Midwheel drive wheelchair with independent front and rear suspension
View Patent ↗A wheelchair includes a frame, and a front pivot arm pivotally mounted to the frame at a front pivot point, the front pivot arm having a caster for supporting the frame. A rear pivot arm is pivotally mounted to the frame at a rear pivot point, the rear pivot arm having a caster for supporting the frame. A ground engaging mid-wheel drive wheel is connected to the frame. A linkage connects the front and rear pivot arms to each other in a manner such that an upward or downward rotation of one of the pivot arms about its pivot point causes rotation of the other pivot arm about its pivot point in an opposite rotational direction.
1. An electronically controlled midwheel drive wheelchair comprising:
a chair;
a frame for supporting the chair, the frame housing a battery between left and right frame side portions, with each frame side portion having a front arm frame mount fixed to the frame, a rear arm frame mount fixed to the frame, and a spring frame mount;
left and right drive wheels located along the respective frame side portions for supporting the frame and the chair, each drive wheel connected to a separate motor drive unit for propelling the wheelchair along a selected path; and
left and right linkage/suspension assemblies located along the respective frame side portions, each linkage/suspension assembly including:
a front arm defining a front arm pivot point and a front arm linkage mount, the front arm provided with a front caster defining a front caster rotational axis, the front arm pivot point connected to the front arm frame mount so as to pivotally attach the front arm to the respective frame side portion;
a rear arm defining a rear arm pivot point and a rear arm linkage mount, the rear arm provided with a rear caster for helping support the frame, the rear arm pivot point connected to the rear arm frame mount so as to pivotally attach the rear arm to the respective frame side portion;
a linkage coupling the front and rear arms together at the front and rear arm linkage mounts, the linkage operative such that rotation of one of the front or rear arms about its pivot point in one direction relative to the frame translates via the linkage to rotation of the other one of the front and rear arms about its pivot point in an opposite rotational direction relative to the frame; and
a single spring having one end connected to the spring frame mount and an opposite end connected to one of the front and rear pivot arms at a spring mounting point located between the respective caster and the respective frame pivot point, the single spring being operative to generate a biasing force on the one arm, wherein there is no spring connected between the frame and the other arm, and wherein the linkage is operative to transfer the biasing force from the one arm to the other arm such that the single spring is operative to affect movement of both the front and rear arms as the respective casters encounter surface irregularities during travel.
2. The wheelchair according to claim 1 wherein the drive wheel defines a drive wheel rotational axis and wherein, for each linkage/suspension assembly, both the front and rear arm pivot points are positioned below the drive wheel rotational axis.
3. The wheelchair according to claim 1 wherein the drive wheel defines a drive wheel rotational axis and wherein, for each linkage/suspension assembly, both the front and rear arm linkage mounts, and the linkage, are positioned below the drive wheel rotational axis.
4. The wheelchair according to claim 1 wherein an outer region of the drive wheel defines an envelope, and wherein at least one of the front and rear arm pivot points is positioned substantially within the envelope.
5. The wheelchair according to claim 4 wherein both of the front and rear pivot points are positioned substantially within the envelope.
6. The wheelchair according to claim 1 wherein at least one of the front and rear arms is formed of a vertically oriented plate.
7. The wheelchair according to claim 1 wherein, when the front caster encounters a raised obstacle during travel, a forward end of the front arm moves upwardly and the front arm rotates relative to the respective side frame in one direction, and the rear arm rotates relative to the respective side frame in the opposite direction.
8. The wheelchair according to claim 7 wherein, when the rear arm rotates relative to the respective side frame in the opposite direction, a rearward end of the rear arm moves upwardly to lift the rear caster off the ground.
9. The wheelchair according to claim 1 wherein each drive wheel defines a drive wheel rotational axis, and the drive wheel is directly mounted on its respective frame side portion such that the drive wheel rotational axis is fixed relative to the frame.
10. The wheelchair according to claim 1 wherein one of the front or rear arm linkage mounts is positioned between the respective caster and the respective arm pivot point, and wherein the linkage includes a link having ends pivotally connected to the front and rear arm linkage mounts.
11. The wheelchair according to claim 1 wherein the front and rear pivot points are each positioned between the respective caster and the respective arm linkage mount.
12. The wheelchair according to claim 1 wherein the linkage includes a slot and pin arrangement.
13. The wheelchair according to claim 1 wherein the linkage includes a flexible member.
14. An electronically controlled midwheel drive wheelchair comprising:
a chair;
a frame for supporting the chair, the frame housing a battery between left and right frame side portions, with each frame side portion having a front arm frame mount fixed to the frame, a rear arm frame mount fixed to the frame, and a spring frame mount;
left and right drive wheels located along the respective frame side portions for supporting the frame and the chair, each drive wheel connected to a separate motor drive unit for propelling the wheelchair along a selected path; and
left and right linkage/suspension assemblies located along the respective frame side portions, each linkage/suspension assembly including:
a front arm defining a front arm pivot point and a front arm linkage mount, the front arm provided with a front caster defining a front caster rotational axis, the front arm pivot point connected to the front arm frame mount so as to pivotally attach the front arm to the respective frame side portion, and wherein the front arm pivot point is located closer to the front arm linkage mount than it is to the front caster rotational axis;
a rear arm defining a rear arm pivot point and a rear arm linkage mount, the rear arm provided with a rear caster for helping support the frame, the rear arm pivot point connected to the rear arm frame mount so as to pivotally attach the rear arm to the respective frame side portion;
a linkage coupling the front and rear arms together at the front and rear arm linkage mounts, the linkage operative such that rotation of one of the front or rear arms about its pivot point in one direction relative to the frame translates via the linkage to rotation of the other one of the front and rear arms about its pivot point in an opposite rotational direction relative to the frame; and
a single spring having one end connected to the spring frame mount and an opposite end connected to one of the front and rear pivot arms at a spring mounting point located between the respective caster and the respective frame pivot point, the single spring being operative to generate a biasing force on the one arm, wherein there is no spring connected between the frame and the other arm, and wherein the linkage is operative to transfer the biasing force from the one arm to the other arm such that the single spring is operative to affect movement of both the front and rear arms as the respective casters encounter surface irregularities during travel.
15. An electronically controlled midwheel drive wheelchair comprising:
a chair;
a frame for supporting the chair, the frame housing a battery between left and right frame side portions, with each frame side portion having a front arm frame mount fixed to the frame, a rear arm frame mount fixed to the frame, and a spring frame mount;
left and right drive wheels located along the respective frame side portions for supporting the frame and the chair, each drive wheel defining a drive wheel rotational axis and connected to a separate motor drive unit for propelling the wheelchair along a selected path; and
left and right linkage/suspension assemblies located along the respective frame side portions, each linkage/suspension assembly including:
a front arm defining a front arm pivot point and a front arm linkage mount, the front arm provided with a front caster defining a front caster rotational axis, the front arm pivot point connected to the front arm frame mount so as to pivotally attach the front arm to the respective frame side portion, and wherein both the front arm pivot point and the front arm linkage mount are positioned below the drive wheel rotational axis;
a rear arm defining a rear arm pivot point and a rear arm linkage mount, the rear arm provided with a rear caster for helping support the frame, the rear arm pivot point connected to the rear arm frame mount so as to pivotally attach the rear arm to the respective frame side portion, and wherein both the rear arm pivot point and the rear arm linkage mount are positioned below the drive wheel rotational axis;
wherein an outer region of the drive wheel defines an envelope, and wherein at least one of the front and rear arm pivot points is positioned substantially within the envelope during the operation of the wheelchair;
a linkage coupling the front and rear arms together at the front and rear arm linkage mounts, the linkage positioned below the drive wheel rotational axis and operative such that rotation of one of the front or rear arms about its pivot point in one direction relative to the frame translates via the linkage to rotation of the other one of the front and rear arms about its pivot point in an opposite rotational direction relative to the frame; and
a single coil spring having one end connected to the spring frame mount and an opposite end connected to one of the front and rear pivot arms at a spring mounting point located between the respective caster and the respective frame pivot point, the single spring being operative to generate a biasing force on the one arm, wherein there is no coil spring connected between the frame and the other arm, and wherein the linkage is operative to transfer the biasing force from the one arm to the other arm such that the single spring is operative to affect movement of both the front and rear arms as the respective casters encounter surface irregularities during travel.
16. An electronically controlled midwheel drive wheelchair comprising:
a chair;
a frame for supporting the chair, the frame housing a battery between left and right frame side portions, with each frame side portion having a front arm frame mount fixed to the frame, and a rear arm frame mount fixed to the frame;
left and right drive wheels located along the respective frame side portions for supporting the frame and the chair, each drive wheel defining a drive wheel rotational axis and connected to a separate motor drive unit for propelling the wheelchair along a selected path; and
left and right linkage/suspension assemblies located along the respective frame side portions, each linkage/suspension assembly including:
a front arm defining a front arm pivot point and a front arm linkage mount, the front arm provided with a front caster defining a front caster rotational axis, the front arm pivot point connected to the front arm frame mount so as to pivotally attach the front arm to the respective frame side portion, and wherein both the front arm pivot point and the front arm linkage mount are positioned below the drive wheel rotational axis;
a rear arm defining a rear arm pivot point and a rear arm linkage mount, the rear arm provided with a rear caster for helping support the frame, the rear arm pivot point connected to the rear arm frame mount so as to pivotally attach the rear arm to the respective frame side portion, and wherein both the rear arm pivot point and the rear arm linkage mount are positioned below the drive wheel rotational axis;
wherein an outer region of the drive wheel defines an envelope, and wherein at least one of the front and rear arm pivot points is positioned substantially within the envelope during the operation of the wheelchair;
a linkage coupling the front and rear arms together at the front and rear arm linkage mounts, the linkage positioned below the drive wheel rotational axis and operative such that rotation of one of the front or rear arms about its pivot point in one direction relative to the frame translates via the linkage to rotation of the other one of the front and rear arms about its pivot point in an opposite rotational direction relative to the frame; and
a suspension spring for urging the front and rear arms to a neutral position.
17. The wheelchair according to claim 16 wherein the front arm pivot point is located closer to the front arm linkage mount than it is to the front caster rotational axis.
18. The wheelchair according to claim 17 wherein the frame includes a spring frame mount, and the spring has one end connected to the spring frame mount and an opposite end connected to one of the front and rear pivot arms at a spring mounting point located between the respective caster and the respective frame pivot point, the spring being operative to generate a biasing force on the one arm, wherein the linkage is operative to transfer the biasing force from the one arm to the other arm such that the spring is operative to affect movement of both the front and rear arms as the respective casters encounter surface irregularities during travel.
19. The wheelchair according to claim 18 wherein the spring is a single spring, wherein there is no spring connected between the frame and the other arm.
20. The wheelchair according to claim 19 wherein at least one of the front and rear arms is formed of a vertically oriented plate.