Wheel lifting device

Abstract

A wheel lifting device comprising a base structure with support means for being supported by a ground surface and a lifting frame with at least one wheel support member and a frame leg which extends upwardly at an angle to the ground surface. A link mechanism is connected to the base structure and to the lifting frame and a pivotal manoeuvring lever is connected to the link mechanism for lifting the lifting frame relative to the base structure. The blocking device for locking the manoeuvring lever at any desired pivotal position comprises a weight which is slidable along the frame leg and arranged to intersect the pivotal movement path of the manoeuvring lever and to be brought into frictional engagement with the frame leg when influenced by a force generated by the manoeuvring lever in order to block the lifting frame from downward movement relative to the base structure.

Claims

1. A wheel lifting device comprising: a base structure with support means for being supported by a ground surface; a lifting frame with at least one wheel support member and a frame leg which extends upwardly at an angle to the ground surface when the base structure is supported on the ground surface; a link mechanism connected to the base structure and to the lifting frame; a pivotal manoeuvring lever connected to the link mechanism for lifting the lifting frame relative to the base structure; and a blocking device for locking the manoeuvring lever at any desired pivotal position, characterized in that the blocking device comprises a weight which is slidable along the frame leg and arranged to intersect the pivotal movement path of the manoeuvring lever and to be brought into frictional engagement with the frame leg when influenced by a force generated by the manoeuvring lever in order to block the lifting frame from downward movement relative to the base structure.

2. A wheel lifting device according to claim 1, wherein the weight exhibits a recess which receives a longitudinal portion of the frame leg with a specific clearance.

3. A wheel lifting device according to claim 2, wherein the recess exhibits opposing edges, each having an extension x generally in parallel with a longitudinal direction of the frame leg; the manoeuvring lever is arranged to make contact with the weight at a first distance y from a centre line between the opposing edges; and wherein x<0.2y.

4. A wheel lifting device according to claim 3, wherein the weight has a centre of gravity which is positioned at a second distance z, from the centre line between the opposing edges, in the direction of first distance y; and wherein x>0.6z.

5. A wheel lifting device according to claim 4, wherein the centre of gravity is positioned at a third distance w from the centre line between the opposing edges in a direction which is perpendicular to the directions of extension x and first distance y; and wherein x>1.2w.

6. A wheel lifting device according to claim 2, wherein the weight and the frame leg are arranged to prevent rotation of the weight about the longitudinal axis of the frame leg.

7. A wheel lifting device according to claim 6, wherein the recess and the frame leg have corresponding form-locking cross sectional geometries.

8. A wheel lifting device according to claim 7, wherein the recess and the frame leg have corresponding polygonal cross sections.

9. A wheel lifting device according to claim 1, wherein the link mechanism comprises a lever shaft which is rotationally connected to the lifting frame and which exhibits two radially extending link levers which are rotationally connected to the base structure.

10. A wheel lifting device according to claim 9, wherein the link mechanism comprises two auxiliary link levers which are rotationally connected to the lifting frame and the base structure.

11. A wheel lifting device according to claim 9, wherein the manoeuvring lever is fixed to the lever shaft.

12. A wheel lifting device according to claim 1, wherein the base structure comprises two base rods which extend in parallel and are mutually connected by means of the link mechanism.

13. A wheel lifting device according to claim 1, wherein the lifting frame comprises two wheel support members extending in parallel.

14. A wheel lifting device according to claim 13, wherein the lifting frame comprises two frame legs each extending essentially perpendicular from a respective wheel support member and wherein the frame legs are mutually connected by a transverse handle rod.

15. A wheel lifting device according to claim 1, wherein the lifting frame is formed in one piece by bending a tubular blank.

16. A wheel lifting device according to claim 1, wherein each wheel support member is provided with a roller arranged to allow a wheel supported by the wheel support members to be rotated.

17. A wheel lifting device according to claim 7, wherein the recess and the frame leg have corresponding square cross sections.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is now described, by way of example, with reference to the accompanying drawings, in which:

(2) FIG. 1 is a perspective view illustrating a wheel lifting device according to an embodiment of the invention where the lifting frame is in a first lower position.

(3) FIG. 2 is a perspective view of the wheel lifting device in FIG. 1 where the lifting frame has been lifted to a second upper position.

(4) FIG. 3 is a perspective view of some parts, in enlarged scale, of the wheel lifting device in FIG. 1.

(5) FIG. 4 is a perspective view illustrating a frame leg and a blocking device comprised in the wheel lifting device shown in FIG. 1.

(6) FIGS. 5a-c, are schematic drawings illustrating the dimensions of and the forces acting on a blocking device of a wheel lifting device according to the invention. FIG. 5a illustrates blocking and FIGS. 5b-c illustrates release of the blocking device.

DETAILED DESCRIPTION

(7) The invention will now be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout the description. Throughout this specification, the terms vertical and horizontal refers to directions of the lifting device when positioned in an upright standing position such as illustrated in the figures.

(8) As shown in FIGS. 1-4, the wheel lifting device comprises a base structure 10 and a lifting frame 20 which is arranged to support a wheel (not shown) to be lifted into position at a vehicle. The lifting frame 20 comprises two wheel supporting members in the form of horizontal support legs 22a, 22b each of which extends essentially perpendicular from a first end of a respective frame leg in the form of vertical leg 24a, 24b. The vertical legs 24a, 24b are, at their second ends, mutually connected by means of a transvers handle rod 25. The support legs 22a, 22b are mutually connected by means of a transverse rod 27 which extends between respective front ends of the support legs, said front ends being distal to the junction with the frame legs 24a, 24b. Each support leg 22a, 22b is provided with a roller 26a, 26b which allows a wheel supported by the support legs to be rotated about its rotational centre axis for facilitating alignment of the wheel's fixation holes with corresponding fixations holes or bolts on the wheel hub of the vehicle. In the shown example, the rollers 26a, 26b are formed of cylindrical hollow sleeves which are rotationally threaded onto a respective support leg 22q, 22b. The support legs 22a, 22b, the frame legs 24a, 24b and the handle rod 25 are all formed of tubular rods. Hereby the frame 20 may readily be manufactured in one single piece by a few fast and cost effective bending operations of a tubular blank. In the shown example the frame 10 has been produced by bending a tubular blank having square cross section.

(9) The frame 20 is connected to the base structure 10 by means of a link mechanism 30 for allowing the frame 20 to be raised and lowered in relation to the base structure 20.

(10) The base structure 10 comprises at least two wheels 12 arranged to be supported by the ground floor. In the shown example the base structure 10 comprises four wheels 12. The wheels 12 allow the wheel lifting device to be correctly positioned in relation to the vehicle at which a wheel is to be shifted. In the shown example, the base structure 10 further comprises two parallel base rods 14a, 14b which are mutually connected by means of the link mechanism 30.

(11) In the shown example, the link mechanism 30 comprises a lever shaft 32 which, at its opposing ends, is rotationally connected to a respective support leg 22a, 22b of the frame 30. The lever shaft 32 comprises two radially extending link levers 34a, 34b, which are fixed to a respective end portion of the lever shaft 32. The link levers 34a, 34b are pivotally connected to a first end portion of a respective base rod 14a, 14b of the base structure 10. Two auxiliary link levers 36a, 36b are pivotally connected to respective second end portions of the base rods 14a, 14b and, by means of the transverse rod 27, to the support legs 22a, 22b of the frame. Rotation of the lever shaft 32 will thus cause the link levers 34a, 34b, 36a, 36b to pivot relative to the frame 20 and the base structure 10 and thereby to increase the vertical distance them between. During this vertical movement, the frame 20 and the base structure 10 will also move horizontally relative to each other. By keeping the frame 20 horizontally fixed, the wheels 12 allow the base structure 10 to move horizontally relative to the frame and the ground floor, thereby maintaining the horizontal position of the frame 20 and the wheel to be attached to the vehicle.

(12) The link mechanism 30 is operated by means of a manoeuvring lever 38, which in the shown example is fixed to the lever shaft 32. Pulling the manoeuvring lever 38 will cause the lever shaft 32 to rotate anti-clockwise as seen in the pictures, thereby raising the frame 20 relative to the base structure 10.

(13) The wheel lifting device further comprises a blocking device 40 which is arranged to counteract the gravity acting on the lifting frame 20 and maintain the frame 20 in any desired lifted position. As best seen in FIGS. 3 and 4, the blocking device 40 comprises a weight 42 which is slideably mounted to one 24a of the vertical legs of the frame 20. The vertical leg 24a is constituted by a tube having a square cross section and the weight 42 exhibits a U-shaped recess 44. The width of the recess 44 is somewhat wider than the width of the vertical leg's 24a cross section, such that the weight may slide up and down along the vertical leg 24a.

(14) The vertical leg 24a and the weight 42 are arranged such that a portion 46 of the weight, which portion 46 extends horizontally out from the vertical leg 24a, may intersect the pivotal movement path of the manoeuvring lever 38. When gravity acts on the lifting frame 20, the gravitational force will be transmitted via the link mechanism 30 to the manoeuvring lever 38, thereby urging the manoeuvring lever to rotate in the clockwise direction as seen in FIGS. 1 and 2. When making contact with the extended portion 46 of the weight 42, the manoeuvring lever 38 will exert an upwardly directed force F on the weight 42 as indicated in FIG. 5a. This force F will tilt the weight relative to the vertical leg 24a, such that opposing edges 44a, 44b of the U-shaped recess 44 make frictional contact with the vertical leg 24a. This friction prevents the weight 42 from being forced to slide upwardly along the vertical leg 24a, whereby the weight 42 blocks further clockwise rotation of the manoeuvring lever 38 and maintains the lifting frame 20 in the raised position in spite of the gravity acting on the lifting frame 20.

(15) In the example shown, the blocking device 40 further comprises a handle 47 which comprises a bolt 48 which is threaded into the weight such that the U-shaped recess is closed and the weight is prevented from coming loose from the vertical leg 24a.

(16) FIG. 1 illustrates the wheel lifting device in a lower starting position. The horizontal support legs 22a, 22b of the frame 20 rest against the base structure 10, whereby the manoeuvring lever 38 does not exert any appreciable force to the blocking device 40. The weight 42 of the blocking device 40 is influenced by gravity and rests on the manoeuvring lever 38. From this position, it is possible to raise the frame 20 by manually pulling the manoeuvring lever 38 as described above. Upon anti-clockwise rotation of the manoeuvring lever 38, the lifting frame is raised and the weight 42 simultaneously slides downwardly along the vertical leg 24a, thereby following the movement of the manoeuvring lever 38. When the lifting frame has reached the desired position, e.g. as shown in FIG. 2, it is possible to let go of the manoeuvring lever 38, whereby the blocking device 40, as described above, immediately will block the manoeuvring lever 38 from returning towards the starting position. For allowing the weight 42, under influence of the gravity, to automatically slide downwardly along the vertical leg 24a, this leg should be arranged at an sufficient great angle to the horizontal. In the shown example the vertical leg 24a is arranged approximately normal to the support plane defined by the four wheels 12. Satisfactory sliding of the weight can however be achieved also when the longitudinal direction of the vertical leg 24a deviates somewhat from the normal to the support plane. Typically, the vertical leg 24a should not deviate more than approx. 20 from the normal to the support plane.

(17) For returning the frame 20 and the manoeuvring lever 38 to the starting position shown in FIG. 1 it suffices to grip the handle 47 of the blocking device 40 and to manually slide the weight 42 upwardly along the vertical leg while keeping the weight 42 approximately non-tilted relative the vertical leg 24a, such that the friction between the edges of the U-shaped recess 44 and the vertical leg 24a is eliminated or reduced.

Example

(18) In the following and with reference to FIG. 5a, the conditions needed to be fulfilled for the blocking device 40 to prevent the lifting frame 20 from being lowered once the desired position has been reached and the manoeuvring lever 38 released is discussed. When the operator has raised the lifting frame 20 to the desired position and let go of the manoeuvring lever 30, the weight of the lifted wheel and the lifting frame 20 will influence the blocking device 40 by the force F. The vertical leg 24a having square cross section is received with a small clearance in the U-shaped recess 44 having opposing edges 44a, 44b. An edge pressure is thereby created between the blocking device 40 and the vertical leg 24a. The force A acting on the vertical leg is by reasons of equilibrium equal at both opposing sides of the vertical leg 24a. By friction between the blocking device 40 and the vertical leg, frictional forces A are created.

(19) The torque about centre axis M is:
Fy2Ax/2=0=>A=Fy/x
Where x is the extension of the edges 44a, 44b in the direction generally in parallel with the longitudinal direction of the vertical leg 24a and y is the distance between the point where the manoeuvring lever 46 makes contact with the weight 42 and the centre line between the edges 44a, 44b.

(20) The condition for reaching blocking of the blocking device is:
2A>F=>>F/(2A)=x/(2y)
Where is the coefficient of friction.

(21) If, for example, x=12 mm and y=60 mm this means that >0.1 results in that the blocking device is frictionally locked to the vertical leg. If the material of the blocking device and the vertical leg are chosen such that this condition is fulfilled the blocking device will be blocked in a satisfactory manner.

(22) In the following and with reference to FIGS. 5b and c, the conditions needed to be fulfilled for the blocking device 40 be released and allowed to slide along the vertical leg 24a will be discussed.

(23) When, from the blocked position, the operator pulls the manoeuvring lever 38 anti clockwise (as seen in FIGS. 1-3), the force F ceases to act on the blocking device. The blocking device 40 is thereafter influenced by its dead mass m with the force mg according to FIG. 5b. Also in this case an edge pressure B arises between the blocking device 40 and the vertical leg 24a. The distance between the centre of gravity CG of the blocking device and the centre point M is designated z.

(24) The torque about centre axis M is then:
2Bx/2mg=0=>B=mgz/x

(25) The condition for not reaching blocking of the blocking device and thus for allowing the blocking device to be displaced along the vertical leg is then:
2B<mg=><mg/(2B)=x/(2z)
If for example x=12 and z=10 this means that the condition for releasing the blocking device is <0.6.

(26) FIG. 5c is a section through the blocking device perpendicular to the direction of FIG. 5b. The circumstances are here somewhat different since the reactional forces act partly on the cylindrical portion of the bolt 48 and partly on the edge 44c of the recess 44.

(27) The torque about centre axis M is then:
2Cx/2mgw=0=>C=2mgw/x

(28) The condition for not reaching blocking of the blocking device and thus for allowing the blocking device to be displaced along the vertical leg is then:
2C<mg=><mg/(2C)=x/(4w)

(29) If for example x=12 mm and w=5 mm this means that the condition for releasing the blocking device is <0.6.

(30) The example shows that both the condition for frictional locking the blocking device 40 relative to the vertical leg 24a and for allowing displacement by releasing said frictional locking may be fulfilled if the geometrical dimensions of the blocking device 40 and the cross section of the vertical leg are chosen according to the principals described above and by choosing materials of the blocking device and the vertical leg which in combination fulfil the requirement on the coefficient of friction . In the shown example the coefficient of friction should lie within the interval:
0.1<<0.6

(31) This condition is fulfilled by many material combinations. It is for example possible to make both the blocking device 40 and the vertical leg 24a of steel and cover the contacting surfaces by many traditional industrial coatings.

(32) Now, starting from the above described conditions for accomplishing the desired blocking and release of the blocking device and from coefficients of friction of suitable constructional materials it is possible to determine preferred geometrical dimensions of the blocking device 40. Many constructional materials such as coated steel exhibit a coefficient of friction in the range of 0.1<<0.3.

(33) Applying the first condition for accomplishing blocking gives:
0.1>x/(2y)=>x<0.2y
Applying the conditions two for accomplishing release gives:
0.3<x/(2z)=>x>0.6z and
0.3<x/(4w)=>x>1.2w

(34) Above an exemplifying embodiment of the wheel lifting device according to the invention has been described. It is however readily understood that the invention is not limited to the above description and that the invention may be varied in numerous ways in accordance with the appended claims. For example the lifting frame may be formed in other ways than by bending a square tube blank, e.g. by bending tubes of other cross sectional geometries, such as other polygonal, oval or other non circular geometries. Even circular geometries may be used but at such instances other means should be provided for preventing the blocking device to rotate relative to the frame leg about the longitudinal axis of the frame leg. The frame may also be formed by other means than bending a tubular blank such as by welding, soldering or screw fixing together discrete components. Bending of a singular tubular blank is however preferred since it has proven to result in a very fast, simple and cost effective way of producing the frame. Instead of being formed of steel the frame and the blocking device may be constituted of or comprise other materials as long as the coefficient of friction and the geometries are chosen such that the above described conditions for accomplishing blocking and release of the blocking device are assured.