Abstract:
An installation switch has an insulating housing and a terminal connecting arrangement for clamping a connecting conductor having an annular terminal shoe. The terminal connecting arrangement includes a terminal socket having an interior disposed between an insertion opening for receiving the terminal shoe and an access opening and a terminal screw having a screw head and a screw shank disposed in the interior of the terminal socket, the screw being actuatable in a longitudinal direction within the interior of the terminal socket between an open state and a clamped state. The arrangement further includes a connection plate having a screw hole with interior threads for threadably engaging the terminal screw when in the clamped state and a retaining device preventing the terminal screw from being removed from the terminal socket when in the open state.

Description:
CROSS REFERENCE TO PRIOR APPLICATIONS 
     This is a continuation of U.S. application Ser. No. 12/194,735, filed Aug. 20, 2008 and issued on Apr. 27, 2010 as U.S. Pat. No. 7,704,105, which claims priority to German Patent Application No, DE 10 2007 039 709.9 filed Aug. 22, 2007. The entire disclosure of both applications is incorporated by reference herein. 
    
    
     The invention relates to an installation switch device having an insulating material housing and a connection terminal arrangement for clamping a connection conductor having an annular terminal shoe. 
     BACKGROUND 
     In conventional installation switch devices, the connecting conductor is screwed to a connection plate, which includes a screw hole and is mounted so as to be stationary in the interior of the device, by means of a terminal screw including a screw head and a screw shank. The connecting terminal arrangement is located in a terminal socket including an opening for inserting the connecting conductor and an opening providing access to the screw head for actuating the terminal screw with a tool, for example a screwdriver. When the connecting conductor is clamped, the screw shank penetrates the annular terminal shoe and is in threaded engagement with the screw hole. 
     Conventional installation switch devices are, for example, circuit breakers, motor circuit breakers or fault-current circuit breakers, the connecting terminal arrangement of which is formed specifically to connect a connecting conductor to an annular terminal shoe, in particular a terminal shoe with a closed ring. A hole through which the terminal screw is guided upon clamping is thus provided in the annular terminal shoe. Terminal screws which include a flat head and a long shank and which are screwed into a connection plate in the interior of the switch device housing are used in the known conventional installation switch devices. In this way, the terminal shoe is clamped between the screw head and the connection plate, optionally with an additional thrust piece inserted therebetween. Attached to the connection plate are further conductors which lead into the interior of the device and carry the current path through the installation switch device between an input terminal and an output terminal. 
     A connecting conductor having an annular terminal shoe cannot be clamped between the screw head and the connection plate unless the terminal screw has been completely unscrewed and lifted off the connection plate beforehand in such a way that a passage is formed at the insertion opening for the closed terminal shoe. During this process, the terminal screw may fall out and be lost through the access opening. Inserting the terminal screw after the connecting conductor including the annular clamping shoe has been introduced requires skill from the engineer, since, due to the long shank and the flat head of the conventionally-used terminal screws, it is easy for said screws to tilt in the terminal socket between the access opening and the thread in the connection plate in such a way that the screw shank does not come into threaded engagement with the screw thread of the connection plate. 
     An object of the present invention is therefore to develop a conventional installation switch device in such a way that the terminal screw cannot be lost when connecting a connecting conductor with an annular terminal shoe and it is easier to screw in the terminal screw. 
     SUMMARY 
     The present invention is directed to a screw head coupled to the insulating material housing in the interior of the terminal socket so as to be displaceable in the longitudinal direction of movement of the terminal screw in such a way that when the terminal screw is moved between an open position of the screw, in which there is a gap for inserting the terminal shoe of the connecting conductor between the free end of the screw shank and the connection plate, and a set-down position of the screw, in which the screw shank is just beginning to be engaged in the thread of the screw hole, the axis of movement of the screw shank remains aligned with the axis of the screw hole. The terminal socket further includes a device for retaining the terminal screw, so removal of the terminal screw from the terminal socket is prevented in the open position of the screw. The retaining device provided according to the invention prevents the terminal screw from being lost. The process of screwing in the terminal screw is simplified by the movable coupling to be provided according to the invention between the screw head and the insulating material housing in the interior of the terminal socket, since this prevents the screw shank from tilting. 
     According to an embodiment of the present invention, the screw head includes, for the movable connection thereof, first guide means which are provided on the screw head and extend in the direction of the longitudinal movement of the screw, and the insulating material housing includes, in the region of the terminal socket, second guide means provided in the terminal socket, which guide means cooperate to guide the movement of the terminal screw in the longitudinal direction when the screw is inserted in the terminal socket. The first guide means provided on the screw head may thus be a component of the screw head. 
     An embodiment of the present invention includes a configuration where the screw head is a cylinder which extends longitudinally in the longitudinal direction of movement of the screw, the first guide means being formed by the casing of this cylinder. Another embodiment includes a configuration where the terminal socket includes a wall which extends in the longitudinal direction of movement of the terminal screw and encompasses the screw head in a guiding manner. A terminal screw including a screw head which is formed as a longitudinally-extended cylinder is encompassed by the wall along its cylinder casing and is thus guided. Tilting of the terminal screw is thus prevented by the fact that the casing surface of the cylindrical screw head displaceably abuts the guiding wall. 
     An embodiment in which the guiding wall is formed by the inner wall of a cylindrical guide channel, which is located in the terminal socket which encompasses the screw head, is particularly advantageous. 
     The retaining device is advantageously an undercut which extends into the terminal socket in the region of the access opening. An undercut of this type can be simply produced together with the housing shells when forming the housing by injection moulding. The terminal screw is then to be introduced into the terminal socket before the housing is closed. 
     Another embodiment of the present invention includes a configuration where the screw head and the wall are engaged by means of a thread in the open position of the terminal screw in such a way that, when the terminal screw is in the open position, it may thus be held displaceably. In this way, the terminal screw may be positioned in a defined manner when it is in the open position. The threaded engagement according to the invention between the terminal screw and the wall also prevents loss of the screw. 
     The threaded engagement between the screw head and the wall begins where the threaded engagement between the screw shank and the screw hole ends. When the terminal screw is screwed by actuation with a tool, out of its clamping position, in which it is screwed in the connection thread to the connection plate, the screw head of said terminal screw moves upwards in the direction of the longitudinal displacement thereof towards the access opening. The threaded engagement between the shank of the terminal screw and the screw thread of the connection plate comes to an end when the set-down position has been reached. In a configuration according to the invention in which the screw head includes an external thread, in conjunction with an arrangement according to the invention in which an internal thread corresponding therewith is provided in the wall, the threaded engagement of the screw head and wall begins in the set-down position in such a way that when the screwdriver actuates the terminal screw further, the terminal screw is screwed out into the wall, as it were, via the internal thread. It is therefore no longer possible to lose the screw and it is held in the open position by the thread without the engineer having to hold it from outside, and this facilitates insertion of the annular terminal shoe. 
     When screwing the terminal screw out of the open position, the screw shank is securely guided by the thread in the wall towards the screw thread in the connection plate. The threaded engagement between the screw head and the wall ends, and the threaded engagement between the screw shank and the screw thread in the connection plate begins when the screw reaches the set-down position. The terminal screw is then screwed into the screw thread in the connection plate by continuous actuation of the tool until the clamping position is reached once again. 
     The screw head is particularly advantageously provided with an external thread and the wall with an internal thread. 
     With regard to the connection plate, an embodiment of the present invention provides that the connection plate is a leg of a U-shaped busbar, which is mounted so as to be stationary in the housing of the installation switch device and of which the second leg, which is opposite the connection plate, is connected therewith via a web. 
     A conductor rail may advantageously be integrally formed on the free end of the connection plate to connect further conductors in the interior of the installation switch device. 
     In yet another embodiment according to the present invention, the web may be contacted from outside the housing for testing and calibration purposes. Establishing contact for testing purposes is required, for example, when hot testing the thermal trip of a circuit breaker. In this process, a defined level of excess current, which may be approximately 1.5 times the rated current, is connected to the device via the web by means of a testing terminal using appropriate test equipment, and whether or not the thermal trip in the interior is triggered in the required disconnection time is tested. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention, as well as further advantageous configurations and improvements of the invention, will be explained in greater detail and described with reference to the drawings in which two embodiments of the invention are shown. 
       In the drawings: 
         FIG. 1  shows a first embodiment of the present invention, in which the terminal screw is in the set-down position; 
         FIG. 2  shows the embodiment from  FIG. 1 , the terminal screw being in the open position; 
         FIG. 3  shows the embodiment from  FIG. 1 , the terminal screw being in the clamped position; and 
         FIG. 4  shows a second embodiment of the present invention, in which the screw head of the terminal screw is not provided with a thread. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a schematic partial cross-sectional view of an installation switch device  1  which includes an insulating material housing  2 . The installation switch device  1  is, for example, a circuit breaker. The insulating material housing thereof includes a leading and trailing front face  3 ,  4 , a leading and trailing side face  5 ,  6  and a fastening face  7 . Provided on the fastening face  7  is a fixed tab  8  which cooperates with a further, generally displaceable tab (not shown) when clamping the circuit breaker  1  to a support rail. 
     In the region of the trailing side face  6 , a terminal socket  10 , in which a connecting terminal arrangement  11  is accommodated, is provided in the housing  2 . The terminal socket  10  can be accessed from the trailing side face  6  through an insertion opening  27  for a connecting conductor  12  and can be accessed from the trailing front face  4  through an access opening  28  for an actuation tool, for example a screwdriver  22 . 
     Together with the connecting terminal arrangement  11 , the connecting conductor  12 , which includes an annular terminal shoe  14  having a central opening  13 , is screwed to a connection plate  16  by a terminal screw  15 . 
     The terminal screw  15  includes a screw head  17 , which is formed as a longitudinally-extended cylinder, and a shank  18 . The shank  18  is approximately as long as the screw head  17 . The shank  18  has an external thread  19 . Provided on the free end face  20  of the screw head  17  is a slot  21  for receiving the actuation tool, such as a screwdriver  22 . 
     The connection plate  16  includes a screw hole  23  with an internal thread  25 . The connection plate is aligned so as to be approximately parallel with the trailing front face  4 . The connection plate  16  forms one leg of a U-shaped busbar  30  which is mounted so as to be stationary in the housing  2  of the installation switch device  1  by web-like housing projections  32 . 
     The second leg  33  of the U-shaped busbar  30  is connected to the connection plate  16  via a web  35 . The second leg  33  includes an opening  34  which faces the screw hole  23  and has a diameter of at least the same size as that of said screw hole. 
     The busbar  30  is arranged in the housing in such a way that the web  35  is located in the vicinity of the trailing side face  6  and may be accessed from outside via a testing opening  36  for establishing contact by means of a test prod for testing or calibration purposes. 
     Integrally formed on the free end of the connection plate  16  is a conductor rail  37 , to which further conductors leading into the interior of the installation switch device  1  may be connected. However these conductors are not shown in the diagram, and neither are all of the further components and modules required to operate an installation switch device, such as a thermal and electromagnetic trip, a switch mechanism, a switch lever with a contact point, an electric arc quenching arrangement, etc. 
     The terminal screw  15  is guided in the terminal socket  10  in an approximately cylindrical guide channel  24 . The guide channel  24  extends approximately parallel to the trailing side face  6  in such a way that the terminal screw  15  is guided vertically through said channel to the screw hole  23  in the connection plate  16 . The inner diameter of the guide channel  24  thus corresponds to the outer diameter of the screw head  17  in such a way that the screw head  17  is guided in a sliding manner in the guide channel  24  and is coupled to the insulating material housing so as to be able to move to some extent in the interior of the terminal socket  10 . 
     In  FIG. 1 , the terminal screw  15  is shown in its set-down position, that is to say, the free end of the screw shank  18  is positioned directly on the internal thread  25  of the screw hole  23 . The annular terminal shoe  14  cannot be inserted into the terminal socket  10  in this position, since the terminal shoe is blocked by the screw shank  18 . Before the terminal shoe is inserted, the terminal screw  15  must be raised from the connection plate  16  in the direction of the arrow P to such an extent that a gap corresponding to at least the depth of the terminal shoe  14  is formed between the free end of the shank  18  and the connection plate  16  so the terminal shoe  14  can then be pushed through the insertion opening  27  until it strikes the conductor rail  37  and the opening  13  of the terminal shoe rests directly above the screw hole  23 . This position is shown in  FIG. 2 . 
     The conductor rail  37  thus has a second function as an insertion stop for the terminal shoe  14  and prevents the terminal shoe from being inserted too far, and this further facilitates the installation of the connecting conductor  12 . 
     The upper portion of the screw head  17  has an external thread  38 . An internal thread  39  is provided on the inner wall of the guide channel  24 . This internal thread begins where the outer thread  38  on the screw head  17  ends in the set-down position according to  FIG. 1 . If the terminal screw  15 , in the set-down position shown in  FIG. 1 , is then rotated further in the direction of the arrow R by means of the screw driver  22 , the screw head  17  and the inner wall of the guide channel  24  become engaged by means of the thread and, when the terminal screw  15  is rotated further, said screw is moved upwards via the internal thread  39  into the open position and is held in said position when the rotational movement is discontinued. 
     After the connecting conductor  12  including the terminal shoe  14  has been inserted (see  FIG. 2 ) the terminal screw  15  may be moved downwards again by being rotated in the internal thread  39 . In this process, the terminal screw passes through the opening  13  of the terminal shoe  14  and thus retains it. 
     When the set-down position has been reached, the threaded engagement of the external thread  38  of the screw head  17  and the internal thread  39  of the inner wall of the guide channel  24  ends and, when the terminal screw  15  is rotated further with a slight degree of downward pressure, the threaded engagement between the external thread  19  of the shank  18  and the internal thread  25  of the screw hole  23  begins. When the terminal screw  15  is rotated further, said screw is pulled downwards further into the screw hole  23  as a result of the threaded engagement until the terminal shoe  14  is clamped firmly between the screw head  17  and the connection plate  16 . This position is shown in  FIG. 3 . In this way, a secure screw connection with a good degree of surface contact can be produced. 
     If the shank  18  were somewhat longer, it could be accommodated in the opening  34  in the second leg  33 . In a variant (not shown), the opening  33  could also be provided with an internal thread and thus optionally also be engaged with the shank  18  by means of the thread and therefore contribute to the clamping action of the screw connection. 
       FIG. 4  shows a further embodiment of the present invention. All like components or modules or components or modules with like functions are denoted in  FIG. 4  with the reference numerals as in  FIGS. 1 to 3 , preceded by “ 10 ”. 
     In this embodiment there is no external thread on the screw head and no internal thread on the inner surface of the guide channel  1024 . Displaceable coupling between the screw head and the guide channel  1024  is achieved by the fact that the casing surface of the cylindrical screw head slides along the casing surface of the guide channel  1024  which is also formed so as to be cylindrical. This reliably prevents tilting of the terminal screw  1015  in the guide channel  1024  and ensures that the axis of the terminal screw  1015  is always aligned with the axis of the screw hole  1023  in such a way that when the terminal screw  1015  is lowered in the guide channel  1024  from the open position into the set-down position, the shank  1018  slides reliably into a position in which it can become engaged by means of the internal thread in the screw hole  1023 . 
     An undercut  1040  provided in the guide channel  1024  prevents the terminal screw  1015  from being lost. The undercut  1040  may be formed as an annular elevation or a narrowing of the diameter of the guide channel  1024  in the upward direction. The cross-sectional area, reduced by the undercut  1040 , of the guide channel  1024  is still large enough to allow a screw driver  1022  to pass therethrough in order to actuate the terminal screw  1015 , but is smaller than the cross-sectional area of the screw head so that said head is held captive to some extent in the guide channel  1024 . 
     The terminal screw  1015  may in this case be raised from the set-down position to the open position, by, for example, the magnetic retentive force of the terminal screw  1025  to a magnetic screwdriver  1022 . 
     In a further embodiment according to the present invention, the free end of the shank  1018  is slightly conically tapered, which is indicted by the bevel  1042 . On the other hand, annular terminal shoes  1014  are generally very thin, and the depth of the ring of a terminal shoe  1014  of this type is often less than 1 mm. In some circumstances, it is therefore sufficient to press a thin terminal shoe  1014  of this type firmly against the free end of the shank  1018  in the set-down position in order to push the terminal screw  1015 , via the bevel  1042 , upwards far enough for the terminal shoe  1014  to slide into its connection position on the connection plate  1016 . In this case, installation is further simplified since the terminal screw  1015  does not have to be raised separately manually and there is no need to bring it into a specific open position before being able to insert the terminal shoe  1014 . 
     The undercut and the bevel are also present in the embodiment shown in  FIG. 1 to 3  and are denoted with the reference numerals  40  and  42  respectively in said figures. However, the particular functional advantages thereof, such as holding the terminal screw “captive” and automatically pushing the terminal screw upwards when inserting the connecting conductor, play a lesser role in  FIG. 1 to 3 , since both functions are substantially covered by the internal thread on the inner side of the guide channel in cooperation with the external thread on the outer casing surface of the screw head. 
     
       
         
               
             
               
               
             
           
               
                   
               
               
                 List of reference numerals 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 1, 101 
                 Installation switch device 
               
               
                 2, 102 
                 Insulating material housing 
               
               
                 3, 103 
                 Leading front face 
               
               
                 4, 104 
                 Trailing front face 
               
               
                 5, 105 
                 Leading side face 
               
               
                 6, 106 
                 Trailing side face 
               
               
                 7, 107 
                 Fastening face 
               
               
                 8, 108 
                 Fixed tab 
               
               
                 10, 1010 
                 Terminal socket 
               
               
                 11, 1011 
                 Connecting terminal arrangement 
               
               
                 12, 1012 
                 Connecting strip 
               
               
                 13, 1013 
                 Opening in the terminal shoe 
               
               
                 14, 1014 
                 Annular terminal shoe 
               
               
                 15, 1015 
                 Terminal screw 
               
               
                 16, 1016 
                 Connection plate 
               
               
                  17, 
                 Screw head 
               
               
                 18, 1018 
                 Shank 
               
               
                 19, 1019 
                 External thread of the shank 
               
               
                 20 
                 End face of the screw head 
               
               
                 21 
                 Slot 
               
               
                 22, 1022 
                 Screwdriver 
               
               
                 23, 1023 
                 Screw hole in the connection plate 
               
               
                 24, 1024 
                 Guide channel in the terminal socket 
               
               
                 25 
                 Internal thread of the screw hole 
               
               
                 27, 1027 
                 Insertion opening 
               
               
                 28, 1028 
                 Access opening 
               
               
                 30, 1030 
                 Busbar 
               
               
                 32, 1032 
                 Web-like projections 
               
               
                 33, 1033 
                 Second leg 
               
               
                 34, 1034 
                 Opening in second leg 
               
               
                 35 
                 Web 
               
               
                 36, 1036 
                 Testing opening 
               
               
                 37, 1027 
                 Conductor rail 
               
               
                 38 
                 External thread of the screw head 
               
               
                 39 
                 Internal thread in the guide channel 
               
               
                 40, 1040 
                 Undercut 
               
               
                 42, 1042 
                 Bevels on the end of the shank