Patent Publication Number: US-10332706-B2

Title: Bimetal controller

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is the U.S. national phase of PCT Application No. PCT/EP2011/061087 filed on Jul. 1, 2011, now published as WO 2012/004197, which claims priority to German Patent Application No. 10 2010 017 741.5 filed on Jul. 5, 2010, the disclosures of which are incorporated in their entirety by reference herein. 
     TECHNICAL FIELD 
     The invention relates to a bimetal controller comprising a switching device and at least one bimetal device, which is or can be actively connected to the switching device in such a way as to allow a temperature-dependent switching of the switching device. 
     BACKGROUND 
     Such bimetal controllers are known from the prior art. 
     A bimetal or thermobimetal is a metal element comprising two layers of different materials which are connected to each other with a material bond or a form fit. The change in shape when there is a change in temperature is characteristic. The change in shape is manifested as a bending of the bimetal. This is caused by the different coefficients of thermal expansion of the metals used. If one metal expands more than the assigned other metal, there is a bending of the combination of metal layers. The two metals are usually connected to each other by rolling, and in particular cold welding, or else by mechanical connecting means, such as for example rivets. 
     A known application area of such bimetals is that of temperature-dependent switches, the bimetals being used here such that they actuate a switching device when there are changes in temperature and the accompanying bendings occur. 
     DE 894 469 shows for example such a bimetal controller or switch, in which a bimetal is attached by one end to a base structure and is actively connected by a free end to a switching device. This switching device consists of two switching elements, which can be set in relation to each other by way of a stop plate. When there is a deformation of the bimetal controller, this causes a closing of the contacts of the two switching elements, that is to say a switching operation, by way of which an assigned electrical appliance, etc. can be activated. 
     DE 889 782 shows a similar bimetal controller, in which the bimetal is likewise attached by one end on a base structure and is actively connected by another, free end to a switching device. Here, too, the switching operation triggered by the bending of the bimetal element at the free end can be set by way of a suitable setting device. 
     The bimetal controllers known from the prior art usually cannot be set accurately enough with regard to the switching temperature. This is in evidence particularly in the case of very small bimetal controllers. 
     SUMMARY 
     The object of the invention is consequently to offer a bimetal controller of the type mentioned at the beginning which ensures a switching behavior that can be accurately set and/or a small hysteresis, in particular also with a small construction. 
     This object is achieved by a bimetal controller according to patent claim  1 . 
     In particular, this object is achieved by a bimetal controller comprising a switching device and at least one bimetal device, which is or can be actively connected to the switching device in such a way as to allow a temperature-dependent switching of the switching device, the bimetal device having at least one first bimetal element and at least one arcuate, second bimetal element, which are connected to each other at a contact region and are formed at the contact region in such a way that the coefficient of thermal expansion of the first bimetal element decreases from the underside thereof to the upper side and the coefficient of thermal expansion of the arcuate, second bimetal element increases from its underside to the upper side, or vice versa. 
     Such an arrangement comprising at least two bimetal elements which are connected to each other and are formed such that they have an opposing progression of the coefficients of thermal expansion in the contact region leads to a bimetal device with greater switching movements when there are changing ambient temperatures in comparison with the bimetal devices that are known from the prior art. 
     Preferably, at least the first bimetal element and at least the arcuate, second bimetal element are constructed from in each case at least two element layers with different coefficients of thermal expansion, the layer structure of the first bimetal element progressing oppositely to the layer structure of the arcuate, second bimetal element with respect to the coefficients of thermal expansion. 
     An essential point is that the bimetal device of the bimetal controller according to the invention consists of at least two bimetal elements, to be specific at least one first bimetal element and at least one second, arcuate bimetal element, both bimetal elements being multilayer elements and the layer elements used for each bimetal element having such different coefficients of thermal expansion that the respective bimetal element deforms in dependence on the ambient temperature. According to the invention, the two bimetal elements are in this case connected to each other at a contact region such that the layer structure of the first bimetal element progresses oppositely to the layer structure of the arcuate, second bimetal element with respect to the coefficients of thermal expansion. 
     Within the scope of the invention, this “opposed arrangement” of the layer structure is understood as meaning such an arrangement in which the layer structure of the first bimetal element, considered from the layer with the lower coefficient of thermal expansion to the layer with the higher coefficient of thermal expansion, progresses oppositely to the layer structure of the second, arcuate bimetal element with respect to the coefficients of thermal expansion. Thus, for example, a bimetal element comprising a lower layer with a high coefficient of thermal expansion and an upper layer with a lower coefficient of thermal expansion, or quite generally a bimetal element with a coefficient of thermal expansion decreasing from the underside to the upper side, and a bimetal element comprising a lower layer with a low coefficient of thermal expansion and an upper layer with a higher coefficient of thermal expansion, or the coefficient of thermal expansion increasing from the underside to the upper side, therefore meet each other in the contact region. To this extent, bimetal devices in which the first bimetal element has a different layer structure, inter alia with respect to the number of layers or the materials used or the material thicknesses, than the second, arcuate bimetal element are therefore also within the scope of the invention, as long as an “opposed layer structure” is provided, in particular in the contact region. 
     “Arcuate” is understood within the scope of this invention as meaning any kind of deviation from a straight line or a principal axis of extent of the bimetal element, and in particular a shape, particularly a shape of an arc of a circle, in which a partial region of the bimetal element runs in a direction offset by at least 90 degrees in relation to the other partial region of the first and/or second bimetal element. 
     The way in which, according to the invention, the first bimetal element is arranged and formed in relation to the second, arcuate bimetal element provides a bimetal device in which the individual movements of the two bimetal elements connected to each other are added together particularly effectively, which leads to a particularly effective switching movement. The result is a bimetal controller in which great movements occur at the bimetal device even when there are small changes in temperature, so that, inter alia even when there are small changes in temperature, switching operations can be performed. The resultant bimetal controller is consequently very much more sensitive in comparison with controllers from the prior art. 
     Preferably, the bimetal device comprises a plurality of combinations of first bimetal elements and arcuate, second bimetal elements arranged in series. In this way, the great switching movements can easily be added together. The bimetal device is in this case preferably formed such that the arrangement of first bimetal elements and arcuate, second bimetal elements alternates, the opposed arrangement of the layer structures of the respective bimetal elements also again being respectively in evidence here. It is also possible to form the bimetal device in such a way that a combination of the first bimetal element and the arcuate, second bimetal element is connected to a further combination of a first bimetal element and an arcuate, second bimetal element by way of a further intermediate element and preferably a non-bimetallic intermediate element. It is also possible to form the bimetal device in a meandering manner by corresponding arrangement of the first and second bimetal elements, in particular in order in this way to compensate for movements substantially perpendicularly to the main direction of movement (that is to say the direction of movement that brings about a switching operation). Moreover, it is conceivable also to arrange said intermediate elements and preferably non-bimetallic intermediate elements between at least one first bimetal element and an arcuate, second bimetal element. 
     Preferably, the first bimetal element and/or the arcuate, second bimetal element is/are formed as a bimetal strip/bimetal strips. Being formed by a bimetal strip/bimetal strips ensures a switching movement of the bimetal device in a defined direction of movement. 
     Preferably, the contact region is arranged at the one, distal end of the first bimetal element and a proximal end of the arcuate, second bimetal element. In this way, a particularly effective addition of the respective bimetal element movements is obtained when there are changes in temperature. 
     Preferably, the arcuate, second bimetal element describes a half arc to almost a full arc and in particular a three-quarter arc, in particular a half arc of a circle to almost a full arc of a circle and in particular a three-quarter arc of a circle. In this way, the element movements of the first bimetal element and the arcuate, second bimetal element when there is a change in temperature add together particularly effectively to form a common switching movement, the bimetal device at the same time being given a very compact structure. 
     Preferably, the arcuate, second bimetal element has at its distal end a switching region, in particular a substantially linearly formed switching region, which is or can be actively connected to the switching device. By the movement of the first bimetal element, coupled with the movement of the second, arcuate bimetal element, a switching movement is transmitted very easily to the switching device by way of the switching region. 
     Preferably, the principal axis of extent of the switching region and the tangent adjoining thereto of the arcuate, second bimetal element include an angle of &lt;180 degrees, in particular an angle of ≤90 degrees. In this way, a very compact component is obtained, along with a very effective combination of the individual bimetal movements when there are changes in temperature. 
     Preferably, the switching region of the arcuate, second bimetal element is arranged axially parallel to the principal axis of extent of the first bimetal element when there is a defined normal temperature T.sub.0. In particular in the case of a second bimetal element substantially in the form of a full arc or a full circle, a bimetal element with very great switching travel is thus obtained, with at the same time a compact construction of the controller. 
     Preferably, the bimetal device is mounted with a proximal end of the first bimetal element substantially restrained in relation to the switching device. On the basis of this point of restraint, a bimetal device with very great switching travel that can also be arranged in a very confined space is obtained. 
     Preferably, in the case of the arcuate, second bimetal element, the element layer with the higher coefficient of thermal expansion is arranged in the region of the inner arc. In this way, a bimetal device which expands very greatly when there is an increase in temperature and acts on a switching device arranged in the area around the outside of the bimetal device is obtained. In the case of a switching device which is arranged substantially within the bimetal device, in the case of which a contraction of the bimetal device is therefore necessary to activate the switching movement, the element layer with the higher coefficient of thermal expansion is preferably arranged in the region of the outer arc of the second bimetal element. 
     The present invention also relates to an apparatus for the electrically conducting connection of at least one conducting element to aforementioned bimetal controllers or to a contact element of such a switching device that is mounted in a housing, a clamping device which has the following being provided: a clamping bolt and a clamping bolt receptacle, which together define a clamping space into which the conducting element can be introduced from the outer side of the housing and into which the contact element protrudes from the inner side of the housing, the clamping bolt being held in its axial direction in the housing and lying with a clamping continuation against the contact element in an unconstrained manner, and a counter bearing region of the clamping bolt receptacle being able to be moved toward the clamping continuation and the contact element lying on it and able to be fixed at least in one clamping position such that the conducting element and the contact element are fixed with respect to each other in an electrically conducting manner, without a flexural loading being introduced into the contact element. 
     The advantage of such an apparatus or of a bimetal controller formed in this way is that the connection of a conducting element to the bimetal controller is possible without involving any introduction of heat, for example by a welding or soldering operation. According to the invention, such introduction of heat in the case of bimetal controllers from the prior art leads to a weakening of the spring elements of the switching device that are usually provided. The use of the apparatus according to the invention avoids this problem. In particular in conjunction with the previously discussed bimetal device, a bimetal controller with a switching behavior that is very accurate, and in particular can be accurately set, is thus obtained. 
     Further embodiments of the invention are provided by the subclaims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is described below on the basis of exemplary embodiments, which are explained in more detail by the accompanying drawings, in which: 
         FIG. 1  shows an isometric representation of an embodiment of the bimetal controller; 
         FIG. 2  shows a side view of the embodiment of the bimetal controller from  FIG. 1 ; 
         FIG. 3  shows the view of a detail of a bimetal device of the embodiment of the bimetal controller from  FIG. 1 ; 
         FIG. 4  shows a further embodiment of a bimetal device; 
         FIG. 5  shows an isometric representation of the embodiment of the bimetal controller according to  FIG. 1  with paternoster connection terminals; 
         FIG. 6  shows an isometric longitudinal section of the representation from  FIG. 5 ; and 
         FIG. 7  shows an isometric longitudinal section of the embodiment of the bimetal controller according to  FIG. 5  when integrated in a housing. 
     
    
    
     DETAILED DESCRIPTION 
     The same reference signs are used hereafter for components that are the same and components that act in the same way, superscripts sometimes being used for the purpose of distinction. 
       FIG. 1  shows an isometric representation of an embodiment of the bimetal controller according to the invention,  FIG. 2  shows a side view of this embodiment and  FIG. 3  shows a representation of a detail of a bimetal device  4 , such as that used in this bimetal controller  1 . 
     In the case of this embodiment, the bimetal device  4  has two bimetal elements  6 ,  8 , to be specific a first bimetal element  6  and an arcuate, second bimetal element  8 . The arcuate, second bimetal element is configured here at least partially in the form of a ¾ circle. These two bimetal elements  6 ,  8  are connected to each other at a contact region  14 , in particular here the first bimetal element  6  is arranged with its distal end  7  on the proximal end  9  of the arcuate, second bimetal element  8 . 
     The bimetal device  4  is actively connected by way of a switching element  3  to a switching device  2 , which establishes an electrical connection between two contact elements  16 ,  18 , that is to say allows a switching operation. An adjustment of the switching operation can be made by way of a setting element  20 , in that two switching contacts  17 ,  19  assigned to the contact elements  16 ,  18  are positioned in relation to each other. Depending on how this positioning is performed, the switching device  2  triggers the switching operation when there are small or greater movements of the bimetal device  4 . 
     The bimetal device  4  is restrained in a substantially flexurally rigid manner by a proximal end  5  of the first bimetal element  6  on a bearing block  22 . This bearing block, which consists of a number of isolating individual elements  23 , carries not only the bimetal device  4  but also the contact elements  16  and  18  and a retaining plate  24 , which allows the bimetal controller  1  to be fastened in a housing  40  (see  FIG. 7 ) and additionally carries the setting elements  20 . 
     The arcuate, second bimetal element  8  has at its distal end  11  a switching region  13 , by way of which it is actively connected to the switching device  2  by the switching element  3 . When there is a change in temperature, the switching region  13  moves on account of the resulting movement of the two bimetal elements  6 ,  8  toward the switching device  2 , the switching element  3  triggering the switching operation when there is a specific movement. 
     The structure of the switching device  2  can be seen in detail in  FIG. 2  in particular. It comprises the two contact elements  16  and  18 , which can be brought into electrically conducting connection with each other via the assigned contact elements  17  and  19  by an activation taking place by way of the switching element  3 . The contact element  17  is formed here as a spring element, and in particular as a beryllium-sprung spring element, so that the electrical conducting connection is opened again when there is a “retraction” of the switching element  3 . 
     In  FIGS. 1 and 2 , and in particular in  FIG. 3 , the different layer structures of the two bimetal elements  6 ,  8  of the bimetal device  4  can be seen. The first bimetal element  6  consists of two element layers  10 ,  12 , element layer  10  with the greater coefficient of thermal expansion .alpha..sub..DELTA.T10 being arranged on the underside  21 , as represented in the plane of the drawing, and the element layer  12  with the lower coefficient of thermal expansion .alpha..sub..DELTA.T12 being arranged on the upper side  23 . 
     The layer structure of the arcuate, second bimetal element  8  is formed oppositely thereto. This bimetal element  8  also consists of two element layers  10 ,  12 , the element layer  10  with the higher coefficient of thermal expansion .alpha..sub..DELTA.T10 being arranged on the upper side  23 , as represented in the plane of the drawing, and the element layer  12  with the lower coefficient of thermal expansion .alpha..sub..DELTA.T12 being arranged on the underside  21  in the contact region  14 . 
     The result of such an opposed arrangement of the two layer structures of the two bimetal elements  6 ,  8  is a very much stronger deflection (represented here in  FIG. 3  by the arrow  26 ), which in the case of the bimetal controller  1  represented here leads to a very much more accurate adjustability and more accurate switchability. 
     In  FIG. 3 , the movement of the bimetal device  4  or of the two bimetal elements  6 ,  8  when there is a specific change in temperature .DELTA.T is represented diagrammatically, the final position of the bimetal device  4  when there is a change in temperature .DELTA.T being represented by dashed lines. 
       FIG. 4  shows a further embodiment of the bimetal device  4 , here a plurality of first bimetal elements  6  and arcuate, second bimetal elements  8  being arranged alongside one another in series and here in particular in a meandering form. In this way, the switching travel  26  represented in  FIG. 3  when there is a change in temperature .DELTA.T can be increased almost at will, allowing unwanted movements, here for example the drift to the right of the switching region  13  depicted in  FIG. 3 , to be corrected. The bimetal elements  6 ,  8  represented here in  FIG. 4  also respectively have a layer structure, consisting of at least two element layers  10 ,  12 , such as that which has already been explained at length with reference to  FIG. 3 . 
     In  FIGS. 5 to 7 , the embodiment discussed above, according to  FIGS. 1 to 3 , is represented again in an isometric view ( FIG. 5 ) and in a longitudinal section ( FIG. 6 ). The embodiment of the bimetal controller  1  has been supplemented here by clamping devices  28 , and in particular by two paternoster terminals  30 , which allow easy connection of a conducting element  50  to the bimetal controller  1 . If in the case of the prior art the contact elements  16 ,  18  have usually been connected to further conducting elements  50  by way of a soldered connection, here the connection of the bimetal controller  1  or of the contact elements  16 ,  18  takes place by way of the paternoster terminals  30 . The advantage of this connecting technique is that no thermal energy is introduced into the contact elements  16  and  18 , and by way of these into the switching contacts  17 ,  19 , and in particular the switching contact  17  formed here as a beryllium-sprung spring, by a soldering or welding operation. This is so because it is specifically this introduction of heat that has led to deformations, and to a weakening of the restoring force of the switching contact  17  configured as a sprung-spring element, in the prior art. This artificial aging, which corresponded substantially to a thermal after-treatment, often led to a malfunction of the bimetal controllers  1 . 
     In principle, it should be noted that the use of this clamping technique by means of the paternoster terminals  30  for the connection of a conducting element to the contact elements  16 ,  18  is not restricted only to use in the case of the bimetal controller  1  according to the invention that is represented here. All components provided with contact elements or switching contacts, in particular with heat-sensitive contact elements or switching contacts, can be equipped correspondingly. 
     The clamping devices  28  represented in  FIGS. 5 to 7  for the electrically conducting connection of at least one conducting element  50  to at least one contact element  16 ,  18  of a switching device, and here of the bimetal controller  1 , that is mounted in a housing  40  has the following: 
     A clamping bolt  32  and a clamping bolt receptacle  34 , which together define a clamping space  36 , into which the conducting element  50  can be introduced, in particular from an outer side  43  of the housing  40 , and into which the contact element ( 16 ,  18 ) protrudes, in particular from an inner side  45  of the housing  40  (see  FIG. 7  in particular), the clamping bolt  32  being held in its axial direction, in particular in the housing  40 , and lying with a clamping continuation  33  against the contact element  16 ,  18  in an unconstrained manner, and a counter bearing region  35  of the clamping bolt receptacle  34  being able to be moved toward the clamping continuation  33  and the contact element  16 ,  18  lying on it while reducing the clamping space  36  and able to be fixed at least in one clamping position such that the conducting element  50  and the contact element  16 ,  18  are fixed with respect to each other in an electrically conducting manner, without a flexural loading being introduced into the contact element  16 ,  18 . The clamping device  28  according to the invention or the paternoster terminal  30  therefore has not only the advantage of easy connection of a conducting element to the contact elements  16 ,  18 , in particular without any introduction of heat, but also the advantage of an unconstrained connection, so that no flexural loadings are introduced into the contact elements  16 ,  18  and the assigned switching contacts  17 ,  19 . 
     Preferably, the clamping bolt receptacle  34  is formed as a clamping bolt shoe, which at least partially encloses the clamping space  36 , the counter bearing region  35  being formed on the inner bottom wall thereof, facing the clamping continuation  33 . The clamping bolt receptacle  34  is in this case preferably mounted movably in the axial direction of the clamping bolt  32  on the clamping bolt. As represented here, the clamping bolt  32  is preferably provided with a threaded region, which is in threaded engagement with a thread receiving region of the clamping bolt receptacle  34  in such a way that the counter bearing region  35  of the clamping bolt receptacle  34  can be moved toward the contact element  16 ,  18  and away from it by a rotation of the clamping bolt  32  toward the clamping bolt continuation  33  and the contact element  16 ,  18  lying against it. 
     As can be seen in  FIGS. 5 and 6 , the clamping bolt receptacle  34  is preferably formed from a metal strip  42  folded over a number of times. This allows inexpensive production, with at the same time good stability and sufficient material for the forming of a thread receiving region. 
     The clamping bolt receptacle  34  preferably has on its lower bottom region a covering element  44 , which serves during the connection of a conducting element as a guide for it. The covering element  44  in this case preferably extends axially parallel to the clamping bolt  32  in such a way that, when there is a reduction in the clamping space  36 , that is to say brought about here by a rotation of the clamping bolt  32 , it successively covers a receiving opening  48  in the housing  40 . This prevents inappropriate introduction of the conducting element.