Abstract:
The invention relates to a vacuum-cleaner nozzle for vacuuming an underlying surface, having a suction channel which opens out into a suction mouth. In order to form the vacuum-cleaner nozzle such that it has a relatively pronounced suction action for a sustained period of time, it is proposed according to the invention that the vacuum-cleaner nozzle comprises a lifting mechanism which interacts with the underlying surface and by means of which it is possible to change the distance of the suction mouth from the underlying surface on a periodic basis.

Description:
[0001]     This application is a continuation of international application number PCT/EP2005/001496 filed on Feb. 15, 2005.  
         [0002]     The present disclosure relates to the subject matter disclosed in international application number PCT/EP2005/001496 of Feb. 15, 2005 and German application number 10 2004 011 745.4 of Mar. 3, 2004, which are incorporated herein by reference in their entirety and for all purposes. 
     
    
     BACKGROUND OF THE INVENTION  
       [0003]     The invention relates to a vacuum-cleaner nozzle for vacuuming an underlying surface, having a suction channel which opens out into a suction mouth.  
         [0004]     Such vacuum-cleaner nozzles are usually connected to the free end of a suction hose or suction tube which is in flow connection with a suction subassembly for vacuuming the underlying surface. The suction subassembly produces a suction flow which, starting from the suction mouth, is channeled through the suction channel. In order to enhance the cleaning action, the suction flow can be intensified by the volume flow being increased. This requires the use of a more powerful suction subassembly, in which case there is a risk of the vacuum-cleaner nozzle sucking fast to the underlying surface for a sustained period of time. Utility Model DE 93 12 261 U1 has therefore proposed to interrupt the suction stream on a periodic basis by means of a flap valve disposed in the suction channel. When the valve is closed, the action of the suction subassembly causes an increase in the negative pressure between the suction subassembly and the valve. If the valve is opened, the increased negative pressure gives rise to an increased suction flow, so that an enhanced suction action can be achieved within this period of time without a more powerful suction subassembly having to be used and without there being any risk of the vacuum-cleaner nozzle sucking fast to the underlying surface for a sustained period of time.  
         [0005]     The disadvantage with such a configuration of a vacuum-cleaner nozzle, however, is that particles of dirt can settle in the region of the flap valve, and these may result in leakage and damage to the valve. This reduces the service life of the vacuum-cleaner nozzle and also the suction action thereof.  
         [0006]     It is an object of the present invention to develop a vacuum-cleaner nozzle of the type mentioned in the introduction such that its suction action can be enhanced for a sustained period of time.  
       SUMMARY OF THE INVENTION  
       [0007]     This object is achieved according to the invention, in the case of a vacuum-cleaner nozzle of the generic type, in that the vacuum-cleaner nozzle has a lifting mechanism which interacts with the underlying surface, it being possible, by means of the lifting mechanism, to change the distance of the suction mouth from the underlying surface on a periodic basis.  
         [0008]     The invention incorporates the idea that periodically changing the distance between the suction mouth and the underlying surface can achieve a periodic variation in the suction flow without there being any risk of leakage or damage to a valve element. By means of the lifting mechanism, which interacts with the underlying surface, the position of the suction mouth can be moved back and forth between two end positions on a periodic basis. In a first end position, the suction mouth assumes a position in which it is as close as possible to the underlying surface and, in a second end position, the suction mouth assumes a position in which it is spaced apart from the underlying surface to the maximum extent. In the first end position, the suction flow, in the region of the suction mouth, experiences a considerable loss in pressure on account of the small distance between the suction mouth and the underlying surface. With the operation of the suction subassembly remaining the same, this results in an increased negative pressure being established in the region between the suction subassembly and the suction mouth. If the suction mouth is then transferred into its second end position by means of the lifting mechanism, the distance between the suction mouth and the underlying surface increases, and this results in a considerable reduction in the loss in pressure of the suction flow in the region of the suction mouth, so that a pulsating suction flow forms overall, this resulting in a considerable increase in the suction action without valve elements which close the suction channel having to be used for this purpose.  
         [0009]     It may be provided, for example, that the suction mouth is bounded at least partially in the circumferential direction by a surround, for example by one or more crosspieces, it being possible for the surround to be raised from the underlying surface, and lowered onto the same, at least in certain regions by means of the lifting mechanism. Depending on the position assumed by the surround in relation to the underlying surface, it is possible to achieve a specified loss in pressure for the suction flow, and a periodic variation in distance, in turn, results in a pulsating suction flow being formed.  
         [0010]     It is advantageous if the suction mouth is mounted fixedly on a base plate of the vacuum-cleaner nozzle, it being possible for the base plate to be raised from the underlying surface, and lowered onto the same, by means of the lifting mechanism.  
         [0011]     In the case of a particularly preferred embodiment of the invention, the vacuum-cleaner nozzle has a supporting wheel, which can be rotated about an axis of rotation and can be positioned on the underlying surface, and the vacuum-cleaner nozzle can be pivoted back and forth about a pivot axis which is oriented parallel to, or coaxially in relation to, the axis of rotation. In the case of such a configuration, on account of the lifting mechanism interacting with the underlying surface, the vacuum-cleaner nozzle executes a periodic pivoting movement, the supporting wheel supporting the vacuum-cleaner nozzle on the underlying surface and the axis of rotation of the supporting wheel defining a pivot axis of the vacuum-cleaner nozzle. The pivoting movement of the vacuum-cleaner nozzle results in a periodic variation in distance of the suction mouth and is brought about by the lifting mechanism.  
         [0012]     In order to ensure that, despite the periodic variation in distance of the suction mouth, the underlying surface is cleaned uniformly, it is advantageous if the width of the suction mouth in the operating direction of the vacuum-cleaner nozzle corresponds at least to the distance covered by the vacuum-cleaner nozzle at a speed of 0.5 m/s along the underlying surface within a raising/lowering cycle of the lifting mechanism. The speed of 0.5 m/s corresponds to a standard speed at which the vacuum-cleaner nozzle is usually moved along the underlying surface by the user. If the width of the suction mouth in the operating direction of the vacuum-cleaner nozzle is greater than or equal to the distance which is covered at the abovementioned standard speed within a raising/lowering cycle of the lifting mechanism, then it is ensured that each region of the underlying surface is also covered by an enhanced suction flow and there are no regions of the underlying surface which are subjected just to a minimal suction flow.  
         [0013]     It is of particular advantage if the width of the suction mouth corresponds at least to 1.5 times the distance which is covered by the vacuum-cleaner nozzle at a speed of 0.5 m/s along the underlying surface within a raising/lowering cycle of the lifting mechanism. It may thus be provided, for example, that the lifting mechanism changes the distance of the suction mouth from the underlying surface on a periodic basis at a frequency of approximately 25 Hz and the width of the suction mouth is at least 20 mm.  
         [0014]     In the case of a preferred embodiment, the lifting mechanism can be switched on and off. This makes it possible for the lifting mechanism to be switched on, and accordingly for the distance of the suction mouth from the underlying surface to be varied, only when an enhanced suction action is desirable for cleaning the underlying surface, for example in the case of a carpet. If the vacuum-cleaner nozzle is used for a merely lightly soiled underlying surface or for a hard surface, the cleaning of which does not require any enhanced suction action, then the lifting mechanism can be switched off.  
         [0015]     It may be provided that the lifting mechanism can be optionally switched on and off by the user. This makes it possible for the user to switch the lifting mechanism on or off manually depending on the degree of soiling of the underlying surface.  
         [0016]     In many cases, the vacuum-cleaner nozzle has a bristle-covered rim which can be moved back and forth between two different positions by means of an actuating device, so that, for cleaning a hard surface, the bristle-covered rim can be extended out of a housing of the vacuum-cleaner nozzle and, for cleaning a carpet, it can be retracted into the housing. It is advantageous here if the lifting mechanism is coupled to the actuating device of the bristle-covered rim. This makes it possible to switch on the lifting mechanism by means of the actuating device for cleaning a carpet, whereas it is switched off for cleaning a hard surface.  
         [0017]     The suction action is more pronounced the greater the difference between the minimum and maximum distances of the suction mouth from the underlying surface. In the case of a large difference between the minimum and maximum distances, that is to say in the case of a large displacement of the suction mouth, a suction flow which pulsates to a pronounced extent and results in an enhanced suction action is established. If, in contrast, the difference between the minimum distance and the maximum distance of the suction mouth from the underlying surface is reduced, then the pulsation of the suction flow is reduced. It is thus advantageous if it is possible to change the extent of the periodic variation in distance, i.e. of the displacement of the suction mouth. This makes it possible to adapt the suction action of the vacuum-cleaner nozzle to the degree of soiling of the underlying surface.  
         [0018]     No more specific details have been given up until now regarding the configuration of the lifting mechanism. It is advantageous if the lifting mechanism has at least one rotatable rolling element which acts on the underlying surface and is coupled to the suction mouth, for example is connected fixedly to the suction mouth, it being possible for the suction mouth to be raised from the underlying surface, and lowered onto the same, by means of the rolling element. If the vacuum-cleaner nozzle is moved along the underlying surface, then the rolling element, which acts on the underlying surface, is made to rotate and, since the rolling element is coupled to the suction mouth, rolling movement of the rolling element can cause the suction mouth to move back and forth in the direction of the underlying surface and in the direction away from the underlying surface. The distance of the suction mouth from the underlying surface can thus be changed on a periodic basis by means of the rolling element in a constructionally simple manner.  
         [0019]     It is advantageous if the rolling element is mounted in an exchangeable manner on a housing of the vacuum-cleaner nozzle, for example such that it can be connected in a releasable manner, in particular latched, thereto. This makes it possible, depending on the nature of the underlying surface, to use different rolling elements which differ, for example, in the extent of the back and forth movement of the suction mouth brought about by them or also in the frequency of this movement.  
         [0020]     The rolling element is preferably mounted eccentrically because it is thus possible for the rolling movement of the rolling element to be translated into a back and forth movement of the suction mouth in a constructionally simple manner.  
         [0021]     It may also be provided that the rolling element is of non-round configuration, for example in the form of a rolling cam which is supported on the underlying surface and raises the vacuum-cleaner nozzle, and then lowers it again, at least in the region of the suction mouth.  
         [0022]     It is advantageous if the rolling element has a contour in the form of a polygon, in particular of a pentagon.  
         [0023]     As an alternative, it may be provided that the rolling element has a star-shaped contour. The rolling element may, for example, be in the form of a star wheel, preferably of a star wheel with five arms or points.  
         [0024]     It may be provided that the rolling element is configured as a wheel or as a roller or brush. It is advantageous here if the width of the rolling element corresponds approximately to the width of a classic thread-lifting means.  
         [0025]     As an alternative, it is possible to use a rolling element, the width of which corresponds substantially to the width of the vacuum-cleaner nozzle.  
         [0026]     It may also be provided that use is made of a plurality of rolling elements which are connected fixedly to one another and are distributed over the width of the vacuum-cleaner nozzle. The vacuum-cleaner nozzle can thus be prevented from tilting laterally in a constructionally simple manner.  
         [0027]     The rolling element exhibits slip in relation to the underlying surface as it rolls. It is advantageous if the contour of the rolling element is non-symmetrical because it is thus possible to ensure, in a constructionally simple manner, that the rolling element has different slippage behavior depending on whether the vacuum-cleaner nozzle is moved in the forward or in the rearward direction. This, in turn, ensures that the suction mouth, which is driven to perform a back and forth movement by the rolling element, covers all regions of the underlying surface, even when it is at a small distance from the underlying surface, so that a uniform cleaning action along the underlying surface is achieved.  
         [0028]     In the case of a preferred embodiment of the vacuum-cleaner nozzle according to the invention, the contour of the rolling element is star-shaped and has a plurality of arms or points with in each case two flanks running toward one another, the two flanks being inclined differently in relation to the radial direction of the rolling element. The different flank inclination in the case of a star-shaped contour ensures different slippage of the rolling element during forward and rearward movement of the vacuum-cleaner nozzle. The different slippage, in turn, means that, during forward and rearward movement of the vacuum-cleaner nozzle, different positions of the rolling element are established in relation to a specific region of the underlying surface, and thus different positions of the suction mouth are also established in relation to the underlying surface. This ensures that each point of the underlying surface is also cleaned with an increased suction flow.  
         [0029]     The rolling element preferably has a friction-enhancing covering. It may thus be provided, for example, that the rolling element is coated with a rubber or latex covering or with a felt. The friction-enhancing covering ensures that movement of the vacuum-cleaner nozzle along the underlying surface results in a rotary movement of the rolling element and thus in a variation in distance of the suction mouth.  
         [0030]     It is of particular advantage if, by way of the friction-enhancing covering, the frictional behavior of the rolling element as it rolls along the underlying surface in the operating direction of the vacuum-cleaner nozzle differs from that as it rolls counter to the operating direction, because this makes it possible to ensure different slippage during forward and rearward movement of the vacuum-cleaner nozzle.  
         [0031]     It may be provided, for example, that the friction-enhancing covering is structured and subjects the underlying surface to a frictional force which is dependent on the rolling direction of the rolling element.  
         [0032]     The vacuum-cleaner nozzle preferably has a supporting wheel which can be positioned on the underlying surface, the rolling element being disposed between the supporting wheel and the suction mouth, as seen in the operating direction of the vacuum-cleaner nozzle. As an alternative, it may be provided that the rolling element is positioned upstream of the suction mouth, as seen in the operating direction.  
         [0033]     It is advantageous if the vacuum-cleaner nozzle has at least one thread-lifting means, the rolling element being disposed between the suction mouth and the thread-lifting means. It is of particular advantage if the rolling element and the suction mouth are positioned between two thread-lifting means.  
         [0034]     As has already been explained, it has proven to be advantageous if the width of the suction mouth corresponds to approximately 20 mm. It has been found that such a configuration of the suction mouth allows reliable and uniform cleaning of the underlying surface.  
         [0035]     It is advantageous if it is possible to change the position of the rolling element in relation to the underlying surface. This makes it possible for the user to render the rolling element inoperative by placing the rolling element in a position in which it does not come into contact with the underlying surface. If, in contrast, the rolling element is to be made operative, then it is transferred by the user into a position in which it is much closer to the underlying surface. It may thus be provided that the rolling element is mounted such that it can be adjusted obliquely or perpendicularly in relation to the underlying surface.  
         [0036]     It is of particular advantage if the position of the rolling element is coupled to the position of an adjustable bristle-covered rim of the vacuum-cleaner nozzle. The bristle-covered rim is only used for cleaning a hard surface; for cleaning a carpet, it is moved to be at a distance from the carpet. Conversely, the rolling element can be moved closer to the carpet, whereas, for cleaning a hard surface, it can be moved a distance away from the hard surface. This results in the rolling element only being used for cleaning a carpet, that is to say that it is only for cleaning a carpet that the distance of the suction mouth from the underlying surface is changed on a periodic basis.  
         [0037]     It may also be provided that the axial position of the rolling element, that is to say the height of the latter in relation to the suction mouth, cannot be changed. If use is made, in such a case, of a bristle-covered rim which can be changed in position, this results, depending on the position of the bristle-covered rim, in the rolling element coming into mechanical contact with the underlying surface and thus being able to become operative, or else, on account of the bristle-covered rim, the rolling element is kept at a distance from the underlying surface and thus remains inoperative.  
         [0038]     It is of particular advantage if the rotary movement of the rolling element can be detected visually or acoustically by the user. It is thus possible to provide, for example, a viewing window through which the user can see the rolling element. It is possible here for the viewing window to comprise a transparent covering with colored marking over which the rolling element passes as it rotates, so that a kind of “stroboscope effect” is established and the rotation of the rolling element is represented to enhanced effect. As an alternative, and/or in addition, the rotary movement of the rolling element can be used to produce a sound.  
         [0039]     As has been explained above, the rotary movement of the rolling element along the underlying surface results in a back and forth movement of the suction mouth. In the case of a preferred embodiment, this movement can be detected by the user by touch.  
         [0040]     However, it may also be provided that the vacuum-cleaner nozzle has damping elements, so that mechanical vibrations of the vacuum-cleaner nozzle can only be transmitted to a small extent to a suction tube or a suction hose which can be connected to the vacuum-cleaner nozzle.  
         [0041]     Instead of using a rolling element, it is provided, in the case of an advantageous embodiment of the invention, that the lifting mechanism comprises a turbine wheel which can be subjected to the action of a suction flow, is mounted such that it can be rotated about an axis of rotation and the center of gravity of which is disposed at a distance from the axis of rotation, and a supporting element acting on the underlying surface at a distance from the axis of rotation, as seen in the operating direction. In the case of such a configuration, the raising and lowering movements of the suction mouth are brought about by the rotation of the eccentric turbine wheel, which can be made to rotate by the suction flow. The turbine wheel has a center of gravity which is disposed at a distance from its axis of rotation and, when the turbine wheel rotates, this results in an unbalance, so that the vacuum-cleaner nozzle is subjected to forces of inertia in the bearing region of the turbine wheel. Since a supporting element which can be positioned on the underlying surface, for example a supporting wheel, is positioned at a distance from the axis of rotation of the turbine wheel, the unbalance of the turbine wheel results in a periodic pivoting movement of the vacuum-cleaner nozzle such that the suction mouth is raised and lowered on a periodic basis, while the supporting element assumes a constant position in relation to the underlying surface.  
         [0042]     It is advantageous if the turbine wheel is disposed within the suction channel and does not completely fill the suction-channel cross-section, because this ensures that the suction flow which is channeled through the suction channel is not adversely affected to any significant extent by the turbine wheel.  
         [0043]     The turbine wheel is preferably disposed in an end portion of the suction channel which opens out into the suction mouth. It is particularly advantageous if the turbine wheel is positioned above the suction mouth.  
         [0044]     The configuration of the turbine wheel with an unbalance is achieved, in the case of a preferred embodiment, in that the turbine wheel has turbine blades of different masses. It may thus be provided, for example, that the turbine wheel has four turbine blades oriented at an angle of approximately 90° in relation to one another, although one turbine blade is of a considerably greater mass than the other turbine blades.  
         [0045]     In order to it to be possible for the action of the turbine wheel to be switched on and off optionally, it is provided, in the case of an advantageous embodiment of the invention, that the turbine wheel can be arrested. As an alternative, it may be provided that the turbine wheel can be introduced into the suction channel and removed therefrom, so that, in accordance with the position of the turbine wheel, it is possible for a periodic variation in distance of the suction mouth to be switched on and off.  
         [0046]     It may be provided that the rotatability of the turbine wheel is coupled to the position of a bristle-covered rim of the vacuum-cleaner nozzle. The bristle-covered rim is only used for cleaning a hard surface and, in this case, the rotatability of the turbine wheel can be blocked. If, instead, the bristle-covered rim is deactivated, then the turbine wheel can be activated at the same time because, in this case, the vacuum-cleaner nozzle is used for cleaning a carpet, in the case of which it is advantageous if an enhanced suction action can be achieved.  
         [0047]     It is advantageous if the rotary movement can be detected by the user visually, acoustically and/or by touch. It may thus be provided, for example, that the vacuum-cleaner nozzle has a viewing window through which the user can see the turbine wheel. The viewing window may carry a transparent covering with a colored marking over which the turbine blades of the turbine wheel pass. As an alternative, and/or in addition, the turbine wheel can produce a sound which makes the user aware that the turbine wheel is rotating.  
         [0048]     As explained in the introduction, the periodic change in distance of the suction mouth from the underlying surface results in an enhanced suction action, on account of which an improved cleaning action can be achieved. The cleaning action is enhanced further, in the case of a particularly advantageous embodiment, by the suction mouth being bounded at least partially in the circumferential direction by a surround which forms that region of the vacuum-cleaner nozzle which projects furthest in the direction of the underlying surface. The surround of the suction mouth thus forms a projecting region by means of which the underlying surface can be cleaned mechanically when the suction mouth assumes the position in which it is minimally spaced apart from the underlying surface. In this position, the underlying surface is treated mechanically by the suction-mouth surround. For cleaning a carpet, the surround penetrates into the pile of the carpet, so that this is mechanically scrubbed. The cleaning action can thus be enhanced to a considerable extent, but without this being associated with the disadvantage of the user having to apply increasing pushing force in order to move the vacuum-cleaner nozzle; rather, the periodic change in distance of the suction mouth, and thus also of the surround, which bounds the suction mouth at least partially in the circumferential direction, ensures that, despite the mechanical treatment of the underlying surface, the pushing forces which are necessary in order to move the vacuum-cleaner nozzle can be kept to a low level.  
         [0049]     According to a preferred embodiment, the suction-mouth surround forms the bearing surface for the vacuum-cleaner nozzle on the underlying surface. In comparison with known vacuum-cleaner nozzles, the vacuum-cleaner nozzle according to the invention thus has a small bearing surface. This results in it being possible for the vacuum-cleaner nozzle to penetrate to a more pronounced extent into a carpet. The increased pushing forces which occur here are reduced by the action of the lifting mechanism, which interacts with the underlying surface and causes the suction mouth to be raised and lowered cyclically. Despite an improved cleaning performance, it is thus the case that the pushing forces are not increased in relation to conventional vacuum-cleaner nozzles.  
         [0050]     It is advantageous if the surround of the suction mouth forms a crosspiece. It may be provided here that, in relation to the operating direction of the vacuum-cleaner nozzle, use is made of a front crosspiece and a rear crosspiece which extend over the entire width of the vacuum-cleaner nozzle substantially at a constant distance from one another.  
         [0051]     It is advantageous if the vacuum-cleaner nozzle has at least one thread-lifting means mounted on a base plate, the surround projecting beyond the thread-lifting means in the direction of the underlying surface and having no interruption in its region which is adjacent to the thread-lifting means. It has been found that it is thus possible to enhance the cleaning action of the vacuum-cleaner nozzle.  
         [0052]     The following description of preferred embodiments of the invention serves for a more detailed explanation in conjunction with the drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0053]      FIG. 1  shows a basic illustration of a first embodiment of a vacuum-cleaner nozzle according to the invention at a minimum distance from an underlying surface;  
         [0054]      FIG. 2  shows a basic illustration of the vacuum-cleaner nozzle according to  FIG. 1  at a maximum distance from the underlying surface;  
         [0055]      FIG. 3  shows a bottom view of the vacuum-cleaner nozzle according to  FIGS. 1 and 2 ;  
         [0056]      FIG. 4  shows a basic illustration of a second embodiment of a vacuum-cleaner nozzle according to the invention at a minimum distance from the underlying surface; and  
         [0057]      FIG. 5  shows a basic illustration of the vacuum-cleaner nozzle according to  FIG. 4  at a maximum distance from the underlying surface. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0058]     In FIGS.  1  to  3 , there is illustrated, schematically, a first embodiment of a vacuum-cleaner nozzle according to the invention which is designated as a whole by the reference numeral  10  and can be displaced along an underlying surface, in the embodiment illustrated along a carpet  12 . The vacuum-cleaner nozzle  10  comprises a housing  14  with a suction channel  16  which passes through the housing  14  and opens out into a suction mouth  18 , which is disposed on a base plate  20  of the housing  14  and is directed toward the carpet  12 .  
         [0059]     The suction mouth  18  is bounded in a circumferential direction by a surround which, in relation to an operating direction  22  of the vacuum-cleaner nozzle  10 , has a front transverse crosspiece  24  and a rear transverse crosspiece  25 , which extend virtually over the entire width of the vacuum-cleaner nozzle  10 , at a constant spacing from one another, and are connected integrally to one another at the ends via longitudinal crosspieces  26 ,  27 .  
         [0060]     At its end which is directed away from the base plate  20 , the suction channel  16  forms a connector  29  for connection to a suction tube, which is known per se and is therefore not illustrated in the drawing, or a suction hose of a vacuum cleaner. The latter has a suction subassembly (not illustrated), with the aid of which a suction flow which leads through the suction channel  18  can be achieved.  
         [0061]     Disposed on the underside of the base plate  20  upstream and downstream of the surround of the suction mouth  18 , as seen in the operating direction  22 , are two thread-lifting means  31 ,  32  which cause threads to be picked up from the underlying surface which is to be vacuumed, and which may be configured, for example, in the form of a plastic strip which is covered with a bristly velours in the direction of the carpet  12 .  
         [0062]     In its rearward region, in relation to the operating direction  22 , the vacuum-cleaner nozzle  10  has a supporting wheel  34  which is mounted on the housing  14  such that it can be rotated about an axis of rotation  35  which is oriented at right angles to the operating direction  22 . For support on the carpet  12 , the vacuum-cleaner nozzle  10  also has two supporting rollers  37 ,  38  which are mounted in a rotatable manner on the housing  14  and are disposed approximately level with the free ends of the transverse crosspieces  24 ,  25 , downstream of the rear transverse crosspiece  25  as seen in the operating direction  22 .  
         [0063]     As is clear from  FIGS. 1 and 2 , the transverse crosspieces  24 ,  25  project beyond the thread-lifting means  31 ,  32  and the circumference of the supporting wheel  34  in the direction of the carpet  12 . Those peripheral regions of the transverse crosspieces  24  and  25  which are directed toward the carpet  12  form that region of the vacuum-cleaner nozzle  10  which projects furthest in the direction of the carpet  12 , that is to say the transverse crosspieces  24 ,  25  form the bearing surface for the vacuum-cleaner nozzle  10  on the carpet  12  and penetrate into the pile  40  of the carpet  12 , so that the latter is treated mechanically by the transverse crosspieces  24  and  25 .  
         [0064]     In order to clean the carpet  12 , the vacuum-cleaner nozzle  10  is displaced back and forth in the operating direction  22  and the carpet  12  is vacuumed. At the same time, the vacuum-cleaner nozzle  10  is pivoted back and forth on a periodic basis about the axis of rotation  35  of the support wheel  34 , so that the distance which the suction mouth  18  assumes from the carpet  12  is increased and decreased on a periodic basis, as is illustrated in  FIGS. 1 and 2 . In order to produce the periodic movement of the vacuum-cleaner nozzle  10 , use is made of a lifting mechanism which, in the exemplary embodiment illustrated in FIGS.  1  to  3 , is formed as a non-round rolling element which is mounted in a rotatable manner on the housing  14  and is in the form of a star wheel  42  which acts on the carpet  12  and is made to rotate as the vacuum-cleaner nozzle  10  is displaced. The star wheel  42  has the contour of a five-pointed star which is of non-symmetrical configuration such that the five points  45 ,  46 ,  47 ,  48  and  49  of the star have in each case two side flanks  43 ,  44  which run toward one another and are inclined differently in relation to the radial direction of the star wheel  42 . The points  45 ,  46 ,  47 ,  48  and  49  of the star wheel  42  are rounded at the ends, so that they each form a minimum bearing surface for the star wheel  42  on the carpet  12 , which ensures that the star wheel  42  only penetrates to a slight extent into the pile  40  of the carpet  12 .  
         [0065]     On account of the non-round configuration of the star wheel  42 , the rolling movement of the latter along the carpet  12  results in periodic raising and lowering of the front region of the vacuum-cleaner nozzle  10 , as seen in the operating direction  22 , that is to say of the suction mouth  18  in particular. If the latter assumes a position in which it is close to the carpet  12 , as illustrated in  FIG. 1 , then an increased flow resistance forms in the region of the surround, this resulting in a strengthened negative pressure within the suction channel  16 . As the star wheel  42  rolls further, the vacuum-cleaner nozzle  10  is raised in the region of the suction mouth  18 , as is illustrated in  FIG. 2 . This results in a reduced flow resistance in the region of the surround, so that ambient air can be taken into suction channel  16 . The continuous periodic raising and lowering movement of the suction mouth  18  thus results in a pulsating suction flow within the suction channel  16 , and this allows the suction action of the vacuum-cleaner nozzle  10  to be enhanced to a considerable extent.  
         [0066]     The axial position of the star wheel  42  can be changed by means of an adjusting member which is known per se and is therefore not illustrated in the drawing, for example a connecting rod or a pivot lever, so that the star wheel  42  can be moved to a distance away from the carpet  12 , so that it becomes inoperative. Conversely, the star wheel  42  can also be moved closer to the carpet  12  by means of the adjusting member, this resulting in an increased displacement, that is to say an increased movement amplitude of the suction mouth  18  as it moves back and forth.  
         [0067]     The star wheel  42  may be covered by a friction-enhancing covering, in particular by a bristly velours as is used for the thread-lifting means  31 ,  32 .  
         [0068]     The periodic raising and lowering of the suction mouth  18  and of the front and rear transverse crosspieces  24 ,  25  also ensures that, although mechanical treatment of the pile  40  of the carpet  12  can take place, there is no need for the user of the vacuum-cleaner nozzle  10  to apply any increased pushing force in order to displace the vacuum-cleaner nozzle  10  along the carpet  12 .  
         [0069]      FIGS. 4 and 5  illustrate a second embodiment of a vacuum-cleaner nozzle according to the invention, which is designated as a whole by the reference numeral  55 . This is a similar configuration to the vacuum-cleaner nozzle  10  which has been explained above with reference to FIGS.  1  to  3 . For identical components, use is thus made of the same reference numerals as were used in FIGS.  1  to  3 . To avoid repetition, reference is made in this respect to the explanations which have been given above.  
         [0070]     The vacuum-cleaner nozzle  55  differs from the vacuum-cleaner nozzle  10  in that the lifting mechanism used, rather than being a rolling element in the form of a star wheel, is formed by a turbine wheel  57  which is disposed within the suction channel  16  and has four turbine blades  58 ,  59 ,  60  and  61  which are oriented in a mirror-symmetrical manner in relation to one another and at an angle of 90° in relation to one another in each case, the turbine blade  58  having a considerably greater mass than the turbine blades  59 ,  60  and  61 . This results in the center of gravity of the turbine wheel  57 , which is mounted such that it can be rotated freely about an axis of rotation  63 , being disposed at a distance from the axis of rotation  63 . The turbine wheel  57  thus forms an unbalance, and a rotation of the turbine wheel  57  as is brought about by the suction flow drawn through the suction channel  16  results in the front region of the housing  14 , as seen in the operating direction  22 , being raised and lowered on a periodic basis, while the rearward region of the housing is supported on the floor  12  by means of the supporting wheel  34 . The periodic raising and lowering of the front region of the housing  14 , and thus of the suction mouth  18  in particular, results, as has been explained above, in a pulsating suction flow since the flow resistance in the region of the surround changes on a periodic basis. An enhanced suction action can thus be achieved in a constructionally simple manner by using the unbalanced turbine wheel  57  in combination with the supporting wheel  34  supported on the carpet  12 . At the same time, using the turbine wheel  57  makes it possible to form the front and rear transverse crosspieces  24 ,  25  such that they project beyond the thread-lifting means  31 ,  32  and the supporting wheel  34  in the direction of the carpet  12  and treat the pile  40  of the carpet  12  mechanically without this nevertheless requiring an increased pushing force in order to displace the vacuum-cleaner nozzle  10 .