Patent Abstract:
The present invention concerns a switching apparatus having an actuating shaft, an actuator, at least one switch and a housing. A switching apparatus in the form of at least one actuating guide which is connected with a first actuating guide portion to the actuating shaft and which with a second actuating guide portion at least partially embraces the actuating shaft at a predetermined spacing, wherein provided on the convex side of the second actuating guide portion is an actuating track for the switch or switches, insofar as at at least one predetermined position the spacing between the outer peripheral edge and the actuating shaft is greater for a predetermined arcuate dimension than at other positions of the second actuating guide portion.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATION  
         [0001]    This application claims priority from the International Application PCT/EP02/04484, filed Apr. 24, 2002, which application is incorporated herein by reference in its entirety.  
         TECHNICAL FIELD  
         [0002]    The present invention concerns a switching apparatus comprising an actuating shaft, an actuator, at least one switch and a housing.  
         BACKGROUND OF THE INVENTION  
         [0003]    Switching apparatuses of that kind are generally known in particular in the form of cam switches and are used in the most widely varying pieces of equipment and for the most widely varying functions. In that respect one or more cam discs are arranged on an actuating shaft. Those cam discs are distinguished in particular in that their outer periphery departs from a circular shape at at least one location and has either a cam dip, that is to say a reduced spacing of the outer peripheral edge with respect to the actuating shaft, or a raised cam lobe, that is to say an increased spacing of the peripheral edge with respect to the actuating shaft.  
           [0004]    Now, an actuating lever extending along such a periphery of a camshaft of such a configuration, for a switch or a contact spring itself, opposite which there is a further contact in the radial direction of the cam disc, can be actuated by the cam disc and can thus trigger a switching operation.  
           [0005]    Depending on the situation off use involved, it is possible to provide a single cam disc which actuates one or more switches, in a complete revolution. Alternatively, it is also possible to provide on a shaft, a plurality of mutually spaced cam discs which then naturally can actuate a plurality of switches, in accordance with the configuration of cam dips and/or raised cam lobes. In that way, a plurality of different switches can be actuated automatically in a predetermined relationship with each other.  
           [0006]    A disadvantage with those known cam switches however is that, for example as a consequence of inevitable tolerances, the precision of such switching mechanisms cannot be increased just as may be desired, and frequently there is a conflict between the requirement for a high level of precision and at the same time a small installation size.  
         SUMMARY OF THE INVENTION  
         [0007]    Therefore one object of the present invention is to develop a switching apparatus of the kind set forth in the opening part of this specification, in such a way that the switching accuracy and the revel of resolution, that is to say the possibility of securely differentiating between two different switching positions, is improved.  
           [0008]    In that respect, the invention is based on the realisation that the level of resolution, precisely in a rotational movement, depends in particular on the length of the arcuate portion during the rotation and thus on the outer periphery of the cam disc.  
           [0009]    In accordance with the invention therefore a switching apparatus of the kind set forth in the opening part of this specification is further developed by the actuator being in the form of at least one actuating guide which is connected with a first actuating guide portion to the actuating shaft and which with a second actuating guide portion at least partially embraces the actuating shaft at a predetermined spacing, wherein provided on the convex side of the second actuating guide portion is an actuating track for the switch or switches, insofar as at at least one predetermined position the spacing between the outer peripheral edge and the actuating shaft is greater for a predetermined arcuate dimension than at other positions of the second actuating guide portion.  
           [0010]    By virtue of that structure, the spacing of the second actuating guide portion from the actuating shaft determines the radius of the actuator and thus also the arcuate portion by which the actuator moves further by a predetermined distance, upon a rotary movement of the actuating shaft. As the relationship between radius and periphery of a circle is linear, the length of the arcuate portion rises for a predetermined angle to the same extent as the radius.  
           [0011]    In a preferred embodiment of the invention the second actuating guide portion is of a predetermined length parallel to the actuating shaft, and has a plurality of actuating tracks for a plurality of switches, said tracks being arranged distributed in mutually juxtaposed relationship over said length. In that way, a suitably designed actuating guide with accordingly also only one fixing on the actuating shaft is sufficient for the actuation of a plurality of switches in a predeterminable manner.  
           [0012]    A preferred feature the present invention employs commercially available switches which are mounted to a first carrier plate. In that way, for example, mounting of the switches on the plate and wiring of the switches can be implemented before installation in the switching apparatus so that the carrier plate with the switches mounted thereon can finally be introduced as a structural unit into the switching apparatus.  
           [0013]    Alternatively to mechanical switches or in addition thereto it is possible to use electronic switches. Those electronic switches are generally designed for a higher number of switching cycles than mechanical switches and thus have a higher level of safeguard against failure. Therefore, the operational reliability of the switching apparatus can be considerably increased by the redundant provision of mechanical and electronic switches. In that respect a suitable arrangement of the switches can restrict the structural size of the switching apparatus.  
           [0014]    In a preferred development of the invention, the actuating shaft is passed through the base plate of the housing so that the actuating shaft is rotatable from the outside. It is possible to arrange at the end of the actuating shaft, which is at the inside of the housing, a rotary sender which represents the position of the shaft in a predeterminable manner independently of the actuation of a switch or a plurality of switches.  
           [0015]    In order to be able to operate the rotary sender with the highest possible degree of freedom from mechanical loadings, a preferred embodiment of the invention provides that the rotary sender shaft is in the form of an actuating shaft for the rotary sender, separately from the actuating shaft for the actuating guide. In order to embody a connection which carries axial and radial forces but which is stiff in torsion, the actuating shaft and the rotary sender shaft are preferably connected by a spring bellows coupling.  
           [0016]    In a preferred embodiment, that rotary sender is a potentiometer and provides a very simple structure. Alternatively the rotary sender can be an incremental sender which for example is integrated in the form of an autonomous structural unit into the switching apparatus and suitably codes the rotational information and outputs the coded information. In that way, the position of the shaft can be continuously ascertained and in addition in predeterminable positions, independently of the rotary sender, the switches can trigger given switching procedures, controlled by way of the actuating guide. That also makes it possible for example to embody a safety circuit which, even in the event of failure of the rotary sender, still permits triggering of given switching procedures when given angular positions are reached.  
           [0017]    A predetermined minimum wall thickness of the cover hood, an in particular shear-resistant connection between the cover hood and the base plate and naturally suitable fixing of the switching apparatus provide a sufficiently high level of load-carrying capability in order for example also in the installation situation to withstand without damage a short-term high shear loading such as a lateral blow and/or someone inadvertently treading thereon.  
           [0018]    If the cover hood fits on the base plate in sealed relationship, that prevents moisture from penetrating into the interior of the switching apparatus. That permits reliable long-term operation. It will be appreciated that a seal can be provided between the base plate and the cover hood. In that respect, the fixing of the cover hood to the base plate can be such that the seal is disposed between the cover hood and the base plate and is biased by the cover hood.  
           [0019]    Further advantageous embodiments of the invention are set forth in the appendant claims. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]    Embodiments by way of example of the invention are described in greater detail hereinafter with reference to the drawings in which:  
         [0021]    [0021]FIG. 1 is a simplified plan view of the base plate of a switching apparatus according to the invention in a first embodiment,  
         [0022]    [0022]FIG. 2 is a side view of an open switching apparatus according to the invention in the first embodiment,  
         [0023]    [0023]FIG. 3 is a simplified plan view of the base plate- of a switching apparatus according to the invention in a second embodiment,  
         [0024]    [0024]FIG. 4 is a side view of an open switching apparatus according to the invention in the second embodiment,  
         [0025]    [0025]FIG. 5 is a simplified plan view of the base plate of a switching apparatus according to the invention in a third embodiment,  
         [0026]    [0026]FIG. 6 is a side view of an open switching apparatus according to the invention in the third embodiment,  
         [0027]    [0027]FIG. 7 is a side view of an open switching apparatus according to the invention in the fourth embodiment,  
         [0028]    [0028]FIG. 8 shows a view of an outside of the base plate,  
         [0029]    [0029]FIG. 9 is a general sketch of the regulation according to the invention, and  
         [0030]    [0030]FIG. 10 shows a view of the structure according to the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0031]    In FIG. 1, shown in the centre of the base plate  10  is an actuating shaft  16 ; the position of the actuating shaft  16  can alternatively be eccentric. The actuating shaft passes through the base plate  10  and can be actuated from the side of the base plate  10 , remote from the view shown in the drawing.  
         [0032]    Fixed to the actuating shaft  10  is a first crank or actuating guide portion  19 . That fixing can be for example in positively locking relationship, so that rotation of the actuating shaft  16  always entrains the first actuating guide portion  19 .  
         [0033]    The first actuating guide portion  19  is connected to a second actuating guide portion  20  by way of a leg shown in the Figure above the actuating shaft  16 . That second actuating guide portion  20  has raised cam portions  23  at predetermined positions. Also shown at the convex side of that second actuating guide portion  20  is a switch  22  which is arranged in a housing and which has an actuating lever which is at a small spacing relative to the surface of the second actuating guide portion  20 . In this case, the spacing between the actuating lever of the switch  22  and the second actuating guide portion  20  is less than the height of the two raised cam portions  23  with respect to the part, which is disposed therebetween, of the second actuating guide portion  20 .  
         [0034]    The first actuating guide portion  20  is entrained by a rotary movement of the actuating shaft  16  and thus the second actuating guide portion  20  also moves along under the actuating lever of the switch  22 . As soon as one of the raised cam portions  23  reaches the actuating lever of the switch  22 , that actuating lever is moved towards the switch  22  and the switch  22  is actuated. In that way, it is possible clearly to detect that the actuating shaft  16  has reached a predetermined position.  
         [0035]    If now the actuating shaft  16  moves in the opposite direction, the raised cam portion  23  moves out from under the actuating lever of the switch  22  and the switch  22  can move back into its rest position again. This also makes it possible clearly to recognise an oppositely directed rotary movement of the actuating shaft  16 .  
         [0036]    [0036]FIG. 2 shows a side view of an open switching apparatus according to the invention. A base plate  10  has a bearing seat  14  through which the actuating shaft  16  is passed. In this case the actuating shaft  16  can be supported for example in a ball-type rotational connection in the form of a bearing  32 . In addition the base plate  10  has a through opening  12  as a cable ducting means, through which connecting cables can be passed out of the switching apparatus which in operation is closed. For sealingly closing those cable openings  12 , it is possible to use gland packing boxes which are generally known and therefore not described in greater detail here.  
         [0037]    In FIG. 2, the region to the right of the base plate is the region which, when the switching apparatus is in the final assembled condition, is covered by a cover hood  36  (shown in broken line) and thus forms the interior of the switching apparatus while the region to the left of the base plate  10  is outside the housing of the switching apparatus.  
         [0038]    It can be easily seen that the actuating shaft  16  extends a predetermined length outside the casing and ends in a connecting sleeve  30 . By way of that connecting sleeve  30 , the actuating shaft  16  can be non-rotatably connected to a further shaft, the rotational position of which is to be established.  
         [0039]    At the inside of the base plate  10 , a first actuating guide portion  19  of a actuating guide is arranged on the actuating shaft  16  in such a way that it is reliably entrained in the rotational movement of the actuating shaft  16 . This can be achieved for example by a positively locking connection.  
         [0040]    Connected to the first actuating guide portion  19  is a second actuating guide portion  20  which, in the present embodiment, extends at a predetermined spacing in the form of a segment of a circle in concentric relationship around the actuating shaft  16  (see in particular FIG. 1). In this case the length of that second actuating guide portion  20  is such that a plurality of actuating tracks are distributed over the length thereof, which tracks can actuate a plurality of mutually juxtaposed switches  22  separately from each other.  
         [0041]    In addition, a first carrier plate  21  is fixed to the base plate  10  in such a way that it extends parallel to the actuating shaft  16  at a predetermined spacing. A plurality of switches  22  are fixed to that first carrier plate  21  in mutually juxtaposed relationship at such a spacing that the actuating lever of each switch  22  is disposed opposite a given actuating track of the second actuating guide portion  20 . A rotary movement of the actuating shaft  16  provides that the first actuating guide portion  19  and therewith also the second actuating guide portion  20  are correspondingly entrained and raised cam portions  23  provided on the second actuating guide portion  20  at predetermined positions actuate the switches  22  (see in particular FIG. 1).  
         [0042]    A second carrier plate  24  is mounted to the side of the first carrier plate  21 , which is remote from the base plate, perpendicularly to the first carrier plate  21 . That second carrier plate  24  carries an incremental sender  26 .  
         [0043]    That incremental sender  26  is in turn connected to the actuating shaft  16  and outputs the rotational position of the actuating shaft  16  in the form of a suitably coded electrical signal.  
         [0044]    The rotary movement of the actuating shaft  16  always directly influences the incremental sender  26  so that the latter shows any rotation of the shaft in the form of electrical signals. Independently of the incremental sender, given predeterminable rotational positions of the actuating shaft  16  can be detected by virtue of the actuation of switches  22  as the position of raised cam portions  23  on the actuating track of the second actuating guide portion  20  permits corresponding actuation of the switches  22  independently of the incremental sender  26 .  
         [0045]    In order to compensate for excessive fluctuations in the operating conditions of that switching apparatus, it is possible to provide for example a heating resistor  34  which is switched on when necessary in order to heat up the interior of the switching apparatus by the conversion of electrical energy into heat.  
         [0046]    The operation of mounting the cover hood  36  (shown in broken line in this Figure) to the base plate  10  can be effected for example by the cover hood  36 , in the region near the base plate, having a female screwthread which can be screwed to a corresponding male screwthread on the base plate  10 . Alternatively it is possible to provide screwthreaded rods (not shown for the sake of clarity) which extend from the base plate  10  parallel to the actuating shaft  16  beyond the incremental sender  26 . In such a case, the cover hood  36 , at the side remote from the base plate, can have bores through which those screwthreaded rods project by a predetermined length so that nuts can be screwed thereon from the exterior, to press the cover hood in its fit against the base plate  10 .  
         [0047]    In addition the fixing (also not shown) of the cover hood  36  can be effected by screws at the periphery of the cover hood  36 , which for example either engage in the radial direction of the switching apparatus into corresponding screwthreaded bores in the base plate  10  or which engage through the base plate  10  in the axial direction into screwthreads of a suitable nature in the cover hood  36 .  
         [0048]    [0048]FIG. 3 shows a simplified plan view of the base plate of a second embodiment of a switching apparatus according to the invention and FIG. 4 shows a side view of this embodiment. As this embodiment and the embodiments described hereinafter are also based on the same principle as the first embodiment, in particular the differences in relation to the first embodiment will be referred to here.  
         [0049]    In this second embodiment, the essential difference is that the second actuating guide portion  20  extends completely around the actuating shaft  16 . In this case, the plane of the area enclosed by the second actuating guide portion  20  extends radially with respect to the actuating shaft  16 .  
         [0050]    Switches  22  are arranged at uniform spacings over the outside periphery, in dependence on the intended maximum rotary angle of the switching apparatus. In the illustrated embodiment the rotary angle does not exceed 120° and thus three switches can be distributed over the periphery (see in particular FIG. 3). That arrangement therefore permits a more compact structure for a switching apparatus according to the invention. In this respect, FIG. 4 shows an arrangement having a third carrier plate  25  on which two switches  22  are arranged.  
         [0051]    The respective switching time derives from the position of the raised cam portions  23 . In the case of two switches  22  as shown in FIG. 3, there are two raised cam portions  23  so that those switches  22  are actuated in both directions of rotation towards the end of the rotational travel, but at different positions and thus at different moments in time. The third switch illustrated at the left in the Figure is shown in the actuated condition. The raised cam portion  23  has urged the actuating lever towards the switch  22  and thus caused the switching operation. In that case that switch  22  is actuated approximately at the centre of the rotational travel independently of the direction of rotation. It will be appreciated that any other combinations can be envisaged.  
         [0052]    [0052]FIGS. 5 and 6 show a further embodiment in which optical switches, for example in the form of fork-type light barrier arrangements, are used in place of mechanical switches  22 . It can be seen from FIG. 5 that the second actuating slide guide portion  20  again extends completely around the actuating shaft  16 . In FIG. 6, the side view shows that the raised cam portions provided for triggering the switching cycles can here be markedly narrower than is required for reliable actuation of mechanical switches.  
         [0053]    [0053]FIG. 7 shows a side view of a fourth embodiment of the switching apparatus according to the invention. In this case, instead of fork-type light barrier arrangements, reflection couplers are used as the switches  22  in order once again to produce corresponding signals by optical means. in order to avoid the switches  22  influencing each other in the case of a cam dip, the switches are arranged in two planes but in displaced relationship with each other, in such a way that no two switches  22  are disposed in opposite relationship. In that way, a suitable choice of the positions of the raised cam portions and the cam dips makes the structure of a switching apparatus according to the invention even more compact.  
         [0054]    The mode of operation of a reflection coupler as a switch  22  differs in that respect from the mode of operation of a fork-type light barrier arrangement. In the case of the fork-type light barrier arrangement, the transmitter and the receiver are disposed separately in the mutually oppositely disposed fork arms. As long as no raised cam portion  23  interrupts that path, the switching operation is triggered. If a raised cam portion  23  is disposed between the transmitter and the receiver, the optical connection and therewith also the switching operation are interrupted. In the case of a reflection coupler, the transmitter and the receiver are disposed on the same side. As soon as a raised cam portion  23  is in front of the reflection coupler, the light emitted by the transmitter is reflected by the raised cam portion  23  and triggers the switching operation in the receiver. If no raised cam portion  23  is disposed in front of the reflection coupler, then the light emitted by the transmitter is not reflected and the switching operation is interrupted.  
         [0055]    It will be appreciated that it is also possible to use switches based on other physical effects such as Hall sensors, reed contacts and so forth. It is also appropriate to use a combination of mechanical and electronic switches  22  if the level of reliability is to be increased. In the event of failure of a mechanical switch, the signal of the electronic switch can still trigger the desired procedure and at the same time a functional disturbance can be detected from the difference between the signals of the two switches (more specifically for example by virtue of the absence of the signal from the mechanical switch), and the procedure for eliminating the functional disturbance can thus be initiated without the basic operability of the switching apparatus suffering.  
         [0056]    In order to achieve an unambiguous and well-defined switching characteristic, each switch can have a hysteresis between the switching-on and the switching-off points. Depending on the nature of the switch that hysteresis can be produced mechanically (for example by a quick-break switch) and/or electronically (for example by a Schmitt trigger). In addition, it is possible to provide a device which checks in particular the plausibility of the switching signals, for example by a comparison of parallel switches and/or a predetermined actuating sequence, and if necessary triggers a corresponding signalling procedure. That device may include for example discrete and/or integrated digital circuits and in particular a microcontroller or a microprocessor.  
         [0057]    In addition, in FIG. 7 the first actuating guide portion  19  and the second actuating guide portion  20  are moved into the same radial plane and thus form a unit in the side view.  
         [0058]    [0058]FIG. 8 is a view of the outside of a base plate  10  with the centrally illustrated actuating shaft  16  and the connecting sleeve  30  extending therearound. Provided beside that connecting sleeve  30  is a plug connector  38 . The plug connector  38  is fixedly mounted and fitted with the electrical connections through a suitable orifice in the base plate  1   0 , from the inside of the switching apparatus. Replacement of the switching apparatus can thereby be effected without simultaneously replacing the connecting cables for the switching apparatus and vice-versa, and that therefore simplifies the working operations involved.  
         [0059]    In the illustrated embodiment the plug connector is in the form of a three-row, 14-pole plug connector. The illustrated contacts are similar to so-called blade contacts, in which respect the plug connector can be both in the form of a socket and also in the form of a male plug. It will be appreciated that the embodiment is also not limited to blade contacts. Rather, it is possible to use any suitable kind of plug connector.  
         [0060]    Viewing FIGS. 9 and 10 together, FIG. 9 shows schematically the interconnection between a control  6  of a rotor blade  42 , the drive  4  for pitch adjustment of the rotor blade  42  as well as the compact limit switch  2  and the switching apparatus  8  which is controlled by the compact limit switch  2  and which is also in the form of a relay. The drive  4  is a motor assembly coupled to the rotor blade  42  to cause rotation of the blade  42  and change its pitch to a desired location. As will be seen, the drive  4  for changing the pitch and adjustment of the rotor blade  42  is controlled by the control device  6 . It predetermines for the rotor blade  42  its angular orientation which, depending on the respective wind conditions, is directed at the optimum, which is predetermined by the control system  6 . For the situation involving shutting down the installation, this can also mean that the rotor blade  4  is moved into the feathered position, while at other times it may be at partial power or full power pitch positions. As will also be seen, the rotor blade  4  is rigidly connected to the shaft  16  so that as the blade  4  is rotated to change the pitch, the shaft  16  is also caused to rotate. Therefore, pitch position of the blade  4 , by way of the actuating shaft  16 , controls the position of the arcuate portion  20  of the switch  2 . If, during rotation, one of the projections  23  of the switch  2  comes into contact with the switch  22 , then by way thereof the switching function of the switching apparatus  8  is triggered and the drive is switched off. The control device  6  also receives a signal from the compact limit switch  2  and can accordingly control the drive  4  in the desired manner, so that damage to the rotor blade is prevented.  
         [0061]    [0061]FIG. 10 shows the arrangement of the switch  2  in conjunction with the rotor blade. It will be seen in this respect that the limit switch  2  is arranged on a holding device  44  on one side of the pitch bearing. The limit switch and housing  36  are always stationary when the rotor blade moves while the shaft  16  rotates as the rotor blade is rotated to change its pitch. By way of the actuating shaft  16 , the switch  2  is connected by sleeve connector  30  to the rotor blade  12 , with a suitable holder  48  at the end of the shaft  16 . When the rotor blade rotates, that automatically results in corresponding rotation of the shaft and a corresponding switch position in the compact limit switch  2 .  
         [0062]    From the foregoing it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the invention. Accordingly, the invention is not limited except as by the appended claims.

Technology Classification (CPC): 5