Abstract:
A switch operates between a first and a second position which selectively connects a load to a first and a second power supply. The connections are made by sliding one or more rods along their axis. The ends of the rods fit within channels to form electrical contact with the first and second power supply.

Description:
FIELD OF THE INVENTION 
   The invention relates generally to electrical switches, and more specifically to switches used to switch between a primary power source and an auxiliary power source. 
   BACKGROUND OF THE INVENTION 
   The reliable supply of electricity is important for businesses and homes. Indeed, virtually every business and home relies upon the continuous supply of electricity to refrigerate food, to operate heating and cooling systems and many other appliances. 
   In some applications, the uninterrupted supply of electricity is absolutely critical. For example, computer systems generally require a virtually perfect power supply. Even a momentary glitch can disrupt their operation. Consequently, where the supply of electricity is unreliable, back-up power sources commonly referred to uninterrupted power supplies are used. These usually include a power detection and filtering circuit. If the main power fails, the back-up power source immediately detects the failure and switches to a battery or other back-up source. In more sophisticated systems, the back-up power source will switch to an alternative power supply such as a generator if the main power remains off line. 
   Although these types of systems are effective even for the most demanding of applications, they are also expensive. The circuitry required to monitor the main power supply and associated battery back up are relatively complex. Moreover, this type of uninterrupted power supply is not necessary for many applications. For example, many businesses or homes can tolerate a short interruption in their power supply. Interruptions of only a few minutes have little effect on heating or cooling systems. Critical applications such as a computer can depend upon a local back-up power supply. If the main power supply continues to fail, a local generator can be started to provide back-up power. 
   The installation of a back-up generator requires that it is connected into the loading circuits in a manner that does not interfere with the normal delivery of power from a local utility company. The back-up generator must be disconnected when the local utility company provides power to prevent large flows of electricity between the two sources. In most conventional home or business settings, the internal wiring is connected directly to the local utility company through a power meter and breaker switches. The power meter is used to monitor usage for billing purposes. The breaker switches are used to prevent excessive flow of current through any loading circuit. 
   The addition of an auxiliary power supply requires a switch which is capable of handling the current drawn by an entire home or business. Especially in larger business applications, the total current drawn from a back-up power supply or from the power grid can be substantial. The switch must be able to handle large currents without heating. In order to do so, electrical transfer switches are typically very large. In order to avoid heating at the switch contacts, these are very substantial in size. A transfer switch suitable for high-current applications which is relatively small is desired. 
   SUMMARY OF THE INVENTION 
   According to one aspect of the invention, a switch is especially suitable for connecting a load to one of two power supplies. The switch has a first and second set of connections. The first set of connections is for connecting with a first power supply. The second set of connections is for connecting with a second power supply. The switch also has a first and a second set of contacts. Each of the contacts has a first and a second connection block. The first connection block defined a first surface channel extending from a first end to a second end of the first connection block. The second connection block defines a second surface channel extending from a first end to a second end of the second connection block. The first surface channel and the second surface channel are aligned to define an interior channel open at the first and second ends of the first and second connection blocks. The first set of contacts is electrically coupled with the first set of connections and the second set of contacts is electrically coupled with the second set of connections. The switch also includes a third set of connections for connecting to a load and a set of plungers. The set of plungers are electrically coupled with the third set of connections. The plungers have a first end and a second end. The first ends of the plungers are configured to fit within and make electrical contact with the interior channels defined by the first set of contacts. The second ends of the plungers are configured to fit within and make electrical contact with the interior channels defined by the second set of contacts. 
   According to further aspects of the invention, the first, second and third set of connections each comprise an interior channel for receiving an end of a wire and a screw for making physical and electrical connection with the end of the wire. The switch also includes insulated board. The first, second and third set of connections are mounted on the insulated board. The first set of connections are positioned in a first row proximate a first end of the insulated board. The second set of connections are positioned in a second row proximate a second end of the insulated board. The third set of connections are positioned in a third row between the first end and the second end of the insulated board. The second and third rows are parallel to the first row. The first and third set of connections are evenly spaced. The even spacing of the third set of connections is offset from the even spacing of the first set of connections so that wires connecting with the third set of connections are offset from the first set of connections and pass through the even spacing of the first set of connections. 
   According to still further aspects of the invention, the insulated board has a top and a bottom side. The first, second and third set of contacts are positioned on the top side and the first, second and third set of connections are positioned on the bottom side. The first and the second surface channels each define a v-shaped groove so that the interior channel defined by the first and the second connection block has a square cross section. The set of plungers comprise a set of square rods positioned between the first and the second set of contacts to selectively engage the first and the second set of contacts. The set of square rods are oriented that their side walls lie at an approximately forty five degree angle with respect to the top side of the insulated board. 
   According to still further aspects of the invention, the switch further includes an insulated bar, a handle and a third set of contacts positioned between the first and the second set of contacts. The third set of contacts electrically connect the set of plungers with the third set of connections. Each of the third set of contacts has the same construction as the first and second set of contacts. The set of plungers pass through the insulated bar. The insulated bar has a top half and a bottom half between which the set of plungers are pinched to form a firm physical connection. The handle is operationally coupled with the insulated bar and configured to move the insulated bar from a first position to a second position. When the insulated bar is in the first position, the set of plungers engage the first set of connections. When the insulated bar is in the second position, the set of plungers engage the second set of connections. 
   According to another aspect of the invention, a three-phase switch is especially suitable for selecting between two power sources. The switch includes a housing, a first, second and third set of connections, a first and a second set of cylinders and a set of pistons. The first set of connections connect with a first power source. The first set of cylinders are electrically connected with the first set of connections. Each of the cylinders have an electrically conductive inner wall. The second set of connections connect with a second power source. The second set of cylinders electrically connected with the second set of connections. Each of the cylinders have an electrically conductive inner wall. The third set of connections connect with a load. The set of pistons electrically connect with the third set of connections. Each of the pistons has an electrically conductive outer wall that is sized to fit within the inner walls of the first set of cylinders and the inner walls of the second set of cylinders. The set of pistons are switchable between a first and a second position. The first position establishes an electrical connection between the first power source and the load by electrical contact between the electrically conductive outer walls of the set of pistons and the electrically conductive inner walls of the first set of cylinders. The second position establishes an electrical connection between the second power source and the load by electrical contact between the electrically conductive outer walls of the set of pistons and the electrically conductive inner walls of the second set of cylinders. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1A  is a bottom view of a three-phase switch shown in the normal position. 
       FIG. 1B  is a bottom view of the three-phase switch of  FIG. 1A  shown in an auxiliary position. 
       FIG. 2  is a side view of the three-phase switch of  FIG. 1A . 
       FIG. 3  is a cross-sectional view of the three-phase switch of  FIG. 1A  taken from the view shown as A—A in  FIG. 1A . 
       FIG. 4A  is a bottom view of a top half of a contact. 
       FIG. 4B  is a side view of the top half of the contact shown in  FIG. 4A . 
       FIG. 4C  is a top view of the top half of the contact shown in  FIG. 4A . 
       FIG. 5A  is a top view of the bottom half of a contact. 
       FIG. 5B  is a side view of the bottom half of the contact shown in  FIG. 5A . 
       FIG. 5C  is another side view of the bottom half of the contact shown in  FIG. 5A . 
       FIG. 6  is a bottom view of a switch showing a preferred positioning of electrical connections. 
       FIG. 7  is an electrical schematic drawing of the three-phase switch of  FIG. 1A . 
       FIG. 8  is a top view of a two-phase switch. 
       FIG. 9  is a top view of a one-phase switch. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   An electrical power transfer switch has two positions. One position can be used to connect a load to a power source such as line power from a commercial power grid. Should the grid fail for any reason, the switch it moved to a second position. This disconnects the load from the power grid and connects the load to an auxiliary power source. The transfer from the grid to the auxiliary power is made by moving a rod along its axis. When fully extended in one direction, the rod engages a contact which is electrically connected with the power grid. And, when fully extended in the opposite direction, the rod engages another contact which is electrically connected to the auxiliary power supply. The rod engages contacts. These contacts define an interior channel that engages the rod. The interior channel has a profile that is complementary to that of the rod so that contact is made around the entire or a substantial portion of the contact. 
   Turning to  FIG. 1 , one preferred embodiment of a three-phase switch  100  is described. It includes three rods  102 ,  104  and  106 . These are physically arranged in parallel. In the position shown, the rods  102 ,  104  and  106  engage contacts  108 ,  110  and  112 , respectively. These are, for example, the contacts which are electrically coupled with a power grid. Along the middle of the rods  102 ,  104  and  106 , they engage another set of contacts  114 ,  116  and  118 , which are electrically connected with a load. Thus, rods  102 ,  104  and  106  connect the power grid to the load. 
   The rods  102 ,  104  and  106  are held together by an insulating bar  120 . The ends of bar  120  connect with the bottom end of a lever  122 , which in turn connects with a handle. When an operator moves the handle, lever  122  is moved. Turning to  FIG. 1B , the three-phase switch  100  is shown in the other position. Here, the handle has been moved to its auxiliary position. The bottom end of lever  122  is likewise moved to its other position along with bar  120 . This, in turn moves the rods  102 ,  104  and  106  so that they are removed from contacts  108 ,  110  and  112  and so that the load is electrically disconnected from the electric grid. Instead, the opposite end of rods  102 ,  104  and  106  engage contacts  124 ,  126  and  128 , which connects the auxiliary power with the load. 
   Returning to  FIG. 1A , blocks  138  and  140  attach along the sides of insulated board  130 . Levers  122  attach to blocks  138  and  140  through a pin  222  (shown in  FIG. 2 ) which permits them to pivot. Another set of pins  142  pass through levers  122  and engage another set of blocks  145  and  146 . These have a u-shape which define an interior channel. The bar  120  passed into the channel. Bolts  302  (shown in  FIG. 3 ), connect the blocks  145  and  146  to the bar  120 . Thus, levers  122  move blocks  145  and  146 , which move bar  120 , and which moves rods  102 ,  104  and  106 . 
   Contacts  108 ,  110 ,  112 ,  114 ,  116 ,  118 ,  124 ,  126  and  128  are attached to insulated board  130 . The insulated board  130  is rectangular. Each end of the insulated board joins an end board  132  and  134 . Contacts  108 ,  114  and  124  are arranged along an axis aligned with rod  102 . Contacts  110 ,  116  and  126  are arranged along an axis aligned with rod  104 . And, contacts  112 ,  118  and  128  are arranged along an axis aligned with rod  106 . Contacts  108 ,  110  and  112 , which couple with a power grid are arranged along a row. Contacts  114 ,  116  and  118 , which couple with a load, are arranged along a row. And, contacts  124 ,  126  and  128 , which couple with auxiliary power, are arranged along a row. Each of these rows is perpendicular to the rods  102 ,  104  and  106 . 
   Turning to  FIG. 1B , the switch  100  has been moved to the auxiliary position. Rods  102 ,  104  and  106  have been slid along their axis by movement of lever  122  so that they no longer engage contacts  108 ,  110  and  112  but instead engage contacts  124 ,  126  and  128 . Rods  102 ,  104  and  106  continue to engage contacts  114 ,  116  and  118 . This establishes an electrical connection between an auxiliary power source and the load. 
   Turning to  FIG. 2 , a side view of the three-phase switch  100  is shown. The insulated board  130  extends along the length of the switch  100 . The insulated board  130  is shown in a horizontal orientation. It has a substantially uniform thickness. It joins end board  132  on the left and end board  134  on the right. The end boards  132  and  134  extend vertically up from the insulated board  130 . Screws  202  extend through the insulated board  130  and into the end board  132  and  134 . The end boards  132  and  134  are slightly higher than the contacts  108 ,  114  and  124  and the lever  122 . A housing or cover can be added so that these elements are contained. Alternatively, the switch  100  can be mounted so that these elements are concealed. 
   Below the insulated board  130 , an electrical connection is aligned with each of the contacts. As shown, connections  204 ,  206  and  208  are positioned below contacts  108 ,  114  and  124 , respectively. Bolts  210  and  212  pass through contacts  204  and  208  and engage contacts  108  and  124 . These bolts also establish an electrical path from the contacts  108  and  124  to the connections  204  and  208 . A bolt also connects connection  206  to contact  114 . It is not visible in this view due to the orientation of the connection  206 . 
   Connection  208  is formed of a flat metal plate  214  which defines a hole for bolt  212 . The plate  214  also connects with a metal cube  216  which defines an interior channel  218 . A screw  220  passes through the metal cube  216 . When an electric cable is placed inside channel  218 , screw  220  is tightened to crimp the cable and form a firm physical and electrical connection. The other connections have the same configuration. 
   Lever  122 , which moves rods  102 ,  104  and  106 , moves about pivot  222 . This pivot passes though lever  122  and engages block  138 . A handle  224  connects at the bottom end of lever  122 . Another pivot  226  attaches block  145  to the top end of handle  122 . This pivot  226  passes through a slot  228  in lever  122 . As the lever  122  is moved from one position to another, the pivot  226  slides along the slot  228  and translates the rotational movement of the lever  122  into lateral movement of block  145  and rod  102 . 
   Turning to  FIG. 3 , a cross-section of the three-phase switch  100  is shown. Levers  122  extend along each side of the three-phase switch  100 . Levers  122  are connected to blocks  138  and  140  by a pivot  222  (shown in  FIG. 2 ). Blocks  138  and  140  have an L-shape. The vertical leg of the L-shaped blocks  138  and  140  are sized to match the thickness of the board  130 . The horizontal leg of the L-shaped blocks  138  and  140  extends along the top surface of board  130 . Screws  300  pass through board  130  and engage blocks  138  and  140 . This fixes blocks  138  and  140  on board  130 . 
   Blocks  145  and  146  sit above blocks  138  and  140 , respectively, but are not connected. When lever  122  is moved, blocks  145  and  146  move with respect to blocks  138  and  140 . This movement is shown in  FIGS. 1A and 1B . Blocks  145  and  146  connect with bar  120 . Screws  302  pass through blocks  144  and  146  to fixedly attach the bar  120 . 
   Bar  120  consists of a lower half and an upper half, each made of an insulating material. Each half is notched so that they fit around the rods  102 ,  104  and  106 . Screws  144  (shown in  FIG. 1A ) connect the two halves and clamp the rods  102 ,  104  and  106  in place. 
   The individual contacts  108 ,  110  and  112  share a common construction along with the other contacts shown in  FIG. 1A . Contact  106 , for example, has a lower block  304  and an upper block  306 . The lower block  304  defines a channel that matches the profile of rod  106 . The upper block  306  defines a complementary channel that also matches the profile of rod  106 . Rod  106  has a square cross section and is oriented so that its sides lie at a forty five degree angle with respect to the face of insulated board  130 . 
   A u-shaped channel  308  passes around upper block  306  and extends midway down the lower block  304 . At its bottom ends, the channel  308  includes a set of lips which extends inward and engages a channel along each side of the lower block  304 . A set of screws  310  pass through the channel  308  and engage the lower block  304  so that channel  308  is rigidly attached to lower block  304 . Another set of screws  312  pass through channel  308 , above the set of screws  310 . This set of screws engage the upper block  306 . Channel  308  defines a hole through which screws  312  pass. The holes permit the body of screws  312  to move slightly up and down along with the upper block  306 . Along the top side of upper block  306 , a spring  314  is sandwiched between channel  308  and the top surface of upper block  306 . This forces upper block  306  to presses down against rod  106 , which also presses rod  106  down against lower block  304 . This establishes a firm contact and electrical connection between rod  106  and both the upper block  306  and the lower block  304 . 
   In an alternative embodiment, the bottom of the lower blocks  304  are dovetailed and the insulated board  130  is grooved to match so that the contacts  108 ,  110 ,  112 ,  114 ,  116 ,  118 ,  124 ,  126  and  128  are held vertically in place. In addition, an insulated plate is cut so that it matches the configuration of the contacts. The insulated plate is placed between the contacts to hold them horizontally in place. The insulated plate is positioned on top of and bonded to the insulated board  130 . 
   In a further alternative embodiment, a lip is formed around the outer edge of the u-shaped channel  308  which holds the lower block  304  and upper block  306  in place. Use of the lip can eliminate the need for the screws (or pins)  310  and  312 . 
   In a still further alternative embodiment, the handle assembly is eliminated in favor of a push-pull rod. The push-pull rod is positioned parallel to the axis of the rods  102 ,  104  and  106 . The push-pull rod connects with bar  120  so that movement of the push-pull rod controls movement of the rods. The push-pull rod can be operated by an automatic, motorized system. 
   Turning to  FIGS. 4A–C , the upper block is further described. On its top face  400 , a circular recess  402  is formed. This is used to hold the spring  314  in place. In its bottom face  404 , the upper block defines a v-shaped channel  406 . The v-shaped channel  406  extends from one end to the other of the upper block. Its profile matches the top half of the rods. 
   Turning to  FIGS. 5A–C , the lower block is further described. Its top face  502  defines a v-shaped channel  504 . Its profile matches the bottom half of the rods. Along its side walls  506  and  508 , a channel  510  is formed. This engages the lip of the unshaped channel  308  shown in  FIG. 3 . 
   Turning to  FIG. 6 , the bottom side of the insulating board  130  is shown along with electrical connections for connecting the switch to a circuit. Board  130  is shown separate from the other components of the switch for simplicity of illustration. Connections  204 ,  206  and  208  are positioned in rows along the bottom of board  130 . They are aligned with the contacts on the opposite face of the board. The middle row of connections  206  are oriented at a ninety degree rotation from the orientation of the lower connections  204 . The top row of connections  208  are oriented at a ninety degree rotation from the orientation of the middle connections  206 . This configuration permits wires  602  to pass into the outer end of connections  204 . Because connections  206  are rotated, the connections they make are offset. This permits wires  604  to pass along the side of connections  204 . Wires  606  pass into the outer end of connections  208 . This configuration avoids overlap of the wires. 
   Turning to  FIG. 7 , an electrical schematic of the switch  100  is shown. It has a set of contacts  702  for connecting with a power source such as an electrical grid. It has a set of contacts  704  for connecting with an auxiliary power supply. And, it has a set of contacts  706  for connecting with a load. 
   Turning to  FIG. 8 , a two-phase switch  800  is shown. It has the same construction as the switch described in  FIG. 1A  above but with two sets of connections rather than three. 
   Turning to  FIG. 9 , a one-phase switch  900  is shown. It has the same construction as the switch described in  FIG. 1A  above but with one set of connections rather than three. 
   Although the invention has been described with reference to specific preferred embodiments and with reference to specific applications, those skilled in the art will appreciate that many modifications and variations can be made without departing from the invention. All such variations and modifications are intended to be encompassed within the scope of the following claims.