Patent Publication Number: US-8534160-B2

Title: Retractable control device for domestic appliance

Description:
This application claims priority under 35 U.S.C. §119(b) to Italian Patent Application No. MI2011A000161, which was filed Feb. 4, 2011, the subject matter of which is incorporated herein by reference. 
     The present invention relates to a retractable control device for household electrical appliances. 
     Devices of the aforesaid type have been used for some time in household electrical appliances: they are used on user interfaces to allow the control of appliance functional elements (such as the electrical resistance heater or microwave generator of an oven, or a gas burner of a cooking hob) while at the same time enabling the appliance to present a pleasant appearance when not in use. For this purpose, a known device of the stated type comprises a pushbutton or knob inserted into an aperture or seat in the interface; this knob is movable therein under the action of a spring or an elastically loaded body such as to assume two working positions, in a first of which it is inserted into its seat in the user interface such that its flat or substantially flat end lies substantially coplanar with the interface, and in the second of which it projects from said aperture. 
     The knob cooperates with a control member of said appliance functional element, which can be a simple shaft rotating about a longitudinal axis thereof, usually coinciding with the central axis through the aperture or seat for the knob (and along which this latter moves), or a complex body defining a so-called push-pull control comprising coupled parts longitudinally movable relative to each other against the action of an elastic element. In both cases this control member is connected to the appliance functional element to enable its activation and operational adjustment by operating the knob. 
     The control member is positioned below the user interface and is at least partly contained in a knob support which can be a cup-shaped member or a tubular body. 
     With particular but non-limiting reference to those control devices with a push-pull member, it can happen that the movable knob is not always centered within the aperture or seat in which it moves and that, when in its second working position (knob extracted), this knob oscillates in planes perpendicular to the longitudinal axis of the seat in which it moves. This causes wear of the material (usually plastic) of the knob and/or of the support for the knob and/or of the parts connected to this latter; this is also because of the spaces present between the constituent parts of the control device and of their constructional tolerances. 
     FR2698459 describes a pushbutton or knob controlling a rotary support shaft, in particular of a heating and air conditioning system of a vehicle on which this knob is mounted and axially slidable against a spring. The knob moves within an aperture or seat of a panel from which it can project into a working position; the drawings show that at the aperture this panel presents a substantially undercut socket-shaped portion in the knob seat. The pushbutton slides within this panel portion, its movement guided by the cooperation between a groove provided on its body, slidable on a shaft fixed to an insulating plate carrying conductive tracks, and a pin carried by a rod positioned on a panel fixed to the shaft. 
     EP797052 describes a knob switch inserted movable within an aperture in a vitreous ceramic plate of a cooking hob. This aperture is surrounded by a protection ring below which a seal ring is present. 
     The seal ring is in contact with the knob even when it emerges from the aperture or seat in the plate to control the appliance heating element. 
     An object of the present invention is to provide a retractable control device for a household electrical appliance in which the knob is centered within its seat and in which the knob oscillations in planes perpendicular to the longitudinal axis of said seat along which the knob moves are possibly limited. 
     Another object is to provide a control device of the stated type which is of reliable use, of low cost and offers to the user a sensation of robustness and considerable attractiveness. 
     These and other objects which will be apparent the expert of the art are attained by a control device in accordance with the accompanying claims. 
    
    
     
       The present invention will be more apparent from the accompanying drawings, which are provided by way of non-limiting example and in which: 
         FIG. 1  is an exploded view of a device according to the invention; 
         FIG. 2  is a cross-section through the device of  FIG. 1  in a first working position; 
         FIG. 3  is a view similar to that of the device of  FIG. 2 , but in a different working position; 
         FIG. 4  is a perspective view of a detail of the device of  FIG. 2 ; 
         FIG. 5  is a section taken on the line  5 - 5  of  FIG. 4 ; 
         FIG. 6  is an enlarged view of the part indicated by A in  FIG. 3 ; 
         FIG. 7  is an exploded perspective view of a first variant of the invention; 
         FIG. 8  is a cross-section through the variant of  FIG. 7 ; and 
         FIG. 9  is an exploded perspective view of another variant of the invention. 
     
    
    
     With reference to said figures, a control device comprises a knob  1  associated with a push-pull control member  2  of known type comprising two elements  3  and  4  slidingly movable one on the other against a spring  5 . A (movable) first element  3  of this member  2  presents a free end  3 A inserted into a preferably cylindrical seat  7  provided in the interior of the knob  1  and coupled thereto in that manner. 
     The knob  1  presents a cup-shaped body  10  having a substantially flat first end part  11  from which a perimetral cylindrical wall  12  projects. The knob is to be disposed in an aperture or seat  15  of a user plate or interface  16  of a household electrical appliance, for example an oven. 
     This plate has a face or surface  16 A facing the user and a face or surface  16 B facing the appliance interior. 
     On this latter face  16 B a cylindrical body  17  is present acting as a support for the knob and for the control member  2 , said body  17  being connected to an electronic selector  18  of known type (visible in  FIGS. 7-9 ) cooperating with said member in known manner and hence not described. 
     The knob  1  can assume two working positions, in a first position it being inserted in its seat  15  (and partially in the body  17 ) with its end  11  substantially coplanar with the face  16 A ( FIG. 2 ); in a second position the knob projects from the seat  15  beyond the face  16 A ( FIG. 3 ) to enable a user to act on the member  2  and activate a function of the appliance by rotating the knob about a longitudinal axis (coinciding with the axis W of the seat  15  and of the body  17 ) and activating the selector  18 . 
     According to the invention, a cylindrical centering element  20  is positioned in the aperture or seat  15  of the user interface  16 , between the latter and the knob  1 , and is of dimensions sufficient to contain the knob  1  when this is in its first working position. The element  20  maintains the knob  1  in its first working position, with its axis coinciding with the central longitudinal axis W through the seat  15 , to centre it within this latter; this cylindrical centering element  20  also prevents the knob from “oscillating” in planes perpendicular to the axis W when in its second working position. 
     More particularly, the cylindrical centering element  20  presents a tubular body  22  having a lateral wall  23  presenting an inner face  23 A and an outer face  23 B; the wall  23  comprises elastically deformable lugs  23 K at least one of which presents perpendicularly projecting ends  23 W, preferably of triangular section, to enable the tubular body  22  to be inserted into the seat  15  and be coupled to the interface  16 , to hence be locked in this latter by the engagement between said ends  23 W and the surface  16 B of said interface. The tubular body  22  also presents a flanged first end  24  to rest on the surface  16 A of the interface  16 , and a second end  25  to be inserted into the cylindrical body  17 . 
     In a first embodiment, shown in  FIGS. 1-6 , said cylindrical centering element  20  internally presents a cylindrical portion  26  coaxial to the tubular body  22  and connected thereto via an annular part  30  fixed to the end  25  of said body  22 . This part is flared towards the axis W and hence comprises a portion of inclined surface  32  facing said axis. 
     The cylindrical portion  26  is similar in length to the tubular body  22  and defines therewith an annular interspace  33  to receive the perimetral wall  12  of the body  10  of the knob  1  when this latter is in its first working position, and to guide the movement of the knob from said position to the second working position (arrows K of  FIG. 3 ), or vice versa. 
     By cooperation between the perimetral wall  12  and the face  23 A of the wall  23  of the tubular body  22 , said movement (and the opposite movement) takes place in a guided manner to maintain the knob coaxially with the axis W of the seat  15  and maintain it centered in its seat  15  (and in the body  17 ). 
     In addition, the knob body  10  comprises a cylindrical or conical inner collar  37 , positioned along the wall  12  of this body. In said movement, said collar cooperates with the cylindrical portion  26  to hence improve the centering effect of the cylindrical element  20  on the knob. 
     Advantageously, said cylindrical portion presents two recesses  38  in proximity to its free end  39 , to define two opposing lugs  40  in said portion  26 ; these lugs are flexible and by cooperating with the aforesaid inner collar  37  and/or with the cylindrical perimetral part  12 , increase the centering effect on the knob  1  when in its second working position. 
     To prevent knob oscillation in a plane perpendicular to the axis W when in its second working position, the movable element  3  of the control member  2  or the cylindrical inner collar  37  presents a flanged end portion  41  which is flared inwards, i.e. it presents an inclined annular part  42 . This inclination is equal to that of the portion  32  of the annular part  30  of the element  20  to hence enable the portion  41  to engage that part and element when the knob  1  is extracted from the seat  15 . This means that by virtue of the contact between the portion  41  and the portion  32  any oscillation of the knob about the axis W is prevented because of the force exerted by the spring  5  which maintains the two portions in mutual contact. 
       FIGS. 7 and 8 , in which parts corresponding to those already described are indicated by the same reference numerals, show a first variant of the invention. In this latter, as in the preceding embodiment, the control member  2  comprises the two elements  3  and  4  movable relative to each other. The element  3  comprises, in proximity to its end  3 A, a collar  50  supporting a body  51  which is substantially cup-shaped, but has an end portion  52  provided with a hole  53  enabling the end  3 A of said element  3  to pass, for its insertion into the seat  7  of the knob  1 . 
     This end portion is arranged to rest on the collar  50 ; peripherally projecting downwards (i.e. towards the underlying  2  and parallel to it) from this portion which is of substantially circular-based frusto-conical shape, there are lugs  55  distributed radially and terminating with feet  56  projecting perpendicularly from said lugs to elastically cooperate by interference with the inner face  23 A of the cylindrical centering element  20  which, in the embodiment under examination, lacks the cylindrical portion  26  of  FIGS. 1-6 . The perimetral wall  12  of the knob  1  also directly cooperates with this inner face  23 A (of diameter less than that of a circumference in which the ends of the lugs  55  lie). 
     By virtue of this embodiment, centering of the knob  15  on the axis W of the seat  15  is achieved by cooperation between the lugs  55  and the wall  23  of the cylindrical element  20 . As these are elastically movable relative to the portion  52  of the cup-shaped body  51  and as their free ends (i.e. those of the feet  56 ) lie on a circumference of diameter greater than that of the lateral wall  23  of the element  20 , the lugs  55  press against the wall  23  to block any oscillation of the pushbutton or knob  1  in planes perpendicular to said axis w. 
     In  FIG. 9 , in which parts corresponding to those of the already described figures are indicated by the same reference numerals, the centering element  20  is shaped similar to that of  FIGS. 7 and 8 ; compared with the already described embodiments, the elements  3  and  4  of the control member  2  lack any part or body arranged to cooperate with the centering element  20  to maintain the knob  1  along the axis W and to prevent its oscillation about this latter. This result is achieved by a particular shaping of the knob  1  which has a second end part  70 , defined by the free end of the perimetral wall  12 , from which a plurality of lugs  71  project with an enlarged end part  72  arranged to cooperate with the inner face  23 A of the lateral wall  23  of the centering element  20 . 
     Each lug can be deformed elastically relative to the wall  12 , and has the free surface of the enlarged part lying on a circumference having a larger diameter than the lateral wall  23  of the element  20 . By virtue of this, the lugs  71  elastically press with interference against said face  23 A, the element  20  hence maintaining the knob  1  centered on the axis W and preventing it from undergoing oscillation about this latter. 
     The described embodiments are of simple implementation and of low cost in that they require no intervention on the interface  16  for the purpose of modifying its shape at the aperture or seat  15 . Moreover they can also be used in already existing and operating household electrical appliances by replacing components and inserting elements defining the invention. 
     Some embodiments of the invention have been described. Others are however possible in the light of the aforegoing description and are to be considered as falling within the scope of the ensuing claims.