Adjustable suspension system for off-road vehicle

A support assembly includes a first support frame having a first bearing surface, and a second support frame spaced a vertical distance from the first support frame. A biasing member is connected to the first support frame and includes a first end and a second end. The first end bears against the first bearing surface. An adjustment assembly is connected to the second support frame and is adjustable with respect to the second support frame. The second end of the biasing member bears against the adjustment assembly.

BACKGROUND

The present invention relates to off-road vehicles and suspension systems for a seat assembly in off-road vehicles.

SUMMARY

In one embodiment, the invention provides a support assembly including a first support frame having a first bearing surface, a second support frame spaced a vertical distance from the first support frame and a suspension having a plurality of suspension arms connected at a first end to the first support frame and connected at a second end to the second support frame. A biasing member is connected to the first support frame and has a first end and a second end, and the first end bears against the first bearing surface. A lever is connected to the second support frame at a lever first end, and pivots with respect to the second support frame. The lever has a second bearing surface, and the second end of the biasing member bears against the second bearing surface. A user actuable control is connected to the lever to adjust the angle of the lever with respect to horizontal upon actuation of the user actuable control. The second end of the biasing member moves along the second bearing surface as the first support frame moves with respect to the second support frame. The lever pivots between a first position in which the lever is at a first angle with respect to horizontal, and a second position in which the lever is at a second angle with respect to horizontal. When the lever is in the first position, the first end of the biasing member moves along the lever at the first angle with respect to horizontal between a first upper position and a first lower position. The first upper position is spaced a first horizontal distance and a first vertical distance away from the first lower position, and the biasing member is deflected a first distance between the first upper position and the first lower position. When the lever is in the second position, the first end of the biasing member moves along the lever at the second angle with respect to horizontal between a second upper position and a second lower position. The second upper position is spaced a second horizontal distance and a second vertical distance away from the second lower position, and the biasing member is deflected a second distance between the second upper position and the second lower position. The first angle is greater than the second angle and the second deflection is greater than the first deflection.

In another embodiment, the invention provides a support assembly includes a first support frame having a first bearing surface, and a second support frame spaced a vertical distance from the first support frame. A biasing member is connected to the first support frame and includes a first end and a second end. The first end bears against the first bearing surface. An adjustment assembly is connected to the second support frame and is adjustable with respect to the second support frame. The second end of the biasing member bears against the adjustment assembly.

DETAILED DESCRIPTION

FIG. 1illustrates an off-highway vehicle10that includes a chassis15, wheels20supporting the chassis15, an internal combustion engine25mounted to the chassis15, a seat30mounted to the chassis15, a control panel35, control levers40, and a mower deck45. An operator zone of the vehicle10includes the seat30and controls and components within reach of an operator seated in the seat30(e.g., the control panel35and the control levers40). One suitable off-highway vehicle is commonly referred to as a zero-turn radius lawn mower, but the invention may be embodied in other types of off-highway vehicles and other vehicles intended for road use; the invention is not limited to the application illustrated.

In the illustrated embodiment, the engine25includes an ignition system50that provides a spark or other event that drives combustion within the internal combustion engine25. Although the engine25in the illustrated embodiment is of the internal combustion variety, the invention is applicable to any type of engine, and the term “ignition system,” as applied to this invention, refers to the part of the engine that sustains its continued operation. In this regard, the ignition system50may be termed an ignition circuit that permits operation of the engine25when closed and disables operation of the engine25when open. Although the illustrated embodiment includes an internal combustion engine25, the present invention may be applied to vehicles and systems having alternative prime movers, such as batteries or other energy storage devices, fuel cells, or gas/electric hybrid drive systems. In such other embodiments, the ignition system would include the electric circuit that enables and disables the prime mover to operate or that enables and disables the vehicle drive and implement systems to operate under the influence of the prime mover.

In the illustrated embodiment, the engine25drives rotation of at least one of the wheels20through a transmission (e.g., a hydraulic, electric, or mechanical transmission). The operator independently controls speed and direction of rotation of the left and right side wheels20via the control levers40. In some embodiments, the engine25also selectively drives rotation of one or more cutting blades under the mower deck45to cut vegetation over which the vehicle10travels.

With reference toFIG. 2, the seat30includes a back cushion60, a back frame65, a bottom cushion70, a bottom frame assembly75, a flexible bellows80, and an adjustment assembly85. The seat30accommodates an operator of the vehicle10. The back frame65supports the back cushion60, and the bottom frame assembly75supports the bottom cushion70. The flexible bellows80substantially encloses the bottom frame assembly75and adjustment assembly85, while accommodating movement of the bottom frame assembly75.

With reference toFIG. 3, the bottom frame assembly75includes a front portion90, a rear portion95, a left side portion100, a right side portion105, a lower support frame110, an upper support frame115, a first suspension arm120a, a second suspension arm120b, a third suspension arm125a, a fourth suspension arm125b, a first torsion spring130a(FIG. 5), and a second torsion spring130b(FIGS. 4 and 5). The terms “front,” “rear,” “left,” and “right” are from the perspective of an operator seated in the seat30during normal use of the vehicle10. A “front portion” of the seat30is the portion closer to the front portion90of the bottom frame assembly75than to the rear portion95, and a “rear portion” of the seat30is the portion closer to the rear portion95of the bottom frame assembly75than to the front portion90.

The left side portion100and right side portion105extend between the front portion90and the rear portion95. The lower support frame110is coupled to the chassis15and the upper support frame115supports the bottom cushion70.

The first and second suspension arms120a,120bare pivotably coupled at one end to the lower support frame110in the front portion90, and are pivotably coupled at an opposite end to the upper support frame115in the rear portion95. The pivotable interconnections of the ends of the first and second suspension arms120a,120bare fixed, which is to say that the pivot point for each end does not move with respect to the frame to which it is mounted. The first suspension arm120ais positioned on the left side portion100and the second suspension arm120bis positioned on the right side portion105. The first suspension arm120ais substantially a mirror image of the second suspension arm120b.

The third and fourth suspension arms125a,125bare coupled at one end to the lower support frame110in the rear portion95, and are coupled at an opposite end to the upper support frame115in the front portion90. The interconnections between the third and fourth suspension arms125a,125band the lower and upper frame assemblies110,115are movable pivots, which is to say that the pivot point for each end of the third and fourth suspension arms125a,125bcan move (in the illustrated embodiment such movement being translational) with respect to the frame to which it is mounted. The third suspension arm125ais positioned on the left side portion100and the fourth suspension arm125bis positioned on the right side portion105. The third suspension arm125ais substantially a mirror image of the fourth suspension arm125b.

The first suspension arm120ais coupled to the third suspension arm125aand the second suspension arm120bis coupled to the fourth suspension arm125bto form a scissor suspension arrangement. The upper support frame115is vertically moveable with respect to the lower support frame110in response to the suspension arms120a,120b,125a,125bpivoting with respect to the lower and upper support frames110,115. As the scissor suspension arrangement is actuated, the pivot point that interconnects the first and third suspension arms120a,125aand the pivot point that interconnects the second and fourth suspension arms120b,125bmoves generally up and down. In this regard, the suspension arms can be said to be coupled at a moving pivot point.

The upper support frame115is vertically moveable with respect to the lower support frame110in response to the first and second suspension arms120a,120bpivoting with respect to the lower and upper support frames110,115and in response to the third and fourth suspension arms125a,125bpivoting and translating with respect to the lower and upper support frames110,115.

As the upper support frame115moves up and down with respect to the lower support frame110, the first and second suspension arms120a,120bpivot with respect to the lower and upper support frames110,115, and the third and fourth suspension arms125a,125bpivot about and translate along the lower and upper support frames110,115. The third suspension arm125arotates with respect to the first suspension arm120aand the fourth suspension arm125brotates with respect to the second suspension arm120b.

In some embodiments, the upper support frame115is moveable between about two and about four inches with respect to the lower support frame110(e.g., the seat has a stroke of between 2 inches and 4 inches). In some embodiments, the upper support frame115is moveable about three inches with respect to the lower support frame110(e.g., the seat has a stroke of 3 inches). The illustrated seat30is a low-profile suspension seat that has a seating index point of about eight inches measured per SAE J1163 SPEC.

In some embodiments, the seat30can be positioned in a vehicle (such as a truck) in which the upper support frame115is moveable between about four inches and about eight inches with respect to the lower support frame110(e.g., the seat has a stroke of between 4 inches and 8 inches). In some embodiments, the upper support frame115is moveable about six inches with respect to the lower support frame110(e.g., the seat has a stroke of about 6 inches).

With reference toFIGS. 4 and 5, the first and second torsion springs130a,130beach include a first end135a,135bhaving a first length, a second end140a,140bhaving a second length, and a coil defining a coil axis and extending between the first and second ends135a,135band140a,140b. The first and second torsion springs130a,130bare coupled to the lower support frame110and the first ends135a,135bbear against a bearing surface on the lower support frame110. Although torsion springs are included in the illustrated embodiment, other biasing members can be utilized in place of the torsion springs.

With reference toFIGS. 4-6, the adjustment assembly85includes a handle150, a threaded shaft155, a coupling nut160, a housing165, a lever170, a splice tube175, and a roller180. The handle150, the threaded shaft155and the coupling nut160together form a user actuable control. The handle150is positioned proximate the front portion90of the seat30, to permit a user to grasp the handle150while sitting in the seat30. In this regard, the handle150may be said to be in the operator zone. The handle150is coupled to the threaded shaft155for rotation with the threaded shaft155.

The housing165includes a bearing surface190that bears against a flat surface of the coupling nut160to inhibit rotation of the coupling nut160with respect to the housing165. Rotation of the handle150and the threaded shaft155causes the coupling nut160to move linearly, which in the illustrated embodiment is also laterally (left and right inFIG. 6). The handle150includes a shoulder that inhibits movement of handle150toward the lever170and a washer is coupled to the threaded shaft155between the threads and the housing165to inhibit movement of the handle150away from the lever170. Therefore, the handle150is retained in substantially the same location with respect to the seat30, so that a user has consistent access to grasp the handle150. Since the handle150is inhibited from lateral movement by the shoulder and the washer, rotation of the handle150causes lateral movement of the coupling nut160along the threaded shaft155. The threaded shaft155and coupling nut160have coarse threads to linearly move the coupling nut160more rapidly than would be possible with fine threads. This increases or maximizes the linear travel of the coupling nut160per rotation of the handle150. While the rotatable handle150is illustrated, other suitable user actuable controls can be utilized to pivot the lever170with respect to the housing165.

The housing165further includes a stop195that limits rotation of the lever170to a desired range of rotation. The stop195can take on any suitable form, but the illustrated stop is a substantially cylindrical projection extending through a portion of the lever170.

The lever170is positioned between the coupling nut160and the roller180(i.e., the coupling nut160bears on one side of the lever170and the roller180bears on an opposite side of the lever170). The lever170includes a first end200, a second end205, a bearing surface210, a bearing plate215and an aperture220. The first end200is coupled to the housing165for rotation about the housing165. The second end205is spaced from the first end200and is free to move with respect to the housing165.

The bearing surface210is positioned between the first end200and the second end205of the lever. The bearing surface210abuts the roller180and bears against the roller180. The second ends140a,140bof the torsion springs130a,130bbias the roller180against the bearing surface210. In the illustrated embodiment, the bearing surface210is an integral part of the lever170. In other embodiments, a separate component is coupled to the lever170to form the bearing surface.

The bearing plate215is coupled to the lever170between the first end200and the second end205of the lever170. The bearing plate215is positioned to abut the coupling nut160. In the illustrated embodiment, the bearing plate215is metallic and the lever170is plastic. However, other materials or combinations of materials can be utilized in other embodiments.

The aperture220receives the stop195of the housing165. The aperture220permits rotation of the lever170within a range of angles with respect to the housing165and inhibits rotation of the lever170outside the range of angles with respect to the housing165. InFIG. 6, the lever170is in an intermediate position within the range of angles.

InFIG. 7, the lever170is in a first end position defining a first end of the range of angles. In the illustrated embodiment, the lever170is positioned at about70degrees with respect to the horizontal in the first end position. In other embodiments, the lever170can be positioned at about 90 degrees with respect to horizontal in the first end position. When the lever170is in the first end position, the stop195is at a first end of the aperture220.

InFIG. 8, the lever170is in a second end position defining a second end of the range of angles. In the illustrated embodiment, the lever170is positioned at about 45 degrees with respect to the horizontal in the second end position. In other embodiments, the lever170can be positioned at about 25 degrees with respect to horizontal. When the lever170is in the second end position, the stop195is at a second end of the aperture220. Other angles and ranges of angles are possible and the illustrated embodiment is given by way of example only.

The springs130a,130bapply force to the lever170, which biases the lever170to pivot in the counterclockwise direction as viewed inFIGS. 6-8and which corresponds to upward movement of the upper support frame115. The lever170is biased against the coupling nut160by the springs130a,130b. The coupling nut160inhibits movement of the lever170beyond a pre-determined angle within a range of angles.

As the angle of the lever170changes, the component of the force acting on the roller180and the torsion spring second ends140a,140bchanges for a given downward displacement of the upper support frame115. As with all torsion springs, the relevant component of the force is the normal force (e.g. the force that is perpendicular to the second ends140a,140bof the torsion springs130a,130b). As shown inFIG. 9, the roller180exerts a first force F1on the lever170. The first force F1has a horizontal component F1xas well as a vertical component F1y. The horizontal component F1xpresses the lever170against the coupling nut160. The relevant component is the vertical component F1ybecause the vertical component F1ybiases the upper support frame115away from the lower support frame110. The first force F1extends at a first angle with respect to vertical.

As shown inFIG. 10, the roller180exerts a second force F2on the lever170. The second force F2has a horizontal component F2xas well as a vertical component F2y. The horizontal component F2xpresses the lever170against the coupling nut160. The relevant component is the vertical component F2ybecause the vertical component F2ybiases the upper support frame115away from the lower support frame110. The second force F2extends at a second angle with respect to vertical. The second angle is less than the first angle. As the angle between the force of the roller180acting on the lever170approaches vertical, a greater component of the force acts in the vertical direction. Therefore, not only is the second force F2greater than the first force F1because of the increased loading of the torsion springs130a,130b, but the vertical component F2yis also a greater portion of the second force F2, because the angle between the second force F2and vertical is smaller than the angle between the first force F1and vertical.

FIGS. 11 and 12illustrate the lever170in the first end position (corresponding to the coupling nut160having fully traveled to one end of its range of motion), in which the bearing surface210is at an angle A1of about 70 degrees with respect to horizontal in the illustrated embodiment.FIG. 11illustrates the upper support frame115in a topped-out position in which the upper support frame115is spaced a maximum distance from the lower support frame110. When the lever170is in the first end position and the upper support frame115is in the topped-out position, the torsion spring ends140a,140bare positioned a first height H1above the lower support frame110and a first length L1from a rear portion of the lower support frame110. As the upper support frame115moves toward the lower support frame110into the bottomed-out position, the roller180rolls along the bearing surface210of the lever170into the position illustrated inFIG. 12. When the lever170is in the first end position and the upper support frame115is in the bottomed-out position, the torsion spring ends140a,140bare positioned at a second height H2above the lower support frame110and a second length L2from a rear portion of the lower support frame110. The second length L2is greater than the first length L1whereas the second height H2is less than the first height H1. As the roller180rolls along the lever170, the torsion springs130a,130bload up (increase in force), and resist further downward movement of the upper support frame115with respect to the lower support frame110.

FIGS. 13 and 14illustrate the lever170in the second end position (corresponding to the coupling nut160having fully traveled to an opposite end of its range of motion), in which the bearing surface210is at an angle A2of about 45 degrees with respect to horizontal in the illustrated embodiment.FIG. 13illustrates the upper support frame115in a topped-out position in which the upper support frame115is spaced a maximum distance from the lower support frame110. When the lever170is in the second end position and the upper support frame115is in the topped-out position, the torsion spring ends140a,140bare positioned a third height H3above the lower support frame110and a third length L3from a rear portion of the lower support frame110. As the upper support frame115moves toward the lower support frame110into the bottomed-out position, the roller180rolls along the bearing surface210of the lever170into the position illustrated inFIG. 14. When the lever170is in the second end position and the upper support frame115is in the bottomed-out position, the torsion spring ends140a,140bare positioned at a fourth height H4above the lower support frame110and a fourth length L4from a rear portion of the lower support frame110. The fourth length L4is greater than the third length L3whereas the fourth height H4is less than the third height H3. As the roller180rolls along the lever170, the torsion springs130a,130bload up (increase in force), and resist further downward movement of the upper support frame115with respect to the lower support frame110.

The difference between the first height H1and the second height H2is less than the difference between the third height H3and the fourth height H4. The forces F3and F4exerted on the lever170by the roller180are shown inFIGS. 12 and 14. The force F4inFIG. 14has a larger vertical component than the force F3inFIG. 12for two reasons. The first reason is that the force F4is oriented as a smaller angle with respect to vertical than the force F3. The second reason is that the torsion springs130a,130bhave been deflected over a greater angle inFIG. 14than inFIG. 12.

The stiffness of the suspension correlates to the force required to overcome the bias of the springs130a,130b. The greater the force that is required to overcome the bias of the springs130a,130b, the stiffer the suspension. Consequently, the suspension becomes stiffer as the relevant component of force increases and becomes softer as the relevant component of force decreases. A soft suspension (such as the suspension illustrated inFIGS. 11 and 12) results in the upper support frame115and bottom cushion70moving a first vertical distance in response to a weight being applied. A hard suspension (such as the suspension illustrated inFIGS. 13 and 14) results in the upper support frame115and bottom cushion70moving a second vertical distance, which is less than the first vertical distance, in response to the same weight being applied.

In order to adjust the stiffness of the suspension system, the user rotates the handle150to rotate the threaded shaft155, which moves the coupling nut160in a horizontal direction. As the coupling nut160moves in a horizontal direction, the coupling nut160causes rotation of the lever170to thereby change the angle of the lever170with respect to the horizontal. As the angle of the lever170changes, the degrees of deflection of the first and second ends135a,135b,140a,140bof the torsion springs130a,130bchanges, which changes the force the torsion springs130a,130bexert on the lever170. As the angle of the lever170changes, the portion of the force acting in the vertical direction (e.g., the vertical component of the force) changes. The vertical components of the forces F3, F4are the components which bias the upper support frame115away from the lower support frame110.

The angular deflection of the torsion spring second ends140a,140bdepends at least in part upon the angle at which a force is applied to the second ends140a,140bof the torsion springs130a,130b. As the angle at which the force is applied to the second ends140a,140bapproaches vertical, the relevant (vertical) component of the force is a greater portion of the force. The changing vertical component of force means that the degrees of rotation of the torsion spring second ends140a,140bper inch movement of the coupling nut160changes, as the lever170rotates. Specifically, when the lever170is in the first end position (shown inFIGS. 7,9,11and12), the degrees of rotation of the torsion spring second ends140a,140bper inch of movement of the coupling nut160is relatively low. When the lever170is in the second end position (shown inFIGS. 8,10,13and14), the degrees of rotation of the torsion spring second ends140a,140bper inch of movement of the coupling nut160is relatively high.

In operation, as the vehicle10travels over uneven ground, the upper support frame115is permitted to move with respect to the lower support frame110because the first and second suspension arms120a,120bare permitted to rotate with respect to the upper and lower support frames115,110, and the third and fourth suspension arms125a,125bare permitted to rotate and translation with respect to the upper and lower support frames115,110. The torsion springs130aand130bbias the upper support frame115away from the lower support frame110and the weight of the user biases the upper support frame115towards the lower support frame110.

Movement of the suspension is also affected by the actual weight of a given user sitting on the seat30. Regardless of the suspension setting, the resistance to downward movement increases as the seat30moves downward. Specifically, as the seat30moves downward, the torsion springs130a,130bload up (increase in force), resulting in greater resistance to further downward movement of the seat30to inhibit the seat30from bottoming out.

In some embodiments, the torsion springs130a,130bare not pre-loaded or are not substantially pre-loaded during adjustment of the coupling nut160when the upper support frame115is in the topped-out position. This permits a user to more easily adjust the stiffness of the seat suspension than was previously possible with other designs.

In some embodiments, the lever is adjustable by a user to pre-set “positions”. For example, the adjustment knob is omitted and the lever is able to be pinned into a soft, medium, or heavy ride setting without the ability to infinitely adjust the firmness of the ride.

In some embodiments, there is no adjustment and the springs bear against an angled top-plate that is preset to an “average” firmness setting.

In some embodiments, the profile of the lever allows for a non-linear suspension rate.