US3058547A - Braking system for hoists and the like - Google Patents

Description

Oct. 16, 1962 L. TlLEY ETAL 3,058,547

BRAKING SYSTEM FOR HOISTS AND THE LIKE Filed March 3, 1959 7 Sheets-Sheet 1 ATTORNES Oct- 16, 1962 e. L. TlLEY ETAL 3,058,547

BRAKING SYSTEM FOR HOISTS AND THE LIKE '7 Sheets-Sheet 2 Filed March 3, 1959 Oct. 16, 1962 G. TlLEY ETAL BRAKING SYSTEM FOR I-IOISTS AND THE LIKE '7 Sheets-Sheet 3 Filed March 5, 1959 W0 0 OJ I Oct. 16, 1962 G. L. TlLEY ETAL 3,058,547

BRAKING SYSTEM FOR HOISTS AND THE LIKE Filed March 3, 1959 7 Sheets-Sheet 4 INVENTORS GERALD L. TILEY ERIC OLDFIELD GERALD W. WYKES 1962 G. L. TILEY ETAL 3,058,547

BRAKING SYSTEM FOR HOISTS AND THE LIKE Filed March :5, 1959 7 Sheets-Sheet 5 INVENTORS GERALD L.TILEY ERIC OLDFIELD B GERALD W.WYK E$ auw nmnuns Oct. 16, 1962 G. TlLEY ETAL 3,058,547

BRAKING SYSTEM FOR HOISTS AND THE LIKE Filed March 3, 1959 7 Sheets-Sheet 6 1'. iii Fig 6 5% N F13 F! EFW 472" Im" L MAN! 52B INVENTORS GERALD L.T|LEY ERIC OLDFIELD GERALD W. WYKES Oct. 16, 1962 G. L. TlLEY ETAL 3,058,547

BRAKING SYSTEM FOR HOISTS AND THE LIKE Filed March 3, 1959 7 Sheets-Sheet 7 y s II W'll I INVENTORS GERALD L.T|LEY ERIC OLDFI ELD GERALD\W. WYKES M? WATTORNEYS ite tare BRAKING SYSTEM FOR HGISTS AND THE LIKE Gerald L. Tiley, near Hamilton, ()ntario, and Eric Oldfield and Gerald W. Wykes, Burlington, Ontario,

Canada, assignors to Canadian Westinghouse Company Limited, Hamiiton, Qntario, Canada, a Canadian company Filed Mar. 3, 1959, Ser. No. 796,906 Claims priority, application Canada Mar. 4, 1958 Claims. (Ci. 188-106) The present invention is concerned with improvements in or relating to brakes, and especially but not exclusively to brakes such as are used for mine hoists.

The movements of the skip or cage of a hoist are usually controlled by means of a drum of relatively large diameter, which may be a winding drum on which the hoist rope is wound, or a driving drum over the periphery of which the hoist rope passes to be driven by friction. To obtain eflicient operation of the hoist it must be possible to accelerate it rapidly to its maximum speed and then decelerate it rapidly to rest. Owing to the large forces involved it is usual practice to employ the motor as a brake, but brakes must also be provided for stopping the hoist accurately at a level, for holding the hoist stationary while the motor is not operative, and also as an emergency safety device in case of failure of the motor to act as a brake.

It is an object of the present invention to provide a new brake construction.

It is a further object of the present invention to provide an improved actuating system for a brake.

According to the present invention there is provided a brake comprising a pair of brake arms mounted for pivoted movement, a pair of brake shoes each mounted by a respective brake arm and .engageable with a member disposed between the brake shoes on opposite sides thereof to apply braking pressure thereto, first means for moving the brake arms to move the shoes into engagement with the said member, and a gravity-actuated weight constituting second means for so moving the brake arms and a pneumatic control system.

A specific embodiment of the invention will now be described, by way of example, with reference to the ac companying diagrammatic drawings wherein:

FIGURE 1 is a view in side elevation of part of the Koepe wheel of a mine hoist and two of the four brakes associated with the wheel,

FIGURE 2 is a View of the apparatus of FIGURE 1, taken in the direction of the arrow 2 in FIGURE 1,

FIG. 2a is a view in section taken along the line 22 of FIG. 2,

FIGURE 3 is a plan view from above of one of the brakes, drawn to a larger scale than FIGURES 1 and 2,

FIGURE 4 is a schematic diagram of the pneumatic equipment of one brake control system,

FIGURE 5 is a schematic diagram of the pneumatic equipment of another brake control system, and

FIGURE 6 is a schematic diagram of the electrical equipment of the two brake control systems.

FIGURE 6A is a diagrammatic representation of the electromagnetic actuators and their associated contacts and fluid relays.

Referring now to FIGURES 1 to 3 of the drawings, a Koepe drum consists of a central rope receiving part 10 and two radially extending rims 11, and is provided with four disc brakes, each generally indicated by 12, each rim serving as the disc for two of the brakes. The drum is mounted by means of a shaft 13 between bearings 14 and is rotated as required by a hoist motor (not shown) connected to the shaft 13 through a suitable coupling (also not shown). The bearings 14 are in turn mounted on the hoist framework 16 which is fastened securely to the floor 3,58,547 Patented Oct. 16, 1962 of the chamber in which the hoist drum, its brakes and motor are located.

The two brakes associated with each disc are disposed diametrically oppositely to one another, each brake comprising a frame, generally indicated by 17, which is rigidly secured to the hoist framework 16. Two levers 18 are mounted for movement in a horizontal plane by respective vertically-disposed pivots 19, which are mounted in a cross member 20 of the frame 17. The ends of the levers 18 nearer to the disc 11 are provided with brake shoes 21, which are pivotally connected to the levers to accommodate small angular changes as the levers move about their pivots, so that the braking surfaces of the shoes can always remain parallel to the associated braking surfaces of the disc. Each shoe is provided with a brake lining 22 of a suitable composite friction material.

The brakes are applied by supplying fluid under pressure, compressed air in this embodiment, to the interior of a respective cylinder 23 which is supported in the frame 17 by cross-members 24. The fluid under pressure enters the cylinder between two oppositely-disposed pistons 25 and forces them apart, so that the immediately adjacent lever ends are forced apart, the pistons engaging their respective arms by means of contact members 26 that are axially adjustable to take up wear in the brake shoes. In other embodiments flexible diaphragms may be employed in place of the pistons 25, since the distances through which they must move to apply the brakes fully is com paratively small. When the pistons move apart the brake shoes 21 move together, with a mechanical advantage due to the greater distance of the pistons from the pivots 19.

The braking effort that is applied by each brake to the drum can be controlled accurately by controlling the pressure of the fluid within the cylinder 23. Upon release of the pressure in the cylinder, e.g. by connecting the cylinder interior to atmosphere, the brake is positively dis engaged by a tension spring 27 connected between the arms on the same side of the pivots 19 as the cylinder 23'.

A safety device whose operation will be described in detail below is constituted by a weight 28, having a Wedgeshaped part 29 which extends between the arms 18 and is engaged at its narrowest width by two rollers 30' mounted respectively in the arms 18 by axles 31. The weight is connected by a rod 32 to a piston in a cylinder 33, and during normal operation of the brake the weight is held up against gravity by the action of compressed air supplied to the interior of the cylinder 33. If the air pressure within the cylinder is insuflicient the weight will descend, the wedge-shaped part forcing apart the rollers 30 so that the arms 18 are forced apart and the brakes are applied.

In most, if not all, of the applications of such a brake it is important that its speed of application is controlled by the inherent design of the brake and/ or by its control mechanism. This is especially important in the case of a safety device. For example, in a Koepe wheel hoist if the wheel is braked too violently the hoist rope may slip, and since the sliding friction between the wheel and rope is smaller than the stationary friction, there is a danger that control of the hoist will be lost completely.

In a brake in accordance with the invention the speed of brake application by the safety device can be predetermined accurately by choice of the design for the wedge-shaped part 29, for example by choice of the con tour of the sloping surfaces engaging the rollers 30. To permit the correct engagement of the sloping surfaces with the rollers, in some embodiments (as illustrated herein), the wedge-shaped part may be separate from the main weight 28 and connected thereto by rollers 29A working loosely in slots in the weight and/or the part, so that the wedge-shaped part can settle itself correctly between the rollers as it descends, despite some misalignment of the main weight 28. In other embodiments the rollers may be replaced by other guiding and engaging means, such as sliding shoes, which may be pivoted to the arms 18. p p v Each weight 28 is guided in its descent by a pair of guide rods 28A, the major lengths of which are a very loose fit in corresponding guide passageways 283 in the weight. The uppermost part 280 of each rod is enlarged to be a snug fit in the passageway 28B. Thus, when the weight is in its fully raised position the enlarged parts 28C hold the weight against tilting, which might cause rubbing of the corresponding brake shoe against the disc, but after the weight has descended a smalldistance it has cleared the enlarged parts and the danger of excessive friction between the weight and rods is reduced, besides permitting a little tilting of the weight which may be desirable, for example, when the weight and the part 29 are rigid with one another.

FIGS. 4 and 5 illustrate the pneumatic equipment and the functional relations thereof in two diiferent embodiments of the invention. Similarly, FIG. 6 illustrates the electrical equipment which serves to actuate or control the pneumatic equipment shown in FIGS. 4 and 5. FIG. 6A is a convenient schematic guide by which one may identify a particular pneumatic component in either FIG. 4 or FIG. 5 and then quickly identify the electrical control component in FIG. 6 which actuates that pneumatic component. For example, in making a correlation between pneumatic components in FIG. 4 and electrical components in FIG. 6, it is only necessary to align FIGS.

4, 6 and 6A side by side horizontally. Assuming then that one wishes to find the electrical component in FIG. 6 which actuates a particular pneumtaic component in FIG. 4, say valve 44, it is only necessary to look at the vertical line numbered 44 in FIG. 6A. One will note that the valve symbol on this line is at the same level as the valve 44 in FIG. 4. Tracing further down this vertical line to the electrical symbol on it, it is only necessary to look horizontally from this latter symbol to find on FIG. 6 the corresponding electrical component 44. Of course, FIG. 6A can also be used to proceed from a known electrical component in FIG. 6 to the correspondng pneumatic component in FIG. 4. The same procedure enables one to correlate FIGS. 5 and 6.

' Referring now to FIGURES 4 and 6 and 6A, the brake control system illustrated therein employs both pneumtaic elements (circuit of FIGURE 4) and electrical elements (circuit of FIGURE 6). The elements in FIGURE 4 within the broken line are supplied for each brake,'wl1ile those outside the line are common to all four brakes. The circuit of FIGURE 6 is for all four brakes. The compressed air for operating the system is supplied by a compressor (not shown) at about 80-100 pounds per square inch (p.s.i.)' and is fed through a filter 34' and a lubricator 35 to pipe 36. It will be understood that other main supply pressures can be employed, but this valueis found to be convenient for this particular embodiment. Moreover fluids other than air can be em ployed, for example, a liquid. Four valves 37 to 40 receive air from the pipe 36, the first three being regulating valves which supply air at a preset outlet pressure;

in FIGURE 4 this outlet pressure is indicated by the figure in the centre of the respective valve. The output pressure of the fourth valve 40 can be varied from the maximum available to zero by movement of an oper ators handle 41, an outlet 42 of the valve leading to atmosphere. The output pressure of the valve 40 is shown to the operator by a gauge 43.

Air from the valve 40 can be fed via valves 44, 45 and 46 connected in series to a relay'valve 48, the last mentioned valve controlling the supply of air from the pipe 36 to the brake cylinder 23. Thus, air from the pipe 36 is supplied to the inlet F of the valve 48 and is delivered from its outlet G (thence to the cylinder 23) at the pressure of the air supplied to its inlet E. The function of the valve 48 is to supply to the cylinder 23 as quickly as possible the relatively large volume of air required for application of the brake, while permitting the use of much smaller volumes in the remainder of the circuit, so that speedy operation is obtainable. An outlet H is connected to atmosphere. Each of the valves 44 to 46, as well as another valve 47, is of a pressure/ solenoid type which is 7 only actuated when the solenoid thereof is energized and a preset actuating pressure is applied to the inlet port D; when the valve is actuated the ports C and A are con-. nected together and when it is released the ports B and A are connected together. A valve 49 operates when actuated and released in the same way as the valves 44 to 47, but for actuation requires only the application of air to inlet D at a preset pressure suflicient to cause full application of the brakes. The function of the other elements of the circuit will be described as necessary.

' In describing the operation of the system it will be assumed at the start that the hoist is shut down and there is no air supply, the brakes being applied by their weights 28. It is also assumed that the hoist was left in condition for automaitc operation, so that the contacts MAN. 1-3 are all open. It is a characteristic of this brake operating system that once the brakes have been applied by the weights they can only be released by the intervention of the operator.

' The application of electrical power to the system between terminals L and N has no effect, since the supply of power to the valves etc. is blocked by open contacts 50A of main relay 50; the operating winding 50 cannot be energized until the contacts of a timmgrrelay T and various safety devices have been closed or short-circuited. Some of these safety devices, for example, are weight limit switches 51 having contacts 51A that are only closed when the associated weights have been raised fully. Operating winding 52 cannot be energized owing to the open contacts 53A that are closed only when full braking air pressure is applied to a pressure-operated switch 53. At this time the valve 44 is released and the switch 53 is connected to atmosphere via port 44B.

' If the compressor is now started air at supply pressure is supplied to the valve 37 to 40, to the ports 44D and 47D and to the relay 48. The air supplied from valves 37, 39 and 40 is blocked by the unactuated valves 49, 46 and 44 respectively, while that supplied from valve 38 to ports 45D and 46D is ineffective, since the solenoids of the valves 45 and 46 are not energized. No air is supplied-by relay 48 to cylinders 23, since the inlet E of the relay is connected to atmosphere via valve port 49C. Thus, although both air and electric power are supplied to the system the brakes will remain applied by the weights 28. I

To regain control of the brakes the operator moves the manual/ automatic selector switch to the manual position, closing the contacts MAN. 13; moves the control valve handle 41 to the FULL-ON position; and then presses a push-button 54 (FIGURE 6). Provided that the contacts associated with various safety devices not immediately concerned with the brakes are closed (indicated herein by the broken line connection in series with the pushbutton contacts 54A) the pressing of the pushbutton shortcircuits (among other safety device contacts) the weight limit switch contacts 51A and timing relay contacts TA, so that main relay winding 50 is energized and contacts 50A close. Valve solenoids 44 and 45 are now energized via closed contacts MAN. 3 and MAN. 2 respectively and consequently valves 44 and 45 are actuated. The actuation of valve 44 applies the FULL-ON air pressure to the switch 53 and contacts 53A close to energize winding 52, causing contacts 52B to close and enabling winding 55 to be energized via contacts 52B and MAN. 1. Contacts 55A are closed when winding 55 is energized and.

47 and valves 47 remain released. The energization of winding 55 closed contact 55C sealing-in the relay 55 so that it is new independent of the operation of relay 52 and switch 53. Contacts 55B are closed, and contacts 47E also, the latter remaining closed as long as the valves 47 are released, so that Winding T is energized and contacts 51A can now be closed by the weights lifting (as suming the other safety devices are not operated) when the pushbutton can be released.

The actuation of the valves 44 to 46 causes the FULL- ON air pressure to be applied to each valve 48, so that air at full pressure is fed to the respective cylinders 23 and also to the valve ports 49D via the unactuated valves 47. After a delay while volumes 56 and the brake cylinders are filled the valves 49 are actuated and air from valve 37 is fed to the cylinders 33 and the weights begin to lift. The pressure of the air from valve 37 is indicated by a gauge 57. Volumes 58 are filled at this time. When all the weights are fully raised all the contacts 51a are closed. If the pushbutton 54 is released before contacts 51A close the main relay winding 55 is deenergized, opening the contacts 519A, and the system returns to its original condition.

The weights are now held raised by the air from valve 37 and the rakes are applied under control of the valve 49. If the pressure of the air supplied to the brake cylinder is too low for full application of the brakes (in this embodiment below about 60 p.s.i.), then it will be too low for actuation of the valves 49 and the Weights cannot be raised. If the pressure of the air from the valve 46 is now reduced by moving the handle 41 the contacts 53A open and relay winding 52 is de-energized, opening contacts 52B and closing contacts 52A so that the valve solenoids 47 are now energized. Each valve 47 is now actuated and supplies air from outlet A of valve 49 to the inlet D of that valve, so that the valve 49 is locked-up in the actuated condition, under the control of the air pressure in the weight cylinders 33 and not that in the brake cylinders 23. Contacts 47E are now open, but contacts 55B maintain the winding T energized, the winding 55 being maintained energized by closed contacts MAN. 1 and 550. It will be apparent that the operation of the switch 53 prevents the raising of the weight unless the manual control is placed FULL-ON.

The operator now has full manual control of the brakes by means of the valve 49, the brakes being fully released by the springs 27 when the air pressure is zero.

If at any time the operator moves the handle 41 to give full application of the brakes the switch 53 closes contacts 53A and winding 52 is energized, opening contacts 52A and releasing valves 47, so that the inlets D of valves 49 are connected to the respective cylinders 23. If full braking pressure is not applied to each cylinder 23 air will escape from the reservoir 56 through a leak 59 associated with a oneway valve 60, until the pressure at inlet 49D is insuflicient and the valve 49 releases, connecting the cylinder 33- to atmosphere through valve outlet port 49C. As soon as the pressure in cylinder 33 falls a small predetermined amount below the required value a quick-acting valve 6-1 operates to connect the interior of cylinder 33 more directly to atmosphere and the respective weight descends and applies the brake. As the weight begins to descend its respective contacts 51A open, de-energizing winding 50 and opening contacts 50A so that all the valves 44 to 46 are released. The release of the valve 46- associated with the faulty brake connects volume 58 to inlet E of relay valve 48 and, provided the loss in braking pressure is not due to a fault between valve 46 and the cylinder 23, this reservoir pressure causes the relay valve 48 to supply air at an operative pressure to the cylinder 23, so that emergency braking is commenced immediately. Air will escape from the reservoir to atmosphere through a leak 62 associated with a oneway valve 63 and the braking pressure applied to 23 is progressively reduced. Each brake is so arranged that its weight will begin to apply an elfective braking etfort when the air pressure efiort is about half normal, so that an overlap of braking is obtained, but full air pressure and full weight effort are not applied simultaneously. The control of the braking characteristic on such a fault is determined by, for example, selection of the reservoir 58, the leak 62, and the valve 61 and by the structure of the weight, as described above. In some embodiments a choke 67 may be included between one or more of the cylinders 33 and their valves 61 to give further control by choice of the choke.

In the case of the brake or each of the brakes that is not faulty the valves 44 to 57 are released, but the full braking air pressure will be applied by valve 4-7 to valve 4 and that valve will remain actuate-d, applying the air at full pressure from 37 to both the relay valve 48 and the weight cylinder 3-3. Indicating apparatus (not shown) of conventional form will be provided to show the operator which of the brakes has reverted to weight operation.

The operation at any time of any of the safety devices connected in circuit with the winding Stl will also cause the release of the valves 44 to 47 and the consequent full air operation of the brakes by the air supplied from the valve 37. If on the supply of this air there is not a fast enough build-up of air pressure in the cylinder 23, the valve 49 will be released and will connect the cylinder 33 to exhaust, causing the weights to descend, and resulting in an emergency stop.

The hoist may be changed from manual to automatic operation only while the cage or skip is at a level and an interlock (not illustrated) is provided on the manual/ automatic switch for this purpose. With the cage or skip at a level the contacts MSX will be open, and since it will be within the creep speed zone the contacts CSR will also be open.

The system is brought into automatic operation by opening the contacts MAN. 1-3, which de-energizes the valve solenoids 44 and 45 and the winding 55, whereupon contacts SSA open and de-energize valve solenoids 46 and 47. As described above such release of all four valves 44 to 47 causes application of the brakes by air pressure, and failing that by the weights.

If the valve 47 associated with any brake fails to release properly it will not be able to test the pressure in cylinder 23 (i.e. by connecting the cylinder 23 and inlet 49D) and may give a false indication; in such a case the associated contacts 47E will not close and, since contacts 55B are now open, the relay T will release opening contacts TA and thereby causing all the brakes to be applied. The relay T is of the type having a delayed release after de-energization so that the contacts 47E will have adequate time to close and the brakes will not be applied prematurely.

It will be understood that the complete hoist will include a considerable amount of ancillary apparatus, for example, apparatus for the hoist motor, apparatus to permit the selection at any level of the level to which the skip or cage is to travel, and a programme control with associated weighing devices for determining the most efficient acceleration and deceleration of the skip or cage. Such ancillary apparatus is not illustrated and it will be appreciated therefore that the representation herein of the automatic brake control apparatus by the contacts MSX and CSR only is a considerable simplification, which is adopted only for ease of description of the present invention.

A signal from the ancillary apparatus to start the hoist results in the closing of contacts MSX, whereupon winding 55 is energized and contacts 55A close to energize valve solenoids 46. The pressure relay 53 is already released so that contacts 52A are closed and valve solenoids 47 are also energized. Valve 46 is actuated and air at 5 p.s.i. is fed from valve 39 to the relay valve,

which repeats this pressure in the cylinder 23 and primes the brake ready for immediate application by a higher pressure. The actuation of valve 47 applies the pressure in cylinder 33- to port 49D and seals-in the valve 49. As the cage or skip leaves the creep speed zone the relay CSR is energized and contacts CSR close, energizing valve solenoids 45 and actuating valves 45, so that the relay valve 48 is connected to atmosphere at port 44C and the brakes are completely released by the springs 27.

Limit switches such as 64 are provided for each brake and form part of a safety circuit that will stop the hoist motor if the brakes are not fully removed within a predetermined period (about 15 seconds with this embodiment) after power has been applied to the motor. During travel of the skip or cage between levels its speed will be determined by the ancillary apparatus referred to above.-

As the skip or hoist enters the creep speed zone at the new level the contracts CSR open again, releasing valves 45 and applying the priming pressure to the brake cylinders 23. When the new level is reached the contacts MSX open and winding 55 is de-energized, causing release of relays 46 and 47 and application of full braking pressure from valve 37 to relay valve 48 and thence to cylinders 23. The valves 47 operate as described above to check that this pressure has been applied to the brake cylinders and the contacts 47E operate, also as described, to check that the valves 47 have operated correctly.

If supply pressure is lost while the hoist is in motion (eg due to compressor failure or a burst pipe) the valve 47 is released, since its actuating air pressure is taken directly from the pipe 36. Since there will be little or no air pressure in the cylinders 23, the valve 49 will also release and the weights will descend to apply the brakes. The relay 50 has contacts (not shown) included in the hoist motor circuit that will cause the motor to be stopped upon the opening of any pair of the contacts 51A, or of any of the other contacts in series With the relay winding 50. 'It supply pressure is lost while the hoist is at rest with the brakes on, the valves 47, 49 and 37 will tend to maintain the air pressure at its operative Value; leakage from the system will reduce the pressure applied to 491) until the valve releases and the Weights descend. 7

Another set of limit switches 65 are provided for the brakes to detect wear in the brake shoes, these switches having contacts (not shown) in the hoist motor circuit that stop the motor if the wear is excessive.

The ancillary apparatus is so arranged that on automatic operation, when the skip or cage is to be jogged accurately into position at the level, the brake cylinders are kept primed to allow quick and quiet application of the brakes. The limit switches 64 are unable to distinguish between full and primed brake application and if the hoist is operating with the brakes primed for more than about 15 seconds, the timing device described above will operate and stop the hoist. This is prevented by providing a pressure switch 66 that detects the relatively low priming pressure and prevents operation of the tim ing device during the jogging operation.

Referring now to FIGURES and 6 and 6A, components common to the circuits of FIGURES 4 and 5 are given the same reference and, to avoid repetition, the differences between the two circuits will 'be described, since the circuits otherwise function in the same manner.

In the circuit of FIGURE 5 the control valve 40 is provided with an electric interlock switch in the line between contacts operated by a cam on the shaft that carries the control handle 41. This switch is in series with the contacts 52A and is normally closed unless the handle 41 is put into the full brake application position. The interlockswitch therefore performs the same function as the pressure switch 53 in de-energizing the valves 47 (directly 52A and the switch 55A and which is.

instead of through relay 52) when full brake application is indicated, so that they can test if the corresponding pressures are obtained in the brake cylinders. The interlock switch guards against the possibility that the switch 53 is not operated by the pressure applied to it, e.g. because the pressure has been reduced by leakage, and the valve 47 therefore cannot be taken out of its locked up condition for testing purposes.

Another difference is that an indicator is included to show that the pistons or diaphragms 25 of the brake cylinder 23 have travelled more than a predetermined amount, indicating for example that the brake shoes have become overworn and readjustment is necessary. For this purpose the cylinder 23 is provided with ports, indicated by 69, that are uncovered when the pistons or diaphragms have moved the said predetermined amount, whereupon the air under pressure in the cylinder 23 is fed to a switch 70 that operates a suitable warning device.

In the circuit of FIGURE 5 the valve outlets 490 no longer lead to atmosphere, but instead are connected to discharge into their respective brake cylinders 23, while the valve inlets 470 are now connected directly to the pipe 36 instead of to the pipe connecting the respective cylinder 33 and the valve 46. The full-on air pressure again is fed to 49C and causes the valves 49 to be actuated, but the valves are now locked-up under the pressure from the pipe 36, such locking-up being essentially to prevent re-application of the weights as soon as the brake pressure from 40 is reduced below the fullon value. The valves 49 are now responsive to loss of pressure in the pipe 36 to unlock themselves and thereafter to apply the weights as soon as they detect after such interlocking a low enough pressure in the cylinders 23. If the valves 49 release the respective cylinders 33 and 23 are connected together and they may be so constructed that a braking characteristic within the permissible limits is obtained. Thus as the weights descend they will drive air into the brake cylinders 23 and tend to maintain the braking by the cylinders. This effect will continue until the weight wedge engages the rollers 30 and begins to apply a braking effort of its own, this braking effort being less than the maximum because of the upward thrust of the air remaining in the cylinders. As the air exhausts further the braking efiort from the air pressure decreases progressively, while that from the weights increases progressively, the design of the brakes being such that the maximum permissible braking is not exceeded.

A further additional feature of the circuit of FIGURE 5 is that additional braking is available, for example as an emergency measure. This additional braking is provided by supplying the brake cylinder alternatively from the valve 37, or from a similar valve 71 set for an appreciably higher pressure, the pressure that is to be operative being selected by a valve 72 and indicated by the gauge '57. This necessitates additional circuitry in FIG. 6 which may comprise a circuit connected between the lines L and N in which an emergency push button and a hoist cage engaging limit switch are connected in shunt and this combination is connected in series with the solenoid of the valve 72 in FIG. 5. With the valve 72 released air is fed from the valve 37 (in this embodiment set at 60 p.s.i.) to the valves 49, while with the valve actuated, by manual operation of the emergency pushbutton, or by the hoist cage engaging the hoist cage limit switch, the air is fed instead from the valve 71 (in this embodiment set at p.s.i.).

It will be noted that in the circuit of FIGURE 5 the priming pressure set by the valve 39 is higher than that of FIGURE 4, the reason for this is that the spring 27 is stronger to give a faster release and a correspondingly higher pressure is required for adequate priming.

A brake in accordance with this invention is able to operate faster than the hoist brakes known hitherto owing 9 to, among other factors, the relatively low effective masses of the arms 18 and the brake shoes 21 and the small distances through which those masses must be moved between full application and full release of the brake.

Moreover, the use as a safety device of a weight acting directly on the brake arms (i.e. without any intervening linkage) ensures rapid emergency application of the brakes as required, the brake in accordance with this invention also having the advantage of flexible control of the braking characteristic provided by the safety device. The braking system in accordance with this invention is such as to permit rapid operation of the brake. Factors assisting in such rapid operation are the use of a relay valve to supply the operating fluid directly from the supply, the use of fluid at an initial priming pressure to set up the brake ready for full braking operation, and the use where possible of an actuating pressure for the valves (such as valves 45 and 46) lower than the supply pressure so that the time taken for such valves to release is reduced.

It will be understood that the invention has been disclosed with reference to a specific embodiment thereof, and accordingly various modifications and changes may be made to the apparatus described within the scope of the invention as set out in the appended claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A braking system for a hoist drum mounted for rotation about a horizontal axis, which system comprises an annular member fixed to and extending from said drum and presenting opposed brake contact surfaces, a pair of brake levers, each of said levers being mounted on an axis intermediate its end for pivotal motion in a plane parallel to the said horizontal axis and each of said levers having a brake shoe coupled thereto adjacent one end thereof, said levers being transversely spaced from each other and positioned relative to said annular member such that said shoes may be made to engage respectively the opposed contact surfaces of said annular member by pivotal motion of said levers about their respective axes, a source of fluid pressure, fluid pressure actuated means for pivoting said levers about their respective pivotal axes to bring said shoes into gripping engagement with said contact surfaces, valve means connected between said source and said pressure actuated means for controlling the application of pressure from said source to said fluid pressure actuated means, spring means acting on said levers for maintaining said shoes out of gripping engagement with said contact surfaces when fluid pressure below a first predetermined minimum is applied to said fluid pressure actuated means, a massive weight mounted for vertical motion on a fluid pressure actuated lift means connected to said source of fluid pressure, said weight having in fixed relation thereto surfaces inclined with respect to the horizontal but substantially perpendicular to a plane containing the axes of said levers, said surfaces extending above and below said levers and in proximity thereto, portions of said levers having means for hearing on said inclined surfaces, said lift means being adapted when actuated to support said weight at a predetermined height relative to said levers such that the distance between said inclined surfaces at the height of said bearing means is such that the inclined surfaces do not engage the bearing surfaces when said brake shoes are in gripping engagement with said annular member wherein upon the pressure applied to said lift means falling below a second predetermined minimum said weight falls under the influence of gravity and forces the ends of the levers bearing the brake shoes together to bring the brake shoes into gripping engagement with said annular member by means of the interaction between said inclined surface and said bearing means.

2. A braking system for a hoist drum mounted for rotation about a horizontal axis, which system comprises an annular member fixed to and extending from said drum and presenting opposed brake contact surfaces, a pair of brake levers, each of said levers being mounted on an axis intermediate its end for pivotal motion in a plane parallel to the said horizontal axis and each of said levers having a brake shoe coupled thereto adjacent one end thereof, said levers being transversely spaced from each other and positioned relative to said annular member such that said shoes may be made to engage respectively the opposed contact surfaces of said annular member by pivotal motion of said levers about their respective axes, a source of fluid pressure, fluid pressure actuated means for pivoting said levers about their respective pivotal axes to bring said shoes into gripping engagement with said contact surfaces, valve means connected between said source and said pressure actuated means for controlling the application of pressure from said source to said fluid pressure actuated means, spring means acting on said levers for maintaining said shoes out of gripping engagement with said contact surfaces when fluid pressure below a first predetermined minimum is applied to said fluid pressure actuated means, a massive weight mounted for vertical motion between the portions of said levers opposite the mounting axes from these ends of the levers having a brake shoe coupled thereto, said weight having, in fixed relation thereto, upwardly and outwardly inclined surfaces, said portions of said levers opposite the ends having brake shoe coupled thereto having means for bearing on said inclined surfaces, fluid pressure actuated lift means connected to said source of fluid pressure, said lift means being adapted to support said weight, upon actuation of said lift means, at a predetermined height relative to said levers such that the distance between said inclined surfaces at the height of said bearing means is less than the distance between said bearing means when said brake shoes are out of gripping engagement with said annular member, wherein upon pressure to said lift means falling below a second predetermined minimum said weight falls under the influence of gravity and forces the ends of said levers apart to bring the brake shoes into gripping engagement with said annular member by means of the interaction between said inclined surfaces and said bearing means.

3. A braking system for a hoist drum mounted for rotation about a horizontal axis, which system comprises an annular member fixed to and extending from said drum and presenting opposed brake contact surfaces, a pair of brake levers, each of said levers being mounted intermediate its ends for pivotal motion about a vertical axis, and each of said levers having a brake shoe coupled thereto adjacent one end thereof, said levers being transversely spaced from each other and positioned relative to said annular member such that said shoes may be made to engage respectively the opposed contact surfaces of said annular member by pivotal motion of said levers about their respective axes, a source of fluid pressure, fluid pressure actuated means for pivoting said levers about their respective pivotal axes to bring said shoes into gripping engagement with said contact surfaces, valve means connected between said source and said pressure actuated means for controlling the application of pressure from said source to said fluid pressure actuated means, spring means acting on said levers for maintaining said shoes out of gripping engagement with said contact surfaces when fluid pressure below a first predetermined minimum is applied to said fluid pressure actuated means, a massive weight mounted for vertical motion between the portions of said levers opposite the vertical mounting axes from those ends of the levers having a brake shoe coupled thereto, said weight having, in fixed relation thereto, upwardly and outwardly inclined surfaces, said portions of said levers opposite the ends having brake shoe coupled thereto having means for bearing on said inclined surfaces, fluid pressure actuated lift means connected to said source of fluid pressure, said lift means being adapted to support said weight, upon actuation of said lift means, at a predetermined height relative to said levers such that the distance between said inclined surfaces adjacent said bearing means is less than the distance between said bearing means when said brake shoes are out of gripping engagement with said annular member, wherein, upon the pressure to said lift means falling below a second predetermined minimum said weight falls under the influence of gravity and forces the ends of said levers apart to bring the brake shoes into gripping engagement with said annular member by means of the interaction between said inclined surfaces and said bearing means.

4. In a braking system for a hoist drum mounted for rotation about a horizontal axis and having mounted thereon an annular member extending from the drum and presenting opposed brake contact surfaces, said system including a pair of brake levers each of which levers is mounted intermediate its ends for pivotal motion about a vertical axis, each of said levers having a brake shoe coupled thereto adjacent one end thereof, said levers being transversely spaced from each other and positioned relative to said annular member so that said shoes may be made to engage respectively the opposed contact surfaces of said annular member upon pivotal motion of said levers about their mounting axes, said system also including a source of fluid pressure and fluid pressure actuated means connected to said source for actuating said levers in directions about their respective pivotal axes to bring said shoes into gripping engagement with said contact surfaces, valve means for controlling the application of pressure from said source to said fluid pressure actuated means, and spring means acting on said levers for maintaining said shoes out of gripping engagement with said contact surfaces when fluid pressure below a first predetermined minimum is applied through said valve means to said fluid pressure actuated means, the improvement which comprises a massive weight mounted for vertical motion between the portions of said levers opposite the vertical mounting axes from those ends of the levers having brake shoes coupled thereto, said weight having in fixed relation thereto a pair of opposed, upwardly and outwardly inclined surfaces, means on said portions of said levers for bearing on said inclined surfaces, fluid pressure actuated lift means connected to said source of fluid pressure, said lift means being adapted to support said weight, upon actuation of said liftmeans, at a predetermined height relative to said levers such that the distance between said inclined surfaces adjacent said bearing means is less than the distance between said bearing means when said brake shoes are out of gripping engagement with said annular member, wherein, upon the pressure to said lift means falling below a second predetermined minimum said weight falls under the influence of gravity to a height such that the distance between the inclined surfaces adjacent the bearing means is substantially equal to the distance between said bearing means when the brake shoes are in full gripping engagement with said annular member. 5. A combined pneumatic mechanical braking system for a hoist drum including a first pneumatic actuator to operate a mechanical brake on said hoist drum producing a first pressure on the brake surfaces in response to a first pneumatic pressure supplied to said first pneumatic actuator and a weight operated mechanical actuator to operate said brake producing a pressure equivalent to said first pressure on the brake surface in response to the downward force exerted by the weight, a second pneumatic actuator opposing the operation of said weight operated actuator, producing a force equal to said weight in response to a pneumatic pressure approximately equal to said first pneumatic pressure, supplied to said first pneumatic actuator, a source of compressed air, a first control valve movable from an off to a full on position to control the pressure of air in the supply line to said first pneumatic actuator from said source, a second control valve movable from a first position to second position in response to reduction of pressure of said source, said second control valve in its first position coupling said second actuator to said source and in its second position coupling said second actuator to said supply line.

References Cited in the file of this patent UNITED STATES PATENTS 437,834 Kaseberg Oct. 7, 1890 707,345 Neale Aug. 19, 1902 2,228,818 Eksergian Jan. 14, 1941 FOREIGN PATENTS 954,006 Germany Dec. 13, 1956 266 Great Britain Ian. 22, 1876 UNITED STATES PATENT OFFICE v CERTIFICATE OF CORRECTION Patent N01, '3,058 547 October l6, 1962 Gerald L, Tiley et alt,

It is hereby certified, that err ent requiring correction and that th or appears in the above numbered patcorrected below,

e said Letters Patent should read as Column 12 line 25,,

for "first" second 9 second occur-rence read Signed and sealed this 18th day of August 1964 (SEAL) Attest:

ERNEsT w. SWIDER' I EDWARD J. BRENNER Attesting Officer Commissioner of Patents

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