Braking system

A braking system having a brake disc and a brake plate. The brake disc and brake plate each include three plateaus that include ramps on each end. The plateaus of the brake disc are configured to substantially mate with the plateaus of the brake plate.

BACKGROUND OF THE INVENTION

The present invention relates to braking systems and particularly to dynamic braking systems. More particularly, the present invention relates to braking systems utilizing the engagement of a brake plate against a brake disc to brake a rotating shaft.

Conventional braking systems typically include a brake disc that rotates with a rotating shaft and a brake plate that engages the brake disc to brake the disc and thereby slow and stop movement of the shaft. The rotating shaft may be a vehicle axle, a component of a powered door hinge, or any other rotating shaft that requires braking. The brake plate brakes the brake disc by relying either on friction between a face of the brake plate and a face of the brake disc or through positive mechanical engagement of teeth on the brake plate and corresponding teeth on the brake disc.

SUMMARY OF THE INVENTION

Conventional braking systems that rely on friction can be unreliable in high-vibration environments where the spring or other mechanism that supplies the normal force between the brake disc and the brake plate relieves itself under the vibratory conditions and decreases the frictional force. Conventional braking systems that utilize the positive mechanical engagement of teeth on the brake disc and brake plate can suffer significant damage in high-velocity and high-vibration environments. The teeth of the brake disc or brake plate or both can break off in such environments. A braking system that provides and maintains sufficient braking force in a relatively high velocity, high-vibration environment will be welcome by users of such braking systems.

According to the present invention, a braking system is provided for braking a shaft mounted for rotation that includes a brake disc, a brake plate, and a spring. The brake disc is coupled to the shaft for rotation therewith and includes a disc face having a plurality of disc plateaus positioned around the circumference of the disc. Each disc plateau includes a disc ramp extending between the disc face and a top surface of the disc plateau. The brake plate is relatively stationary; thus, the brake disc rotates relative to it. The brake plate includes a brake face positioned substantially parallel and adjacent to the disc face and includes a plurality of plate plateaus corresponding to the number of disc plateaus. Each plate plateau includes a plate ramp extending between the plate face and a top surface of the plate plateau. The plate ramps are angled relative to the plate face at the same angle at which the disc ramps are angled to the disc face. Recesses defined between consecutive plate plateaus are dimensioned to correspond to the disc plateaus such that the disc plateaus mate with the recesses. A spring biases the disc face against the plate face.

Additional features and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description exemplifying the best mode of carrying out the invention as presently perceived.

DETAILED DESCRIPTION

Referring toFIG. 1, a braking system10according to the present invention includes a brake disc12, which engages a brake plate14. The brake disc12is coupled to an insert17that is coupled to a shaft16. The shaft16is mounted in a sleeve54and bearing56combination for rotation with respect to a base member18that is relatively stationary within the system10. By “relatively stationary” it is meant that the base member18does not rotate (as discussed below it does translate slightly) with respect to the majority of the parts of the system10or the overall device that utilizes the braking system10. On the other hand, the shaft16does rotate with respect to the majority of the parts of the system10and the overall device.

Mounted for rotation, the shaft16could act as any of a number of things, including the hinge of an aircraft door or the axle of a vehicle, such as an airplane, etc., that creates a high-velocity, high-vibration environment. The brake plate14is mounted to the base member18. Therefore, when the shaft16(along with the insert17) rotates, the brake disc12rotates relative to the brake plate14. A series of springs20bias the brake plate14against the brake disc12to provide a normal force between the two that engages the brake plate14with the brake disc12and brakes the shaft16. The specifics of the engagement between the brake plate14and the brake disc12will be further discussed below. Some of the springs20include adjustment screws48that can be turned to adjust the force applied on the base member18by the springs20.

With the braking system10positioned as shown inFIG. 1, the system10provides a braking force on the shaft16. To release the braking force, power is supplied through cables50to a coil52. When power is supplied to the coil52, a magnetic field is created that attracts the base member18toward the coil52with sufficient force to overcome the force of the springs20. The base member18is designed and constructed of metal to respond to the magnetic field created by the coil52. As discussed above, the brake plate14is mounted to the base member18and, therefore, when the coil52is powered, the brake plate14also moves towards the coil52. This moves the brake plate14out of engagement with the brake disc12. If power to the coil52is lost or intentionally cut, the springs20again take over and force the brake plate14into engagement with the brake disc12. Thus, the system10is considered “fail-safe” in that the system10brakes (i.e., engages the brake plate14to stop rotation of the shaft16) if power is lost. However, it will be apparent to those of ordinary skill in the art that the system10could be designed to be “fail-secure” wherein the system10brakes when power is supplied to the coil52.

Referring toFIG. 2, the brake disc12includes a connection hub22that is coupled to the insert17and, in turn, the shaft16. The brake disc12is generally circular and includes a disc face24having three disc plateaus or disc teeth26projecting therefrom. Each disc plateau26includes two disc ramps28transitioning between the disc face24and a top surface30of the disc plateau26.

The disc plateaus26are arranged generally around the circumference of the brake disc12and are equally spaced approximately 120° from each other. The disc plateaus26are sized so that they cover approximately one-half of the total circumference of the brake disc12. Between consecutive disc plateaus26, disc recesses32are created and cover approximately the other half of the circumference of the brake disc12. The disc ramps28are angled approximately 10° relative to the disc face24to create a relatively shallow transition between the disc recesses32and the top surfaces30of the disc plateaus26.

Referring toFIG. 3, the brake plate14has a plate face34, including a series of plate plateaus or plate teeth36that generally correspond to the disc plateaus or disc teeth26, discussed above. As with the disc plateaus26, the plate plateaus36, which include plate ramps38angled at approximately 10°, extend between the plate face34and a top surface40of the plate plateaus36. In the illustrated embodiment, the disc ramps28and plate ramps38are angled at the same angle (i.e., approximately 10°). While angling the disc ramps28and the plate ramps38at the same angle is preferred as illustrated in the Figures, the ramps28,38could be angled at slightly different angles (e.g., one at 9° and the other at 11°) or even more disparate angles (e.g., one at 5° and one at 20°). In all cases, however, the ramps28and38will be angled at shallow angles (i.e., between 5° and 20°).

Again, as with the disc plateaus26, the plate plateaus36are spaced approximately 120° from each other around the circumference of the brake plate14. A series of plate recesses42are defined along the circumference of the brake plate14between the plate plateaus36and cover approximately one-half of the plate circumference, with the plate plateaus36covering approximately the other half. A series of counter-sunk holes44through the brake plate14are used to mount the brake plate14to the base member18(seeFIG. 1) so that the brake plate14is relatively stationary with respect to the base member18. The insert17(and, thus, the shaft16attached to it) and brake disc12rotate relative to the brake plate14and the housing18.

The connecting hub22of the brake disc12and the shaft16extend through a central aperture46of the brake plate14, thereby positioning the disc face24adjacent the plate face34. In this way, the top surfaces30of the disc plateaus26mate with the plate recesses42of the disc plate14and the top surfaces40of the plate plateaus36mate with the disc recesses32of the brake disc12. Also, the disc ramps28are in engagement with the plate ramps38. As the brake disc12rotates with the shaft16, the disc plateaus26ride up the plate ramps38and onto the plate plateaus36. The top surfaces30of the disc plateaus36then slide over the top surfaces40of the plate plateaus36. The brake disc12must overcome the biasing force provided by the springs20to cause the disc plateaus26to ride up the plate ramps38and over the top surfaces40of the plate plateaus36. The frictional force provided by the sliding engagement of the top surfaces30of the disc plateaus26over the top surfaces40of the plate plateaus36, and the force provided by the positive mechanical engagement provided between the disc ramps28and the plate ramps38when the disc plateaus26are mated with the plate recesses32, provide the braking force to brake the shaft16and, thus, for example, a vehicle to which the shaft16is coupled. Once the braking process is complete, the positive mechanical engagement of the disc ramps28and the plate ramps38, “locks” the shaft16in position, preventing further rotation of it.

As an example, the braking system10of the present invention could be used to brake the hinge shaft of a large cargo door on a transport aircraft. The system10would be powered, thereby releasing the brake plate14from the brake disc12to allow the shaft16to rotate while the door is being closed. As the door approaches its closed position, power would be removed from the system10and the springs20would force the brake plate14into engagement with the brake disc12, as shown inFIG. 1. The interaction of the plate plateaus36against the disc plateaus26causes the shaft16to dynamically brake. That is, the shaft16may continue to rotate for a number of turns after the brake plate14has engaged the brake disc12, but the engagement of the plateaus26,36will cause the shaft16to begin slowing down and eventually stop. Once the shaft16has stopped rotating, the positive engagement of the plate plateaus36with the disc plateaus26provides a secure brake/lock preventing the shaft16from rotation even in the high vibratory environment of an aircraft. To help counter vibratory forces acting on the system10, a number of plugs58made of an elastic material such as rubber, Viton, etc. are placed through the system10to help dampen vibration in the system10. Even if the force of the springs20varies somewhat under the forces created by the vibratory environment, the positive engagement of the plateaus26,36will not allow the brake disc12to rotate relative to the brake plate14, which in turn means the cargo door will not move from its closed position. Thus, the at-rest state of the system10, with power removed, provides a secure, closed state for the cargo door.