Abstract:
Damper, in particular for washing machines with a spin cycle, with a housing having a central longitudinal axis and at least partially encompassing a housing interior by housing walls, a plunger displaceable in the housing along the central longitudinal axis, guided out of the housing and having at least one friction lining recess, fastening elements, arranged on open ends of the housing and the plunger, and at least one friction lining, arranged in the at least one friction lining recess and in frictional contact with opposite housing walls.

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The invention relates to a damper, in particular a friction damper as used, for example, in washing machines with a spin cycle. 
     Background Art 
     A friction damper with a rectangular housing is known from EP 0 697 539 B1. The plunger has friction linings on opposite sides. Moreover, manufacture of the housing is extremely expensive. 
     SUMMARY OF THE INVENTION 
     The object of the invention is to create a friction damper which can be produced simply and at reasonable cost. 
     The object is achieved by a damper with a housing having a central longitudinal axis, at least partially encompassing a housing interior by housing walls, a plunger displaceable in the housing along the central longitudinal axis, guided out of the housing and having at least one friction lining recess, fastening elements, arranged at free ends of the housing and the plunger, and at least one friction lining, arranged in the at least one friction lining recess and in frictional contact with opposite housing walls. The basis of the invention is to provide a continuous window on the inside end of a plunger guided in a housing, in which window a friction lining is arranged. This one friction lining is in frictional contact with opposite inside walls of the housing. The attenuation characteristics of the damper can be freely set by the configuration of the window—the friction lining recess—and of the friction lining. Moreover, the arrangement has the advantage that only one single friction lining is required for friction on two friction surfaces. 
     Additional features and details of the invention emerge from the description of several embodiments with the aid of the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an external view of a damper according to a first embodiment, 
         FIG. 2  shows a cross-section according to cutting line II-II in  FIG. 1 , 
         FIG. 3  shows the housing of the damper according to  FIG. 1 , 
         FIG. 4  shows the plunger of the damper according to  FIG. 1 , 
         FIG. 5  shows the friction lining of the damper according to  FIG. 1 , 
         FIG. 6  shows a friction lining of a damper according to a second embodiment, 
         FIG. 7  shows a plunger of a damper according to a third embodiment, 
         FIG. 8  shows a plunger of a damper according to a fourth embodiment, 
         FIG. 9  shows a housing of a damper according to a fifth embodiment, 
         FIG. 10  shows a housing part of the housing according to  FIG. 9 , 
         FIG. 11  shows a housing of a damper according to a sixth embodiment, 
         FIG. 12  shows a housing part of the housing according to  FIG. 11 , 
         FIG. 13  shows a plunger of a damper according to a seventh embodiment, and 
         FIG. 14  shows a cross-section in the region of the friction lining recess of a damper according to an eighth embodiment. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A first embodiment of the invention is described below with reference to  FIGS. 1 to 5 . A damper  1  has a housing  2  with a central longitudinal axis  3 , in which a plunger  4  is displaceably guided. The housing  2  is constructed as one part. It is also possible to provide the housing  2  composed of several parts, in particular two parts. The housing  2  has an outer, axial end  5  and an opposite end  6  facing the plunger  4 . In the region of end  5  the housing  2  has a fastening element  7 , in particular in the form of an eye, via which the housing  2  is fastened and coupled in the washing machine. The plunger  4  can be inserted into the housing  2  along an insertion direction  8 , which runs parallel to the central longitudinal axis  3 . At the outer end  9  of the plunger  4  located opposite direction  8 , the plunger  4  has a fastening element  10  in the form of an eye, via which the plunger  4  is coupled and fastened in a washing machine. The plunger  4  can be prevented from being pulled fully out of the housing  2  by pull-out-limiting means, not illustrated. 
     Starting behind the fastening element  10  in direction  8 , the plunger  4  has a double-T-shaped or H-shaped cross-section, which is formed by two side bridges  11 ,  12 , running parallel to one another, and by an intermediate bridge  13 , arranged between them, which connects the side bridges  11 ,  12  to one another. The intermediate bridge  13  runs perpendicular to the side bridges  11 ,  12 . In the region of the end of the plunger  4  located in direction  8 , provided in the intermediate bridge  13  is a friction lining recess  14 , which fully penetrates the intermediate bridge  13 , in other words is open to two sides—top and bottom. The recess  14  is limited on the circumferential side, i.e. in the plane formed by the intermediate bridge  13 , towards all sides by the intermediate bridge  13 . The recess  14  has a rectangular shape with parallel end faces  15  located along direction  8  and parallel longitudinal sides  16  connecting them. Arranged in the recess  14  is a friction lining  17 , the shape of which in the simplest case corresponds substantially to that of the recess  14 . The friction lining  17  is thus cuboid, its end faces  18  resting against the end faces  15  of the recess  14  and its longitudinal sides  19  resting against the longitudinal sides  16  of the recess  14 . Otherwise the friction lining  17  has two friction surfaces  20 , running parallel to one another and forming the top and bottom of the cuboid. The friction lining  17  consists, for example, of a suitable foam material. The friction lining  17 , which is itself preferably constructed as one part, rests directly against the edge of the recess  14  against the plunger  4 , preferably constructed as one part. 
     The housing  2  encompasses a housing interior  21 , the cross-sectional shape of which corresponds to the outer contour of the plunger  4 , i.e. the housing  2  likewise has a double-T-cross-sectional shape. Formed in the housing  2  are two longitudinal channels  22 , extending along the central longitudinal axis  3  and corresponding to the side bridges  11 ,  12 , which are connected to one another by an intermediate channel  23  corresponding to the intermediate bridge  13 . The longitudinal channels  22  are limited by longitudinal channel walls  24 . The intermediate channel  23  is limited by two intermediate channel walls  25 , opposite one another and running parallel to one another. Fastened to the intermediate channel walls  25  are flat friction inserts  26 , consisting of sheet metal. They are fixed in the region of the transition to the fastening element  10  by L-shaped offsets  27 , provided in corresponding longitudinal grooves in the intermediate channel wall  25 . The friction inserts  26  extend over the full length of the housing interior  21  and are located in each case between the intermediate channel walls  25  and the intermediate bridge  13  of the plunger  4 . The housing  2  is advantageously made of plastics material. The friction inserts  26  may consist of steel sheet metal, for example. 
     The mode of functioning of the friction damper is described below. The desired frictional force can be set, for example, by the choice of thickness D R  of the friction lining  17 . In particular, the friction lining  17  may have a thickness D R  which is greater than the width B Z  of the intermediate channel  23 . The friction lining  17  thus rests against the friction surfaces  28  of the friction inserts  26  with bias. In direction  8  and perpendicular thereto in the plane formed by the intermediate bridge  13 , the friction lining  17  is held by the end faces  15  and longitudinal sides  16 . One friction lining  17  rests directly against the friction surfaces  28  located opposite one another. Therefore precisely only one single friction lining  17  is required to have frictional effect on two opposite friction surfaces  28 . The attenuation characteristics of the damper  1  can be largely freely set by the shape of the recess  14  and the circumferential configuration of the friction lining  17 . 
     If the plunger  4  is inserted along direction  8 , the friction lining  17  is initially partially compressed owing to the forces of static friction between friction surfaces  20  and friction surfaces  28 , achieving a minimal free-wheeling effect. There then follows increasing build-up of kinetic friction force. The same applies to the subsequent pulling of the plunger  4  out of the housing  2  against direction  8 . If the length L R  of the friction lining  17  is smaller in the axial direction than the axial length L A  of the recess  14 , there is greater compression of the friction lining  17  when the plunger  3  ( sic ) is inserted or pulled out. A more marked free-wheeling effect thus occurs. If the length L R  of the friction lining  17  is greater than the length L A  of the recess  14 , and the friction lining  17  is therefore axially biased in the recess  14 , a lesser or no free-wheeling effect occurs. The build-up of frictional force is thus more abrupt. An advantage of the build-up is the characteristics which can be influenced, i.e., for example, free-wheeling or gentle build-up of frictional force. Corresponding characteristics have a positive effect on the running properties of the washing machine. For example, the ground forces are reduced and the acoustics improved. 
     A second embodiment of the invention is described below with reference to  FIG. 6 . Identical parts are given the same reference numerals as in the first embodiment, to the description of which reference is herewith made. Structurally different, but functionally similar parts are given the same reference numerals with an a placed after them. The main difference from the first embodiment is in the configuration of the friction lining  17   a . The friction lining  17   a  basically again has a cuboid shape with longitudinal sides  19  and end faces  18   a . However, the axial ends are formed not by a planar end face, but by an indented outer contour with numerous points  29 . The friction lining  17   a  thus has end faces  18   a  which are meandering in cross-section. Again, three cases can be distinguished. If L R  is approximately equal to L A , a greater free-wheeling effect arises, as the points  29  are more easily compressed. There is thus a very gentle, progressive build-up of frictional force. If L R  is smaller than L A , an even more marked free-wheeling effect occurs owing to the slipping of the friction lining  17   a  in the recess  14 . If L R  is greater than L A , the gentle build-up of frictional force is increasingly eliminated by the points  29  therefore already compressed in the initial state. 
     A third embodiment of the invention is described below with reference to  FIG. 7 . Identical parts are given the same reference numerals as in the first embodiment, to the description of which reference is herewith made. Structurally different, but functionally similar parts are given the same reference numerals with a b placed after them. The main difference from the first embodiment is that the longitudinal sides  16   b , which limit the recess  14   b  laterally, are constructed not as smooth, but as indented or meandering. The points  30  of the longitudinal sides  16   b  press into the friction lining  17  from the side, so it is better fixed along direction  8 . 
     Owing to the axial fixing no free-wheeling effect occurs. The build-up of frictional force is not so gentle at the start of insertion or pushing out of the plunger  4 , but more abrupt. The friction lining  17  may additionally have teeth on its longitudinal sides  19 , which match the longitudinal side  16   b.    
     A fourth embodiment of the invention is described below with reference to  FIG. 8 . Identical parts are given the same reference numerals as in the first embodiment, to the description of which reference is herewith made. Structurally different, but functionally similar parts are given the same reference numerals with a c placed after them. The main difference from the first embodiment is that the end faces  15   c  are not planar, but are provided with lugs  31  projecting into the recess  14   c , in particular two lugs. If the friction lining  17  has a length L R  corresponding to the distance between the opposite points of the lugs  31 , a gentle free-wheeling effect occurs owing to the compression of the friction lining  17 . There is a gentle, progressive build-up of frictional force. The lugs  31  first penetrate the friction lining  17 . Only then does the respective end face  18  of the friction lining  17  encounter the end face  15   c  of the recess  14   c . If the friction lining  17  is shorter than the distance between the points of the lugs  31 , a more marked free-wheeling effect occurs, owing to the slipping of the friction lining  17  in the recess  14   c . There is thus a gentle, progressive build-up of frictional force. 
     A fifth embodiment of the invention is described below with reference to 
       FIGS. 9 and 10 . Identical parts are given the same reference numerals as in the first embodiment, to the description of which reference is herewith made. Structurally different, but functionally similar parts are given the same reference numerals with a d placed after them. The main difference from the first embodiment is that the housing  2   d  is not constructed as one part, but consists of two preferably identical housing parts  32 , locked to one another, for example. The connecting mechanism for connecting the two housing parts  32  is a linear bayonet, which is braced in the last part of the locking movement. In principle, locking of the two parts  32  is also possible. The housing part  32  has a base plate  33 , on the axial end  5  of which a fastening element  7  is provided. On the inside of the base plate  33 , one half of the longitudinal channels  22  is formed in the shape of longitudinal grooves. Between them is located the intermediate channel wall  25 , projecting upwards, on which the friction insert  26 , consisting of sheet metal, is arranged. The base plate  33  has two axially extending, outer longitudinal flanks  34 ,  35 . Along flank  35  teeth  36  are provided laterally, i.e. projecting outwards, with lugs  37  projecting downwards in the manner of a toothed strip. The top of the teeth  36  defines a planar first sliding face  38 . 
     In the region of the longitudinal flank  34  is formed a rail  39 , U-shaped in cross-section, extending axially and open towards the base plate  33 , consisting of a lower strip  40 , a central strip  41  running perpendicular thereto and an upper strip  42  arranged parallel to the lower strip  40  and connected to the central strip  41 . The top of the lower strip  40  defines a second sliding face  43 , sliding faces  38  and  43  being located in the same plane. The upper strip  42  is formed by a row of teeth  44  with lugs  45 , corresponding to teeth  36  and lugs  37  and located at the same axial height. Recesses  46  are provided in the lower strip  40  in the region of the teeth  44 , to simplify removal from the mould during the injection-moulding process of the housing part  32 . For assembly, two housing parts  32  are placed on top of one another, offset by one tooth position, and then displaced axially by one tooth position, so the two housing parts  32  are overlapped and locked to one another. Catching lugs, not illustrated, are provided on the lugs  37  for this purpose, which prevent the housing parts  32  slipping apart. An advantage of the configuration of the housing parts  32  is the fact that they can be easily produced. It is also possible to dispense with integrated axial securing, which produces locking, and to produce axial securing of the two housing parts  32  by joining a layer of rubber and a spacing bush in the eye. 
     A sixth embodiment of the invention is described below with reference to  FIGS. 11 and 12 . Identical parts are given the same reference numerals as in the first embodiment, to the description of which reference is herewith made. Structurally different, but functionally similar parts are given the same reference numerals with an e placed after them. The main difference from the fifth embodiment according to  FIGS. 9 and 10  is in the configuration of the catching elements and the locking movement. On the right side of the base plate  33  in  FIG. 12  is provided a continuous strip  47  with catching lugs  48  projecting upwards, the catching lugs  48  decreasing in profile laterally outwards transversely to the central longitudinal axis  3 . As in the fifth embodiment, formed on the opposite side of the base plate  33  is a rail, U-shaped in cross-section, with strips  40   e ,  41   e ,  42   e . Strip  42   e  is formed by catching teeth  44   e , arranged above recesses  46   e . During assembly, two housing parts  32   e  are placed on top of one another at the same axial height and locked together perpendicular to direction  8  along a catching direction  49 . The catching lugs  48  of the upper housing part  32   e  engage in the recesses  46   e  of the lower housing part  32   e . The same applies to the corresponding, opposite row of catching lugs  48 . 
     A seventh embodiment of the invention is described below with reference to  FIG. 13 . Identical parts are given the same reference numerals as in the first embodiment, to the description of which reference is herewith made. 
     Structurally different, but functionally similar parts are given the same reference numerals with an f placed after them. The main difference from the first embodiment is in the configuration of the friction lining recess  14   f . This is diamond-shaped, i.e. two opposite sides are parallel to one another in each case, are not perpendicular to one another and all the sides are the same length. Two opposite points face along the insertion direction  8 . In the diamond-shaped friction lining recess  14   f  is arranged a diamond-shaped friction lining, not illustrated, matching the recess  14   f . The advantage of the diamond-shaped configuration is the reduction of the static friction points at the start of a friction process. The friction lining is constructed tapering to a point along direction  8 , so the static friction forces acting on the points are lower at the start of a movement. The diamond-shaped configuration of the recess and the friction lining results in an improved running property of the damper. Otherwise, the plunger has a trough-shape in the region of the side bridges  11   f  and  12   f  and of the intermediate bridge  13   f , which shape is explained in greater detail with the aid of the next embodiment, reference herewith being made thereto. 
     An eighth embodiment of the invention is described below with reference to  FIG. 14 . Identical parts are given the same reference numerals as in the first embodiment, to the description of which reference is herewith made. Structurally different, but functionally similar parts are given the same reference numerals with a g placed after them. The main difference from the first embodiment is in the configuration of the indentation formed by the side bridges  11   g  and  12   g  and by the intermediate bridge  13   g  on the top and bottom of the plunger  4   g . In the first embodiment, the plunger has on the top and the bottom in each case a U-shaped, i.e. overall an H-shaped, cross-section, i.e. the outer walls of the side bridges are perpendicular to the intermediate bridge. In the present embodiment this is different. There the top and the bottom of the plunger  4   g  have a trough-shaped indentation. This means that the inner faces  50  of the side bridges  11   g  and  12   g  enclose with the bottom face  51 , formed by the outside of the intermediate bridge  13   g , an angle of more than 90°, i.e. the inner faces  50  run obliquely outwards. The housing  2   g  has a corresponding trough-shaped constriction, formed by side bridges  52  and  53 , which run parallel to the inner faces  50 , and an intermediate bridge  54 , which runs parallel to intermediate bridge  13   g . Provided on the inside of bridges  52 ,  53  and  54  is a correspondingly shaped friction insert  26   g , which rests against the inside of bridges  52 ,  53  and  54  and is fastened there. There is only a small amount of play between the legs of the friction insert  26   g  and the inner faces  50 . Otherwise there is a greater amount of play  55  between the side bridges  11   g  and  12   g  and the inside of the housing  2   g , so if the plunger  4   g  is in an oblique position in the housing  2   g  in the region of the play  55 , there is no contact between the plunger  4   g  and the inside  2   g . The double-trough-shaped configuration of the plunger  4   g  and the friction insert  26   g  causes the plunger  4   g  to be automatically centred in two dimensions in the sectional plane illustrated in  FIG. 14  and continually brought back into the central position. Moreover, this avoids hard striking between the plunger  4   g  and the housing  2   g.