Note: Descriptions are shown in the official language in which they were submitted.
This invention relates to arrestors for vehicles,
such as mine cages, trains, aircraft and ships, such arrestors
comprising a length of deformable tensile material and a
device defining a non-straight path through the device for
the length of ductile materialt When the device moves
longitudinally rela-tive 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 non-straight 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 i9
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 70 years. French
Patent Specification No. 328841 of 1903 discloses a pair of
arrestors to be mounted one on each side of a lift shaft. Each
arrestor consists of four cables on which are engaged a
plurality of arresting devices comprising transverse vertical
plates carrying pegs arranged in three vertical spaced rows,
the pegs in the middle row being aligned with the spaces between
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the pegs in the upper and lower rows and the diameter and
spacing of the pegs is such that each wire ...... ~
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rope is constrained to ~ollow a non-straight path past the pegs
of the middle row and just fits in the gaps between the peg
of the middle row and the adjacent pegs of the upper and lower
rows. Each peg of the middle row has two wire ropes in contact
with it. In the event of overspeeding of the lift cage, a claw
extends from the latter and engages the plate of the arrestor
device, the intention being that the latter is moved downwardly
along the wire ropes against the drag exerted by the ropes as
they are pulled through the non-straight paths and past the
pegsO British Patent Specifications Nos, 19623 of 1901 and
25469 of 1904 both describe arrangements for arresting a mine
cage in the event of breakage of the winding rope. The cage
is guided by four guide ropes each o~ which passes between a
pair of rollers carried by a lever arm pivoted to a corner
of the cage. If the winding rope should break or otherwise
lose tension, the lever arms are tilted by springs and by the
downward movement of the cage relative to the guide ropes into
a position in which the rollers "bind" the guide ropes by
forcing the latter to adopt a doubly bent configuration.
All such devices relying on deformaticn of wire ropes,
operate very largely by friction. While energy is absorbed
by doing work in bending and straightening successive portions
of the ropes, this work is absorbed in overcoming friction
between the individual wires of the ropes. Their performance
is -therefore unpredictable since the various coefficients of
friction will vary with the state of the various surfaces
for example in accordance with the amount of oil or grease and
rust on the ropes.
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More recen~ly, arrestors have been proposed in
U.S. Patents Nos. 257g753r 2979163, 2980213, 3017163, 3211260
and 3377044 in which a coil of strip is contained in a housing
and has i-ts 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 to 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 results in high friction and thus possibly inconsistent
operation if the device has been neglected for many years
while at the same time the inevitable bul~ 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 re~uire impossibly
massive and heavy installations to support and guide the strip.
Figures 1 and 2 of Belgian Patent Specification No.
477757 show an arrestor supporting a lift cage and comprising
a pair of strips having their upper ends fixed to transom fixed
to the lower end o the lift cable while an adjacent part of
each strip passes down through a guide carried by the lift cage.
The upper end of each guide defines an S-shaped path for the
strip partly by means of rollers and partly by curved guide
surfaces in frictional contact with the strip. Accordingly,
the retardation exerted by the arrestor will vary to a great
extent in accordance with the state of the guide surfaces and
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the strip surfaces. ......................................
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Accordingly, for the various reasons set out above,
none oE these known arrestors has been widely used for
arresting vehicles.
According to the present invention, there is providea
an arrestor for stopping or slowing a vehicle in a portion of
a substantially predetermined path for the vehicle, the
arrestor comprising a flat strip of ductile material extending
in the direction of the path in which the arrestor i.5 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 contin-
uously deforming the interposed strip portion by a constant
amount 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 leadîng end being engayeable by
the stationary structure or ~ehicle respectively as the vehicle
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reaches the said portion oE the path.
With this arrangement, a major part of the
retardation ~orce 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-
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lubricating materials ior the bearings, for example bearings incorporating
polytetrafluoroethylene. Alternatively, bearings of hard aluminium alloy
with perhaps a smear of lubricant may be used.
By keeping the number of rollers in each set small, ~4~m~
not more than five and preferably three, the contribution of friction
to the retardation, for example in the bearinys of the rollers is also
reduced. By having an odd number of rollers, the emerging strip can be
coplanar with the strip entering the set of rollers, thereby helping
to ensure that the angle of wrap of the sitrip with each roller can be
maintained constant.
In one îorm of embodiment the strip is mounted on stationary
st,r~cture adjacent the part of the vehicle path over which the retardation
is to ta~e place, for example ahove the normal upper position of the lift
cage in a mine shaftO The frame or frames carrying the sets of rollers
is then preferably mounted on a light carriage which can be engaged by
the cage or other vehicle on overwincl or overshooting. Advantageously,
where the vehicle to be arrested has guides for example ropes or rails,
the carriage is itselE guided on these guidesO
rn another form of embodlment, the strip in its straight form
~s carried by the vahicle with the rollers engaged with the leading end
of the strip and a suitable device i9 provided for engaging the roller
frame when the arresting operation is re~uired. ~'his device may be in the
fo~ of a iixed projection ~n an overrun part of the vehicle path or a
velocit~-or-lac~ of-tension-sensitive device arranged to extend latches
~5 or t,o fire explosive bolt~ into structure alongside the path of the
vehicle~
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Where the strip cross-section is cons-tant 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 during movement
along the strip path so as to accommodate vehicles where the
load carried by the vehicle may appreciably vary. Conveniently,
the variation in strip cross-section may be 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
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guide ra.ils 3 ~ the cage :Eor this pwXpose CAxx~n~ sets ~
guide wheels 4 at its upper and lower ends~ . ~,,, .,,, ~, ......
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On each side of the path of the cage 1 a cross beam 5
has its two ends firmly embed~ed in and supported in the lining
(not shown) of the mine shaft. The ~uides 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 cross-section,
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 over-
shoots its lowermost position.
The construc-tion of the arrestor is shown i.n more
detail in Figures 2 and 3, The carriage 8 i5 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 set of three rollers 11, 12 and 13
each o~ which is mounted by means of a plain bearing B 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 B are of the self-lubrica-tlng 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
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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 at 12 and ll perform successive bending
operations in opposite directions on the strip through
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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 bet~een 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 ~f 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 themsel~es provide any material resistance to
movement of the strip ~ 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 50 If desired, the
strips 7 may be pre-tensio-r.ed although this will tend to increase the
proportion of the retardation forces which are due to friction in the
bearingsO `
The blocks 9 on the carriacge 8 (Figure ~ 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 ~ 7 having their upper ends attached
to stub beams 22 supported on cross beams 23. ~iigid 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 en~ble them to stri~e the arrestor
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carriages 8 on overshooting o~ the cage~ the ends of the
members 2~ passing between the projecting ends of the stub
beams 22.
The ar~estor shown in Figu~e 5 is mounted in a
horizontal plane in the position normally used for hydraulic .
buffers at the end cf a length of track 31. The arrestor
carriage 8 is supported (by means of wheels or shoes (not
shown)) on the rails of the txack 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 arrangemen~ 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 in general desirable
that the number of rollers should not exceed five (to avoid
excessive friction), three rollers being considered sufficient
for most applications. The arrangement shown in Figures 1 and
~ are for use at the lower end of the travel of the mine cageO
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
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its intended uppermost position~ Furthermore, it may in some
cases be practical to mount R 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
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