Abstract:
An overload coupling is provided for the limited transfer of torque in a floor cleaning device. A drive element and a driven element are arranged concentrically to one another, thereby forming an intermediate space. The intermediate space accommodates at least one coupling element which transfers torque and can be moved from the intermediate space into an alternative space contrary to the action of an elastic restoring force when an overload occurs. The overload coupling has an overload element which is spring-loaded in the direction of rotation of the coupling element and releases the alternative space for the coupling element when an overload occurs.

Description:
This application is a continuation of International application number PCT/EP2003/013532 filed on Dec. 2, 2003. 

   The present disclosure relates to the subject matter disclosed in International application number PCT/EP2003/013532 of Dec. 2, 2003 and German application number 103 18 820.7 of Apr. 16, 2003, which are incorporated herein by reference in their entirety and for all purposes. 
   BACKGROUND OF THE INVENTION 
   The invention relates to a cleaning head for a floor cleaning device with a rotatable brush roller which is coupled to a drive motor via an overload coupling, wherein the overload coupling transfers only a limited torque. 
   Cleaning heads of this type are used for floor cleaning devices, with the aid of which a floor surface to be cleaned can be cleaned, for example, can be brushed and vacuumed. The cleaning head comprises a rotatable brush roller which can be driven by a drive motor. An overload coupling is connected between the brush roller and the drive motor and this transfers only a limited torque. As a result, it is ensured that the transfer of torque is interrupted by the overload coupling when a predetermined limiting value is exceeded. Such an interruption occurs, in particular, when the rotation of the brush roller is blocked. On account of the overload coupling, the drive motor can continue to run uninterrupted and without it becoming overloaded even in the case of such a blocking of the brush roller. 
   Overload couplings are also designated as torque limiters or overload protection devices and are known as such from EP 0 108 930 B1. Torque can be transferred between two machine elements with their help, wherein this transfer is, however, interrupted when an overload occurs, i.e., when a maximum limiting value of the torque is exceeded. As a result, it may, for example, be ensured that the drive element is not damaged during any blocking of the driven element. 
   An overload coupling is known from DE 29 34 164 A1, with which several coupling elements in the form of steel balls are held in their coupling position, in which they transfer torque from the drive element to the driven element, by means of a thrust sleeve spring-loaded in axial direction. When an overload occurs, the thrust sleeve is acted upon by the steel balls with a thrusting force effective in axial direction so that it is deflected in an axial direction and, as a result, facilitates a radial movement of deflection of the steel balls, wherein the transfer of the torque is then interrupted. The overload coupling known from DE 29 34 164 A1 is of a complicated construction. 
   An overload coupling is known from U.S. patent specifications No. 3,552,147 and No. 2,730,220 which has a drive element and a driven element which are arranged concentrically to one another, thereby forming an intermediate space. The intermediate space accommodates a coupling element which transfers torque, wherein the coupling element can be moved from the intermediate space into an alternative space contrary to the action of an elastic restoring force when an overload occurs. The overload coupling also has an overload element which is spring-loaded in the direction of rotation of the coupling element and releases the alternative space for the coupling element when an overload occurs. 
   The object of the present invention is to further develop a cleaning head for a floor cleaning device of the type specified at the outset in such a manner that the overload coupling has a constructionally simple design, can be produced inexpensively and can be operated reliably. 
   SUMMARY OF THE INVENTION 
   This object is accomplished in accordance with the invention, in a cleaning head of the generic type, in that the overload coupling has a drive element and a driven element which are arranged concentrically to one another, thereby forming an intermediate space, wherein the intermediate space has at least one coupling element which transfers torque and can be moved from the intermediate space into an alternative space contrary to the action of an elastic restoring force when an overload occurs, and that the overload coupling has an overload element which is spring-loaded in the direction of rotation of the coupling element, releases the alternative space for the coupling element when the overload occurs and is arranged between the coupling element and the alternative space in a coupling position of the coupling element. The use of an overload element which is spring-loaded in the direction of rotation of the coupling element makes a construction of the overload coupling possible which is particularly simple from a constructional point of view and can, therefore, be produced inexpensively. Torque is transferred to the driven element by the drive element via the coupling element below a critical limiting value of the torque to be transferred. The transfer is brought about, in this case, under the influence of the spring force which is effective in the direction of rotation of the coupling element and with which the overload element is acted upon. The drive element, like the driven element and the at least one coupling element, executes a rotational movement about a common axis of rotation. If the torque exceeds a limiting value predetermined by the effective spring force, the overload element executes a movement relative to the drive element and/or the driven element, wherein it releases an alternative space for the coupling element which the coupling element can enter. 
   As a result of this, the coupling element transfers from its coupling position into a non-coupling position and the transfer of torque between the drive element and the driven element is interrupted. A limitation of the torque to be transferred is ensured by the overload coupling in a constructionally simple manner, wherein the critical limiting value of the torque can be predetermined by the spring force, with which the overload element is acted upon in the direction of rotation. In accordance with the invention, the overload element is arranged between the coupling element and the alternative space in a coupling position of the coupling element. This has the advantage that the access of the coupling element to the alternative space is blocked by the overload element and is released when an overload occurs. The overload coupling is therefore characterized by a reliable mode of operation. 
   In a preferred embodiment, the alternative space adjoins the intermediate space radially on its outer side. Since the coupling element, like the drive element and the driven element, executes a rotational movement during the transfer of torque, the arrangement of the alternative space on the radially outer side has the advantage that the transfer of the coupling element into the alternative space can be achieved by means of the centrifugal force acting on the coupling element. The arrangement of the alternative space on the radially outer side also has the advantage that the at least one coupling element is held automatically in the alternative space when an overload occurs on account of the centrifugal force acting on the coupling element without additional retaining elements needing to be used for this purpose. 
   It has proven to be particularly favorable when the overload element abuts on the coupling element in the coupling position thereof. In this respect, it may be provided for the overload element to cover the alternative space in the coupling position of the coupling element so that the coupling element cannot easily enter the alternative space. If the torque to be transferred exceeds the critical limiting value, the overload element releases the alternative space for the coupling element and the coupling element transfers into its non-coupling position. 
   The drive element and the driven element form an intermediate space between them. This is preferably designed as an annular space arranged between the drive element and the driven element. 
   A configuration which is particularly unsusceptible to malfunction may be preferably achieved in that the annular space accommodates several coupling elements, each of which has an overload element as well as an alternative space associated with it. Several coupling elements, which are arranged in the annular space and each of which has an overload element associated with it which releases an alternative space for the respective coupling element when an overload occurs, are used in this case for the transfer of the torque from the drive element to the driven element. 
   The overload elements associated with the various coupling elements are preferably connected rigidly, in particular, in one piece to one another. 
   In order to act on the overload element with a spring force, it is provided in one preferred embodiment for the overload element to be coupled to the drive element or the driven element via a torsion spring. The torsion spring may, in this case, be designed as a helical spring. 
   It has proven to be favorable when the torsion spring can be releasably connected to the drive element or driven element. This makes it possible, depending on the desired limiting value for the torque to be transferred, to use a torsion spring adapted to this limiting value. 
   In a particularly preferred embodiment, it is provided for the overload coupling to have an intermediate part, on which the at least one overload element is held so as to be non-rotatable and which is coupled to the drive element or driven element via the torsion spring. The intermediate part forms, in this case, a support for the at least one overload element. It is particularly advantageous when the at least one overload element is connected in one piece to the intermediate part. 
   The intermediate part preferably forms an intermediate flange and the at least one overload element is preferably secured to the intermediate flange in the form of an axially protruding projection. This facilitates a configuration of the overload coupling in a constructionally simple manner such that the drive element and the driven element are arranged in a radial direction so as to be offset relative to one another and to form an annular space between them, into which the at least one overload element dips in that this is secured to the intermediate flange of the intermediate part in the form of an axially protruding projection. The intermediate part may, in this case, be positioned in axial direction to as to be offset in relation to the drive element and/or the driven element. 
   The driven element is preferably of a star-shaped configuration and has a plurality of stop surfaces which are aligned at an angle to the direction of rotation of the coupling element and on each of which a coupling element abuts in the coupling position. In this respect, it has proven to be particularly favorable to design the driven element with a shell surface which is configured essentially in the shape of saw teeth and on which several coupling elements abut in their coupling position, wherein the coupling elements can be positioned at a distance in relation to the driven element when an overload occurs by transferring into their alternative position so that the coupling elements can be freely rotated relative to the driven element and, as a result, a transfer of torque is prevented. 
   In order to hold the driven element it may be provided for the overload coupling to have a driven flange, to which the driven element is secured, wherein the driven element forms a collar projecting axially from the driven flange. The collar preferably has a shell surface in the shape of saw teeth. In this respect, it is favorable when the driven flange is aligned parallel to the intermediate flange so that the intermediate space accommodating at least one coupling element is limited in axial direction, on the one hand, by the intermediate flange and, on the other hand, by the driven flange. 
   The radial limitation of the intermediate space may be brought about by means of the driven element and the drive element. 
   A gear wheel is preferably used as drive element and this surrounds the driven element in circumferential direction and, in an advantageous embodiment, forms the at least one alternative space for the coupling element on its radially inner side. 
   A particularly compact configuration is achieved in a preferred embodiment in that the overload coupling has a dome-shaped housing, to which the drive element is secured, wherein the driven flange forms a cover for the housing. The drive element is preferably connected in one piece to the dome-shaped housing. The housing can, in this respect, accommodate the at least one coupling element as well as the overload element and the spring element acting on it with a spring force, preferably in the form of a torsion spring, and is covered by the driven flange which, in a particularly preferred embodiment, supports a driven gear wheel on its outer side facing away from the housing, wherein it is particularly favorable when the driven gear wheel is connected in one piece to the driven flange. 
   The floor cleaning device, for which the cleaning head according to the invention is provided, may be designed as a brush vacuum cleaner, with the aid of which a floor surface to be cleaned can be brushed and vacuumed at the same time. In this respect, it is of particular advantage when the drive motor drives not only a suction fan of the floor cleaning device but also its brush roller. The brush roller is driven so as to execute a rotational movement about a brush axis of rotation. If the brush roller is blocked or obstructed, the use of the overload coupling enables the drive motor to continue to be driven uninterrupted and without any motor overload occurring. The operation of the suction fan is, consequently, not influenced by any obstruction or blocking of the brush roller. 
   The following description of a preferred embodiment of the invention serves to explain the invention in greater detail in conjunction with the drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1 : shows a schematic, partially opened bottom view of a cleaning head according to the invention for a floor cleaning device with an overload coupling; 
       FIG. 2 : shows a sectional view of the overload coupling along line  2 — 2  in  FIG. 1  with active transfer of torque; 
       FIG. 3 : shows a diagrammatic illustration of an intermediate part of the overload coupling; 
       FIG. 4 : shows a sectional view in accordance with  FIG. 2  during the transfer of coupling elements of the overload coupling into an alternative space and 
       FIG. 5 : shows a sectional view of the overload coupling in accordance with  FIG. 2  after successful transfer of the coupling elements into the respective alternative space. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   In  FIG. 1 , a cleaning head designated altogether with the reference numeral  10  is illustrated in a schematic manner; the cleaning head can be moved along a floor surface for the purpose of cleaning the floor surface, wherein the floor surface is brushed and vacuumed at the same time. For this purpose, the cleaning head comprises a brush roller  14  which is mounted so as to be rotatable about a brush axis  12  and can be caused to rotate by means of an electric motor  16 . In addition, the cleaning head has, in a customary manner and not, therefore, illustrated in the drawings, a suction nozzle which is in flow communication with a suction unit which is known to the person skilled in the art and, therefore, likewise not illustrated so that the floor surface to be cleaned can be vacuumed by means of the cleaning head  10 . The suction unit can have in the usual manner a suction fan which is, like the brush roller  12 , caused to rotate by the electric motor  16 . 
   The coupling of the brush roller  14  to the electric motor  16  is brought about with the interposition of an overload coupling  20  which is connected to the electric motor  16  on the drive side via a first toothed belt  22  and to the brush roller  12  on the driven side via a second toothed belt  24 . The electric motor  16  can be integrated into the suction unit and is operatively connected to the brush roller for its rotary drive via the overload coupling  20 . The suction fan may have a rotational speed of, for example, 25000 revolutions per minute (revs/min) while the brush roller  12  has only a rotational speed of, for example, 2800 revs/min. The overload coupling  20  described in detail in the following ensures that a possible blocking of the brush roller  12  does not lead to any interruption in the rotary drive of the suction fan by means of the electric motor  16 . The overload coupling  20  serves, on the contrary, as an overload protection which interrupts the coupling of the brush roller  12  to the electric motor  16  during any blocking thereof. 
   The first toothed belt  22  is in engagement with a drive element of the overload coupling  20  in the form of a drive gear wheel  26  which is connected in one piece to a dome-shaped housing  28  of the overload coupling  20  and forms the outer edge of the housing  28 . Aligned coaxially to the drive gear wheel  26 , the overload coupling  20  has a sleeve  30  which is connected in one piece to the housing  28  and is supported on a bearing axle  32  passing through the housing  28  so as to be freely rotatable. The bearing axle is supported on an underframe  38  of the cleaning head  10  by means of bearings  34 ,  36  arranged at the ends so as to be rotatable. 
   The dome-shaped housing  28  of the overload coupling  20  is covered at its end face by a driven flange  40  which is connected in one piece to a driven gear wheel  42  which is supported on the bearing axle  32  so as to be non-rotatable. The driven gear wheel  42  is in engagement with the second toothed belt  24 . 
   On its inner side facing the interior of the housing  28 , the driven flange  40  bears an axially projecting driven element which is connected in one piece to the driven flange  40  and is designed as a star-shaped collar  44 . The collar  44  has in circumferential direction a shell surface  46  which is essentially of a saw tooth-shaped design and faces an inner edge  48  of the drive gear wheel  26 . The shell surface  46  and the inner edge  48  define between them an annular space  50  which accommodates a plurality of coupling elements in the form of steel balls  52  distributed uniformly in circumferential direction, in the illustrated embodiment eight coupling elements. Each steel ball  52  has a recess  54  associated with it which is integrally formed in the inner edge  48  and defines an alternative space  56  which adjoins the annular space  50  in radial direction adjacent each time to a steel ball  52 . 
   The housing  28  of the overload coupling  20  encloses an intermediate part  58 , the construction of which results, in particular, from  FIG. 3 . It comprises an intermediate flange  60  which is arranged parallel to the driven flange  40 , is connected in one piece to a projecting sleeve  62  on its side facing away from the driven flange  40  and bears on its outer edge overload elements which are arranged equidistant to one another in circumferential direction in the form of projections  64  which protrude axially in the direction of the driven flange  40 , are connected in one piece to the intermediate flange  60  and dip into the annular space  50 , each associated with a steel ball  52 . The projections  64  are, in cross section, approximately of an L-shaped design and comprise a first arm  66  which extends in the shape of a circular arc and concentrically to the inner edge  48  of the drive gear wheel  42  as well as a second arm  68  which is radially aligned and dips into a respective alternative space  56 . 
   The housing  28  also encloses a torsion spring  70  which is of a helical shape and is secured, on the one hand, to the housing  28  and, on the other hand, to the projecting sleeve  62  of the intermediate part  58 . 
   During operation of the cleaning head  10 , torque is transferred to the drive gear wheel  26  from the drive motor  16  via the first toothed belt  22 . The direction of rotation of the drive gear wheel  26  is represented in  FIGS. 2 ,  4  and  5  by the arrow  72 . This is connected in one piece to the housing  28 , to which the torsion spring  70  is secured. The torque is transferred to the intermediate part  58  via the torsion spring  70 . The torque is transferred by the projections  64  of the intermediate part  58  dipping into the annular space  50  to the steel balls  52  which abut on the second arm  68  of the projections  64  and, in their coupling position as illustrated in  FIG. 2 , cause the star-shaped collar  44  to rotate so that the torque is transferred via the driven flange  40  to the driven gear wheel  42  which is coupled to the brush roller  14  via the second toothed belt  24 . A stop surface  65  is formed by the portion of the shell surface  46  that contacts the steel ball  52 . 
   As is apparent from  FIG. 2 , the L-shaped projections  64  cover the alternative spaces  56  provided that the steel balls  52  are in their coupling position. The torsion spring  70  is tensioned with increasing torque load and so the projections  64  execute a relative movement with respect to the drive gear wheel  26 . This results in the projections  64  gradually releasing the alternative spaces  56 , as illustrated in  FIG. 4 . If the torque to be transferred exceeds a limiting value predetermined by the spring force of the torsion spring  70 , the projections  64  spring-loaded by the torsion spring  70  release the alternative spaces  56  to such an extent that the steel balls  52  moving in the direction of rotation  72  pass into the respectively associated alternative spaces  56  on account of the gravity acting on them, wherein they no longer abut on the collar  44  in this position but rather release this completely. During sustained rotation of the drive gear wheel  26 , the steel balls  52  are held in the respective alternative spaces  56  on account of the gravity acting on them, wherein torque is no longer transferred from the steel balls  52  to the collar  44 . When a predetermined limiting value is exceeded, the transfer of torque is, therefore, interrupted by the overload coupling  20 . Such an interruption occurs, in particular, when the rotation of the brush roller  14  is blocked. On account of the use of the overload coupling  20  for the cleaning head  10 , as provided in accordance with the invention, the electric motor  16  of the cleaning head  10  can continue to run uninterrupted and without it being overloaded even with such blocking of the brush roller  14 . 
     FIG. 5  illustrates the overload coupling after successful transfer of the coupling elements into the respective alternative space.