Abstract:
An electrical switch assembly is provided for use as a single-pole, double-throw switch. The assembly includes a housing having an interior cavity. First and second stationary contacts are positioned on one side of the interior cavity, and third and fourth stationary contacts are positioned on the other side of the interior cavity. A conductive member is interconnected between the first and third stationary contacts. A movable contact member is configured in one operative position to complete an electrical path between the first and the second stationary contacts, configured in a second operative position to complete an electrical path between the third and the fourth stationary contacts, and configured in an inoperative or OFF position to be electrically disconnected from all four stationary contacts. The improved switch assembly eliminates a center contact disposed in the housing, such that the switch assembly is less cumbersome and costly to manufacture and assemble.

Description:
BACKGROUND AND SUMMARY OF THE INVENTION 
   This invention relates to an electrical switch assembly such as a single-pole, double-throw electrical switch, and more particularly to an improved construction of a rocker type switch assembly configured without a center contact. 
   A known rocker-type electrical switch assembly, such as a single pole double throw (SPDT) switch assembly, typically includes a housing having first and second stationary contacts mounted on opposite sides of an interior cavity. A stationary “center” contact is centrally located between the stationary first and second contacts. In the prior art, the center contact is channel-shaped and interconnected with a prong that extends from the bottom portion of the housing. 
   A V-shaped movable contact member or rocker formed of an electrically conductive material is engaged with and pivotable about the channel-shaped center contact. The V-shaped movable contact member includes a first leg and a second leg that are operable to selectively connect the center contact to either the first stationary contact or the second stationary contact in response to manual operation of an actuator movably mounted to the housing. Each leg of the V-shaped movable contact member carries a button-type contact that establishes contact with the underlying first or second stationary contacts. Upon the contact member establishing contact, a circuit path is completed from the respective first or second stationary contact and associated prong, through the V-shaped contact member, to the center contact, and on to the interconnected prong. The rocker type switch assembly can be used as a transfer switch assembly to selectively connect an electrical load between one of two separate power supplies, or as a switch assembly to selectively connect a power supply to one of two separate electrical loads. 
     FIG. 11  illustrates a center contact arrangement known in the art. The arrangement includes an electrically conductive U-shaped or channel shaped center contact  14  connected to a shaft  15  and a prong  16 . The center contact  14  is configured to pivotally support a V-shaped contact member  17  having a number of button-type contacts at its ends. 
   When in an inoperative or OFF position, the V-shaped contact member  17  is positioned such that the button-type contacts are out of contact with a first  18  and a second stationary contact  19 . The V-shaped contact member  17  remains in contact and is supported by the center contact  14 . To place the switch in a first ON position, a plunger type actuator is pivoted relative to the switch housing to cause the V-shaped contact member  17  to rock or pivot on one of the walls of the center contact  14 . One of the arms of the contact member  17  moves downwardly into engagement with underlying stationary contact  18 , completing an electrical path from the stationary contact  18  through the contact member  17  to the center contact  14 . When returned to the OFF position, the V-shaped contact member  17  pivots on the wall of the center contact  14 , disengaging the contact member  17  from the stationary contact  18 . 
   The center contact arrangement works in a similar fashion with respect to a second ON position, in which the other leg of the V-shaped contact member  17  establishes contact with the respective second contact  19 , completing an electrical path from the second contact  19  through the contact member  17  to the center contact  14 . 
   The known rocker-type transfer switch assembly has several drawbacks. For example, the first and the second contacts are located in close proximity to the center contact channel. Because of this proximity, arcing or short circuiting is possible when the first and second contacts are connected to separate electrical inputs. Furthermore, the configuration of the center contact area is cumbersome and inefficient to assemble. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide an improved rocker-type switch assembly with a simplified design that is less cumbersome to manufacture, and yet functions in an effective manner to selectively connect a power supply between separate electrical loads, or selectively connect an electrical load between separate power supplies. 
   In accordance with one aspect, the present invention provides an electrical switch assembly that includes a first and a second stationary contact positioned on one side of the assembly, and a third and a fourth stationary contact positioned on an opposite of the assembly. A conductive member electrically connects the first and third stationary contacts. The switch assembly further includes a movable contact member configured to selectively establish an electrical path between the first and second stationary contacts in a first position, and configured to selectively establish an electrical path between the third and the fourth stationary contacts in a second position. 
   The movable contact member may include two pairs of arms. A first pair of arms is configured to selectively establish an electrical path between the first and second stationary contacts when the movable contact member is in the first position, and a second pair of arms is configured to establish an electrical path between the third and the fourth stationary contacts when the movable contact member is in the second position. The movable contact member can have a nonlinear configuration, such as in the form of a V-shaped member having the first and the second pairs of arms extending outwardly from a common center or apex. Each of the arms has a contact member secured toward its outer end to engage each of the four contacts. Furthermore, the movable contact member may be pivotable about four centering ears integrated into a housing forming a part of the switch assembly, and to which the stationary contacts are mounted. 
   In accordance with another aspect, the present invention provides an electrical switch assembly that includes a housing having an interior cavity. A first and a second stationary contact are positioned on one side of the interior cavity, and a third and a fourth stationary contact are positioned on the other side of the interior cavity. A movable contact member is configured in a first position to complete an electrical path between the first and the second electrical contacts, and is configured in a second position to complete an electrical path between the third and the fourth contacts, and is further configured in an inoperative or OFF position to be electrically disconnected from all four contacts. 
   The improved electrical switch assembly eliminates the center contact disposed in the housing, such that the switch assembly is less cumbersome to assemble and less costly to manufacture. 
   The invention also contemplates a method of selectively connecting an electrical load with a first power supply or a second power supply, substantially in accordance with the foregoing summary. In addition, the invention contemplates a method of selectively connecting an electrical power supply with a first electrical load or a second electrical load, substantially in accordance with the foregoing summary. 
   Various other features, objects and advantages of the invention will be made apparent from the following description taken together with the drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The drawings illustrate the best mode presently contemplated of carrying out the invention. 
     In the drawings: 
       FIG. 1  is an isometric view of an assembled electrical switch assembly constructed in accordance with the present invention; 
       FIG. 2  is an exploded isometric view illustrating the components incorporated into the electrical switch of  FIG. 1 ; 
       FIG. 3  is a section view along  3 — 3  of  FIG. 1 , showing the movable contact member in an inoperative or OFF position; 
       FIG. 4  is a section view similar to  FIG. 3 , showing the movable contact member in a first operative position; 
       FIG. 5  is a section view similar to  FIGS. 3 and 4 , showing the movable contact member in a second operative position; 
       FIG. 6  is a section view taken along line  6 — 6  of  FIG. 3 ; 
       FIG. 7  is a plan view showing the movable contact member incorporated into the electrical switch of  FIG. 1 ; 
       FIG. 8  is a section view taken along line  8 — 8  of  FIG. 3 ; 
       FIG. 9  is a bottom plan view of the electrical switch assembly of the present invention, with reference to line  9 — 9  of  FIG. 3 ; 
       FIG. 10  is a partial section view taken along line  10 — 10  of  FIG. 4 ; and 
       FIG. 11  is a section view of a prior art switch assembly having a center contact member. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to  FIGS. 1 and 2 , an electrical switch assembly  20  of the present invention generally includes a housing  25  made up of a base  30 , a cover  35 , and an actuator  40 . The actuator  40  controls movement of a movable contact member  45  positioned within the housing  25 . 
   Referring to  FIGS. 1–6 , the housing base  30  includes a pair of side walls  50  and a pair of end walls  55 , which cooperate to define an internal cavity  60  within which the movable contact member  45  is received. The side walls  50  and the end walls  55  extend upwardly from a bottom wall  65 , which defines the lower extent of the internal cavity  60 . 
   Referring to  FIGS. 2 ,  6  and  10 , a series of stationary contacts are secured to the bottom wall  65  of the housing base  30 . The stationary contacts include a first contact  70  and a second contact  75 . As illustrated in  FIG. 10 , each stationary contact  70  (not shown) and  75  includes a contact head  85  defining an upwardly facing contact surface  90 , in combination with a shaft  95  that extends through an opening or aperture  100  formed in the bottom wall  65  of the housing base  30 . Shaft  95  also extends through an aligned aperture  105  formed in a conductive strip  110  in engagement with the underside of the bottom wall  65 . The conductive strip  110  is electrically connected to a depending prong  125  in accordance with conventional construction. A retainer head  126  is formed at the end of the shaft  95  opposite the contact head  85 . The retainer head  126  maintains each contact  70  and  75  and the associated conductive strip  110  and prong  125  in engagement with the bottom wall  65 , and establishes an electrical connection of each contact  70  and  75  with the conductive strip  110 . The stationary contacts  70  and  75  and the bottom wall  65  are configured and arranged such that the upper contact surfaces  90  of contact heads  85  are generally coplanar. 
   As shown in  FIGS. 2 ,  6 , and  10 , the series of stationary contacts further include a third stationary contact  115  and a fourth stationary contact  120 . In a similar manner to stationary contacts  70  and  75  and as illustrated in  FIG. 10 , each stationary contact  115  (not shown) and  120  includes a contact head  127  defining an upwardly facing contact surface  130 , in combination with a shaft  135  that extends through an opening  137  in the bottom wall  65 . Each shaft  135  also extends through an aligned aperture  140  formed in a terminal strip  145 , in engagement with the underside of the bottom wall  65 . Each terminal strip  145  is electrically connected to a depending contact prong  150  in accordance with conventional construction. A retainer head  155  is formed at the end of each shaft  135  opposite the contact head  127 . Each retainer head  155  maintains each contact  115  and  120  and its associated terminal strip  145  in engagement with the bottom wall  65 , and establishes an electrical connection of each contact  115  and  120  with one of the terminal strips  145 . Again, the stationary contacts  115  and  120  and the bottom wall  65  are configured and arranged such that the upper contact surfaces  130  of the contact heads  127  are generally coplanar with one another, as well as coplanar with the contact surfaces  90  of the contact heads  85  of the stationary contacts  70  and  75 . 
     FIGS. 2 and 6  illustrate a first pair of contacts, namely contacts  70  and  115 , and a second pair of contacts, namely contacts  75  and  120 , located on opposite sides of the cavity  60 . As will be understood, any number of contacts may be employed in the electrical switch assembly  20 . 
   Referring to  FIG. 6 , stationary contact  70  is located directly opposite contact  75 . Also, contact  115  is aligned with its respective opposite contact  120 , such that a line  160  which intersects the centers of contacts  70  and  75  is parallel to a line  165  which intersects the centers of contacts  115  and  120 . In addition, a line  170  which intersects the centers of contacts  70  and  115  is parallel to a line  175  which intersects the centers of contacts  75  and  120 . Contacts  70  and  115  and contacts  75  and  120  are equally spaced from a central axis  180  of the bottom wall  65 . 
   Still referring to  FIG. 6 , a first barrier  182  and a second barrier  184  are disposed between stationary contacts of opposite polarity. Specifically, the first barrier  182  is disposed between contacts  70  and  115 , and the second barrier  184  is disposed between contacts  75  and  120 . The barrier can be comprised of any non-conductive material known in the art, and may be formed integrally with the bottom wall  65 . 
   Referring to  FIGS. 2 ,  3 ,  7  and  10 , the movable contact member  45  includes a central v-portion  185  connected to a first pair  190  and a second pair  195  of spaced apart contact arms. Each arm of the pairs of contact arms  190  and  195  is separated by a space  200 , and each pair of contact arms  190  and  195  extend outwardly from the central v-portion  185 . The first pair of spaced apart contact arms  190  extends outwardly in a first direction from the central v-portion  185 , and the second pair of spaced apart contact arms  195  extends outwardly from the central v-portion  185  in a second direction opposite the first direction. 
   Referring to  FIGS. 2 ,  7 ,  8  and  10 , a rivet-type movable contact  205  is connected toward the outer end of each contact arm  190 . The movable contact  205  includes a contact head  210 , a shaft  215  that extends through an aperture  220  formed in the contact arms  190  and  195 , and a retainer head  225 . The retainer head  225  serves to secure each movable contact  205  to its associated contact arm  190  and establishes an electrical connection between the movable contact  205  and the contact arms  190 . Referring to  FIG. 7 , the contact head  210  of each movable contact  205  defines a downwardly facing movable contact surface  230 . 
   Similarly, a movable contact  235  is secured toward the outer end of each contact arm  195 . Referring to  FIGS. 2 ,  3 ,  7  and  10 , each movable contact  235  includes a contact head  240 , a shaft extending through an aperture (similar to shaft  215  and aperture  220  in  FIG. 10 ) formed toward the outer end of each second contact arm  195 , and a retainer head  255  on the opposite side of each second contact arm  195 . As illustrated in  FIG. 7 , the retainer head  255  secures the movable contact  235  to its associated contact arm  195  and establishes an electrical connection therebetween. The contact head  240  of each movable contact  235  defines a downwardly facing movable contact surface  260 . 
   Still referring to  FIGS. 2 ,  3  and  7 , the central v-portion  185  of movable contact member  45  is in the form of a V-shaped member made up of a first planar wall  265  and a second planar wall  270 , which intersect at a vertex  275 . The central v-portion  185  and respective vertex  275  approximately spans between the walls  50  of the housing  25 . 
   Referring to  FIGS. 2 ,  6 ,  7  and  8 , a V-shaped retainer tab  280  extends outwardly from each side of movable contact member  45 . Each tab  280  includes intersecting tab walls  285  and  290 , which are in the form of outward extensions of the central v-portion  185  of the first  265  and second  270  planar walls, respectively. When positioned within the cavity  60  of the housing base  30 , each tab  280  of the movable contact member  45  is positioned between spaced apart retaining ridges  295  extending from the walls  50  of the housing  25 . 
   Referring to  FIGS. 6–8 , the v-portion  185  of the movable contact member  45  pivots in the housing  25  about a first pair  297  and a second pair  298  of centering ears. The first pair of centering ears  297  is configured to engage the first planar wall  265 , and the second pair of centering ears  298  is configured to engage the second planar wall  270 . The first  297  and the second  298  pair of centering ears may be integrated into the bottom wall  65  of the housing base  30 . 
   Referring to  FIGS. 2 ,  3  and  7 , the first pair of spaced apart contact arms  190  of the movable contact member  45  is coplanar with each other and with the first planar wall  265  of the central v-portion  185 . Similarly, the second pair of spaced apart contact arms  195  is coplanar with each other and with the second planar wall  270  of the central v-portion  185 . The first  190  and the second  195  pairs of contact arms are formed integrally with the central v-portion  185 , and are in the form of outward extensions of the first  265  and the second  270  planar walls, respectively. With this construction, the first  190  and the second  195  pairs of contact arms are formed integrally with the material of the central v-portion  185 . The movable contact member  45  is preferably formed of a conductive material, e.g. copper plated with fine silver, although it is understood that any other satisfactory material may be employed. 
   Referring to  FIGS. 2–3 , the housing cover  35  is configured to engage with the upper ends of the housing base side walls  50  and end walls  55 , and cooperates with the actuator  40  to enclose the internal cavity  60  defined by the housing base  30 . The general structure and assembly of the base  30 , the cover  35 , and the actuator  40  are known in the art. In a manner as is known, the cover  35  includes a pair of flexible retaining fingers  300  configured to engage with a retaining surface  305  defined by the housing base  30 , so as to secure the cover  35  to the base  30 . 
   The actuator  40  includes an actuator member  310  pivotally mounted between spaced apart side walls  315  of the cover  35  via a pivot pin  320 . The actuator member  310  includes a manually engageable actuator tab  325  in combination with a pair of wings  330  that extend downwardly and outwardly from the actuator tab  325 . The wings  330  function to enclose the upper end of the base internal cavity  60  when the cover  35  and the actuator  40  are mounted to the housing base  30 . 
   The actuator member  310  further includes a pair of barrel sections  335  located inwardly of the pivot pin  320 . An actuating plunger  340  is mounted for inward-outward movement within a passage  345  defined by each barrel section  335 . A spring  350  is received within the passage  345  and biases the plunger  340  in a downward or an outward direction. The plunger  340  includes a generally conical outer end or tip  355  configured to engage and provide movement of the movable contact member  45  in response to pivoting movement of the actuator member  310  about the pivot pin  320 . 
   In operation and as illustrated in  FIGS. 3–5 , the electrical switch assembly  20  functions as follows. It is understood that the electrical switch assembly  20  may be connected as a switch that is operable to selectively connect an electrical power supply to one of two separate electrical loads. Electrical power is supplied to the contacts  70  and  75  via the conductive strip  110  and connected prong  125 , for selective connection to one of a pair of electrical loads interconnected with the electrical switch assembly  20  via the stationary contacts  115  and  120  and their associated respective terminal strips  145  and prongs  150 . Alternatively, the electrical switch assembly  20  may be connected as a transfer switch. When the electrical switch assembly  20  is connected as a transfer switch, two separate electrical power supplies are connected to the stationary contacts  115  and  120 , respectively, and a single load is connected to the stationary contacts  70  and  75  via the connected the conductive strip  110  and prong  125 . 
   To prevent connection between the stationary contacts  70  and  115 , or between the stationary contacts  75  and  120 , the electrical switch assembly  20  is maintained in its inoperative or OFF position of  FIG. 3 , in which actuator member  310  is in an intermediate position and neither of movable contacts  205 , nor movable contacts  235 , are engaged with the respective underlying respective stationary contacts  70 ,  75 ,  115 , and  120 . Typically, a detent arrangement is interposed between the cover  35  and the actuator member  310  for maintaining the movable contact member  45  in its inoperative position of  FIG. 3 . In this position, the conical tip  355  of each plunger  340  is engaged with the vertex  275  of the v-portion  185  of the movable contact member  45 , forcing the vertex  275  against each pair of centering ears  297  and  298  of the housing base  30 . The conical tip  355  is angled in a manner so as to correspond with the angle between the first  265  and second  270  walls, respectively, of the v-portion  185 , to prevent movement of movable contact member  45  from its inoperative position. 
   To establish an electrical connection between the stationary contact  75  and the stationary contact  120 , the actuator member  310  is pivoted in a clockwise direction about the pivot pin  320  toward the first operative position of  FIG. 4 . This operative position functions to either interconnect a first electrical load connected to stationary contact  120  with a power supply connected with contacts  70  and  75 , or to connect a first power supply connected to contact  120  with an electrical load connected with the contacts  70  and  75 . The pivoting movement of the actuator member  310  functions to slide the plungers  340  in an outward direction from the vertex  275  and toward the first movable contacts  205 . The vertex  275  of the movable contact member  45  acts as a pivot about which movable contact member  45  rocks in a counterclockwise fashion, to bring movable contact surfaces  230  of movable first contacts  205  into engagement with the upper contact surfaces  90  and  130  of the stationary contacts  75  and  120 , respectively. The barrel sections  335  and the plungers  340  are oriented such that each spring  350  provides a primarily downward force on the first contact arms  190  so as to urge the movable first contacts  205  into engagement with the stationary contacts  75  and  120 . Simultaneously, the downward force applied by each plunger  340  is operable to maintain engagement of the portion of first wall  265  adjacent to vertex  275  with the centering ears  297  of the bottom wall  65 . 
   In the position shown in  FIG. 4 , the plunger  340  is in engagement with each of the contact arms  190 , which are flexible and resilient relative to the v-portion  185  of the movable contact member  45 . The space  200  between the contact arms  190  allows the plungers  340  to flex the contact arms  190  in different amounts as required so as to establish full contact with the stationary contacts  75  and  120 . This feature is illustrated in  FIG. 10 . Initial movement of movable contact member  45  may result in one of movable contacts  205  being spaced slightly above its associated stationary contact  75  or  120 . As shown in  FIG. 10 , application of the biased downward forces (shown as arrows) exerted by the plungers  340  functions to flex the first contact arms  190  downwardly so as to engage the movable first contact  205  with the stationary contacts  75  and  120 . 
   To break the connection with the stationary contacts  75  and  120 , an operator moves the actuator member  310  to the inoperative position of  FIG. 3 . To then establish a connection between stationary contacts  70  and  115 , the operator pivots the actuator member  310  in a counterclockwise direction to a position as shown in  FIG. 5 , which causes the clockwise pivoting movement of the movable contact member  45 . In the same manner described previously, this clockwise movement of the movable contact member  45  results in the inner portion of second planar wall  270  of the v-portion  185  to move into engagement with centering ears  298 , and causes the movable second contacts  235  to move into engagement with the stationary contacts  70  and  115 . In the same manner as described previously, the space  200  between the contact arms  195  enables the contact arms  195  to flex relative to one another and relative to the central v-portion  185 , to ensure proper engagement of the movable second contacts  235  with the stationary contacts  70  and  115 . 
   The configuration of the movable contact member  45  and the stationary contacts  70 ,  75 ,  115  and  120  is such that the movable contact member  45  moves smoothly between its various positions simply by selectively “rocking” the central v-portion  185  on the centering ears  297  and  298  of the housing base  30 . The flexibility of the arms  190  and  195  ensures that the movable contact member  45  is in full contact with the stationary contacts  70 ,  75 ,  115  and  120  when the switch assembly  20  is placed in either of its operative positions. The provision of the v-portion  185  allows the movable contacts  205  and  235  to share a current load equally. The flexibility of the movable contact arms  190  and  195  allows each of the movable contacts  205  and  235  to seek its own seated position, so as to ensure proper electrical contact. 
   The tabs  280  of the movable contact member  45  are positioned between the respective retaining ridges  295  to maintain the position of the movable contact member  45  within the cavity  60  of the housing base  30 . When movable contact member  45  is moved to one of its operative positions, such as the first operative position as shown in  FIG. 4 , the first pair of contact arms  190  of movable contact member  45  engages the upper edge of ears  297 . Again, as illustrated in  FIG. 10 , the downward forces applied to the contact arms  190  by the plungers  340  functions to seat the movable contacts  205  on the stationary contacts  75  and  120 . The proper sharing of the electrical current load is accomplished by the structure of the movable contact member  45 . 
   The construction of the movable contact member  45  enables the electrical switch assembly  20  to be employed as a transfer switch, since it is impossible for contact to be established between the stationary contacts  115  and  120 . In the event that one of the movable contacts  205  were to become welded to one of the stationary contacts  75  or  120 , the movable contacts  235  cannot subsequently be moved toward a position in which the non-welded movable contacts  235  can be brought into engagement with one of the opposite stationary contacts  70  and  115 , or vice versa, and thereby avoid creating a common connection of all of the movable contacts  205  and  235 . The strength of the material of the movable contact member  45  is selected such that, in the event this were to occur, the biasing force applied by the associated plunger  340  is insufficient to flex the pairs of movable contact arm  190  or  195  by an amount sufficient to establish contact with stationary contacts of opposite polarity. 
   While the invention has been shown and described with respect to particular embodiments, it is understood that alternatives and modifications are possible and are contemplated as being within the scope of the present invention. For example, and without limitation, the spaced apart contact arms of the movable contact member are shown and described as being formed integrally with the material of the central v-portion. It is also contemplated that the separate arms of the movable contact member may be formed separately and connected to the central v-portion in any satisfactory manner. Further, the movable contact member has been shown and described as being formed of the material which itself is the conductor that establishes an electrical path between the first and the second contacts or the third and the fourth contacts. It is also contemplated that the movable contact member may be formed of a resilient material, such as plastic, and that the movable contacts and the central v-portion may be in the form of electrically conductive material connected with each other and carried by the movable contact member. In addition, while a specific type of construction is shown for providing pivoting movement of the movable contact member relative to the housing, it is contemplated that any other type of pivot or rocking connection may be employed. In addition, while the invention has been described with respect to two pairs of contact arms which extend outwardly from the center contact area, it is understood that any number of contact arms on either side of the center contact area may be employed. The number of contact arms may be equal or unequal, and the contact arms may be aligned with each other as shown or may be out of alignment with each other. Further, while a specific type of actuator has been shown and described, it is understood that any type of biased actuator which is capable of applying separate downward forces on the separate contact arms may be employed while still gaining the full advantages offered by the central v-portion and the spaced apart contact arms of the movable contact member of the present invention. 
   Various alternatives and embodiments are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter regarded as the invention.