Patent Application
20110239397
The present invention relates to a suction unit for an autonomous vacuum cleaner. Furthermore, the invention relates to an autonomous vacuum cleaner.
In EP0803224 a suction unit is integrated with a fan unit and a dust chamber, and all components are accommodated in the same housing. In EP0803224 the outlet of the nozzle for removing particles from a surface to be treated communicates with a chamber accommodating a dust container. The chamber is connected to a fan unit that provides an underpressure. The nozzle is mounted to the chassis by an arm that is supported by a ball joint so that it can pivot with relation to the housing. During movement of the vacuum cleaner across the floor, the nozzle rests by its own weight on the floor and floats on the floor because of the flexible support at the ball joint.
A problem with known suction units is that when the nozzle is completely sealed from the outside atmosphere, the underpressure in the nozzle increases while the nozzle gets stuck on the surface to be treated. This occurs especially when cleaning soft floors such as carpets. The problem is already well known for traditional non-autonomous vacuum cleaners. For autonomous vacuum cleaners the consequences generally are worse, since it can lead to a device that gets inoperable, without a user noticing it. The enhanced underpressure results in a normal force that presses the nozzle down to the cleaning surface. It could then occur that the power of the driving system is insufficient to move the suction unit or the vacuum cleaner in order to overcome the increased downward force. This can result in the device getting immobile. This is in particular true when the suction unit is relatively small, since in that case a drive system normally will only have limited power.
It is an object of the present invention to provide a suction unit that reduces the abovementioned disadvantage.
To achieve this object, the present invention provides an autonomous suction unit according to claim 1.
With this suction unit the problem of restricted mobility is avoided or at least reduced in that the coupling means exert a force away from the surface to be treated whenever the underpressure in the interior space of the nozzle increases. If the nozzle gets stuck, the underpressure in the interior space will increase due to the opening being sealed from the environment. This results in an increased normal force acting on the nozzle. This force will at least partially be reduced by the coupling means that exert a counterforce away from the surface to be treated.
Any enhanced downward force on the nozzle due to increasing pressure therein can effectively be reduced in this manner, while driving the suction unit gets easier. An additional advantage is that the force exerted by the coupling means results in improved traction force of the driving system on the surface to be treated, as the force exerted by the coupling means will be transferred so as to increase the downward force acting on the chassis. This will be explained in more detail below.
According to a preferred embodiment, the coupling means comprises a bellows interposed between the chassis and the nozzle, the bellows having an interior space that communicates with the interior space of the nozzle. This provides a simple and effective construction for the coupling means. When the underpressure in the nozzle increases, the underpressure in the bellows will increase also. Or, in other words, the pressure in the bellows drops. Accordingly, the bellows will contract and exert a counterforce on the nozzle that is directed away from the surface to be treated. A larger underpressure in the nozzle results in a larger underpressure in the bellows and hence in a larger force that is exerted on the nozzle.
Another simple and effective construction is the suction unit according to claim 3.
According to another preferred embodiment, the coupling means comprises a linear actuator interposed between the chassis and the nozzle for moving the nozzle with relation to the chassis in a substantially vertical direction. It is especially preferred that a pressure sensor is provided in the interior space, the sensor giving an output signal, the linear actuator being configured to move the nozzle depending on the output signal of the pressure sensor. This has the advantage that the force that is exerted on the nozzle can be applied in an active manner, which results in a precise control of the forces acting on the nozzle.
Furthermore, it is preferred that the coupling means comprises an arm that is pivotally mounted to the chassis by means of a pivot pin or a pivot axis and extends substantially parallel with relation to the surface to be treated, the nozzle being supported by the arm. This provides a simple and effective construction. It is especially preferred that the nozzle is provided at a front part of the chassis and the pivot pin is provided at a rear part of the chassis, the pivot pin being provided low on the chassis, so that the distance between the pivot pin and the surface to be treated is small during operating conditions. This embodiment ensures that the arm extending between the nozzle and the pivot pin is relatively long. In combination with the fact that the pivot pin is close to a surface to be treated, this results in a friction force acting on a forward moving nozzle, leading to a relatively small (downward) normal force acting on the nozzle. Preferably, a support member is provided at the front end of the chassis. This member supports the arm to guarantee a minimum distance between the nozzle and the surface to be cleaned. Favourable distances and dimensions are given in claims 8 and 9, respectively. This will be explained in more detail below.
According to another preferred embodiment, the drive system comprises a set of wheels provided at opposite sides of the chassis, wherein the wheels on either side of the chassis can be separately operated. This allows easy turning of the suction unit by driving the wheels at one side of the chassis only.
The present invention also relates to an autonomous vacuum cleaner comprising a suction unit according to any one of the aforementioned embodiments, the vacuum cleaner further comprising a dust chamber, and a fan unit that communicates with the dust chamber, the fan unit communicating with the outlet for creating an underpressure in the interior space of the nozzle during operating conditions. Preferred embodiments are given in claims 12 to 14.
The present invention can in particular be advantageously used for the arrangement as described in WO 02/074150. This document discloses an autonomous cleaner having a self-propelling moving suction unit or cleaning head that is connected to a main module or vacuum fan module that is also self-propelling and holds a dust container and a fan unit as well as the larger part of the cleaner's navigation and control system. Because the size of the suction unit is relatively small, at least compared to the main module, the maximum power of the drive system therein will be relatively small. Since the suction power generated in the main module typically will be comparable to that of conventional vacuum cleaners, there is an enhanced risk of the suction unit getting stuck to the floor. The maximum power of the drive system then can be insufficient to overcome this. Moreover, the weight of such a suction unit will be relatively low. Accordingly, the normal force acting on the wheels is relatively low, which leads to an enhanced risk of spinning wheels.
The present invention can also be applied in an integrated autonomous vacuum cleaner according to claim 12. EP0803224 describes an integrated autonomous vacuum cleaner. In these vacuum cleaners all components are integrated in a unitary self-propelling unit.
The term ‘bellows’ within this specification is used to indicate any deformable container having at least one opening that is able to expand or contract when the pressure in the container, respectively, increases or decreases.
Embodiments of the present invention will now be described by way of example and with reference to the accompanying drawing, wherein;
At a front part of the chassis a nozzle 7 is provided. The nozzle has an interior space defining an opening 9 facing the surface to be treated 11 when the suction unit is operational. The interior space communicates with an outlet 13, while at another side it results in the opening 9. The outlet 13 is meant to communicate with suction means or a fan unit when the suction unit is operated. One can for example connect a hose assembly at one side to the outlet at while the other side is connected to a unit accommodating a dust chamber and a fan unit. By operating the fan unit an under pressure arises in the interior space of the nozzle which enables picking up particles and dust from the surface 11 to be cleaned.
Alternatively, a fan unit and for example a dust bin and a filter element may be provided in one unitary housing accommodating all components of the vacuum cleaner.
The nozzle is carried by an arm 15 that is pivotable with relation to the chassis 5 around a pivot pin 17. The arm 15 extends in the chassis, which is indicated with dotted lines. The pivot pin preferably lies behind both wheels at a rear part of the chassis. The arm preferably also accommodates the air path that establishes the communication between the nozzle and the outlet. The air path can be formed by a tube or a hose or a combination thereof.
The opening 9 or lower edge of the nozzle 7 normally rests a few millimeters above the surface 11. This allows surrounding air to be sucked into the nozzle and thus pick up dust particles. In the case of hard floors this condition is always satisfied. In the case of soft floors, however, a nozzle can be sealed-off from the surrounding air, for example by numerous fibers. When this takes place the pressure in the interior space of the nozzle drops while ambient air pressure presses the nozzle down.
A bellows 19 is interposed between an extension 21 of the chassis 5 and the nozzle 7. The bellows has an interior part 23 that communicates with the interior part of the nozzle via one or more openings (not shown) that are provided in a plate between both parts. The plate may also be an integral part of the bellows 19.
Due to the aforementioned openings, the underpressure in the interior space of the bellows will increase whenever the underpressure in the interior space of the nozzle increases. As mentioned above, this mainly occurs when the nozzle rests on a soft floor with fibers that largely shut off the nozzle from the ambient air. Due to the action of a fan unit, the pressure of the air surrounding the nozzle will be larger than the pressure in the nozzle, as a result of which the nozzle is pressed down. In the drawing this is indicated by force Fa. When the underpressure in the bellows increases, it will contract. Upon contracting, the bellows exerts a counter force Fb on the nozzle that is directed away from the surface to be treated. This force reduces the total normal force acting on the nozzle and thus reduces the sealing action of the nozzle. In this manner a new balance will automatically be established wherein the force that is exerted by the bellows compensates or at least partly compensates for the downward force on the nozzle. Hence, the problem of the nozzle getting stuck to the surface is restricted.
The counter force Fb leads to improved traction of the wheels. As the bellows is attached to an extension 21 of the chassis 5, the force generated by the bellows will lead to a counter force acting on the chassis, which via the ‘action is minus reaction principle’ ultimately leads to an increased normal force acting on wheels 3. In
A supporting member 27 is provided at the chassis 5 to support the arm 15, while a minimum distance between the opening 9 and the surface 11 is guaranteed. Preferably, this distance is approximately 2.5 mm.
Preferably, the nozzle 7 has a slanting edge 25 to facilitate lifting of the nozzle when it encounters for example a doorstep.
The nozzle and the chassis may be accommodated in a housing, which is not shown in
The magnitude of the force that is exerted on the nozzle by the bellows will mainly depend on the ratio between the area of the nozzle opening and the cross-sectional area of the bellows. Enlarging the effective area of the bellows in relation to the cross-sectional area of the nozzle leads to a larger counter force acting on the nozzle.
F
w
×R
p
=F
a
×R
a.
Therefore, by having an arm that is relatively long and by keeping the distance Rp relatively low, the resulting normal force acting on the nozzle will be relatively low. A relatively long arm is obtained by providing the nozzle at a front part of the chassis and providing the pivot pin at a rear part of the chassis. The distance Rp is kept relatively low by providing the pivot pin low on the chassis.
Preferably, a rotating brush is provided in the interior space of the nozzle. This brush is driven by an electromotor provided behind the nozzle.
Instead of moving by means of the pivoting arm, the nozzle may also be arranged so as to move with relation to the chassis by means of guiding means, such as roller bearings provided at one or more sides of the nozzle facing the chassis.
It will be clear to a person skilled in the art that the scope of the present invention is not limited to the examples discussed in the foregoing, but that several amendments and modifications thereof are possible without deviating from the scope of the present invention as defined in the attached claims. While the present invention has been illustrated and described in detail in the figures and the description, such illustration and description are to be considered illustrative or exemplary only, and not restrictive. The present invention is not limited to the disclosed embodiments. Variations to the disclosed embodiments can be understood and effected by a person skilled in the art in practicing the claimed invention, from a study of the figures, the description and the attached claims. In the claims, the word “comprising” does not exclude other steps or elements, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope of the present invention.
The invention relates to a suction unit for a vacuum cleaner and to a vacuum cleaner. The suction unit comprises a drive system for driving the suction unit on a surface to be treated; a chassis supporting the drive system; a nozzle for removing particles from a surface to be treated, which nozzle is configured to move with relation to the chassis in a direction away from the surface to be treated, the nozzle having an interior space defining an opening facing the surface to be treated; and an outlet communicating with the interior space, the outlet being arranged for communication with a fan unit during operating conditions. The suction unit further comprises coupling means for coupling the nozzle to the chassis, wherein the coupling means are arranged to exert a force that is directed away from the surface to be treated when the underpressure in the interior space increases. In this manner the problem of the suction unit getting stuck on the floor can be overcome or at least reduced. Furthermore the traction of the drive system can be improved. An autonomous vacuum cleaner according to the invention comprises such a suction unit and further comprises a dust chamber, and a fan unit that communicates with the dust chamber, the fan unit communicating with the outlet for creating an underpressure in the interior space of the nozzle during operating conditions.
| Number | Date | Country | Kind |
|---|---|---|---|
| 07114669.0 | Aug 2007 | EP | regional |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/IB2008/053304 | 8/18/2008 | WO | 00 | 6/20/2011 |
