Electrically actuated aircraft brakes

A reciprocating drive for operative axial communication with a brake disk stack through a pressure plate to compress the disk stack for braking of a rotatable wheel comprises: a relatively stationary annular housing; an annular ram member mounted coaxially within the housing and adapted for axial movement and contacting engagement with the pressure plate to effect compression of the brake disk stack; a relatively rotatable annular ring gear member mounted coaxially between the housing and the ram member; a plurality of rollers operative between the rotatable ring gear and ram members to effect an axial movement of the ram member when interacting with the rotatable ring gear member; and at least two high torque motors mounted within the housing and having pinion drives for operative engagement with the ring gear member to rotate the member in response to an electrical signal. The rollers may comprise a planetary drive or a recirculating roller drive with suitably configured ring gear and ram member engagement surfaces.

BACKGROUND OF THE INVENTION 
The invention described and claimed herein relates to aircraft brake 
assemblies wherein actuation of the brake is achieved by electrical 
control as opposed to actuation by hydraulic control. Hydraulically 
actuated aircraft braking systems are, of course, well known and 
understood in the prior art. 
More particularly, the invention provides a brake assembly wherein a 
plurality of electric torque motors effect wheel braking through a 
reciprocating control means which operates to compress a multi-disk stack 
of frictional braking elements. In the applicant's prior applications and 
patents referenced above, the reciprocating control means is in various 
forms of a ball-screw drive mechanism. Electric torque motors, responding 
to an electrical signal from the pilot cockpit control, effect rotation of 
a ring gear member which interacts through a plurality of balls to drive 
an axially and linear moving ram member into contacting engagement with a 
brake pressure plate associated with a brake disk stack for braking 
action. 
The embodiments described in this application are directed to a 
reciprocating control means in the form of roller screw drive mechanisms 
which also effect compression of the brake disk stack for braking action. 
The embodiments described and claimed herein are directed to the 
reciprocating control means only and do not elaborate upon the means by 
which the pilot or user may apply the electrical control signals to the 
torque motors which drive the reciprocating control means. Any type of 
electric brake controller which regulates the direction of current flow to 
the torque motors to achieve either brake application or brake release may 
be applied to this invention. 
SUMMARY OF THE INVENTION 
A reciprocating drive for operative axial communication with a brake disk 
stack through a pressure plate to compress the brake disk stack for 
braking of a rotatable wheel comprises: a relatively stationary annular 
housing, an annular ram member mounted coaxially within the housing and 
adapted for axial movement and contacting engagement with the pressure 
plate to effect compression of the brake disk stack, a relatively 
rotatable annular shaped ring gear member mounted coaxially between the 
housing and the ram member, a plurality of rollers operative between the 
rotatable ring gear and ram members to effect an axial movement of the ram 
member when interacting with the rotatable ring gear member, and at least 
two high torque motors mounted within the housing and having drive means 
for operative engagement with the ring gear member to effect rotation of 
the member in response to an electrical signal. The rollers may comprise a 
planetary type drive or alternatively a recirculating roller type drive 
with suitably configured ring gear and ram members for each type of drive.

DETAILED DESCRIPTION OF THE INVENTION 
Referring to FIG. 1 of the drawings, a wheel and brake assembly is 
generally indicated by reference numeral 10, the conventional elements 
thereof being shown by dot-dashed ghost lines and a specific configuration 
for a reciprocating control means according to this invention being 
indicated generally by reference numeral 100 and illustrated in solid 
lines. 
The conventional elements of a wheel and brake assembly 10 include a torque 
tube 12 fixedly secured to a brake housing 14 by a plurality of bolts 16 
and a wheel rim 18 rotatably mounted with respect to a wheel axle 20 and 
adapted for mounting of a tire (not shown). The axis of rotation of the 
rotating elements of the wheel and brake assembly is indicated by line 
A.sub.x. The wheel rim 18 includes a plurality of drive keys 18a located 
about an inner peripheral surface which engage a plurality of rotatable 
friction disks 24, the disks 24 being alternate ones of a brake disk stack 
generally indicated by reference numeral 22. The friction disks 24 are, of 
course, rotatable with the wheel 18 while other alternate ones of the 
brake disk stack 22 are relatively stationary disks 26 which are keyed 
about an inner peripheral surface 26a to the torque tube 12. The disks 
24,26 are therefore functional to provide braking of the wheel 18 when 
compressed in the axial direction by a forceful engagement imparted by a 
brake pressure plate 28 positioned at the inboard end of the brake disk 
stack 22. 
The pressure plate 28 is also positioned for operative engagement with the 
reciprocating control means 100, which control means is part and parcel of 
a brake actuator which functionally effects compression of the brake disk 
stack for braking of the wheel 18. The reciprocating control means 100 
generally comprises at least one torque motor 30 mounted in a relatively 
stationary housing member 40 and operatively positioned with respect to a 
rotatable ring gear member 50 to drive said member 50 into rotation about 
the A.sub.x axis by way of a pinion gear 32 mounted at the outboard extent 
of its drive shaft 34. The rotatable ring gear member 50 drives a movable 
ram member 70 into and out of axial engagement with the brake pressure 
plate 28 through a plurality of roller means 60 operatively positioned and 
mounted between the ring gear member 50 and the ram member 70. The roller 
means 60, according to the first embodiment of this invention, comprises a 
plurality of planetary type rollers having annular ridges and grooves 
which engage matching ridges and grooves in a peripheral bore surface of 
the rotatable ring gear member 50 while also engaging helical ridges and 
grooves in the outwardly facing surface of the ram member 70. 
More particularly and referring now to FIG. 2 of the drawings, a torque 
motor 30 is mounted in a relatively stationary housing member 40 by being 
received within a cavity 42 and fixedly secured thereto by a plurality of 
fasteners which may be any suitable screw or bolt 44. The fasteners 44 are 
carried within bores 46 in the housing 40 which also has a bore 48 for 
receiving the motor drive shaft 32 therethrough. A pinion gear 34 is 
attached at the outer extent of the drive shaft 32. While FIG. 2 merely 
shows a single motor 30, the housing member 40 is actually an 
annular-shaped member which carries a plurality of such motors. FIG. 4 
clearly illustrates a configuration of a particular one such housing 
wherein ten motor mounting positions 42 are indicated. The actual number 
of motors 30 to be mounted in a housing 40 will, of course, depend upon 
the particular brake application and the requirements imposed on the brake 
assembly. For example, a housing 40 of the type indicated may be 
configured to mount as many as 15 or as few as two torque motors 30 and 
these will be positioned in a balanced arrangement within the housing 40 
about the A.sub.x axis. Finally, the housing member 40 is characterized by 
a ball race 40a machined or otherwise formed within an inside surface of 
its bore 40b. The ball race 40a is one-half of a thrust bearing which 
carries a plurality of ball bearings 80 and these are mounted within a 
passageway formed by the race 40a and an opposite race configured in the 
rotatable ring gear member 50 to be specifically described hereinafter. 
The rotatable ring gear member 50 comprises, primarily for ease in 
manufacture, two annular-shaped pieces 50a and 50b which are positioned 
inboardly and outboardly respectively about the A.sub.x axis. The inboard 
portion 50a is functionally a ring gear having gear teeth 52 about an 
inner bore surface, which teeth are positioned to engage matching teeth of 
the pinion gear 32 in a conventional manner. The inboard portion 50a is 
secured to the outboard portion 50b by fasteners 82 and both portions 
rotate as a single integral unit by the action of the pinion 34 on the 
ring gear teeth 52. The outboard portion 50b is an L-shape in 
cross-section having a vertical leg 54 that attaches to the inboard piece 
50a via fasteners 82 and an axial or horizontal leg 56 which carries the 
other half of the thrust bearing race indicated at 50c. A bore surface in 
the horizontal leg 56 is characterized by a plurality of annular ridges 
and grooves 58 which function to engage the planetary rollers 60 in a 
manner to be described hereinafter. 
The axially movable ram member 70 is mounted in the brake housing 14 and is 
restrained from rotational motion about the A.sub.x axis by reason of ball 
slots 72 which interact with anti-rotational balls 84 mounted in 
corresponding slots 86 in the brake housing structure 14. The relationship 
which exists between the slots 72,86 and the balls 84 is clearly 
illustrated in FIG. 4 of the drawings at three balanced locations within 
the bore of the ram member 70. Referring again to FIG. 2, the ram member 
70 is characterized by a plurality of ridges and grooves 74 in its 
outwardly facing surface and these have a particular helical pitch which 
when interacting with the rollers 60 effects an axial movement to the ram 
member. 
Now therefore, and as hereinbefore stated, the rollers 60 are planetary 
type rollers and these are configured with a grooved drive surface 62. The 
surface 62 comprises ridges and grooves which are annular rather than 
helical in configuration and may comprise a machined surface which is 
complimentary with the ridges and grooves 58 in the bore of the rotatable 
ring gear member 50. Alternatively, the roller ridges and grooves may be 
configured from a plurality of stacked washers, alternating ones of the 
stack having the major diameter of the roller which establishes the ridge 
height while the other alternating ones have a minor diameter which 
establishes the groove depth. In either of these above-mentioned 
configurations, each roller 60 is mounted between a pair of keeper plates 
66 which are affixed to an inboard and to an outboard facing surface of 
the rotatable ring gear member 50. 
Referring now to FIG. 3 of the drawings, each roller 60 is mounted between 
the keeper plates 66 such that its axis indicated at A.sub.r is offset 
with respect to the A.sub.x axis about which both the ring gear member 50 
and the ram member 70 are axially mounted. Accordingly, a line drawn 
parallel to the roller ridges and grooves 62 and which is perpendicular to 
the roller axis A.sub.r defines an angle .alpha. with respect to both the 
rotatable ring gear member ridges and grooves 58 as illustrated in the 
left hand portion of FIG. 3 and to the ram member ridges and grooves 74 as 
illustrated in the right hand portion of the figure. Preferably, the angle 
.alpha. is one-half the pitch angle of the helically turned ridges and 
grooves of the ram member 70 which are also perpendicular to an axis 
indicated at A.sub.h which is the axis of the helix with respect to the 
A.sub.x axis of the ram member 70. It will be appreciated therefore that a 
rotation of the ring gear member 50 effects rotation of the rollers 60 and 
these in turn advance the ram member 70 in the axial direction dependent 
upon the direction of rotation of the ring gear member. Furthermore, 
because the ridges and grooves 58 in the bore of the ring gear member 50 
are annular and the ridges and grooves 62 about the surface of each roller 
60 are also annular, there is no axial motion imparted relatively between 
these two members. However, because the ridges and grooves 74 in the 
surface of the ram member 70 are helical turns, the interaction of these 
with the rollers 60 effects a relative axial motion between these two 
members. The rollers 60 are, or course, stationary in the axial direction 
by reason of their mounting within the bore of the ring gear member 50 and 
therefore the axial motion is imparted to the ram member 70. It will be 
further appreciated from the foregoing that the rollers 60 travel in a 
planetary path and do not move axially when the rotatable member 50 is 
rotated by the pinion 34 and consequently they do not have to be 
recirculated. 
FIG. 5 of the drawings illustrates a second embodiment of the invention 
which is generally indicated by reference numeral 101. According to this 
embodiment, a plurality of rollers 90 are mounted between the ring gear 
member 50 and the ram member 70, which rollers 90 are characterized by a 
ridge and groove outwardly facing surface 92 having a continuous helical 
turn of the same pitch as the ridges and grooves 74 of the ram member 70. 
In addition, the ring gear member 50 is characterized by a bore surface 
comprised of matching ridges and grooves generally indicated at 59 and 
these are helically pitched with respect to the A.sub.x axis. In this 
configuration, a rotation of the ring gear member 50 as effected by the 
pinion gear 34 will move each roller 90 in the axial direction within the 
confines of the ring gear bore 59. The rotation and axial movement of the 
rollers 90 effects an axial movement of the ram member 70 into and out of 
contacting engagement with the brake pressure plate indicated at 28 in a 
ghost-line illustration. It will be appreciated that, because the roller 
ridges and grooves 92 are helical turns and the rollers move axially, they 
must be recirculated back to a starting position when the ring gear member 
rotates beyond a particular portion of the helical turn extent of its 
ridges and grooves. In this respect, each roller 90 has an axial length 
which is a particular portion of the axial length of the bore 59 and the 
actual length is dependent upon the helical pitch of its ridges and 
grooves and that of the interacting members. In any event, and to limit 
the axial excursion of each roller 90, an end ring 53 is provided at the 
inboard end of the ring gear member 50 and it is affixed via fasteners 53a 
while an end ring 55 is provided at the outboard end and it is affixed via 
fasteners 55a. Recirculation of each roller 90 may be accomplished, for 
example, by a cam and slot configuration wherein a slot (indicated at 94) 
is machined axially within the bore of the ring gear member 50 and in-line 
cams 96 are provided which lift the roller radially out of contacting 
engagement with ram member 70 and into the slot 94. Upon continued 
rotation of the ring gear member 50 in the same direction, a roller 90 is 
moved back to its starting position within the bore of the ring gear 
member. It is anticipated that a roller 90 need only be moved back a 
single ridge and groove distance of the ram member ridges and grooves 74 
at any point of recirculation. A recirculating roller screw mechanism 
which operates on the principle just described is produced by SKF Group of 
La Technique Integrale of Chambery, France and sold under the Trademark 
"TRANSROL".