to the cage and the full ones off, the pushing rods are supported by rollers and are attached to a vertical travelling beam running on rails which is connected through struts and a rocking lever to an oscillating hydraulic ram. In this way all the pushing rods are bound to move forward at the same instant and with equal speed. Under the old arrangement, it was found that as each ram was independent, they frequently travelled at varying speeds owing to the possible existence of a leaky valve, or a tight cup leather in the stuffing box. The pushing rams are withdrawn by a balanced weight immediately the winding cage has been loaded.

The time occupied in changing the eight tubs on the four decks of the cage is about five seconds. As soon as this has taken place, winding recommences, and while this is going on the subsidiary hoists at the front and back are lifted simultaneously, the former to be filled with empty trams ready for the next arrival of the drawing cage, and the latter to discharge its load of full tubs.

It should be noted that with this arrangement the hydraulic machinery has to be powerful enough to lift the subsidiary hoist and its complement of full tubs, because the winding engine only brings the top deck of the main cage up to screening level.

Tomson's Apparatus.-This arrangement is also a modification of Fowler's idea, but designed to require less motive power to work it. Subsidiary cages in front and at the back of each winding cage are employed, but the two in front are suspended by a common chain passing over a pulley, so that one ascends while the other descends. The back pair are similarly arranged, and all are supported by rams which move in hydraulic cylinders. These cylinders are arranged that the forward one on the right is in connection with the back one on the left, while the other two are also connected crosswise. The connection pipes pass through a controlling apparatus so constructed that: :

(1) Two opposite lying cylinders may be placed in direct communication and the passage of water from one into the other regulated to control the speed of motion.

(2) Either cylinder can be put into connection with the waste pipe, and the cylinder lying opposite to this, or both together or separately, in connection with the pressure service pipes.

(3) The service pipes can be put into connection with a hand

pressure pump.

This apparatus is supplied by water under pressure, but owing to the peculiar system of balancing, the hydraulic power is not needed when the loading is normal and is only employed under exceptional circumstances. The descending auxiliary cages are always heavier, owing to the number of tubs on them than the ascending ones, and this provides the motive power.

The controlling apparatus is operated by one man, and consists of a set of valves worked by two levers, A and B. When the levers are in mid position the cages are locked. When lever A is moved forward, the right-hand hoists, front and back, rise, and the others fall. The reverse movement takes place when the lever, A, is pushed backward. When the loading of the hoists is not normal, both levers,

A and B, are moved forward or backward, as the case may be, and water admitted to the cylinders from the hydraulic pressure main to operate the lifts. There is a hand pressure pump connected with the controlling apparatus which can be used whenever the chief supply fails.

The rails on the main and subsidiary cages are inclined at such a gradient that the tubs run on and off without being pushed. The tubs are retained on the cages and hoists by suitable stops, which are all operated by the movement of one lever immediately the windingcage arrives at the banking level. Consequently all the decks are changed at once.

This apparatus effects a considerable saving of water, as the motive power is really obtained from the winding engines owing to the fact that the main cages travel a greater distance than the mean depth of the pit, the actual caging taking place above the banking level at the surface, and below the inset level at the bottom of the pit. The changing is not quite so rapid as when rams are used to push off the tubs, because these have to start from a state of rest under the influence of gravity, and a badly greased tub may delay operations. Neither is the action quite so certain. A ram overcomes any slight obstruction which may prevent the tubs starting on a small gradient.

The more perfect arrangement for very rapid changing appears to be a combination of the Tomson hoists with the Chambers pushing off rams.

Steam Hoists

empties

to

Supply bottom

empties

full tabs

deck

Harris Navigation Colliery.-At the downcast pit, two decks are changed at once. The full tubs run off the top deck, in the opposite direction to those going off the bottom deck, and proceed round a circular platform, having a gradient of about in 40, to the other side of the pit, where they join the loaded tubs from the bottom deck, the whole lot then going to the screens. The empty tubs to change both decks are raised by a steam hoist to a platform about 6 feet 6 inches high; part of them run straight to the shaft (to change the top deck), while the other part run round a second circular platform with a descending gradient, and reach the opposite side of the shaft, where they are placed on the lower deck of the cage (Fig 443).

full

tubs

from

top

Fig. 443.

deck

The steam hoist discharges its tubs automatically, as a stop is placed in the guides which tilts up the bottom. The cages are also provided with a loose bottom, pivoted about a pin. By an arrangement of projecting pieces and tub stops, similar to those in use at Clifton, tubs automatically discharge themselves as soon as the cage is lowered on to the keps.

Bell End Colliery.-At Bell End Pit, where the shaft only contains one cage, the author is employing a combination of several arrangements. The cage is double-decked, and each is changed independently. The rails are set at a permanent inclination, and the tubs are kept on by a hinged arm, but at the landing-place are released by an automatic arrangement described a little later on. At the bottom, the lower deck is received on a set of Stauss props, the tub is released and gravitates away to a platform. The cage is then lowered without reversing the engine, and the top deck tub released, which then runs to the same platform. The full tubs are now on the cage, which starts away to bank.

The platform referred to is attached to a hydraulic ram and pivoted about a point slightly away from its centre (Fig. 444). When the tubs are on, it therefore

takes a certain inclination limited by a stop. The curved guard, b, prevents the tubs running through, and the inclined surface will not allow them to pass out during the lift. The hanger-on pulls the lever, a, the platform and its contents rise a distance of about 6 feet. On arriving at the top the platform automatically stops through catching the lever, d, and cutting off the pressure, and is tilted in the opposite direction, when the tubs run away on the top landing, c, and gravitate to the point where they are attached to the haulage ropes; the platform then descends, ready to receive another consignment of empty

tubs.

The releasing gear employed is that designed by Mr. W. R. Wills. The inclination of the rails on the cage is such that the

a

Fig. 444.

tubs will only run forwards, and these are held on and released from the cage by the mechanism shown in Figs. 445, 446, and 447. The Larms, a a, revolve in suitable bearings, fixed to the side of the cage, and the angle pieces rest against the front end of the tub, but are prevented from rising too high by a stop (not shown in illustrations), while they are kept in their proper place by a spiral spring, b, attached to levers, c c, projecting outwards. On the cage being drawn out of the shaft these levers strike against and lift two catches, d, which fall back into place again, and on the return of the cage push the levers, c, into the position shown by the dotted line on the lefthand side of Fig. 446, and release the tub. By the time, however, that the cage rests on the legs the levers, c, have completely passed the catches, d, and the arms, a, would be closed by the springs, b, but. *So. Staff. Inst., iv., 31.

by such time as the tub is on an incline it has moved forward a short distance and the L parts of the arms are locked beneath the bottom of the tub to remain there until it has passed out, when they immediately close and prevent the further passage of the second tub.

At the surface, the cage is lifted until its bottom deck rests on the Stauss props, and the motion afterwards is always a lowering one. The tubs are automatically released by a similar apparatus to the one at the bottom.

Bascoup Colliery.-At No. 5 pit the changing operations are performed with extreme rapidity; at the bottom with the aid of a balance platform, and at the top with Stauss keps; and, by the peculiar arrangement existing there, both are carried on independently of each other.

The

When the cage reaches the bottom it is received upon a platform (p, Fig. 448), counterbalanced with a weight, w, equal to that of the empty tubs and the cage. The two empty tubs on the bottom deck are then replaced by full ones, and the extra weight of the load they contain causes the cage to descend with the platform, until the second deck is level with the inset. The tubs on this deck are then changed, and the platform and cage descend again, until the top deck is level with the inset, when the empty tubs are replaced by full ones. descent of the platform is governed by a brake, a, regulated by a handwheel, b. A catch, c, is also provided, which locks the platform at This catch can be the proper levels, by engaging with the stops, e. lifted off by an arm, d. It will allow the platform to ascend, but not to descend until released. Immediately the cage containing the full tubs is lifted by the winding engine, the counterbalance brings back the platform to the level of the inset, ready to receive the other cage.

At

The changing at the surface is carried out as follows. The bridlechains are made very long, and before the top cage comes to bank, the bottom cage reaches the balance platform just described. this point the engine is steadied, and the top cage is lifted until its lower deck rests on the Stauss props. An amount of slack rope is, therefore, payed out on the cage at the bottom by such operation, but through the bridle-chains being long the rope itself is kept straight, and does not "kink"; indeed, not so much is let out as would be expected, for before the top cage is actually raised to bank, the empty tubs on the bottom deck of the

cage below ground will be replaced by full ones, and the platform lowered, thus taking up a length equal to the height of one deck. At the surface the bottom deck is also changed first, the cage lowered by moving the Stauss props, the full tubs on the second deck replaced by empty ones, the cage again lowered and the top deck changed. The engineman has only to attend to the operations at the surface, the tubs at the bottom being changed with the balance platform, and by the time the top deck is changed at the surface, all the slack chain and rope has been taken up, and the engine starts away upon receiving the signal from the bottom.

At Anzin Colliery a balance platform is also employed, but to remove any chance of the rope kinking when the slack rope is payed on to the cage, a short length of aloe rope is in

Fig. 448.

serted between the bridle-chains and the capping of the steel rope. As this is quite soft and flexible, no harm can result.

Fencing the Pit Top.-To allow the empty tubs to run on, and the full ones off, the cage, a movable fencing has to be employed at the pit top. This usually consists of sliding gates opposite the ends of the cage, a permanent fence being erected on the other two sides. Projecting pieces on the cage top catch these gates and lift them upwards when the cage arrives at bank, but as soon as the descent commences the gates fall to the ground and secure the top of the shaft. As the cage travels at considerable speed when it strikes the fence, it is advisable that the latter should be made as light as possible. The preferable plan appears to be to employ three strips of iron or wood, a, b, and c (Fig. 449), resting on two props, d, cut to the shape illustrated. The top strip is longer than the second, the second than the third, and all are guided in a vertical plane by the ropes, e e. On the arrival of the cage at bank, the bottom bar is first lifted, then the