GB2266077A

GB2266077A - Suspension for hand-propelled vehicle.

Info

Publication number: GB2266077A
Application number: GB9207438A
Authority: GB
Inventors: Christopher James Mills
Original assignee: Individual
Current assignee: Individual
Priority date: 1992-04-03
Filing date: 1992-04-03
Publication date: 1993-10-20
Anticipated expiration: 2012-04-03
Also published as: GB9207438D0; GB2266077B

Abstract

The vehicle, such as a wheelchair, child's pushchair or buggy, comprises a chassis (22) and a suspension assembly mounted on the chassis. A support, such as a seat (25), for a load is mounted on the chassis, and a handle (28) is provided for manually propelling the vehicle. The suspension assembly comprises suspension arms (38, 39) pivotably mounted on the chassis and extending in forward and rearward directions in the region of opposite sides of the chassis. Each suspension arm has a wheel (42, 43) rotatably mounted at the free end thereof. Spring means (46) is disposed in the region of each side of the chassis and acts between the forwardly and rearwardly extending suspension arms in such a way that the free ends thereof tend to pivot towards each other. The suspension permits the load to travel smoothly over rough ground. <IMAGE>

Description

WHEELED CONVEYANCE The present invention relates to a wheeled conveyance such as a child's pushchair or buggy, a wheelchair or a stretcher. More particularly, the wheeled conveyance is adapted for being propelled manually.

Pushchairs and the like are well known, but are generally not provided with any effective form of suspension system and are generally not suited for use on rough ground.

There is an increasing awareness among people of the need to be fit and healthy, and more people are going on leisurely cross-country walks. Such walks, however, are difficult for parents with young children because it is tiring to carry them and pushchairs are generally incapable of travelling over gravel or sand or of providing a smooth ride for a child across an uneven surface frequently coming to a jarring stop.

It is an object of the present invention to provide a wheeled conveyance that incorporates a suspension system and which is more suited for use on rough ground.

According to the present invention there is provided a wheeled conveyance comprising a chassis and a suspension assembly mounted thereon, support means for a load mounted on the chassis, and handle means for manually propelling the conveyance, the suspension assembly comprising: suspension arms pivotably mounted on the chassis and extending in forward and rearward directions in the region of opposite sides of the chassis, each suspension arm having a wheel rotatably mounted at the free end thereof; and spring means disposed in the region of each side of the chassis and acting between the forwardly and rearwardly extending suspension arms in such a way that the free ends thereof tend to pivot towards each other.

The suspension arms may each incorporate a counter lever extending outwardly from the pivot point thereof. The spring means may extend between the counter levers of the suspension arms such that, in use, the spring means is maintained in a state of compression between the counter levers.

The forwardly extending suspension arms may be generally horizontal. The suspension arms may be inclined laterally outwardly of the chassis.

The suspension arms are preferably dimensioned such that the turning moment exerted on the spring means is substantially the same for the forwardly and the rearwardly extending suspension arms.

The suspension assembly may include stop means for limiting pivotal movement of the forwardly and/or rearwardly extending suspension arms. The stop means may be provided to limit upward movement of the rearwardly extending suspension arms. Alternatively, or additionally, the stop means may limit pivoting of the suspension arms towards one another. The stop means may be adjustable.

The support means for a load may comprise a seat. The seat may be adjustable forwardly and rearwardly relative to the chassis.

The chassis may comprise a frame that extends generally horizontally or which may be substantially upright.

The handle means may be adjustable. For example the handle may be pivotable relative to the chassis or may be extendible. Where the handle is pivotable relative to the chassis, the handle may be locked in any one of a predetermined angular positions by means of a manually operable locking pin.

For a better understanding of the present invention and to show more clearly how it may be carried into effect reference will now be made, by way of example, to the accompanying drawings in which: Figure 1 is a perspective view in diagrammatic form of the general arrangement of one embodiment of a wheeled conveyance according to the present invention in the form of a child's buggy; Figure 2 is a partial perspective view, on a larger scale, of the buggy shown in Figure 1 and shows the chassis arrangement of the buggy; Figure 3 is a side elevational view in diagrammatic form of the general arrangement of another embodiment of a wheeled conveyance according to the present invention in the form of a child's buggy;; Figure 4 is a front view, on a larger scale, of the buggy shown in Figure 3, with the seat removed for clarity, and Figure 5 is a rear view, on a larger scale, of the buggy shown in Figures 3 and 4.

Figures 1 and 2 show a wheeled conveyance according to the present invention, the conveyance being in the form of a child's buggy. As can best be seen from Figure 2, the buggy comprises a chassis 1 including a substantially square or rectangular frame 16 made, for example, from square section steel tube, and a suspension assembly 2 mounted on the chassis. Mounted on the chassis 1, by way of tubular elements 12, is a support means for a load in the form of a seat 13 which is adjustable, and even removable, by way of adjusting clips 14. A handle 15 extends from the chassis 1 for manually propelling the pushchair.

The suspension assembly includes two round shafts 3 extending transversely across the frame 16, one towards the front of the frame and the other towards the rear. Each shaft 3 carries two suspension arms 17 which include pivot elements 4 pivotably mounted on the shaft.

An arm 5 for carrying a wheel 6, shown in more detail in Figure 1, extends from each pivot element 4 from, and beyond in the case of a buggy, the frame 16 in a downwardly inclined direction, and a counter lever 7 extends upwardly from each pivot element 4 such that any up or down movement of a wheel 6 as a result of encountering an obstacle is translated through the suspension arm 17 into forward or backward movement of the counter lever 7. Thus, on each side of the chassis, one arm 5 extends forwardly and another arm 5 extends rearwardly.

As shown in Figure 1, the wheels 6 have a relatively large diameter as compared with the norm for a child's buggy in order to assist in overcoming any obstacles. Additionally, the wheels have a substantial width relative to the diameter thereof in order to reduce the risk of the wheels sinking in soft ground. The wheels 6 may be provided with relatively rigid or relatively soft tyres as desired.

The counter levers 7 on each side of the chassis are interconnected by spring means, such as spring 8 which is maintained under compression between the two levers 7.

Spring 8 has the effect that as the forward wheel on one side of the chassis encounters and rises over an obstacle, the forward arm 5 moves upwardly and forward counter lever 7 thus moves back. This forces spring 8 to be compressed, and the spring thus urges the rearward counter lever 7 to move back, the rearward arm 5 to drop and the rear wheel 6 to drop and to lift the rear of the chassis to substantially the same height as the front of the chassis.

If the rear wheels encounter an obstacle the actions of the suspension assembly work in reverse, causing the front wheel to drop and to lift the front of the chassis. Thus, the chassis always remains substantially level no matter what obstacles are encountered by the wheels.

As can be seen from Figure 2, stop means 9 is provided between the rearward counter levers 7 and the frame 16 of the chassis to limit upward movement of the rearward arms 5. I have found this is particularly useful when the buggy is mounting an exceptionally high obstacle beyond the means of the suspension to ride. In this situation it is conventional for a buggy to be tipped up so that the front wheels are lifted over the obstacle, the buggy then being pushed forward so that the rear wheels can subsequently be lifted over the obstacle. In the arrangement according to the present invention, if no stop means is provided, tipping the buggy so as to raise the front wheels is particularly difficult because the effect of the suspension assembly is to allow the chassis to rotate without lifting the front wheels.The stop means has the effect of limiting upward movement of the rearward arm 5 and thus permits the buggy to be tipped and the front wheels lifted once the stop means has engaged. Stop means 9, as shown in Figure 2, comprises an elongate element 10 that engages in the rearward counter lever 7 and passes through a ring 18 mounted on the rear of the frame 16, and an adjustable stop nut 11 threaded on to the end of the elongate element 10 on that side of the frame remote from the counter lever 7.

Figures 3, 4 and 5 show an alternative form of wheeled conveyance according to the present invention, again in the form of a child's buggy. The embodiment shown in Figures 3, 4 and 5 incorporates the same principles as the embodiment shown in Figures 1 and 2, but is more compact, rides rougher ground, including low kerbs, and is easier to manoeuvre.

The buggy shown in Figures 3, 4 and 5 comprises a chassis 21 including an upright rectangular frame 22 made from, for example, square section steel or aluminium tube, cast aluminium or plastics material, and a suspension assembly 23 mounted on the chassis. Mounted on the chassis 21, by way of laterally extending arms 20 and upright tubular elements 24, is a support means for a load in the form of a seat 25 which is adjustable for example by way of adjusting clips 26, and which can be removed, for example as illustrated in Figure 4. If desired, the seat can be adjustable forwards and backwards so as to maintain the centre of gravity of the load, such as a child, over the upright frame 22 in order to balance the load and the suspension.

As shown in Figures 3, 4 and 5, a handle 28 is mounted on the chassis 21 by way of laterally extending tubular arms 19. The angle of the handle 28 is adjustable by way of a part-circular plate 29 mounted at the end of each arm 28.

The handle is mounted in a pivotable manner at the end of each arm 28 and is provided with two retractable locking pins 30 which are engageable in apertures and/or slots 31 formed in each plate 29. The angle of the handle 28 is varied by operating a manually operable lever 32, for example mounted pivotably across the upper portion of the handle, so as to retract the locking pins 30 from the aperture and/or slot 31 by way of a cable 33. The handle 28 is then moved to its required position and the locking pins allowed to engage with the appropriate aperture and/or slot 31. Adjustment of the angle of the handle allows the user to compensate, for example, for varying slopes or even to swing the handle over the child's head to allow the child to be safely lowered backwards down or pulled up a steep slope or over difficult terrain.The upper part of the handle 28 is removable attached to the lower part, for example by way of a threaded stud and a removable knob 34.

As a further possibility (not shown), the handle 28 can be adjustable for length to make a more comfortable relationship to the user on varying slopes particularly when descending.

As with the embodiment of Figures 1 and 2, the suspension assembly includes two round shafts 35, 36 extending across the frame 22, in this case an upper shaft 35 arranged between the upper and lower cross members of the frame and a lower shaft 36 mounted on downwardly extending arms 37 protruding from the lower part of the frame. Each shaft 35, 36 carries two suspension arms, with suspension arms 38 extending forwardly from the lower shaft 36 and suspension arms 39 extending rearwardly and downwardly from the upper shaft 35. We have found that substantially horizontal forward suspension arms 38 give optimum performance in terms of permitting the buggy to mount obstacles.The upright frame 22 of the chassis of the buggy shown in Figures 3, 4 and 5 permits the forward suspension arms 38 to be positioned substantially horizontally as compared with the suspension arms of the buggy shown in Figures 1 and 2. To permit the frame 22 to have relatively small dimensions, while maintaining considerable stability for the buggy, the suspension arms 38, 39 are inclined laterally outwardly from the frame 22.

The suspension arms 38, 39 are mounted on the lower and upper shafts 36 and 35, respectively, by way of a tube 40 secured to each suspension arm and extending over the respective shaft. The tubes 40 are maintained in position along the shafts 35, 36 by engagement with the frame 22 and by means of a tubular spacer 41, which may be part of the tube 40, extending between the tubes 40 on each of the shafts 35 and 36. A wheel 42, 43 is mounted at the free end of each of the suspension arms 38, 39 respectively. As shown in Figure 3, the wheel 42 on the forwardly extending suspension arm 38 may have a larger diameter than the wheel 43 mounted on the rearwardly extending suspension arm 39.

The larger diameter wheel 42 at the front of the buggy assists the buggy in mounting relatively large obstacles, for example up to half the diameter of the wheel in height.

Due to the greater effectiveness of the trailing arm, the rear wheels do not require to be of the same diameter in order to provide the same obstacle climbing ability as the front wheels.

Extending substantially horizontally from each of the tubes 40 is a counter lever 44, 45. The counter levers 44 mounted on the lower suspension arms 38 being positioned so as to be beneath and to face the counter levers 45 mounted on the upper suspension arms 39. In practice, the counter levers 44 are mounted directly on, or can be formed integrally with, the lower suspension arms 38, while the counter levers 45 are mounted generally on the opposite sides of the tubes 40 to the upper suspension arms 39.

Thus any upward movement of any of the wheels 42, 43, for example as a result of encountering an obstacle, results in the respective counter levers 44, 45 being urged towards each other and any downward movement of any of the wheels 42, 43 results in the respective counter levers 44, 45 being urged away from each other. Because the suspension arms are independently pivotable on the shafts 35, 36, upward or downward movement of any of the wheels at one side of the buggy does not affect the suspension arms at the other side of the buggy.

The counter levers 44, 45 on each side of the buggy are interconnected by a coil spring 46 which is maintained under compression between the two counter levers 44, 45.

The initial degree of compression of the coil spring 46 is determined by a bolt 47 which extends axially through the spring 46 and which also serves to limit the relative movement of the counter levers 44, 45 away from each other.

Limitation of movement in this way facilitates tilting of the buggy for mounting an unusually high obstacle and/or for steering. Additionally, means can be provided for adjusting the free compression length of the springs 46 so as to adjust the suspension for different terrain. For example the free compression length can be reduced and the suspension rendered more firm for use in town or when the buggy is not in motion, and the free compression length can be extended and the suspension rendered less firm for use over rougher terrain.

Thus, similarly to the embodiment of Figures 1 and 2, if a front wheel 42 at one side of the buggy encounters and rises over an obstacle, the forwardly extending suspension arm moves upwardly and urges the counter lever 44 towards the counter lever 45. This compresses the coil spring 46 which in turn causes the counter lever 45 to move away from the counter lever 44,.thus causing the rearwardly extending suspension arm 39 to move downwardly and the rear wheel 43 also to move downwardly. Thus the child's seat may rock from side to side if an obstacle is encountered at only one side of the buggy, but does not tilt forwards and backwards1 resulting in a more comfortable ride for the child. If a rear wheel encounters an obstacle, the suspension assembly works in reverse, causing the front wheel to drop and to lift the front of the buggy.

Stop means 48 is mounted on a sub-frame 49 secured to the upper end of frame 22 in order to limit the upward movement of the rearwardly extending suspension arms 39. The stop means 48 is adjustable by the user and may be variable in a number of ways. For example, the stop means may be steplessly adjustable as illustrated in Figure 5, or may have a number, for example two, of predetermined settings such as for use in town or over difficult terrain.

Limiting the upward movement of the rearwardly extending suspension arms in this way facilitates tilting of the buggy such as to assist steering or surmounting large obstacles as described above in respect of Figures 1 and 2.

Conventionally, a suspension arrangement such as that described in connection with wheeled conveyance according to the present invention would require a damper, or shock absorber, in order to provide an acceptable ride. However, in practice the wheeled conveyance according to the present invention, whether it be a pushchair, wheelchair, wheeled stretcher or other conveyance is adapted to be propelled manually and surprisingly I have found that no additional damping is required because adequate damping is provided through the medium of the person or persons manually propelling the conveyance. Additionally, in practice the softness of the suspension permits the person holding the handle to limit the side-to-side rocking similarly to absorbing the shocks in the suspension.

I have found, however, that to obtain the best effect from a wheeled conveyance according to the present invention, the turning moment exerted on the suspension spring should be substantially the same for both the forwardly and the rearwardly directed suspension arms. In practice, because the counter levers are of substantially the same length, this is accomplished by arranging for the distance from the pivot point of each suspension arm to the point of contact with the ground to be substantially the same. The distance from the pivot point to the point of contact with the ground encompasses7 however, numerous design alternatives dependent upon the size of the wheel and the length of the suspension arm, the larger the wheel, the shorter the suspension arm.Surprisingly, I have found that the wheeled conveyance according to the present invention performs best when an obstacle is approached with some determination. Contrary to the performance of conventional buggies, which would stop on encountering an obstacle of any significance, a buggy made in accordance with the present invention rides up and surmounts the obstacle, with the wheels and the suspension absorbing the impact.

Clearly there is substantial opportunity for adapting the form of the wheeled conveyance according to the present invention from those described with reference to the drawings without departing from the scope of the present invention. For example, alternative materials could be used such as plastics or other metals. Other possibilities include incorporating a folding mechanism into the conveyance and introducing means to assist turning the conveyance. It is also possible to replace the frame that forms part of the chassis as described in the embodiments described with reference to the drawings with a single cross member, the shafts being mounted directly or, more likely indirectly, on the cross member and carrying the suspension arms and the counter levers and the like.

Claims

1. A wheeled conveyance comprising a chassis and a suspension assembly mounted thereon, support means for a load mounted on the chassis, and handle means for manually propelling the conveyance, the suspension assembly comprising: suspension arms pivotably mounted on the chassis and extending in forward and rearward directions in the region of opposite sides of the chassis, each suspension arm having a wheel rotatably mounted at the free end thereof; and spring means disposed in the region of each side of the chassis and acting between the forwardly and rearwardly extending suspension arms in such a way that the free ends thereof tend to pivot towards each other.

2. A wheeled conveyance as claimed in claim 1, wherein the suspension arms each incorporate a counter lever extending outwardly from the pivot point thereof.

3. A wheeled conveyance as claimed in claim 2, wherein the counter lever of at least one of the forwardly and rearwardly extending suspension arms comprises a portion of the suspension arm between the pivot point and the free end thereof.

4. A wheeled conveyance as claimed in claim 2 or 3, wherein the spring means extend between the counter levers of the suspension arms such that, in use, the spring means is maintained in a state of compression between the counter levers.

5. A wheeled conveyance as claimed in any preceding claim, wherein the forwardly extending suspension arms are generally horizontal.

6. A wheeled conveyance as claimed in any preceding claim, wherein the suspension arms are inclined laterally outwardly of the chassis.

7. A wheeled conveyance as claimed in any preceding claim, wherein the suspension arms are dimensioned such that the turning moment exerted on the spring means is substantially the same for the forwardly and the rearwardly extending suspension arms.

8. A wheeled conveyance as claimed in any preceding claim, wherein the suspension assembly includes stop means for limiting pivotal movement of the forwardly and/or rearwardly extending suspension arms.

9. A wheeled conveyance as claimed in claim 8, wherein the stop means is provided to limit upward movement of the rearwardly extending suspension arms.

10. A wheeled conveyance as claimed in claim 8 or 9, wherein the stop means limits pivoting of the suspension arms towards one another.

11. A wheeled conveyance as claimed in any one of claims 8, 9 or 10, wherein the stop means is adjustable.

12. A wheeled conveyance as claimed in any preceding claim, wherein the support means for a load comprises a seat.

13. A wheeled conveyance as claimed in claim 12, wherein the seat is adjustable forwardly and rearwardly relative to the chassis.

14. A wheeled conveyance as claimed in any preceding claim, wherein the chassis comprises a frame that extends generally horizontally.

15. A wheeled conveyance as claimed in any one of claims 1 to 13, wherein the chassis comprises a frame that is substantially upright.

16. A wheeled conveyance as claimed in any preceding claim, wherein the handle means is adjustable.

17. A wheeled conveyance as claimed in claim 16, wherein the handle is pivotable relative to the chassis.

18. A wheeled conveyance as claimed in claim 17, wherein the handle can be locked in any one of a predetermined angular positions by means of a manually operable locking pin.

19. A wheeled conveyance as claimed in claim 16, 17 or 18, wherein the handle is extendible.

20. A wheeled conveyance substantially as hereinbefore described with reference to, and as shown in, Figures 1 and 2 or Figures 3 to 5 of the accompanying drawings.