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June, 1944

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Due to the lack of confidence in the early types of iron and steel winding ropes, various devices were incorporated in the rope system to protect it from heavy strains, and a great deal of inventive genius was devoted to designing attachments to the cage with the object of gripping the guides in the event of the rope breaking.

It is convenient for these safety devices to be considered under three distinct periods. The first period consisted of cage arresters* which in practice proved unsatisfactory. None of these devices made any attempt to release the rope from the cage in the event of an overwind occurring. The second period in the development of safe winding was marked by attempts to provide for this eventuality. The general arrangement consisted of a detaching hook with a scissors mechanism which was normally prevented from opening by the weight of the cage; in the event of an overwind, a lever, which was a continuation of the detaching hook, struck a bar provided in the headgear, causing the scissors to open, and so permitting the rope to be pulled over the headgear pulley. At the same time steps were taken to prevent the cage falling to the shaft bottom. In the third period, which is still with us to-day, confidence is placed in the strength of the rope, which has, however, to be manufactured according to certain clearly defined specifications, the material employed in the construction having to undergo rigid tests to ensure desirable minima in regard to fatigue resistance, torsion, bending and tensile strength. Further safety has been ensured by affording higher factors of safety, daily examination and replacement of the winding rope after the specified time laid down by the Regulations. This confidence in the winding rope to undergo reversible stresses, the carrying of heavy loads at varying speeds, and the ability to undergo shocks without detriment, is due largely to the scientific investigations carried out on the effect of internal and external stresses in the rope, lubrication, the effects of acceleration and deceleration, the corrosion of the wire by acidulated waters, metal fatigue, rope oscillation, and the effect of gases on the rope in the upcast shaft. The only safety device incorporated in the rope system in the third period is the detaching hook, the purpose of which is to permit the rope to be detached from the cage in the event of an overwind.

The first detaching hook fitted to a winding system, not dependent upon safety devices in the event of a rope breaking, was introduced and patented by E. Ormerod in 1865; it acted by disconnecting the shackle from the rope, at the same time supporting the cage in a bell-mounted casting provided for the purpose in the pit headgear. The detaching hook was a scissors arrangement of three plates pivoted on a central pin; the upper ends of the plates were slotted and notched in such a way that the pin of the rope shackle in the normal position was firmly retained, accidental displacement being guarded against by a shearing pin passing through all three. The lower ends of the plates were spread out and had slotted holes, through which passed the pin of the shackle attached to the cage. When overwinding occurred, and the detaching hook was pulled into the fixed bell mouth, the expanded ends were forced together, thereby shearing the pin and releasing the rope shackle, but at the same time opening the plates at the top, causing the notched ends to overhang the bell mouth, so as to prevent the descent of the cage.

King's detaching hook, patented in 1867, and similar in action to Ormerod's, is illustrated in Fig. 1. The detaching hook consisted of two outside plates, enclosing between them two inner movable ones, which can oscillate about a strong pin passing through both plates and framework. The upper end of both these plates is made of uniform width except near the bottom, where two projections aa are fixed to prevent the hook from passing through the hole in the disengaging plate. The winding rope is attached to the top shackle d and the cage to the lower one e. When the two movable plates are placed on the central bolt b their upper parts close in opposite directions upon the connecting pin of the winding rope shackle and entirely overlap it, and in such position are secured by a copper pin c. In the case of an overwind, when the hook passes into the ring of the disengaging plate, the two projecting pieces aa are forced inwards, the copper pin sheared, and the jaws at the top forcibly separated from each other, thus releasing the shackle pin d; at the same time the two projecting pieces are forced outwards into the position ff, and prevent the cage dropping back.

This hook was improved by Messrs. E. G. Weddell, J. G. Chamberlain and R. Plaget, who took out patents in 1896 and 1900. In the modified detaching hook, two outer fixed plates on the opposite sides of the jaw were cut away, and the inner scissors-like jaws were thickened up so as to be flush, thus giving increased bearing area to the shackle. The scissors plates were also provided with two pairs of catches. In the event of an overwind occurring, one pair of catches begins to project simultaneously on to the opening of the scissors plates; should the overwind be completed the second pair comes into operation and obviates the shock and damage which would otherwise ensue in falling on to the catch plate.

An objection raised to the earlier Ormerod and King detaching hooks was that, being constructed of plates, there was a considerable amount of side friction, and unless they were regularly taken apart and oiled there was always the probability that the plates would firmly rust together and would therefore fail to act should the necessity arise.

Forster and Brindle also designed a detaching hook, an illustration of which is given in Fig. 2.

Messrs. T. Walker & Son introduced their well-known detaching hook (Fig. 3) in 1897. This is of a type using an entirely different principle from those previously described. In the Ormerod and King types the weight is utilised to prevent displacement, whereas in the Walker type the load is always endeavouring to cause detachment but prevented from doing so by a hoop encircling the hook. In its construction two levers aa are pivoted about the centre b and kept from opening under ordinary conditions by the collar c, held in position by the copper rivets d, which also provide an additional safeguard in that a tongue passes from one jaw to the other. When the hook enters the plate the collar is pushed downwards and the two rivets are sheared; at the same time the upper part of the jaws open, the winding shackle is released, and the suspension jaws are locked on the disengaging plate. Other detaching hooks were designed, but as they followed much the same lines as those described no useful purpose would be served by giving details; the most notable was that of Messrs. Ramsay and Fisher.

It can conveniently be stated here that the Mines Act of 1887 did not make the use of any overwinding appliance compulsory, but a limit of speed was fixed when men were being wound, if the mine was not provided with an automatic contrivance to prevent overwinding.

In practice, it was found that the rebound of the cage, after the detaching hook had performed its function in the case of an overwind, was to throw such a strain on the cage chains as to cause their collapse, thereby allowing the cage to drop, leaving the detaching hook suspended on its plate. To prevent this, Mr. Sebastian Smith designed an arrangement of catches in the headgear, which were closed under normal conditions, but which opened beneath the cage directly it had passed them. When these catches were open, their front faces projected in an inclined direction beyond the face of the headgear frame and terminated with projecting beaks. Consequently, when an overwind took place, and the cage chains failed to withstand the strain, the cage was caught between the inclined faces of the props, and possibly arrested by their wedging action; but should the cage continue descending in spite of the wedging force, and drop to the bottom of the inclines, it was then effectually stopped and supported by the beaks of the props.

Keps

In using the "clatch iron" during the winding of personnel, it was customary, when the rider arrived at the mouth of the shaft, for the winch handle to be made fast by a bolt drawn from the winch structure and the banksman to grasp the rider's hand and by main force bring him or her to terra firma. At a later date, when baskets or corves were utilised in bringing men or coal to the surface, it was usual for the shaft top to be covered by two folding doors, which were open during winding and then closed when the basket arrived at the shaft top. The basket was then lowered on to the doors thus permitting the men to alight in safety. Should coal be wound, the same procedure was adopted, except that the basket was removed from the rope and manhandled to a convenient place for unloading, being replaced by an empty one which was lowered after the doors had been opened. In some instances it was arranged that, after closing the doors, the basket swinging freely at the end of the rope was pulled to one side and the coal emptied into a suitable receptacle; it was then permitted to swing back before being lowered down the shaft.

The difficulty of handling the load at the surface was increased when cage guides were introduced by John Curr in 1788. The corve, which was attached to a bar riding in the guides, required a movable platform in order to enable it to land and its contents to be dealt with. Such an arrangement was cumbersome and wasted considerable time although mechanical contrivances were introduced later which overcame these drawbacks to some extent. However, even at their best it will readily be recognised that systems of this kind were very slow and were quite incapable of dealing with the larger outputs which were necessary before deep mining could become an economic proposition. This became especially apparent when T. Hall instituted the use of the cage for carrying tubs and men in 1834.

To protect the rope from damage and to facilitate loading and unloading of the cage it became essential to devise some means of supporting the cage during decking. For this purpose keps, keeps or shuts were designed. These supports, now commonly known as keps, were introduced in 1834-35, and originally consisted of hinged frames swinging inward under the cage and actuated by a lever. From this beginning the keps were gradually developed until they consisted of a series of four legs arranged in pairs on two sides of the cage, much as they appear to-day. They are pivoted on a shaft, Fig. 4, and are easily pushed aside by the cage on its upward journey but have to be moved out of the way by hand to allow the cage to descend. Nowadays their operation is made more easy by the use of counterbalance weights incorporated in the system. Another arrangement consists of a series of projecting bolts arranged in the main timbers at the pit top, and pressed outwards by springs, the bolts being made to return to their original position by means of levers. These were not so suitable for heavy loads as the previous type; moreover, wear was considerable, and a great strain was thrown on the frame at the pit top.

A great advance was made by the simple and ingenious arrangement of keps designed and patented by Stauss in 1844. Haniel and Lueg have also designed keps of a similar type. Essentially this apparatus, Fig. 5, consists of two shafts a and b fixed in bearings, and legs c upon which the cage rests at the end of the wind. The latter are threaded upon a shaft d, which is free to swing, but which is attached by a link to the shaft a. The shaft d is connected to b by a toggle joint lever ef. A glance at diagram A will show that it is impossible for the props c to slide in a horizontal direction, as the two levers ef prevent such motion, but they permit the cage to pass through when arriving at the pit top, for being loose on the shaft d, they rotate about their axis, and take the position shown by the dotted line, dropping back into their normal position as soon as the cage has passed. To lower the cage, the banksman pulls over a lever which moves the link g and rotates the shaft b. This lifts up f until the point h is a little above the straight line joining d and b. Immediately this takes place the weight of the cage forces the props c to slide on an incline plane i, which has a slope of about 9° The whole apparatus then takes up the position shown in B.

The advantages gained by this system were :–

(1) No complicated parts.

(2) One reversal only of the winding engine necessary, that is, immediately the cage is brought to bank, the direction of the movement being always afterwards a lowering one.

(3) Less wear and tear on the ropes, since lifting of the cage to release the keps is unnecessary.

(4) Great saving in time during decking, amounting to 3 to 6 seconds for each lift, according to the skill of the engineman, with single-deck cages; with cages of several decks the saving is more or less in proportion.

(5) Wear on the keps infinitesimally small and nothing to get out of order.

With the ordinary form of keps the cage cannot descend without first being lifted by the engine, since the weight on them prevents the banksman from withdrawing them. As an example, in the event of a three-deck cage being used, and each deck changed independently, it is necessary to reverse the engine seven times, each deck requiring two, and the final lowering of the cage another.

In addition to using Stauss keps, Continental mining engineers have experimented with hydraulic types. There is a description in the Lehrbuch der Bergbaukunde by G. Köhler of an apparatus designed by Frantz in 1884. This arrangement consisted of four plunger cylinders e (Fig. 6A) provided with stuffing boxes and pistons connected together by wrought iron tubes. Each plunger was provided with a double lever g having its turning point on the piston itself. The end of the lever projected under a fixed pin i, the other serving as a support to the bottom of the cage. Water in the accumulator k enables the piston and double lever to rise. The ascending cage m lifts the front end of the lever g upwards (diagram B), which on account of its own weight falls back into a horizontal position immediately after the cage has passed. When the cage rested on the legs, it was supported by the water in the piston, the connection between the plunger cylinder and the accumulator being cut off by means of a valve. When the cage had to be lowered, the valve was opened and the weight of the load pressed down the plunger, forcing the water into the accumulator until the lever g assumed the position indicated in diagram C. Immediately the cage had descended, the accumulator again forced the piston and lever into the higher position and the valve was closed.

Other keps adopting the same principle were evolved, but owing to the complicated form of apparatus and the use of water which froze in cold weather (although this disadvantage was overcome to some extent by introducing glycerine into the rams and accumulators) hydraulic keps never became popular, especially in this country.

It was early found that when using keps it was essential to have the length of the rope carefully adjusted, so that the cage did not fall back after drawing back the keps. The sinking of the cage should not amount to more than the slack of the rope when unloaded.

Before the present types of rope were used for winding, this difficulty in obtaining the correct length of winding rope for use with keps was overcome by Freudenberg's cage-adjusting hangers, the action of which is clearly illustrated in Fig. 7.

* See January, 1944, issue

(To be continued.)

Drawings and Photographs accompanying the article