WO1996007555A1

WO1996007555A1 - Trolley comprising floor-engaging wheels and auxiliary wheels coupled to the floor-engaging wheels

Info

Publication number: WO1996007555A1
Application number: PCT/IB1995/000704
Authority: WO
Inventors: John Alfons Maria Verbruggen
Original assignee: Philips Electronics N.V.; Philips Norden Ab
Priority date: 1994-09-07
Filing date: 1995-08-28
Publication date: 1996-03-14

Abstract

An unattended trolley (for example, supporting a work station fora mobile X-ray apparatus) which collides with a threshold-like obstacle (34) on the floor will tend to be overturned. In order to increase the resistance against overturning, the floor-engaging wheels (18) of the trolley are provided with auxiliary wheels (20) which are situated a small distance above the floor. In the case of collision with a threshold (34), first the auxiliary wheel (20) will pass the threshold so that the trolley is lifted a first distance. Subsequently, the floor-engaging wheel (18) crosses the threshold, the trolley thus being lifted the remaining distance. The vertical impact of the collision is thus distributed between two impulses, thus reducing the tendency to overturning.

Description

Trolley comprising floor-engaging wheels and auxiliary wheels coupled to the floor-engaging wheels.

The invention relates to a trolley intended to travel on a floor surface, comprising a number of floor-engaging wheels and at least one auxiliary wheel whose shaft occupies a fixed position relative to the shaft of at least one of the floor-engaging wheels and extends parallel thereto, the lower side of said auxiliary wheel being situated above the floor surface engaged by the floor-engaging wheels during travel.

The invention also relates to an assembly of a floor-engaging wheel and an auxiliary wheel, which assembly is suitable for use in such a trolley.

A trolley of this kind is known from United States Patent Specification No. 4,387,468. The trolley described therein is used for a mobile X-ray apparatus as used, for example in hospitals. This trolley consists of a base on which a rotatable column for an X-ray apparatus is mounted. The base comprises two legs whereto the floor-engaging wheels are secured, which wheels are mounted on shafts which extend perpendicularly to said legs. On the end of the legs there is mounted a bight, at the centre of which the auxiliary wheel is secured. The shaft of the auxiliary wheel extends parallel to the shaft of the floor-engaging wheel and mounting is such that some clearance exists between the lower side of the auxiliary wheel and the floor on which the trolley rests. Authorities nowadays tend to impose increasingly severe requirements as regards the stability of trolleys in working environments such as hospitals. For example, there is the requirement that when an unattended trolley travelling at a given speed collides with an obstacle (for example, a threshold) of a given height, it may not be overturned by such a collision. (For example, see "International Standard" IEC 601-62B CA 108A.) In order to satisfy this requirement, designers tend to make the basal area of the trolley much larger, for example by providing projecting wheel supporting arms. This has the drawback that such trolleys occupy more floor surface area than actually required by the dimensions of the equipment mounted thereon. It is then difficult or even impossible for such trolleys to pass through door openings of standard dimensions. Moreover, large supporting arms constitute obstacles which could interfere with the operating personnel.

The known trolley can more readily overcome small obstacles such as thresholds and the like on the floor on which the trolley travels. In this trolley, however, the distance between the auxiliary wheel and the floor-engaging wheels in a direction perpendicularly to the axial direction is of the order of magnitude of the diameter of a floor- engaging wheel or even larger. Consequently, comparatively narrow obstacles (i.e. obstacles whose dimension in the direction of travel is smaller than said diameter) still have the same overturning effect as in the absence of an auxiliary wheel.

It is an object of the invention to provide a trolley which better satisfies the more severe requirements as regards resistance against overturning, without it being necessary to increase the required basal area significantly.

To this end, the trolley in accordance with the invention is characterized in that a line extending in the prolongation of the shaft of the auxiliary wheel intersects the associated floor-engaging wheel on or within the circumference of this wheel, and that the perpendicular projection of the circumference of the auxiliary wheel onto the floor-engaging wheel is situated partly outside the circumference of the floor-engaging wheel.

When the lower side of the auxiliary wheel is arranged approximately halfway the height of the obstacles to be expected, the impact exerted on the trolley by the obstacle in the case of a collision is distributed approximately equally between two impulses, that is to say one on each of the wheels (i.e. the auxiliary wheel and the floor-engaging wheel), regardless of the width of the obstacle. The tendency of the trolley to be overturned by the collision is thus reduced. A preferred embodiment of the trolley is characterized in that the assembly formed by the auxiliary wheel and the associated floor-engaging wheel comprises a second floor-engaging wheel whose shaft is situated in the prolongation of that of the former floor-engaging wheel, the auxiliary wheel being arranged between said two floor-engaging wheels. In this configuration, the intended force distribution between the wheels takes place even in the case of obstacles whose dimension in the direction of the shaft is of the order of magnitude of the width of the set of wheels. The invention will be described in detail hereinafter with reference to the Figures in which corresponding reference numerals denote corresponding elements. Therein:

Fig. 1 shows a trolley for use as a mobile X-ray apparatus, comprising auxiliary wheels in accordance with the invention; Fig. 2 is a more detailed representation of a floor-engaging wheel and an auxiliary wheel in accordance with the invention;

Fig. 3 shows an embodiment of the invention, consisting of an assembly of two floor-engaging wheels and one auxiliary wheel.

Fig. 1 shows a trolley for use as a work station for a mobile X-ray apparatus, for example for use in a hospital. A number of short supporting arms 4 is connected to a base 12, a set of wheels 14 being secured to each supporting arm. These sets of wheels will be described in detail hereinafter with reference to the Figs. 2 and 3. On the base 2 there is arranged a cabinet 6 in which data processing equipment is accommodated. The trolley also comprises a keyboard 8 for operating the equipment and two monitors 10. There is also provided a space 12 for accommodating additional equipment, for example a video recorder or a copier.

Fig. 2 shows an assembly 14 consisting of a floor-engaging wheel 18 and an auxiliary wheel 20. The base 12 is provided with a number of such wheel sets 14, each of which consists of two floor-engaging wheels 18 wherebetween an auxiliary wheel 20 is arranged. The wheel sets .14 are rotatable relative to the base 12 about an axis 17. The auxiliary wheel 20 is mounted so that its lower side is situated at a small distance from the floor 22 on which the trolley travels. The floor-engaging wheel 18 is mounted on a holder 16 which is rotatable relative to the base 12 about an axis 17; this is realised in that one end of the holder 1§ is mounted in a bearing 24 provided in a housing 26. The housing 26 is connected to the base 12 by way of a mounting member 28. The floor-engaging wheel 18 is mounted on a supporting plate 25, forming part of the holder 16., so as to be rotatable about a shaft 30. An auxiliary supporting plate 31 is rigidly connected to the supporting plate 25, the auxiliary wheel 20 being mounted on said auxiliary supporting plate so as to be rotatable about a shaft 32. As a result, the shaft 32 occupies a fixed position relative to the shaft 30. The diameter of the floor-engaging wheel 18 amounts to 150 mm and that of the auxiliary wheel 20 to 60 mm. Because it is desirable to arrange the keyboard 8 at working level and the monitors 10 at viewing level, the weight distribution on the trolley is such that overturning upon a collision with a threshold-like obstruction is not precluded. When obstacles are expected to be present on the floor 22 (for example, thresholds or cables) which have, for example a height of 20 mm, the auxiliary wheel can be arranged in such a manner that its lower side is situated at a distance of 14 mm from the floor. When the trolley collides with the threshold (34), first the auxiliary wheel contacts the threshold; the trolley is then lifted over a distance of 6 mm. Subsequently, the floor-engaging wheel contacts the threshold, the trolley then being lifted 14 mm. Because the diameter of the floor-engaging wheel in this example is substantially larger than that of the auxiliary wheel, the impact on the floor- engaging wheel is less than could be expected on the basis of the difference in height.

Fig. 3 shows a preferred embodiment of the assembly of floor-engaging wheel and auxiliary wheel. Therein, the auxiliary wheel 20 is arranged between two floor- engaging wheels 18a and 18b. The wheel diameters and the difference in height are the same as in Fig. 2. Even though the wheel suspension in this Figure is constructed as a holder 16 provided between the floor-engaging wheels 18a and 18b, it is alternatively possible to construct the wheel suspension in the form of a double plate, one plate portion being present on the outer side of each of the floor-engaging wheels. The horizontal cross-section of this holder is then U-shaped.

Claims

CLAIMS:

1. A trolley intended to travel on a floor surface (22), comprising a number of floor-engaging wheels (18) and at least one auxiliary wheel (20) whose shaft (32) occupies a fixed position relative to the shaft (30) of at least one of the floor-engaging wheels (18) and extends parallel thereto, the lower side of said auxiliary wheel (20) being situated above the floor surface (22) engaged by the floor-engaging wheels (18) during travel, characterized in that a line extending in the prolongation of the shaft (32) of the auxiliary wheel (20) intersects the associated floor-engaging wheel (18) on or within the circumference of this wheel, and that the perpendicular projection of the circumference of the auxiliary wheel onto the floor-engaging wheel is situated partly outside the circumference of the floor- engaging wheel.

2. A trolley as claimed in Claim 1, characterized in that the assembly Q4) formed by the auxiliary wheel (20) and the associated floor-engaging wheel (18a) comprises a second floor-engaging wheel (18b) whose shaft (30) is situated in the prolongation of that of the former floor-engaging wheel (18a), the auxiliary wheel (20) being arranged between said two floor-engaging wheels (18a, 18b).

3. An assembly (14) of a floor-engaging wheel (18) and an auxiliary wheel (20) which is suitable for use in a trolley as claimed in any one of the preceding Claims, which assembly Q4) comprises a wheel suspension Q6J which is rotatable about an axis (17) and which is intended to be connected to a trolley, said axis (17) extending perpendicularly to the shaft (30) of the floor-engaging wheel (18), the lower side of the auxiliary wheel (20) being situated above the plane (22) through the lower side of the floor-engaging wheel (18), shifted in the direction of the axis (17) of the wheel suspension Q6J, so that a line extending in the prolongation of the shaft (32) of the auxiliary wheel (20) intersects the associated floor-engaging wheel (18) on or within the circumference of this wheel, and that the perpendicular projection of the circumference of the auxiliary wheel (20) onto the floor- engaging wheel is situated partly outside the circumference of the floor-engaging wheel.