Abstract:
A telescopic extension ( 1 ) comprises an inner tube ( 2 ), an outer tube ( 3 ) and a sleeve ( 4 ) in which a constraining element ( 21 ) and a thrust slider ( 30 ) are movably supported; the constraining element ( 21 ) is capable of making integral the inner tube ( 2 ) and the outer tube ( 3 ) and the thrust slider ( 30 ) is connected to an actuating element ( 40 ) and is engaged with the constraining element ( 21 ) under the action of a spring ( 31 ); the constraining element ( 21 ) consists of a projection of an elastic tongue ( 16 ) having one end ( 19 ) formed as one piece with the sleeve ( 4 ).

Description:
This application is the US national phase of international application PCT/EP01/12396 filed 23 Oct. 2001, which designated the US. 
   BACKGROUND 
   I. Field of the Invention 
   The present invention relates to a telescopic extension for an electric household appliance. 
   II. Related Art and Other Considerations 
   EP-B1-0 520 534 discloses a telescopic extension for a vacuum cleaner, comprising an inner tube and an outer tube sealingly slidable one inside the other, a sleeve, a means for constraining the inner tube and outer tube, a thrust slider and an actuating pushbutton. 
   The inner tube is provided with a row of recesses having a predefined shape and the outer tube is provided with an end tubular portion with a flared shape which is formed as one piece therewith and inside which the sleeve is fastened. 
   The constraining means consists of a cylinder piece integral with a plate provided with a pin. By means of the pin and the plate, the cylinder piece is rotatably supported in a hollow seat of the sleeve. The seat has, formed in it, a slit by means of which the cylinder piece is able to engage with a recess of the inner tube and disengage from the recess. 
   In this telescopic extension, the thrust slider is operationally connected to the actuating pushbutton, is slidably supported inside the seat of the sleeve and is subject to the action of resilient means. 
   The resilient means cause the thrust slider to engage with the plate integral with the cylinder piece to force the latter into the recess of the inner tube and lock the inner tube inside the outer tube. As a result, the extension assumes a predefined length. 
   In order to adjust the length of the extension, the actuating pushbutton is pushed manually against the action of the resilient means so that the thrust slider is able to disengage from the plate and leave the cylinder piece free to come out of the recess of the inner tube, releasing the inner tube from the outer tube. By means of sliding of the inner tube inside the outer tube, the extension assumes the desired length. 
   In order to assemble the extension, the sleeve is fitted onto the inner tube and the constraining means, the slider/pushbutton assembly and the resilient means are pre-mounted in the hollow seat of the sleeve. Then, the inner tube is mounted inside the outer tube and the sleeve is inserted into the end tubular portion, centred with respect thereto, passing the slider/pushbutton assembly through an end opening of the outer tube. 
   The object of the present invention is to improve the abovementioned extension, reducing the number of components and making assembly easier. 
   SUMMARY 
   The present invention relates to a telescopic extension for an electric household appliance, comprising: 
   a) an inner tube and an outer tube slidable one inside the other, 
   b) a sleeve fastened to said outer tube, 
   c) a constraining means capable of making integral said inner tube and said outer tube, 
   d) a thrust slider which can be engaged with said constraining means under the action of resilient means, and 
   e) actuating means operationally connected to said thrust slider, 
   f) said inner tube being provided with a row of recesses having a predefined shape, 
   g) said sleeve being arranged between said inner tube and said outer tube, 
   h) said constraining means and said thrust slider being movably supported by said sleeve, 
   i) said thrust slider acting on said constraining means under the action of said resilient means to force said constraining means into a recess of said inner tube and lock said inner tube with respect to said outer tube, 
   j) said actuating means being capable of disengaging said thrust slider from said constraining means to leave said constraining means free to move radially and come out of said recess, releasing said inner tube from said outer tube and allowing said inner tube to slide with respect to said outer tube in order to adjust the length of said extension, 
   k) said constraining means having an appendix, characterized in that 
   l) said appendix consists of a resilient tongue having one end formed as one piece with said sleeve, said resilient tongue being radially movable with respect to said sleeve, 
   m) said constraining means consists of a projection on said resilient tongue, and 
   n) said thrust slider can be engaged with said resilient tongue to force said projection into a recess of said inner tube and thus lock said inner and outer tubes and can be disengaged from said resilient tongue to allow said projection to come out of said recess of said inner tube and thus release said inner and outer tubes. 
   Preferably, said sleeve has a longitudinal cavity able to house said thrust slider and said resilient means. 
   Advantageously, said longitudinal cavity has an opening inside which said resilient tongue is located, said end of said resilient tongue being formed as one piece with a wall of said longitudinal cavity. 
   Preferably, said sleeve has an internal longitudinal boss which is located underneath said longitudinal cavity and said inner tube has a longitudinal groove with which said internal longitudinal boss of said sleeve is coupled in order to centre said sleeve with respect to said inner tube. 
   Preferably, said longitudinal groove of said inner tube has a bottom wall in which said recesses are present. 
   Advantageously, said outer tube has a lateral opening which extends as far as one end thereof and said sleeve has an external longitudinal relief which engages with said lateral opening to couple said outer tube with said sleeve and centre said outer tube with respect to said sleeve. 
   Preferably, said sleeve is provided with a collar against which said end of said outer tube comes into contact, said collar and said external relief having a thickness substantially equal to that of said outer tube so that it remains flush with said collar and said external relief. 
   Advantageously, said thrust slider is provided with an upper head able to be inserted by means of pressure into a niche in said actuating means. 
   Preferably, said sleeve, said resilient tongue and said projection are made of plastic material. 
   Advantageously, said outer tube has a cross-section with a substantially constant diameter. 
   The telescopic projection according to the invention has the advantage that it is compact, low-cost and simple to assemble. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Characteristic features and advantages of the invention will now be illustrated with reference to an embodiment shown by way of a non-limiting example in the accompanying drawings, in which: 
       FIG. 1  is a partial, longitudinal sectional view of a telescopic extension for an electric household appliance according to the invention, in the locked condition; 
       FIG. 2  shows the extension according to  FIG. 1  in the unlocked condition; 
       FIG. 3  is a cross-sectional view taken along the plane III—III in  FIG. 1 ; 
       FIG. 4  is a partial top view, on a reduced scale, of the extension of  FIG. 1 ; 
       FIG. 5  is a partial, perspective view of an outer tube, a sleeve and an inner tube of the extension of  FIG. 1  in the disassembled condition; 
       FIG. 6  is a top view of the sleeve of the extension of  FIG. 1 ; 
       FIG. 7  is a longitudinal sectional view of the sleeve of  FIG. 6 ; 
       FIG. 8  is a cross-sectional view taken along the plane VIII—VIII in  FIG. 7 ; 
       FIG. 9  is a bottom view of a pushbutton and a thrust slider of the extension of  FIG. 1 ; 
       FIG. 10  is a longitudinal sectional view of the pushbutton and the thrust slider of  FIG. 9 ; 
       FIG. 11  is a cross-sectional taken view along the plane XI—XI in  FIG. 10 ; 
       FIGS. 12 and 13  are respectively a right-hand side view and top view of the pushbutton and thrust slider of  FIG. 9 . 
   

   DETAILED DESCRIPTION 
     FIGS. 1 ,  2  and  3  show a telescopic extension  1  for an electric household appliance, such as a vacuum cleaner. The extension  1  comprises an inner tube  2 , an outer tube  3  and a sleeve  4  arranged between the inner tube and the outer tube. 
   The inner tube  2  and outer tube  3  are sealingly slidable one inside the other. A sealing gasket arranged between inner tube and outer tube is not shown. 
   The inner tube  2  has a longitudinal groove  5 , with a substantially parallelepiped shape, having a bottom wall  6  ( FIG. 4 ) in which a row of recesses  7  with a partially cylindrical shape is formed. 
   The sleeve  4  has a longitudinal cavity  10  ( FIGS. 6–8 ), an external relief  11 , a collar  12  and an internal boss  13  ( FIG. 7 ). The external relief  11  has a substantially parallelepiped shape and is aligned with the cavity  10 . The internal boss  13  has a substantially parallelepiped shape and a length nearly the same as that of the sleeve  4 . 
   The cavity  10  has a bottom wall  14  in which an opening  15  is formed. A resilient tongue  16  integral with the sleeve  4  is located in the opening  15 . The resilient tongue  16  projects from a wall  18  of the opening  15  and has one end  19  formed as one piece with the wall  18 . The resilient tongue  16  has on the upper side an inclined ramp  20  and on the lower side a tooth-shaped projection  21 . The resilient tongue  16  is movable radially with respect to the sleeve  4  and, during its centripetal radial movements, causes the projection  21  to penetrate into a recess  7  of the tube  2  ( FIG. 1 ), whereas, during its centrifugal radial movements, it extracts the projection  21  from the recess  7  ( FIG. 2 ). Therefore, the projection  21  forms a means for constraining the inner tube  2  and outer tube  3 , the sleeve  4  being made integral with the outer tube  4 , as will be illustrated further below, and the resilient tongue  16  forms an appendix of the projection  21 . 
   The outer tube  3  has a lateral opening  22  which extends as far as one end  23  and engages with the external relief  11  of the sleeve  4  until the end  23  of the outer tube comes into contact against the collar  12  of the sleeve  4  ( FIG. 4 ). Thus the outer tube is coupled with the sleeve  4  and is centred with respect thereto, remaining flush with the collar  12  and with the relief  11  because the latter have a thickness which is practically the same as that of the outer tube  3 . 
   The outer tube  3  is fastened to the sleeve  4  by means of two indentations—not shown—which penetrate into two notches  24  on the sleeve  4  ( FIGS. 5 and 6 ). The indentations are formed at the moment of assembly by means of deformation of the wall of the tube  3 . 
   The longitudinal cavity  10  of the sleeve  4  houses a thrust slider  30  and a helical spring  31 . 
   The thrust slider  30  ( FIGS. 9–12 ) consists of a rectangular plate  32  having an inclined wall  33  able to remain in contact with the inclined ramp  20  of the tongue  16 , and a tapered wall  34 . A head  35  which is formed as one piece with the plate projects upwards from the plate  32 . The head  35  and the plate  32  have a blind hole  36  in which the spring  31  is partially housed. The spring  31  reacts against a wall  37  of the cavity  10  in the sleeve  4  and is mounted pre-stressed so that the inclined wall  33  of the slider  30  is normally in contact with the inclined ramp  20  of the resilient tongue  16  ( FIG. 1 ) and pushes the projection  21  to penetrate into a recess  7  of the inner tube  2 . In this way, the tubes  2  and  3  are rigidly joined together and form an extension  1  with a predefined length. 
   A pushbutton  40  ( FIGS. 9–13 ) is mounted on the head  35  of the thrust slider  30  ( FIGS. 9–13 ). The pushbutton  40  has a seat  41  provided with a niche  42  into which the head  35  is inserted with pressure. Thus pushbutton  40  and slider  30  are locked together by means of interference. 
   The thrust slider  30  and the pushbutton  40  may be formed as one piece. 
   The tubes  2  and  3  are made, for example, of painted aluminium or stainless-steel sheet metal, which is chrome-plated externally. 
   The sleeve  4  is made, for example, of a suitable plastic material. The thrust slider  30  and the pushbutton  40  are also made of a suitable plastic material. 
   The plate  32  of the slider  30  has an elongated and flattened form. It has a thickness practically equal to the depth of the cavity  10  in the sleeve  4 . Thus the plate  32  remains embedded inside the cavity  10  and is flush with the external surface of the sleeve  4 . 
   The extension  1  has transverse dimensions which are minimized. Its compact form is also due to the fact that the resilient tongue  16  is provided with the tooth-shaped projection  21  which engages with the indented, concave, recesses  7  of the inner tube  2 . The increases in transverse dimensions of the inner tube, which would occur with a tongue which can be engaged with outward projecting protrusions of the inner tube, are thus avoided. 
   The extension  1 , in addition to having a simple and compact design, is also very resistant to stresses because the resilient tongue  16  has a stress resistance much greater than that of a tongue which can be engaged with protrusions projecting from the inner tube and which must have a curved end. 
   Another advantage of the extension  1  lies in the fact that the contact between the inclined wall  33  of the slider  30  and the inclined ramp  20  of the tongue  16  extends over a surface and any wear which may occur with use of the extension  1  is uniformly distributed over the entire surface. The presence of the spring  31  prevents the formation of play between the slider  30  and the tongue  16  and ensures correct contact also after prolonged use of the extension. 
   In order to adjust the length of the extension  1 , the pushbutton  40  is operated manually, displacing it from the position shown in  FIG. 1  to the position shown in  FIG. 2  so that the slider  30  separates from the resilient tongue  16  and leaves it free to be raised to extract the projection  21  from the recess  7  of the tube  2 , inside which it is inserted. 
   This allows sliding of the tube  2  inside the tube  3  until the desired length of the extension  1  is achieved. 
   Assembly of the telescopic extension  1  is performed by fitting the sleeve  4  onto the inner tube  2  so that its internal boss  13  is coupled with the longitudinal groove  5  of the inner tube. The slider  30  with the spring  31  is then mounted in the cavity  10  of the sleeve  4  in a position where its inclined wall  33  is in contact with the ramp  20  of the tongue  16  and pushes the projection  21  into a recess  7  of the inner tube  2 . 
   At this point, the outer tube  3  is fitted onto the sleeve  4 , coupling its lateral opening  22  with the external relief  11  until its end  23  is brought into contact against the collar  12  of the sleeve. In this position, the head  35  of the slider  30  projects outside the opening  22  and the pushbutton  40  may be press-fitted thereon. Therefore, the assembly of the extension  1  requires only a few simple and easy operations.