varying width.

The invention will now be further described by way of example with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a lift cage and an arrestor in accordance with the invention positioned to slow-up the lift cage if it should descend beyond its lowermost intended position, Figure 2 is an elevational view showing components of the arrestor, Figure 3 shows a portion of Figure 2 with part of the frame cut away to show the rollers and strip, Figure 4 is a view similar to Figure 1 of a larger, two storey mine lift cage having two arrestors arranged on each side of its path of travel, Figure 5 shows one method of applying the invention to buffers for railway tracks, and Figure 6 shows a modification of Figure 3.

In the embodiment shown in Figures 1 to 3, a mine lift cage 1 (Figure 1) is connected to a winding rope (not shown) by a conventional linkage 2 and is guided on vertical guide rails 3, the cage for this purpose carrying sets of guide wheels 4 at its upper and lower ends.

On each side of the path of the cage 1 a cross beam 5 has its two ends firmly embedded in and supported in the lining (not shown) of the mine shaft. The guides 3 are anchored to the cross beams 5 by brackets 6, in addition to other conventional supports for the guides.

A mild steel strip 7 of rectangular crosssection, for example 120 mm. x 9 mm. is anchored firmly by its upper end to each of the beams 5. The strips 7 support the carriage 8 of an arrestor, the carriage 8 having suitable means such as the blocks 9 shown in Figure 1 for engaging an appropriately strong part of the frame of the cage 1 when the latter overshoots its lowermost position.

The construction of the arrestor is shown in more detail in Figures 2 and 3. The carriage 8 is guided on the same guides 3 as the cage by means of shoes 10 in conventional manner. Alternatively, the carriage may carry light guide rolls for engaging the guides 3 in a similar manner to the rollers 4 provided on the cage 1. At each end, out board of the shoes 10, the carriage 8 carries a frame supporting a set of three rollers 11, 12 and 13 each of which is mounted by means of a plain bearing on a respective shaft 14, 15, 16. Each end of each of the shafts 14, 15, 16 is secured in the appropriate one of the two plates or beams 8A, 8B making up the carriage 8. Preferably, the bearings are of the self-lubricating material type, for example, incorporating polytetrafluoroethylene.

As can be seen particularly in Figure 3, the middle roller 12 is offset in the horizontal direction from the upper and lower rollers 11 and 13. The strip 4 is thereby forced to bend around part of the upper roller 11 and then in the opposite direction around a larger portion of the middle roller 12 and then finally back around a portion of the lower roller 13 to return to the same plane as part of the strip above the rollers. Accordingly, as the carriage 8 is forced downwards, the rollers 13 and 12 and 11 perform successive bending operations in opposite directions on the strip through a sufficient angle to cause plastic deformation of the material of the strip during each bending operation thereby absorbing substantial amounts of energy.

Since each of the three curved bending surfaces is formed by a roller, the only significant frictional drag will be due to friction in the bearings between the rollers and their shafts and this can be held to a reduced, reasonably consistent value by appropriate design and choice of materials for the bearings and shafts which may for example be of stainless steel if it is preferred to leave the bearings dry.

In order to prevent any lateral oscillation of the strip 7 from varying the angles of wrap around the upper and lower rollers 11 and 13, it is preferred to provide the carriage with guide pins (or rollers) 17 and 18 which do not of themselves provide any material resistance to movement of the strip 4 past them.

As indicated in Figure 2, it may be found desirable to anchor the lower ends of the strip 7 to further cross beams 5. If deired, the strips 7 may be pre-tensioned although this will increase the proportion of the retardation forces which is due to friction in the bearings.

The blocks 9 on the carriage 8 (Figure 1) may be arranged to interfit with appropriate sockets in the under frame of the cage 1, so that the cage can then guide the carriage thereby dispensing with the need for the guide shoes or rollers 10.

In the arrangement illustrated in Figure 4, the cage 21 has two storeys and on each side of the path of the cage 21 two arrestor carriages 8 are mounted each on a pair of strips 7 having their upper ends attached to stub beams 22 supported on cross beams 23.

Rigid cross members 24 are secured to the top of the cage frame and project at each end outwards beyond the sides of the cage sufficiently to enable them to strike the arrestor carriages 8 on overshooting of the cage, the ends of the members 24 passing between the projecting ends of the stub beams 22.

The arrestor shown in Figure 5 is mounted in a horizontal plane in the position normally used for hydraulic buffers at the end of a length of track 31. The arrestor carriage 8 is supported (by mans of wheels or shoes, not shown) on the rails of the track 31. The strips 7 have their ends suitably secured in blocks or frames 32 and 33. The carriage 8 carries buffers 34 for engagement by the buffers 35 of a train 36.

In a variation of the arrangement shown in Figure 5, the strips may have their planes horizontal and be sufficiently slack to curve downwards from the carriage when the latter is in the position shown in Figure 5 and rest in an appropriate channel. The axes of the rollers 11, 12 and 13 will then be horizontal.

Finally, Figure 6 is a view corresponding to Figure 3, but showing an arrangement having five rollers 11, 12, 13, 25 and 26 which provide two further working operations on the strip, but with increased bearing friction in view of the larger number of rollers. It is necessary that the number of rollers should not exceed five (to avoid excessive friction), three rollers being considered sufficient for most applications. The arrangements shown in Figures 1 and 4 are for use at the lower end of the travel of the mine cage. At the upper end similar arrangements may be used, but suitably modified in that the arrestor carriages 8 would be mounted adjacent the anchored lower ends of the strips 7 in a position to be engaged by upward movement of the cage beyond its intended uppermost position. Furthermore, it may in some cases be practical to mount a complete arrestor on the cage so that the strips and carriage normally travel with the cage, but the arrestor carriage can be engaged with a fixed part of the shaft structure in the event of an excessive speed or overshoot occurring.

The cross-sectional dimensions of the strip may be varied to suit individual needs. The material of the strip should of course be ductile and non-brittle with metallurgical properties which are stable over a long period and for consistent reliable operation the state of annealing or work hardening of the strip should be checked on installation.

It will be appreciated that the carriages and strips take up little space within the shaft or other installation.

WHAT WE CLAIM IS: 1. An installation comprising a vehicle movable along a substantially predetermined path and an arrestor for stopping or slowing the vehicle in a portion of the path, the arrestor comprising a flat strip of ductile material extending in the direction of the path in which the arrestor is to operate, the strip being of width greater than thickness and of uniform thickness across its width, the strip being threaded through a set of not more than five rollers carried on a frame for plastic deformation of successive elements of the strip around the rollers when the strip is moved through the set of rollers during an arresting operation, each roller being rotatably mounted on the frame, each roller being rotatable about its axis by the strip when the strip is drawn through the set of rollers with alternate rollers in contact with alternate sides of the strip, the spacing between adjacent roller surfaces being greater than the strip thickness, the axes of all rollers in the set being fixedly located on said frame and with respect to each other, the rollers continuously maintaining a portion of the strip in a deformed condition and the maximum deformation of successive elements of the strip during relative strip-roller movement being constant irrespective of relative strip-roller movement, the strip extending substantially in the same direction along the path as it leaves the set of rollers, the arrestor being mounted on the vehicle or a stationary structure and having one of its frame and the leading end of the strip secured thereto, the other of the frame and strip leading end being engageable by the stationary structure or vehicle respectively as the vehicle reaches the said portion of the path.

2. An installation according to claim 1, including bearings supporting said rollers on the frame, the bearings ofthe rollers having a smaller radius than the strip engaging surfaces of the rollers.

3. An installation according to claim 1 or 2, wherein the bearings of the rollers comprise self-lubricating materials.

4. An installation according to claim 3, wherein the bearings incorporate polytetrafluoroethylene.

5. An installation according to any of the preceding claims, wherein the or each set of rollers has three said rollers.

6. An installation according to any of the preceding claims, wherein the strip is mounted on stationary structure adjacent the said portion of the vehicle path over which the retardation is to take place and the frame carrying the set of rollers is mounted on a carriage which can be engaged by the vehicle to be stopped or slowed.

7. An installation according to claim 6, wherein the carriage and vehicle are guided on the same guide.

8. An installation according to any of claims 1 to 5, wherein the strip in its straight form and the frame are carried by the vehicle with the rollers engaged with the leading end of the strip and means are provided for holding the frame when the arresting operation is required.

9. An installation according to claim 8, wherein the said means is in the form of a fixed projection in an overrun part of the vehicle path.

10. An installation according to claim 8, wherein the said means are velocity- or lackof-tension-sensitive and are arranged to extend latches or to fire explosive bolts into structure alongside the path of the vehicle.

11. An installation according to any of the preceding claims and including a pair of guide members for the strip, one guide member engaging the strip closely adjacent the point at which the strip meets the first roller and the other guide member engaging the strip closely adjacent the point at which the strip leaves the last roller, the guides engaging the strip on the side thereof opposite to the respective roller.

12. An installation comprising a vehicle and an arrestor for slowing or stopping the vehicle substantially as hereinbefore described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. properties which are stable over a long period and for consistent reliable operation the state of annealing or work hardening of the strip should be checked on installation. It will be appreciated that the carriages and strips take up little space within the shaft or other installation. WHAT WE CLAIM IS:

1. An installation comprising a vehicle movable along a substantially predetermined path and an arrestor for stopping or slowing the vehicle in a portion of the path, the arrestor comprising a flat strip of ductile material extending in the direction of the path in which the arrestor is to operate, the strip being of width greater than thickness and of uniform thickness across its width, the strip being threaded through a set of not more than five rollers carried on a frame for plastic deformation of successive elements of the strip around the rollers when the strip is moved through the set of rollers during an arresting operation, each roller being rotatably mounted on the frame, each roller being rotatable about its axis by the strip when the strip is drawn through the set of rollers with alternate rollers in contact with alternate sides of the strip, the spacing between adjacent roller surfaces being greater than the strip thickness, the axes of all rollers in the set being fixedly located on said frame and with respect to each other, the rollers continuously maintaining a portion of the strip in a deformed condition and the maximum deformation of successive elements of the strip during relative strip-roller movement being constant irrespective of relative strip-roller movement, the strip extending substantially in the same direction along the path as it leaves the set of rollers, the arrestor being mounted on the vehicle or a stationary structure and having one of its frame and the leading end of the strip secured thereto, the other of the frame and strip leading end being engageable by the stationary structure or vehicle respectively as the vehicle reaches the said portion of the path.