SVANTESSON, Esbjörn (Enstavägen 2, Täby, S-187 35, SE)
BERNDTSON, Maria (Völundsgatan 1, _3tr, Stockholm, se-113 21, SE)
JONSSON, Stefan (Rålambsvägen 21, Stockholm, S-112 59, SE)
TRYDEGÅRD, Anna-Karin (Norrtullsgatan 21, Stockholm, S-113 27, SE)
SVANTESSON, Esbjörn (Enstavägen 2, Täby, S-187 35, SE)
BERNDTSON, Maria (Völundsgatan 1, _3tr, Stockholm, se-113 21, SE)
JONSSON, Stefan (Rålambsvägen 21, Stockholm, S-112 59, SE)
CLAIMS
1. Wheel for floor care appliances, such as vacuum cleaners or the like, to allow smooth and easy moving of the appliance over a supporting structure, such as a floor, comprising an axis of rotation, a wheel body (5) and a tread surface (7), c h a r a c t e r i z e d in that the wheel also comprises a gas cushion layer (6), in form of a shell structure of a resilient material, which defines several, separate gas cells (8, 13) filled with gas .
2. Wheel according to claim 1, c h a r a c t e r i z e d in that the gas cushion layer (6) is manufactured from transparent plastic.
3. Wheel according to claim 1 or 2, c h a r a c t e r i z e d in that a layer (7) forming a tread surface is applied over the gas cushion layer (6) .
4. Wheel according to any of the preceding claims, c h a r a c t e r i z e d in that it comprises one continuous gas cell (8) extending around the circumference of the wheel, and several confined, separate gas cells (13) , which are distributed over the circumference of the wheel and which are arranged inside the circumferential continuous gas cell.
5. Wheel according to claim 2, c h a r a c t e r i - z e d in that the transparent gas cushion layer (6) is visible from the outside of the wheel (4) .
6. Wheel according to any of the preceding claims, c h a r a c t e r i z e d in that the gas cushion layer is filled with a gas having generally atmospheric pressure .
7. Wheel according to any of the claims 4-6, c h a r a c t e r i z e d in that the separate gas cells (13) each are formed as tubular columns extending from a radially inner wall portion (9) to a radially outer wall portion (10) of the circumferential, continuous gas cell (8) .
8. Wheel according to any of the preceding claims, c h a r a c t e r i z e d in that the cells (8, 13) are of an open type, each having at least one opening through a confining wall such that air can escape from or enter into the cell through the opening. |
WHEEL FOR FLOOR CARE APPLIANCES
The invention relates to a wheel for floor care appliances, such as vacuum cleaners or the like, to allow smooth and easy moving of the appliance over a supporting structure, such as a floor, comprising an axis of rota- tion, a wheel body and a tread surface.
Background of the invention
The use of wheels is desirable in connection with different floor care appliances such as e.g. vacuum cleaners and nozzle heads for vacuum cleaners.
To reduce costs, such wheels are normally very simple. Often formed as a unitary part of rigid plastic and sometimes provided with a tread surface of elastic plastic or rubber. One disadvantage with such a simple wheel structure is that the wheels are quite noisy during use since they can not provide proper damping when moved over a floor having a hard surface or when hitting an obstacle such as a doorstep or the like. This kind of floor care appliances are normally adapted to be used indoors and the noise generated can be very disturbing, especially during late hours or in environments where it is desirable to maintain silence.
Normally, wheels having inflatable tyres are not an option for this kind of appliances since such types of wheels as a rule are to expensive to manufacture and needs maintenance in form of occasionally pumping as well as are susceptible to puncture. Moreover, these kinds of appliances are normally to light weight for inflatable wheels to be able to provide proper resilient properties and hence damping. Also, inflatable wheels are restricted in terms of alternative design options.
One possibility to overcome the disadvantages above, would be to manufacture the wheel of a soft and elastic plastic, such as foam plastic, which could provide the
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2 desirable damping properties. However, such soft plastics are often not sufficient durable and wear resistant. Also the grip of the wheel towards the floor will often be too good which sometimes is undesirable when the appliance needs to be moved laterally without rotating the wheels. A wheel of this type is disclosed in DE 19712138, wherein a wheel body of a soft and elastic material is sandwiched between two stiffening disks . A similar wheel is disclosed in EP 716938. In US 5255410 is disclosed a wheel, which has a wheel body of a hard material and in a preferred embodiment is assembled of two matching partial wheel elements. The wheel body comprises a circumferential groove in which is positioned an elastic, annular tyre having a portion protruding beyond the circumference of the wheel body. Underneath the bottom surface of the tyre, there is preferably a deflection space to allow deflection of the tyre. The object of this structure is to make it possible to use a tyre material having high wear resistance and still achieve a high damping effect. However, this structure allows only for a limited deflection of the tyre and hence a low damping effect. Also, a large part of the circumference of the hard material wheel body is exposed on each side of the tyre which can bump into obstacles during use and cause unwanted noise.
Another type of a wheel having a damping effect, is disclosed in EP 858760. Here, the wheel is formed with an inner support ring and an outer roller ring, which roller ring is manufactured of an elastic material and in one lateral edge attached to the support ring whereas the opposed edge is free and disposed on a distance from the support ring. Accordingly, the support ring provides for the load-carrying structure whereas the roller ring provides for the damping feature since it can deflect elas- tically. However, there are several disadvantages associated with such a wheel. Although the roller ring is elastic it is also made of a hard material which, when roll-
ing over a floor, can cause disturbing noise, especially if the floor is covered by sand or other kinds of debris . Moreover, the construction of the wheel has to effect that the diameter of the wheel, and hence the ground clearance, will vary to a large extent depending on the load applied on the appliance. The contact surface of the roller ring against the floor will also be inclined for most of the load situations, which can cause the wheel to deviate in one direction when rolling over the floor. The design of the wheel having one support ring and one roller ring located concentric with a small gap there between, may also cause debris to stuck inside the gap which, as the debris build up, eventually will restrict the deflecting action of the roller ring.
Summary of the invention
An object of the invention is to overcome the drawbacks of prior art wheels and provide a wheel, which exhibit good resilient and damping characteristics for a floor care appliance and yet can be manufactured to a low cost. At least this object can be achieved by a wheel according to claim 1.
Accordingly, the basis of the invention is the insight that the above object may be achieved by a wheel, which comprises a resilient gas cushion layer being provided with a plurality of confined compartments or cells filled with a gas, preferably air. Within this general inventive idea, the invention may be varied in many different ways . In a hereinafter described and illustrated embodiment, the resilient gas cushion layer is in form of a ring or tube of a resilient material which is mounted on the circumference of a hub, the tube being reinforced by a plurality of tubular columns, which are of the same ma- terial as the tube, are evenly distributed over the circumference of the wheel and each extends in a radial direction from an inner circumferential wall of the tube to
an outer circumferential wall. The tube as well as the tubular columns are manufactured in form of a shell structure of a resilient material. The walls of the shell structure have preferably a thickness in the range of 1-3 mm. Accordingly, there is provided a continuous, confined and circumferential gas space inside the tube and separate, confined gas spaces in the tubular columns inside the tube .
However, also other forms and embodiments of the air cells are possible. The tube could for instance instead be segmented by partition walls arranged in the radial direction of the wheel in parallel to the rotational axis . In this way the tube will be provided with confined cells laying in sequence along the circumference of the wheel. The cells could also be arranged in two or more layers on top of each other.
The confined cells in the gas cushion layer can optionally be hermetically sealed, such that they are gas tight, and the load-carrying effect will in such a case be performed by the gas pressure inside the cells in combination with the supporting effect from the supporting structure represented by the walls of the shell structure .
As an alternative, the confined cells can be more or less open, such that the walls of the shell structure exhibit e.g. small holes through which the air can dissipate from or enter into the cells depending on whether the cell is exposed to a pressure or not. The open cells can be in fluid communication with the air surrounding the floor care appliance and/or with each other.
In an embodiment having open cells communicating with the surrounding air, at least the long term load- carrying effect is provided entirely or at least mainly by the walls in the shell structure. However, the load- carrying effect in the short term, e.g. during rotation of the wheel over a floor, can also be provided by the air pressure inside the cells provided that the openings
through the walls are sufficient small such that the air can escape slowly from the cells. In this way the air inside the cells will contribute to the damping and resilient effect of the wheel. As soon as the cell in question is revealed from the load, the air will begin to flow back inside the cell again due to the resilient properties of the shell structure. One advantage with such a construction is that in case of a puncture in one of the cells, the load-carrying effect of that cell, at least within the short term aspect, is maintained. This makes the wheel invulnerable for puncture. Another advantage is that the damping and resilient properties from a wheel having open gas cells can be sufficient also for a light weight floor care appliance, such as a small vacuum cleaner.
In case of hermetically sealed compartments or cells, the gas pressure inside could be a pressure exceeding the atmospheric pressure. However, it is preferred to use an atmospheric pressure inside the cells since this will make the wheel easy and inexpensive to manufacture and low weight appliances will in most cases not require any overpressure to bear the load. Instead, the load-carrying is provided as a combination of the confined gas and the partition walls defining the sepa- rate gas cells. In that way the risk for puncture is minimized but should a puncture nevertheless occur, it is normally restricted to only one gas cell and the bearing as well as the damping properties can be taken over by adjacent gas cells and the partition walls confining the gas cells. Moreover, the cells could be filled with arbitrary suitable gases, for instance nitrogen, but for ease of manufacture and reasons of costs, air is preferred.
Preferably, the gas cushion layer is positioned on a rim or hub, which can be formed in many different ways and of different materials. For instance, the hub can be made of metallic or plastic material, can be provided with an integrated rotational shaft or be provided with a
hole for accommodating a stationary shaft attached to the appliance .
A tread surface for rolling over a floor, can be integrated with and manufactured of the same material as the gas cushion layer. However, also a separate tread surface layer can be applied on the gas cushion layer. In a hereinafter described and illustrated embodiment of the invention, the gas cushion layer is manufactured of a transparent plastic, which is visible from the outside of the wheel. This creates a visually attractive appearance of the wheel which can be altered by dying the transparent plastic in different colours. A separate, thin tread surface layer of dark rubber or plastic is applied on the outer circumference of the gas cushion layer. Although the hereinafter described and illustrated embodiment of the invention is described in relation to application on a vacuum cleaner, it is to be understood that the wheel can be applicable also on other kinds of floor care appliances, as mentioned before.
Brief description of the drawings
The invention will now be described with reference to the drawings in which: Fig 1 is a perspective view of a vacuum cleaner equipped with wheels according to the invention; Fig 2 is a cut perspective view in larger scale of the wheel in fig 1; Fig 3 is a cross section in parallel to the rota- tional axis of the wheel in fig 2; and
Fig 4 is a cross section perpendicular to the rotational axis of the wheel in fig 2.
Detailed description of an embodiment of the invention
Reference is first made to fig 1, in which is illustrated a possible embodiment of a vacuum -cleaner equipped
with wheels according to the invention. The vacuum cleaner comprises a vacuum cleaner body 1, which accommodates an electrical motor for driving of a suction fan, a handle 2, a vacuum hose 3 and, in a rear portion of the body 1, two large wheels 4 of which only one is visible in the drawing. The vacuum cleaner has one further, small wheel, positioned on the underside in a forward portion of the vacuum cleaner and hence not visible in the drawing. The wheel 4 is formed in accordance with the invention and is illustrated in further detail in figs 2 to 4 in a cut perspective view, a cross section in parallel to the rotational axis and a cross section perpendicular to the rotational axis, respectively. As can be seen, the wheel 4 comprises a hub or rim 5, preferably made of rigid plastic, which is rotatably attached to the vacuum cleaner body. On the outer circumference of the hub 5, a gas cushion layer 6 is applied, which is manufactured of a transparent, resilient plastic. Finally, a tread sur- face layer 7 of a resilient plastic or rubber material, is applied on the outer circumference of the gas cushion layer 6.
The gas cushion layer 6 comprises an annular tube, which defines and encloses a continuous, circumferential gas cell 8 around the wheel. The tube is defined by wall portions of a transparent, resilient plastic material having a preferred thickness of about 1-3 mm. More precisely, the tube is defined by a radially inner wall portion 9, a radially outer wall portion 10 as well as axi- ally inner and outer side wall portions 11 and 12, respectively. Inside the tube are several, separate, reinforcing, confined gas cells 13 provided, each of which has the form of a tubular column extending from the radially inner wall portion 9 to the radially outer wall portion 10 of the tube. Also the cells 13 are formed of a transparent, resilient plastic material having a preferred thickness of about 1-3 mm and each encloses a con-
fined gas space. Seen in cross section the cells 13 have a more or less rectangular shape. In this way is formed confined compartments or cells 8, 13 and more precisely one annular cell 8 extending around the circumference of the wheel, and several confined, separate cells 13 distributed around the circumference of the wheel and positioned inside the annular cell 8. Suitably the cell 8 as well as the cells 13 may each be of the open type having at least one opening, which is not shown in the drawings, through the wall of the shell structure to allow air to escape from or enter into the cell during applying or revealing pressure to or from the cell, as described hereinbefore .
The tread surface layer 7 is thread onto the outer circumference of the gas cushion layer 6, which in its turn is thread onto the outer circumference of the hub 5. The tread surface layer 7, the gas cushion layer 6 and the hub 5 are attached to each other, suitably by means of adhesives .
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