Abstract:
A remote brake release for elevator drive machine brakes includes a release lever attached to a shaft coupled by a clutch to a bellcrank. The clutch is normally engaged and can be a spring clutch or a friction type disc clutch. Movement of the lever to rotate the shaft moves the bellcrank which is coupled to a brake release mechanism. A solenoid is actuated to disengage the clutch preventing release of the brake. The solenoid can be connected to a control circuit responsive to a speed of rotation of the drive machine motor.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to braking systems for elevators and, in particular, to an elevator remote brake release with a clutch. 
     Elevators and their associated mechanical components are well known. Elevators are used to move people and things between floors in multistory buildings. A conventional traction type elevator application includes an elevator car attached to a counterweight via a suspension cable, and a drive machine rotating a traction sheave that is engaged with the cable. As the drive turns the sheave, friction forces between the grooved surface of the sheave and the cable cause the car and counterweight to oppositely raise and lower in a hoistway. A brake associated with the drive is used to slow and stop the car. The drive machine and the brake are typically located in a machine room accessible by maintenance personnel. The machine room can be located at the top or the bottom of the hoistway or adjacent to the hoistway. 
     Elevators are also provided with control systems that perform various functions for ensuring smooth and safe operation of the elevator including operating the drive machine and the brake. Advances in elevator technology have led to the development of mini-machine-room or machine-room-less (MMR/MRL) elevator applications. As their names imply, these types of elevator mechanical systems employ very small machine rooms or no machine rooms at all. MMR/MRL elevator applications have the goal of reducing the amount of building space occupied by the elevator systems and thereby increasing the amount of usable space on the floors, and are becoming more and more common. 
     The brake is a major component of the electrical mechanical and control systems. The brake is utilized in normal operation for arresting the movement of the elevator car, but also is engaged in emergency situations in order to prevent the car from moving within the hoistway. Brakes typically utilize a spring or clutch mechanism with accompanying wear plates that engage with a drum area on the drive motor, or alternatively with a cylindrical brake drum that is attached to the suspension cable, in order to stop the movement of the elevator car. 
     Elevators are provided with numerous safety systems in addition to the basic mechanical components and control systems described above. Safety systems generally contain sensors that monitor the condition of the mechanical components or the operation of the control systems. The safety systems are engaged whenever the mechanical components or control systems are operating in a manner to meet or exceed preset limits for safety, and may utilize the brakes to stop the movement of the elevator car. The safety systems may also stop operation, for example by disconnecting power, of the drive and control system, where feasible. 
     In emergency situations, the brake is typically engaged so that the elevator car remains stationary in the hoistway. When this occurs, the elevator car may be between floor levels. It is desirable to be able to move the car short distances, for example to the adjoining floor, so that any occupants can exit the car safely and/or maintenance personnel can enter the car. The elevator car is moved by overriding the application of the brake using an emergency brake release. In many prior art systems, the emergency brake release could only be activated from the machine room, making the process both time-consuming and inefficient. 
     It is especially desirable for the brake release to be actuated remotely so that maintenance personnel can actuate the brake release without having to enter the machine room. Furthermore, in MMR/MRL elevator applications the drive machine and the associated brake are not easily accessible. Prior art patents have recognized this desirability. The U.S. Pat. No. 5,526,902 describes a means for utilizing a brake release from inside the elevator car. The U.S. Pat. No. 5,971,109 describes the remote operation of brake release by utilizing linkage from the interior of the car, or alternatively, from another space adjacent to the elevator shaft but remote from the machinery space. 
     The prior art noted above, however, does not contemplate the fact that an emergency situation may occur or that the elevator car may move too quickly after the brake release has been engaged. For example, an overspeed condition may occur after the brake has been released, and the prior art shows no way to reengage the brake in order to prevent a catastrophic failure or at least an undesirable condition from occurring. 
     It is desirable to provide a remote brake release that has the ability to be disengaged, and to reengage the elevator brake if an emergency condition, such as an overspeed condition, is detected. 
     It is an object of the present invention, therefore, to provide a safe and efficient means of remotely releasing a drive machine brake on applications where the drive machine and the brake are not accessible. It is another object of the present invention to increase the safety of the entire elevator application by integrating the brake release mechanism with an overspeed detection system. 
     SUMMARY OF THE INVENTION 
     The brake release apparatus according to the present invention provides a safe and efficient means of remotely releasing a drive machine brake on applications where the drive machine and brake are not accessible, which is typical of Machine Room Less (MRL) and Mini Machine Room (MMR) applications. The advantage of this invention over the prior art is that it provides a means of automatically disengaging the remote brake over-ride should an overspeed condition be detected. Once disengaged, the standard return springs on the drive machine brake cause the brake to re-apply thus slowing and stopping the car. 
     The brake release apparatus according to the present invention includes a solenoid and simple spring clutch to engage or disengage an emergency brake release. A brake release lever is located where it may be accessed by a qualified elevator service technician. Rigidly attached to the brake release lever is a shaft. A spring clutch is fitted around the end of the shaft. A second shaft is also fitted into the spring clutch and is then connected to a bellcrank and from there to a cable. The cable is attached to the brake on the drive machine. 
     The spring clutch is a simple helical spring made from rectangular spring wire. It is preferably fit to the two shafts with a slight interference fit (approximately 0.1 mm). Pulling down on the brake release causes the brake release lever shaft to rotate. The spring (right hand or left hand) is selected such that pulling down on the brake release lever causes the spring to wind tighter onto the bellcrank shaft thus transmitting torque to the bellcrank. Pushing up on the lever causes the spring to unwind, releasing the spring and preventing torque transmission. 
     One end of the spring is fastened to the brake release lever shaft. The other end of the spring is free. The free end has a small pad that can be engaged by a solenoid or other similar device. The purpose of this arrangement is that the solenoid can then be used to disengage the clutch should an overspeed condition be detected. It does this by pushing on the pad and unwinding the spring. This clutch and solenoid arrangement is known in the art as a “normally engaged” clutch. 
     The present invention can be practiced in arrangements other than mechanical actuation of the brake release and electrical actuation upon an overspeed detection. Other arrangements are possible by varying the hand of the spring, the fixation locations (and methods) of the spring to the shafts and the control circuit logic. 
     In an alternative embodiment, the present invention may also be practiced with a “normally disengaged” device using the same elements. In place of an interference fit, the spring would have a clearance fit to the shaft on the brake release lever. The solenoid would be located on the brake lever side of the spring. To actuate the emergency release, the solenoid would extend and push on the spring tab. This would cause the spring to wind “down” on the brake release shaft. Torque in the shaft would then be transmitted to the brake. 
     In another alternative embodiment, the present invention makes it possible to eliminate the free rotation that will occur in the brake release lever when the solenoid disengages the clutch. A second spring can be added between the brake lever and ground. This second spring would be “normally disengaged”. The solenoid would actuate both springs, causing the spring between the emergency brake lever and the brake to disengage, and causing the spring between the brake release lever and ground to engage. 
     Finally, the present invention is not limited to the use of spring clutches. A friction type disc clutch could be used instead of the spring clutch. 
     The present invention advantageously combines an overspeed protection with the brake release mechanism, providing an additional level of safety with the elevator operation and maintenance. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     The above, as well as other advantages of the present invention, will become readily apparent to those skilled in the art from the following detailed description of a preferred embodiment when considered in the light of the accompanying drawings in which: 
     FIG. 1 is a perspective view of a remote brake release apparatus in accordance with the present invention; 
     FIG. 2A is a perspective view and FIG. 2B is an elevation view of an alternative embodiment of the remote brake release apparatus in accordance with the present invention; and 
     FIG. 3 is a schematic block diagram of a control system for a remote brake release apparatus in accordance with the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to FIG. 1, a remote brake release is indicated generally at  2 . The brake release  2  is intended to be operated by a qualified elevator service technician. The brake release  2  includes a brake release lever  4  having an end rigidly attached to one end of a first brake release shaft  6  such that the lever extends longitudinally transverse to an axis of the shaft. A spring clutch  8 , in the form of a helical spring, is coupled to an opposite free end of the first brake release shaft  6  and to a free end of a second brake release shaft  10 . The spring clutch  8  is preferably coupled to the shafts  6  and  10  with a slight interference fit to function as a “normally engaged” clutch. The shafts  6  and  10  are axially aligned. The second brake release shaft  10  has an opposite end rigidly attached to a bellcrank  12  adjacent one end thereof such that the bell crank extends longitudinally transverse to the shaft. A brake releasing means  14 , shown here as a cable, is attached adjacent an opposite end of the bellcrank  12 . 
     The spring clutch  8  is constructed so that when the brake release lever  4  is moved in a releasing direction depicted by an arrow  16 , the spring clutch  8  tightens around the shafts  6  and  10  so that the torque from the brake release lever  4  is transmitted to the bellcrank  12 . Conversely, if the brake release lever  4  is moved in an engaging direction depicted by an arrow  18 , the spring clutch  8  loosens from the shafts  6  and  10  so that no torque from the brake release lever  4  is transmitted to the bellcrank  12 . 
     The brake releasing means  14  is preferably a control cable or the like. The brake releasing means  14  is further attached to a drive machine brake (not shown), utilizing the torque transmitted from the brake release lever  4  to release the spring tension of the brake return springs (not shown) on the friction pads (not shown) of the brake. 
     A pad  20  is attached to an end of the spring clutch  8  engaging the shaft  10 . The pad  20  cooperates with a shaft or plunger  22  of a solenoid  24 . When a control or safety system (not shown) detects an emergency condition, the control or safety system sends a signal (not shown) to energize the solenoid  24 . When the solenoid  24  is energized, the shaft  22  extends in a direction  26  and pushes on the pad  20 . By pushing on the pad  20 , the shaft  22  unwinds the spring clutch  8 , and does not allow torque to be transmitted from the brake release lever  4  to the bellcrank  12  and the brake releasing means  14 . 
     Referring now to FIG.  2 A and FIG. 2B, an alternative embodiment of a remote brake release is indicated generally at  30 . The remote brake release apparatus  30  includes a brake release lever  32  having an end rigidly attached to one end of a brake release shaft  34  such that the lever extends transverse to the shaft. The brake release shaft  34  can be attached to or form a plunger of a solenoid  36 . A friction type disc clutch indicated generally at  38  is mounted on the brake release shaft  34 . The clutch  38  includes a spring pack  40 , a spring retainer  42 , a clutch pack  44  and a thrust washer  46 . The clutch pack  44  preferably contains a plurality of friction pads members or the like for gripping a bellcrank  48  that is positioned between the members of the clutch pack  44 . The bellcrank  48  has an end with an aperture through which the shaft  34  passes. The spring pack  40  is normally compressed so that the clutch pack  44  is compressed against the bellcrank  48 . A movement of the brake release lever  32  in a releasing direction depicted by an arrow  50 , therefore, rotates the shaft  34  and the coupled bellcrank  48 . An opposite end of the bellcrank  48  is attached to a brake releasing means  52 . 
     The brake releasing means  52  is preferably a control cable or the like. The brake releasing means  52  is further attached to the drive machine brake (not shown), preferably utilizing the torque transmitted from the brake release lever  32  to release the spring tension of the brake return springs (not shown) on the friction pads (not shown) of the brake. 
     When a control or safety system (not shown) detects an emergency condition, the control or safety system sends a signal (not shown) to energize the solenoid  36 . When the solenoid  36  is energized, the shaft  34  moves in an energized direction depicted by an arrow  54 . When the shaft  34  moves in the energized direction  54 , the spring pack  40  is decompressed and releases its grip on the bellcrank  48 . In the released state, torque is not transmitted from the brake release lever  32  to the bellcrank  48  and the brake releasing means  52 . 
     Referring now to FIG. 3, a control system of the remote brake release apparatus according to the present invention is indicated generally at  60 . The control system  60  can be used with the remote brake release  2  shown in FIG.  1  and with the remote brake release  30  shown in FIGS. 2A and 2B. A drive machine brake  62  is attached to a drive motor  64 . The speed of the drive motor  64  is monitored by an encoder  66 , which supplies a voltage signal, in proportion to the speed of the drive motor  64 , to one input of a comparator  68 . The encoder  66  is preferably a position encoder, a speed encoder or a generator similar to those used on bicycle headlamps. A reference voltage supply  70  supplies a reference voltage to another input of the comparator  68 . The comparator  68  compares the signal from the reference voltage supply  70  to the signal from the encoder  66 . If the signal from the encoder  66  exceeds a preset value in relation to the reference voltage supply  70 , the comparator  68  will provide a signal to an amplifier  72 , which is connected to an output of the comparator  68 . The amplifier  72  processes the output signal from the comparator  68 , and provides a voltage to a solenoid  74  which can be the solenoid  24  or the solenoid  36 . The solenoid  74  disengages a clutch  76 , which can be the clutch  8  or the clutch  38 . The clutch  76  is positioned between a release lever  78 , which can be the lever  4  or the lever  32 , and the brake  62 . The brake  62  is then reengaged and the brake springs (not shown) and friction pads (not shown) then stop the drive motor  64 . 
     In accordance with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiment. However, it should be noted that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope. For example, the present invention can vary the type of clutch utilized, the type of solenoid utilized, as well as other alternatives of control circuit logic utilized.