Abstract:
A vehicle connectable to an auxiliary power unit capable of energizing a pair of fail-safe brakes that arrest rotation of a pair of electric transaxles mounted to the vehicle. Each brake has an external connector and requires electrical power to assume a non-braked state that permits free rotation of an electric motor engaged to the brake and incorporated in each of the electric transaxles. The auxiliary power unit having first and second circuits and first and second connectors compatible with the external connectors of one of the brakes.

Description:
CROSS REFERENCE 
     This application claims the benefit of U.S. Provisional Patent Application No. 61/357,341 filed on Jun. 22, 2010, which is incorporated herein in its entirety. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to component assemblies for electric drive systems for self-propelled vehicles or machines, and is particularly useful for brake release mechanisms for electric drives used in self-propelled vehicles or machines such as lawn mowers, snow-throwers, and lawn or garden tractors. 
     BACKGROUND OF THE INVENTION 
     Self-propelled vehicles or other machines such as self-propelled or riding lawn mowers, snow-throwers, and lawn or garden tractors are known. Electric drive systems for such vehicles or machines typically employ an automatic fail-safe or parking brake in association with an electric drive motor which drives one or more axles. 
     It would be advantageous to be able to release the fail-safe brake to allow the vehicle to be towed or otherwise moved, e.g. for servicing the vehicle, when it is not in operation or the batteries are discharged. 
     SUMMARY OF THE INVENTION 
     This invention relates to an assembly useful in association with electric drive systems for self-propelled vehicles or machines having a fail-safe or parking brake mechanism comprising an auxiliary battery-powered brake release assembly. 
     This invention also relates to a self-propelled vehicle or machine having an electric drive system comprising a fail-safe brake in association with an auxiliary battery-powered brake release assembly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top plan view of a vehicle in the form of a riding lawn mower to which one or more principles or aspects of the present invention may be applied. 
         FIG. 2  is a top plan view of the vehicle depicted in  FIG. 1  showing application of one or more principles of the present invention. 
         FIG. 3  is a schematic diagram of a battery-powered brake release circuit useful in the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     An example of a self-propelled vehicle that can be modified in accordance with this invention is described in U.S. Patent Application Publication No. 2009/0065273, filed as Ser. No. 12/209,120 on Sep. 11, 2008, the entire disclosure of which is incorporated herein by reference. 
     Turning now to the figures, wherein like reference numerals refer to like elements,  FIG. 1  illustrates a utility vehicle in the form of mowing vehicle  100 , that can be modified to incorporate one or more principles of the present invention. Power supply (not shown) of vehicle  100  drives an electric motor  141  on each of two electric transaxles,  110   a  and  110   b , each separately driving one of two rear wheels  112   a  and  112   b , to implement zero turn vehicle functionality. A pair of pivoting front casters  125  is also provided to facilitate zero turn vehicle functionality. The transaxles drive the wheels  112   a  and  112   b  via axle shafts  113   a  and  113   b , which are coupled to transmissions  114   a  and  114   b , which are driven by electric motors  141 . A fail-safe brake  160  is joined to each of the electric motors  141 , preventing movement of the vehicle, for example, when it is powered down. In this embodiment, the electric transaxles  110   a  and  110   b  are nested in a side-by-side, parallel arrangement as shown in  FIG. 1 . A brake release assembly in accordance with the principles of the invention can be modified to be useful with a lawn tractor having only one electrically driven transaxle incorporating a single fail-safe brake as described herein. 
     Referring to  FIGS. 1 and 2 , mowing vehicle  100  may include one or more brake systems. In the embodiment shown, switches (not shown) are opened when steering/drive levers  136   a  and  136   b  are both positioned in a neutral, drive-disengaged position, allowing the engagement of fail-safe brakes  160 . Similarly, when drive levers  136   a  and  136   b  are both positioned in the neutral, drive-disengaged position, those same switches (or a separate set of switches) may also signal or initiate a blade stop function as a safety and power management feature. 
     In the mode shown in  FIG. 1 , fail-safe brake leads  143  extend from fail-safe brakes  160  to controller leads  145   a  and  145   b , providing electrical communication between the fail-safe brakes  160  and controllers  120   a  and  120   b . Drive controllers  120   a  and  120   b  may control electrical communication from a vehicle power source, such as a battery (not shown), to the fail-safe brakes  160 . Each fail-safe brake  160 , which is biased to braking engagement, is preferably of a conventional, electro-mechanical kind in which springs (not shown) press a brake plate, friction disk or the like (not shown) into braking engagement, arresting the rotation of the motor shaft (not shown) of an electric motor  141 , to which it is engaged. In a vehicle driving mode, electrical current from the vehicle power source passes through the controllers  120   a  and  120   b  to energize coils (not shown) in the fail-safe brakes  160 , thereby releasing the brake plate or friction disk from braking engagement. 
       FIG. 2  shows the connection of fail-safe brakes  160  to brake release assembly  150 . As shown in  FIG. 2 , when the connections between fail-safe brakes  160  and controllers  120   a  and  120   b  are manually broken, and battery pack case  153  and battery pack leads  151  are connected to fail-safe brake leads  143 , the closing of switch  154  releases fail-safe brakes  160 . In the mode shown in  FIG. 2 , the electrical current from battery pack case  153  energizes coils (not shown) in brakes  160  that oppose the springs and release brakes  160 . The brake release assembly  150 , which may be used periodically to release brakes  160  when the main power supply is depleted, for example, may be a hand held device or may be permanently mounted on vehicle  100 . 
       FIG. 3  shows the circuit details of brake release assembly  150 , comprising a pair of switchable circuits connecting a power source  152   a  and  152   b  in parallel with a light-emitting diode (LED)  158   a  and  158   b  and an external connector  156   a  and  156   b , respectively. External connectors  156   a  and  156   b  are joined to the pair of switchable circuits by battery pack leads  151  (as best shown in  FIG. 2 ), which may be of varying length to allow for the access requirements of different vehicles. As illustrated, both circuits are controlled by a double pole single throw (DPST) switch  154 , though other switch types or number of switches may be employed as known in the art. Switch  154  may be mounted to the exterior of battery pack case  153 . In  FIG. 3 , each power source  152   a  and  152   b  is depicted as a pair of batteries in series, specifically a set of 9V batteries. While the use of 9V batteries is shown for convenience, other batteries and voltages may be employed as determined by the demand or requirements of fail-safe brakes  160 . Power sources  152   a  and  152   b  are contained within battery pack case  153 . Each LED  158   a  and  158   b  may be mounted to the exterior of battery pack case  153  and serves as an indicator that fail-safe brakes  160  have been released. However, conventional lamps or bulbs could be used in each circuit as indicators. 
     While specific embodiments have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention.