Login| Sign Up| Help| Contact|

Patent Searching and Data


Title:
AN ARRANGEMENT IN CARRIAGES WHICH MOVE ON WHEELS ALONG A CARRIAGE SUPPORTING SURFACE
Document Type and Number:
WIPO Patent Application WO/1990/000129
Kind Code:
A1
Abstract:
The invention relates to an arrangement for manually steering and manoeuvering a trolley (2) during movement of the trolley on wheels (3, 4, 6) along a trolley supporting surface (1). At least one of the trolley wheels (6) is arranged for pivotal movement via a steering column (7) having a central rotational axis line (8), such as to steer the trolley during its movement along the supporting surface (1) in dependence on a selected pivot position. The arrangement further comprises a steering device (9) which co-acts non-rotatably with the steering column and with the pivotable wheel (6), which is driven by a wheel drive arrangement connected to the wheel. The steering device (9) includes a manually gripable stick (12) or handle located to one side of the rotational axis line (8). The handle or stick (12) is located forwardly of the rotational axis line when the trolley moves in a forward direction. The steering column (7) and its rotational axis line (8) extend vertically or substantially vertically. The stick (12) is pivotably, displaceably and/or tiltably connected to an upper support (13) rigidly connected to the steering column, so as to activate the wheel drive arrangement (10) to drive the wheel (6) in response to the non-neutral setting of the stick (12). The stick (12) and the steering column (7) can be rotated freely (through 360�) in both directions thus acting as a new type of joy stick function.

More Like This:
Inventors:
Westerlund
Boh
G�sta
Application Number:
PCT/SE1989/000365
Publication Date:
January 11, 1990
Filing Date:
June 27, 1989
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
HELPHER AB WESTERLUND
Boh
G�sta
International Classes:
B62B3/00; B62B5/00; B62B5/06; (IPC1-7): B62D1/04
Foreign References:
DE2751333C2
US4081047A
US3225853A
CH460634A
GB1313884A
SE336049B
Download PDF:
Claims:
CLAIMS
1. An arrangement for manually steering and maneouvering a wheeled trolley along a trolley support surface, in which at least one of the trolley wheels can be pivoted via a steering column having a central rotational axis line such as to be able to steer the trolley for move¬ ment along the trolley supporting surface in response to a selected rotational position , said arrangement com¬ prising a steering device which coacts with the stee¬ ring column and is nonrotational therewith and which also coacts with said pivotable wheel which is driven in response to activation of a wheel drive arrangement, wherein the steering device includes a manually gripable handle or stick positioned to one side of said rota¬ tional axis line, and wherein the stick is located forwardly of the rotational axis line when the trolley moves forwardly, as seen in the direction of trolley movement, characterized in that the steering column and its rotational axis line extend vertically or sub¬ stantially vertically; in that the stick is pivotally, displaceably and/or tiltably attached to an upper sup¬ port rigidly connected to the steering column; and in that the wheel drive arrangement is activateable for driving said wheel in response to a positional setting of the stick relative to the support which deviates from a neutral position; and in that the stick and steering column can rotate freely (through 360°) in both direc tions.
2. An arrangement according to Claim 1, characterized in that the axle of said wheel is located on or to one side of the rotational axis line, in said latter case perpen dicular to said axis line and behind said line as seen in the normal travel direction.
3. An arrangement according to Claim 1 or 2, charac¬ terized in that the trolley comprises a lower, wheeled first frame section and a second frame section which extends upwardly from the first frame section; and in that two steering columns are mounted adjacent said second frame section for coaction with a respective driven and pivotable wheel and with a respective stick.
4. An arrangement according to Claim 1, 2 or 3, charac¬ terized in that the stick is arranged such as to be located in front of the rotational axis line of said steering column upon manual activation to a forward drive position.
5. An arrangement according to Claim 1 or 4, charac¬ terized in that the stick is operative, when manually activated to said position in initiating a throttle function which causes the motor to be driven proportionally to the force exerted on the stick, by virtue of the fact that the position of the stick is communicated to a throttle device connected to the motor.
6. An arrangement according to Claim 1, 2, 3 or 4, characterized in that the stick coacts with a position responsive transducer or sensor, such as a sliding potentiometer or like device, and/or said stick is arranged to coact with a pressure sensor, such as a piezoelectric element.
7. An arrangement according to any one of the preceding claims, characterized in that the stick is spring biased towards a neutral position.
8. An arrangement according to Claim 2 or 4, charac¬ terized in that a telescoping member extends between the two sticks and is connected therewith.
9. An arrangement according to Claim 8, characterized in that sticks are connected together by means of connect¬ ing arms, a part of which is in the form of handles, which extend between respective sticks and in that the arms are connected to said sticks such as to form angles therewith.
10. An arrangement according to any one of the preceding claims, characterized in that the wheel can be braked electrically via said throttle device upon movement of the stick.
11. An arrangement according to any one of the preceding claims, characterized in that a free wheel arrangement is mounted between the motor and associated wheel.
12. An arrangement according to Claim 1 or 4, charac¬ terized in that the arrangement is such that when the stick is moved to a first nonneutral position the wheel will rotate in one direction, whereas when the stick is moved to another nonneutral position, the wheel will rotate in the opposite direction.
13. An arrangement according to Claim 1, 2, 9 or 10, characterized in that the motor incorporates a worm or bevel drive gear, the output shaft of which coacts with the wheel or wheels and which is arranged to pivot with axial rotation of the shaft.
14. An arrangement according to Claim 1, 9 or 12, cha¬ racterized in that a free wheel arrangement and/or differential function is mounted between the output shaft of the worm or bevel drive gear and the wheel pair.
15. An arrangement according to Claim 1, 13 or 14, characterized in that a differential brake or a dif¬ ferential latch is provided at the driven wheel pair.
Description:
TITLE OF THE INVENTION An arrangement in carriages which move on wheels along a carriage supporting surface.

TECHNICAL FIELD

The present invention relates generally to a manually controlled and maneouvered wheeled carriage or trolley, and more particularly, but not exclusively, to a steer¬ ing system for wheeled trolleys of the kind in which at least one of the carriage wheels is pivotally mounted on a steering column or column having a central rotational axis line, such as to be able to steer movement of the trolley during movement thereof along the trolley sup¬ porting surface, in accordance with the selected pivotal setting of said wheel.

To this end, the steering column or rod is arranged to coact with a steering device which is fixedly mounted on the column.

The inventive steering arrangement is particularly suited for trolleys of the kind in which the pivotable wheel is driven by a wheel drive arrangement connected to said wheel, wherein the steering device includes a manually gripable handle or stick located on one side of the rotational axis line. This handgrip will be referred to hereinafter as the stick. The complete function of the steering device is comparable to the function of a joy stick.

When the trolley is moved forward along a straight line, the stick will be located in front of the rotational axis line, as seen in the direction of trolley movement.

BACKGROUND PRIOR ART

Arrangements of the aforedescribed kind are known in several different forms, since many innovations have been proposed in the technical field to which the pre¬ sent invention relates.

There are known to the art many different kinds of arrangements for manually steering and maneouvering a wheeled trolley along a trolley supporting surface, in which at least one of the trolley wheels is pivotally mounted on a steering column or steering rod having a central rotational axis line, such as to be able to steer and move the trolley along the supporting surface in response to a selected pivot position of the wheel, said trolley possibly having the form of a forklift truck or a load supporting carriage. In the case of one known trolley steering arrangement, the positional setting of the wheels is controlled by an arm which is pivotally mounted on the trolley and extends therefrom in co-action with the wheels, such as to pivot or turn the wheels to different angular positions. In the case of this known steering arrangement, the free end of the arm normally carries a steering device which activates the drive to the driven wheel or wheels.

Examples of the prior standpoint of techniques are found described and illustrated in the German Patent Specifi¬ cation 27 51 333, the UK Patent Specification 1 313 884, the Swiss Patent Specification 460 634, the German Lay¬ out Print 24 43 375, the Swedish Patent Specification 336 049 and the German Patent Specification 27 51 333.

Various kinds of driven trolleys are also known for conveying golf clubs around a golf course. The US Patent Specification 4,081,047 teaches an arrangement in which the outer part of a handle on a shaft, is in the form of knob which can be displaced in the aforesaid arm, the position to which this knob is displaced from the arm causing an electric drive motor to be driven in a com¬ mensurate direction.

A corresponding arrangement is described and illustrated in the US Patent Specification 3,225,853, although in this case it is possible to drive the motor in two mutually different directions, in response to the dis- placement position of a handle in relation to an arm, starting from a neutral position.

In the case of this latter arrangement, the trolley will move behind a forwardly walking person, by virtue of a pulling force on the handle, whereas a pressure force on the handle causes the carriage to be driven in front of the walking person, in a rearward movement. This move¬ ment thus takes place with the wheels in an unstable position of alignment and the trolley can only be stee- red with great difficulty.

SUMMARY OF THE INVENTION

TECHNICAL PROBLEM When considering the state of the prior art as described above, it will be seen that a technical problem encoun¬ tered in wheeled trolleys which are manually steered and maneouvered along a trolley supporting surface and having the features set forth in the preamble and ada¬ pted to function as a driven transport trolley in de- partmental stores or warehouses, resides in the pro-

vision of means which will enable a trolley adapted for heavy loads to be maneouvered and steered as easily and as readily as a much lighter trolley which lacks self- drive means, in which preferably all wheels are caster wheels and said trolleys being referred to generally as "customer trolleys" ort "grocery carts".

One technical problem associated with a trolley of this kind, which is pushed in front of a walking person in a forward direction, is one of realizing the advantages which are afforded when the steering column, by means of which the wheel or wheels are steered, and the rota¬ tional axis line of said steering column, extend verti¬ cally, so as to enable the wheel or wheels to be steered directly with the aid of an upper stick or handgrip located to one side of the geometric rotational axis of the column.

It will be seen that a technical problem also resides in realizing the advantages afforded when the stick is pivotably, displaceably and/or tiltably mounted on an upper support which is rigidly connected to the steering column, thereby enabling the trolley to be maneouvered and steered, by driving the drive wheel or drive wheels in response to the positional setting of the stick relative to said support, this setting deviating from a neutral position and being operative in activating the wheel drive machinery.

Another qualified technical problem resides in realizing the advantages afforded when the stick is able to move continuously through 360°, i.e. in the absence of stop positions. Thus causing a completely new type of joy stick function.

It will be seen that a technical problem also resides in the provision of a steering arrangement which is not only suitable for three-wheeled trolleys, of which one wheel is driven and the remaining two wheels are fixedly mounted for movement in a straight line, but also with four-wheeled trolleys or carriages, of which two wheels are driven and two are pivotally mounted on a lower, wheeled frame section, and therewith also realize the advantage afforded in this latter alternative construc- tion when the two driven and pivotable wheels are each activated by a respective joy stick function in a manner to enable the position of the wheels to be set in¬ dividually, so that the trolley can be steered, man¬ eouvered and moved in any desired direction, therewith enabling a heavily loaded trolley provided with the inventive steering arrangement to be maneouvered and steered more readily than a lighter trolley which lacks auxiliary drive means.

It will also be seen that a technical problem resides in realizing the advantages that are afforded by a vertical rotational axis with an upper support and an upper stick, thereby providing conditions such that when the stick is moved in a direction away from the rotational axis the wheels of the trolley will be set for stable wheel movement (forward movement) , whereas when the stick is moved in a direction towards the rotational axis, the trolley is driven in an opposite direction (rearwards) with the wheel settings in an unstable position of wheel alignment.

In this respect, subsequent to forward movement of the trolley with the wheels positioned stably, and when desiring to reverse the trolley, the stick need only be moved towards the geometric rotational axis, whereupon

the wheel drive machinery will drive the wheels in an unstable rearward direction, this wheel drive tending to rotate the wheels and the stick through 180°, therewith bringing the wheels to a stable position of alignment for smooth trolley movement. The stick is then again moved away from the rotational axis, wherewith the wheels are turned to a stable position in the new for¬ ward direction of trolley movement, this direction previously being a reverse direction, irrespective of where the person steering the trolley is located in relation to the trolley.

In the case of smaller trolley or cart drive, it will be seen that a qualified technical problem resides in the use of worm gear motors which are mounted with the motor part rotating about its own axle or steering column, and to integrate the worm gear with requisite free wheel and/or differential functions, while in the case of heavier trolley or cart a problem resides in the provi- sion of adapting known integrated drive assemblies, and of enabling these assemblies to be readily supplemented with requisite free wheel functions.

It will also be seen that a technical problem resides in the provision of a particular joy stick movement pattern cocting with the upper support and to provide means for transmitting the joy stick movement to an electrical throttle system connected to the motor and directional initiating or aiming in a pre-determined path.

It will also be seen that a technical problem resides in realizing the advantages afforded when throttle func¬ tions or system and wheel drive arrangements or drive machinery can accompany the pivotal movement of the wheels around the geometric rotational axis line of the

steering column or rod.

It will be seen that another technical problem resides in the provision of a solution to the electrical trans- mission and control of the drive machinery used in conjunction with a non-restricted pivotable system relative to the frame and batteries.

In the case a four wheeled trolley, it will be seen that a technical problem resides in realizing that steering and maneouvering of the trolley along the trolley sup¬ port surface can be greatly facilitated when the two sticks are interconnected by a telescopic connecting assembly.

It will also be seen that a technical problem resides in realizing the maneouvering advantages afforded when the stick is arranged for movement between pre-determined terminal positions, and particularly when the stick positions provide a forward-reverse-function.

It will also be seen that a technical problem resides in realizing the advantages afforded when a trolley in¬ tended for the aforesaid purpose is provided with a free wheel arrangement between the motor and associated wheel and when means are provided for connecting said free wheel arrangement with the neutral position of the stick.

Steering of the trolley is further facilitated when movement of the stick is operative in activating a progressive forward-reverse-function, and that the free coupling function of the wheel is activated in the neutral position of the stick.

It will also be seen that a technical problem is one of providing connecting shafts which co-act with the sticks and which, in turn, co-act readily with a telescopic assembly, so as to freely determine both the relative positions of the drive motor/wheels and the handgrips.

It will also be seen that a qualified technical problem is one of realizing that in the case of a trolley with which one or more of the aforesaid technical problems have been resolved, maneouvering or steering of the trolley can be greatly simplified when the stick can be moved to a positional setting forwards and backwards from a neutral position against an increasing spring force, and therewith influence the rotational speed of the wheels in a first or second direction in response to the positional setting of the stick.

Finally, a technical problem is one of realizing the significance of a front/brake function as a simpler alternative to the forward/reverse function.

SOLUTION

For the purpose of solving one or more of the aforesaid technical problems, the present invention relates to an arrangement for manually steering and maneouvering a wheeled trolley along a trolley supporting surface, in which at least one of the trolley wheels or wheel pairs can be pivoted via a steering column or rod having a central geometric rotational axis line, such as to steer and move the trolley along the supporting surface in response to the positional setting of the wheel or wheel pair. The steering column or rod is connected rigidly to a steering device and the pivotable wheel is driven by a wheel drive mechanism connected thereto. The steering device has mounted thereon a manually gripable stick .

which is positioned to one side of the rotational axis and which, when the trolley moves in a straight line, is located forwardly of the rotational axis line, as seen in the direction of trolley movement.

It is proposed that the steering column and its rota¬ tional axis line extend vertically, or at least sub¬ stantially vertically; that the stick is pivotally, displaceably and/or tiltably attached to an upper sup- port rigidly connected to the steering column such as to be non-rotatable relative thereto; and that said drive machinery is operative to change the torque and rota¬ tional direction of said wheels in response to changes in the positional setting of the stick relative to said support, said setting deviating from a neutral position; and that the stick and the steering column are mounted for rotation through 360° in both directions.

Also lying within the scope of the invention are embodi- ments in which the axle of the wheel is located to one side of and perpendicular to the rotational axis line, and also rearwardly behind said rotational axis line, as seen in the direction of trolley movement.

According to one embodiment of the invention, the trol¬ ley includes a lower, wheeled first frame section and a second frame section which is upstanding from said first frame section, wherein two steering columns are arranged adjacent said second frame section for co-action with a respective driven and pivotable wheel and each provided with an individual joy stick function.

The stick or sticks is/are preferably so arranged that when manually activated for forward trolley drive, the stick will be located forwardly of the rotational

axis line of said steering column, as seen in the direc¬ tion of trolley travel, and that the stick is arranged to exercise a throttle function when moved manually in said direction, this throttle function resulting in driving of the motor in proportion to the force exerted on the stick, this being achieved by virtue of the fact that the position of the stick is communicated to a throttle device connected to the motor.

The stick may be arranged to co-act with a position- dependent transducer or sensor, such as a sliding poten¬ tiometer or some corresponding device, and/or the stick may be arranged to co-act with a pressure sensor, such as a piezoelectric element. The stick is preferably spring biased towards a neutral position.

In the case of dual-driven wheels or wheel pairs, there is preferably arranged between the two joy sticks a telescopic device preferably adapted as handgrip, which is connected with said sticks to form a "joy stick handle assembly". Thus extending between respective sticks and telescopic handle device are connecting arms which are rigidly connected to and forming said hand¬ grips.

According to another suitable embodiment of the inven¬ tion, the wheel can be braked electrically in response to stick movement, via said throttle device. Freewheel arrangements may be provided between the motor and associated wheel, for the purpose of facilitating twist¬ ing, slewing or like pivotal movement.

The wheel may be arranged to rotate in a first direction when the stick is moved to a first position deviating from the neutral position, and to rotate in a second

direction when the stick is moved to a second position opposite to said first position and deviating from said neutral position, thereby providing a front/back func¬ tion.

According to another embodiment of the invention, the motor may be integrated with bevelled gear drive, the output shaft of which co-acts with the wheel or wheels and which is mounted for rotation with said steering column.

Finally, it is proposed that a free wheel arrangement and/or the aforesaid differential arrangement is mounted between the output shaft of the bevelled gear drive and the wheel pair.

ADVANTAGES

Those advantages primarily associated with an arrange¬ ment for steering a moveable wheeled trolley along a trolley support surface in front of a person steering the trolley, in accordance with the present invention, reside in the provision of conditions which enable a loaded, heavy goods trolley driven by one or more drive machines to be readily maneouvered by hand in any selec- ted direction, in the same easy manner as a much lighter trolley running on three or more wheels, e.g. a customer trolley in a departmental store.

The primary characteristic features of an arrangement according to the present invention are set forth in the characterizing clause of the following Claim 1.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail with reference to two embodiments thereof at present prefer-

red and with reference to the accompanying drawings in which:

Figure 1 is a perspective view of a trolley having two fixed wheels positioned with their respective axles perpendicular to the longitudinal extension of the trolley, and a pivotable driven wheel; Figure 2 is a perspective view of a four-wheeled trol¬ ley, having two casters and two pivotable, driven wheels, the latter in the form of wheel pairs; Figure 3 is a perspective view of a proposed attachment of a stick to an upper support;

Figure 4 illustrates schematically a known electric coupling device operative to drive an electric motor in a first or second direction of rotation, in dependence on the positional setting of the stick;

Figure 5 is a side view of an electric motor equipped with a worm gear and incorporating a differential and/or freewheel coupling arrangement for driving one wheel pair; and Figure 6 is a perspective view of an integrated wheel drive motor having one wheel.

DESCRIPTION OF EMBODIMENTS AT PRESENT PREFERRED Figure 1 is a perspective illustration of one embodiment of a steering system applied to a three-wheeled trolley 2 which can be maneouvered and steered by a single per¬ son along a trolley supporting surface 1 , with said person located behind the trolley.

Two of the wheels, here referenced 3 and 4, are fixedly mounted on a load carrying platform 5 and are positioned so as to rotate parallel to the longitudinal axis of the platform 5. The remaining wheel 6 is pivotally mounted on a vertical steering column 7 having a central rota- tional axis 8, said wheel 6 having unlimited rotational

freedom, such as to enable the trolley to be steered freely along the supporting surface 1 in a direction contingent on the angular position of said wheel. Steer¬ ing is effected by means of a steering arrangement generally referenced 9 having a function similar to the function of a joy stick, which is rigidly mounted on the steering column and which will be described in more detail hereinafter with reference to Figure 3.

The pivotal wheel 6 is driven by an actuatable drive arrangement 10 connected to said wheel, said arrangement comprising an electric motor and associated devices connected thereto, as described in more detail herein¬ after with reference to Figure 6.

The embodiment illustrated in Figure 1 also comprises a battery housing 11 which accommodates the batteries required to drive the motor 10.

The steering arrangement 9 includes a stick 12 which is located to one side of the rotational axis line 8 and when the trolley is moved forwards in a straight line, as illustrated in Figure 1, the stick will be located forwardly of the axis line, as seen in the direction of trolley movement.

It should be observed that the person steering and maneouvering the trolley 2 will normally walk behind the trolley in the illustrated direction of trolley movement F, which means that in the direction of forward trolley movement the trolley is "pushed" by said person and, in the reverse direction of trolley movement is "pulled" behind said person, in response to appropriate pushing (pressing) or pulling force (drag) on the stick.

The radial distance of the stick from the rotational axis line 8 should be greater than 3 cm but less than 20 cm, and will preferably be from 5-10 cm.

As will be seen from Figure 1, the steering column 7 and its rotational axis line extend vertically. It lies within the scope of the invention, however, for the steering column and its rotational axis line to extend substantially vertically.

The stick 12 is pivotably, displaceably and/or tiltably attached to an upper support 13 having the form of a round disc attached rigidly to the steering column 7.

As will be described in more detail hereinafter with reference to Figure 4, the drive machinery 10 is activated to drive said wheels, in response to movement of the stick relative to the support 13 to a position which deviates from a neutral position.

It will be seen from Figure 1 that the stick 12 can be moved smoothly and continuously through 360° in either direction, i.e. in the absence of a stop position, thereby enabling the stick 12 to be rotated about the rotational axis line 8 to any selected position, either directly or subsequent to a selected number of revolu¬ tions, without intermediate stopping.

The axle 6a of the wheel 6 is preferably located immediately beneath or to one side of the rotational axis line 8, and then perpendicularly to said axis line immediately behind said line as seen in the movement direction F, and consequently when the trolley is moved forwards in said forward direction F the stick 12 will be located in front of the rotational axis line 8 and

the wheel axle 6 will be located on or behind said axis line but in a plane coinciding therewith.

Figure 1 illustrates one embodiment of a wheel 6. The wheel, however, may also have the construction illustra¬ ted in Figure 5 or Figure 6. When the wheel 6 is a double-wheel unit, i.e. a wheel pair, the wheel drive may be mounted between the two wheels of said pair.

The stick is connected to a throttle device which is operative to activate the motor in response to the position of the stick.

Both the throttle device and the motor are connected to the steering column 7 and participate in rotating the steering column about its longitudinal axis. Current is supplied via electrical sliding contacts.

Figure 2 illustrates a second embodiment of the inven- tive arrangement, in which the steering arrangement shown in Figure 1 is duplicated.Thus, the load carrying platform 5 is supported by a lower wheeled first frame section 20. Extending upwardly from the first frame section is a second frame section 21, and two vertical steering columns 7, 7' are mounted adjacent said second frame section 21. Each of the steering columns 7, 7 / co- acts with a respective driven and pivotable wheel 6, 6" and are each provided with a respective stick 12, 12'. In the case of the illustrated embodiment, the wheel 6 and 6' are wheel pairs which are driven in a manner described below with reference to Figure 5.

The frame section 20 has two caster wheels 3, 4 mounted thereto.

The battery housing is not shown in Figure 2, for the sake of clarity.

The description of the steering arrangement made with reference to Figure 1 will thus apply to the steering arrangement illustrated in Figure 2, but in duplicate.

Thus, the sticks 12, 12' of respective handle assemblies 22 and 22' will be arranged such that upon manual ac- tivation in a common forward drive direction F they will be located in front of the respective rotational axis lines 8, 8' of the steering columns 7, 7' as seen in said forward direction; and that the sticks are opera¬ tive in exercising a throttle function upon said manual activation in said movement direction, such as to drive respective motors 10, 10' proportionally to the force exerted on the sticks, by virtue of the fact that move¬ ment of the sticks is transmitted to respective throttle devices connected to respective motors.

In the case of the Figure 2 embodiment, it is also possible to turn the two wheels 6, 6' independently of one another to different positional settings, and to subject said two wheels 6, 6' to mutually different torque from their respective motors 10, 10', in response to the positional setting of the sticks 12, 12'.

Thus, the joy stick handle assembly 22, 22' which join the sticks can be manipulated to drive the motors in a common forward movement of the trolley, or may mutual¬ ly co-act to drive the wheels 6,6' in common, to move the trolley in the opposite direction, or may work against one another such as to cause the wheels to rotate at different speeds and in different directions.

A common feature of the Figure 1 and Figure 2 embodi¬ ments is that a force applied to the stick 12, 22 in a direction away from the steering column 7 will activate the wheel drive for forward trolley movement, whereas a force applied in a direction towards the steering column 7 will activate rearward drive of the trolley.

It should be mentioned that when the wheels and the stick are in a forward drive position and the back function is activated, it has been found in practice that the wheels tend to rotate through 180°, therewith activating the forward drive function. The back function thus becomes an exception.

As will be seen from Figure 3, the stick 12 can be moved to three separate positions, a neutral position 12a, a second position 12b for driving the wheel 6 in a forward direction F, and a third position 12c in which the wheel 6 is driven for rearward trolley movement B.

To this end, it shall be possible to move the stick 12 relative to the support 13, in a known manner, for on- off function and co-act with position responsive trans¬ ducers or sensors, such as sliding potentiometers or the like and/or pressure sensitive transducers, such as piezoelectric devices with associated control circuits.

The stick 12 may also be biased towards its neutral position 12a by springs 25, 26, as illustrated in Figure 4.

When the stick 12 is pushed in the direction F, a slid¬ ing contact 27 is moved along a resistance 28, therewith activating a known electric starting device 29 which supplies current to the motor 10 via a supply circuit 30

and conductors 31.

It also lies within the scope of the invention to pro¬ vide an "on/off"-function activated by the stick 12. In the case of the Figure 4 embodiment, however, the elect¬ rical throttle device is operative in increasing the torque on the motor 10 in response to the distance through which the stick 12 is moved from a neutral position.

A variant of the joy stick function (12) is shown in Figure 2, in which two joy stick connecting arms 22, 22' a part of which forms the handles connecting the stick attachments 12, 12' of this embodiment have extending therebetween a hollow member 23, such as to form a tele¬ scopic assembly 22, 23, 22', the connecting arms forming an angle with respective handle members and the sticks in the manner illustrated in Figure 2.

Figure 5 is a side view of a motor 10 which incorporates a worm or bevel gear drive 50, the output shaft of which co-acts drivingly with the wheel pairs 6 via a free wheel arrangement and/or a differential gear even during pivoting of the wheel pair on the steering column 7.

The function of a proposed differential gear 51 is based on the friction engendered between balls and two disc plates, the balls 53 being seated in holes in a driven disc plate 52.

The disc plate 52 is driven with the aid of a belt, chain, worm or gear wheel.

The balls 53 in the disc plate 52 are located in holes 53' disposed around a circular line and are moved round in a circular path.

Located on each side of the disc plate 52 are further discs 54, 54' which are pressed against the balls 53, to ensure that the requisite friction is obtained. Each of the further discs 54, 54' is provided with a circular groove 55 which serve as a running surface for the balls when the grooves face one another.

When the drive disc plate 52 rotates, the mutually facing discs 54, 54' are rotated at the same speed with equal braking force. When pivoting on the steering column 7, the two wheels rotate at mutually different speeds and optionally in different directions.

In order to prevent unintentional differential effects, the gear arrangement can be provided with different types of free wheel and/or differential brake or latch¬ ing functions of known construction.

Alternative couplings between drive steering column (drive steering columns) and wheels which afford said function may also be used.

It should be noted that when applicable the term "wheel" used in the aforegoing can be replaced with the term "wheel pair".

Figure 6 illustrated an integrated drive motor for driving a wheel 6 with the aid of an electric motor 10 and a gear arrangement 51'. The axle 6a of the wheel is, in this case, located in the centre of the rotational axis line 8.

It will be understood that the invention is not restric¬ ted to the aforedescribed embodiments thereof and that modifications can be made within the scope of the inven¬ tive concept.