Fluid-pressure and analogous brake systems – Speed-controlled – Automatic braking including speed governor or hydraulic...
Reexamination Certificate
1999-08-13
2001-07-10
Schwartz, Christopher P. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Automatic braking including speed governor or hydraulic...
C303S004000, C244S111000
Reexamination Certificate
active
06257681
ABSTRACT:
BACKGROUND
The present invention relates to a braking system suitable for an aircraft and a method for the control of a braking system comprising a plurality of brake assemblies at least one of which is operable independently of the other or another of the brake assemblies. The invention relates also to a brake control system for the control of a plurality of carbon brakes and to a braking system such as an aircraft braking system comprising a plurality of carbon brakes and to a braking system such as an aircraft braking system comprising a plurality of carbon brakes rakes operatively associated with the brake control system.
The term carbon brake is used to mean a brake assembly having friction discs of a carbon-carbon composite material comprising a carbon fiber reinforcing material within a carbon matrix.
The ability to stop an aircraft both quickly and economically is of great importance and enormous amounts of kinetic energy have to be dissipated in order to bring a moving aircraft to rest, particularly in RTO (refused or rejected take-off) situation. The aircraft velocity may be decreased and the kinetic energy thereby dissipated by drag forces, by application of the engine thrust reversers and by application of the aircraft wheel brakes. The drag forces can be increased by deploying of airbrakes or speed brakes on the aircraft wings.
However, very high energy brake applications in an RTO situation are fortunately rare events and therefore play little, if any, part in determining overall brake operating economics.
It is now recognized that the rate of wear of carbon brake discs is not proportional to the energy dissipated during the time the brakes are applied, brake wear being disproportionately high when energy input to the brake is low. Consequently it is beneficial to apply only a restricted number of the available brakes when the required braking action is relatively low.
The concept of applying only limited numbers of brakes during taxiing operations but all the available brakes in a landing run has already been disclosed in GB 2216209B and U.S. Pat. No. 4,097,610. The concept has been described variously as brake disabling, selective braking or as taxi-brake select.
That concept has been developed by the teaching of GB 2289734 which describes a cascade operation. In the cascade operation the number of brake assemblies actuated is dependent on the pilot's pedal pressure demand and can increase, or decrease, as the pilot's demand increases or decreases.
In some circumstances a condition can arise in which it would be undesirable to employ or continue with selective braking, either simple selective braking as in GB 2216209 or cascade braking as in GB 2289734. Examples of conditions when simple selective or cascade braking might be undesirable include occasions when a skid condition is detected and when a hydraulic fuse has blown.
SUMMARY OF THE INVENTION
This invention has as an object the provision of means and a method whereby selective braking is inhibited when there arises a condition, especially a randomly occurring condition, that requires or renders prudent the operation of all brake assemblies.
According to one aspect of the invention, there is provided a selective braking system comprising a plurality of brake assemblies, each comprising brake actuation means: braking demand signal supply means for supplying a signal indicative of a demanded level of braking to be provided by the system; drive signal supply means connected to each brake actuation means and the braking demand signal supply means and operable for supplying drive signals to the brake actuation means to operate the respective braking assemblies; control means coupled to the drive signal supply means and operable for selectively operating said brake assemblies; and monitoring means connected to the drive signal supply means and said control means and operable for monitoring the drive signal received by each brake actuation means with reference to the said braking demand signal and, at times, for causing the control means to become operable for the brake assemblies to be operated concurrently.
Each brake actuation means may be hydraulically operable and the drive signal supply means may comprise hydraulic pressure supply means connected to each actuation means.
According to a second aspect of the invention there is provided a selective braking system comprising a plurality of hydraulically operable brake assemblies, each brake assembly comprising brake actuation means: braking demand signal supply means for supplying a signal indicative of a demanded level of braking to be provided by the system; hydraulic pressure supply means connected to the actuation means and the braking demand signal supply means and operable for supplying hydraulic pressure to the brake actuation means to operate the braking assembly; control means couples to the hydraulic pressure supply means and operable for selectively operating said brake assemblies; monitoring means connected to the hydraulic pressure supply means and said control means and operable for monitoring the hydraulic pressure received by the brake actuation means with reference to the braking demand signal and, at times, for causing the control means to become operable for the brake assemblies to be operated concurrently.
In accordance with another of its aspects the present invention provides a braking system comprising a plurality of hydraulically operable brake assemblies at least one of which is operable independently of the other or another brake assembly of the plurality, control means for monitoring the hydraulic pressure at at least some of the brake assemblies and comparing the pressure with a brake control demand signal, and override means to cause operation of all or substantially all of the brake assemblies if comparison of the monitored hydraulic pressure with the brake control demand signal indicates a requirement for all or substantially all of the brake assemblies to be operated simultaneously.
The invention provides also a brake control system for use in the braking system and method aspects of the invention.
The brake control demand signal may, for example, be a hydraulic signal derived from a pilot's brake pedal pressure, or an electronic signal from a brake control device especially in the case of a fly-by-wire type aircraft.
The control means may, for example monitor hydraulic pressure at a position between a hydraulic anti-skid control valve and a brake actuation piston. The monitor position may be between a hydraulic fuse and a brake actuation piston.
In accordance with another of its aspects the present invention provides a method for the control of a braking system comprising a plurality of hydraulically operable brake assemblies at least one of which is operable independently of the other or another of the brake assemblies wherein the hydraulic pressure at at least some of the brake assemblies is monitored and compared with a brake control dement signal, and a system condition which inhibits at least one of the brake assemblies from operating during a braking condition is over-ridden at least in part whereby all or substantially all brake assemblies are brought into operation when comparison of a monitored brake assembly hydraulic pressure with a brake control dement signal indicates a requirement for all or substantially all of the brake assemblies to be operated simultaneously.
In consequence of the invention it is therefore possible to provide that fewer brakes are inhibited than otherwise would be the case, or that all brakes are in operation during the occurrence of anti-skid activity or failure of a hydraulic fuse or, more generally, a pressure drop resulting from a failure of a component or hydraulic line at a position between a anti-skid valve and a brake assembly.
REFERENCES:
patent: 4971179 (1990-11-01), Gebhardt et al.
patent: 4986610 (1991-01-01), Beck et al.
patent: 5403072 (1995-04-01), Kilian et al.
patent: 5417477 (1995-05-01), Lasbleis
patent: 5505531 (1996-04-01), Griffith
patent: 5845975 (1998-1
Bartz C. T.
Dunlop Aerospace Limited
Nixon & Vanderhye P.C.
Schwartz Christopher P.
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