GB2025363A - Drop back catch assembly - Google Patents

Abstract

A drop back catch assembly for a vertical lift cage (7) or similar conveyance reduces the weight normally carried by the cage by coming into operation only when the cage travels above the upper limit of normal travel. A rack (11) having opposed sets of teeth is disposed adjacent the overrun path of the cage, mounted on a rack post (3) itself mounted to thrust back beams (4) which extend horizontally across the lift shaft. A catchblock assembly (1) has rollers (12) and travels in roller channels (13) carried by supports (14) mounted on the thrust back beams. A double set of pawls (8) engages with the opposed teeth of the rack 11 allowing only upward movement of the catchblock assembly with respect to the rack. A lip (15) and ledge (16) extending from the catch block engage with an engagement catch (17) on the cage only when the cage travels above a predetermined position, whereupon the cage carries the catchblock, and the rack and pawls provide a drop back catch action preventing the cage from falling. The catchblock and cage are thus interengaged only in the event of drop back protection being required. The ledge (16) may be on a pivoted latching hook (18a). <IMAGE>

Description

SPECIFICATION Drop back catch assembly This invention relates to drop back catch assemblies for vertical conveyors such as lifts, mine cages and mine skips, and to a vertical conveyor and shaft therefor equipped with such an assembly.

The conveyor assembly is provided with winding means to control the ascent and descent of the conveyance (hereinafter for convenience called "the cage", which expression is used to include any type of conveyance moveable in a shaft). In the event of the cage being moved beyond the normal upper limit of travel, means must be provided in order to hold the cage and prevent its uncontrolled descent in the event of its becoming detached from the winding cable. To achieve this end, it is known to have catches mounted on the sides of the cages and racks mounted beside its path of movement, or vice versa. See for example our pending UK application No. 49267/76 (Serial No.

The weight of that part of the catch assemblies of the prior art which has to be borne by the cage represents a considerable weight to be carried, considering that it is only on the rare occasions when the cage becomes overwound that the catch assembly is operational.

The present invention avoids the neccessity of having this considerable weight on the cage by mounting the complete drop back catch assembly upwardly from the cage, adjacent the path which would be taken by the cage should it overrun its normal limit of travel, with provision for the cage to engage the catch assembly when it overruns so that the drop back prevention action of the catch comes into operation.

Thus according to the present invention there is provided a vertically disposed member located adjacent the path taken by the cage should it overrun its normal upper limit of travel and a catchblock arranged to run in a path adjacent said vertically disposed member, said vertically disposed member and said catchblock having cooperating engagement means which allow upwards movement of said catchblock with respect to said vertically disposed member but prevent such downwards movement, there being provided interengaging means between the cage and the catchblock such that should said overrun occur the cage engages the catchblock and carries it upwardly along said path, and holding means on said catchblock which on engagement of the catchblock assembly with the cage hold the cage to prevent its uncontrolled descent.

Preferably, said vertically disposed member is a rack located parallel to the overrun path of the cage and said engagement means comprises teeth on said rack and catches mounted on said catchblock which engage with said teeth, in which case the rack may extend vertically through a slot in the catchblock so that the rack itself acts as the guide means for the vertical movement of the catchblock.

Alternatively, said catchblock includes a rack and said engagement means comprise teeth on said rack and catches mounted on said vertically disposed member which engage with said teeth.

In this way the invention provides effective drop back protection for the cage in the event that such protection is required without the need for the cage to carry heavy machinery throughout its normal travel.

In one form of the invention the catchblock assembly has a ledge or platform which fits under the bottom of the cage, the guide means being angled near its bottom end so that in the parked or resting position of the catchblock the ledge it out of the path of travel of the cage. When the upward movement of the cage pulls the catchblock assembly up beyond the angled portion of the guide means, the ledge is brought under the cage.

In another preferred form of the invention the catchblock engages the cage by means of a latch mechanism, there being at least one displaceable latching element on the catchblock which element is biassed, by gravity and/or suitable resilient means, into the path of upward movement of the cage and is arranged to be displaced by the cage upon such upward movement whereafter the latching element is returned by said bias so as to catch beneath an element on the cage to hold the cage against subsequent descent. Suitably the latching element is in the form of a hook and is pivotally mounted to swing into and out of the path of movement of the cage, the underface of the hook providing a cam surface which is engaged by the cage to push the hook aside.

Preferably the upper face of the hook which catches the cage is below a downward facing surface of the catchbiock which is engaged by the cage during upward movement in order to entrain the catchblock upwardly.

An especially suitable arrangement of rack and pawls for use in the invention is that described in our copending UK application 10931/78 (Serial No. ) but the invention is not limited thereby.

In a further, preferred form of the invention, the rack extends vertically through a slot in the catchblock so that the rack itself acts as the guide means for vertical movement of the catchblock.

This eliminates the need for separate guide means and therefore simplifies the construction.

There can be provided a plurality of racks, for example one parallel to and adjacent the position of each corner of one end of a rectangular cage in the event of an overrun and a catchblock which engages with both racks. With this arrangement, the catchblock does not substantially obstruct access to the cage at that end so that in the event of an overrun escape from the cage through that end is possible. The racks should be suitably held in position by location means at points above and below the path of movement of the catchblock.

Preferably means are provided in order to retract the pawls so that the cage can be released from its overwind position.

These means may include, for example, a hydraulic piston system which can be operated by means of a portable head unit.

The rack or racks may be resilientiy supported to allow limited vertical movement, providing a cushioning of the loads when a cage is "caught" by engagement of the catchbiock and rack or racks. There may also be provided a buffer member connected to the interengaging means between the cage and the catchblock, the resilience of which can assorb the shock produced when the cage picks up the catchblock at the begining of an overrun.

Particular embodiments of the present invention will now be described by way of example, with reference to the accompanying drawings wherein: Figure 1 shows a section through a mine shaft, showing two cages, one in an overwound position engaged with the catchblock assembly and the other one on the point of engaging with the catchblock assembly; Figure 2 shows a vertical section through the racks, pawls and guide means; Figure 3 shows a horizontal section through the catchblock assembly and mounting beam; Figure 4 is a side view part of another drop back catch assembly according to the present invention; Figure 5 is a front view of the drop back catch assembly of Figure 4, seen in the direction of the arrow V of Figure 4;; Figure 6 is a sectional view of the drop back catch assembly of Figure 4 taken across the line VI--VI in Figure 5; Figure 7 is another sectional view of the drop back catch assembly of Figure 4 taken across the line VIl-VIl in Figure 5; Figure 8 is a side view of another embodiment of the drop back catch assembly according to the present invention; and Figure 9 is a front view of the drop back catch assembly if Figure 8 taken in the direction of the arrow IX; Figure 10 is a side view of a further embodiment of the drop back catch assembly according to the present invention; and Figure 11 is a front view of the drop back catch assembly of Figure 10 taken in the direction of the arrow Xl.

Figure 12 is a vertical section through the rack post and drop back catch gear of a further embodiment of the drop back catch assembly according to the present invention, together with part of a mine cage; Figure 13 is a side view of the rack post and drop back catch gear of Figure 12; Figure 14 is in more detail the catch assembly of Figure 13; and Figure 1 5 is a section along the line XV-XV in Figure 14.

Figure 1 6 is a front view of another embodiment of the drop back catch assembly according to the present invention; Figure 1 7 is a sectional view of the assembly of Fig. 16, taken on the line XVll-XVll and Figure 18 is a sectional view of the assembly of Fig. 16 taken on the line XVIII--XVIII.

Figure 1 of the drawings shows two cages which have overrun their normal upper limit, in conjunction with an embodiment of drop back catch assembly according to the present invention. If there are two cages, the drop back catch assembly is duplicated and one of these will now be described.

To the side of the line of travel of the cage are located thrust back beams 4 which support two posts 14, each bearing a roller channel 13 which face towards each other, as best seen in Figure 3.

At their lower ends the two roller channels are angled and diverge away from the path of travel of the cage.

Centrally between the upper vertical part of the two roller channels 13 is located a double sided rack 11 facing outwardly towards these channels, the rack being held on a rack post 3 mounted in a channel faced with brass strips 10 in a guide bracket 5 secured to the thrust back beams 4. The rack post 3 is resiliently mounted, for example on ring springs (not shown), in order to adsorb the initial shock when the pawls hit the rack.

A catchblock assembly 1 having four rollers 12, two on each side, travels within the roller channels 1 3. The left-hand side of the Figure 1 shows the lower "resting" or "parked", position of the catchblock assembly. As seen in Figure 1, the catch block assembly is provided with an engagement lip 1 5 which lies in the path of an engagement catch 1 7 on the cage, so that as the cage travels upwards, the catch 17 fits under the engagement lip 1 5 and carries the catchblock assembly upwards into operational engagement with the rack. The engagement lip 1 5 and/or the catch 1 7 may be resiliently mounted in order to reduce the initial shock as the catchblock assembly is picked up by the cage.The shape of the catch 17 and the lip 15 is such that the cage is prevented from swinging outwardly away from the catchblock assembly, as seen in Figure 1. As the catchblock assembly moves upwards and the rollers 12 enter the vertical parts of the roller channel 13, a ledge 1 6 forming the upper end of a bracket 1 8 swings round under the bottom of the cage 7 and thus supports it.

The catchblock assembly 1 is provided with a series of pawls 8 which ride up past the racks 11 and which are biassed outwardly so that downward movement of the catchblock assembly, and therefore of the cage which is now resting on it, is prevented. The spacing between successive pawls and the spracing between successive teeth is preferably arranged so that the fali back, that is, the distance through which the cage may drop before the engagement of the pawls with the teeth prevents downward travel of the cage, is less than the distance between successive teeth on the rack. The pawls and rack may be constructed in the manner described in our copending application No. 10931/78, but the invention is not limited thereby.

In Figures 4 to 7 there can be seen an embodiment of the invention, wherein there are provided two catch means for each catchblock, each catch means comprising a lip 1 5 and a hookshaped latch section 1 8a having a ledge 1 6a, and pivotable about a pivot 19. The lip 1 5 and pivot 19 are fixedly mounted on vertical members 24, which are connected to bars 21 and 22, running in the channels 13. The bottom bar 21 normally rests on end stops 23. Also mounted on the members 24 is the straining plate 20, upon which are mounted a plurality of pairs of pawls 8, facing each other. Located between the channels 13, is the rack 11, which has two opposed sets of teeth (or a configuration which effectively provides two such sets) with which the pawls interact.

Should the mine cage overwind, projection 17, conveniently one of the reinforcing loops running around the side of the cage, rides over the angled side of latch section 1 8a, forcing it outwards until the bottom edge of the projection 1 7 has passed beyond the ledge 1 6a, whereafter the latch section 1 spa swings back down under gravity into its vertical position. Thus upward movement of the mine cage causes the upper side of the projection 1 7 to hit against lip 15, thus carrying the catchblock upwards; attempted downwards movement of the cage causes the lower side of the projection 1 7 to be retained by ledge 1 6a. As the catchblock is carried upwards, the pawls 8 ride up over the teeth of the rack 11.Attempted downward motion causes the pawls to interact with the rack, and thus downward movement of the catchblock and hence the cage, which is resting upon ledge 1 6a, is prevented.

Conveniently the catchblock is in normally a "parked" position in which the pawls are already interacting with a lower portion of the rack, and thus guide means to direct the pawls into alignment with the rack are not required.

A further embodiment of the invention will now be described with reference to Figures 8 and 9.

The same reference numerals are used as for the corresponding parts in Figures 4 to 7, and the operation of the assembly is as previously described. The main difference in this embodiment is that the latch section 1 8a is so shaped that even when it is pivoted outwards to its furthest extent (by the action of the projection 1 7 passing over its inner angled side 1 8b), it does not extend outwards beyond the plane defined by the outer edges of the channels 13. To compensate for the reduced mass of the latch section 1 8a a spring 25 is provided between the latch section and the fixed lip 1 5 to effect positive return of the latch section to its vertical position as soon as the lower edge of the projection 17 has passed over the lip 16a.

The latch assemblies and the catchblock are conveniently mounted in a frame 26, which runs in channels 3 mounted to coincide with the outer edges of the frame.

Preferably the configuration of the frame is such that the pawls are in engagement with the rack even when the drop back catch assembly is in its parked, non-operative position. Also the distance between the latch mechanism and the bottom of the frame is preferably such that when the top hoop of the mine cage engages with the latch mechanism, the middle hoop is about level with the bottom of the frame; this limits the forward and backwards movement of the cage.

The embodiment of Figures 8 and 9 has the advantage inter alia, that no clearance is required behind the guide channels for the latch mechanism to operate in.

Although the embodiment have shown the pawls mounted on the moveable part of the drop back catch assembly and the rack fixed, the invention applies equally where the moveable part of the drop back catch assembly is provided with a rack or racks, and the pawl mechanism is fixed.

The drop back catch assembly depicted In Figures 10 and 11 is generally similar to that of Figures 8 and 9, the same reference numerals identifying corresponding parts. The difference is that each latch 1 8c on the moveable frame 26 is pivoted about a pivot 1 9c which is located at the lower end of the latch, rather than the upper end of the latch as in the embodiments described above. The latch is resiliently biassed against a stop 27 on the frame 26 by a compression spring 25c.As the projection 1 7 e.g. the upper cage hoop, on the cage engages the inclined edge 1 8d of the latch, the latch is forced up against the spring, thus allowing the projection 17 to pass into a position such that it occupies the space between the fixed lip 1 sic and the top face 1 6c of the latch 1 8c which returns to its rest position under the action of the spring. The catch and pawl assembly can then function as previously described. In this embodiment also, the pawls 8 are always in engagement with the rack 11.

Figures 12 to 1 5 show an embodiment of the assembly in which there is a plurality of rack posts which themselves act as guide means for the catchblock.

Figure 12 shows part of a cage which has overrun its normal upper limit of travel. Commonly there are two cages per mineshaft, and therefore two sets of overwind safety catch gear. The following description will however just refer to one cage. The cage is rectangular in plan, normal access, at least for men, being at the narrow ends.

The cage has a top hoop 103 and some way below an intermediate hoop 104.

Above the normal upper limit of travel of the cage 101 there are mounted four.rack posts 105, one adjacent each corner of the cage when overrunning (only two of the posts 105 can be seen in the Figures: these two are at one narrow end of the cage). The rack posts 105 have racks in the form of rows of teeth on their opposed edges (see Figure 14). The two posts 105 at one end of the cage are suspended from a cross-beam 1 15 which is supported by two compressible buffers 1 17 (these may be similar to railway buffers, upended, or may be ring springs, springs of the oilpneumatic type of rubber blocks).The buffers 11 7 are carried by beams 11 6 extending transversely to the cross-beam 11 5 and supported at their ends (not shown) in a manner which allows them to lift a little (e.g. 5 cm) for a reason explained below. The cross-beam 11 5 is normally held by the buffers 11 7 against a fixed member 118, but is not attached to the member 118 so that when the cage is caught by the catchgear, the buffers can give resiliently allowing the posts 105 to descend a little. This cushions the shock.

At their lower ends the racks pass through guide slots in a cross-member 107, which keeps them in position. These slots are preferably brasslined.

A catchblock 104 is mounted to slid along the two posts 1 05. There are two such assemblies, one at each end of the cage 101. As will be described below, the posts 105 act as guides for the catchblocl < 104, which normally rests on the cross-member 1 07. The catchblock has a frame composed of vertical members 112, 114 and cross-members 109, 110, 111. As Figure 12 shows a top cross-member 111 projects into the path of the overrunning cage 101, so that it is struck by the hoop 103 and the whole catchblock 104 is carried upwardly by the cage along the racks 105.

A wooden bumping beam 113 is provided above the cage 101, to limit upward travel. This beam 11 3 is fixed to the underside of a crossbeam 11 6a attached to the beams 116. As the beam 11 6 can lift a little (see above), the shock of the cage striking the beam 11 3 is cushioned by the buffers 11 7. The buffers 117 thus have two functions (see above).

As Figures 14 and 15 show, the frame members of the catchblock carry brass liners 1 33, so as to provide a slot, closed on three sides by brass, through which the racks posts 105 pass.

The use of brass is intended to avoid the rusting of the rack posts solid with the catchblock, while the clearance between the liners 133 and the posts 105 is such that the posts guide the catchbiock when it is entrained upwardly by the cage.

The catchblock which is shown in more detail in Figures 14 and 15, comprises two sets of pawls 11 9, mounted in back to back relationship, facing outwards, so as to be able to interact with the rack, and a plurality of latches 121, 123, mounted between the sets of pawls 11 9, which engage the hoop 103 of the cage.

The pawls 119 are mounted on pivots 127, and are resiliently biassed outwards. The spacings between successive pawls and between successive teeth on the rack are different so that a vernier arrangement results, whereby the movement of the drop back catch assembly, required to give positive engagement ofa pair of pawls (one on each side) with the rack teeth, is less than the distance between successive teeth on the rack.

There are provided two pairs of latches to engage the hoop 103; an upper set 123 and a lower set 121. These are mounted on pivots 129, and 127 respectively. In use, when the cage 101 overwinds, the upper hoop 103, or other suitable projection on the cage, rides up against the lower surface of the latches, forcing them outwards.

Further upward motion of the cage relative to the catch block is prevented by the upper surface of the hoop 103 hitting against stop 111. Once the hoop has passed over them, the latches move back, by the action either of gravity or resiiient means or both, and the hoop is thus trapped between the latches and the stop 111. it is intended that the hoop is retained by the upper set of latches 123, the lower set 121 serving to retain the cage should the upper set fail.

Continued upward motion of the cage carries the drop back catch assembly with it, the pawls 11 9 ratcheting over the teeth of the racks.

Then upward motion of the cage and drop back catch assembly cease, the drop back catch assembly, and therefore the cage, are prevented from moving downwards more than a few centimetres by a pair of pawls engaging with the teeth of the racks. The shock as the pawls engage is adsorbed by the buffers 11 7. The cage is thus held, being supported on the latches 123 or 121 if the former have failed.

The catchblock is always parked, with its pawls in engagement with the rack teeth, ready for operation. Thus problems of registration of the teeth and the rack are avoided.

Another advantage of this embodiment if that again no modification of the cage is needed; thus no extra weight is carried up and down the mine shaft in normal operation.

The lower transverse member 110 is horizontally opposed to the intermediate hoop 104, when the cage is engaged with the catchblock. This stabilizes the cage and prevents it swinging against the racks 105 themselves.

The location of the racks 105 at the corners of the cage means that practicaliy the whole of the space between the members 109, 110 in the catchblock is unobstructedly available for escape from the cage, after the cage has been caught by the catchgear.

Figures 16 to 18 show an embodiment in which the carriage 200 has a frame composed of vertical members 210, 212, 214, 216 and cross members 218, 220. The outer vertical members 210, 212 carry pawls 222 (shown on the left hand member, 210, in Figure 16) which engage with teeth on rack posts 205 and also have guide means 207 (shown only on the right hand member, 212, in Figure 16) which co-operate with catch plates 209 on the racks 205. For the sake of clarity both guide means 207 and catch plates 290 are omitted from the left hand side in Figure 1 6.

The two inner vertical members 214 and 216 are of C-shaped cross-section and are the guide rails on which slides a guide member 230 to which are attached two vertical plates 232, 234.

A hook 240 is mounted between these two plates at a pivot point 241. The plates 232, 234 each have a lug 235 shown in Figure 1 7 and the two lugs 235 are connected vertically to a piston rod (which is encased in a compressible jacket 236) of a spring buffer member 237 fixed to the vertical members 214,216.

As the cage travels vertically upwards beyond its normal upper limit of travel, a laterally extending hoop of the cage strikes the upper lip of the hook 240, pivoting it upwards so that the hoop is held by the hook 240, as shown by dotted lines in Fig. 1 7. When the hoop hits the lower edges of the lugs 235, these are moved upwards so that the shock of the impact is adsorbed by the buffer 237. The uppermost end of the hook 240 is shaped so that on pivoting of the hook by the cage hoop pushes past a pin 250 which is held in slots in the two plates 232, 234, the pin being biassed by the springs so as to move down and prevent return of the hook.

As is seen in Figure 17 the hoop is shaped to correspond with the side of the recess in the hook.

The resilience of the buffer in this embodiment allows a movement on initial impact of 140 mm and also allows a movement of 40 mm to provide a buffing action on fail back of the cage.

Considerable advantages may be obtained with the catch assemblies of the invention. The catchblock is only picked up by the cage in the unusual event of an overwinding of the cage so that the weight oi the catchblock assembly, which can be quite considerable, is not normally carried by the cage. This may represent a considerable saving on the cost of running the lift system.

in addition, very little space is taken by the assembly of the invention especially when it includes the latch shown in Figures 8 and 10 where no part of the catchblock assembly extends beyond the plane defined by the running channels for the catchblock.

Furthermore, in the embodiments where, for example, the catchblock assembly is designed to engage with a laterally extending beam of the cage, no modification or alteration of the cage is necessary on fitting the drop back catch. This obviously results in economy and ease both of fitting and of maintaining the mechanism.

Claims (9)

1. A drop back catch assembly for vertically movable conveyor or cage having a vertically disposed member located adjacent the path taken by the cage should it overrun its normal upper limit of travel and a catchblock arranged to run in a path adjacent said vertically disposes member, said vertically disposed member and said catchblock having cooperating engagement means which allow upwards movement of said catchblock with respect to said vertically disposed member but prevent such downwards movement, there being provided interengaging means the cage and the catchblock such that should said overrun occur the cage engages the catchblock and carries it upwardly along said path, and holding means on said catchblock which on engagement of the catchblock assembly with the cage hold the cage to prevent its uncontrolled descent.

2. A drop back catch assembly according to claim 1 wherein said vertically disposed member is a rack located parallel to the overrun path of the cage and said engagement means comprises teeth on said rack and catches mounted on said catchblock with respect to said vertically disposed

3. A drop back catch assembly according to claim 1 wherein said catchblock includes a rack and said engagement means comprise teeth on said rack and catches mounted on said vertically disposed member which engage with said teeth.

4. A drop back catch assembly according to claim 2 wherein the rack extends through a slot in said catchblock so as to act as a guide for vertical movement of the catchblock.

5. A drop back catch assemblyaccording to any one of claims 1 to 4 wherein said interengaging means includes a lip extending from said catchblock and a hook extending from said cage, said hook engaging said lip on upward movement of the cage past its normal upper limit of travel.

6. A drop back catch assembly according to any one of claims 1 to 4 wherein said interengaging means includes a latch member having a lip and a hook-shaped latch section, said latch member being pivotally mounted on said catchblock and arranged to co-operate with a laterally extending portion of said cage such that on upwards movement of said cage said laterally extending portion engages said latch member between said lip and said hook-shaped latch section.

7. A drop back catch assembly according to any one of the preceding claims wherein there is provided a resilient member connected with the interengaging means between the cage and catchblock said resilient member providing a buffering action to adsorb shock produced on interengagement of the cage and catchblock.

8. A drop back catch assembly essentially as herein described with reference to and as shown in the accompanying drawings.

9. A vertical conveyor fitted with a drop back catch assembly according to any one of the preceding claims.