Abstract:
A reconfigurable contact block usable for at least DIN rail and panel mount applications. The contact block&#39;s wiring compartments have reversible wiring terminals and reversible, interchangeable protective covers. Lateral wiring ports in each cover guide inserted wires to the covered terminal, and an axially facing cover opening provides tool access to the terminal.

Description:
FIELD OF THE INVENTION 
     The invention relates to electric power switches and, in particular, to the contact block portion of a switch, which houses electrical contacts and conductors and has terminals for connecting external wiring to the conductors. 
     BACKGROUND OF THE INVENTION 
     Contact blocks have a protruding operating member such as a shaft (reciprocating or rotary) and are specifically built for panel mounting or for DIN rail mounting, but not for both. A contact block built for panel mounting typically is secured against the back of a panel, the operator shaft protruding to the front of the panel through a hole. The close proximity of the panel necessitates rear-facing terminal screws for making the wiring connections. A contact block built for DIN rail mounting typically has a rear-facing slot that embraces a DIN rail. Front-facing terminal screws are provided because the DIN rail and/or its supporting structure would block access to rear-facing terminal screws. 
     SUMMARY OF THE INVENTION 
     The invention concerns a reconfigurable contact block that can be mounted at its front (operator) end behind a panel or at its rear end to a DIN rail or other support. The contact block&#39;s wiring compartments have reversible wiring terminals and reversible, interchangeable protective covers. 
     A contact block according to the invention comprises a casing having an axially facing front end, an axially facing rear end, a plurality of sides and internal switching contacts. At least one wiring compartment located at one side of the casing has an open front end and an open rear end. A switch conductor extends laterally into the wiring compartment and substantially divides it into front and rear wiring chambers. An axially extending wiring terminal is in one of the wiring chambers and is connected to the switch conductor, and a removable cover is attached to the casing over the wiring compartment. The cover comprises at least one lateral wiring port axially offset from the switch conductor and an axially facing access opening near the wiring port. The cover and the casing have biaxially symmetrical mating portions that enable reversible attachment of the cover to the casing in either of two orientations so that the wiring chamber in which the wiring terminal is located is accessible by a wire through the wiring port and the wiring terminal is accessible by a tool through the access opening. 
     The contact block preferably has two wiring compartments located at opposite sides of the casing and two covers, one for each wiring compartment. The covers are substantially identical and the cover-mating portions of the casing are substantially identical so that either cover can be attached to the casing over either wiring compartment in either orientation. 
     Each wiring compartment preferably comprises a lateral end wall having at least one pair of axially spaced guide ports. Each guide port communicates with a respective wiring chamber and the wiring port of the cover is aligned with one of those guide ports when the cover is attached to the casing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       A preferred embodiment of the disclosed invention is described in detail below purely as an example, with reference to the accompanying drawing, in which: 
         FIG. 1  is a perspective view of a contact block according to an exemplary embodiment of the invention configured for mounting to a panel; 
         FIG. 1A  is a perspective view in section of the contact block of  FIG. 1 ; 
         FIG. 2  is a partially exploded view of the contact block of  FIG. 1 ; 
         FIG. 3  is an inverted perspective view of the contact block of  FIG. 1  with one of its identical wiring compartment covers removed; 
         FIG. 4  is an outer perspective view of a wiring compartment cover of the contact block of  FIG. 1 ; 
         FIG. 4A  is an inner perspective view of the cover of  FIG. 4 ; 
         FIG. 5  is an inverted outer perspective view of the cover of  FIG. 4 ; 
         FIG. 5A  is another inner perspective view of the cover of  FIG. 4 ; 
         FIG. 6  is a detail perspective view of a portion of  FIG. 3 ; 
         FIG. 7  is a detail sectional view of a portion of  FIG. 9 ; 
         FIG. 8  is a bottom plan view of the contact block of  FIG. 1 ; 
         FIG. 9  is a sectional view of the contact block of  FIG. 1  taken along line  9 - 9  in  FIG. 8 ; 
         FIG. 10  is a perspective view of a contact block according to an exemplary embodiment of the invention configured for mounting to a DIN rail; 
         FIG. 11  is a partially exploded view of the contact block of  FIG. 10 ; 
         FIG. 12  is a bottom plan view of the contact block of  FIG. 10 ; 
         FIG. 13  is a sectional view of the contact block of  FIG. 10  taken along line  13 - 13  in  FIG. 12 ; and 
         FIG. 14  is a detail sectional view of a portion of  FIG. 13 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As used in this application, terms such as “front,” “rear,” “side,” “top,” “bottom,” “above,” “below,” “upward” and “downward” are intended to facilitate the description of the contact block of the invention, and are not intended to limit the structure of the invention to any particular position or orientation. 
     Referring to  FIGS. 1-3 ,  8  and  9 , a contact block according to the invention comprises a molded casing having a central core  4  with a front end  6  facing axially away from the core and a rear end  8  facing axially away from the core in the opposite direction. Screws  9  hold the core components together. The core also has a first side  10 ; a second side  12  opposite the first side; a third side  14  extending between the first and second sides; and a fourth side  16  opposite the third side. An axially movable input shaft (plunger)  18  extends from a boss  20  at front end  6 . Two holes  22  in front end  6  receive mounting screws S for securing the contact block to and against a panel (not shown), which typically has a hole through which boss  20  and shaft  18  would extend. Rear end  8  also has two screw holes  24  for alternate mounting of a DIN rail clip  21  (see  FIGS. 10-13 ), which has a slot  23  adapted to embrace a DIN rail. Alternatively, rear end  8  may be formed with an integral DIN rail slot. 
     As seen in  FIG. 9 , an axially movable brush  28  within the core carries two brush contacts  26  at its opposite ends. The actuator for this brush contact assembly is conventional and comprises an axially movable contact basket  25  having an aperture through which brush  28  extends; a balance contact spring  27  between contact basket  25  and the front face of brush  28 ; and an actuation spring  29  between contact basket  25  and the rear end  8  of the core. Brush contacts  26  engage respective stationary contacts  30  carried at the inner ends of respective conductors  32 . A pushbutton operator (not shown) on the outer end of shaft  18  provides user input for actuation.  FIG. 9  shows an example of a normally closed (NC) actuator arrangement: inward movement of shaft  18  engages contact basket  25  and causes the contacts  26 ,  30  to separate, breaking the circuit.  FIG. 1A  shows an example of a normally open (NO) actuator arrangement: inward movement of shaft  18  engages contact basket  25  and causes contacts  26 ,  30  to close, making the circuit. It should be understood that the invention is not limited to any particular type of internal actuator or contact arrangement, or to the type of external operator that provides user input to the actuator. 
     Referring to  FIGS. 2 ,  3  and  9 , each side  10 ,  12  of the core has an integrally formed wiring compartment  34  defined by parallel tapered extensions  36  of sides  14 ,  16  and an interconnecting lateral end wall  38 . The edges of extensions  36  and end wall  38  define a front opening  35  and a rear opening  33  for tool access to the wiring compartment. Each end wall  38  has a pair of front wire guide ports  39  and a pair of rear wire guide ports  41 . Referring to  FIGS. 1A and 9 , each conductor  32  extends laterally outward into its respective wiring compartment  34 , substantially dividing it into a front wiring chamber  40  adjacent guide ports  39  and a rear wiring chamber  42  adjacent guide ports  41 . Thus, each front wire guide port  39  serves to guide the end of a wire into front wiring chamber  40  and each rear wire guide port  41  serves to guide the end of a wire into rear wiring chamber  42 . 
     A terminal assembly for each wiring compartment  34  is connected to conductor  32  in one of the wiring chambers depending on the application: in rear wiring chamber  42  for panel mounting as shown in  FIGS. 1A and 9 ; in front wiring chamber  40  for DIN rail mounting as shown in  FIG. 13 . Each terminal assembly is conventional and comprises a terminal screw  44  that engages a threaded hole  46  in conductor  32  and preferably includes a lock washer  49  beneath the head of the screw and a roughened wire clamping washer  48 , which can clamp one or two wires inserted through the wire guide port(s)  39  or  41 . 
     Referring to  FIGS. 2-7  and  14 , each wiring compartment  34  is provided with a protective molded cover  50  that snaps onto casing  4  and is held in place by four corner snap tabs  52  that respectively engage four recesses  54  in casing extensions  36 . The sloped edges  56  of extensions  36  act as ramps that spread opposing tabs  52  apart as cover  50  is pressed onto the wiring compartment until the tabs reach and engage recesses  54 . Cover  50  can be pried off if necessary by inserting and twisting a flat screwdriver blade or similar tool in the gap  58  between the casing and the cover. Cover  50  also has a solid end wall  60 , a U-shaped terminal access opening  62  in the opposite end wall  64  and a side-by-side pair of wiring ports  66  in its lateral end wall  68  that are axially offset toward opening  62 . 
     Cover  50  has a universal configuration that enables it to be installed over either wiring compartment  34  in either of two orientations as required by the mounting application, i.e., as a function of which wiring chamber  40 ,  42  houses the terminal assembly. For panel mounting, cover  50  would be installed with its opening  62  facing rearward to enable access to terminal screw  44  in rear wiring chamber  42  (see  FIGS. 1 ,  1 A,  2 ,  3 ,  8  and  9 ). For DIN rail mounting, cover  50  would be installed with its opening  62  facing forward to enable access to terminal screw  44  in front wiring chamber  40  (see  FIGS. 10-13 ). In either orientation, cover wiring ports  66  are aligned with one pair of wiring chamber guide ports  39  or  40  so that one or two wires W can be inserted through the aligned ports and into the appropriate wiring chamber, where they can be clamped by tightening the terminal screw  44  (see  FIG. 1A ). 
     The positional versatility of cover  50  is due to the biaxial symmetry of the mating portions of the cover and the casing, as is evident in  FIGS. 2-9 ,  13  and  14 . The mating portions of the casing, which are identical on each side  10 ,  12 , comprise (1) the laterally protruding contoured edge  37  of each side extension  36 , which has a double reverse curved and straight profile, and (2) the four tab-receiving recesses  54 . These casing features collectively are symmetrical about a longitudinal axial plane, i.e., one containing the axis of shaft  18  and bisecting both wiring compartments  34 . They are also symmetrical about a plane perpendicular to that axial plane and bisecting both wiring compartments between guide ports  39  and  41 . The mating portions of the cover comprise (1) its two contoured edges  67 , which are substantially congruent with the contoured edges  37  of the casing, and (2) its four snap tabs  52 , which are axially and laterally spaced to fit into recesses  54 . These mating cover features collectively are symmetrical about the same two perpendicular planes. 
     While a preferred embodiment has been chosen to illustrate the contact block of the invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the scope of the invention as defined by the appended claims.