HOLDING BRAKE FOR AN ELEVATOR

Abstract: Holding brake for an elevator, comprising a brake body (1), a movable frame (2) movably supported on the brake body, a brake pad (3) attached to the movable frame, an electromagnet (5) mounted on the brake body to draw the movable frame toward the brake body, and a compressing element (11) designed to move the movable frame away from the brake body and to press the brake pad attached to the movable frame against a braking surface (4), said holding brake comprising a hydraulic circuit resisting the motion of the movable frame.

Description: HOLDING BRAKE FOR AN ELEVATOR The present invention relates to a holding brake for an elevator, as defined in the preamble of claim 1. Moreover, the invention relates to the use of a hydraulic release device as mentioned in claim 10. The function of the holding brake of an elevator is to keep the elevator car immovable at a floor and to stop the car when necessary, e.g. in the event of a power failure. Therefore, the braking action is based on the use of a mechanical compressing element, such as a spring, which keeps the brake in position when it is not subject to the action of any external forces. Considering elevator passengers, the operation of the brake of the elevator must be as fast, accurate and noiseless as possible. Therefore, the air gap between the brake pad of the holding brake and the braking surface of the traction sheave or a separate brake wheel must be as small as possible. Thus, the braking action is fast and the impact energy of the brake shoe remains low while the braking noise is minimized. The braking force of the holding brake, i.e. the com- pressive force of the spring used in it has to be relatively large to allow optimal operation of the brake. The impact of the brake shoe against the braking sur- face generally tends to produce some kind of noise or vibration. Also, when the mechanical spring is compressed at release of the brake, a noise is produced as a result of the impact between the brake body and the movable frame. There is good reason to continue efforts towards developing different solutions for damping the above-mentioned kinds of impact noise. Finnish patent application no. FI 982788 proposes an idea of damping the noise produced by the operation of the holding brake by the use of a separate damping ele- ent made of an elastic material, placed between the movable frame and the brake body. The object of the present invention is to achieve a new type of holding brake. A specific object is to disclose a structure in which a hydraulic brake releasing system is utilized for damping the movements of the brake and the noise produced by it. The holding brake of the invention comprises a hydraulic circuit which resists the motion of the movable frame. As for the features characteristic of the invention, reference is made to the claims. As compared with previous solutions, the invention has the advantage of low manufacturing costs as it combines a brake releasing device and a damper in the same physical device. Another advantage is that the structure of the brake system can be implemented in various ways. A further advantage is that the same apparatus is used to effect damping both in the releasing direction and in the closing direction. The movements of the mov- able frame during braking are small, and the apparatus of the invention produces an accurate braking action without a delay. The apparatus of the invention also makes it possible to avoid malfunctions produced by backlash. One of the advantages is also the fact that the brake releasing device and the brake damper share the same fluid supply. The structure of the invention is preferably implemented by integrating certain parts of the hydraulic circuit in the piston. On the other hand, the components of the hydraulic circuit will be more easily accessible for servicing and maintenance when placed in separation from the brake body. A further advantage of the invention is that it uses a tank circuit in conjunction with the hydraulic circuit to eliminate leakages and wear of gaskets . The tank cir- cuit is preferably so constructed that it shares with the hydraulic circuit the same fluid pipe leading to a release pump, thus obviating the need for a separate pipe to connect the tank circuit to the release pump. In the following, the invention will be described in detail by referring to the attached drawings, which present a holding brake for an elevator according to the invention. Fig. 1 presents a general view of a traction sheave elevator. Fig. 2 presents a partially sectioned holding brake of an elevator, with a brake releasing cylinder and a damping hydraulic circuit and a tank circuit integrated with it. Fig. 3 presents a somewhat different implementation of the apparatus presented in Fig. 2, with certain parts of the hydraulic circuit machined in the piston. Fig. 1 presents a traction sheave 51 provided with a motor and transmitting a force via ropes 53 to an elevator car 54 and a counterweight 55. Placed against the braking surface of the traction sheave are two holding brakes 52. The figure visualizes the placement and operation of the holding brake. The holding brake 52 presented in Fig. 2 comprises a brake body 1 with a movable frame 2 movably mounted in it. A brake pad 3 engaging the braking surface 4 of the traction sheave 51 is attached to the outer surface of the movable frame. The brake body houses an electromagnet 5 exerting a force of attraction between the brake body 1 and the movable frame 2. Fixed to the movable frame 2 is a lifting element, such as a lifting arbor β . Placed between the brake body 1 and the movable frame 2 is a compression means, such as a mechanical spring 11, composed of e.g. disc springs, serving to move the movable frame 2 away from the brake body 1 and to press the brake pad 3 against the braking surface 4. Built in conjunction with the holding brake 52 is a brake releasing unit, which comprises a piston 7 at- tached to the lifting arbor 6 and serving to produce a hydraulic pressure to force a fluid from a brake release cylinder 12 into ducts kl and k2 comprised in a separate hydraulic circuit resisting the motion of the movable frame 2. The ducts kl and k2 communicate with chokers vl and v2 , which damp the fluid flow and therefore the impact noise produced by the braking action. The hydraulic circuit comprises a mechanical release device 8, by the operation of which the brake fluid is caused to flow from the tank 9 of the release device via a release pump 10 into spaces above and below the piston 7, said spaces being partially defined by unequal areas Al and A2 above and below the piston. Connected to the hydraulic circuit is a tank circuit 13 to prevent fluid leakage from the brake releasing cylinder 12 and to prevent wear of the gaskets . By using a damping hydraulic circuit, it is possible to combine a brake releaser and a damper in the same device. When the brake is being released mechanically e.g. during a power failure, the electromagnet 5 being inoperative, the fluid pressure.is passed from the container 9 of the release device 8 via the ducts kl and k2 into the spaces on either side of the piston 7. The brake is released as the piston 7 is pushed upward by the pressure developed in consequence of the difference between the areas of the upper and lower sides of the piston 7. When the brake is being released using the brake releasing device, the pressure above the piston 7 tends to increase in consequence of the movement of the piston 7 because pressure balancing in the system is retarded by the gasket between the upper and lower sides of the piston and by the choker vl. The sealing of the spaces above and below the piston 7 toward the tank circuit 13 may leak considerably. In this case, an amount of fluid is forced to flow past the gasket around the upper part of the piston into the tank cir- cuit 13, with the result that the pressure is equalized and the releasing delay is significantly shortened. When the brake is released by means of the electromagnet 5, the latter attracts the movable frame 2 and the brake body 1 toward each other, with the result that the brake pad 3 starts moving upward while at the same time the upper side of the piston 7 is forcing some fluid into duct kl, where the flow is damped by choker vl, and therefore the impact noise produced as the movable frame 2 and the brake body 1 hit against each other is damped while the kinetic energy is converted into thermal energy. The fluid coming from the upper side of the piston 7 circulates to the lower side of the piston 7, but, since the area A2 on the lower side is larger than the area Al on the upper side, an amount of fluid from the container 9 of the release pump 10 flows in to make up the deficit. As the brake is released, the fluid coming from the release pump 10 flows past choker v2. When the brake is closed, the action of the electromagnet 5 ceases and the mechanical spring 11 of the brake presses the movable frame 2 and the brake pad 3 attached to it downward toward the braking surface 4. At the same time, the piston 7 forces an amount of fluid from below into duct k2 , from where it flows via choker vl to the upper side of the piston 7, damp- ing the impact noise produced as the brake pad 3 hits against the traction sheave 51. After that, due to the difference between the areas Al and A2 of the upper and lower sides of the piston, the fluid flows via choker v2 back into the container 9 of the release device 8. The fluid leaking past the gasket in the lower part of the piston 7 flows into the tank circuit 13, so it will not harm the brake system below or cause wear of the other gaskets . Fig. 3 presents the apparatus of the invention shown in Fig. 2 using a somewhat different implementation. Fig. 3 only differs from Fig. 2 in . that the fluid circulation between the spaces partially defined by the upper and lower sides Al and A2 of the piston has been implemented by drilling a duct kl in the piston 7, the choker vl damping the impact noise being placed in this duct. The apparatus according to Fig. 3 also has no tank circuit. Thus, the damping hydraulic circuit of the invention can be integrated with the piston 7 in the brake releasing cylinder 12 e.g. by drilling a hole in the piston 7. As a result, the fluid circulating be- tween the upper and lower sides of the piston 7 would flow through this drilled hole. If the hole is small enough, it will constitute a good choker limiting the flow. It is also possible to place a separate choker in the drilled hole. Another possibility is to provide a fluid flow path at the side of the piston. The invention can be implemented in conjunction with the brake in many ways without departing from the inventive idea. For instance, the duct kl connecting the spaces partially defined by areas Al and A2 as well as the choker vl can be machined in the piston 7 and the pressure balancing duct together .with the chokers vl and v2 can be connected directly to one of the spaces partially defined by areas Al and A2. The chokers used to restrict the flow may also be placed in a separate unit by the side of the brake releasing cylinder 12.

Claims: CLAIMS 1. Holding brake (52) of an elevator, comprising - a brake body (1) - a movable frame (2) movably supported on the brake body, - a brake pad (3) attached to the movable frame, - an electromagnet (5) mounted on the brake body to draw the movable frame toward the brake body and a compressing element (11) designed to move the movable frame' away from the brake body and to press the brake pad attached to the movable frame against a braking surface (4) , characterized in that the holding brake comprises a hydraulic circuit resisting the motion of the movable frame (2) . 2. Holding brake (52) as defined in claim 1, characterized in that it has a hydraulic actuator comprised in the hydraulic circuit and connected to the movable frame (2), by means of which actuator the brake can be released. 3. Holding brake (52) as defined in claim 2, characterized in that the actuator is a brake releasing cylinder (12) containing a piston (7) for moving the movable frame (2), said piston having on its upper and lower sides unequal areas (Al, A2) meeting the fluid in the brake releasing cylinder (12) . 4. Holding brake (52) as defined in claim 3, characterized in that it comprises a fluid path between the upper and lower sides, with a choker (vl) placed in said path. 5. Holding brake (52) as defined in claim 3, characterized in that the hydraulic circuit comprises a fluid container (9) and that there is a choker (v2) between the fluid container (9) and the piston (7) . 6. Holding brake (52) as defined in any one of the preceding claims, characterized in that the hydraulic circuit comprises a separate release device (8) provided with a container (9), from where, using a release pump (10) , the fluid can be caused to flow to different sides of the piston (7) . 7. Holding brake (52) as defined in any one of the preceding claims, characterized in that the hydraulic circuit is a separate unit in connection with the holding brake (52) . 8. Holding brake (52) as defined in any one of claims 1-7, characterized in that at least part of the hydraulic circuit has been machined in the piston (7) . 9. Holding brake as defined in any one of the preceding claims, characterized in that it comprises a tank circuit (13) integrated with the hydraulic circuit to eliminate leakages and the wear of gaskets . 10. Use of the hydraulic circuit or part of the hydraulic circuit of a hydraulic device for releasing the holding brake (52) of a traction sheave elevator to reduce the noise produced by the release and/or closing of the brake. 11. Use as defined in claim 10, characterized in that the hydraulic circuit or a part of it is designed to provide a resistance to the motion of the brake.

Inventors: MUSTALAHTI JORMA, MUSTALAHTI, JORMA
Applicants: KONE CORP, MUSTALAHTI JORMA, KONE CORPORATION, MUSTALAHTI, JORMA
Application year: 2001
Main classification: B66D5
IPC codes: B60T13, B66D5, F16D49, F16D65