Abstract:
An object detection system is operable to alert and/or automatically react to a lawn mower, or equivalent mower equipment, contacting an object when the lawn mower is operating in reverse gear. The object detection system comprises a sensor strip, a connection lead wire and an electrical circuit. The sensor strip generates and electrical contact signal traveling through the lead wire in response to the lawn mower contacting an object. The electrical contact signal causes the electrical circuit to enable a warning system and selectively activate a brake system and disable the power take off (PTO) switch to stop rotation of the mower blade.

Description:
BACKGROUND  
       [0001]     The present invention relates to an object detection system for a lawn mower.  
       SUMMARY  
       [0002]     In one embodiment, the invention provides a lawn mower comprising a chassis; a plurality of wheels mounted for rotation with respect to the chassis and supporting the chassis; a mower deck supported by the chassis; a cutting blade beneath the mower deck and rotatable to cut vegetation under the mower deck; an engine supported by the chassis and selectively engaging the wheels to cause forward movement and reverse movement of the lawn mower, and selectively engaging the cutting blade to cause rotation of the blade; means for generating an electrical contact signal in response to a rear portion of the lawn mower contacting an object; and an electrical circuit causing the mower blade to cease rotation in response to receiving the electrical contact signal.  
         [0003]     In another embodiment the invention provides a method for operating a lawn mower comprising of a chassis, a plurality of wheels, a mower deck, a cutting blade, and an engine. The method comprises (a) applying a pressure sensor to a rear portion of the lawn mower; (b) generating an electrical signal in response to the pressure sensor detecting impact with an object; (c) transmitting the electrical contact signal to an electrical circuit; and (d) stopping rotation of the mower blade in response to the electrical circuit receiving the electrical contact signal.  
         [0004]     The electrical circuit may disengage the mower blade from the engine in response to receiving the electrical contact signal, or it may shut down the engine in response to receiving the electrical contact signal. The lawn mower may also include a bumper in the rear portion of the lawn mower, and the means for generating the electrical contact signal may be mounted on the bumper. The lawn mower may also include a braking system for selectively resisting rotation of the cutting blade, and the electrical circuit may activate the braking system in response to the electrical circuit receiving the electrical contact signal.  
         [0005]     The means for generating the electrical contact signal may take the form of, for example, a resilient strip with pressure sensors. The electrical circuit may include a relay that permits the engine to engage the cutting blade in the absence of the electrical contact signal, but that disengages the cutting blade from the engine in response to receiving the electrical contact signal. The electrical circuit may also include a central processing unit (CPU) to filter out transient electrical signals. The means for generating the electrical contact signal may also include a wireless transmitter and receiver.  
         [0006]     Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]     FIG. I is a perspective view of a lawn mower embodying the present invention.  
         [0008]      FIG. 2  is an exploded view of the rear portion of the lawn mower.  
         [0009]      FIG. 3  is a schematic illustration of the electrical circuit of the lawn mower in a blade-disengaged condition.  
         [0010]      FIG. 4  is a schematic illustration of the electrical circuit of the lawn mower in a blade-engaged condition.  
         [0011]      FIG. 5  is a schematic illustration of the electrical circuit of the lawn mower in a blade-disabled condition. 
     
    
     DETAILED DESCRIPTION  
       [0012]     Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings.  
         [0013]      FIG. 1  illustrates a lawn mower  10  comprising a chassis  15 , a mower deck  20 , one or more cutting blades  25  beneath the mower deck  20 , a set of four wheels  30  supporting the chassis  15 , and an engine  35 . A power take off (PTO) clutch  40  (illustrated schematically in  FIGS. 3-5 ) selectively engages the cutting blade  25  to the output shaft  45  of the engine  35  to cause the cutting blade  25  to rotate under the influence of the engine  35 . A brake  43  (illustrated schematically in  FIGS. 3-5 ) selectively stops rotation of the blades  25  so they do not continue to rotate after the engine is disengaged from the blades. Although the illustrated lawn mower is of the zero-turn, transteer variety, the invention may also be embodied in more traditional lawn tractors or any other type of riding lawn mower.  
         [0014]      FIG. 2  illustrates a rear portion  50  of the lawn mower  10 , which includes a pressure sensor strip  55  mounted within a bracket  60  that is fastened to a rear portion of the chassis  15  using screws  75  or other appropriate fasteners or mounting means. Alternatively, the lawn mower  10  can include a bumper mounted to the rear portion of the chassis  15  and the strip  55  can be affixed to the bumper. In the illustrated embodiment, the strip  55  is a product commercially available from Recon Company of Batavia, Ill., and sold as part number T-120 under registered trademark SENSI-SWITCH. More specifically, the strip  55  comprises a high yield stainless steel electrode acting as sensing element. The electrode is molded in urethane and electrically communicates with a lead wire  70 . In operation, the electrode generates an electrical contact signal in response to pressure being applied to the strip  55 , and the lead wire  70  conducts the electrical contact signal.  
         [0015]     The lead wire  70  is connected to the lawn mower&#39;s electrical system  75 . The electrical system may include, for example, a battery, a lighting system, a start up system, control panel with switches and lights, steering control system, and other elements. In some embodiments, the electrical system may include controllers and circuits such as that disclosed in commonly-assigned U.S. Patent Application Publication No.  2005-0053447  A1, the entire contents of which are incorporated herein by reference.  
         [0016]      FIGS. 3-5  illustrate an electrical circuit  80  that is also part of the lawn mower&#39;s electrical system. The electrical circuit  80  includes a PTO switch  85 , which a user can actuate to engage the PTO clutch  40  and cause rotation of the cutting blade  25  under the influence of the engine  35 . The circuit  80  also includes a warning system  90 , which alerts the user when the rear portion  50  of the lawn mower comes into contact with an object. The circuit  80  also includes a bumper switch  95 , which closes in response to receiving the electrical contact signal from the strip  55 . Last, the circuit  80  includes a relay system  100 , which is connected to the PTO switch  85 , the PTO clutch  40 , the bumper switch  95  and the warning system  90 .  
         [0017]      FIG. 3  illustrates the electrical circuit  80  when the cutting blade  25  is not engaged to the engine  35 . During normal operation of the lawn mower  10 , the engine  35  of the lawn mower  10  is operating but the engine  35  does not engage the cutting blade  25  until the PTO switch  85  is closed by the user.  
         [0018]      FIG. 4  illustrates the PTO switch  85  in a closed position, therefore the PTO clutch  40  becomes part of a closed electrical circuit and causes the engine  35  to engage the cutting blade  25 . During such normal operation of the lawn mower  10 , the bumper switch  95  remains open, keeping the warning system  90  off.  
         [0019]      FIG. 5  illustrates the operation of the electrical circuit  80  when the strip  55  generates the electrical contact signal. The bumper switch  95  closes in response to receiving the electrical contact signal. This causes the relay system  100  to switch from connecting the PTO switch  85  to the PTO clutch  40  to connecting the PTO switch  85  to the warning system  90 . As a result, the cutting blade  25  disengages from the engine  35  while the warning system  90  starts operation. The circuit  80  can perform other acts in response to receiving the electrical contact signal, such as shut down the engine  35 , automatically shifting the transmission into a neutral or forward gear, and engaging the blade brake  43 .  
         [0020]     With respect to the blade, the relay system  100  may connect the PTO switch  85  to the brake  43  in response to the bumper switch  95  closing. In consequence, the brake stops the rotational motion of the cutting blade  25  as the cutting blade  25  disengages from the engine  35 .  
         [0021]     In alternative embodiments, the electrical circuit  80  may include a central processing unit (CPU) that controls operation of the mower blade  25  in response to actuation of the PTO switch  85  and generation of the electrical contact signal at the pressure sensor strip  55 . In some embodiments, the electrical circuit  80  can include wireless means for transferring the electrical contact signal, including wireless receivers and transmitters. Also, the CPU may be programmed to filter out transient contacts. Transient contacts may include, for example, electrical contact signals produced by the strip  55  due to contacting objects such as flying rocks and flying chips, other flying debris, or high grass during normal operation of the lawn mower.  
         [0022]     Thus, the invention provides, among other things, an object detection system for a lawn mower. Various features and advantages of the invention are set forth in the following claims.