Brakes – With condition indicator – Wear
Reexamination Certificate
2001-03-13
2003-10-21
Graham, Matthew C. (Department: 3683)
Brakes
With condition indicator
Wear
C188S071100, C188S170000, C188S171000
Reexamination Certificate
active
06634465
ABSTRACT:
The invention relates to a spring-loaded brake with a first housing section connected to a first brake shoe and a second housing section connected to a second brake shoe and with an actuation device, by means of which the first and the second housing section are capable of movement relative to one another. Such spring-loaded brakes are used, for example, for the securing of drive trains, in order to prevent the risk that, in the event of an operational fault, the machines connected to the drive trains run uncontrolled and wild. Thus, for example, spring-loaded brakes are used in particular on conveyor belts or chain conveyors, with which bulky material mined underground, such as coal, rock, or ore, is conveyed over long transport distances. With these devices, spring-loaded brakes prevent the risk that, in the event of a failure in the drive system, the belt with the material lying on it runs back uncontrolled along the conveying stretch or starts running under its own dynamic forces.
For this purpose, known spring-loaded brakes are equipped with an actuation device, designed as a rule as a spring package, by means of which the brake shoes, mounted on bearings in a jointed manner, equipped in each case with a brake lining, will automatically be moved into the braking position in the event of the removal of a counter-force applied via the brake caliper arm.
The advantage of the known spring-loaded brakes consists of the “fail-safe behaviour” explained heretofore, by means of which it can be ensured that a braking effect will always be reliably applied even if no further external energy sources are available for creating the braking force. Problems arise, however, in that the brake linings of the brake shoes are subject to wear. This wear depends on the frequency of the braking procedures, the braking time, and the scale of the braking force taking effect in each case. With increasing wear of the brake linings, the path increases over which the housing parts must be moved against one another, in order to reach the braking position. The consequence of this is that, if a spring package is used, the braking force of the braking device likewise decreases as the wear increases. For this reason it is necessary for the wear on the brake linings to be monitored and for the tension of the spring package to be adjusted. If an excessive degree of wear is detected, the connection between the housing parts and the spring package is adjusted in such a way that the braking force lies at the maximum permissible limit value.
In order to avoid manual adjustment, the principle is known of providing for a fluid-filled pressure buffer between the actuation device and at least one of the housing parts. This pressure buffer is connected to a pressure storage vessel, in which fluid is stored under pressure. In such a system, in the event of the braking force dropping because of wear, the fluid buffer is filled up with fluid under pressure to such a degree that the reduction in braking force caused by the wear is compensated for. In this way, the decrease in braking force otherwise inherent with brake wear will be automatically compensated for, and it will be ensured that the same braking force will still be uniformly available in the event of a fault.
In order to avoid overheating of the brake disks due to the brake linings chafing them or coming in contact with them during the operation of the drive, and therefore to a large extent avoiding the risk of fire, it is necessary for the air passage of the brake linings to be monitored, so that the risk can be avoided of the machine being started with inadequately vented brakes. For this purpose, the known spring-loaded brakes are equipped with an eccentric disk, which is connected to one of the housing parts. A limit switch is provided on the other housing part, by means of which, for example, the energy supply of a motor is controlled. The eccentric disk in this situation is adjusted in such a way that the limit switch is closed and the motor supplied with energy when the spring-loaded brake is vented, i.e. is out of action. If the limit switch is not reached, the motor must be prevented from starting.
This combination of limit switch and eccentric disk does indeed allow for the control of a motor with simple and robust means. It is however impossible in this manner to monitor the wear of the spring-loaded brake reliably in such a way that, on the one hand, a signal is always received relating to the need for the brake linings to be replaced, and, on the other hand, the brake linings can also be used for an optimum period of time. In addition to this, the mechanical elements of the limit switch/eccentric disk combination have proved in practice to be prone to failure, since on the one hand they must be freely accessible for adjustment and readjustment purposes, and, on the other, they are always subject to the risk of damage due to falling material. In addition to this, the wilfully or unintentionally incorrect setting of the eccentric disk may lead to faulty function of the limit switch.
In addition to the prior art known from practice, as described heretofore, a brake caliper unit is known from DE 195 14 463 C1, of the generic type of the invention, for the disk brakes of vehicles, and railed vehicles in particular, in which one brake caliper arm is connected directly to the housing and the other brake caliper arm is connected by means of a gear system. With this known brake caliper unit, too, the problem arises of identifying wear of the brake lining in good time, and of avoiding malfunction of the brake in the event of inadequate venting.
The objective of the invention is of creating a spring-loaded brake of the type referred to in the preamble, in which the air passage and the wear can be monitored reliably and in a simple manner.
This objective is achieved according to the invention in that a spring-loaded brake of this type is equipped with a measuring device, which continually monitors the change in the relative position of the housing parts.
With a spring-loaded brake designed according to the invention, continuous monitoring of the relative position of the housing parts can be effected. In this way, information is always available from which can be derived, on the one hand, the air passage which is covered in each venting procedure, and, on the other, the current state of wear of the brake linings in each case. This makes it possible, with low technical effort, to make an assessment at any time of the air passage, the state of wear, and, inherently associated with this, of the functionality of the spring-loaded brake. It is accordingly possible to display, with a high degree of reliability, the position of the brake shoes in the vented state. With equally high precision, the moment of time can also be determined at which the replacement of the brake linings is in fact required.
By means of the continuous acquisition of the relative position of the housing parts, made possible by the invention, assessments can be made of the effective size of the air passage covered during each venting procedure. These signals form the basis for the generation of control signals for the operation of the drive system connected to the brake equipped according to the invention. If it is ascertained, for example, that the air passage is too small, the drive is not allowed to start up. On the other hand, the risk pertains that overheating of the brake may occur due to chafing brake shoes. If it is ascertained, by contrast, that the air passage is too large, this means that a readjustment of the air passage limits must be carried out.
In the braked position, too, the measuring device provided for according to the invention supplies a signal which is important for the assessment of the operational state.
For example, it is possible to conclude from the position of the brake caliper arms, determined by means of the measuring device in the braked position, whether the brake shoes of the brake are showing sufficient strength.
It is no longer necessary to make an adjustmen
Graham Matthew C.
Proskauer Rose LLP
Tüschen & Zimmermann
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