Abstract:
A switch for controlling a control circuit or an operating current of electric-motors in linear gear drives includes: a switch casing, having at least an upper part including keys, and a lower part for forming a receiving space; a circuit board incorporated in the receiving space with micro-switches including a switch casing and a spring-biased push-rod therein; wherein, when the keys are actuated by a user, the push rod actuates the micro-switch to control a control circuit or operating current, and wherein the switch contains at least one locking element, transferable between a locking position, which locks the keys, and a release position, which releases the keys. To prevent damage to a switch from pressure forces during actuation, the locking device is formed such that the pressure applied to the key is transferred onto the switch casing and/or the circuit board plate over as wide an area as possible.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a Section 371 of International Application No. PCT/EP2012/070069, filed Oct. 10, 2012, which was published in the German language on Apr. 18, 2013, under International Publication No. WO 2013/053764 A1 and the disclosure of which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The invention concerns a switch for controlling a control current for the control of an operating current of electric motors in linear transmissions, for example for the actuation of sick-beds, tables or the like. Such switches comprise a switch housing having at upper part including buttons and a lower part for forming a receiving space. Received in the receiving space is a circuit board having microswitches which have a switch housing and a spring-biased pushrod therein. Upon actuation of the buttons by a user the elastic or resilient button is depressed on to the pushrod of the microswitch and thus actuates the microswitch for controlling the control current. In addition such a hand switch has at least one locking device which can be displaced by the user from a locking position of locking the button into a release position of releasing the buttons. 
         [0003]    Such switches which are in the form of hand switches are known for example from EP 0 480 221 B1 and WO 2005/036576. Both specifications are concerned with the problems of mechanical locking devices for the buttons in a hand control or a hand switch. Those hand switches include one or more buttons in an upper part which is connected to a lower part. Provided between the upper part and the lower part is a receiving space in which there is arranged a circuit board on which microswitches are fixed. Those microswitches have a spring-biased button arrangement which is depressed upon actuation of the buttons of the upper casing part and thus controls the control current for actuation of the operating current for the electrically operated drive or drives. Usually the two respective buttons are arranged in juxtaposed paired relationship in order to respectively permit the two opposite modes of operation for a respective electric motor. 
         [0004]    The proposed solutions propose locking devices which are rotatable about a central axis and which can be rotated from the release position into the locking position. In the locking position the locking devices block the buttons to prevent them from being depressed in the upper part on to the pushrods of the microswitches. They therefore bear in contact between the underside of the elastic buttons and the upper part of the housing of the microswitch in such a way that it is not possible for the buttons to be pressed down on to the pushrod of the microswitch. In the rotated release position the two laterally projecting locking arms of the locking device free that arresting action and allow the buttons to be pressed down on to the microswitches. 
         [0005]    EP 0 480 221 B1 operates with pneumatic switches, but with a similar principle with a rotatable locking device which in the locking position prevents the buttons from being pressed down by engagement at one side into the opening. That has the disadvantage that the one-sided displacement can cause tilting of the buttons. WO 2005/036576 discloses a further configuration of a mechanical locking arrangement. 
         [0006]    Those mechanical locking arrangements transmit the locking forces to the microswitch and to the circuit board on which the microswitch is soldered. In ongoing operation that can result in destruction of the microswitch and/or the solder joints, and that then results in a system fault. 
       BRIEF SUMMARY OF THE INVENTION 
       [0007]    The object of the invention is to further develop a hand switch of the general kind set forth in such a way that the disadvantages of the state of the art are at least partially avoided and in particular destruction of the solder joints of the circuit board and system components by excessively heavy loadings on the buttons is prevented. 
         [0008]    That object is already attained in that the locking element is adapted to transmit the pressure applied to the button to the switch housing and/or the circuit board over as large an area as possible. That is effected by way of an arm which can be introduced under the button or buttons and which in that position either locks the button to prevent it from being depressed (locking arm) or which by introduction first bridges over an intermediate space between the underside of the button and the top side of the pushrod so that it is only after introduction that a pressure on the button can cause actuation of the microswitch (bridging arm). Preferably the bridging arm is of an elastic nature. 
         [0009]    In a first preferred embodiment the locking device has a longitudinally displaceable locking element which is adapted to be transferred from a lowered release position into a lifted locking position, when a translatory movement is performed. In the lowered release position therefore it is possible for the buttons to be pressed down on to the pushrod of the microswitches. Upon displacement into the locking position, the locking element—also referred to as the locking slider—performs such a vertical movement that the locking element either bears against the housing or the switch housing or both and thus prevents the buttons from being depressed, but at the same time it also transmits the pressure forces at least for the major part to the switch housing and not to the delicate system components. 
         [0010]    Preferably the means for performing the heightwise displacement of the locking element include inclined run-on ramps which are operative in pairs in mutually opposite and complementary relationship and which in the course of the translatory movement slide against each other, with a displacement in respect of height. 
         [0011]    It is also possible that the locking element surrounds the circuit board on the outside, that is to say it bears on the housing lower part, and only a horizontally extending locking or bridging arm extends at least portion-wise over the circuit board, but does not necessarily have to be in contact therewith. Another solution provides that the locking device is adapted to transmit the pressure forces to the circuit board over the complete surface area thereof. Preferably in that respect the housing has a housing portion at which the circuit board is supported over a surface area so that no delicate system components carry the pressure forces. 
         [0012]    In the displaceable structures discussed above the locking element performs a translatory movement which is sometimes converted into a lifting/lowering movement. In a basically different solution the locking element is in the form of a rotary element which performs a rotary movement about an axis of rotation. Preferably the locking element, with its axis of rotation extending in a longitudinal direction, extends vertically in the switch housing. As in that embodiment the locking element generally extends transversely relative to the longitudinal axis of the circuit board it can thus also extend through an opening in the circuit board for the transmission of force to the switch housing and to avoid loadings on the circuit board. That structure therefore has the advantage that the pressure forces are transmitted to the housing and/or the circuit board by way of the rotary element, whereby that structure basically requires less structural space than the translatory structures. In addition rotary structures can be sealed off more easily, for example by a simple O-ring. 
         [0013]    The locking element has preferably locking and/or bridging arms which project in diametrically opposite relationship and which can be of such a geometrical configuration as to avoid collision with components disposed in the switch, in the rotary region. Naturally, depending on the respective situation of use and the geometrical factors in the switch, the arms can also be arranged differently relative to each other. 
         [0014]    In another preferred embodiment the lockable switch is fitted into a side portion of a bed. The mechanical locking device for the buttons is very universal and can be easily adapted to different types of microswitches. In that respect it is possible to use different configurations of microswitches in the switch. A first structure of microswitches is of a small structural height and switches a control circuit for the actuation of a load relay which switches the respective operating current of the electric motors. The advantage of the mechanical locking device is that it can be adapted to the flat microswitches so that a hand switch for a bed or for a chair can also be of a very flat and shallow configuration. Another form of microswitches has other switching contacts which directly switch the operating current of the electric motors. The advantage in that respect lies in the simple structure and ease with which they can be assembled. 
         [0015]    Preferably the proposed switch is made from plastic, in particular ABS or polyamide or combinations thereof. 
         [0016]    What is essential in all proposed solutions is that the locking element is adapted, in the locking position, to transmit the pressure force exerted on the button or buttons over as large a surface area as possible, in particular preferably to the housing or to the circuit board and the housing. It can also be transmitted at least partially to the switch housing of the microswitches, to the circuit board and to the housing. Force transmission over a large surface area is crucial, to avoid stress peaks. 
         [0017]    The proposed lockable switch is preferably in the form of a hand switch which for example can be connected to the linear transmission by way of a cable, but it can equally well be in the form of a chair switch which for example is integrated in the armrest or backrest of a chair. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0018]    The foregoing summary, as well as the following detailed description of the invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there are shown in the drawings embodiments which are presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. 
           [0019]    Further details, advantages and features of the invention will be apparent from the specific description hereinafter in which preferred embodiments of the invention are set forth and described in fuller detail. In the drawing: 
           [0020]      FIG. 1A  shows a perspective view of a first embodiment of the mechanical locking switch in the form of a hand switch for a chair; 
           [0021]      FIG. 1B  shows an enlarged longitudinal section of the region of the buttons of the hand switch shown in  FIG. 1A  in the release position; 
           [0022]      FIG. 1C  shows an enlarged longitudinal section of the buttons of the hand switch shown in  FIG. 1A  in the locking position; 
           [0023]      FIG. 2A  shows a perspective view of a locking switch in the form of a chair switch for incorporation in an armchair; 
           [0024]      FIG. 2B  shows a longitudinal section through the locking switch of  FIG. 2A ; 
           [0025]      FIG. 2C  shows a cross-section through the locking switch of  FIG. 2A ; 
           [0026]      FIG. 2D  shows a first perspective view of the lifting device of the switch of  FIG. 2A ; 
           [0027]      FIG. 2E  shows a second perspective view of the lifting device of the switch of  FIG. 2A ; 
           [0028]      FIGS. 3A-8B  show longitudinal sections which are respectively enlarged in pairs of various embodiments of the locking switch, wherein in each case Figure A denotes the switch in the release position and Figure B denotes the switch in the locking position; 
           [0029]      FIG. 8A  shows a sectional view of a locking device in the form of a rotary locking member and a locking device in the form of a rotary transmission member, fitted in a hand switch; 
           [0030]      FIG. 8B  shows an enlarged sectional view of the rotary member of  FIG. 8A  in the locking position; 
           [0031]      FIG. 8C  shows an enlarged sectional view of the rotary member of  FIG. 8A  in the release position; 
           [0032]      FIG. 9A  shows a perspective view of parts of another chair hand switch as shown in  FIGS. 2A to 2E  in the release position; 
           [0033]      FIG. 9B  shows a perspective view of the parts of another chair hand switch as shown in  FIG. 9A  in the locking position; and 
           [0034]      FIG. 9C  shows a perspective view of the parts of another chair hand switch as shown in  FIG. 9A  as an exploded view. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0035]    Identical parts or parts having the same action are denoted by the same references. 
         [0036]    Accordingly the hand switch  2  shown as a perspective view in  FIG. 1A  comprises an elongate switch housing formed by an upper part  4  and a lower part  6  which are each in the form of a half-shell portion and the edges of which are joined together at the joint locations, enclosing a receiving space, preferably being connected releasably for repair purposes. The geometrical configuration of the hand switch is not relevant in the present case and here only represents a preferred embodiment. 
         [0037]    The hand switch  2  comprises two buttons  8 ,  10  which respectively form a pair and which are intended to control an electric motor of a linear transmission for the chair in the one direction and in the opposite direction. Signal transmission from the hand switch to the electric motor is effected either by way of a cable (not shown) connected to the hand switch  2 , or by way of wireless transmission. 
         [0038]    The actuating end  12  of a locking slider received within the hand switch for locking the buttons  8 ,  10  projects through a rectangular opening in the upper part  4  above the pair of buttons in such a way that actuation is possible by insertion of a pointed article, for example a pen or pencil, into a pressing-in opening at the top side of the actuating end  12 . 
         [0039]      FIGS. 1B and 1C  show an enlarged longitudinal section through the hand switch  2  in the region of the buttons  8 ,  10 . In accordance therewith the lower part  6  includes a plurality of mutually spaced vertical legs, on which a circuit board  16  is fixed by fixing screws (not shown) or after assembly of the housing parts  4 ,  6 . Arranged on the circuit board  16 , besides the required circuits and electrical components, there are in particular two microswitches  18  which are arranged in corresponding relationship with the buttons and of which in the present case only the microswitch  18  associated with the button  8  is visible here. Each microswitch comprises a switch housing, from the top side of which a spring-biased pushrod  20  projects. The pushrod  20  is arranged in the installation position beneath a downwardly projecting vertical leg of the button  8 . The button  8  is in the form of a plastic element which is in the shape of a cover and which has a peripherally extending flange which in the installation position embraces the edge of a through opening for the buttons  8 ,  10  in the upper part  4 . 
         [0040]    In the release position shown in  FIG. 1B  the buttons  8 ,  10  can be pressed down whereby the pressure can be transmitted to the pushrod  20  of the microswitch  18  for actuation thereof. The locking slider  14  is in the form of a one-piece injection moulding having a lower horizontal leg which defines a horizontal plane and which in the installation position bears over a surface area against the circuit board to distribute the pressure there, together with three legs which extend transversely relative to the plane of the horizontal leg, namely an actuating leg  15  provided at a first end, and two locking legs  22 ,  24  which are spaced relative to each other by the outside diameter of the buttons  8 ,  10 , at the opposite end of the slider. By actuation of the actuating leg  15 , the locking slider  14  which is movable with a translatory movement is movable from the release position shown in  FIG. 1B  in which the locking legs  22 ,  24  allow the buttons  8 ,  10  to be pressed down, into the locking position shown in  FIG. 1C  in which the locking legs  22 ,  24  are disposed at both sides beneath the rim of the buttons  8 ,  10  and thus prevent the buttons  8 ,  10  from being depressed and thus the pressure force applied is transmitted over a surface area to the circuit board  16  and from same by way of the vertical legs to the switch housing  2 . 
         [0041]    The second embodiment of the locking switch, shown in  FIG. 2 , is in the form of a chair switch for fitment in the armrest of a chair. This embodiment comprises a circular-cylindrical switch housing having a housing lower part  26  and a housing upper part  27  which can be fitted thereon in the form of a cap, the lower and upper parts  26  and  27  being in the form of one-piece plastic portions, of which the housing upper part  27  has a peripherally extending fixing flange  28  which in the installation position, after fitment of the switch housing into a suitable receiving opening of a chair, bears against it at the edge thereof, and can be covered by a cover ring  29  which can be fitted in position thereon by snapping engagement. Thus only the actuating end of the chair switch with the two buttons  30 ,  32  which are of a semicircular shape is visible, wherein a spacer leg  34  of the housing upper part  27  extends between the two buttons  30 ,  32 . Provided centrally in the spacer leg  34  is a rectangular opening, through which the actuating leg  36  of a locking slider  38  projects. 
         [0042]    This locking slider  38  which is in the form of a lifting device comprises the plates which are shown in perspective views in  FIGS. 2D and 2E , wherein the view in  FIG. 2D  is a view of those plates from below and  FIG. 2E  is a view of the two plates from above. The locking slider  38  is thus formed by a lower plate  102  which is arranged downwardly in the installation position and a lift plate  104  which is of a complementary configuration thereto and which in the position of installation on the lower plate  102  has a central opening through which the actuating leg  36  of the lower plate  102  projects. At their peripheral edges, the plates  102 ,  104  which are substantially in the form of circular discs have a plurality of semicircular recesses for fixing them in position in the switch housing. Provided between the plates  102 ,  104  are lifting means which transform translation of the lower plate  102  into a lifting movement of the upper plate  104  in relation to the stationary lower plate  102 . In the present case those lifting means include a plurality of depressions  106  which are formed in the lower plate  102  and which respectively have, at the left-hand sides in the Figure, a plurality of inclined run-on surface portions  103  with an angle of 45° relative to the horizontal, in respect of the depressions  106 . In the present embodiment, a total of seven ramp projections  110  are integrally formed at the underside of the lift plate  104 , which ramp projections  110  can be of differing widths and which in the installation position correspond with the depressions  106  and lower inclined run-on surface portions  108  in the lower plate  102 , that is to say at the side on the left in the Figure, they have upper inclined run-on surface portions  112  which in the installation position act in complementary relationship with the lower inclined run-on surface portions  108  so that, in a translatory movement of the lower plate  102 , they cause lifting of the lift plate  104  into the locking position, by virtue of the complementary inclined run-on surface portions  108 ,  112  sliding against each other. 
         [0043]    The locking slider  38  further includes a latching arm  44  which extends in the longitudinal direction and which either engages in latching relationship into a corresponding release opening in the underside of the spacer leg  34  in the release position shown in  FIG. 2B , or into a locking opening spaced from the release opening, for fixing in the locking position, in the underside of the spacer leg  34 . 
         [0044]    As shown in  FIG. 2C  the spacer leg  34  is of a U-shaped configuration, the opening facing downwardly in the illustrated view. In a manner not shown in greater detail, and in accordance with another embodiment of the locking slider which is also not shown in greater detail, the locking slider has, in portions thereof, shaped-out portions or shaped-in portions which correspond with shaped-in portions, shaped-out portions or with recesses or with spring legs of the limbs of the U-shaped spacer leg, in such a way that they are of an elastically yielding nature and are thus in the form of a latching means which can be overcome. When the locking slider is moved from the one end position into the other end position, that resistance formed by the latching means is overcome and the locking slider is simultaneously held in the respective end position. 
         [0045]    In a further embodiment (also not shown) the ramp projections are shaped on or fitted to the buttons. In this embodiment there is no upper plate, this considerably simplifying assembly of the locking switch. In other words, a part of the lifting device is thus integrated into the buttons. In this embodiment the ramp projections fitted to the buttons also have corresponding inclined run-on surface portions, wherein the gradient of those inclined surface portions defines the resistance to be overcome. 
         [0046]    In addition, fitted in recessed relationship in the spacer leg  34  is a control diode  46  with which the actuating direction and/or actuation of the buttons  30 ,  32  can be indicated by colour coding. The diode  46  is connected like the microswitches  40 ,  42  to a circuit board  48  fixed in an accurate position on the upper end of the housing lower part  26 . In this embodiment of  FIG. 2  also, the switch housing thus comprises the lower switch housing  26  which has the function of the lower half-shell portion for carrying the circuit board  48  in accordance with the embodiment of  FIG. 1 , and a housing upper part  27  which together with the housing lower part  26  forms the receiving space for the circuit board  48  and the electrical components. The lower housing part  26  and the upper housing part  27  are releasably fixed together with screws in the peripheral flange. 
         [0047]      FIGS. 3 to 7  show various embodiments of the locking devices according to the invention in the form of longitudinal sections on an enlarged scale, fitted in a hand switch as shown in  FIG. 1A . These Figures, besides the locking device, for the purposes of better clarity, only show the essential components, that is to say the housing upper shell portion  4 , the button, the circuit board  16  and the microswitch  18 , in order to clearly show the different configurations of the locking slider. 
         [0048]    In the embodiment shown in  FIG. 3  the button  50  has a slot-shaped recess  52  at one side. The horizontal portion  57  of the locking slider  54 , which is received displaceably in the upper half-shell portion  4  of the switch housing  4 , can be inserted in the recess  52 , for locking purposes. In  FIG. 3A  that locking slider  54  is in the release position at the left in the Figure. In the locking position shown in  FIG. 3B  in contrast the locking slider  54  is displaced out of the left position shown in  FIG. 3A  into the right locking position so that the free end of the horizontal portion  51  of the locking slider  54  engages into the one-sided recess  52  in the button  50 . The pressing force is thus transmitted by way of the button  50  and the locking slider  54  to the upper half-shell portion  56  of the switch housing to avoid loading the electrical components within the switch housing. 
         [0049]    In the embodiment shown in  FIG. 4  a button which is L-shaped in cross-section is integrally formed on the upper half-shell portion  56  of the switch housing and joined thereto by means of a film hinge  58 . A horizontal leg  60  of that button, which is an upper leg in the installation position, forms the actual button region and a vertical leg  62  which extends vertically downwardly from the horizontal leg  60  at the free end projects as far as a certain spacing above the circuit board  16 . In this embodiment also the locking slider  64  is arranged on the circuit board  16  movably with a translatory movement, that is to say longitudinally displaceably, between the locking and release positions, and at its rear free end which is at the right, it has a thickened portion  66  which bridges over the spacing between the lower end of the vertical leg  62  and the surface of the circuit board  16  in the locking position, in order to lock the button  60  against being depressed. At the same time the pressure force is transmitted from the button  60  by way of the locking slider  64  over a surface area to the circuit board  16  and the lower half-shell portion (this is not shown). 
         [0050]      FIG. 5  shows various views of a locking device which is in the form of a rotary element and which is referred to hereinafter as a ‘rotary locking member’. That rotary locking member  68  basically comprises two elements which are received in the switch housing, namely a central rotatable axis member  70  and a locking arm  72  arranged non-rotatably on the axis member  70 . In the installation position the axis member  70  is received extending vertically in the switch housing and is rotatable through an upper opening with a corresponding key or wrench. The axis member  70  which is shown as a separate part in  FIG. 5C  is in the form of a general cylinder  74  on which a cylindrical enlargement portion  76  is formed at the upper end, approximately however at the centre. A peripherally extending sloped groove  78  is formed in the outer peripheral surface of the enlargement portion  76 . The locking arm  72  shown as a perspective view in  FIG. 5D  includes a ring  80  having an internal recess in which the cylinder  74  of the axis member  70  can be fitted. Formed in a cylindrically enlarged upper region of the ring  80  are inwardly projecting, mutually diametrally opposite projections  72  which in the installation position engage into the sloped groove  78  in the axis member  70 . By virtue of a rotary movement of the axis member  70  the projections  82  are guided in the sloped groove  78  so that the locking arm  72  is moved from the release position of being lowered, as shown in  FIG. 5A , into the lifted locking position shown in  FIG. 5B  and in which arms  84  formed integrally at one side at the outer peripheral surface of the ring  80  are disposed beneath the button  86  and lock the button  86  to prevent it from being pressed down. The rotary locking member  68  is sealed with respect to the housing by way of an O-ring  69 . 
         [0051]    In a development of the embodiment shown in  FIG. 5  the ring  80  has further arms  84  corresponding to a further button. Thus the rotary locking member  68  is adapted to either lock or release a number of corresponding buttons  86 , preferably two buttons  86 , for actuation purposes. 
         [0052]    The embodiments of the locking devices, that are shown in  FIGS. 6   a  and  7 , are somewhat different in terms of their operative principle, from the above-described embodiments. In these embodiments more specifically the slider is used not for locking purposes but for the transmission of the pressure force from the button  86  to the pushrod of the microswitch  18 . In both embodiments therefore the locking device is not in the form of a locking slider but in the form of a transmission slider for transmitting the pressure force of the button  86  in the release position. The release slider again has a horizontal plate  88  which in the installation position is disposed on the circuit board  16  and which in this embodiment additionally has a central opening around the microswitch  18 . A vertical leg  92  which in the installation position extends inclinedly relative to the horizontal plate  88  is equipped with spring arms  94 ,  96  which are of different configurations and which project relative to the microswitch  18  and which in the release position shown in Figure A in respect of  FIGS. 7 and 8  are disposed with an enlarged portion between the underside of the button  86  and the top side of the pushrod  20  of the microswitch  18 , and thus transmit the pressure force from the button  86  to the pushrod  20  for actuation thereof, and a locking position which is respectively shown in Figure B in  FIGS. 7 and 8  and in which the spring arms  94 ,  96  clear the space between the underside of the button  86  and the top side of the pushrod  20  so that depression of the button  86  admittedly causes deflection of the spring arms  94 ,  96 , but not actuation of the pushrods  20  of the microswitches  18 . For that purpose the spring arms  94 ,  96  are integrally formed on the vertical leg of the release slider  19 , by way of spring portions  98  of a wave-shaped configuration. 
         [0053]    For the sake of improved clarity of the drawing the Figures usually show only one microswitch on an enlarged scale. In that respect this involves a simplified view because the microswitches are usually but not necessarily always locked in pairs or in group-wise fashion. 
         [0054]      FIGS. 8A-8C  show enlarged sectional views of a respective locking device in the form of a rotary locking member  114  and a locking device in the form of a rotary transmission member  115 , installed in a hand switch, to clearly show the mode of operation involved, wherein each of the rotary members  114 ,  115  simultaneously either releases or locks two buttons  120  arranged in paired relationship one beside the other.  FIG. 8A  shows the rotary locking member  114  and the rotary transmission member  115  in the locking position. Each of the rotary members  114 ,  115  includes a respective central rotary cylinder, on which sickle-shaped arms  122  are integrally shaped at both sides in diametrally opposite relationship, with the inclusion of an angle of 180 degrees. Those arms  122  are of such a configuration that in the left-hand embodiment, in the form of a rotary locking member  114 , they are disposed in the locking position at both sides beneath the underside of the outside edge of the buttons  120  and support same against the top side of the housings of the microswitches  126 . When they are in the form of rotary transmission members  115  in contrast the arms  122  are of such a configuration that in the locking position they clear the space between the underside of the buttons  120  and the upper end of the pushrods of the microswitches. The buttons  120  arranged in pairs are accordingly simultaneously either locked or simultaneously unlocked after rotation of the rotary locking member  114  or the rotary transmission member  115  in accordance with the view in  FIG. 8B , wherein in that view the arms  122  of the rotary locking member  114  are not arranged between the microswitches  126  and the buttons  120  and the arms of the rotary transmission member  115  are in contrast arranged in that way. For safeguarding displacement, the rotary movement is preferably possible only with a key or wrench which fits to the rotary locking member  114  or the rotary transmission member  115 . 
         [0055]      FIGS. 9A to 9C  illustrate a particular development of a chair switch shown in  FIGS. 2A to 2E . The difference in this embodiment relative to the embodiments of  FIGS. 2A to 2E  lies in a different configuration of the latching action of the locking slider  38  in the release position and in the locking position. To better illustrate the structure and the mode of operation, components like the buttons  30 ,  32  and the microswitches  40 ,  42  are not shown in the perspective views. While  FIG. 9A  illustrates the release position the locking slider  38  has been moved into the locking position in  FIG. 9B . In that case the locking slider  38  is connected to a first latching portion. In the view in  FIGS. 9A to 9C  the first latching portion is formed by a projection  129  connected to the locking slider  38 . 
         [0056]    That first latching portion corresponds with a second latching portion which is connected to the housing. The second latching portion is here a recess  128  which is part of the spacer leg  34 . As described above the spacer leg  34  is part of the housing. In addition there is a resilient portion  127  arranged besides the recess  128 . When the locking slider  38  is displaced from the release position into the locking position and back, the projection  129  passes the resilient portion  127  in going from one recess  128  to another and in so doing pushes it somewhat to the side so that the projection  129  is arranged in the respective recess  128  or engages somewhat thereinto there in the release position and in the locking position. 
         [0057]    For the sake of simplified description of the mode of operation involved, the variants predominantly involve locking devices which are slidable or which operate with a translatory movement. Rotatable locking devices can also be used, similarly thereto. The locking devices which operate with a translatory movement implement the displacement in respect of height preferably by means of ramps or bevels which slide against each other on the complementary parts, whereas, in the case of the locking devices which operate with a rotary movement, a projection or pin is guided in an arcuate guide with a slope. The rotatable locking devices have the important advantage that a seal can be very easily fitted (as an additional component or as an elastomer component shaped on the structure). 
         [0058]    The subject-matter of the present invention derives not only from the subject-matter of the individual claims but from the combination of the individual claims with each other. All features and details disclosed in the specification—including the Abstract—, in particular the spatial configuration shown in the drawing, are claimed as essential to the invention insofar as they are novel individually or in combination, over the state of the art. 
         [0059]    It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.