Abstract:
The invention relates to an electrical device having a switching unit, which is provided for switching a power supply of a consumer unit, and a control unit for controlling the consumer unit. According to the invention, the electrical device includes a bridging unit provided for supplying power to the control unit when the power supply is switched off by the switching unit.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a 35 USC 371 application of PCT/EP2008/064852 filed on Nov. 3, 2008. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention is based on an electrical appliance. 
     2. Description of the Prior Art 
     An electrical appliance equipped with a switch unit and a control unit is already known. The switch unit is provided for switching a power supply to a consumer unit and the control unit is provided for controlling the consumer unit. 
     ADVANTAGES AND SUMMARY OF THE INVENTION 
     The invention is based on an electrical appliance with a switch unit provided for switching a power supply to a consumer unit and a control unit provided for controlling the consumer unit. 
     According to one proposal, the electrical appliance has a bridge unit provided to supply current to the control unit when the power supply is switched off by the switch unit. In this context, the term “provided” is understood to mean specially equipped and/or specially embodied and/or specially programmed. In addition, a “control unit” should be understood in particular to be a unit that is composed of a computing unit, an evaluating unit, a control unit, and/or a regulating unit; a control unit can be composed of a processor alone or in particular, can be composed of a processor accompanied by additional electronic components such as memory devices and/or electronic components such as a voltage stabilizing capacitor. Preferably, the control unit has a microcontroller. Also in this context, a “switch unit” should in particular be understood to be a unit that makes or breaks an electrically conductive connection between two components and/or contacts and has at least one switch element, in particular a mechanical switch element. Preferably, the present invention is used in electrical appliances equipped with a bipolar switch unit. Basically, however, it is also conceivable for them to be equipped with a monopolar switch unit. In this context, a “bridge unit” should in particular be understood to be a unit that uses a conductive connection to bridge over an electrical connection that has been broken by a switch unit. The bridge unit can be constituted in a structurally simple way by a power supply line and/or in a particularly advantageous way by additional components and/or units that perform additional functions such as changing a power-to-heat ratio. The embodiment according to the invention can be used to advantageously supply a voltage to electrical appliance electronics or to individual units and/or components such as the control unit, of the electrical appliance electronics, thus avoiding an undesirable warm-up time of the electrical appliance electronics when starting or switching on the consumer unit. In addition, the increased output of the electrical appliance can be achieved at the beginning of a work process and/or other auxiliary functions such as protective functions in the electrical appliance electronics can be achieved in a structurally simple fashion. The present invention has the particular advantage of being suitable for use in an electrical appliance that is embodied in the form of a power tool, in particular a hand-held power tool such as an angle grinder. 
     According to another proposal, the bridge unit is a voltage conversion unit. In this context, a “voltage conversion unit” should in particular be understood to be a unit that is provided for converting or changing an electrical current with an input voltage into an electrical current with an output voltage that differs from the input voltage. Preferably, the voltage conversion unit converts the input voltage to a lower output voltage that permits a low-energy stand-by mode, particularly of the control unit. 
     If the voltage conversion unit has a resistance unit, then a voltage can be converted in a structurally simple way. In particular, the resistance unit can be integrated into conventionally designed switching electronics of the electrical appliance in a particularly inexpensive way and it is thus possible for conventional, standard switching components to be inexpensively used in connection with the resistance unit. In this context, a “resistance unit” should in particular be understood to be a unit with at least one resistance element, in particular an ohmic resistance. Preferably, the resistance unit is constituted by a high-ohm resistance unit so that an advantageously low, inexpensive operating voltage can be implemented in the stand-by mode. Basically, however, it is also conceivable, instead of the resistance unit, for the voltage conversion unit to be equipped with other electrical components and/or units such as a capacitor, an induction coil, and/or other components and/or units deemed suitable by the person skilled in the art. 
     A structurally simple, component-saving conversion of the voltage, in particular a conversion of an input voltage to a considerably lower output voltage, can be achieved if the resistance unit has at least one high-ohm resistance element. In this context, a “high-ohm resistance element” should in particular be understood to be an element that has a resistance value in the range from approx. 5 kΩ to 20 kΩ. The resistance element can be constituted by a capacitor, an induction coil, and/or particularly preferably, a resistance. 
     According to another proposal, the electrical appliance has at least one contact point that connects the bridge unit conductively to an incoming power supply line. In this context, an “incoming power supply line” should in particular be understood to be a power supply line that is connected to a power outlet and is provided to supply current to the electrical appliance and/or an electrically conductive contact with an energy storage unit such as a rechargeable battery. The bridge unit can thus be situated before the switch unit along a current flow direction and conductively connected to the power supply line, thus achieving an advantageous permanent current supply to the control unit by means of the bridge unit when there is a current-carrying connection of the power supply line to an electrical power grid. Alternatively to this, the contact point can also be provided in the switch unit; in this case, the contact point is advantageously situated before a switch point of the switch unit along a current flow direction. 
     An electrically conductive contact between the bridge unit and the contact point can be achieved in a structurally simple fashion if the contact point and the bridge unit each have a respective contact element. Preferably, the contact point and the bridge unit each have two contact elements, permitting the bridge unit to bridge over a voltage supply in an electrical appliance equipped with a bipolar switch unit. If the electrical appliance has only a monopolar switch unit, then it is sufficient to provide the contact point and the bridge unit with only one contact element each. It is particularly advantageous for the contact elements to each be composed of a contact terminal, thus permitting achievement of a simple plug connection between the contact point and the bridge unit. 
     According to another proposed embodiment of the invention, the electrical appliance has an additional component that at least partially forms an assembly unit together with the bridge unit. In this context, an “assembly unit” should in particular be understood to be a unit that is installed in one piece during an assembly of the electrical appliance. This makes it advantageously possible to achieve savings with regard to additional components, space, and assembly complexity of the electrical appliance, and also makes it possible to achieve a particularly compact arrangement of the bridge unit. 
     According to another proposal, the assembly unit has at least one housing in which the additional component and the bridge unit are at least partially accommodated, making it possible to achieve a particularly compact, especially protected arrangement of the bridge unit and/or the additional component. 
     If the assembly unit also has a fixing material, then it is possible to achieve a particularly stable arrangement inside the assembly unit. In a particularly advantageous embodiment, the fixing material is composed of a casting compound such as Macromelt. Preferably, the fixing material or casting compound is dispensed into the housing of the assembly unit during a production process after the component and at least one component of the bridge unit have been placed therein and then hardens so that the components are situated in a particularly stable fashion and in fixed positions in relation to one another inside the assembly unit. 
     If the additional component is composed of a capacitor, in particular a decoupling capacitor, then at least two functional elements, which must be provided in the vicinity of the switch unit, can advantageously be accommodated in a particularly compact fashion inside the electrical appliance. 
     In an advantageous modification of the invention, the assembly unit has at least three contact elements, making it advantageously possible to achieve savings with regard to additional components, in particular additional lines and/or cable, and the assembly unit can be connected to via a minimal number of contacts and can be connected in an electrically conductive fashion to additional components. In this connection, it is particularly advantageous that a contact element is provided for connecting the bridge unit to an incoming power supply line in an electrically conductive. Preferably, the two other contact elements constitute connecting elements for the additional component. 
     According to another proposal, the assembly unit has an electrically conductive connection that is provided to connect the bridge unit to a connecting element of the additional component. This eliminates the need for providing additional contact elements, e.g. for the bridge unit, and enables a compact embodiment of the electrical appliance electronics. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS The invention is described in detail below in conjunction with the drawings, in which: 
         FIG. 1  is a schematic depiction of an electrical appliance embodied in the form of a hand-held power tool; 
         FIG. 2  is a circuit diagram of the electrical appliance electronics of the electrical appliance, equipped with a bridge unit; 
         FIG. 3  is a schematic depiction of an assembly unit of the electrical appliance, equipped with a bridge unit and an additional component; 
         FIG. 4  is a schematic depiction of an embodiment of the bridge unit alternative to the one in  FIG. 3 , equipped with an additional component; and 
         FIG. 5  is a schematic depiction of the bridge unit from  FIG. 4 , in an arrangement together with the additional component inside the electrical appliance. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  schematically depicts an electrical appliance  10  embodied in the form of a hand-held power tool  66 . The hand-held power tool  66  is embodied in the form of an angle grinder, which has a disk-shaped tool  68  that can be driven to rotate. The hand-held power tool  66  has a handle  74  at its end  72  remote from the tool  68  in a longitudinal direction  70 . In a region of the handle  74 , the hand-held power tool  66  also has a power cord  76  for connecting the hand-held power tool  66  to an electrical power grid. The power cord  76  supplies electrical energy to a set of electrical appliance electronics  78  and a motor unit  80 . 
       FIG. 2  is a more detailed depiction of the electrical appliance electronics  78  of the hand-held power tool  66 . The electrical appliance electronics  78  include a switch unit  12  that is embodied in the form of a bipolar switch unit  12 . The switch unit  12 , which has two switch contacts  82 ,  84 , switches a current supply for a consumer unit  14  embodied in the form of the motor unit  80 . In addition, the hand-held power tool  66  and the electrical appliance electronics  78  include an internal power supply line  86  that is situated between the motor unit  80  and the switch unit  12  and between the switch unit  12  and the power cord  76  and is provided to produce an electrically conductive connection between the power cord  76  and the motor unit  80  when the switch contacts  82 ,  84  of the switch unit  12  are closed. The power cord  76  is connected in an electrically conductive fashion to the internal power supply line  86  at a contact point. 
     In addition, the electrical appliance electronics  78  include a control unit  16 , which is provided to control the motor unit  80  of the electrical appliance  10 , and has a capacitor  54  embodied in the form of a decoupling capacitor  88 , which reduces a transmission of interfering frequencies to the power grid during operation of the motor unit  80 . For this purpose, the control unit  16  has a microcontroller  90 , a voltage stabilizing unit  92  with a voltage stabilizing capacitor  94 , and a semiconductor-based breaking element  96  that is connected between the microcontroller  90  and the motor unit  80 . The semiconductor-based breaking element  96  in this case can be embodied in the form of a bidirectional thyristor triode and/or other elements deemed suitable by the person skilled in the art. Basically, it is also always conceivable, in an alternative embodiment of the electrical appliance electronics  78 , to use an embodiment of the control unit  16  that differs from the variant of the control unit  16  described above and shown in  FIG. 2 . The electrical appliance electronics  78  also have a bridge unit  18  that is provided for supplying current to the control unit  16  if the current supply is switched off by the switch unit  12 . In this case, the power cord  76  provides an electrically conductive connection between the electrical appliance  10  and the power grid and, because of a switching position of the switch contacts  82 ,  84 , the motor unit  80  is in a switched-off operating state. The bridge unit  18  has a voltage conversion unit  20  that is provided to convert a high incoming grid voltage of the power grid into a low stand-by voltage for a stand-by mode of the control unit  16 . For this purpose, the voltage conversion unit  20  has a resistance unit  22  equipped with a resistance element  24 . The resistance element  24  is composed of a high-ohm resistance element  24  and has a resistance value of approx. 10 kΩ. 
     The high-ohm resistance element  24  bridges over a switch contact  82  of the switch unit  12 . For bridging over the other switch contact  84 , the bridge unit  18  has a continuous line element  98  that is of one piece with the internal power supply line  86 . Basically, in lieu of the continuous line element  98 , it is also conceivable to use an additional resistance element and/or another electrical component deemed suitable by the person skilled in the art such as an induction coil and/or a capacitor, etc. 
     At the contact point  26  of the electrical appliance  10  or the electrical appliance electronics  78 , the bridge unit  18  is connected in an electrically conductive fashion to an incoming power supply line  28  of the power cord  76 . For this purpose, the contact point  26  and the bridge unit  18  each have two respective contact elements  30 ,  32 , and  34 ,  36 , that are embodied in the form of a contact terminal  38 ,  40 ,  42  (see  FIGS. 3 through 5 ). The contact point  26  in this case is composed of two angle contacts  100 ,  102  that respectively connect the incoming and outgoing power supply lines  28 ,  104  of the power cord  76  to two contact elements  30 ,  32  of the bridge unit  18  in an electrically conductive fashion. In addition, the contact elements  34 ,  36  or the angle contacts  100 ,  102  connect the internal power supply line  86  and the switch contacts  82 ,  84  to the power cord  76 . 
       FIG. 3  schematically depicts a subregion of the bridge unit  18  equipped with the resistance unit  22 . The high-ohm resistance element  24  comprises an assembly unit  48  together with another component  46  that is constituted by the decoupling capacitor  88 . For this purpose, the assembly unit  48  has a housing  50  in which are situated the high-ohm resistance element  24  and the decoupling capacitor  88  embodied in the form of a capacitor winding. To fix the decoupling capacitor  88  and the high-ohm resistance element  24  together inside the housing  50  of the assembly unit  48 , the assembly unit has a fixing material  52  that is embodied in the form of a casting compound such as Macromelt. The casting compound fixes the decoupling capacitor  88  and the high-ohm resistance element  24  in place inside the assembly unit  48 . 
     The assembly unit  48  also has three contact elements  30 ,  56 ,  58 ; a contact element  30  is constituted by one of the contact terminals  38  of the bridge unit  18 . The other two contact elements  56 ,  58  are constituted by connecting elements  60 ,  62  for the decoupling capacitor  88 , which are embodied in the form of connecting pins. During an assembly procedure, the connecting elements  60 ,  62  can be used to insert the assembly unit  48  by means of a simple insertion procedure into contact elements of the electrical appliance electronics  78  and/or of the electrical appliance  10  that correspond to the connecting elements  60 ,  62  and are not shown in detail here (analogous to  FIG. 4 ). In addition, the assembly unit  48  has an electrically conductive connection  64  that is provided to connect the high-ohm resistance element  24  to one of the connecting elements  60  of the decoupling capacitor  88  and the assembly unit  48  is thus provided with a minimum number of contact elements  30 ,  56 ,  58 . 
     The housing of the assembly unit  48  also has a respective locking element  116  embodied in the form of a knob situated on opposite sides  110 ,  112 , on each of the outward-facing surfaces  114 . The locking elements  116 , in cooperation with the contact terminal  38  and the connecting elements  60 ,  62 , permit the assembly unit  48  to be installed in a structurally simple, captive fashion inside the electrical appliance  10  during an assembly process and removed in a structurally simple fashion if an unwanted defect occurs. 
       FIGS. 4 and 5  show an arrangement of a decoupling capacitor  88  together with a high-ohm resistance element  88  of a bridge unit  18 . The high-ohm resistance element  24  in this case is situated between two line segments  106 ,  108  of an internal power supply line  86 . A connection between the high-ohm resistance element  24  and the decoupling capacitor  88  in this case is analogous to the description of  FIG. 3 . In addition, the resistance element  24 , along with the decoupling capacitor  88 , is connected to the internal power supply line  86  in a fashion analogous to the description of  FIGS. 2 and 3 . 
     Alternative to the embodiments of the invention shown in  FIGS. 3 through 5 , the bridge unit  18  and the resistance unit  22  with the high-ohm resistance element  24  can also be situated inside the electrical appliance electronics  78 , independent of or separate from an embodiment or arrangement of the decoupling capacitor  88 . For this purpose, only the bridge unit  18  or resistance unit  22  would have to have an additional contact point for contacting with the internal power supply line  86  inside the electrical appliance electronics  78 . 
       FIG. 5  shows a partial detail of the electrical appliance  10  in addition to an arrangement of the decoupling capacitor  88 , together with a resistance unit  22  in a region of a switch unit  12 . A connection between the contact element  30  of the bridge unit  18 , which contact is embodied in the form of a contact terminal  38 , and a contact terminal  40  of the contact point  26  is produced by means of a simple plug connection of the two contact terminals  38 ,  40 . The contact terminals  40 ,  42  in this case are embodied as U-shaped; only one leg of the U-shaped contact terminals  40 ,  42  is visible in  FIG. 5 . The legs of the U-shaped contact terminals  40 ,  42  are each connected to a housing  124  of the electrical appliance  10  at the contact point  26  by means of a respective screw  122 . One leg of the U-shaped contact terminals  40 ,  42 , which is not visible in  FIG. 5 , is provided to produce an electrical contact with power supply lines  28 ,  104  of a power cord  76 . For this purpose, the power supply lines  28 ,  104  are fixed in place in a clamp, not shown in detail, such as a strip connector, of a conventional standard switch, together with the non-visible legs of the U-shaped contact elements  118 ,  120 . The electrical appliance  10  also has two additional contact elements  118 ,  120  into which the connecting elements  60 ,  62  of the decoupling capacitor are inserted; these additional contact elements produce an electrically conductive contact with the electrical appliance electronics  78  and the internal power supply line  86 . 
     Alternative to the embodiments in  FIGS. 3 through 5 , it is also conceivable for the contact elements  30 ,  32  of the bridge unit  18  to be embodied in the form of a braid and for this to be fastened to a contact screw of the contact point  26  and connected to the power supply lines  28 ,  104  of the power cord  76  in an electrically conductive fashion. 
     The foregoing relates to the preferred exemplary embodiments of the invention, it being understood that other variants and embodiments thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.