WO2010030282A1

WO2010030282A1 - Drive disengagement mechanism for a lawn mower

Info

Publication number: WO2010030282A1
Application number: PCT/US2008/076152
Authority: WO
Inventors: Richard Bednar
Original assignee: Husqvarna U.S. Holding, Inc.
Priority date: 2008-09-12
Filing date: 2008-09-12
Publication date: 2010-03-18

Abstract

A power driven lawn mower (10) having a plurality of drive wheels (16) and characterized by a drive pulley (92) operated by an engine (12) and a driven pulley (96) for operating a transmission (14) coupled to the plurality of drive wheels (16). The power driven lawn mower (10) also includes a belt (100) trained about the drive pulley (92) and the driven pulley (96). An idler pulley (102) controls the tension of the belt (100) for engaging and disengaging the driven pulley (96). An idler arm (104) is pivotably mounted to a frame (20) of the lawn mower (10). The idler pulley (102) is mounted to the idler arm (104) to move the idler pulley (102) between a first position and a second position. In the first position, the belt (100) is tensioned to engage the driven pulley (96) and allow movement of the lawn mower (10) by the plurality of drive wheels (16). In the second position, tension is released on the belt (100) to disengage the driven pulley (96) to prevent the lawn mower (10) from being moved by the plurality of drive wheels (16). A throw-out bar (52) is pivotably mounted to the frame (20) for contacting the idler arm (104) to allow movement of the idler arm (104) to move the idler pulley (102) between the first and second positions. The lawn mower (10) further includes a mechanism (56) to control operation of the throw-out bar (52) by an operator.

Description

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DRIVE DISENGAGEMENT MECHANISM FOR A LAWN MOWER

FIELD OF THE INVENTION

The present invention relates to lawn care equipment and more particularly to a drive disengagement mechanism for a self-propelled or power driven lawn mower that automatically disengages the drive when the speed control is in the "start" position.

BACKGROUND

In self-propelled or power driven lawn mowers, such as walk-behind mowers or similar mowers, the mowers typically include an internal combustion engine that may be mechanically coupled or linked to a transmission for applying power to the drive wheels of the lawn mower. The transmission may be a hydrostatic pump or pumps for pumping a fluid to the drive wheels for propelling the lawn mower. Typically, the engine may be started without disengaging the transmission. However, there may also be some parasitic load associated with the transmission or hydrostatic pump when starting the engine. To over come these parasitic loads the state of the art utilizes a manual release to disengage the hydrostatic pumps. Additionally, under some conditions, for example as the mower ages, the transmission or hydrostatic pump and control means can wear and go out of adjustment. The mower may then immediately begin to creep or lurch forward when the engine of the mower is started.

SUMMARY In accordance with an embodiment of the present invention, a power driven lawn mower including a plurality of drive wheels is characterized by a drive pulley operated by an engine and a driven pulley for operating a transmission coupled to the plurality of drive wheels for powering the drive wheels. The power driven lawn mower also includes a belt trained about the drive pulley and the driven pulley. An idler pulley controls the tension of the belt for engaging and disengaging the driven pulley. An idler arm is pivotably mounted to a frame of the lawn mower. The idler pulley is mounted to the idler arm to move the idler pulley between a first position and a second position. In the first position, the belt is tensioned to engage the driven pulley and allow movement

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of the lawn mower by the plurality of drive wheels. In the second position, tension is released on the belt to disengage the driven pulley to prevent the lawn mower from being moved by the plurality of drive wheels. A throw-out bar is pivotably mounted to the frame for contacting the idler arm to allow movement of the idler arm to move the idler pulley between the first and second positions. The lawn mower further includes a mechanism to control operation of the throw-out bar by an operator.

In accordance with another embodiment of the present invention, a power driven lawn mower including a plurality of drive wheels is characterized by a base frame member and an upright frame member attached to the base frame member. The upright frame member includes a horizontal portion for locating devices for controlling operation of the lawn mower and also includes two vertical stanchion portions extending substantially perpendicular from opposite ends of the horizontal portion. Each vertical stanchion portion is attached at lower end thereof to the base frame member. An engine is mounted on an upper side the base frame member and has a drive shaft extending through an opening in the base frame member to an under side of the base frame member. A drive pulley is attached to the drive shaft of the engine on the under side of the base frame member. The lawn mower also includes a hydrostatic pump for driving the drive wheels of the lawn mower. The hydrostatic pump is mounted on the upper side of the base frame member and has a drive shaft extending through an opening in the base frame member to the under side of the base frame member. A driven pulley is attached to the drive shaft of the hydrostatic pump on the under side of the base frame member. A is belt trained about the drive pulley and the driven pulley. An idler pulley controls the tension of the belt for engaging and disengaging the driven pulley. An idler arm is pivotably mounted to a frame of the lawn mower. The idler pulley is mounted to the idler arm to move the idler pulley between a first position to tension the belt to engage the driven pulley and allow movement of the lawn mower by the plurality of drive wheels and a second position to release tension on the belt to disengage the driven pulley to prevent the lawn mower from being moved by the plurality of drive wheels. A biasing mechanism urges the idler arm into the first position to cause the idler pulley to increase tension on the belt to engage the driven pulley and cause operation of the hydrostatic pump to drive the drive wheels. A speed control selector is operable by the operator to

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control the speed of the lawn mower. A speed control linkage couples the speed control selector to the hydrostatic pump to control the speed of the lawn mower. A headed push rod is slideably coupled to the speed control linkage. The headed push rod is slidable to an extended position to engage and pivot the throw-out bar to move the idler arm and the idler pulley to the second position to release the belt tension and disengage the driven pulley of the transmission when the speed control selector is placed in a start position or disengaged position.

In accordance with another embodiment of the present invention, a method to control engagement of a plurality of drive wheels on a power driven lawn mower includes providing a mechanism to control operation of a throw-out bar by an operator. The method further includes pivotably mounting the throw-out bar to a frame of the lawn mower for contacting an idler arm to move the idler arm and an idler pulley attached to the idler arm between a first position to tension a belt to engage a driven pulley and allow movement of the lawn mower by the plurality of drive wheels and a second position to release tension on the belt to disengage the driven pulley to prevent the lawn mower from being moved by the plurality of drive wheels. The method further includes biasing the idler arm to move the idler pulley to the first position in response to the throw-out bar being release from holding the idler arm and the idler pulley in the second position. BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a perspective view of a power driven lawn mower in accordance with an embodiment of the present invention.

Figure 2 is a rear view of the power driven lawn mower of Figure 1 illustrating a throw-out bar of a drive disengagement mechanism and a mechanism to control operation of the throw-out bar and speed of the lawn mower in accordance with an embodiment of the present invention.

Figure 3 is a bottom view of a portion of the lawn mower of Figure 1 illustrating the drive disengagement mechanism in accordance with an embodiment of the present invention.

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Figure 4A is a side perspective view of a portion of the lawn mower of Figure 1 illustrating the throw-out bar in a first position to engage the drive wheels of the lawn mower in accordance with an embodiment of the present invention.

Figure 4B is a side perspective view of a portion of the lawn mower of Figure 1 illustrating the throw-out bar in a second position to disengage the drive wheels of the lawn mower in accordance with an embodiment of the present invention.

Figure 5 A is a detailed bottom view of the lawn mower of Figure 1 illustrating an idler pulley in a first position to engage a transmission of the lawn mower for transferring power to the drive wheels of the lawn mower in accordance with an embodiment of the present invention.

Figure 5B is a detailed bottom view of the lawn mower of Figure 1 illustrating the idler pulley in a second position to disengage the transmission of the lawn mower to prevent any transfer of power to the drive wheels of the lawn mower in accordance with an embodiment of the present invention.

DESCRIPTION OF THE INVENTION

The following detailed description of preferred embodiments refers to the accompanying drawings which illustrate specific embodiments of the invention. Other embodiments having different structures and operations do not depart from the scope of the present invention. Figure 1 is a perspective view of a power driven lawn mower 10 in accordance with an embodiment of the present invention. The lawn mower 10 may be a walk- behind hydrostatic drive lawn mower as illustrated and described herein, although the invention described herein may be applicable to other types of lawn mowers or vehicles. The lawn mower 10 may be powered by an internal combustion engine 12. The engine 12 may be mechanically coupled to a transmission 14 or drive. The transmission 14 or drive may be or may include a hydrostatic pump or pumps to drive the lawn mower 10. The transmission 14 or hydrostatic pumps are mechanically coupled to a plurality of drive wheels 16 for propelling the lawn mower 10. The engine 12 and transmission 14 are mounted on an upper side of a base frame member 18 of a frame 20 of the lawn mower 10. Each of the drive wheels 16 is rotatably mounted to the base frame member

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18 by suitable means including an axle 22 to permit rotation of the drive wheels 16 as driven or powered by the engine 12 and transmission 14 for movement of the lawn mower 10.

A mower deck 24 may be attached to a front portion 26 of the base frame member 18 by suitable means. At least one cutting blade 28 (shown in phantom in Figure 1) for cutting grass or the like may be disposed under the mower deck 24. The cutting blade 28 is mechanically coupled to the engine 12 for operation of the cutting blade 28. A pair of caster wheels 30 is mounted to a front portion 32 of the mower deck 24 at a suitable spacing from one another. The lawn mower 10 may also include an upright frame member 34 attached to a rear base frame section 36 of the base frame member 18. The rear base frame section 36 may be a separate frame member attached to a rear portion of the base frame member 18 and extending above the rear portion of the base frame member 18. The upright frame member 34 may include a horizontal frame portion 38 and two vertical stanchion frame portions 40. The vertical stanchion frame portions 40 extend substantially perpendicular from opposite ends of the horizontal frame portion 38. Each vertical stanchion frame portion 40 is attached at a lower end to the rear base frame section 36 of the base frame member 18. The horizontal frame portion 38 includes an area for locating devices for controlling operation of the lawn mower 10. For example, a groundspeed lever or speed control selector 42 may extend through a slot 44 formed in the horizontal frame portion 38 as described in more detail herein. The slot 44 may include a notch 45 (as best shown in Figure 2) to define a start position where the speed control selector 42 may be moved and retained in place to disengage the transmission 14 or hydrostatic pumps when starting the engine 12 as described in more detail herein. The slot 44 may include an elongated vertical segment 47 (Figure 2) extending in a forward direction relative to a direction of travel of the lawn mower 10 or in a vertical direction relative to an operator and away from the operator of the lawn mower 10. The lawn mower 10 may then be propelled at faster speeds as the speed control selector 42 is pushed forward and away from the operator to faster positions within the slot 44. The lawn mower 10 may be propeller at slower speeds as the speed control selector 42 is pulled back or rearward in the slot 44 toward the operator to slower positions within the slot 44. The notch 45 or

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shorter slot segment may extend perpendicular to the elongated vertical segment 47 at an end of the elongated vertical segment 47 that is closest to the operator to define the start position or disengaged position. The slot 44 may be positioned in substantially a central position or middle location in the horizontal frame portion 38 for ease of operation by the operator.

Operator handles 46 may also be mounted to the horizontal frame portion 38 for directional control of the lawn mower 10. The operator handles 46 are coupled to the transmission 14 or hydrostatic pumps by linkages 48. Through operation of the handles 46 and operator can turn and control the direction of movement of the lawn mower 10. In a hydrostatically driven mower, controls associated with each of the handles 46 manipulates the respective linkage 48 to control the fluid flow to each of the drive wheels 16 to control the direction of movement of the mower 10. With the multiple devices for controlling the operation of the lawn mower 10 by an operator, the horizontal frame portion 38 may define a control panel. The vertical stanchion frame portions 40 may be attached to the base frame member 18 in a manner that the horizontal frame portion 38 is slightly angled to provide a more ergonomic presentation of the horizontal frame portion 38 or control panel to the operator for controlling the lawn mower 10. Guards 50 may also be provided to protect an operator's hands when holding the handles 46. Each guard 50 may extend from a front portion of the respective handle 46 and extend rearward in front of the handles 46 to protect the operator's hands.

Referring also to Figures 2 and 3, Figure 2 is a rear view of the power driven lawn mower 10 of Figure 1 illustrating a throw-out bar 52 of a drive disengagement mechanism 54 and a mechanism 56 (best shown in Figure 3) to control operation of the throw-out bar 52 and to control speed of the lawn mower 10 in accordance with an embodiment of the present invention. Figure 3 is a bottom view of a rear portion 58 of the lawn mower 10 of Figure 1 illustrating the drive disengagement mechanism 54 in accordance with an embodiment of the present invention.

The mechanism 56 to control operation of the throw-out bar 52 and to control speed of the lawn mower 10 includes the speed control selector 42 and a speed control linkage 60 to couple the speed control selector 42 to the transmission 14 or hydrostatic pumps to control the speed of the lawn mower 10. The speed control selector 42

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includes a lever moveable in the slot 44 to control operation of the throw-out bar 52 and groundspeed of the lawn mower 10 as further described herein.

The speed control selector 42 is attached to a speed control bar 62. The speed control bar 62 is pivotably mounted to an underside of the horizontal frame portion 38 of the upper frame member 34 by suitable fasteners 64 that permit the speed control bar 62 to pivot or rotate in response to an operator moving the speed control selector 42. The speed control bar 62 may extend completely across the underside of the horizontal frame portion 38 in a direction substantially perpendicular to the vertical stanchion portions 40 and the elongated segment 47 of the slot 44. The speed control bar 62 may then be pivotably attached by the suitable fasteners 64 at opposite sides of the horizontal frame portion 38 or to the respective opposite vertical stanchion portions 40 of the upright frame member 34 proximate to the horizontal frame portion 38.

As shown in Figure 3, a lever arm 66 extends substantially perpendicular from the speed control bar 62. The lever arm 66 may extend from the speed control bar 62 at a location offset from a location where the speed control selector 42 attaches to the speed control bar 62. A tube 68 is coupled at one end by a threaded stud 70 and a flexible joint or coupler 72 to the lever arm 66 of the speed control bar 62. The threaded stud 70 permits adjustment of the length of the speed control linkage 60 relative to the speed control bar 62 and the lever arm 66. A length of the threaded stud 70 may be secured in place relative to the tube 68 by a lock nut.

The mechanism 56 to control operation of the throw-out bar 52 also includes a headed push rod 74. The headed push rod 74 may include a flat or button-shaped head 76 for contacting the throw-out bar 52. The headed push rod 74 may be threaded at an end opposite to the button-shaped head 76 for attaching to a lower end to the tube 68. The threaded end of the headed push rod 74 permits further adjustment of the length of the speed control linkage 60. The length of the headed push rod 74 may be secured in place relative to the tube 68 by a lock nut.

As best shown in Figures 4A and 4B, the headed push rod 74 is slidably received in a swivel fitting 78. The swivel fitting 78 connects the speed control linkage 60 to a speed control arm 80 of a cam shaft 82 for controlling the speed of the transmission 14 (Figures 1 and 2) or fluid flow in the hydrostatic pumps for controlling the speed of the

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lawn mower 10 as previously described. The cam shaft 82 is pivotably mounted in supports 84 for rotation by the speed control arm 80 and speed control linkage 60 in response to movement of the speed control selector 42 (Figure 2) by the operator to control the speed of the transmission 12 and lawn mower 10. The cam shaft supports 84 are mounted to the base frame member 18. The speed control arm 80 may be attached to an end of the cam shaft 82 extending just beyond one of the cam shaft supports 84. The cam shaft supports 84 may be spaced from one another with the cam shaft 82 extending between the cam shaft supports 84 for rotation therein. Accordingly, the cam shaft 82 may be rotatably supported at one end by one cam shaft support 84 and rotatably supported proximate to another end of the of the cam shaft 82 by another one of the cam shaft supports 84 proximate to the speed control arm 80.

The headed push rod 74 may be biased to maintain contact with the throw-out bar 52 when the speed control selector 42 is moved to the start position (notch 45) for starting the engine 12 of the lawn mower 10 as previously described. The headed push rod 74 may be biased by inserting the headed push rod 74 through the coil spring 86. The coil spring 86 may be captured between the swivel fitting 78 and a washer 88 fixed in place on the headed push rod 74 by a roll pin 90. Referring to Figure 4B, the coil spring 86 is compressed when the headed push rod 74 engages and pivots the throw-out bar 52 to maintain the throw-out bar 52 in a position to disengage the transmission 14 when the speed control selector 42 is moved to the start position or a disengaged position. As the speed control selector 42 is moved by an operator to a slow position in the slot 44 in a direction back toward the operator and notch 45, the speed control arm 80 contacts a stop 81 (best shown in Figure 2). The stop 81 may be formed as extension from the cam shaft support 84 supporting the end of the cam shaft 82 to which the speed control arm 80 is attached. As the speed control selector 42 continues to be moved by the operator toward the start position or notch 45, the speed control arm 80 becomes stationary after contacting the stop 81. The spring 86 begins to compress as the headed push rod 74 is further extended by the speed control linkage 60 causing the headed push rod 74 to be slid through the swivel fitting 78 and to come in contact with throw-out bar 52. Further movement of the speed control selector 42 in a back direction toward the operator position compresses the spring 86 even further allowing the push rod 74 to

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activate the throw-out bar 52 by pivoting the throw-out bar 52 in a downward direction to a disengaged position to disengage the drive or transmission as described herein.

As shown in Figure 3, the lawn mower 10 includes a drive pulley 92 attached to a drive shaft 94 of the engine 12 (Figure 1). A driven pulley 96 is attached to a drive shaft 98 of the transmission 14 or hydrostatic pumps (Figure 1). A belt 100 is trained about the drive pulley 92 and the driven pulley 96. An idler pulley 102 is disposed between the drive pulley 92 and driven pulley 96 within the loop of the belt 100. The idler pulley 102 is rotatably mounted to an idler arm 104. The idler arm 104 is pivotably mounted to the base frame member 18. The idler arm 104 may be pivotably mounted to the base frame member 18 by a suitable fastener at a pivot point 106 on the idler arm 104. The pivot point 106 may be proximate to an end of the idler arm 104 opposite to an end of the idler arm 104 where the idler pulley 102 is mounted to the idler arm 104.

Referring also to Figures 5 A and 5B, Figure 5 A is a detailed bottom view of the lawn mower 10 of Figure 1 illustrating the idler pulley 102 in a first position to tension the belt 100 to engage the transmission 12 of the lawn mower 10 for transferring power to the drive wheels 16 of the lawn mower 10. Figure 5B is a detailed bottom view of the lawn mower 10 of Figure 1 illustrating the idler pulley 102 in a second position to disengage the transmission 12 of the lawn mower 10 to prevent any transfer of power to the drive wheels 16 of the lawn mower 10 or to prevent creeping of the lawn mower 10 when the speed control selector 42 (Figure 2) is in the start position or disengaged position. A biasing mechanism 108 causes the idler arm 104 to move the idler pulley 102 to the first position or transmission engaged position in response to the mechanism 56 to control operation of the throw-out bar 52 being released from holding the idler arm 104 and idler pulley 102 in the second position or transmission disengaged position. The biasing mechanism 108 may include a coil spring 110 anchored at one end to an attachment point 112 on an interior of the base frame member 18 and attached at another end to the idler arm 104. The other end of the coil spring 110 may be attached to the idler arm 104 at an attachment point 114 corresponding substantially to a hub of the idler pulley 102. The coil spring 100 must have a sufficient high spring constant to hold the idler arm 104 and idler pulley 102 in the first or engaged position under load or

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movement of the lawn mower 10 over the mower's entire speed range without slippage of the belt 100.

The throw-out bar 52 may include an elongated center portion 116 and an end tab portion 118 at each end of the elongated center portion 116 extending perpendicular to the elongated center portion 116. Each end tab portion 118 has a hole formed therein for pivotably attaching the throw-out bar 52 to opposite sides of the frame 18 or rear base frame section 36 using a suitable fastener 120 as shown in Figures 4A and 4B. The elongated center portion 1 16 extends substantially parallel to a rear side 122 of the frame 18 on an exterior of the frame 18. A coil spring 121 (Figure 2) may be attached between the throw-out bar 52 and the frame 20 or one of the vertical stanchion frame portions 40 to bias the throw-out bar 52 in an up position or disengaged position and to prevent the throw-out bar 52 from loosely bouncing or pivoting up and down or rattling as the lawn mower 10 operates.

The throw-out bar 52 may also include a contact projection 124 extending substantially perpendicular from the throw-out bar 52 for extending through an opening 126 formed in the rear side 122 of the frame 18 (Figures 4A and 4B) to contact the idler arm 104 as shown in Figures 5A and 5B.

The idler arm 104 may include an appendage 126 extending from the idler arm 104. The appendage 126 may extend substantially perpendicular to the idler arm 104 proximate to the pivot point 106 or an end of the idler arm 104 opposite to the idler pulley 102. A round headed bolt or bumper 128 may be attached to the appendage 126. The round headed bolt or bumper 128 may be received by a threaded hole formed in the appendage 126. The distance or amount of projection the round headed bolt or bumper 128 extends from the appendage 126 may be adjusted by screwing the round headed bolt or bumper 128 into or out of the threaded hole in the appendage 124. A pair of lock nuts on either side of the opening in the appendage 126 may retain the bumper 128 at the desired position for contacting the contact projection 124 of the throw-out bar 52.

In operation, the contact projection 124 of the throw-out bar 52 may contact the bumper 110 to push the idler arm 104 to move the idler pulley 102 to the second position or disengaged position as shown in Figure 5B in response to the throw-out bar 52 being pivoted by the control mechanism 56 when the speed control selector 42 is placed in the

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start position or disengaged position by the operator. The coil spring 110 will pull the idler arm 104 and the idler pulley 102 into the first position or the engaged position as shown in Figure 5A in response to the operator moving the speed control selector 42 from the start position (notch 45 in Figure 2) and begins moving the speed control selector 42 forward in the elongated segment 47 of the slot 44 to apply power to the drive wheels 16 and increase the groundspeed of the lawn mower 10 in correspondence to forward movement of the speed control selector 42.

In accordance with an embodiment of the present invention, the speed control selector 42 or another element of the mechanism 56 for disengaging the drive may be electromechanically interconnected with a start switch 130 (Figure 1) so that the engine 12 will only start when the transmission 14 or pump drive is disengaged eliminating creeping of the lawn mower 10. Additionally, the engine 12 may be easier to start by eliminating any parasitic load that may be caused by turning the transmission 12 or the hydrostatic pump. As an example, the speed control selector 42 in the start position (notch 45) may operate a switch to permit a circuit to be completed or closed when the start switch 130 is also operated for starting the engine 12.

Although specific embodiments have been illustrated and described herein, those of ordinary skill in the art appreciate that any arrangement which is calculated to achieve the same purpose may be substituted for the specific embodiments shown and that the invention has other applications in other environments. For example, the structure and method of the present invention may be used for any type of powered vehicle. This application is intended to cover any adaptations or variations of the present invention. The following claims are in no way intended to limit the scope of the invention to the specific embodiments described herein.

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Claims

Attorney Docket No. 1R1293US00-7What is claimed is:

1. A power driven lawn mower (10) having a plurality of drive wheels (16), characterized by: a drive pulley (92) operated by an engine (12); a driven pulley (96) for operating a transmission (14) coupled to the plurality of drive wheels (16); a belt (100) trained about the drive pulley (92) and the driven pulley (96); an idler pulley (102) to control the tension of the belt (100) for engaging and disengaging the driven pulley (96); an idler arm (104) pivotably mounted to a frame (20) of the lawn mower (10), wherein the idler pulley (102) is mounted to the idler arm (104) to move the idler pulley (102) between a first position to tension the belt (100) to engage the driven pulley (96) and allow movement of the lawn mower (10) by the plurality of drive wheels (16) and a second position to release tension on the belt (100) to disengage the driven pulley (96) to prevent the lawn mower (10) from being moved by the plurality of drive wheels (16); a throw-out bar (52) pivotably mounted to the frame (20) for contacting the idler arm (104) to allow movement of the idler arm (104) to move the idler pulley (102) between the first and second positions; and a mechanism (56) to control operation of the throw-out bar (52) by an operator.

2. The power driven lawn mower (10) of claim 1 characterized by a biasing mechanism (110) to cause the idler arm (104) to move the idler pulley (102) to the first position in response to the mechanism (56) to control operation of the throw-out bar (52) being release from holding the idler arm (104) and the idler pulley (102) in the second position.

3. The power driven lawn mower (10) of claim 1 wherein the throw-out bar (52) is characterized by an elongated center portion (116) and an end tab portion (118) at each end of the elongated center portion (1 16) extending perpendicular to the elongated center

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portion (116), each end tab portion (118) having a hole formed therein for pivotably attaching the throw-out bar (52) to opposite sides of the fame (20, 36) and the elongated center portion (116) of the throw-out bar (52) extending substantially parallel to a rear side (122) of the frame (18) on an exterior of the frame (18).

4. The power driven lawn mower (10) of claim 3 wherein the throw-out bar (52) is further characterized by a contact projection (124) extending substantially perpendicular from the throw-out bar (52) for extending through a opening (126) in the rear side (122) of the frame (18) to contact the idler arm (104), wherein the contact projection(124) pushes the idler arm (104) to move the idler pulley (102) to the second position in response to the throw-out bar (52) being pivoted by the control mechanism (56) being moved to a disengaged position by the operator.

5. The power driven lawn mower (10) of claim 1 wherein the mechanism (56) to control operation of the throw-out bar (52) is characterized by: a speed control selector (42) operable by the operator; a speed control linkage (60) to couple the speed control selector (42) to the transmission (14) to control a speed of the lawn mower (10); and a headed push rod (74) slideably coupled to the speed control linkage (60) wherein the headed push rod (74) is slidable to an extended position to engage and pivot the throw-out bar (52) to move the idler arm (104) and idler pulley (102) to the second position to release the belt tension and disengage the driven pulley (96) of the transmission (14) when the speed control selector (42) is placed in a start position.

6. The power driven lawn mower (10) of claim 5, wherein the headed control rod (74) is biased to maintain contact with the throw-out bar (52) when the speed control selector (42) is in the start position.

7. The power driven lawn mower (10) of claim 5, wherein the speed control linkage (60) is characterized by:

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a speed control bar (62) pivotably mounted to an under side of an upper frame member (34) of the lawn mower (10); a lever arm (66) extending from the speed control bar (62); a tube (68) coupled at one end to the lever arm (66) by a threaded stud (70) to permit adjustment of a length of the speed control linkage (60) relative to the speed control bar (62) and the lever arm (66), wherein the headed push rod (74) is received in the tube (68) at an end of the headed push rod (74) opposite a headed end (76) of the push rod (74); a cam shaft (82) for controlling the speed of the transmission (14); a speed control arm (80) attached to the cam shaft (82) for rotation of the cam shaft (82) to adjust the speed of the transmission (14); and a swivel fitting (78) attached to the speed control arm (80), wherein the headed push rod (74) is slidably received through an opening in the swivel fitting (78) to engage the throw-out bar (52).

8. The power lawn mower (10) of claim 7, characterized by a coil spring (86), the headed push rod (74) being disposed through the coil spring (86) and the coil spring (86) being disposed between the swivel fitting (78) and a washer (88) fixed in place on the headed push rod (74), wherein the coil spring (86) is compressed when the headed push rod (74) engages and pivots the throw-out bar (52) to maintain the throw-out bar (52) in a position to disengage the driven pulley (96) when the speed control selector (42) is in the start position or a disengaged position.

9. The power driven lawn mower (10) of claim 5, further characterized by: a base frame member (18) of the frame (20); an upright frame member (34) including a horizontal portion (38) and two vertical stanchion portions (40) extending substantially perpendicular from opposite ends of the horizontal portion (38), each vertical stanchion portion (40) being attached at a lower end to the base frame member (18); a slot (44) formed in the horizontal portion (38) of the upright frame member (34), the slot (44) including an elongated vertical segment (47) extending in a

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forward direction relative to a direction of travel of the lawn mower and away from the operator of the lawn mower and a shorter segment (45) extending perpendicular to the elongated vertical segment (47) at an end of the elongated vertical segment (47) closest to the operator, wherein the shorter segment (45) defines the start position; and wherein the speed control selector (42) is characterized by a lever extending through the slot in the horizontal portion (38) of the upright frame member (34).

10. The power driven lawn mower (10) of claim 1, wherein the transmission (14) is characterized by a hydrostatic pump.

11. A power driven lawn mower (10) including a plurality of drive wheels (16), characterized by: a base frame member (18); an upright frame member (34) attached to the base frame member (18), wherein the upright frame member (34) includes a horizontal portion (38) for locating devices for controlling operation of the lawn mower (10) and two vertical stanchion portions (40) extending substantially perpendicular from opposite ends of the horizontal portion (38), each vertical stanchion portion (40) being attached at lower end to the base frame member (18); an engine (12) mounted on an upper side the base frame member (18) having a drive shaft (94) extending through an opening in the base frame member (18) to an under side of the base frame member (18); a drive pulley (92) attached to the drive shaft (98) of the engine (12) on the under side of the base frame member (18); a hydrostatic pump (14) for driving the drive wheels (16) of the lawn mower (10), the hydrostatic pump (14) being mounted on the upper side of the base frame member (18) and having a drive shaft (98) extending through an opening in the base frame member (18) to the under side of the base frame member (18); a driven pulley (96) attached to the drive shaft (98) of the hydrostatic pump (14) on the under side of the base frame member (18);

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a belt (100) trained about the drive pulley (92) and the driven pulley (96); an idler pulley (102) to control the tension of the belt (100) for engaging and disengaging the driven pulley (96); an idler arm (104) pivotably mounted to a frame (18, 20) of the lawn mower (10), wherein the idler pulley (102) is mounted to the idler arm (104) to move the idler pulley (102) between a first position to tension the belt (100) to engage the driven pulley (96) and allow movement of the lawn mower (10) by the plurality of drive wheels (16) and a second position to release tension on the belt (100) to disengage the driven pulley (96) to prevent the lawn mower (10) from being moved by the plurality of drive wheels (16); a biasing mechanism (108) to urge the idler arm (104) into the first position to cause the idler pulley (102) to increase tension on the belt (100) to engage the driven pulley (96) and cause operation of the hydrostatic pump (14) to drive the drive wheels

(16); a speed control selector (42) operable by the operator; a speed control linkage (60) to couple the speed control selector (42) to the hydrostatic pump (14) to control a speed of the lawn mower (10); and a headed push rod (74) slideably coupled to the speed control linkage (60) wherein the headed push rod (74) is slidable to an extended position to engage and pivot the throw-out bar (52) to move the idler arm (104) and idler pulley (102) to the second position to release the belt tension and disengage the driven pulley (96) of the hydrostatic pump (14) when the speed control selector (42) is placed in a start position or disengaged position.

12. The power driven lawn mower (10) of claim 11 wherein the throw-out bar (52) is characterized by: an elongated center portion (116) and an end tab portion (118) at each end of the elongated center portion (116) extending perpendicular to the elongated center portion (116), each end tab portion (118) having a hole formed therein for pivotably attaching the throw-out bar (52) to opposite sides of the fame (20) and the elongated center

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portion (116) of the throw-out bar (52) extending substantially parallel to a rear side (122) of the frame (18, 20) on an exterior of the frame (18, 20); and a contact projection (124) extending substantially perpendicular from the throw-out bar (52) for extending through a opening (126) in the rear side (122) of the frame (18, 20) to contact the idler arm (104), wherein the contact projection (124) pushes the idler arm (104) to move the idler pulley (102) to the second position in response to the throw-out bar (52) being pivoted by the control mechanism (56) being moved to a disengaged position by the operator.

13. The power driven lawn mower (10) of claim 11, wherein the headed control rod (74) is biased to maintain contact with the throw-out bar (52) when the speed control selector (42) is in the start position.

14. A method to control engagement of a plurality of drive wheels (16) on a power driven lawn mower (10), characterized by: providing a mechanism (56) to control operation of a throw-out bar (52) by an operator; pivotably mounting the throw-out bar (52) to a frame (20) of the lawn mower (10) for contacting an idler arm (104) to move the idler arm (104) and an idler pulley (102) attached to the idler arm (104) between a first position to tension a belt (100) to engage a driven pulley (96) and allow movement of the lawn mower (10) by the plurality of drive wheels (16) and a second position to release tension on the belt (100) to disengage the driven pulley (96) to prevent the lawn mower (10) from being moved by the plurality of drive wheels (16); biasing the idler arm (104) to move the idler pulley (102) to the first position in response to the throw-out bar (52) being release from holding the idler arm (104) and the idler pulley (102) in the second position.

15. The method of claim 14, wherein pivotably mounting the throw-out bar (52) to the frame (20) is further characterized by pivotably attaching end tab portions (118) of the

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throw-out bar (52) to opposite sides of the fame (20) with an elongated center portion (116) of the throw-out bar (52) extending substantially parallel to a rear side (122) of the frame (20) on an exterior of the frame (20).

16. The method of claim 15, further characterized by extending a contact projection (124) from the throw-out bar (52) through a opening (126) in the rear side (122) of the frame (18, 20) to contact the idler arm (104), wherein the contact appendage (124) pushes the idler arm (104) to move the idler pulley (102) to the second position in response to the throw-out bar (52) being pivoted to a disengaged position by the operator.

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