Wheel with suspension system and centralizing unit with suspension system

Abstract

A wheel with a suspension system being connectable to a vehicle, like a wheel chair, comprises a hub (38) and a rim (34) rotatable about the axle (42) of the hub (38). Between the hub (38) and the rim (34), a number of support members (40) is located. The support members (40) are adapted to retain the distance when stressed up to a threshold value and recoverly alter the distanced when stressed over this threshold value. According to the invention, the support members (40) are comprising spring elements (50), damping strokes by compression if the support member (40) is compressed or elongated. The spring elements (50) are preferably preloaded.

Claims

1. A centralizing unit comprising a suspension system with at least one support member comprising: an outer longitudinal element enclosing a lumen, comprising a first outer slit and a second outer slit longitudinally spaced from said first outer slit along an outer slit longitudinal axis; an inner longitudinal element slidable in said lumen, comprising a first inner slit and a second inner slit longitudinally spaced from said first inner slit along an inner slit longitudinal axis, said inner and outer longitudinal elements are slidably movable relative to each other in a longitudinal direction within said lumen; a first sliding pin provided in said first outer slit and said first inner slit; a second sliding pin provided in said second outer slit and said second inner slit; and a suspension spring connected with a first end to said first sliding pin and with a second end to said second sliding pin; wherein said inner and outer longitudinal elements are configured whereby when subjected to compression or extension stresses less than a predetermined threshold value, said first and second sliding pins maintain a fixed distance relative to each other.

2. The centralizing unit of claim 1, wherein said slits are sized and arranged wherein at a central relative position between said outer longitudinal element and said inner longitudinal element, said first sliding pin and said second sliding pin are pushed by said suspension spring to a maximal distance.

3. The centralizing unit of claim 2, wherein, when said first sliding pin and said second sliding pin are at said maximal distance, said suspension spring is at a nominal length being smaller than a non-stressed length of said suspension spring.

4. The centralizing unit of claim 1, wherein at any non-central relative position between said outer longitudinal element and said inner longitudinal element, said first sliding pin and said second sliding pin are forced to approach each other to a distance smaller than said maximal distance, thereby compressing said suspension spring between said first sliding pin and said second sliding pin.

5. The centralizing unit of claim 1, comprising a central member connected at a first portion to a first of said at least one support member, and at an evenly displaced second portion to a second of said at least one support member substantially identical to said first support member.

6. The centralizing unit of claim 5, wherein, when said central member is loaded to a magnitude greater than a predetermined threshold value, said first support member elongates and said second support member compresses, whereby both of a first spring element of said first support member and a second spring element of said second support member compress with a cumulative compression force resisting said loaded magnitude of said central member.

7. The centralizing unit of claim 6, wherein, when said central member is loaded to a magnitude less than said predetermined threshold value, said first and second support members support a fixed distance between said central member and said first and second support members.

8. The centralizing unit of claim 6, wherein, when said central member is loaded to a magnitude less than a predetermined threshold value, said inner and outer longitudinal elements are configured to support a fixed distance between said central member and said support member.

9. The centralizing unit of claim 1, wherein said suspension spring dissipates kinetic energy at least partly upon compression of said suspension spring.

10. The centralizing unit of claim 1, configured to dissipate kinetic energy at least partly upon compression of said first spring element and of said second spring element.

11. The centralizing unit of claim 1, wherein said first sliding pin passes through said first inner and outer slits, and said second sliding pin passes through said second inner and outer slits, during said relative slidable movement of said inner and outer longitudinal elements.

12. The centralizing unit of claim 1, wherein said inner and outer longitudinal elements are configured whereby when subjected to compression or extension stresses over a predetermined threshold value, said first and second sliding pins move towards each other, thereby compressing said suspension spring.

13. The centralizing unit of claim 12, wherein said suspension spring stores mechanical energy at compression, and is provided preloaded to a predetermined threshold value, thereby compresses only in response to compressive force greater than said threshold value.

14. The centralizing unit of claim 1, wherein said suspension system is provided in a wheel including a hub and a rim, and being connectable to a vehicle, wherein said at least one support member is positioned between said hub and said rim, thereby providing a normally fixed distance between said hub and said rim.

15. The centralizing unit of claim 14, wherein said at least one support member is connected in a non-radial manner to said hub.

16. The centralizing unit of claim 14, wherein said support member is adapted to retain said distance when stressed up to a threshold value and to recoverably alter said distance when stressed over said threshold value.

17. The centralizing unit of claim 16, wherein said threshold value relates to a minimal shock magnitude absorbed by said wheel.

18. The centralizing unit of claim 16, wherein said threshold value relates to a minimal vibration amplitude absorbed by said wheel.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Hereinafter, preferred embodiments of the invention are described, referring to the drawings.

(2) FIGS. 1A-B schematically illustrate side views of a wheelchair and a wheel anticipating different obstacles during motion, in accordance with embodiments of the present invention,

(3) FIGS. 2A-C illustrate an exemplary wheel comprising a plurality of spoke type selective suspension members in accordance with a first preferred embodiment of the invention,

(4) FIG. 3 illustrates a perspective view of a second embodiment of the invention,

(5) FIGS. 4A-C are showing side views of the spring element used within the wheel shown in FIG. 3 in different damping situations, and

(6) FIGS. 5A-C are showing diagrams of bilateral spring mechanisms.

DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

(7) The following preferred embodiments may be described in the context of exemplary suspension mechanisms for wheelchairs, or other types of self-propelled vehicles, for ease of description and understanding. However, the invention is not limited to the specifically described devices, and may be adapted to various applications without departing from the overall scope of the invention. For example, devices including concepts described herein may be used for suspension of any rotatable mass including wheels of motorized or otherwise powered vehicles.

(8) Common suspension systems are built to absorb interruptions and obstacles which cause deceleration and/or undesired vibration to the vehicle and/or aid the wheel in following the terrain and avoiding loss of contact with it, or grip. In doing so, the suspension systems are built to absorb and/or dissipate energy, including such that can be translated to effective kinetic energy. Furthermore, the common suspension systems (which include, for example, parts like metal springs, cushioning materials and elastomers) cause a feeling of plushness, or softness, which may cause a sense of instability, which are undesirable by many users.

(9) In order to answer these and other considerations, the present invention provides or includes means for selective responsiveness (or irresponsiveness) according to types and/or magnitudes of absorbed interferences or perturbations.

(10) Referring now to the drawings, FIGS. 1A-B schematically illustrate side views of a wheelchair 10 and a rear wheel 11 anticipating different obstacles during motion, in accordance with embodiments of the present invention. Besides combining two rear wheels such as wheel 11, wheelchair 10 further includes a seat 12 and a pair of casters 13. In FIG. 1A, wheelchair 10 moves along path 20 which includes a step or a curb descent 21 with height x, as well as a plurality of recesses 22, such as tile gaps or chamfers on paved surfaces. Height x may be about 10 cm or more in case of a sidewalk curb, or 15 cm or more in case of a standard stairway step. Recesses 22, on the other hand, are of heights of less than 3 cm, usually around 1 cm. In some embodiments, the suspension system of the present invention includes means for selective differentiation between drops from different heights, for example drops from up to 1 cm, optionally up to 3 cm and those which are equal or higher than 1 cm, optionally 3 cm, optionally 5 cm, or higher, or lower or intermediate. Also, a selective differentiation may be applicable for a range of drops or perturbations, such as over 3 cm and under 10 cm, for example.

(11) Wheelchair 10 is shown in motion adjacent a forward-facing step 21 with its front end is tilted upwardly (commonly known as performing a wheelie), pivoting around rear wheel(s) 11a common practice when riding over steps, performed either by an attendant or by the wheelchair user himself. The tilting angle may be between 0 to 40, and optionally higher. Such tilting maneuver changes the impact angle of the wheelchair with the ground and should be considered when designing an effective suspension mechanism. In some embodiments, the suspension system of the present invention is configured for effective suspension of falls at different impact angles, optionally in angles range of at least 10 to 10, optionally 30 to 30, optionally 60 to 60. Also, in some cases the drop can be taken in reverse, meaning that the rear wheels go first, while the front casters are still on the top platform, generating a mild nose up angle of generally less than 20, but optionally higher.

(12) FIG. 1B shows a second demonstrative scenario in which wheel 11 (shown independently for ease of demonstration only) travels along path 30 that includes a bump 31 of a significant height followed by a substantially shallow coarse road 32. In some embodiments, the suspension system of the present invention includes means for selectively differentiating between bumps of different heights, and for example may allow suspension of bumps of 0.5 cm or higher, optionally 1 cm or higher, optionally 3 cm or higher. Alternatively or additionally, such or other means may allow suspension of bumps shorter in height than wheel radius, optionally shorter than its radius, optionally shorter than its radius. Alternatively or additionally, such or other means may differentiate between road types (such as between coarse roads like road 32) which cause vehicle's and/or wheel's vibrations differentiated by acceleration impact amplitude and/or frequency, optionally depending also on vehicle's velocity. In some such embodiments, the suspension selectivity is also based on a defined allowed load (e.g., combined weight of wheelchair and user) or on a defined allowed range of loads, so that only if such a condition is met, the suspension system can correctly differentiate between such predetermined fall heights. For example, a suspension system according to the present disclosure can be provided in two rear wheels of a wheelchair, and provided and preset such, that if a combined weight of the wheelchair and a wheelchair user is, for example, between 40 Kg to 120 Kg, or optionally between 50 Kg to 100 Kg, or optionally between 60 Kg to 80 Kg, or optionally about 70 Kg, or higher or lower or an intermediate value, then the suspension system will not operate at shocks originating from falls of 40 mm or less, optionally 20 mm or less, optionally 10 mm or less, optionally 5 mm or less, optionally 2.5 mm or less, in height, or higher or lower or an intermediate value.

(13) Reference is now made to FIGS. 2A-C which illustrate an exemplary wheel 700 comprising a plurality of spokes type selective suspension members 740 (or 760), with a first embodiment of the present invention. Wheel 700 includes a rim 710 wearing a tire 720, a hub 730 and the plurality of members 740 that are symmetrically and evenly distributed and connecting between rim 710 and hub 730. In some embodiments, members 740 support a fixed distance, under a compressive forces of less than a threshold magnitude, between hub 730 and contact regions (e.g., flanges 715) at rim 710. Optionally, members 740 do not maintain or only partially support circularity of rim 710, and therefore the latter is optionally provided strengthen with respect to previously shown rims. In some embodiments, hub 730 includes a center rounded portion 736 having a bore 738 passing therethrough and housing a bearing (not shown) mountable to a chassis (e.g., of a wheelchair) using an axle. Three outwardly radial extensions 734 originate from hub center 736; each radial extension 734 ends with an angularly extended head 732; each angularly extended head 732 includes two lateral sides; wherein each lateral side is hingedly connected to an inward connection portion 742 of a member 740. Member 740 includes an outward connection portion 746 which is hingedly connected to rim 710 at flange 715. Each member 740 includes a piston 741 slidably movable in a cylindrical housing 745. Both piston 741 and housing 745 includes linear slots (744 and 748, respectively) provided along and in parallel to their longitudinal axes, and each include a movable pin (743 and 747, respectively) that is slidably movable in a corresponding slot (pin 743 in slot 748 and pin 747 in slot 744). A preloaded compression spring 750 is provided connected in-between pin 743 and 747. Spring 750, when fully relaxed or compressed under a predetermined threshold value (according to preloading), maintains pins 743 and 747 at a normally fixed distance. When piston 741 and housing 745 are subject to compression or extension stresses that are over the predetermined threshold value, the pins ultimately move one towards the other thereby compressing spring 750. A damping member (not shown) may also be provided and configured to act in parallel to contraction motions of spring 750. Member 760 is an alternative design that can replace member 740, and while preserving similar qualities, it is based on gas spring 770 instead of coil spring 750. Similarly, when member 760 elongates or shortens at stresses exceeding the threshold value, gas spring 770 will be forced to compress. In some embodiments, gas spring 770 includes damping capabilities, as known in the art.

(14) Within FIGS. 3 and 4A-C, a second preferred embodiment of a wheel connectable to a vehicle, particularly to a wheel chair, is shown. Wheel 10 comprises a rim 34 carrying a tire 36. The rim 34 is connected to a hub 38 by three supporting members 40. An axle 42 is shown provided in hub 38, being in this embodiment surrounded by bearing 44. The inner ring of the bearing 44 is fixed to the axle 42 and the outer ring of the bearing 44 is fixed to a connecting member 46 having three arms 48. The arms 48 are particularly arranged radially to the axle 42. The support members 40 are connected to the outer end portions of the arms 48 so that the support members 40 are not arranged in a radial manner in the wheel.

(15) To damp a stroke or the like, the length of the support members 40 vary damping the stroke.

(16) Within the drawings 4A-C, the support members 40 are shown in different damping situations.

(17) In a regular, normal situation (i.e., hub 38 in concentric with rim 34), each of the support members 40 centralized and are not compressed or elongated, and a spring 50 provided therein is substantially preloaded (e.g., it is held compressed to a length being substantially smaller than its non-stressed length).

(18) The support members comprise two longitudinal elements 52 and 54, whereby the cylindrical element 54 surrounds the inner cylindrical element 52. Therefore, it is possible to move the two longitudinal elements 52, 54, relative to each other in a longitudinal direction 56. Within the inner longitudinal element 52, the damper 50 is located. The spring 50 comprises a piston 58, being located within a cylinder 60. The cylinder 60 is, for example, filled with compressed gas or oil. Spring 50 is preloaded since at nominal position, the pins 62 are distanced such that the spring is already compressed to the threshold value. Only above the threshold it can be further compressed. The end portions of the spring 50, i. e. of the cylinder 60 and the rod 58, are each connected to a pin-like tracked sliding element 62. The pin-like tracked sliding elements are passing through slits 64 of the inner longitudinal element 52 and slits 66 of the outer longitudinal element 54. Due to the slits 64 and 66, a movement of the two longitudinal elements 52, 54 in longitudinal direction 56 is possible. Slits length provide boundaries to such relative motion, above which pins 62 are forced to move.

(19) As shown in FIG. 4B, combined acting forces F and F compress support member 40. The force actuates and compresses spring 50, due to the fact that rod 58 is pressed into the cylinder 60 compressing the air in the cylinder 60. Optionally and additionally, spring 50 acts as a damper so that some of the kinetic energy invested by the force work is dissipated and the stroke is absorbed. Additionally, the left tracked sliding element 62 is moved within left slits 64, 66. The right tracked sliding element 62 remains in place.

(20) In some embodiments, when at least one support member in a self-suspended wheel or in a centralizing unit according to the present invention, there is at least a second support member being elongated, optionally at same extent, optionally to a different extent. In some such embodiments, springs and/or damper installed in both support members shall compress during the first support member compression and the second support member elongation, such that both springs and/or dampers contribute to the overall mechanical energy storage and/or damping, respectively. Reference is now made to FIG. 4C, showing that the support member 40 is now elongated by a force F. According to the invention, the spring 50 is compressed, i. e. the rod 58 is, for example, compressing gas provided in the cylinder 60, even if the support member 40 is elongated. This is possible due to the fact that in this case, the left tracked sliding element 62 is held in place compared to the normal position (FIG. 4A), whereby the right tracked sliding element 62 is moved to the left in FIG. 4C. This movement is possible since the right tracked sliding element 62 can be moved to the left inside the slit 66 of the outer longitudinal element 54, whereby this movement is caused by moving the inner longitudinal element 52 to the left in FIG. 4C.

(21) A centralizing unit according to the invention may comprise a central member 48 being connected to three support members 40, whereby the central member 38 does not necessarily have to be connected to a hub and the support members 40 do not necessarily have to be connected to the rim (see, for example, FIG. 3).

(22) The principle mechanism background of a bilateral spring mechanism is hereinafter described in view of FIGS. 5A-5C.

(23) Virtually, an infinite spring, such as a coil spring, that adheres to the linear rule of elasticity, would demonstrate substantially the same ratio between elongation to required force as it would between compression to required force (often referred to as k, or spring constant).

(24) Therefore, if such a spring is allowed to work both as a pulling spring and as a compression spring, its behavior as depicted in the graph of FIG. 5A.

(25) In most suspension systems the spring is installed with some portion of compression preload, in order to prevent the spring to be free at any point, hence diminishing unwanted movement of the spring while not under compression forces (see graph of FIG. 5B).

(26) As a preloaded spring is inherently stressed in one direction (e.g., compressed), if it is prone also to shift to the opposite direction (e.g., extend) then the preloading function will not be efficient.

(27) Therefore, while compressing the system for a certain travel (e.g., 2 cm) would require a certain amount of force, elongating the system by the same travel would require less force.

(28) The disclosures provided herein allow bilateral suspension or centralizing unit and obviate the need for two such mechanisms (or sub-systems) to be installed in opposite directions, in order to for a mirrored image of the graph shown in FIG. 5B.

(29) When a symmetrical preloaded springing system is implemented, both compression and elongation produce the same forces, in their respective direction, while allowing preloading function in both directions, as shown in FIG. 5C.

(30) Such a mirrored springing system enables several benefits that are impossible with one-directional springs, like a bi-directional threshold and symmetrical suspension response using a single sprung element while other applications that deals with cyclic or periodic perturbations must use two systems installed in opposite directions.

(31) The principal of a bi-directional threshold can be described as preventing motion in any direction, as long as force above a certain magnitude, like F.sub.min, is not exerted on the system. In this setup, any force, in any direction, that is lower than F.sub.min will not derive any movement of the spring, and only forces higher than F.sub.min will cause the spring to travel at k ratio, in either direction (without any special push/pull connection).