Title:
SAFETY BRAKE UNIT FOR A MINE CAGE
United States Patent 3695396


Abstract:
A safety brake unit for a mine cage or similar elevator car. A safety line suspended in the elevator shaft extends through the safety brake unit mounted in the mine cage and several such units may be mounted in a single cage. The safety brake unit includes a pair of brake drums about which the safety line is wrapped. The brake drums have circumferential grooves to hold the wraps of the line and one drum is offset or tilted with respect to the other to permit the line to extend continuously about both drums. The brake drums are electrically actuated and switches are provided in the electrical circuits to close whenever the mine cage is released from its hoist or commences to drop too fast. Whenever several safety brake units are mounted in a single cage, the electrical actuating means will permit all of them to operate in unison. A mechanical fail-safe brake setting mechanism may also be included to set the brakes if the electrical system fails.



Inventors:
JONES ROBERT LOUIS
Application Number:
05/085152
Publication Date:
10/03/1972
Filing Date:
10/29/1970
Assignee:
SAFETY LIFT CORP.
Primary Class:
Other Classes:
254/336
International Classes:
B66B5/04; (IPC1-7): B66B5/16
Field of Search:
187/89,29,39,38,73 254
View Patent Images:
US Patent References:
2969854Lifting, lowering and hauling1961-01-31Blair
1977452Safety apparatus for elevators1934-10-16Neuschotz
1934508Elevator safety1933-11-07McCormick
1072138N/A1913-09-02Matthews
0132113N/A1872-10-08



Foreign References:
DE1227219B1966-10-20
Primary Examiner:
Blunk, Evon C.
Assistant Examiner:
Maffei, Merle F.
Claims:
I claim

1. A safety system for an elevator cage or the like which is normally suspended in a shaft having no rigid guide rails, and by a hoist line mechanism to be moved upwardly and downwardly in the shaft, and including in combination therewith:

2. A safety system for an elevator cage or the like which is normally suspended in a shaft having no rigid guide rails, and by a hoist line mechanism to be moved upwardly and downwardly in the shaft, and including in combination therewith:

3. In the safety system defined in claim 1, wherein:

4. In the safety system defined in claim 1, wherein:

5. In the safety system defined in claim 1, wherein

6. In the safety system defined in claim 1, including:

7. In the safety system defined in claim 1, including:

8. In the safety system defined in claim 8, including:

9. In the safety system defined in claim 8, including:

Description:
The present invention relates to safety braking devices, and more particularly to safety brakes for elevator cars and mine cages which are raised and lowered by cable systems. The invention is now used in mine cages and is thus herein referred to as "a safety brake" or "a safety brake for a mine cage."

An object of the invention is to provide a novel and improved safety brake for a mine cage which engages a safety line suspended in the shaft which will stop the movement of the cage by gripping the line whenever the cage commences to move too fast, or whenever the pull of the hoist cable is suddenly released, and which will grip the safety line without causing it to slip or be damaged.

Another object of the invention is to provide a novel and improved safety brake for a mine cage which can also be operated manually to stop the downward movement of the cage at any time.

Another object of the invention is to provide a novel and improved safety brake for a mine cage, an elevator car or the like, which is a simple, compact unit of a standardized construction connecting with a suspended safety cable in the cage shaft.

Another object of the invention is to provide a novel and improved safety brake system for a mine cage which may use a plurality of improved, standardized safety brake units and which will operate such units in unison to hold the cage substantially level should an accident occur which would permit the cage to fall.

Another object of the invention is to provide a novel and improved braking system which is reliable and quick acting and which may be easily arranged to operate in a fail-safe manner.

Other objects of the invention are to provide a safety brake for a mine cage which is a simple, compact, low-cost, rugged and durable unit.

With the foregoing and other objects in view, my present invention comprises certain constructions, combinations and arrangements of parts and elements as hereinafter described, defined in the appended claims, and illustrated in preferred embodiment by the accompanying drawing in which:

FIG. 1 is a front elevational view of a mine cage supported by a hoist cable and having two improved safety brake units installed in the top of the cage with each unit being connected with a suspended safety cable extending from the top to the bottom of the shaft wherein the cage is located, the hoist cable and the safety cables being broken away in the view to conserve space.

FIG. 2 is a side elevation view of the upper portion of the cage shown at FIG. 1 with wall sections broken away to show components within the cage.

FIG. 3 is a sectional plan view of the cage as taken from the indicated line 3--3 at FIG. 1 to better show the arrangement of safety brake units.

FIG. 4 is a fragmentary plan view of a portion of the showing at FIG. 3, but on an enlarged scale and with the cover plate of a safety brake unit broken away and in section to show the cable wound about drums forming the safety brake unit.

FIG. 5 is an offset transverse sectional view, as taken from the indicated line 5--5 at FIG. 4, but on an enlarged scale.

FIG. 6 is a transverse sectional view as taken from the indicated line 6--6 at FIG. 4, but on an enlarged scale.

FIG. 7 is a longitudinal sectional view as taken from the indicated line 7--7 at FIG. 5 to show more specifically the internal structure of a braking drum.

FIG. 8 is a circuit diagram of the safety brake system illustrated at FIGS. 1-7, with broken lines illustrating additional circuit components which may be included in the system.

FIG. 9 is a front elevational view of a mine cage similar to the showing at FIG. 1, but on a reduced scale, and arranged to use only one safety brake unit and with a supplementary line-tensing mechanism being included with the unit.

FIG. 10 is a fragmentary sectional detail as taken from the indicated line 10--10 at FIG. 9, to show the structure of the line-tensing device.

FIG. 11 is a fragmentary plan view of a portion of the showing at FIG. 3, but on an enlarged scale, with cover plate portions broken away to show parts otherwise hidden from view, and with an auxiliary fail-safe apparatus being added to the organization.

FIG. 12 is a longitudinal offset sectional view as taken substantially from the indicated line 12--12 at FIG. 11, but on an enlarged scale.

The improved safety brake unit, the present invention, uses a safety line which is suspended alongside a mine cage or other type of elevator car. The safety line extends through the safety brake unit so that the brake unit may grip the line to retard and stop the downward movement of the cage. The safety line is held by the brake unit by winding the safety line about a pair of drum-type brakes within the safety brake unit. The safety brake unit itself is built in a compact manner with the pair of drum-type brakes being alongside each other as well be described.

One or more of such units may be mounted in a mine cage in any suitable arrangement with each unit connecting with a suspended safety line. However, if a plurality of units are used, they must operate in unison to balance the pull on the several safety lines and these lines are thus arranged in such a balanced manner as to keep the mine cage in an upright position insofar as is possible.

Referring more particularly to FIGS. 1-8 of the drawing, a typical mine cage C, as shown at FIGS. 1-3, is modified to include two safety brake units B and B' substantially identical in structure and arranged in symmetrical opposition with each other to connect with two safety lines L and L' respectively, with one line being at each side of the cage to thereby restrain the cage in a balanced manner. The cage C is constructed as an upright, box-like unit having opposing sidewalls 20 which extend upwardly from a floor section 21 to connect with a roof 22 and with the primary, structural members of the cage being in the sidewalls. The front and the rear of such a cage is ordinarily left open for access in either direction. However, closure gates 23 are provided at the front and rear of this cage to protect the occupants when the cage is being raised or lowered.

This cage is supported by a hoist cable 24 connected to a drawbar 25 upstanding from the top and center of the cage. A vertical guide slot is formed by angles 26 at the outer surface of each side of the cage and guide cables 27, or guide rails, extend from the top to the bottom of the shaft, in any manner not shown, to lie in the guide slots to hold the cage in position against rotating and weaving when it is being lowered and raised in a shaft. The hoist cable 24 is wound upon the reel of a hoist mechanism at the top of the shaft, not shown, and other features, also not shown, will include controls used to regulate the starting, stopping, raising and lowering of the cage by the hoist cable.

This cage C is modified to incorporate the pair of safety brakes B and B' by extending the normal height of the cage about 18 inches to place the brakes near the roof section of the cage and at the same time maintain sufficient head clearance for the passengers therebelow. A box-like support frame 30, formed by side channel members 31, secured between upper and lower channel members 32, extends transversely across the central portion of the cage, and is rigidly and securely affixed to each sidewall 20 of the cage. Each brake unit is mounted upon a backwall plate 33, at each side of the frame, and each backwall plate extends transversely across the cage. Thus, the two backwall plates are mounted vertically, and in spaced parallelism upon opposite sides of the support frame 30, as by welding or bolting the plates to the top and bottom channels 32 of the framework.

Since this support frame 30 carrying the brakes must be designed to withstand the entire weight of the cage, the hoist cable drawbar 25 conveniently connects with this frame. The drawbar 25, formed as two parallel flat bars spaced apart in a clevis-like arrangement, extends from the connection with the hoist line, downwardly and through an opening 30a at the center of the support frame 30 and this drawbar terminates as a hooked bottom 34 which engages the underside of the frame.

The safety lines L and L' extend downwardly from opposite sides of the elevator shaft and each turns about a sheave 35 and 35', respectively, which is mounted upon the respective sidewalls 20 of the cage. The lines L and L' turn about their respective sheaves and extend horizontally and transversely through the cage and through the respective brake units B and B' to wrap about the drum brakes therein and to project from opposite sides of the cage. There, the lines L and L' turn about sheaves 36 and 36' respectively, mounted upon the sidewalls of the cage and extend downwardly to the bottom of the shaft. Each safety line L and L' is secured to a suitable anchor 37 at the top of the shaft and each will include a line-tensing counterweight 38 at its bottom, at the base of the shaft, as in the manner illustrated at FIG. 1. If desired, an anchored holding socket 39 may be provided at the bottom of each line to prevent it from being pulled upwardly by the hoist cable 24 if the brakes are set.

Each safety brake unit B and B' includes two drum-type brakes 40 and 41 which are arranged side by side and are carried upon spindles 42 and 43, respectively. These spindles are affixed to the backwall plate 33 of the unit to cantilever therefrom. The spindle axis of the brake 42 is normal to the backwall plate 33 and the spindle axis of the brake 41 is tipped upwardly with respect to the normal of the backwall plate a few degrees to permit the safety line L, or L', to extend from the sheave 35, or 35', and to be wrapped about the brakes 40 and 41 without interference as will be hereinafter described. Accordingly, the brake 40 may be referred to as the "normal brake" and the brake 41 may be referred to as the "tipped brake." The connections of the spindles 42 and 43 to the backwall plate are reinforced by a channel 44 having the edges of its flanges welded to the backwall plate, as at 45, as illustrated at FIG. 5, so that the base of each spindle will extend through a socket 46 in the web of the channel and into a socket 46' in the backwall. When welded into these sockets 46 and 46', the spindles are securely held in position. The safety brake unit includes further, an oval housing 47 extending about and partially enclosing the drum brakes and this housing includes a flange 48 about its periphery so that it may be bolted to the backwall plate 33 as illustrated. This housing will clear the face of the brake drums with only a small clearance to prevent the line L or L' from jumping out of the sheave grooves in the drum which will be described. Sleeves 49 are located at each side of the base of this housing to provide guided passageways through which the line L, or L', extends.

Each drum-type brake 40 and 41 is essentially a conventional automotive brake, and one type suitable for the purpose at hand is known as a "two shoe adjustable electric brake" manufactured by the Kelsey-Hayes Company of Romulus Mich. Referring more particularly to FIGS. 5 and 7, the spindle 42, or 43, is formed as a square-sectioned, or round, bar having a length sufficient to carry the backing plate of the brake a short distance outwardly from the reinforcing channel 44. The extended end of this shaft is turned as at 50, to support ball bearing races 51 whereon a conventional hub 52 is mounted. The brake drum 53 is mounted upon this hub and the drum is also conventional excepting that its outer periphery is formed with a plurality of circumferential sheave grooves 54 to receive the cable forming the safety line L. Four such grooves are shown in the disclosed structure; however, this number of grooves can vary and can be one or more to accomplish the functions herein set forth. The spindle also holds a flange 55 near the channel 44 which carries the backing plate 56 of the brake.

The conventional assembly of braking components will include primary and secondary brake shoes 57, an anchor 58, holding springs 59 and an adjusting link 60. This brake is operated electrically and the brake drum 53 includes an armature plate 61, a flat, washer-like plate which is affixed to the brake drum by rivets 62. An electro-magnet 63 is carried on a lever 64 mounted upon the backing plate 56. This lever is pivoted at a cam 65 which spreads the brake shoes apart whenever the lever is pulled in either direction by the magnet 63 gripping the rotating armature plate 61. To complete this overall organization, an opening 66 is provided adjacent to the tension adjusting link to permit an adjusting wheel 67 on the link 60 to be rotated.

A significant feature of the present invention resides in the tipping of brake 41 to permit the drums to be arranged side by side and close together and at the same time permit the safety line L to extend through a sleeve 49 at one side of the brake unit, thence to wrap about the drums 40 and 41, and thence to extend through the other sleeve 49 without being askew with respect to the sheave grooves 54. The inclination of the spindle 43 from the normal of the backwall plate, as heretofore described, is such that the sheave grooves 54 at the bottom of the drum of tipped brake 41 are offset outwardly one full groove width with respect to the grooves of the drum of brake 40 but the grooves 54 at the top of the drums are in alignment. This offset, illustrated at FIGS. 4, 5 and 6 is arranged to permit the cable to be wrapped around the pair of drums in a progressive manner with each cable reach between the drums being aligned with the grooves of both drums.

Tracing the course of the safety line L from left to right at FIG. 4, it is to be noted that the outer reach of the wraps of the safety line L extends through a sleeve 49 at the left side of the base of the drum housing 47 and that this outer reach misses the drum of brake 40 completely, but extends to and turns 180° about the first outer groove of the drum of the brake 41 at the right side of the housing. The line at the top of the drum of brake 41 extends to and turns 180° about the first outer groove of the drum of brake 40. Thence the line extends from the bottom of that drum to and turns 180° about the second groove of the drum of brake 41; thence from the top of that drum to and 180° about the second groove of the drum of brake 40; thence from the bottom of that drum to and 180° about the third groove of the drum of brake 41; thence from the top of that drum to and 180° about the third groove of the drum of brake 40; thence from the bottom of that drum to and 180° about the fourth groove of the drum of brake 41; thence from the top of that drum to and 180° about the fourth groove of the drum of brake 40; and, thence the line extends to the right behind and past the bottom of the brake 41 and through the sleeve 49 at the left side of the braking unit. To miss the backing plate 56 of the brake 41, a notch 68 may be cut in the base of the plate, as shown at FIG. 6. It is to be noted that with the offsetting tilt of one brake with respect to the other, regardless of which brake is tilted, the reaches of the line between brake drums are in alignment with respect to the sheave grooves. The number of grooves and wraps about the two brake drums 53 will be selected to assure an adequate frictional grip upon the drums and prevent slipping of the safety line in the grooves about the drums whenever the system is operating. The design of a brake unit, to determine the proper number of sheave grooves 54 to prevent slipping, will take into account a number of factors including: the size of the safety line, the initial tension on the line, the loading to be imposed when the system is braked, the diameter of the brake drums and the coefficient of friction between the line and the drums. However, these factors can be established and a designer skilled in the art can easily solve the problem.

These brakes 40 and 41 in each safety brake unit and the two units B and B' must operate simultaneously to stop the safety lines L and L' from moving through them at the same time. To do this, the electro-magnets 63 in all four brakes are energized simultaneously by a common electrical system. An electrical circuit for energizing these magents is illustrated at FIG. 8. A battery 70 is connected to the four electro-magnets in parallel by a circuit loop 71. The battery will be selected to apply the proper voltage to each electromagnet, and with a battery of sufficient voltage, the magnets could be interconnected in series. The actuation of the brake, by energizing these electro-magnets 63, may be effected by closing any one of three normally open switches 72, 73 and 74 which are in the lead 71 in parallel. The operation of these switches will be hereinafter described.

The closing of any one of the three switches 72, 73 or 74 will also energize an interlock lead 75 shunting the reach of the lead 71 to the electro-magnets 63 to energize a solenoid 76 in that lead. This closes a normally open switch 77 which, in turn, also parallels switches 72, 73 and 74. Accordingly, whenever switch 77 is closed by energizing solenoid 76, the circuit 71 is locked and will continue to energize the electro-magnets 63 and solenoid 76. Thus, the circuit locks even if one of the switches 72, 73 or 74 is only momentarily closed.

A manually operated, normally closed switch 78 in the lead 75 is opened to break the interlock and de-energize the electro-magnets 63. The switch 72 is also manually operated to manually set the brakes. Both switches 72 and 78 are conveniently mounted in the cage as illustrated at FIG. 1.

The switch 73 is an emergency switch associated with the drawbar 25. Referring to FIG. 5, the drawbar is formed as an elongated clevis having a base 80 between two bars. A compression spring 81 is secured at the lower end of this clevis between the bottom of the drawbar and a stop bolt 82 on the anchor channels 32. This spring 81 urges the drawbar downwardly. The switch 73, mounted adjacent to the support frame 30, has an actuating lever which is engaged by downward movement of this drawbar as whenever the load is released from the cable. This could happen where the hoist cable is suddenly released or breaks, or where the operator is jerking the hoist cable.

The third switch 74 is closed by a governor of any suitable type which actuates whenever the rate at which the elevator is being lowered or raised exceeds a specified maximum. This governor 83 is conveniently associated with a brake 40 and it may be a conventional unit commonly known as a plugging switch which is controlled by a rotating shaft. The governor 83 is mounted upon a bracket 84 secured to the housing 47 to hold and axially align the shaft 85 of the governor with the brake drum 40. So positioned, the shaft is connected to the hub 52 as by a coupling 86 at FIG. 5. The switch 74, within the governor, is a conventional plugging switch which can be easily adjusted to close whenever the rate of rotation of the drum 40 becomes excessive.

The electrical circuit shown at FIG. 8 will include a charging circuit 87 shunting the battery 70 and having a rectifier 88 suitable for receiving an electrical plug-in to actuate the charging circuit. Other leads may also be included in this circuit to control various alternate components as hereinafter described.

Various modified arrangements of the system described above are possible. For example, the mine cage can include three or four safety brake units with a similar number of safety lines extending into the cage and through the units. Also, a single unit may be used as shown at FIG. 9 and is especially useful where the cage is operated in an inclined shaft, since an unbalanced load on the cage will not cause it to tip sidewise. The alternate construction of a cage C', shown in a somewhat diagrammatic manner, is substantially the same as that of cage C, shown at FIG. 1, having sidewalls 20, a floor section 21 and a roof 22. Other features, heretofore described but not shown at FIG. 9, may also be included. However, with only one safety line L and one braking unit B in the cage, it is expedient to align the braking unit vertically instead of horizontally as heretofore described. This permits the line L to extend directly through the cage without extending about sheaves on the wall of the cage. The reach of the line within the cage, below the safety drum and in the passenger section of the cage, is preferably passed through a tube 90 to protect the passengers therein.

As a further feature of this arrangement, the tube 90 may include a line-tensing brake 91 which functions to hold the line L whenever the braking unit B operates. The effective gripping of the line L by the brake drums 53 is a function of the tension on the reach of the line L below the brake unit and a gripping action by the brake 91 to increase this tension greatly increases the grip of the drums 53 on the line L wrapped about them. The brake 91 is electrically operated to operate simultaneously with the braking unit B and includes a backing shoe 92 at one side of the line L which is of iron or other magnetic-responsive material. An electrical armature 93 is carried at the other side of the line, as illustrated at FIG. 10. These members are mounted upon a plate 94 having slotted mounting holes 95 to permit one element to move with respect to the other. Whenever this armature 93 is energized, it moves toward the shoe to grip the line L between the two members. The grip is not sufficient to stop the fall of the cage, but the members do hold the line and apply tension to the portion of the line extending to the braking unit. The modification to the electrical circuit to include the armature 93 and to make it work in unison with the brakes is a simple matter of providing an extension 71' of circuit loop 71 to connect the armature 93 in parallel with the electro-magnets 63 as shown in broken lines at FIG. 8.

FIGS. 11 and 12 illustrate a modified construction for the safety brake units B and B' which provides a mechanical fail-safe braking actuator to lock the brakes 40 and 41 should the battery 70 become discharged to the point where it cannot effectively energize the electro-magnets 63. To install this mechanical fail-safe linkage, a modified pair of brakes 40' and 41' are used which are conventional electro-mechanical brakes and which are substantially the same as the brakes 40 and brake 41 heretofore described. The mechanical actuating mechanisms merely supplement the electrical mechanisms.

One way of mounting a mechanical component in an electrical brake is illustrated at FIGS. 5 and 7. The anchor point 58 is rotatable in the backing plate and a shaft stub 100 extends rearwardly and outwardly from this backing plate to connect with a lever arm to rotate the anchor. One end of each of the brake shoes 57 abuts against a cam 101 on the anchor 58 and accordingly, whenever the anchor 58 rotates, the cam spreads the brake shoes apart to set the brake. Other conventional arrangements of mechanical braking mechanisms may be provided, also using a stub shaft 100 which is rotated to set the brakes.

Where two safety brake units B and B' are used, a mechanical linkage is provided for each brake unit and the two linkages are interconnected to operate in unison as shown by the arrangement at FIGS. 11 and 12. The normal and tilted brakes 40 and 41 in each unit are mounted upon their respective spindle flanges 55 in a manner which places the stub shafts 100 in symmetrical opposing positions such as illustrated at FIG. 12. Lever bars 102 and 102' are affixed to the stub shafts 100 of the normal and tilted brakes 40 and 41 respectively. These levers upstand from their respective brakes in a common plane, but lever bar 102' is bent slightly as at 103 to compensate for the tilt of brake drum 41. The length of these lever bars is such as to extend them through an opening 104 in the top of the housing 47 to a position sufficiently above the housing to provide suitable operative clearances. Toggle links 105 and 106 are connected to the extended ends of the bars 102 by low friction pivot bearings 107 and are interconnected by a low friction pivot bearing 108 between the bars. The toggle 106 includes an extended, inwardly folded arm 109. The inwardly folded arms of each linkage of each safety brake unit B and B' are joined together at the center of the safety brake assembly, over the beam 30, to there interconnect and form a single lever 110.

Whenever the lever 110 is pulled downwardly, the toggle lever 105 and the toggle portion 106 of each arm 109 spreads the respective bars 102 and 102' apart. However, this spread is limited by abutments 111 in the opening 104 to a position where the toggle is not fully spread and thus is not locked. A tension spring 112 between these toggles urges them together and whenever the lever 110 is not held down, the tension springs will pull the levers 102 and 102' together, snapping the toggle and the lever 110 upwardly. Movement of levers 102 and 102' will rotate the stub shafts 100 to lock the brakes 40 and 41.

Accordingly, the mine cage cannot be operated unless the lever 110 is pulled downwardly and held downwardly so the toggle linkage will spread the arms 102 and 102' apart to release the brakes. This may be effected manually as by a pull cord 113 connected to the end of the lever 110 and extended through suitable holes 114 in the framework 30. The cord then extends downwardly and to the passenger section of the cage. Also, a solenoid 115 is mounted upon this framework 30, as upon a suitable base member 116 to engage an armature 117 on the control lever 110. Whenever the solenoid is energized by an electrical current and is engaged by the armature 117, the arm 110 is held in a downward position. Accordingly, whenever an operator wishes to use the mine cage and the brakes are mechanically set, he may energize the solenoid 115, as by closing a switch, and pull the lever 110 downwardly. If the electrical current through the solenoid 115 is insufficient to hold the armature, the lever 110 will snap upwardly setting the brakes and the operator then knows that the battery 70 of his electrical system has been discharged or that the system has a bad connection at the battery and cannot operate the electro-magnets 63 of the brakes in case of an emergency.

The electrical circuit to operate solenoid 115 may be a simple addition to the circuit illustrated at FIG. 8. A circuit lead 118 will connect in lead 71 shunting the battery 70 as shown in broken lines. This lead 118 will include, in series, the solenoid 115, a manually operated switch 119 and a warning light 120. When the mine cage is to be operated, the switch 119, indicated as being normally open, is closed to energize the solenoid 115 and to light the indicator light 120. Thereafter, when the cage is ready for operation, the lever 110 is pulled downwardly against the solenoid 115 and the emergency brake system will then be opened and may subsequently actuate through closure of switches 72, 73 or 74 as heretofore described. When the cage is not to be used for a period of time, switch 119 will be opened to de-energize the solenoid 115, release the arm 110, set the brakes and turn off the warning light 120.

I have now described my invention in considerable detail. However, it is obvious that others skilled in the art can build and devise alternate and equivalent constructions which are nevertheless within the spirit and scope of my invention. Hence, I desire that my protection be limited, not by the constructions illustrated and described, but only by the proper scope of the appended claims.