Abstract:
A rotary knob for an electrical system includes a body containing a rotary maneuvering member which actuates a cam-driving part and bears one or more electrical units. A cup is defined between an outer cylindrical flange of the body and an inner cylindrical sleeve, and contains a spring either of a helical type for urging a sliding ring separate from the driving part, or of a torsion type to return the maneuvering member. The ring provides a sensitivity function. The cylindrical sleeve defines in a central opening thereof a centering seat of the shank of the maneuvering member.

Description:
BACKGROUND OF THE INVENTION 
     I. Field of the Invention 
     The present invention relates to a rotary knob for an electrical system, comprising a body on which can be mounted a rotary maneuvering member, in particular a hand grip or a rotor controlled by a key, and of housing a driving part for switching contacts. 
     II. Description of Related Art 
     In conventional rotary knobs, the maneuvering member is provided with a shank for moving the driving part, and the body also serves as a support for at least one electrical contact block, switchable in response to the rotation of the maneuvering member via at least one axially moving slider. The maneuvering member is mounted on the body such that it rotates about an axis with a limited angular movement, in order to assume at least two functional positions, maintained or transitory. Rotary knobs of this type are well known (see for example the documents DE 34 12 518 and DE 35 41 390). The maneuvering member is locked in rotation with a driving part having a cam able to actuate the slider or sliders and the body is able to receive the hand grip in a fluid-tight manner, to serve as a support for the electrical blocks and to house the driving part and the sliders. 
     These knobs sometimes have the disadvantage that, although the maneuvering member is placed in one of its functional positions, a slight force applied to that member can suffice to make a notch of the cam jump and to drive the knob in an inopportune manner. 
     BRIEF SUMMARY OF THE INVENTION 
     The purpose of the invention, in a rotary knob of the type described, is to overcome the disadvantages of the prior art by proposing a knob providing satisfactory guidance of the rotary part using means conferring the knob with minimal dimensions, in particular height, and facilitating assembly. 
     Another purpose of the invention is to propose means making it possible to improve the fluid-tightness of such knobs. 
     According to the invention, the body of the knob has a recessed part provided with an external cylindrical flange, an internal cylindrical sleeve, and a cup defined between the flange and the sleeve for housing a helical spring acting on a sensitivity ring separate from the driving part and movable in translation or, respectively, a torsion spring acting on the maneuvering member, and the cylindrical sleeve defines a central opening with which a centering seat of the shank of the maneuvering member cooperates. The arrangement resulting form this provides the sought sensitivity whilst maintaining small dimensions. 
     In order to achieve an excellent centering at the level of the sleeve, the shank of the maneuvering member and the driving part can each have a cylindrical seat ensuring the centering, in the central opening of the sleeve, of the rotary equipment consisting of the maneuvering member and the driving part. 
     In order to facilitate the assembly of the knob, the driving part can be mounted by means of interlocking shapes on the shank of the maneuvering member and provide a shoulder connected to its seat for being applied axially against a bearing face of the body. 
     When the spring is a compression spring, the cup preferably also houses the sensitivity ring, and the ring:
         is separate from the driving part, and is coaxial with the maneuvering member and movable in translation,   has a diametral size corresponding to that of the cup, and   cooperates with the maneuvering member by means of cam shapes provided on their respective peripheries and provided with notches corresponding to the functional positions of the knob.       

     The rotary equipment, formed by the shank of the maneuvering member and the driving part, can carry a lip seal of small diameter which cooperates in rotation with the central opening of the cylindrical sleeve substantially at the level of the cup. 
     Between the external cylindrical flange of the body and the cup, it is possible to provide an annular space, stepped with respect to the cup, able to house a sealing device. 
     According to a first variant embodiment, the sealing device comprises a guard ring intended to retain the sensitivity ring and housed in the stepped annular space of the body. The head of the hand grip can be provided with a reentrant annular rim which is housed in the staged annular space of the body. Thus the annular rim of the hand grip and the guard ring define between them a first radial annular interstice between the flange and the annular rim and a second radial annular interstice between the annular rim and the cylindrical skirt, the two interstices in series forming a sealing chicane. The guard ring contributes to forming a barrier against the introduction of dust, polluting elements or projections inside the body of the rotary knob, and the two interstices together avoid, in normal conditions of use, having to make use of a sealing gasket of large diameter. 
     According to a second variant embodiment, the sealing device can be constituted by a conventional lip seal provided in the stepped annular space. 
     For purposes of compactness, the compression spring housed in the cup can advantageously have a height of substantially the same order as the height of the cylindrical sleeve. 
     When the spring is a torsion spring, a chicane sealing device can be provided between the cylindrical flange of the body and can comprise a skirt of the grasping head and an intermediate cylindrical flange of the body separating the cup from the annular space. The torsion spring and the intermediate flange advantageously have a height substantially of the same order as the height of the cylindrical sleeve. 
     The following detailed description, referring to the appended drawings, illustrates an embodiment given by way of example. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagrammatic representation in perspective of a rotary knob according to the invention, with its contact blocks. 
         FIG. 2  is an exploded view of a rotary knob with maintained positions. 
         FIG. 3  is a diagrammatic plan view of a rotary knob with maintained or transitory positions according to the invention. 
         FIGS. 4A to 4C  are longitudinal axial cross sectional views, through  4 A- 4 A,  4 B- 4 B,  4 C- 4 C,  4 D- 4 D respectively of  FIG. 3 , of the rotary knob with maintained positions shown in  FIG. 2 . 
         FIG. 5  is a perspective view of the sensitivity ring used in the rotary knob with positions shown in  FIG. 2 . 
         FIG. 6  is a bottom view of the hand grip of the rotary knob according to the invention. 
         FIG. 7  is an exploded view of so-called return knob. 
         FIG. 8  is a longitudinal axial cross-sectional view of the rotary return knob shown in  FIG. 7 , through  4 B′- 4 B′ of  FIG. 3 . 
         FIG. 9  is a diagrammatic axial cross-sectional view of a variant embodiment of the knob with maintained positions. 
         FIG. 10  is an exploded view of component parts of the knob shown in  FIG. 9 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The rotary knob  1 ,  1 ′ shown in the figures comprises a body  10  which carries a maneuvering member  20  which rotates about an axis X. In the present example, the member  20  is a hand grip, but it can also be a cylinder operated by a key. The body  10  of the knob is designed to be fixed in an opening formed in a panel or a wall P, for example by means of a normal fixing base S. Electric contact blocks C are integral with the body or the base in order to be switched according to the position given to the hand grip  20 . The hand grip  20  is mounted such that it rotates in the body with a limited angular movement, in order to assume at least two functional positions, maintained or transitory. 
     The body  10  of the knob has a recessed top part  10   a  and a narrower bottom driving part  10   b . The bottom part  10   b  of the body comprises straight shapes for guiding sliders  11  which move in translation, in response to the rotation of the hand grip and under the action of a drive part  50  rotationally coupled to the hand grip. The sliders  11  move in a direction parallel with the axis X in order to become applied on push rods that are part of the blocks C. The push rods are pushed back against the sliders  11  by individual springs. 
     The hand grip  20  comprises in its grasping head  21 , embedded in the latter, an indicator  60 , whose function is to mark the angular position of the hand grip. This indicator  60  is for example interlocked in a slot formed in the grasping head  21 . 
     In the rest of the description, the use of the terms “axial”, “axially”, “coaxial” or “transverse” are defined with respect to said axis X. 
     Similarly the terms “high”, “low”, “upper”, “lower”, above”, “below” or equivalent directional terms must be understood to be with respect to said axis X when the latter is vertical. 
     The recessed part  10   a  of the body is provided with an external cylindrical flange  12  and with an internal cylindrical sleeve  13 , the latter defining a central opening  14 . Moreover, the flange  12  and the sleeve  13  define between them a cup  15  which houses, in a first embodiment of the invention, a helical compression spring R whose axis is X ( FIGS. 2 to 6 ) or, in a second embodiment which will be described later, a torsion spring R′ ( FIGS. 7 and 8 ). 
     In the first embodiment, the body  10  comprises a sliding sensitivity ring  30  translationally acted upon by the compression spring R. The compression spring R is applied on the one hand against the bottom of the cup  15  and on the other hand against the sensitivity ring  30  in order to act upon the latter axially. 
     The hand grip  20  has a grasping head  21  having the shape of a wing formed in an axial plane. The hand grip  20  furthermore comprises a central shank  22  which is connected to the head and extends axially in order to traverse the central opening  14 , the driving part  50  being fixed by interlocking to the shank  22 . 
     The hand grip  20  has a centering seat  23  ( FIG. 6 ) which is applied against the internal face of the sleeve  13  and which has a groove or an annular shoulder in order to receive a lip seal  24  providing good fluid-tightness with the internal face of the sleeve. A groove  29  ( FIGS. 4A to 4D ) provided on the periphery of the grasping head  21  of the hand grip is able to house a sealing device  25  such as a conventional lip seal (see  FIG. 9 ) which is applied against the internal face of the flange  12  of the body. 
     The lip seal is used if a certain total resistance force is tolerated. If it is desired to reduce this total resistant force, the sealing device  25  can be constituted by a chicane provided towards the flange  12 , for example formed by a guard ring  40  ( FIG. 9 ) housed in an annular space  16  concentric with the cup  15 , stepped with respect to the latter. This guard ring can be provided in replacement of said lip seal or in addition to it as shown in  FIG. 9 . 
     The grasping head  21  of the hand grip has on its internal periphery actuating shapes  26  which cooperate with the ring  30 . Finally, the shank  22  of the hand grip has shapes for indexing the driving part  50  (for example square as seen in  FIG. 6 ) and interlocking shapes  27  upon which respective shapes of the part  50  interlock. 
     The sensitivity ring  30  has notches  31  or other similar recessed or relief shapes which allow it to slide axially against two slides  12   a  ( FIG. 4A ) of the body  10  formed in the stepped annular space  16 ; it must be noted that these slides can be also be provided on said guard ring  40 . Furthermore, the ring  30  has shapes  32  provided for cooperating with the actuating shapes  26  of the hand grip. These shapes  32  (see  FIG. 5 ) have slopes  32   a  and notches  32   b  corresponding to the desired functional positions of the knob. 
     The driving part  50  ( FIG. 4B ) has the shape of a tubular part having at its top a centering seat  55  in the opening  14  defined by the sleeve  13  inside the body  10  and at its bottom cam shapes for actuating the sliders  11 . It also has an internal sleeve  51  having a constant square cross-section and in which the shank  22  of the hand grip  20  is inserted. Interlocking shapes  56  are provided on the internal surface of this sleeve  51  for cooperating with corresponding interlocking shapes  27  of the shank  22  of the hand grip. The driving part  50  furthermore comprises an external coaxial cylindrical skirt  53  having a lower rim  52  whose periphery defines the cam shapes. The skirt  53  forms with the centering seat  55  an annular shoulder  54  defining a transverse surface facing the lower rim of the internal sleeve  13  of the body  10 . 
     In the annular space  16  of the body  10  there are two slides  12   a  provided with an engagement recess  12   b  for the guard ring  40  ( FIG. 10 ) when the latter is provided. 
     The guard ring  40  ( FIG. 10 ) has a flange  41  fixed, for example force fitted, against the bottom of the cup  15 , and a cylindrical skirt  42  provided with two diametrically opposite notches  43  which allow the ring  40  to sit on the sliding protrusions  12   a  ( FIG. 10  shows for this purpose in its bottom part a portion of the ring  40  inserted in the body  10 ). At the level of the notches  43 , the skirt  42  has stops  44 , for example in the form of claws or tenons, which therefore retain the ring  30  against the spring R ( FIG. 9 ). 
     The assembly and the operation of the rotary knob  1  according to the invention will be explained for the embodiment having a sensitivity ring. The spring R is placed at the bottom of the cup  15  and the ring  30  is slipped over the protruding slides  12   a . The body/spring/ring  10 ,  30 , R subassembly is then ready to receive the hand grip  20 , added from the top into the body, and then the driving part  50  which is added from the bottom and engaged on the shank  22  of the hand grip and bearing by its shoulder  54  on the lower rim of the sleeve  13 . The centering seats  23 ,  55  of the hand grip  20  and of the part  50 , situated on the two sides of the lip seal  24 , ensure perfect guidance of the rotary equipment  20 ,  50 . 
     When the operator rotates the hand grip  20 , the actuating shapes  26  cooperate with the cam shapes  32  of the ring  30  during the rotation; the pressure then applied on the spring R gives rise to a reaction force felt by the operator. When the hand grip arrives at the desired position, the spring pushes back a notch  32   b  of the ring towards the corresponding shape  26  such that the position remains maintained, and the axial movement of the ring remains limited by the hand grip  20  ( FIG. 4B ). The fluid-tightness of the interior of the knob is guaranteed by the lip seal  24  and possibly, if it is present, by the sealing device  25 . The seal  24  is of small diameter and therefore gives rise to minimal resisting force. 
     In the second embodiment of the invention, the rotary knob  1 ′ is called a return knob and uses a torsion spring R′ in replacement of the compression spring R. The latter is fixed on the one hand to the bottom of the cup  15  and on the other hand to the hand grip  20  in order to return the latter in a rotary manner. 
     In this embodiment, shown in  FIGS. 7 and 8 , the body has an intermediate internal flange  17  separating the cup  15  from the previously defined annular space  16 . The hand grip  20  has a reentrant skirt  28  in the annular space  16 . The presence of the sleeve  13  and of the intermediate flange surrounding the spring R′, combined with the presence of the reentrant skirt  28  of the hand grip, produce the sought fluid-tightness. The other features of the rotary return knob  1 ′ are identical to those of the rotary knob  1  with positions.