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BACKGROUND OF THE INVENTION 
     The invention concerns a furniture damper for damping a movement of a movably mounted furniture part or a movably mounted furniture fitting component of a furniture fitting, comprising a piston arranged in a fluid chamber, in which a damping action is performed by a relative movement between the fluid chamber and the piston. A sealing device is provided for sealing the fluid chamber, and the sealing device has a first abutment element and a second abutment element mounted movably relative to the first abutment element and adapted to seal the fluid chamber. A spring is arranged between the first abutment element and the second abutment element. 
     A furniture fitting having a furniture damper for damping a movably mounted furniture part, wherein a damping action is performed by a movement of a piston in a fluid chamber, is disclosed in WO 2009/003458. A movably mounted seal is acted upon by a spring which bears against the end plate of the fluid chamber. The spring serves in that case for guiding the movably mounted seal and is held by projections both against the seal and also against the end plate. In the intermediate region, the spring has a constant cross-section and occupies the entire interior of the housing in which the fluid chamber is arranged, to permit guidance for the seal, that is as stable as possible. The disadvantage of such a furniture fitting is that the nature of the spring and the projections take up a great deal of space and the range of movement of the seal is limited, whereby use is conceivable only for large furniture fittings where there is sufficient space. The advantages of a movably mounted seal, as are described in GB 565 630, cannot be enjoyed in that respect for every kind of furniture fittings. 
     SUMMARY OF THE INVENTION 
     Therefore, the object of the present invention is to provide a furniture damper of the general kind referred to in the opening part of this specification, which avoids the above-indicated disadvantages. 
     A furniture damper of the kind referred to in the opening part of this specification has the advantages that the abutment elements, which are mounted movably relative to each other, of the sealing device provide additional space for the damping stroke movement per se and as volume compensation in the course of a damping process when a relative movement takes place between the fluid chamber and the piston. In that case, a fluid is pressed for example as a damping liquid, for example silicone oil, through openings provided for the fluid, from a first region of the fluid chamber into a second region of the fluid chamber. The damping action occurs due to the resistance opposed to the fluid movement by the through openings, as in the case of a conventional fluid damper. The first and second abutment elements are acted upon by the spring disposed between the abutment elements so that, as a consequence of a relative movement of the abutment elements, compression or extension of the spring occurs and the abutment elements which are mounted movably relative to each other are returned to their starting position again. 
     In addition, the beginning and the end of the damping process can be initiated with less of a jerk and more gently, due to the spring-loaded sealing device. The characteristic curve of damping of the damper in itself, which is afforded by the damping force generated during a damping action, becomes smoother due to the movably mounted seal. 
     According to the invention, the spring can be compressed between the first and second abutment elements substantially to the cross-sectional thickness of the spring or the spring coils, whereby there is more damping travel with the same structural size. Alternatively, overall the structural size of the furniture damper is reduced in total in comparison with furniture dampers in the state of the art as, with a given additional compensating volume, due to the movably mounted sealing device, which volume is afforded by the extension and compression of the spring from its neutral position, the first and second abutment elements are compressible to a smaller mutual spacing by virtue of the nature according to the invention of the spring. As a result, the structural height of the sealing device turns out to be less than in the state of the art. The cross-sectional thickness of the spring or the spring coils is used to mean the cross-sectional diameter of the spring wire or the spring strip from which the spring or the spring coil is made. 
     In addition, it is possible for the volume of the compensating space which is additionally made available to be maximised by the spring according to the invention, without having to forego the advantages of a spring loading. 
     Further advantageous configurations of the invention are defined in the appendant claims. 
     In a particularly preferred embodiment of the invention, the spring is a conical spiral spring. A conical spiral spring is distinguished in that the projection of the spring coils on to a plane perpendicularly to the longitudinal axis of the spring represents a spiral. Compression of the conical spiral spring permits the spring coils to be arranged one within the other so that the compressed spring forms a spiral, whereby the lengthwise extent of the compressed spring substantially corresponds to the cross-sectional thickness of the spring or the spring coils. The individual coils of the conical spring have a spiral configuration and therefore increase in diameter. The coils of smaller diameter are pushed into the coils of larger diameter, when the spring is compressed. Upon compression of the spring to its cross-sectional thickness, all coils are pushed into the coil of largest diameter, which is arranged at the base of the conical spring. The cross-sectional thickness of the spring is given here by the cross-sectional diameter of the spring wire or spring strip of the largest coil diameter. 
     It is preferable that the spring has a central opening in which the piston or a piston rod connected to the piston is arranged so that in the mounted condition of the furniture damper, the spring coils are arranged around the piston or piston rod. In that way, the spring is guided during the movement of the first abutment element relative to the second abutment element, by the piston or the piston rod. 
     In a further embodiment of the invention, the first abutment element has a contact surface against which (in the mounted condition of the spring) a first end of the spring bears and the spring is thereby supported against the first abutment element. In that way, it is possible to dispense with projections in the abutment element for fixing the spring, which require a large amount of space. Additionally or alternatively, the second abutment element can have an abutment surface against which a second end of the spring bears in the mounted condition of the spring, whereby the spring is supported against the second abutment element. In that way, it is possible to dispense with projections on the second abutment element, that require a large amount of space and serve to mount the spring. The abutment elements are acted upon by the spring by way of the abutment surface or surfaces. A relative movement of the abutment elements with respect to each other is transmitted to the spring by way of the abutment surface or surfaces of the abutment elements. 
     During the damping process, the relative movement between the fluid chamber and the piston is transmitted to the abutment elements so that they are also moved relative to each other, whereby the spring is compressed between the abutment elements. In that respect, the spring has such a design that, as a consequence of a maximum damping stroke, the second and the first abutment elements assume a minimum spacing relative to each other, and the spring disposed between the abutment elements is compressed substantially to the cross-sectional thickness of the spring or spring coils. As a subsequent consequence, the spring stretches to its neutral position again and transmits that movement to the abutment elements so that they again assume a greater spacing from each other and are returned to their starting position. 
     In a further embodiment of the invention, the second abutment element has a sealing element which has sealing lips which (in the mounted condition) bear against the piston or a piston rod connected to the piston and additionally or alternatively against the wall of a housing surrounding the fluid chamber and thereby seal off the fluid chamber. In that case, the sealing integrity prevents the fluid in the fluid chamber from escaping therefrom. It is preferably provided in that respect that the fluid chamber is enclosed by a housing having an open end. The sealing integrity afforded by the sealing device, in particular by the sealing element with the sealing lips, closes off the fluid chamber in relation to the open end. 
     The invention further concerns a furniture hinge having a furniture damper as described above. 
     It is preferable in that respect that the furniture hinge has a carcass-side fitment portion and a hinge cup hingedly connected thereto for fixing furniture parts, and in the mounted position, the furniture damper is arranged substantially completely within the hinge cup. Instead, the furniture damper can be fitted from above into the hinge cup and can be arranged within the hinge cup. In that case, the fitment portion and the hinge cup can already be hingedly connected together. The furniture damper can be connected to the hinge cup by co-operating fixing means in that mounted position. 
     The space within a hinge cup is generally very small as hinge cups are arranged in side walls of furniture carcasses or in doors which close furniture carcasses. The advantage of furniture dampers arranged in hinge cups is that no space is occupied within the furniture carcass by the arrangement of the damper. However, very high demands are made on furniture dampers which are arranged in hinge cups, in regard to the small size of the components to be used. For that reason, a furniture damper according to the invention which has a spring between a first and a second abutment element, which spring can be compressed substantially to the cross-sectional thickness of the spring, is of particular advantage. 
     The invention further concerns a furniture damper for damping a movement of a movably mounted furniture part or a movably mounted furniture fitting component of a furniture fitting, comprising a piston arranged in a fluid chamber, wherein a damping action is performed by a relative movement between the fluid chamber and the piston. A sealing device is provided for sealing the fluid chamber, and the sealing device has a first abutment element and a second abutment element which is mounted movably relative to the first abutment element and which is adapted to seal the fluid chamber. The piston assumes a first end position at the end of the damping stroke relative to the fluid chamber. A return spring is provided by which the relative position of the piston relative to the fluid chamber is displaceable into a readiness position remote from the end position, and the return spring is arranged between the first and second abutment elements. 
     The furniture damper in that case has the above-described configuration. The spring which serves for the return movement of the relative position of the first and second abutment elements and which is arranged between the first and second abutment elements additionally serves to return the relative position of the piston relative to the fluid chamber. In that case, the spring disposed between the first and second abutment elements can support or completely replace a further return spring or springs serving to return the relative position of the piston relative to the fluid chamber. 
     In the last-mentioned case, the spring arranged between the first and second abutment elements must have a spring constant such that not only can the abutment elements be returned, but the relative position of the piston relative to the fluid chamber can also be returned to the readiness position after the conclusion of a damping process so that the furniture damper is ready for use for a fresh damping process. In that respect, the spring can be compressed substantially to the cross-sectional thickness of the spring by the relative movement of the first and second abutment elements. 
     The invention further concerns a furniture hinge having a furniture damper with a return spring as described above. In a particular embodiment, the furniture hinge has a carcass-side fitment portion and a hinge cup hingedly connected thereto for fixing furniture parts. In that case, in the mounted position the furniture damper is arranged substantially completely within the hinge cup or can be inserted from above into the hinge cup when the fitment portion and the hinge cup are already hingedly connected together, and it can be arranged within the hinge cup. The furniture damper can be connected to the hinge cup by way of co-operating fixing means in that mounted position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further details and advantages of the present invention are described more fully hereinafter by means of the specific description with reference to the drawings, in which: 
         FIG. 1  shows a perspective view of an article of furniture with a door mounted pivotably relative to a furniture carcass by way of furniture hinges, 
         FIGS. 2   a  and  2   b  show perspective views of a furniture hinge with a furniture damper to be arranged in the hinge cup, 
         FIGS. 3   a  through  3   c  show the furniture damper as an exploded view, an enlarged detail view of the slider and the arresting element as a perspective view from below, 
         FIGS. 4   a  and  4   b  show perspective views in longitudinal section through the furniture damper in various positions of the piston relative to the fluid chamber, 
         FIGS. 5   a  and  5   b  show the views of  FIGS. 4   a  and  4   b  at another moment in time during the damping process, 
         FIGS. 6   a  and  6   b  show a partly broken-away perspective view through a furniture hinge with a furniture damper integrated in the hinge cup, and a detail view thereof, 
         FIG. 7  shows a perspective view in longitudinal section of a furniture damper integrated in the hinge cup, and an enlarged detail view thereof, 
         FIGS. 8   a  and  8   b  show a plan view of a longitudinal section through the furniture damper and an enlarged detail view thereof, 
         FIGS. 9   a  and  9   b  show the views of  FIGS. 8   a  and  8   b  at another moment during the damping process, 
         FIGS. 10   a  and  10   b  show the views of  FIGS. 8   a  and  8   b  at yet another moment during the damping process, and 
         FIGS. 11   a  through  11   e  show various views of a conical spiral spring according to the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a perspective view of an article of furniture  1 , wherein a movable furniture part  3  in the form of a door  3   a  is mounted pivotably relative to a furniture carcass  2  by way of two or more furniture hinges  4 . In a known manner, the furniture hinges  4  have a fitment portion  5  to be fixed to a frame  2   a  and a hinge cup  6  connected pivotably to the fitment portion  5 . Mounted in the internal cavity in the hinge cup  6  is a respective furniture damper (not visible here), by which a closing movement of the furniture hinge  4  to the completely closed end position can be damped. Depending on the respective size and weight of the movable furniture part  3 , the damping power of the furniture damper cannot be appropriately adapted. That is to say, in the case of a damping power which is excessively great, the movable furniture part  3  can pass into the completely closed position, either too slowly or not at all. For that reason, the damping action of the furniture damper can be completely deactivated by way of a locking device. In that respect, it may be desirable for example for the damping action of a first furniture hinge  4  to be completely deactivated while a second furniture hinge  4  provides an active damping action which permits a desired damped closing movement of the movable furniture part  3  to the completely closed position. 
       FIG. 2   a  shows a perspective view of a furniture hinge  4 , wherein the hinge cup  6  is connected pivotably by way of at least one hinge lever  7  to the fitment portion  5  in the form of a hinge arm  5   a . The furniture hinge  4  can be moved into the completely closed position and/or into the completely open position by way of a spring device  8 . For damping that spring-assisted movement into the end position or positions, there is provided a furniture damper  9  having a housing  12  and a slider  13  movable relative thereto. The furniture damper  9  is either already fitted in the factory into the internal cavity  10  in the hinge cup  6  or alternatively—with the fitment portion  5  and the hinge cup  6  assembled—the furniture damper  9  can be retro-fitted from above into the hinge cup  6  and arranged within the hinge cup  6 . In that case, the furniture damper  9  can be releasably connected together in that mounted position by way of a co-operating fixing device  11   a ,  11   b . In the illustrated embodiment, the furniture damper  9  has first fixing part  11   a  in the form of a guide groove, which can be releasably connected to second fixing part  11   b  arranged in the hinge cup  6  and in the form of a fixing projection. The furniture damper  9  has an introduction opening  14  through which the fixing projection  11   b  can be arranged in the guide groove  11   a . To deactivate the damping function, the furniture damper  9  has a locking device  15  with a displaceable arresting element  15   a  in the form of a switch member, by which the slider  13  can be releasably arrested in the position of being completely pressed in. 
       FIG. 2   b  shows a perspective view of the furniture hinge  4  with the furniture damper  9  in the mounted position. The furniture damper  9  is arranged completely in the internal cavity  10  in the hinge cup  6 . In the closing movement of the furniture hinge  4 , the hinge lever  7  encounters the slider  13 , whereby the damping process is initiated. In the course of the further closing movement, the slider  13  can be pressed relative to the housing  12  into a complete end position, wherein that end position can be releasably arrested by the locking device  15 . The slider  13  can no longer be returned in the arrested position, in which case therefore the damping action is deactivated. 
     In the exploded view in  FIG. 3   a , the furniture damper  9  has a housing  12  and a slider  13  displaceable relative thereto. The furniture damper  9  is in the form of a linear damper and includes a piston rod  17  connected to the housing  12 . This embodiment therefore provides that the piston rod  17  (and therewith a piston connected to the piston rod  17 ) is arranged stationarily in the mounted position while a fluid chamber provided in the slider  13  is movable relative to that stationary piston rod  17 . The slider  13  is in the form of a sliding wedge member and has an inclined abutment surface  16  which, as from a predetermined relative position of the furniture hinge  4 , can be acted upon by the hinge lever  7  ( FIG. 2   b ). 
     Provided in the interior of the slider  13  is at least one fluid chamber in which at least one piston (not visible here) with a piston rod  17  is displaceably mounted. It is possible clearly to see the first fixing part  11   a  in the form of guide grooves on both sides, by which the slider  13  is displaceable in the damping stroke movement relative to the second fixing part (projections)  11   b  of the hinge cup  6 . The second fixing part (projection)  11   b  can be arranged in the first fixing part (guide groove)  11   a  through the introduction opening  14 . The housing  12  has a mounting  18  to which the piston rod  17  is to be fixed. Arranged on the slider  13  is a first securing element  19  which can be secured in the pressed-in end position of the slider  13  relative to a second securing element  20  arranged on the switch  15   a.    
       FIG. 3   b  shows an enlarged detail view of the slider  13 , on which a first securing element  19  in the form of a resilient tongue is provided.  FIG. 3   c  shows a perspective view from below of the arresting element  15   a  in the form of a switch. Arranged at the underside of the arresting element  15   a  is the second substantially rigid securing element  20 , by which the first securing element  19  of the slider  13  can be secured in the completely pressed-in end position of the slider  13 . 
       FIG. 4   a  shows a perspective view in longitudinal cross-section through a furniture damper  9 . It is possible to see the slider  13  in which there is a fluid chamber  21 , in which a piston  22  with a piston rod  17  is mounted, being arranged stationarily in the illustrated embodiment. In the closing movement of the furniture hinge  4 , the hinge lever  7  ( FIG. 2   b ) encounters the inclined abutment surface  16  of the slider  13 , whereupon the slider  13  is displaceable relative to the stationary piston  22 . 
     The housing of the slider  13  has an open end which is closed by a first abutment element  27  in the form of a cover plate. The first abutment element  27  has an opening for the piston rod  17 . The spring  26  in the form of a conical spiral spring is arranged around the piston rod  17 . A first (large diameter) end of the spring  26  bears against the abutment surface of the first abutment element  27  and in that case is supported on the first abutment element  27 . The narrower second (small diameter) end of the spring  26  bears against an abutment surface of a second abutment element  28  and is supported thereat. The second abutment element  28  has a sealing element  29  having an outer sealing lip  31  and an inner sealing lip  32 . The outer sealing lip  31  serves to seal off the fluid chamber  21  in the region of the housing wall of the slider  13  and bears thereagainst. The inner sealing lip  32  serves to seal off the fluid chamber  21  in the region of the piston rod  17  and for that purpose bears thereagainst. 
       FIG. 4   b  shows a plan view of the longitudinal section in  FIG. 4   a , in which respect it is to be noted that the sealing lips  31  and  32  are shown diagrammatically. Without a piston rod  17  and without a wall of the slider  13 , the sealing element  29  would assume the illustrated shape with the outer and inner sealing lips  31 ,  32 . That is to say, the sealing element  29  it is of slightly larger outside dimensions than the space actually present within the fluid chamber  21 . In the mounted position, by virtue of the elastic or deformable sealing element  29 , the outer sealing lip  31  is pressed inwardly by the housing wall, while the inner sealing lip  32  is pressed outwardly by the piston rod  17 . That permits mobility of the second abutment element  28  together with the sealing element  29  with simultaneous sealing of the fluid chamber  21  and the slider  13 , respectively. In that case, the sealing element  29  can be fixed for example with adhesive on the second abutment element  28 , or can be screwed thereto. 
       FIGS. 4   a  and  4   b  show the furniture damper  9  prior to initiation of a damping process by the hinge lever  7 . The furniture damper  9  is in the readiness position. In that case, the fluid arranged in the region at the left of the piston  22  in the fluid chamber  21  is urged into the region to the right of the piston  22  by way of through openings, whereby a damping effect occurs. The sealing element  29  with the outer and inner sealing lips  31 ,  32  prevents the fluid from passing through into the additional compensating space  33  between the first and second abutment elements  27 ,  28 . That additional compensating space  33  serves as an additional damping stroke and by way of the spring  26 , permits a more gently matched damping action. The return spring  30  (which is not shown in  FIG. 4   a  for reasons of clarity of the drawing) acts on the first abutment element  27  and serves to return the slider  13  again after damping has occurred. 
       FIGS. 5   a  and  5   b  again show the furniture damper  9  as a perspective view ( FIG. 5   a ) and a plan view ( FIG. 5   b ) of a longitudinal section. The illustrated components correspond to those in  FIGS. 4   a  and  4   b . In the situation shown in  FIGS. 5   a  and  5   b , the slider  13  is almost in its end position with respect to the piston  22 . The damping stroke which is possible by the piston  22  has been almost completely used up. Besides the damping stroke that is still available, the fluid in the fluid chamber  21 , which fluid is moving with a certain inertia, is still additionally pressing in the direction of the sealing element  29 . As can be seen, the additional compensating volume  33  of the additional compensating space  33  is also not yet entirely used up as the spring  26  can be compressed to its cross-sectional thickness (i.e., a thickness equal to the diameter of the wire forming the spring, as shown in  FIG. 10   b ). 
       FIG. 6   a  shows a cross-section of a furniture hinge  4  with the furniture damper  9  in the mounted position. The furniture hinge  4  has a fitment portion  5  which is in the form of a hinge arm  5   a —and which is preferably L-shaped—and which is connected pivotably to the hinge cup  6  by way of a hinge lever  7 . The hinge lever  7  is mounted pivotably about an axis of rotation  23  at the furniture cup side.  FIG. 6   b  shows an enlarged detail view of the region circled in  FIG. 6   a . Towards the end of the closing movement, the hinge lever  7  encounters the inclined abutment surface  16  of the slider  13  and displaces it relative to the stationary piston  22 . The damping stroke of the furniture damper  9  extends substantially at a right angle to the axis of rotation  23 . The slider  13  can be arrested by the switch  15   a  in the pressed-in end position relative to the housing  12  of the furniture damper  9 , whereby the damping action can be deactivated. 
       FIG. 7  shows a longitudinal section of the furniture damper  9 . The piston  22  with the piston rod  17  is mounted within the fluid chamber  21 . It is possible to see a return mechanism  30  placed outside the fluid chamber  21  and in the form of two return springs which are supported on the one hand against abutments  24  of the housing  12  and on the other hand against counterpart abutments  25  of the slider  13 . After the damping stroke has taken place, the slider  13  can be returned by the return mechanism  30  into a readiness position again, which is provided for the next damping stroke. It will be appreciated that it is also possible to arrange a return spring in the interior of the fluid chamber  21 , which can be supported on the one hand against the end  34  of the fluid chamber  21  and on the other hand against the piston  22  and thus urges the piston  22  into the readiness position again. 
       FIG. 8   a  corresponds in principle to  FIG. 4   b . The marked portion is shown as an enlarged view in  FIG. 8   b . The illustrated situation is prior to initiation of the damping process. The additional compensating space  33  is still completely unused. The spring is in its neutral (free) position or in the starting position defined by the abutment elements  27 ,  28 , and is not yet compressed by a relative movement of the abutment elements  27 ,  28 . 
       FIGS. 9   a  and  9   b  show the components of  FIGS. 8   a  and  8   b , wherein the damping process is already further advanced. The spring  26  is already compressed and the additional compensating space  33  is partially used up by the second abutment element  28  which is moving towards the first abutment element  27 . 
       FIGS. 10   a  and  10   b  show the components of  FIGS. 8   a  and  8   b , wherein the damping process is now concluded and the first abutment element  27  and the second abutment element  28  are in their end position, that is to say at the smallest spacing relative to each other. The spring  28  is now compressed completely to the cross-sectional thickness of the spring  26  or the spring coil (i.e., compressed to a thickness equal to a diameter of the wire forming the spring). That provides a maximum damping stroke movement, and the internal space in the slider  13  can be small with nonetheless a sufficient damping stroke. That is of great advantage in particular when it is arranged within a hinge cup. 
       FIGS. 11   a  and  11   b  show the spring  26  in the form of a conical spiral spring as perspective views in its neutral position ( FIG. 11   a ) and in the compressed position ( FIG. 11   b ) where it can be seen that the spring  26  can be compressed to the form of a spiral so that the compressed spring  26  is substantially of its cross-sectional thickness. 
     That can also be clearly seen from the side view in  FIG. 11   d . In comparison, the side view of the spring  26  in  FIG. 11   c  shows the spring in its neutral position. 
       FIG. 11   e  again shows a plan view of the spring  26  where it can be seen that the projection of the spring  26  on to a plane perpendicular to the longitudinal axis is in the form of a spiral, independently of the compression condition. It will be seen that the spring coils of the spring are of such a configuration that they can be pushed one into the other. 
     In the illustrated drawings, the return of the slider  13  is implemented by way of return springs  30 . It is, however, also possible to permit that return movement by the spring  26 , in which case the spring  26  can support or entirely replace the return springs  30 . 
     The present invention is not limited to the illustrated embodiment but extends to all variants and technical equivalents which can fall within the scope of the appended claims. The positional references adopted in the description such as for example up, lateral, and so forth are also related to the directly described Figure and are to be appropriately transferred to the new position upon a change in position.

Summary:
A furniture damper damps a movement of a movably mounted part of a piece of furniture or a movably mounted component of a furniture fitting. The damper includes a piston arranged in a fluid chamber, a damping action being carried out by a relative movement between the fluid chamber and the piston. A sealing device seals the fluid chamber, and the sealing device includes a first abutment element and a second abutment element that is movably mounted in relation to the first abutment element and designed to seal the fluid chamber. A spring is arranged between the first abutment element and the second abutment element, and the spring is compressible by the relative movement of the first abutment element and the second abutment element essentially up to the thickness of the cross-section of the spring.