Abstract:
A telescopic extension ( 1 ) for an electric household appliance is described, said extension comprising: an inner tube ( 2 ) and an outer tube ( 3 ) which are slidable one inside the other; a sleeve ( 4 ) fixed to the outer tube; a fastener ( 5 ) able to lock together said inner tube and the outer tube; a slider co-operating with the fastener via the action of a first spring and a second spring ( 73 ); and an actuating handle ( 8 ) operationally connected to said slider. The inner tube is provided with a plurality of recesses ( 23 ) able to receive, at least partially, the fastener. The outer tube comprises a tunnel ( 31 ) for retaining the slider and for guiding it during displacement. The tunnel is formed by suitably shaping the outer tube. The sleeve comprises a recessed area ( 46 ) for retaining the slider and guiding it during displacement.

Description:
This application is the U.S. national phase of International Application No. PCT/EP2007/002323 filed 15 Mar. 2007 which designated the U.S. and claims priority to IT MI2006A000616 filed 31 Mar. 2006, the entire contents of each of which are hereby incorporated by reference. 
     The present invention relates to a telescopic extension for an electric household appliance, such as a vacuum cleaner and the like. 
     BACKGROUND 
     The known telescopic extensions for electric household appliances comprise an inner tube and an outer tube sealingly slidable one inside the other, a sleeve, a fastening means adapted to lock together the inner tube and outer tube, a thrusting slider engaging with the fastening means via the action of resilient means and actuating means operationally connected to the thrusting slider. In these extensions, the inner tube is provided with a row of notches of predefined shape and the sleeve is fixed to the outer tube. 
     Telescopic extensions of the abovementioned type are known, for example, from EP 1 092 383 A1, EP 0 520 534 B1, EP 0 987 976 B1 and EP 01993418.1, all in the name of the same Applicant. The telescopic extensions mentioned above are all very efficient and practical to use. 
     Other telescopic extensions are known from EP 0 552 481 B1, EP 0 553 482 A1 and DE 196 15 814 A1. 
     In particular, EP 0 552 481 describes a telescopic tube for electric household appliances with an inner tube and outer tube slidable one inside the other; a sleeve fixed to the outer tube; and a fastening means able to lock together the inner tube and the outer tube. An actuating pushbutton consisting of two pieces retained in a central position by two springs is provided in the telescopic tube according to EP 0 552 48. The bottom piece of the actuating pushbutton has outwardly projecting parts which are engaged via a cavity in the top part of the two-piece pushbutton. The sleeve is housed inside a cavity formed by flaring the outer tube in the vicinity of its end. 
     The telescopic tube for an electric household appliance according to EP 0 552 481 has various drawbacks. The flaring is a costly operation which increases greatly the cross section of the telescopic tube. Moreover, it greatly stresses the metallic walls of the tube, weakens them and very often causes damage which results in rejection of the finished part. This results in high production costs. In order to prevent the outer tube from rotating with respect to the inner tube, a longitudinal relief must be necessarily provided in the inner tube and a corresponding longitudinal recess provided in the outer tube. 
     The telescopic tube for an electric household appliance according to EP 0 552 481 is difficult to assemble owing to the outwardly projecting parts of the bottom piece of the actuating pushbutton. In fact, the bottom part of the pushbutton cannot be mounted by inserting the sleeve in the outer tube. The bottom part of the pushbutton must be mounted from above and this operation is difficult owing to the presence of the two springs. Assembly therefore cannot be automated. 
     The telescopic tube for an electric household appliance according to EP 0 552 481 is not considered safe owing to the fact that the top part of the pushbutton may be separated from the bottom part and the entire device may therefore break and become unusable. 
     The Applicant, in particular, has perceived the need to reduce the number of components which form the mechanism and provide a mechanism which is easy to assemble. 
     The Applicant has also perceived the need to provide a telescopic extension which is strong and entirely reliable in any operating condition. 
     According to the technology disclosed herein a telescopic extension for an electric household appliance is provided, said extension comprising: an inner tube and an outer tube which are slidable one inside the other; a sleeve fixed to the outer tube; a fastening means adapted to lock together the inner tube and the outer tube; a slider co-operating with the fastening means via the action of a first spring-land a second spring; and an actuating handle operationally connected to said slider. The inner tube is provided with a plurality of recesses able to receive, at least partially, the fastening means. The outer tube comprises a tunnel for retaining the slider and for guiding it during displacement; the tunnel is formed by suitably shaping the outer tube. The sleeve comprises a recessed area for retaining the slider and guiding it during displacement. The inner tube has a depression forming a channel which extends longitudinally. Recesses for the fastening means are provided on the bottom of the channel. 
     Conveniently, the tunnel has two sides walls and a ceiling which connects together the two side walls. 
     In an advantageous embodiment, the tunnel comprises at least two windows formed in the ceiling of the tunnel, the two windows defining between them a central connecting strip which connects the two side walls of the tunnel. 
     Conveniently, the surface of the slider is in contact, at least partially, with the central connecting strip in any operating condition of the slider. The surface of the slider which is in contact, at least partially, with the central connecting strip is flat and does not have parts projecting from the ceiling of the tunnel. 
     Preferably the actuating handle comprises a longitudinal recess for receiving the tunnel of the outer tube. The actuating handle comprises two teeth projecting from the bottom of the longitudinal recess, the distance between the two teeth corresponding to the length of the slider. 
     The end surface of the teeth conveniently has a rounded form for retaining the springs. 
     The slider conveniently comprises two side holes for receiving a respective end of the two springs. 
     The actuating handle preferably consists of two pieces and comprises means for locking together the two pieces. 
     According to a second aspect, the technology disclosed herein relates to an electric household appliance comprising a telescopic extension as mentioned above. 
     The telescopic extension of the technology disclosed herein has the advantage of being extremely compact and particularly resistant to the operating stresses such as axial thrusts, transverse thrusts and twisting moments. 
     Moreover, it may be assembled using a significantly simplified process which allows a reduction in the time and production costs and may be easily automated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Characteristic features and advantages of the technology disclosed herein will now be described with reference to an embodiment represented by way of example in the accompanying drawings in which: 
         FIG. 1  is an exploded view of a section of a telescopic extension for an electric household appliance according to an embodiment of the technology disclosed herein; 
         FIG. 2  is a longitudinally sectioned view of the telescopic extension according to  FIG. 1 , mounted and in a first operating condition; 
         FIG. 3  is a longitudinally sectioned view of the telescopic extension according to  FIG. 1 , mounted and in a second operating condition; 
         FIG. 4  is a cross-sectional view of the telescopic extension according to  FIG. 1 , taken along the line  2 - 2  of  FIG. 2 ; 
         FIG. 5A  is a cross-sectional view of the sleeve, taken along the line  2 - 2  of  FIG. 2 ; 
         FIG. 5B  is a top plan view of the sleeve; 
         FIG. 5C  is a longitudinally sectioned view of the sleeve; 
         FIG. 6A  is a first longitudinally sectioned view of the actuating handle; 
         FIG. 6B  is a cross-sectional view of the actuating handle; 
         FIG. 6C  is a plan view of the actuating handle; 
         FIG. 6D  is a second longitudinally sectioned view of the actuating handle; 
         FIG. 7A  is an exploded axonometric view of the actuating handle; and 
         FIG. 7B  is an axonometric view, from the inside, of a half-part of the actuating handle; 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows, in an exploded view, a section of a telescopic extension  1  for an electric household appliance, such as a vacuum cleaner or the like. The extension  1  comprises an inner tube  2 , an outer tube  3 , a sleeve  4 , fastening means  5 , a slider  7  and an actuating handle  8 . 
     The inner tube  2  has preferably a cross-section which is roughly circular, but has a depression  21  which forms a channel  22  preferably with a flat bottom. The channel formed by the depression  21  extends longitudinally parallel to the longitudinal axis of the inner tube. Recesses  23  are provided on the bottom  22  of the channel. According to a preferred embodiment, said recesses have a substantially semi-cylindrical shape. Alternatively, they may be semi-spherical. The inner tube  2  is preferably made of metal, for example steel, aluminum or alloys thereof. 
     The outer tube  3  has preferably a cross-section which is roughly circular, but has a tunnel  31  projecting outwards from the cross-section of the outer tube  3 . The tunnel  31  extends longitudinally parallel to the longitudinal axis of the outer tube  3 . The tunnel  31  extends over a relatively short section of the outer tube  3 . By way of example, the tunnel  31  extends over about 5 cm. The height of the tunnel  31  is equal to a few mm. The outer tube  3  is preferably made of metal, for example steel, aluminum or alloys thereof. 
     The tunnel  31  is formed with two side walls  37  and a ceiling  38  which connects the two side walls  37 . It should be mentioned at this point that the tunnel  31  is not comparable in any way with a flaring (such as that described in EP 0 552 481). The flaring is a widening of the diameter of the tube along the entire circumference. This causes major stressing of the tube such that in many cases it breaks or in any case becomes unusable. Moreover, the flaring increases considerably the dimensions of the tube. The tunnel, instead, constitutes a “localized” and small-size widening of the diameter of the outer tube which can be produced easily and at a low cost. It does not cause major stressing and does not increase substantially the external dimensions. 
     Two windows  32 ,  33  are formed in the tunnel  31 . The ceiling  38  of the tunnel  31  is thus formed by three strips  34 ,  35  and  36  The strip  34  is the one situated closest to the tunnel entrance; the strip  35  is the central one; and the strip  36  is the one situated at the end of the tunnel, where it is connected to the outer tube  3  which assumes a circular cross-section. The windows  32 ,  33  may extend as far as the side walls  37  of the tunnel  31  or may terminate before them so that a thin ceiling edge remains connected to the side walls  37  opposite the windows  32 ,  33 . 
     Conveniently, two bosses  39  are provided on the outer tube  3  so as to favour locking of the sleeve  4  to the outer tube  3 . 
     The sleeve  4  has preferably a roughly circular cross-section which is also visible in  FIG. 5A . The sleeve  4  is essentially a tube, preferably made of plastic, with a thickness  41 . The outer diameter of the sleeve  4  corresponds substantially to the inner diameter of the outer tube  3 . 
     Reference shall now be made to  FIGS. 5B and 5C . 
     A ring  42  with a diameter greater than the outer diameter of the sleeve is provided at a first end of the sleeve  4 . The opposite end of the sleeve  4  is provided with two receiving notches  43  and two respective windows  44  co-operating with the bosses  39  of the outer tube  3 . An inner relief  42 ′ allows centring of the sleeve  4  with respect to the inner tube  2 . 
     A suitably shaped recessed area  45  is formed in the thickness  41  of the sleeve  4 . An opening  46 ′ for the fastening means  5  is provided in the centre of the recessed area  45 . The recessed area  45  has the shape of an elongated rectangle  46 ; it continues with two narrower sections  47  and terminates in two respective projecting blocks  48 ,  49 . The projecting blocks  48 ,  49  project from the cross-section of the sleeve  4  and have a sectional form substantially complementing that the tunnel  31 . The width of the recessed area, in the region of its rectangular central part  46 , is equal to the width of the slider  7 . 
     The slider  7  is shown in  FIGS. 1 ,  2 ,  3  and  4 . The slider  7  is a substantially parallelepiped part with a flat upper side  74  and a bottom side  75  provided with two symmetrically arranged notches  71 . Two blind holes  72  for receiving two respective cylindrical springs  73  are formed on the sides of the slider ( FIGS. 2 and 3 ). Preferably, the springs  73  have the same length and the same properties. Preferably, the slider  7  is made of metal, for example steel, aluminum or alloys thereof. Alternatively, the slider  7  may be made of plastic. 
     The fastening means  5  is shown in  FIGS. 1 ,  2 ,  3  and  4 . It is in the form of a cylinder piece  5 , but alternatively may be a spherical body. 
     The actuating handle  8  of the telescopic extension according to the technology disclosed herein is shown in  FIGS. 1 ,  2 ,  3 ,  4  and  6 . The actuating handle  8  has a tubular shape and is preferably made of plastic. Externally, it has a knurled area  81  for improving the grip in any operating condition. The ends are preferably chamfered or rounded. 
     Internally, the actuating handle has a substantially circular cross-section with a diameter substantially corresponding to the external diameter of the outer tube  3 . However, as shown in  FIGS. 6B and 6C , a longitudinal recess  82  is provided so as to receive the tunnel  31  of the outer tube  3  ( FIG. 1 ). Two teeth  83  projecting from the bottom of the longitudinal recess  82  are also provided. The end surface  85  of the teeth  83  preferably has a rounded shape for retaining the springs  73 . The distance  84  ( FIG. 6D ) between the two teeth  83  corresponds to the length of the slider  7  ( FIG. 2  and  FIG. 3 ). 
     The cross-sections in  FIGS. 2 and 3  show the telescopic extension  1  according to an embodiment of the technology disclosed herein, completely assembled and in two different operating configurations. 
     In order to assemble the telescopic extension  15  the sleeve  4  is fitted onto the inner tube  2 . The fastening means  5  is then inserted into the window  46 ′, the slider  7  is mounted and the springs are placed inside their seats  47  (preferably slightly pre-tensioned). Alternatively, the fastening means may be inserted together with the slider  7  (for example using a magnet). The sleeve thus equipped is inserted inside the outer tube  3  until the ring  42  comes up against the edge of the outer tube  3 . The height of the ring  42  with respect to the projecting block  48  is such that the ring  42  is flush with the outer tube  3 . Finally, the actuating handle is locked against the outer tube. 
     The projecting block  48  is retained by the strip  34  of the tunnel  31  and the projecting block  49  is retained by the strip  36  of the tunnel  31 . 
     The slider  7  is seated inside the recessed area  45  and in particular inside its central part  46 . The central part  46  therefore acts as a guide for the slider. The slider  7  is retained by the metallic central strip  35  of the tunnel  31 . The bottom side  75  of the slider  7  provided with the incisions  71  faces the sleeve  4 . 
     In the operating configuration shown in  FIG. 2 , the slider  7  is kept in the centre of the recessed area  45  of the sleeve  4  by means of the two springs  73 . The two cylindrical springs  73  are partially inserted inside the holes  72  of the slider and bear with their ends against the shoulder surfaces  48 ′ and  49 ′ ( FIG. 5C ) of the projecting blocks  48  and  49 . 
     In the operating configuration shown in  FIG. 2  the fastening means  5  is retained by the bottom side  75  of the slider  7  inside the recess  23  of the inner tube  2 . In this operating configuration the two tubes  2  and  3  are locked together. 
     In order to release the two tubes  2  and  3 , the actuating handle  8  is pushed to the right (as shown in  FIG. 3 ) or to the left. When the handle  8  is pushed to the right, for example, the slider  7  is correspondingly displaced to the right. The right-hand spring  73  is compressed, while the left-hand spring  73  is extended. In any case, during its displacement, the slider  7  is guided by the central part  46  of the recessed area  45  and is retained by the metallic central strip  35  of the tunnel  31 . The fastening means  5  moves out of its recess  23  and is seated inside an incision  71  and inside the opening  46 ′ of the sleeve. Owing to its shape, the fastening means (for example in the form of a cylinder piece) is able to roll on the inner tube. 
     When the cylinder piece  5  is against situated opposite a recess  23  and the force on the handle is released, locking together of the outer tube  3  and inner tube  2  will again occur. 
     According to an advantageous embodiment, the actuating handle  8  is formed by two pieces  86  and  87  ( FIGS. 7A and 7B ). Each handle half-piece  86 ,  87  comprises projecting engaging teeth  88  and/or corresponding engaging blocks  89 . When the two handle half-pieces  86 ,  87  are forced together, the engaging teeth  88  engage with the engaging blocks  89  in a permanent and lasting manner. 
     The handle for the telescopic extension according to the technology disclosed herein may be formed by two pieces also because it exerts a minimum force. In fact, the handle engages with the slider and only has the function of displacing it in one direction or the other. The slider is guided inside the recess of the sleeve and, on the opposite side, by the tunnel ceiling (and in particular by the strip  35 ). The handle must not retain the slider in position and prevent it from coming out of its seat 
     Various advantages are provided by the technology disclosed herein compared to the known telescopic extensions. One of the main advantages is the ease of assembly. The ease of assembly (and the possibility of automating assembly) is of fundamental importance in this kind of article in order to reduce costs and make the telescopic extension economically advantageous. In fact, it is sufficient to keep the slider  7  with the two springs  73  and the fastening means  5  against the sleeve and insert the sleeve thus equipped inside the outer tube. Once the sleeve has been inserted to the point where the slider  7  reaches the strip  34 , there is no longer the risk of the slider coming out of its seat. In fact, it is retained inside the tunnel  31 , in particular by the central strip  35 . The size of the windows  32  and  33  is also such that the slider is unable to pass out through them. 
     A machine (not shown) with a head-piece able to keep the cylinder piece  5 , the slider  7  and the springs  73  in position inside the sleeve  4  is used for assembly. In order to prevent the cylinder piece from coming out, obviously the sleeve  4  must be fitted onto the inner tube. As mentioned above, the inner relief  42 ′ allows centering of the sleeve  4  with respect to the inner tube  2 . The two parts are unable to rotate relative to each other. 
     The actuating handle  8  may be mounted on the outer tube very easily and without the risk of the springs and/or the slider coming out of their seats. 
     A second important advantage is the robustness of the telescopic extension in any operating condition and its reliability over time. In fact, the slider  7  is situated between the sleeve  4  and the tunnel  31  of the outer tube  3 . The tunnel  31  forms part of the outer tube  3  and is advantageously made of metal. The slider  7  may simply be displaced along a guided path: on the one hand, it is guided by the tunnel  31  (in particular by the ceiling  38 , mainly formed by the strips  34 ,  35  and  36 , and by the side walls  37 ) and, on the other hand, it is guided by the central part  46  of the recessed area  45 . The tunnel  31  formed in the outer tube is very strong since the outer tube may be made of metal. Therefore, in any operating condition (for example when the slider is displaced so as to move the cylinder piece  5  out of the recess  23 ), the strips  34 ,  35  and  36  will prevent the slider from moving radically outwards.