Abstract:
A brake position sensor unit includes a unitary brake shaft that transmits braking torque to a article to be slowed, connects directly to a brake unit, connects to a resolver and has a plurality of planetary gears rotating thereabout to activate a sensor when the brake unit is set.

Description:
BACKGROUND OF THE INVENTION 
     The application claims priority to U.S. Provisional Application No. 61/106,208 which was filed on Oct. 17, 2008. 
    
    
     Prior art brake sensors are typically used with an electromagnetic brake that has a failsafe feature that activate springs to apply the brake if an electromagnetic field that opposes the force of the springs fails. To deactivate the brake, the electromagnetic field pulls the brake parts apart. A resolver is typically used to communicate with a controller to inform the aircraft of the brakes position. A brake verification mechanism may be used with the brake sensor to determine whether a brake is in use. 
     SUMMARY OF THE INVENTION 
     According to the invention, a brake position sensor unit includes a brake shaft that transmits braking torque to an article to be slowed, connects directly to a brake unit, connects to a resolver and has a plurality of planetary gears rotating thereabout to activate a brake verification mechanism (“BVM”) if the brake unit is set. 
     According to an aspect of the invention, the BVM is used to verify the brake is set in a take-off environment. 
     These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a prior art sectional view of a brake for an aircraft. 
         FIG. 2  shows a brake unit including a sectional view of the brake position sensor of the invention. 
         FIG. 3  is a close-up of a brake assembly of  FIG. 2 . 
         FIG. 4  is a close-up of the planetary gear head and brake verification mechanism of  FIG. 2 . 
         FIG. 5  is a schematic view of the brake unit shown in  FIG. 2  in a non-limiting embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to a prior brake sensor  FIG. 1  is shown. A shaft  10  is attached to an item to be braked such as an aircraft slat, flap (not shown) or wheel  230  (see  FIG. 5 ). A plurality of planetary gears  20  attached to shaft  10  rotates a sun gear  15  that is attached to a separate brake shaft  25 . The brake shaft in turn rotates a brake plate  30  disposed between a clapper plate  40  and a thrust washer  35 . The brake shaft also rotates a resolver  45  through a series of gears  50 . The resolver communicates the position of the brake shaft  25  to an electronic controller (not shown) and, in view of the connections noted hereinabove, the item to be positioned such as a wheel etc. (See  FIG. 5 ). 
     If voltage applied to the windings  55  is removed, a plurality of springs  60  force the clapper plate  40  against the brake plate  30  (which in turn engages the thrust washer  35 ) that is directly attached to the brake shaft  25  to stop the rotation of the brake shaft. 
     With the brake shaft  25  stopped and the brake engaged, if torque is applied to shaft  10 , the planetary gears  20  continue to rotate around the sun gear  15  until a ball ramp  75  drives a translating ball ramp  80  against a housing shoulder  85  and activates a switch  90 . The planetary gears multiply the braking torque on the shaft  10  about four fold upon freeing the springs  60 . At this point, the controller (not shown) is alerted, via a switch  90  that the brake is activated and the torque applied to shaft  10  is removed. 
     Referring to  FIG. 2 , the brake sensor unit  100  of the invention includes a resolver  105 , a gear section  110 , a brake portion  115 , planetary gears  120  and a brake verification mechanism (e.g., “BVM”)  125 . The resolver portion, gear section, brake section, planetary gears and BVM are disposed within housing  130 . A shaft  145  attaching to the gear section  110 , the brake portion (as will be discussed herein), and the planetary gears  120  extends outwardly from the housing  130  and attaches to an item to be braked such as an aircraft flap (not shown) or wheel  230 . 
     The gear section  110  and resolver  105  used in the present invention are known in the art and may be acquired from BVR Technologies. 
     Referring now to  FIGS. 2 and 3 , the brake portion  115  is described. The brake portion includes an electromagnetic coil  140 , which is disposed around shaft  145 , a translating pressure (clapper) plate  150  that is also maintained around the shaft, a stationary pressure plate  155 , and a rotating brake plate  160 . Springs  165  are disposed within the electromagnetic coil as is known in the art. The rotating brake plate  160  has brake material  170  disposed thereon. The brake plate rotates with sun gear  175  that is disposed about the shaft  135 . If the brake is activated, the electromagnetic coil is deactivated and springs  165  urge the translating pressure plate  150  into contact with the brake plate  160  which in turn engages the stationary pressure plate  155 . The brake material  170  disposed the brake plate  160  stops the brake shaft from rotating. As the brake shaft slows, planetary gears  180  rotate relative to the brake shaft also around sun gear  175 . 
     Referring now to  FIG. 4 , the planetary gears  180 , which rotate on planetary pins  182 , rotate a ball ramp  185  thereby causing a ball(s)  190  to move relative to the ball ramp and force a translating ball ramp  195  to move axially away from the ball ramp  185  until it engages a corner of the housing  200  at which point the shaft ceases to move. While the translating ball ramp moves it also engages a switch a microswitch  205  which forms the primary piece of the BVM  125 . 
     Spring  210  acts to reset the translating ball ramp to a normal operating position if torque is removed from shaft  145 . 
     The microswitch  205  has a nipple  215  that has a travel length that is ten times longer than the length of travel of the microswitch of the prior art so that there is increased reliability given the forces encountered within the brake. 
     By disconnecting the shaft  145  from the planetary gears that drive the brake shaft  25  (see  FIG. 1 ), and allowing the brake shaft to attach directly to the gear section  110  and therefore the resolver  105 , the resolver now rotates more than four times slower than the resolver of the prior art thereby increasing the reliability of the resolver. The gear section  110  is such that the resolver does not rotate more than one revolution for the length of travel of a slat, flap or a wheel while being braked. 
     In operation of the braking system is activated and an object to be braked, such as a wheel  230  is held from rotation by the brake portion  115 . The nipple  215  is being pressed by the translating ball ramp  195  and the controller then knows that the brake portion  115  is engaged. An aircraft  220  may then build thrust in its engines  225  to test the engines or prepare for take-off. If take-off is desired, the electromagnetic coil  140  pulls the translating pressure plate  150  away the brake plate  160  and the shaft  145  is released. As the brake shaft rotates, the springs urge the translating ball ramp  195  towards the ball ramp  185  away from the nipple  215  of the microswitch  205 . If this does not occur, the controller knows the brake has not released and appropriate action is taken to avoid damage to the brake sensor unit  100 . 
     Although a preferred embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.