Abstract:
The present disclosure relates to a short-travel key comprising a touch body for actuating the short-travel key, wherein at least two redundantly arranged microswitches are provided which are actuable via the touch body and wherein the short-travel key has only one tactile pressure point.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to German Patent Application No. 10 2011 010 760.6, entitled “Short-Travel Key”; filed Feb. 9, 2011, which is hereby incorporated by reference in its entirety for all purposes. 
       TECHNICAL FIELD 
       [0002]    The present disclosure relates to a short-travel key which comprises a touch body for actuating the short-travel key. 
       BACKGROUND AND SUMMARY 
       [0003]    Generic short-travel keys have a touch body accessible to the user. The pushing pressure effects a movement of the touch body which cooperates with a microswitch to trigger a corresponding switch state. The microswitch can be either of an electrical or mechanical nature. 
         [0004]    So-called tactile short-travel keys prove to be advantageous when a feedback to the key operator is required. Tactile short-travel keys have a pressure point which is tactile for the operator and which communicates the successful triggering of the switch state. As a rule, the reaching of the pressure point is additionally assisted by an acoustic sound, for example by a click or the like. 
         [0005]    The generic short-travel keys are in particular used with functional keyboards or special control panels. Such keyboards or control panels are in particular used in work machines as input devices for the direct control of the machine. The increasing safety requirements in the industry also cover the design of the keyboards or control panels used. The functional security is guaranteed in that the key function can no longer be triggered on a failure of one or more components. An unwanted incorrect operation (malfunction), caused by a component error of the key, is thereby avoided. 
         [0006]    While taking the above into account, it is the object of the present disclosure decisively to increase the functional security and operating security of a generic short-travel key significantly by a direct further development thereof. 
         [0007]    This object is achieved by a short-travel key having a touch body which serves the actuation of the short-travel key. In accordance with the present disclosure at least two redundantly arranged microswitches are provided. The microswitches arranged redundantly to one another, in particular short-travel microswitches, are in contact with the touch body and can be actuated by the travel movement of the actuated touch body. The key function is only ensured when both microswitches are contacted. 
         [0008]    One or more microswitches work in accordance with a mechanical and/or electrical switching principle. The switching principles of at least some of the microswitches used can differ from one another or can be identical. Exactly two microswitches may be arranged redundantly to one another. 
         [0009]    The feedback of the short-travel key for signaling the successful switch actuation should be unambiguous despite the redundantly designed microswitches. Provision is therefore made in accordance with the present disclosure that the short-travel key only has a tactile pressure point. The arrangement of the redundantly designed microswitches accordingly takes place such that only a single tactile pressure point can be felt despite the parallel actuation of the at least two microswitches. 
         [0010]    The touch body used is optionally of parallelepiped shape, in particular cuboid, with the lower side coming into contact with the microswitches to actuate them. In the unloaded state, i.e. without an effect of force of the operator, the touch body expediently contacts at least one microswitch. 
         [0011]    The upwardly disposed front side of the touch body is optionally cut out for inserting a touch cap. The touch cap forms the pressure point for the operator of the short-travel key. 
         [0012]    The requirement of providing the short-travel key with a single tactile pressure point is advantageously achieved in that the short-travel key includes a single tactile microswitch and at least one non-tactile microswitch. The pressure point noticeable for the operator is accordingly only generated by the tactile microswitch. 
         [0013]    There is optionally only a contact between the non-tactile microswitch(es) and the touch body in the unloaded state. 
         [0014]    It can be advantageous to arrange at least one support surface at the touch body in such a manner as to limit the maximum possible travel movement of the touch body for the microswitch actuation. The touch body is in contact with the movably supported switch element of the microswitch optionally designed as a pressure switch. The pressure of the touch body exerted onto the switch element or pressure element of the microswitch triggers a switching state change on reaching a defined pressure level. The contact between at least one support surface and the fixed part of the microswitch limits the maximum travel of the touch body. A complete pressing in of the microswitch pressure element is suppressed, which contributes to the saving of material of the short-travel microswitches used. 
         [0015]    In a particularly advantageous embodiment of the short travel key, at least one support surface is not arranged centrally in the region of all microswitches, but rather off-center in the contact region of the touch body with the non-tactile microswitch(es). The resulting only contact of the support surface with the non-tactile microswitch(es) effects a lever arm function of the support surface. The touch body is inclined in the direction of the tactile microswitch, which improves the function of the short-travel key in the interaction of both microswitches. 
         [0016]    At least one guide is advantageously provided at the touch body and is in engagement with at least one microswitch. A stable position of the touch body on the microswitch(es) is achieved by the guide. A centration of the touch body on the non-tactile short-travel microswitch is in particular achieved. This allows the guidance of the touch body over the total height up to the front plate cut-out of the touch body, which improves the function of the short-travel key and excludes the risk of jamming. A ball guide has proved particularly advantageous. 
         [0017]    One or more webs standing perpendicular on the touch body surface are in particular arranged on the side of the touch body facing the microswitch. The webs simplify the installation of the short-travel key in accordance with the present disclosure, in particular the equipping of the microswitches fastened to a circuit board with the corresponding touch body. The webs advantageously have a conical extent with a periphery converging starting from the touch body. The webs expediently form the corner points of an imaginary rectangle which accepts the at least two microswitches in its middle. 
         [0018]    It is conceivable that the microswitches and the touch body are arranged such that a defined switching order of the microswitches is followed on their interaction. It can be expedient that the microswitches are not switched simultaneously, but with a travel delay by the touch body. 
         [0019]    The switching order is advantageously fixed such that first the non-tactile microswitch is triggered by the touch body and the tactile microswitch is actuated with a travel delay. It is ensured in this manner that a tactile feedback only takes place after the successful switching state change of both microswitches. 
         [0020]    The present disclosure further relates to a keyboard or to a control panel having at least one short-travel key in accordance with one of the above-explained feature combinations. The keyboard or the control panel evidently has the same advantages and properties as the previously described short-travel key so that a repeated explanation will be omitted at this point. 
         [0021]    Further advantages and particulars of the present disclosure will be explained in detail with reference to an embodiment shown in the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0022]      FIG. 1  shows a perspective lower view of the touch body of the short-travel key in accordance with the present disclosure. 
           [0023]      FIG. 2  shows the short-travel key in accordance with the present disclosure in a plan view. 
           [0024]      FIG. 3  shows a cross-sectional representation of the short-travel key in accordance with the present disclosure. 
           [0025]      FIG. 4  shows a perspective cross-sectional representation of the short-travel key in accordance with the present disclosure. 
           [0026]      FIG. 5  shows a schematic representation of the functional principle of the short-travel key in accordance with the present disclosure.  FIGS. 1-4  are drawn approximately to scale, although other dimensions are possible. 
       
    
    
     DETAILED DESCRIPTION 
       [0027]    The present application relates to a short-travel key that may be positioned in a device  8 , such as a functional keyboard or a special control panel. Such keyboards or control panels may be positioned in a work machine (such as a crane, for example) as an input device for the direct control of the machine. As such, element  8  may represent a keyboard, control panel, a keyboard positioned in a work machine, and/or a control panel positioned in a work machine. 
         [0028]    The perspective representation of  FIG. 1  shows the touch body  10  of the short-travel key in accordance with the present disclosure in a view from below. The touch body  10  has roughly almost a cuboid shape; with the side walls of the touch body  10  forming the hollow space  13  in the interior space. The upper side or front plate of the touch body is completely cut-out for receiving a releasable touch cap. The downwardly lying side surface  11  of the touch body  10  is let piece-wise into the hollow space  13  of the touch body  10  while forming the projecting margin  12 . 
         [0029]    Furthermore, the two support surfaces  40  are arranged on the lower side  11  close to the margin and disposed on a common axis. Four conical webs  51  are furthermore fastened close to the margin and project perpendicular from the lower side  11  and terminate with the margin  12 . 
         [0030]    The ball guide  60  which is arranged at the same spacing centrally between two conical webs next to the support surfaces  40  serves as a connection means between the touch body and the microswitches  20 ,  30 . The ball guide  60  ensures a stable and central positioning of the touch body  10  on the non-tactile short-travel microswitch  30 . For equipping, the touch body is placed from above onto the two microswitches and is fixed sufficiently via the ball guide to the non-tactile short-travel switch  30 . 
         [0031]      FIG. 2  shows a plan view of the short-travel key in accordance with the present disclosure. In the embodiment shown, the short-travel key is shown without a touch cap and fiber optics for illuminating the touch cap. The Figure allows a view through the cut-out front plate into the hollow space  13  of the touch body  10  up to the two short-travel microswitches  20 ,  30 . 
         [0032]    The microswitches  20 ,  30  made as pressure switches can easily be recognized in detail in the Figure. The microswitches each include a fixed switch element  21 ,  31  and a pressure element  22 ,  32  movably supported thereon for switch actuation. The pressure force introduced onto the touch body  10  or onto the fastened touch cap effects a travel movement of the touch body in the direction of the microswitches  20 ,  30  whose pressure elements  22 ,  32  are pressed into the fixed switch elements  21 ,  31  from the lower side  11  of the touch body. 
         [0033]    Both microswitches can work in accordance with an electric or mechanical switching principle. 
         [0034]    In the assembled state, the microswitches  20 ,  30  lie aligned adjacent and parallel to one another in the region between the four conical webs  51  arranged symmetrically to one another. A corresponding preceding parallel and adjacent alignment of the microswitches on the circuit board  50  is necessary for the following equipping with the touch body  10 . 
         [0035]    The microswitch  30  is designed as a non-tactile microswitch and the microswitch  20  as a tactile microswitch. Only the tactile microswitch  20  has a pressure point tangible for the operator. In addition, the tactile microswitch  20  can output a click for signaling the switching state change. Furthermore, it can be seen from  FIG. 2  that only the non-tactile microswitch  30  or the fixed switch element  31  lies in the contact region of the support surfaces  40 . 
         [0036]      FIGS. 3 ,  4  show a cross-section of the short-travel key in accordance with the present disclosure, with  FIG. 3  showing a side view of the cross-section and  FIG. 4  showing a perspective view of the cross-section. Both representations show the short-travel key without the touch cap and corresponding fiber optics. The two microswitches are electrically connected, in particular soldered, to the circuit board  50 . 
         [0037]    In both  FIGS. 3 ,  4 , the movably supported pressure elements  22 ,  32  can be easily recognized which are in direct contact with the lower side  11  of the touch body  10 . The travel movement of the touch body  10  generated by the effect of force presses the pressure elements  22 ,  32  into the fixed switch elements  21 ,  31  of the microswitches  20 ,  30 . The ball guide  60  contributes to the sufficient guidance of the touch body  10  over the total height up to the front plate cut-out, which improves the function of the short-travel key and precludes the risk of jamming during the travel movement. 
         [0038]    The conical webs  51  and the two conical noses  70 , which are integrated in the margin  12 , serve as an installation aid in the equipping of the corresponding microswitches  20 ,  30  with the touch body  10 . 
         [0039]      FIG. 5  shows a schematic representation of the operation of the short-travel key in accordance with the present disclosure. In the starting position, that is in the pressure-relieved position of the touch body  10 , the lower side  11  of the touch body is only in contact with the pressure element  32  of the non-tactile microswitch  30 . The switching order of the short-travel key in accordance with the present disclosure is defined in this respect so that first the non-tactile microswitch  30  should be triggered until then the tactile microswitch  20  is actuated with travel delay. The schematic representation in  FIG. 5  divides the switching process of the short-travel key in accordance with the present disclosure which takes place into the three chronologically shown switching paths. 
         [0040]    In the first switching path, the touch body  10  is moved in the direction of the microswitches  20 ,  30  by the exertion of force onto the touch body so that the pressure element  32  of the non-tactile microswitch  30  is pressed into the fixed switch element  31  until a contact is established between the pressure element  22  of the tactile microswitch  20  and the lower side  11  of the touch body  10 . 
         [0041]    In the second switching path, the touch body  10  is moved so far in the direction of the microswitches  20 ,  30  until the switching state of the non-tactile microswitch  30  is triggered. The adjoining third switching path comprises the triggering of the tactile microswitch  20  due to the continuing travel movement of the touch body, with a tactile feedback to the operating person of the touch body  10  taking place. In addition, an assisting acoustic feedback can be output in the form of a click. 
         [0042]    The support  40  is in contact with the fixed switch element  31  of the non-tactile microswitch  30  and limits the maximum travel movement of the touch body  10 . A complete pressing in of the pressure elements  22 ,  32  is hereby successfully suppressed, whereby both short-travel microswitches  20 ,  30  are protected. The off-center arrangement of the support surfaces  40  furthermore acts as a lever arm mechanism. The corresponding arrangement effects a tilting of the touch body  10  in the direction of the tactile short-travel microswitch  20 , which improves the function of the short-travel switch in the interaction of both microswitches  20 ,  30 .