CA1199154A - Controllable swivel wheel - Google Patents
Controllable swivel wheelInfo
- Publication number
- CA1199154A CA1199154A CA000464237A CA464237A CA1199154A CA 1199154 A CA1199154 A CA 1199154A CA 000464237 A CA000464237 A CA 000464237A CA 464237 A CA464237 A CA 464237A CA 1199154 A CA1199154 A CA 1199154A
- Authority
- CA
- Canada
- Prior art keywords
- wheel
- axle
- swivel
- cart
- pivot
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60B—VEHICLE WHEELS; CASTORS; AXLES FOR WHEELS OR CASTORS; INCREASING WHEEL ADHESION
- B60B33/00—Castors in general; Anti-clogging castors
- B60B33/04—Castors in general; Anti-clogging castors adjustable, e.g. in height; linearly shifting castors
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Handcart (AREA)
Abstract
ABSTRACT
On a cart which is guided by a person not riding on it, it is common for the cart to be on two pairs of wheels, one pair of them on a fixed axle, and each wheel of the other pair on a short axle which swivels about a pivot, the axis of which is vertical and not on a line which intersects the axis of the wheel axle, and the bearing of which is fixed to the cart body.
For carts which have to be guided with precision in both forward and reverse directions, such as lawnmowers, the usual swivel wheel is unsuitable because when the cart changes direction between forward and reverse the swivel wheels swivel through half a revolution, which causes difficulties when the lawnmower is alongside an obstacle such as a fence. It is necessary, in in any kind of swivel wheel for the vertical pivot to lead the wheel axle as the cart is moving, which means that the relative positions of the axle and pivot must be reversed as the cart changes between forward and reverse. In this invention the vertical pivot is allowed to slide along a guideway which depends from the wheel axle, in order to acheive the above mentioned reversal of positions. In the invention there is also a spring clutch arrangement which prevents the swivel wheel from rotating on its axle while the pivot is changing positions. Furthermore, each of the pair of swivel wheels may be linked to the other so that both always swivel by the same amount.
On a cart which is guided by a person not riding on it, it is common for the cart to be on two pairs of wheels, one pair of them on a fixed axle, and each wheel of the other pair on a short axle which swivels about a pivot, the axis of which is vertical and not on a line which intersects the axis of the wheel axle, and the bearing of which is fixed to the cart body.
For carts which have to be guided with precision in both forward and reverse directions, such as lawnmowers, the usual swivel wheel is unsuitable because when the cart changes direction between forward and reverse the swivel wheels swivel through half a revolution, which causes difficulties when the lawnmower is alongside an obstacle such as a fence. It is necessary, in in any kind of swivel wheel for the vertical pivot to lead the wheel axle as the cart is moving, which means that the relative positions of the axle and pivot must be reversed as the cart changes between forward and reverse. In this invention the vertical pivot is allowed to slide along a guideway which depends from the wheel axle, in order to acheive the above mentioned reversal of positions. In the invention there is also a spring clutch arrangement which prevents the swivel wheel from rotating on its axle while the pivot is changing positions. Furthermore, each of the pair of swivel wheels may be linked to the other so that both always swivel by the same amount.
Description
s~
SPECIFICATION
This invention relates to a swivel caster or wheel.
It is known for a cart which is guided by a person not riding on it to ha~e a pair of f-xed wheels and a pair of swivel wheels. The fixed wheels are on a horizontal axle which is fixed to the cart and unable to move relative to it. Each swivel wheel is on a short hori~ontal axle which swivels about a pivot having a vertical axis. This vertical axis is on the vertical plane which is parallel to the wheel face and which bisects the wheel tire. Also, the axis of the pivot is on a line which does not intersect the axis of the wheel axle,the horizontal distance between the two axes being the radius of swivel of the wheel axle~ The bearing of the pi~ot is fixed to the cart body, and the rotating part of the pivot is fixed to the wheel axle by means of a bracket. Whith this arrangement the wheels swivel when the operating person applies a sideways force to the Gart.
~owever, to enable the cart to be steered ~y these swivel wheels the swivelling axles must follow the vertical pivots, ta~ing their path, while the cart is moving, which is in any case their natural tendency. This means that when the cart is moving between forward and reverse directions the swivel wheels swivel through half a revolution so that the axle of each swivel wheel can assume a following position relative to that o~ its pivot as the cart moves along in its new direction. Furthermore, if an attempt is made to guide the cart so that it exactly re-traces its origi-nal path while changing direction, each swivel wheel will swivel half a turn in a random direction, that is, either clockwise or counter clockwise, and at an unpredictab~e ins~ant~ shortly after the c~ange in direction between forward and reverse. Therefore, swi~el wheels o~ this type are unsatisfactory for some types of cart, such as lawnmowers, over whose steering full control must be kept by the operating person during c~anOes of d~rection between forward and reverse, when the cart is required to exactly 5~
re-trace its path because, during its swivel through half a turn, one of the wheels would possi~ly collide wit~ a fe~ce or fall over the lawn ed~e into a flower bed.
I have found -that these disadvantages may be overcome ~J
placing the vertlcal pivot in a horizontal slideway which can be situated withln the wheel rim envelope, is parallel to t~e face of the wheel,and is supported, through bearings, by the wheel axleO This arrangement permits the vertical pivot to travel in a horizontal line ~etween two positions, each a~ equal dist-ance from the wheel axle. The bearing of the vertical pivot isfixed to the cart, and the rotating member of the pivot i~ ~ixed to a slider which can travelin the slideway. When the cart is moving forward, the vertical pivot will be in its ~orward pos-ition, that is, forward of, and leading, the wheel axle. '~hen the cart changes to a reverse direction the pivot will travel along the slideway to its aft position, that is, aft of, and leading, the wheel axle. 3ecause the vertical pivot bearings are fixed to the cart, when the pivot moves alon~ the slideway the body o~ the cart and the two fixed a~le wheels move the same distance as the pivot. The relative movement between the vertical pivot and the swivel wheel axle occurs becaufie the swivel wheel is stationary, that is, it cannot rotate on its axle, while the pivot is travelling between its two positions.
The wheel is preven-ted from rotating during this time by two helical spring clutches. If the vertical pivot is between its forward and aft positions, both spring clutches are engaged, and the wheel cannot rotate on its axle in either direction. If the vertical pivot is at its forward or aft position, the appropriate spring clutch will be released, permitting the wheel ~o rotate on its axle in the necessary direction. This swi~el wheel arr~
angement allows t~e cart to change ~etween forward and reverse without the swivel wheels swivelling hal~ a turn, an~ there~ore gives the operating person better control o~ the swivel wheels.
4~
Furthermore, this arrangement, because the wheels need not be capable o~ swivelling through a full turn9 allows both wheels in a pair to be easily linked together which ensures that each wheel of the pair swivels by the same amount. ~his advantage permits better control on uneven ground and is particularly useful when the cartwheels make contact with the ground after leaving it, for example, after the cart has been carried, when full control of the wheels can more quickly and easily be acheived.
In drawings which illustrate embodiments of the invention, Figure 1 is an elevation of one wheel, partly in section.
Figure 2 is an end elevation of this wheelg partly in section.
Fig~re 3 is a top plan view of this l,vheel, partly in section.
Figure 4 is a view, in isometric projection, of the spring clutch arrangement.
Figure 5 is an elevation o~ a cart which illustrates the relative positions o~ the vertical pivot and the swivel wheel axles when the cart is moving in the forward direction.
Figure 6 is an elevation of a cart which illustrates the relative posi-tions of the vertical pivo-t and the swivel wheel axles when the cart is moving in the reverse direction.
The wheel illustrated comprises a horizontal bar 1, one end of which is fixed to the cart body and the other end welded to a pair of ~rackets 2 which are attached by screws to the top9 non-rotating member of a thrust ball bearin~ 3 whose axis of of rotation is vertical. If requiredfor cheapness, a plain bearing could be usedO The bottom, rotating member of the bear-ing has a bracke-t attached to it .vhich holds two identical shafts 4, whose axes are harizontal and parallel to each other. Carried ~y each sha~t, and free to rotate on it,is a pair of rolle~s 5.
The horizontal bar 1, brackets 2, bearin~ ~, shafts 4 and rollers 5 form a carria~e which is constrained by slideway 6 to tra~el in a horizontal line which is parallel to the wheel Iace 7. The ~ 3~ ~ Sf~
vertical axis of the thrust bearing 3 is on a vertical plane which is parallel to the wheel face 7 and ~hich bisects the tire 8. The guideway has a stop 9 at each end, shown in -the drawing as a porti~n of the guideway bent round, to ~revent the carriage from touching the wheel rim 10. The bottom part of the guideway is extended and hent upward to form an outer plate 11 hich is parallel and adjacent to the outer face 7 of the wheel.
This outer plate 11 has a clearance hole for a piece of tubing 12.
The tubing is co-axial with the tire 8 and is fixed by welding to the outer face 7. Within the tubing, co-axial with it, and separated from it by bushing 13 is a non-rotating axle 14. The axle has a shoulder 15, or other constraining device, at the outer end, and tG the inner end is attached, b~ a screw, an inner plate 16. The length of the tubing 12 is slightly shorter than the distance between the shoulder 15 and the inner plate 16 so that the wheel is ~ree to rotate, subject only to the constraints of the spring clutches 17. The inner plate 16 is attached ~y three scre~s, one at its centre, which attaches it to the axle lL~
~y means of a threaded hole in the axle, and one at each end, each of ~hich attaches it to a spacer 1~, one end of which has a threaded hole, and the other end of which is attached by weld-ing to the outer plate 11. The spring clutch arrangement consists of two identical close-wound helical springs 17 whose internal diameter, when the springs are free, is slightly smaller than the external diameter of the tubing 12. Each end o~ each spring is extended in a straight line which is perpendicular to the longitudinal axis of the helical portion of the spring, and both ends of each spring are formed such that the angle subtended by them in the plane which is perpendicular to the axis of the helical portion is less than 1~0 degrees and more than 90 degrees~
the exact angle in any particular case depending upon the requir-ed diameter of the wheel rim. The spring clutches 17 are sit~ated on the tubing 12 and the inside of the spring heli~ ~rips the outside of the tubing. The spring nearest the outer plate 11 is arran~ed such that the spring end adjacent -to the o~ter plate is horizontal, ~nd the other end is pointing downward. The horizon-tal end is attached to the outer plate ~y a suitable clamp 1~, and the downward pointing end left free. The spring nearest the inner plate 16 is arranged such that the spring end nearest the inner plate is horizontal, and the other end is pointing down-ward. The horizontal end is attached to the inner plate by a suitable clamp 19, and the downward pointing end left free. The downward pointing, free end of each spring can be raised slightly by a stri~er 20 which is fixed to the hori~ontal bar 1. If the striker ls not in contact with either of the downward pointing spring ends the wheel cannot revolve on its a~le in either direction. If the free end of a spring is raised slightly the helical portion of that spring becomes loose on the tubing 12 and the wheel is ~ree to rotate in one direction, but the other spring, whose downward pointing end remains free, will continue to grip and ~revent the wheel from rotating in the other direct-ion~ It is in the nature of the usual spring clutch, which hasonly one helical spring, to allow rotation in one direction but not in the other. In this invention, two spring clutches and a release device are used to change the direction in which rotation is allowed. Although it is possible, in the case of a three wheeled cart, to have only one swivel wheel, most carts, being four wheeled, will have a pair o~ swivel wheels, in which case it is desirable that both of them swivel at the same time9 in the same direction, and by the same amount. To ensure that this happens, both swivel wheels in a pair are linked to each other by two links, in this invention. Each link 21 is of the same length. Each wheel has attached to its inner plate 16 two bear-ings Z2 for pivots having vertical axes. ~or maximum rigidity 5~
the horizontal dis-tance between the vertical pivots on a wheel should be as large as possible, within practicable limits. Free to rotate in each bearing is a pin 227 and attached to this pin is one end of one of the links 21~ As well as ens~ring that both wheels of a pair swivel together, these two links ensure that both thrust bearings 3 in a pair of wheels are in the same position along their slideways.
SPECIFICATION
This invention relates to a swivel caster or wheel.
It is known for a cart which is guided by a person not riding on it to ha~e a pair of f-xed wheels and a pair of swivel wheels. The fixed wheels are on a horizontal axle which is fixed to the cart and unable to move relative to it. Each swivel wheel is on a short hori~ontal axle which swivels about a pivot having a vertical axis. This vertical axis is on the vertical plane which is parallel to the wheel face and which bisects the wheel tire. Also, the axis of the pivot is on a line which does not intersect the axis of the wheel axle,the horizontal distance between the two axes being the radius of swivel of the wheel axle~ The bearing of the pi~ot is fixed to the cart body, and the rotating part of the pivot is fixed to the wheel axle by means of a bracket. Whith this arrangement the wheels swivel when the operating person applies a sideways force to the Gart.
~owever, to enable the cart to be steered ~y these swivel wheels the swivelling axles must follow the vertical pivots, ta~ing their path, while the cart is moving, which is in any case their natural tendency. This means that when the cart is moving between forward and reverse directions the swivel wheels swivel through half a revolution so that the axle of each swivel wheel can assume a following position relative to that o~ its pivot as the cart moves along in its new direction. Furthermore, if an attempt is made to guide the cart so that it exactly re-traces its origi-nal path while changing direction, each swivel wheel will swivel half a turn in a random direction, that is, either clockwise or counter clockwise, and at an unpredictab~e ins~ant~ shortly after the c~ange in direction between forward and reverse. Therefore, swi~el wheels o~ this type are unsatisfactory for some types of cart, such as lawnmowers, over whose steering full control must be kept by the operating person during c~anOes of d~rection between forward and reverse, when the cart is required to exactly 5~
re-trace its path because, during its swivel through half a turn, one of the wheels would possi~ly collide wit~ a fe~ce or fall over the lawn ed~e into a flower bed.
I have found -that these disadvantages may be overcome ~J
placing the vertlcal pivot in a horizontal slideway which can be situated withln the wheel rim envelope, is parallel to t~e face of the wheel,and is supported, through bearings, by the wheel axleO This arrangement permits the vertical pivot to travel in a horizontal line ~etween two positions, each a~ equal dist-ance from the wheel axle. The bearing of the vertical pivot isfixed to the cart, and the rotating member of the pivot i~ ~ixed to a slider which can travelin the slideway. When the cart is moving forward, the vertical pivot will be in its ~orward pos-ition, that is, forward of, and leading, the wheel axle. '~hen the cart changes to a reverse direction the pivot will travel along the slideway to its aft position, that is, aft of, and leading, the wheel axle. 3ecause the vertical pivot bearings are fixed to the cart, when the pivot moves alon~ the slideway the body o~ the cart and the two fixed a~le wheels move the same distance as the pivot. The relative movement between the vertical pivot and the swivel wheel axle occurs becaufie the swivel wheel is stationary, that is, it cannot rotate on its axle, while the pivot is travelling between its two positions.
The wheel is preven-ted from rotating during this time by two helical spring clutches. If the vertical pivot is between its forward and aft positions, both spring clutches are engaged, and the wheel cannot rotate on its axle in either direction. If the vertical pivot is at its forward or aft position, the appropriate spring clutch will be released, permitting the wheel ~o rotate on its axle in the necessary direction. This swi~el wheel arr~
angement allows t~e cart to change ~etween forward and reverse without the swivel wheels swivelling hal~ a turn, an~ there~ore gives the operating person better control o~ the swivel wheels.
4~
Furthermore, this arrangement, because the wheels need not be capable o~ swivelling through a full turn9 allows both wheels in a pair to be easily linked together which ensures that each wheel of the pair swivels by the same amount. ~his advantage permits better control on uneven ground and is particularly useful when the cartwheels make contact with the ground after leaving it, for example, after the cart has been carried, when full control of the wheels can more quickly and easily be acheived.
In drawings which illustrate embodiments of the invention, Figure 1 is an elevation of one wheel, partly in section.
Figure 2 is an end elevation of this wheelg partly in section.
Fig~re 3 is a top plan view of this l,vheel, partly in section.
Figure 4 is a view, in isometric projection, of the spring clutch arrangement.
Figure 5 is an elevation o~ a cart which illustrates the relative positions o~ the vertical pivot and the swivel wheel axles when the cart is moving in the forward direction.
Figure 6 is an elevation of a cart which illustrates the relative posi-tions of the vertical pivo-t and the swivel wheel axles when the cart is moving in the reverse direction.
The wheel illustrated comprises a horizontal bar 1, one end of which is fixed to the cart body and the other end welded to a pair of ~rackets 2 which are attached by screws to the top9 non-rotating member of a thrust ball bearin~ 3 whose axis of of rotation is vertical. If requiredfor cheapness, a plain bearing could be usedO The bottom, rotating member of the bear-ing has a bracke-t attached to it .vhich holds two identical shafts 4, whose axes are harizontal and parallel to each other. Carried ~y each sha~t, and free to rotate on it,is a pair of rolle~s 5.
The horizontal bar 1, brackets 2, bearin~ ~, shafts 4 and rollers 5 form a carria~e which is constrained by slideway 6 to tra~el in a horizontal line which is parallel to the wheel Iace 7. The ~ 3~ ~ Sf~
vertical axis of the thrust bearing 3 is on a vertical plane which is parallel to the wheel face 7 and ~hich bisects the tire 8. The guideway has a stop 9 at each end, shown in -the drawing as a porti~n of the guideway bent round, to ~revent the carriage from touching the wheel rim 10. The bottom part of the guideway is extended and hent upward to form an outer plate 11 hich is parallel and adjacent to the outer face 7 of the wheel.
This outer plate 11 has a clearance hole for a piece of tubing 12.
The tubing is co-axial with the tire 8 and is fixed by welding to the outer face 7. Within the tubing, co-axial with it, and separated from it by bushing 13 is a non-rotating axle 14. The axle has a shoulder 15, or other constraining device, at the outer end, and tG the inner end is attached, b~ a screw, an inner plate 16. The length of the tubing 12 is slightly shorter than the distance between the shoulder 15 and the inner plate 16 so that the wheel is ~ree to rotate, subject only to the constraints of the spring clutches 17. The inner plate 16 is attached ~y three scre~s, one at its centre, which attaches it to the axle lL~
~y means of a threaded hole in the axle, and one at each end, each of ~hich attaches it to a spacer 1~, one end of which has a threaded hole, and the other end of which is attached by weld-ing to the outer plate 11. The spring clutch arrangement consists of two identical close-wound helical springs 17 whose internal diameter, when the springs are free, is slightly smaller than the external diameter of the tubing 12. Each end o~ each spring is extended in a straight line which is perpendicular to the longitudinal axis of the helical portion of the spring, and both ends of each spring are formed such that the angle subtended by them in the plane which is perpendicular to the axis of the helical portion is less than 1~0 degrees and more than 90 degrees~
the exact angle in any particular case depending upon the requir-ed diameter of the wheel rim. The spring clutches 17 are sit~ated on the tubing 12 and the inside of the spring heli~ ~rips the outside of the tubing. The spring nearest the outer plate 11 is arran~ed such that the spring end adjacent -to the o~ter plate is horizontal, ~nd the other end is pointing downward. The horizon-tal end is attached to the outer plate ~y a suitable clamp 1~, and the downward pointing end left free. The spring nearest the inner plate 16 is arranged such that the spring end nearest the inner plate is horizontal, and the other end is pointing down-ward. The horizontal end is attached to the inner plate by a suitable clamp 19, and the downward pointing end left free. The downward pointing, free end of each spring can be raised slightly by a stri~er 20 which is fixed to the hori~ontal bar 1. If the striker ls not in contact with either of the downward pointing spring ends the wheel cannot revolve on its a~le in either direction. If the free end of a spring is raised slightly the helical portion of that spring becomes loose on the tubing 12 and the wheel is ~ree to rotate in one direction, but the other spring, whose downward pointing end remains free, will continue to grip and ~revent the wheel from rotating in the other direct-ion~ It is in the nature of the usual spring clutch, which hasonly one helical spring, to allow rotation in one direction but not in the other. In this invention, two spring clutches and a release device are used to change the direction in which rotation is allowed. Although it is possible, in the case of a three wheeled cart, to have only one swivel wheel, most carts, being four wheeled, will have a pair o~ swivel wheels, in which case it is desirable that both of them swivel at the same time9 in the same direction, and by the same amount. To ensure that this happens, both swivel wheels in a pair are linked to each other by two links, in this invention. Each link 21 is of the same length. Each wheel has attached to its inner plate 16 two bear-ings Z2 for pivots having vertical axes. ~or maximum rigidity 5~
the horizontal dis-tance between the vertical pivots on a wheel should be as large as possible, within practicable limits. Free to rotate in each bearing is a pin 227 and attached to this pin is one end of one of the links 21~ As well as ens~ring that both wheels of a pair swivel together, these two links ensure that both thrust bearings 3 in a pair of wheels are in the same position along their slideways.
Claims (3)
1. A swivel wheel for use on a cart, lawnmower or any vehicle which is guided by a person not riding on it comprising a wheel, a straight slideway fixed to the wheel axle bearing such that the slideway axis is parallel to the wheel face, extends both sides of the wheel axle and may be held horizontal while the wheel rotates on its axle, a slider which travels along the slideway and fits the slideway so as to prevent all relative movement of the slider to the slideway except along the slideway axis, a pivot whose axis is vertical and on a plane which bisects the wheel tire, whose stationary bearing is fixed to the cart and whose rotating member is fixed to the slider, such arrangement permitting the vertical pivot to travel along a horizontal slideway between two positions, one forward, the other aft of the wheel axle.
2. A swivel wheel as described in claim 1, in which the wheel is prevented, by two helical spring clutches, from rotating on its axle unless the pivot is at one of two positions along the slideway in which an attachment to the pivot bearing releases one of the spring clutches.
3. A pair of swivel wheels as described in claim 1 or 2, in which each wheel of the pair is connected to the other by two horizontal links, the attachments between links and wheels being pivots with vertical axes.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000464237A CA1199154A (en) | 1984-09-28 | 1984-09-28 | Controllable swivel wheel |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000464237A CA1199154A (en) | 1984-09-28 | 1984-09-28 | Controllable swivel wheel |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1199154A true CA1199154A (en) | 1986-01-14 |
Family
ID=4128798
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000464237A Expired CA1199154A (en) | 1984-09-28 | 1984-09-28 | Controllable swivel wheel |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1199154A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0356742A1 (en) * | 1988-08-17 | 1990-03-07 | Jungheinrich Aktiengesellschaft | Castor with an axle or shaft supported in a bracket |
-
1984
- 1984-09-28 CA CA000464237A patent/CA1199154A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0356742A1 (en) * | 1988-08-17 | 1990-03-07 | Jungheinrich Aktiengesellschaft | Castor with an axle or shaft supported in a bracket |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |