Abstract:
A cutter assembly positioning mechanism provides an improved positioning mechanism and control for a riding lawn mower. Specifically, the mechanism optimizes the speed and accuracy of positioning the cutter assembly in the desired position and allows the operator to raise and lower the cutter assembly without sacrificing control of the mower. The lawn mower has a frame including an actuator adapted to be coupled to the frame, a cutter assembly adapted to be movable relative to the frame for adjusting a cutting height and a first flexible member interconnecting the actuator and the cutter assembly. The actuator is operable to extend and retract thereby raising and lowering the cutter assembly.

Description:
RELATED APPLICATIONS 
     This application claims the benefit of U. S. Provisional Application No. 60/139,563 filed Jun. 16, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention generally relates to a lawn cutting apparatus. More particularly, the present invention pertains to a mechanism for positioning a cutter assembly for a riding lawn mower. 
     2. Discussion 
     Operators of lawn cutting equipment often have a need to adjust the position of the cutter assembly relative to the ground over which the lawn mower is driven. The cutter assembly is typically retracted when the mower is driven from one cutting area to another to avoid hitting obstacles such as curbs and stones. 
     Many riding lawn mowers are equipped with mechanisms for positioning the cutter assembly to a desired cutting height. Most of these mechanisms consist of linkage interconnecting the cutter assembly and a lever which is directly controlled by the operator&#39;s hand or foot to engage a series of holes which correspond to specific cutting heights. Although the effort required to lift the cutter assembly is reduced by using leverage, these mechanisms require strength and coordination. 
     Other cutter assembly lift mechanisms exist that are actuated by an electric motor or a hydraulic cylinder. However, many of these devices have certain undesirable features. Firstly, the operator of the lawn cutting equipment is unable to easily position the cutter assembly at a desired height because the device lacks a positive height setting device. While some of the aforementioned mechanisms include a fine adjustment capability that is facilitated by using a slow actuation means, use of this design sacrifices productivity by making the operator wait. Secondly, many riding mowers are controlled by a steering mechanism that requires the use of both of the operator&#39;s hands. Accordingly, operation of the aforementioned lift mechanisms requires the operator to stop the mower in order to take one hand off of the steering mechanism and adjust the cutting height. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide an improved positioning mechanism and control for a riding lawn mower. 
     It is another object of the present invention to optimize the speed and accuracy of positioning the cutter assembly in the desired position. 
     It is yet another object of the present invention to allow the operator to raise and lower the cutter assembly without sacrificing control of the mower. 
     According to the present invention, a cutter assembly positioning mechanism for a riding lawn mower having a frame includes an actuator adapted to be coupled to the frame, a cutter assembly adapted to be movable relative to the frame for adjusting a cutting height and a first flexible member interconnecting the actuator and the cutter assembly. The actuator is operable to extend and retract thereby raising and lowering the cutter assembly. 
     Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from a reading of the subsequent description of the preferred embodiment and the appended claims, taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a riding lawn mower constructed in accordance with the teachings of the present invention; 
     FIG. 2 is a partial side view of the cutter assembly positioning mechanism of the present invention; 
     FIG. 2A is a magnified view of the mechanism of FIG. 2; 
     FIG. 3 is a perspective view of an embodiment of the cutter assembly positioning mechanism of the present invention; 
     FIG. 4 is a side view of the secondary and tertiary sprockets of the cutter assembly positioning mechanism of the present invention; 
     FIG. 5 is a partial perspective view of the cutter assembly positioning mechanism constructed in accordance with the teachings of the present invention; 
     FIG. 6 is a side view of the cutter assembly positioning mechanism depicting the cutting height memory mechanism in an operable position; and 
     FIG. 7 is an electrical schematic of the control system for the cutter assembly positioning mechanism of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference to the drawings, a cutter assembly positioning mechanism and control for a riding lawn mower constructed in accordance with the teachings of an embodiment to the present invention is generally identified at reference numeral  10 . The cutter assembly positioning mechanism  10  is shown operatively associated with an exemplary riding lawn mower  12 . In the preferred embodiment, the riding lawn mower  12  is a zero turning mower capable of performing zero radius turns. The riding lawn mower  12  includes a left steering control lever  14  for controlling a left drive wheel  16  and a right steering control lever  18  for controlling a right drive wheel  20 . Accordingly, proper operation of the riding lawn mower  12  requires the use of both of the hands of an operator at all times. The riding lawn mower  12  further includes a pair of front wheels  22  mounted on pivots  24  to facilitate zero radius turns. One skilled in the art will appreciate that the riding lawn mower depicted in the drawings and described in detail is merely exemplary and that the cutter assembly positioning mechanism of the present invention may be utilized in a variety of applications such as riding lawn tractors and walk-behind mowers. 
     Referring to FIGS. 1 and 2, the riding lawn mower  12  further includes a frame  26  having a seat  28 , a floor pan  30  and the pivots  24  mounted thereto. The riding lawn mower  12  also includes a cutter assembly  32  pivotally interconnected to the frame  26  via links  34 . One skilled in the art will appreciate that the frame  26 , the cutter assembly  32  and the links  34  form a four-bar linkage such that the cutter assembly  32  remains in a generally horizontal plane as it is raised and lowered. 
     As shown in FIG. 3, the cutter assembly  32  is raised and lowered by an actuator  36  interconnected to a roller chain  38 . The roller chain  38  is coupled to a first sprocket  40  which is drivingly engaged to a primary shaft  42 . Depending on the geometry of the cutter assembly  32 , a number of secondary sprockets  44  and  46  may be drivingly engaged with and positioned along the length of the primary shaft  42 . The secondary sprockets  44  and  46  are utilized to distribute the lifting effort supplied by the actuator  36  across the surface of the cutter assembly  32 . In this manner, a large cutter assembly  32  such as the one depicted in FIG. 3, may be smoothly raised and lowered without binding the links  34  during operation. However, one skilled in the art will appreciate that some cutter assemblies may require only one lift point and that the roller chain  38  may be directly interconnected to the cutter assembly  32  without the need for secondary sprockets. It should also be appreciated that the roller chain  38  is merely an exemplary device and that a variety of flexible members such as wires, cables or belts may be used without departing from the scope of the present invention. In similar fashion, it should be appreciated that other rotary power transfer devices such as gears, pulleys, cogs, bearings, cams and shafts may be implemented instead of sprockets without departing from the scope of the appended claims. 
     In the preferred embodiment, an inner secondary sprocket  44  and two outer secondary sprockets  46  drivingly interconnect with the primary shaft  42 . Each of the secondary sprockets  44  and  46  are interconnected to the cutter assembly  32  via a flexible member  48 . As earlier described, the flexible member  48  may comprise devices such as a chain, a wire, a cable or a belt. As shown in FIGS. 2 and 2A, the flexible members  48  associated with the outer secondary sprockets  46  are directly interconnected to the cutter assembly  32  via an attachment mechanism  50 . 
     The attachment mechanism  50  includes a lift pin  52  mounted to an upper surface  54  of the cutter assembly  32 , an “L” shaped bracket  56  also mounted to the upper surface  54  of the cutter assembly  32  and a deck lift stud  58  for interconnecting the flexible member  48  and the “L” bracket  56 . Specifically, the “L” bracket  56  includes a first leg  60  coupled to the cutter assembly  32  and a second leg  62  having an aperture  64  extending therethrough. The deck lift stud  58  is a generally cylindrical rod  66  having an external thread extending along a substantial portion of its length. The deck lift stud  58  includes a transverse aperture  68  extending through the rod  66  near one of its ends for receipt of the flexible member  48 . Specifically, the flexible member  48  is coupled to the deck lift stud  58  in a manner commonly known in the art such as pinning. In addition, a pair of adjustment nuts  70  cooperate with the external thread of the deck lift stud  58  and the second leg  62  of the “L” bracket  56  to provide an initial adjustment feature whereby the operator may level the cutter assembly if more than one secondary sprocket is used. 
     Referring to FIG. 3, the inner secondary sprocket  44  and its corresponding flexible member  48  act in cooperation with a tertiary sprocket  72  drivingly engaged with a secondary shaft  74  rotatably coupled to the frame  26 . It will be appreciated that the flexible member  48  drivingly engages both the inner secondary sprocket  44  and the tertiary sprocket  74  and is coupled to the cutter assembly  32  via the attachment mechanism  50  as previously described in detail. In reference to FIGS. 3 and 4, as the actuator  36  is extended, the primary shaft  42  rotates in a clockwise direction as viewed from the left side of the riding lawn mower  12 . Accordingly, the secondary sprockets  44  and  46  also rotate in a clockwise manner. Based on the routing of the flexible member  48 , the tertiary sprocket  72  rotates in a counter-clockwise fashion thereby lowering the cutter assembly  32 . Conversely, when the actuator  36  is retracted, the primary shaft  42  rotates in a counter-clockwise direction while the secondary shaft  74  rotates in a clockwise direction thereby raising the cutter assembly  32 . 
     Referring to FIG. 5, the cutter assembly positioning mechanism  10  of the present invention also includes a cutting height memory mechanism  76 . The memory mechanism  76  includes a stop  78  extending from the frame  26 . Preferably, the stop  78  defines a passage  80  for guiding the roller chain  38  therethrough. The cutting height memory mechanism  76  also includes a sleeve  82  defining a passage  84  with the roller chain  38  disposed therein. The sleeve  82  includes a first aperture  86  and a second aperture  88  for receipt of a pin  90 . The pin  90  is sized to cooperate with the roller chain  38  and the first and second apertures  86  and  88 . Specifically, the pin  90  has a diameter less than the minimum spacing between a pair of adjacent rollers  92  of the roller chain  38 . 
     In order to provide the cutting height memory mechanism  76  with a relatively fine adjustment increment, the first aperture  86  is spaced apart from the second aperture  88  a distance approximately equal to one and a half times the distance between adjacent roller chain links. Accordingly, when the operator of the riding lawn mower  12  wishes to establish a fixed cutting height, the operator translates the sleeve  82  along the roller chain  38  to abut with the stop  78  as shown in FIG.  6 . At this time, the pin  90  is disposed within the aperture best aligned with the space between the rollers  92  to set the memory mechanism  76 . Accordingly, the operator may raise the cutter assembly  32  for transport over rough terrain such as rocks or curbs and subsequently lower the cutter assembly  32  until the sleeve  82  engages the stop  78  thereby returning the cutter assembly  32  to exactly the same cutting height previously set. One skilled in the art will further appreciate that the cutting height memory mechanism  76  does not interfere with an anti-scalp lawn protection system  94 . 
     As best seen in FIG. 1, the anti-scalp system  94  includes a plurality of rollers  96  mounted at the forward edge  98  of the cutter assembly  32  to prevent the mower blades from damaging or scalping the turf when traversing uneven terrain. During operation, the anti-scalp system  94  operates to raise the cutter assembly  32  when the rollers  96  are contacted by an obstacle or rapidly changing ground elevation. The cutting height memory mechanism  76  cooperates with the anti-scalp system  94  by allowing the cutter assembly  32  to be lifted by the rollers  96  without operator intervention. Specifically, once the memory mechanism  76  has been set, the sleeve  82  is forced against the stop  78  thereby placing the roller chain  38  in a tensile mode. When in tension, the roller chain  38  limits the downward travel of the cutter assembly  32 . However, when an obstacle is encountered, the cutter assembly  32  is free to move in an upward direction because the roller chain  38  becomes slack and the sleeve  82  is no longer loaded against the stop  78 . As the riding lawn mower  12  enters smooth terrain, the rollers  96  will no longer be loaded and the cutter assembly  32  will lower until the sleeve  82  once again contacts the stop  78  thereby returning the cutter assembly to the height initially set. 
     Referring to FIG. 1, the actuator  36  is controlled by the operator&#39;s foot or feet. In the preferred embodiment, a first switch  100  and a second switch  102  are located on the floor pan  30  of the riding lawn mower  12 . The first switch  100  is preferably located near the operator&#39;s left foot and second switch  102  is preferably located near the operator&#39;s right foot. Depressing the first switch  100  causes the cutter assembly  32  to lower while depressing the second switch  102  causes the cutter assembly  32  to be raised relative to the ground. One skilled in the art will appreciate that a single switch system may also be implemented to raise and lower the cutter assembly without departing from the scope of the present invention. In addition, it should be appreciated that the actuator  36  may be of an electrical or a hydraulic type. 
     Referring to FIG. 7, the preferred embodiment utilizes an electrical control system  104  with the actuator  36  as depicted in the electrical schematic. The control system  104  functions to position the cutter assembly  32  by extending or retracting the actuator  36 . Specifically, the control system  104  includes a portable power source  106  preferably mounted to the frame  26  of the riding lawn mower  12 . The control system  104  also includes a circuit  108  including the first switch  100 , the second switch  102 , a first relay  110  and a second relay  112 . Each of the relays  110  and  112  are preferably of the dual position, dual throw type having a dual position switch and a coil operable to selectively change positions of the switch. The relay  110  includes a normally closed first position input  114 , a normally open second position input  116 , an output  118 , and a coil  120  selectively energizable for switching the first position  114  to open and the second position  116  to closed. The second relay  112  includes a first normally closed input  122 , a second normally open input  124 , an output  126 , and a coil  128 . 
     Beginning with the portable power source  106 , a first battery terminal  130  is connected to ground. A second battery terminal  132  is connected to one side of each of the coils  120  and  128 , a first position  114  of first relay  110 , and a second position  124  of second relay  112 . A first lead  134  of actuator  36  is connected to an output  118  of first relay  110 . A second lead  136  of the actuator  36  is connected to an output  126  of second relay  112 . Connected to ground are the second position  116  of first relay  110 , the first position  122  of the second relay  112  and the second side of each of the coils  120  and  128 . The first switch  100  is normally open and positioned between the ground and the first position  122  of the second relay  112  while the second switch  102  is positioned between the coils and ground. Accordingly, when switch  100  is depressed, power is delivered directly to the actuator  36  causing it to extend thereby lowering the cutter assembly  32 . Upon release of the first switch  100 , the actuator  36  stops due to an open circuit condition. If an operator wishes to raise the cutter assembly  32 , the second switch  102  is depressed to close the circuit and energize coils  120  and  128 . Once the coils have been energized, each of the relays  110  and  112  switch such that the second position is now closed and the first position is open. In effect, depression of switch  102  reverses polarity to the electric actuator  36  thereby causing the actuator to retract. 
     An alternate means of controlling the actuator includes implementing a single, three-positioned multi-pole electrical switch that would extend the actuator when moved in a first direction and retract the actuator when moved in a second direction. The single three-positioned switch may also be foot operated. 
     Another alternate means of controlling the actuator is by way of a single spool, three-position hydraulic valve. The hydraulic valve controls a hydraulic cylinder instead of the electric actuator  36  presented in the drawings. In operation, fluid circulates throughout the system while the hydraulic valve is in the center position. Once the hydraulic valve is moved to one of the two engaging positions, hydraulic fluid is directed to one end of the hydraulic cylinder to extend the actuator. Conversely, once the hydraulic valve is switched to the opposite engaged position, the hydraulic fluid forces the cylinder to retract. 
     The foregoing discussion discloses and describes merely exemplary embodiments of the present invention. One skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims, that various changes, modifications and variations may be made therein without departing from the spirit and scope of the invention as defined in the following claims.