Patent Publication Number: US-2011067459-A1

Title: Washing machine

Description:
The invention relates to a washing machine according to the preamble of claim  1 . 
     To support a balanced washing operation of the washing machine, the outer tub of the washing machine inside which the washing drum rotates is fitted with counterweights. These may be fastened to the outer tub by means of screwed connections. 
     A screwed connection for fastening a counterweight to an outer tub of a washing machine is known from US 2005/005650 A1. The screwed connection has, when assembled, a screw guided through the counterweight, the screw being screwed into a receiving thread of the outer tub. The screw head abuts against an abutment surface of the counterweight, the abutment surface facing away from the outer tub. 
     A further screwed connection for fastening the counterweight to the outer tub is known from DE 42 38 685 A1, in which, when assembled, the screw head abuts via a washer configured as a spring plate against the abutment surface of the counterweight facing away from the outer tub. The screw head is screwed into a screw boss configured in a same material and in one piece with the outer tub. The screw boss projects through an assembly hole into the counterweight. 
     To secure the screwed connection between the counterweight and the outer tub non-rotatably, it is known for a screw to be used, between the screw head and the screw shaft of which an approximately rectangular securing collar is provided. The securing collar of the screw is inserted into a corresponding through opening of a securing plate which is in turn arranged non-rotatably relative to the counterweight. To prevent rotation, a special screw, configured with the securing collar, and a securing plate are therefore required. The outlay in terms of assembly and components to secure the screw non-rotatably is therefore correspondingly large. 
     The object of the invention is to provide a washing machine in which the counterweight is fastened to the outer tub with a reduced number of components. 
     The object is achieved in a washing machine having the features of claim  1 . Advantageous further developments of the invention are disclosed in the subclaims which are supported in the description below and in the drawings. 
     According to the characterizing clause of claim  1 , at least one of the bracing elements at the ends is configured as a spiked plate having at least one spike-type projection. When the counterweight is fastened, the spike-type projection is forced in the direction of bracing into the fastening section of the outer tub and the spiked plate is thereby non-rotatably secured. An additional securing plate with associated securing collar of the screw, as used in the prior art, can thus, for the purposes of simplifying assembly and reducing the number of components, be dispensed with. Preferably, a multiplicity of spike-type projections is provided. 
     The two bracing elements at the ends can for the purposes of the invention be a threaded nut and/or a screw head. The bracing element can optionally also be a washer which is forced by means of the threaded nut or the screw head against the fastening section of the outer tub. 
     The spiked plate according to the invention can preferably be configured as a spiked nut which can be screwed together with the screw element. Irrespective of the screw used, the spiked nut is adapted according to the invention, whereas the screw can be configured conventionally, with no additional rotation-preventing elements. 
     The spiked plate can be a deep-drawn sheet metal part made, for example, of a spring-hardened stainless steel sheet, as a result of which the spiked plate is, in production engineering terms, easy to produce. 
     Alternatively, the spiked plate can also be configured as a screw head of the screw element. Here, the spike-type projections of the screw head point in the direction of the threaded shaft of the screw element. The screw serves a dual function here: both for bracing and for non-rotatably securing the screwed connection. The spike-type projections here are arranged on the underside of the screw head facing toward the outer-tub fastening section. 
     As a further alternative, the spiked plate can also be a washer which is associated with the screw head of the screw element. The washer is configured such that it is non-rotatably connected to the screw head. For such a non-rotatable connection the washer can have a recess, the inner contour of which is adapted to the outer contour of the screw head (e.g. a hexagonal inner contour). When fastened, the screw head engages in a form-locking manner with the inner contour of the recess of the washer, as a result of which the screw cannot rotate relative to the washer. 
     To simplify assembly, the at least one spike-type projection of the spiked plate can have a rounded spike tip, which, when the screwed connection has not yet been tightened prior to assembly, can give rise to the following advantages: prior to assembly, the spiked plate with its spike-type projection still abuts loosely against the outer-tub fastening section. Because the tip of the spike-type projection is rounded, the spiked plate can readily be displaced along the fastening section. Such a displacement would, in the case of an angular or sharply pointed spike tip, lead to the spike-type projection “catching” in the fastening section and consequently to a stiff sliding motion. 
     The spiked plate can preferably have a polygonal peripheral profile with an even number of sides. This can facilitate the application of a tool to the spiked plate. The spiked plate can, for the sake of further simplicity, have at least one pair of parallel opposing lateral surfaces. The lateral surfaces of the spiked plate serve a duel function: as a tool application and as lateral stops to further secure the spiked plate non-rotatably. For such additional rotation prevention, the spiked plate according to the invention can be associated with at least one rotation stop configured on the fastening section, which, besides the at least one spike-type projection of the spiked plate, ensures that the screwed connection is non-rotatably secure. To this end, the rotation stop configured on the fastening section can have two parallel opposite side walls. 
     The spiked plate with its lateral stop surfaces can then be non-rotatably arranged between these side walls. 
     To increase the functionality of the spiked plate, the latter can have an inner screw-element fastening section and an outer plate-shaped abutment section which abuts under pressure against the outer-tub fastening section. The at least one spike-type projection is provided on the plate-shaped abutment section. When the counterweight is fastened, the inner screw-element fastening section engages rigidly with the screw. In a special embodiment, the screw-element fastening section can be a receiving thread into which the screw is screwed. 
     For a permanently reliable fastening of the counterweight to the outer tub, it is preferable for an additional pretensioning element to be associated with the screwed connection. The pretensioning element permanently maintains a pretension between the bracing elements and the counterweight and/or the outer-tub fastening section, including also in the event of strong dynamic stresses on the screwed connection caused by operation of the washing machine and in the event of retardations and plastic or entropy-plastic deformations, as can occur under long-term stressing, particularly of an outer-tub fastening section made of plastic and/or other (plastic) parts directly associated with the screwed connection. 
     The pretensioning element may according to the invention be integrated in the spiked plate. The pretensioning element is advantageously a plate-type spring section, which is provided between the inner screw-element fastening section and the outer plate-shaped abutment section of the spiked plate. The plate-type spring section can be configured as a section of a cone. Where the spiked plate is configured as a spiked nut, a receiving thread for the screw element can be provided in the inner screw-element fastening section. The receiving thread can be provided in a central base region of the spiked plate. Alternatively, the inner screw-element fastening section can have a threaded sleeve on the inside of which the receiving thread is provided. 
     The threaded sleeve can here be provided on the side of the spiked plate facing away from the spike-type projections. Likewise, the threaded sleeve can also be provided on the side of the spiked plate facing toward the spike-type projections. Where the length is appropriate, the threaded sleeve here can, together with the threaded shaft, be guided through the fastening section of the outer tub. The threaded shaft of the screw does not therefore come directly into contact with the outer-tub fastening section, but only the smooth exterior of the threaded sleeve of the spiked plate. 
     Where the spiked plate is configured as a screw head, the inner screw-element fastening section can also be non-rotatably connected, in particular integrally connected, to the screw element. 
     The outer-tub fastening section can have a laterally open insertion slot, through which the screw element projects. Where the bracing elements are screwed loosely, one of the bracing elements can therefore be inserted into the laterally open insertion slot and displaced therein to a predetermined definitive fastening position. The fastening section of the outer tub can, in addition, form a guide channel. The insertion slot can open into this guide channel and extend in the longitudinal direction of same. When the screwed connection is assembled, the spiked plate can then be displaced along the guide channel and the screw element along the insertion slot to a definitive fastening position. 
     The fastening section is preferably configured together with the outer tub in the same material and in one piece. The outer tub and/or the fastening section can in production engineering terms advantageously be made of plastic. In a method for fastening the counterweight to the outer tub, a screw of the screwed connection according to the invention can firstly be guided through the counterweight. The end of the screw guided through the counterweight can then loosely be screwed to a bracing element at the end. The bracing element at the end is the spiked plate according to the invention. The loosely screwed bracing element at the end can then be inserted into the guide channel of the outer-tub fastening section. The counterweight can then, to adjust position, be displaced with the loosely screwed bracing element along the guide channel; and when the arrangement of the counterweight is correct, the screwed connection can be tightened in its definitive fastening position. 
    
    
     
       Five exemplary embodiments of the invention will be described below with the aid of the attached drawings, in which: 
         FIG. 1  shows according to the first exemplary embodiment, in a schematic partial view, an upper counterweight which is fastened by means of screwed connections to the outer tub of the washing machine; 
         FIG. 2  shows, in an enlarged sectional representation, one of the screwed connections between the counterweight and the outer tub; 
         FIG. 3  shows, in a perspective representation, a threaded nut used for the screwed connection; 
         FIG. 4  shows a spiked plate embodied as a threaded nut, according to the second exemplary embodiment; 
         FIG. 5  shows a spiked plate embodied as a threaded nut, according to the third exemplary embodiment; 
         FIG. 6  shows a spiked plate embodied as a screw head, according to the fourth exemplary embodiment; and 
         FIG. 7  shows a spiked plate embodied as a washer, according to the fifth exemplary embodiment. 
     
    
    
       FIG. 1  shows in a schematic side view a partial area of an outer tub  1  of a washing machine and a counterweight  3  fastened to the top of the outer tub  1 , which counterweight ensures a balanced washing operation. The elongately configured counterweight  3  extends transversely relative to a central axis (not shown) of the hollow cylindrical outer tub  1  and lies at its two opposing ends on hollow support profiles  5  of the outer tub  1 . The counterweight  3  is mounted at each of its longitudinal ends on the associated hollow support profile  5  of the outer tub  1  by means of a screwed connection  7 . 
     The counterweight  3  is produced in a known manner from a cast material, for example cast iron or concrete, or another suitable material. The outer tub  1  is an injection-molded plastic part. The hollow support profile  5  is molded integrally onto the outer tub  1  in an easy-to-manufacture manner. 
       FIG. 2  shows one of the screwed connections  7  from  FIG. 1  in an enlarged partial sectional view. The opposite screwed connection (not shown) is configured identically. 
     As can be seen from  FIG. 2 , the screwed connection  7  is configured in three parts, with a screw  9  or screw element, a washer  11  and a spiked plate  13  embodied as a threaded nut. The screwed connection  7  is shown in  FIG. 2  with the counterweight  3  and the outer tub  1  in the assembled position. The screw  9  is guided with its threaded shaft  15  through an assembly hole  17  of the counterweight  3 . Here, the screw head  19  is supported via the washer  11  on an abutment surface  21  of the counterweight  3  facing away from the outer tub  1 . The abutment surface  21  here is the base of a conically extended countersunk hole  23 . 
     The threaded shaft  15  guided through the assembly hole  17  projects with its shaft end into an insertion channel  25  of the hollow support profile  5 . The insertion channel  25  extends perpendicular to the plane of the drawing of  FIG. 2  and is delimited by two side walls  27  and by an upper covering wall  29  connecting the two side walls  27 . 
     In the present exemplary embodiment, the upper covering wall  29  is a fastening section of the outer tub  1 . This fastening section  29  and the counterweight  3  are braced according to  FIGS. 1 and 2  between the screw head  19  and the spiked plate  13  which are the bracing elements at the ends of the screwed connection  7 . A narrow insertion slot  31  which extends along the guide channel  25  and through which the threaded shaft  15  projects, is provided in the covering wall  29  for this purpose. The insertion slot  31  is laterally open and opens into the guide channel  25   
     The spiked plate  13  embodied as a threaded nut is screwed inside the guide channel  25  to the (in  FIG. 2 ) lower end of the threaded shaft  15 . The spiked plate  13  thus engages behind the covering wall  29 . In the assembled position shown, the counterweight  2  and the covering wall  29  of the outer tub  1  are thus braced between the screw head  19  and the spiked plate  13 . 
     The spiked plate  13  embodied as a threaded nut is shown in detail in  FIG. 3  in an enlarged perspective view. The threaded nut  13  is made of a spring-hardened stainless steel sheet with a material thickness of c. 1 mm. The spiked plate  13  has according to  FIG. 3  an inner screw-element fastening section  32 . The inner screw-element fastening section  32  is fitted here with an internal thread  33  with which the end of the shaft  15  of the screw  9  can be screwed together. 
     As can further be seen from  FIG. 3 , the screw-element fastening section  32  of the spiked plate  13  has a centrally arranged threaded sleeve  35  in which the internal thread  33  is provided. Connected to the threaded sleeve  35  in the direction of the outer contour of the spiked plate  13  is a conical section which forms a plate-type spring section  37  (in the manner of a plate spring). On its outer edge region, the spring section  37  merges integrally into a plate-shaped, flat abutment section  39 , extending in the radial direction of the spiked plate  13 . The abutment section  39  has a uniform octagonal outer contour with opposite pairs of sides or stop surfaces  41  respectively running parallel to one another. When assembled, the spiked plate  13  presses with the lower (in  FIG. 3 ) surface of the abutment section  39  against the covering wall  29 . 
     A permanently non-rotatable seating of the spiked plate  13  embodied as a threaded nut is for operating safety of great importance. According to the invention, projections  43  with rounded spike tips are therefore provided on the side of the spiked plate  13  facing the covering wall  29 . The spike-type projections  43  are provided on the side of the spiked plate  13  facing away from the threaded sleeve  35  and extend in a direction parallel or substantially parallel to the longitudinal direction of the threaded shaft  15 . When the counterweight  3  is fastened, the spike-type projections  43  are pressed by the clamping forces of the screwed connection in the direction of bracing into the plastic material of the covering wall  29 . 
     For additional rotation security to prevent a rotational movement of the spiked plate  13 , the distance b shown in  FIG. 3  between two opposing lateral stop surfaces  41  is dimensioned such that each of the opposing stop surfaces  41  lies with limited play c opposite the facing side wall  27  of the outer-tub hollow support profile  5  (see  FIG. 2 ). The two side walls  27  of the hollow support profile  5  therefore act as a rotation stop, which additionally limits a rotational movement of the spiked plate  13 . 
     To fasten the counterweight  3  to the outer tub  1 , the screw  9  is firstly guided from the side of the counterweight  3  facing away from the outer tub  1  through the assembly opening  17 . The spiked plate  13  is then loosely screwed to the lower end of the shaft  15  in  FIG. 2 . This loose screwed connection can be effected still independently of the outer tub  1 . To connect the counterweight  3  to the outer tub  1 , the spiked plate  13  which is loosely connected with the screw  9  is then inserted into the laterally open guide channel  25  of the outer tub  1 . The threaded shaft  15  of the screw  9  now projects through the insertion slot  31 , while the covering wall  29  is arranged between the threaded nut  13  and the counterweight  3 . In this condition, the loosely screwed spiked plate  13  can be displaced along the guide channel  25  and the screw  9  along the insertion slot  31  to a correct or definitive fastening position. 
     After correct positioning of the counterweight  3  has been carried out, the screwed connection  7  is tightened by means of a tool applied to the screw head  19 . 
     To simplify the tightening process, the spiked plate  13  is non-rotatably held by means of its lateral stop surfaces  41  between the two side walls  27 . On the other hand, the play c provided between the stop surfaces  41  of the spiked plate  13  and the side walls  27 , and the rounded projections  43  ensure that, when the spiked plate  13  is loosely screwed on, the spiked plate  13  can be displaced smoothly inside the guide channel  25 . 
       FIG. 4  shows the spiked plate  13  according to the second exemplary embodiment. The basic structure and mode of operation of the spiked plate  13  shown in  FIG. 4  corresponds to the structure and mode of operation of the spiked plate  13  of the first exemplary embodiment as shown in  FIGS. 1 to 3 , so corresponding reference characters are used for features that work the same, and the description below describes, in particular, the differences in relation to the first exemplary embodiment. 
     Accordingly, the receiving thread  33  for the screw  9  is likewise provided in the inner screw-element fastening section  32  of the spiked plate  13 . In contrast to the first exemplary embodiment, however, the receiving thread  33  is not provided inside the threaded sleeve  35  but rather in a central base region  45 . The central base region  45  merges via the plate-type spring section  37  into the outer plate-shaped abutment region  39  of the spiked plate. On the (in the representation according to  FIG. 4 ) top side of the abutment region  39 , the rounded spike-type projections  43  are again provided. 
       FIG. 5  shows the spiked plate  13  according to the third exemplary embodiment. The spiked plate shown in  FIG. 5  has—as in the first exemplary embodiment—a central threaded sleeve  35 , connected to the (in  FIG. 5 ) lower end region of which is the plate-type spring section  37 , which merges into the outer plate-shaped abutment section  39 . 
     In contrast to the first exemplary embodiment, however, the threaded sleeve  35  is not provided on the side of the spiked plate  13  facing away from the spike-type projections  43 , but rather on the side facing toward the spike-type projections  43 . Viewed in the axial direction of the spiked plate  13 , indicated in  FIG. 5  by a dot-dash line, the central threaded sleeve  33 , the spring section  37  and the radially outer abutment section  39  are therefore partially “nested”, as a result of which the overall height of the spiked plate  13  is reduced in comparison to the first exemplary embodiment. This spiked plate  13  is therefore particularly suitable for a very shallow guide channel. 
     With an appropriate length, the threaded sleeve  35  is guided together with the threaded shaft  15  screwed therein through the insertion slot  31  of the covering wall  29  of the hollow support profile  5 . The edges of the insertion slot  31  are not therefore directly in contact with the threaded shaft  15  of the screw  9 . Rather, the smooth outside of the threaded sleeve  35  advantageously comes into contact with the edges of the insertion slot, as a result of which the threaded shaft  15  is displaced smoothly inside the insertion slot  31 . 
       FIG. 6  shows the spiked plate  13  according to the fourth exemplary embodiment. In contrast to the first three exemplary embodiments, here the spiked plate  13  is integrally configured with the screw  9  as the screw head thereof. The spiked plate  13  consequently has a central head section  47 . Radially outwardly adjacent to the central head section  47  is the plate-type spring section  37  which merges into the abutment section  39 . In the exploded view shown, a conventional washer  11  and a conventional threaded nut  49  are associated with the screw  9 , it being possible for said threaded nut to be screwed together with the (in  FIG. 6 ) upper end of the shaft  15  so as to brace the covering wall  29  and the counterweight  3 . When the counterweight  3  is fastened, the threaded nut  49  with its washer  11  is supported in the variant according to  FIG. 6  on the abutment surface  21  of the counterweight  3  facing away from the outer tub  1 , as shown in  FIG. 2 . In a corresponding manner, the spiked plate configured as a screw head is arranged inside the guide channel  25  of the hollow support profile  5 . 
       FIG. 7  shows the screwed connection  7  according to the fifth exemplary embodiment, likewise in an exploded view. As can be seen from  FIG. 7 , the spiked plate  13  is configured here as a washer of the screw head  19 . The spiked plate  13  here has a central recess  51 , the inner contour of which fits in a form-locking manner with the outer contour of the screw head  19 . Adjacent to the central recess  51  is the plate-type spring section  37  which again merges into the radially extending plate-shaped abutment section  39 . Arranged in turn on the abutment section  39  are the spike-type projections  43 . The end of the shaft  15 , which is fashioned with a thread, of the screw  9  is likewise screwed to a conventional threaded nut  49 . When the counterweight  3  is fastened, the spiked plate  13  is arranged, together with the screw head  19  arranged in its recess  51 , in the guide channel  25 . Here, the spiked plate  13  sits non-rotatably on the covering wall  29  with its projections  43  pressed into the plastic material of the covering wall  13 . Consequently, due to the form-locking connection between the outer contour of the screw head  19  and the inner contour of the recess  51 , the screw head  19  is non-rotatably connected to the spiked plate. 
     Reference characters in the claims, the description and the drawings serve merely to provide a better understanding of the invention and are not intended to limit the scope of protection. 
     LIST OF REFERENCE CHARACTERS 
     
         
           1  outer tub 
           3  counterweight 
           5  hollow support profile 
           7  screwed connection 
           9  screw/screw element 
           11  washer 
           13  spiked plate 
           15  shaft/threaded shaft 
           17  assembly hole 
           19  screw head 
           21  abutment surface 
           23  countersunk hole 
           25  insertion channel/guide channel 
           27  side walls 
           29  covering wall/fastening section 
           31  insertion slot  31   
           32  screw-element fastening section of  13   
           33  internal thread 
           35  threaded sleeve 
           37  plate-type spring section 
           39  abutment section 
           41  stop surfaces 
           43  spike-type projections of  13   
           45  base region 
           47  head section 
           49  threaded nut 
           51  recess 
         a material thickness 
         b distance 
         c play between  27  and  41