Abstract:
A universal load switch includes convex fixed terminal contacts and convex movable contacts selectively connectable electrically to the terminal contacts. Snap blades forcibly move the movable contacts toward and away from each of the terminal contacts.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is national phase of PCT/US2010/044044 filed Jul. 31, 2010, and claims the benefits of U.S. Provisional Application Ser. No. 61/238,360 filed Aug. 31, 2009. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to electrical switches, and, more particularly, to limit switches, proximity switches and the like in which a cam, linear operator or other position adjustable device operates the switch to open or close the switch. The present invention pertains to switches known as snap switches. 
     BACKGROUND OF THE INVENTION 
     Electrical switches are used in many different types of devices to start a function, stop a function, adjust the rate or other performance of the function, etc. For example, trains, subways and other devices may have several switches positioned in various locations to sense or confirm operation of doors that open or close access openings. Some such switches are used in high voltage applications while others are used in low voltage applications. In the past, it has been necessary to provide different switch constructions for high power applications than for low power applications. It can be costly to manufacture and maintain adequate inventories of replacement switches for future service operations for manufacturers of the switches and for operators of the devices in which the switches are used. 
     Arcing between switch contacts can occur due to frequent and rapid opening and closing of the contacts, as well as due to other conditions under which the switch may have to operate. When arcing occurs, it can happen that the switch contacts become welded to each other. Breaking the welds to separate the welded contacts can be difficult, and until the condition is corrected or the switch is replaced, normal function of the devices in which the switch is installed is adversely affected. It is desirable to provide a switch with redundancy to continue operating in such damaged situations; and/or, to operate forcefully when opening the contacts to thereby break welds that may occur from arcing. 
     SUMMARY OF THE INVENTION 
     A universal load switch is provided with convex fixed terminal contacts and convex movable contacts selectively connectable electrically to the terminal contacts. Snap blades forcibly move the movable contacts toward and away from each of the terminal contacts. 
     In one aspect of one form thereof, a load switch is provided with opposed spaced terminals, terminal contacts on the opposed spaced terminals, and a contact blade assembly between the terminal contacts, the contact blade assembly including blade contacts. Snap blades forcibly moving the contact blade assembly toward and away from both of the terminals. 
     In another aspect of a form thereof, a load switch is provided with first and second spaced upper terminal contacts, first and second spaced lower terminal contacts, and a contact blade assembly have a first end disposed between the first upper contact and the first lower contact, and a second end disposed between the second upper contact and the second lower contact. Contacts of the contact blade assembly selectively engage the terminal contacts. A blade shuttle moves the contact blade assembly, and snap blades forcibly move the contact blade assembly toward and away from each of the first and second spaced upper and lower terminal contacts. 
     In another aspect of a form thereof, a load switch is provided with first upper and lower terminals having first upper and lower terminal contacts thereon, second upper and lower terminals having second upper and lower terminal contacts thereon, a plunger assembly and a blade shuttle assembly including a blade shuttle and a contact blade assembly disposed in the blade shuttle. The contact blade assembly has first and second ends between the first upper and lower terminals and the second upper and lower terminals, respectively. Upper and lower blade contacts are provided on opposite sides of the contact blade assembly at each of the first and second ends. Snap blades operatively arranged between the plunger assembly and the blade shuttle forcibly move the contact blade assembly toward and away from each of the upper and lower terminals. 
     Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims and drawings in which like numerals are used to designate like features. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a universal load switch; 
         FIG. 2  is an elevational view of the universal load switch shown in  FIG. 1 , but having an outer housing cover removed to expose internal components of the universal load switch; 
         FIG. 3  is a perspective view of a universal load switch similar to that shown in  FIGS. 1 and 2 , but having alternate connection accessories; 
         FIG. 4  is an enlarged perspective view of a subassembly in the universal load switch shown in the previous drawings; 
         FIG. 5  is a cross-sectional view of the subassembly shown in  FIG. 4  for the universal load switch; 
         FIG. 6  is an exploded view of a plunger assembly for the universal load switch; 
         FIG. 7  is a cross-sectional view of the plunger assembly; 
         FIG. 8  is a perspective view of a blade shuttle assembly in the universal load switch; 
         FIG. 9  is an exploded view of a blade assembly in a universal load switch; 
         FIG. 10  is a perspective view illustrating an assembly step for installing the blade assembly in the blade shuttle; 
         FIG. 11  is a perspective view illustrating a later assembly step for installing the blade assembly in the blade shuttle; 
         FIG. 12  is an exploded view of the blade shuttle assembly; 
         FIG. 13  is an enlarged view of a set of terminals for the universal load switch; 
         FIG. 14  is a perspective view of the butterfly assembly fully assembled and ready for installation in the housing and terminal assembly; 
         FIG. 15  is a perspective view of the butterfly assembly fully installed in the universal load switch housing; 
         FIG. 16  is an enlarged, fragmentary cross-sectional view of a distal end of the plunger in the universal load switch; 
         FIG. 17  is a view of the universal load switch; 
         FIG. 18  is a view of the universal load switch shown from a different angle than that shown in  FIG. 17 ; 
         FIG. 19  is a perspective view of the universal load switch; 
         FIG. 20  is a fragmentary view of a fully assembled a universal load switch without the housing cover being shown; 
         FIG. 21  is an elevational view showing the universal load switch in a so-called “free position”; 
         FIG. 22  is an elevational view illustrating the universal load switch at an operating condition with the plunger depressed; 
         FIG. 23  is an elevational view illustrating the universal load switch in a so-called “reset” condition; 
         FIG. 24  is a cross-sectional view of the universal load switch at the reset condition shown in  FIG. 23 ; 
         FIG. 25  is a perspective view of a second embodiment for the blade shuttle assembly in a universal load switch; and 
         FIG. 26  is a perspective view of the blade shuttle assembly shown in  FIG. 25  installed in a completed switch. 
     
    
    
     Before the embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is understood that the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting. The use herein of “including”, “comprising” and variations thereof is meant to encompass the items listed thereafter and equivalents thereof, as well as additional items and equivalents thereof. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now more specifically to the drawings and to  FIG. 1  in particular, a universal load switch  100  is shown. As shown in  FIG. 1 , universal load switch  100  includes a housing  102  to seal and protect the inner components of the switch mechanism to be described subsequently herein. Switch  100  can be connected within an electrical circuit in many different ways. By way of example and not limitation, wire leads  103   a, b, c  and  d  can be connected to the switch by soldering, crimp connecting or other suitable electrical connection, as those skilled in the art will readily understand. An alternative construction is shown in  FIG. 3  in which quick connect blade accessories  203   a - d  are provided in place of wire leads  103   a - d . Quick connect blade accessories  203   a - d  can be connected by welding, crimp connections, screws  205  (only one screw  205  being shown for exemplary purposes) or other suitable electrical connecting means to the switch. 
     For ease of description herein, and for clarity in the claims, the universal load switch will be described in the orientation shown in the drawings. Accordingly, terms such as “upper”, “lower”, “above”, “below” and other terms that imply direction and relative orientation will be used. However, it should be understood that the switches described herein can be used in different orientations, such as upside down from the primary orientation shown in the drawings, lying flat, or oriented on an edge other than as shown in the drawings. The directional and spatial descriptors used herein are merely for ease and clarity in description, and are not intended as limiting. 
     Operating components of load switch  100  are contained within housing  102 , except for the distal end of a plunger assembly  104  that protrudes from housing  102 . As will be described subsequently herein, the distal end of plunger assembly  104  can be depressed for operating load switch  100 . 
       FIG. 2  illustrates universal load switch  100  with a cover or a side panel removed from housing  102  to expose the operating mechanisms of the switch within the switch housing. Switch  100  includes a butterfly assembly  105 , which is comprised of plunger assembly  104 , a blade shuttle assembly  106  and snap blades  108 ,  110  interconnecting plunger assembly  104  and blade shuttle assembly  106 . Butterfly assembly  105  can be preassembled out of housing  102 , and thereafter installed as a single unit or subassembly in switch  100 , as will be described more fully hereinafter. 
       FIG. 4  shows butterfly assembly  105  apart from the remaining structures of switch  100 , and  FIG. 5  is a cross-sectional view of butterfly assembly  105 , more clearly showing plunger assembly  104  and blade shuttle assembly  106  interconnected by snap blades  108 ,  110 .  FIGS. 6-12  illustrate the component parts of butterfly assembly  105 , including plunger assembly  104  and blade shuttle assembly  106 . 
     Referring now to the exploded view of plunger assembly  104  shown in  FIG. 6 , plunger assembly  104  includes a plunger  112 , a C-spring  114 , a guide  116  and a rollover washer  118 . Plunger  112  is a cylindrical rod or shaft having a circumferential depression  120  at the external end thereof extending out of housing  102 , and a circumferential channel  122  at the opposite or inner end thereof. C-spring  114  is, as the name implies, a C-shaped spring body having a hole  124  centrally located in a trunk portion  126  of the C-shaped body. First and second arms  128 ,  130  project from trunk portion  126  and include notched distal ends  129 ,  131 , respectively. Guide  116  includes a hole  132  in a trunk  134  and arms  136 ,  138  projecting from opposite ends of trunk  134 . Fore and aft flange plates  140 ,  142  project from the edges of trunk  134  and arms  136 ,  138 . Accordingly, guide  116  generally defines a C-shaped channel  144  for receiving and supporting C-spring  114  in the completed assembly. 
       FIG. 7  is a cross-sectional view of the assembled plunger assembly  104 . Plunger  112  is extended into holes  124  and  132  of C-spring  114  and guide  116 , respectively. The peripheral edges defining holes  124 ,  132  are received in circumferential channel  122  of plunger  112 , and rollover washer  118  is provided there against to hold the assembled spring  114  and guide  116  on plunger  112 . As can be seen, arms  136 ,  138  define therein openings  146 ,  148  respectively. 
       FIG. 8  is a perspective view of blade shuttle assembly  106 , which includes a contact blade assembly  150  held in a blade shuttle  152 . A blade stay  154  and coil spring  156  are disposed to hold blade assembly  150  in blade shuttle  152 . 
       FIG. 9  is an exploded view of blade assembly  150 , which includes a contact blade  158  having upper contacts  160  and lower contacts  162  provided thereon. Four upper contacts  160  and four lower contacts  162  are provided in overlying alignment, extending through holes  164  defined in contact blade  158 . Upper contacts  160  and lower contacts  162  are provided in pairs on opposite faces of contact blade  158 , near opposite ends of contact blade  158 . Silver contacts  160 ,  162  that preferably are convex or hemispherical in outer surface shape can be welded or staked to one another. When formed by staking, each contact has a primary head and a shank which extends through one of the holes  164  in contact blade  158 , and during the staking process the distal end of the shank is pressed to form the opposite contact surface. A central aperture  166  is provided in contact blade  158 . 
       FIG. 10  is a perspective view illustrating an assembly step for installing contact blade assembly  150  in blade shuttle  152 . Blade shuttle  152  defines a window  168  extending therethrough and having upper and lower pedestals  170 ,  172  projecting toward each other, but spaced from each other in window  168 . Contact blade assembly  150  is tilted on an edge and inserted into window  168 . Upper and lower pedestals  170 ,  172  can be bifurcated as shown for upper pedestal  170  or can be channeled as shown for lower pedestal  172  to accommodate the width of contact blade  158  being inserted therethrough. A cylindrical opening  173  and other slots or openings can be provided through blade shuttle  152  to accommodate passing of contacts  160 ,  162  therethrough. In the exemplary embodiment, contact blade  158  is generally of a dog bone shape, having a narrower waist section at the middle thereof and wider sections containing upper and lower contacts  160 ,  162  at opposite ends of contact blade  158 . Accordingly, with contact blade  158  centrally located in window  168 , the contact blade can be rotated for placement over lower pedestal  172  such that lower pedestal  172  extends through central aperture  166 . 
       FIG. 11  is a perspective view illustrating a later assembly step for installing blade assembly  150  in blade shuttle  152 . Aperture  166  is engaged with lower pedestal  172 , with contact blade  158  extending outwardly of window  168  so that upper and lower contacts  160 ,  162  are exposed outwardly of blade shuttle  152  at both ends of contact blade  158 . Thereafter, blade stay  154  is positioned over lower pedestal  172  and against contact blade  158 , and coil spring  156  is compressed and inserted into window  168 . 
       FIG. 12  is an exploded view of blade shuttle assembly  106 , better showing blade stay  154  and spring  156 . In the completed assembly, blade stay  154  is engaged over lower pedestal  172  and against contact blade  158 . Spring  156  is engaged over a truncated conical end of blade stay  154  at the lower end of spring  156  and over upper pedestal  170  and against the upper end of window  168  at the upper end of spring  156 . Accordingly, blade assembly  150  is held yieldingly in blade shuttle  152  by the biasing force of spring  156  there against, and can tilt or twist against the force of spring  156 . 
     Above window  168 , blade shuttle  152  defines V-channels  174 ,  176  extending inwardly from opposite surfaces. In the completed assembly of switch  100 , snap blades  108 ,  110  are angularly disposed between and held in V-channels  174 ,  176  and shaped distal ends of arms  129 ,  131  of C-spring  114 . Accordingly, snap blades  108 ,  110  extend through openings  146 ,  148  defined in guide  116  and interconnect plunger assembly  104  with blade shuttle assembly  106 . 
     In the assembled switch, housing  102  also contains fixed, upper, normally open terminals  178 ,  180  having silver terminal contacts  182 ,  184 , respectively, provided above the pairs of upper contacts  160  at opposite ends of contact blade  158 , and fixed, lower, normally closed terminals  186 ,  188  having silver terminal contacts  190 ,  192  provided below the pairs of lower contacts  162  at opposite ends of contact blade  158 . Terminal contacts  182 ,  184 ,  190 ,  192  preferably also are convex or hemispherical in outer surface shape. 
       FIG. 13  is an enlarged view of one set of terminals, including upper terminal  178  and lower terminals  186  having terminal contacts  182 ,  190 , respectively. It should be understood that the other pair of upper and lower contacts is constructed substantially the same as those shown in  FIG. 13 . Terminals  178 ,  180 ,  186 ,  188  can be adapted easily for attachment to various different types of electrical conductors including the aforementioned soldered connections, screw connections, snap or sliding connections and the like, including the aforedescribed wire leads  103   a - d  or quick connect of blade accessories  203   a - d.    
       FIG. 14  is a perspective view of butterfly assembly  105  fully assembled and ready for installation in housing  102 , which has terminals  178 ,  180 ,  186 ,  188  installed therein. 
       FIG. 15  is a perspective view of the butterfly assembly  105  fully seated within housing  102 . The upper and lower contacts  182 ,  184 ,  190 ,  192  of the preinstalled terminals  178 ,  180 ,  186 ,  188  are positioned above and below the contacts  160 ,  162  on contact blade  158  of butterfly assembly  105 . 
       FIG. 16  illustrates components for final assembly at the distal end of plunger  112 . An O-ring  194  is seated in a groove  196  in housing  102  that is provided around plunger  112 . A washer  198  and a return spring  200  are placed over the distal end of plunger  112 . A spring cap  202  and lock ring  204  are next installed over the distal end of plunger  112 , with lock ring  204  seated in circumferential depression  120 , thereby holding return spring  200  in operating position between housing  102  and spring camp  202 . 
       FIGS. 17 and 18  illustrate a step in the completion of housing  102  from different angles. A cover piece  206  having weld grooves  208  is positioned over the open switch assembly.  FIG. 19  illustrates the switch after the cover has been sonically welded in place. To provide an environmentally sealed switch, seal compound  210  is injected through a seal port  212  in housing  102 . Terminal screws  214  are shown attached to the terminals. 
       FIG. 20  shows further detail of the flow of seal compound  210  within the switch  100 . 
     In the assembled condition for switch  100 , snap blade  108  is disposed between an upper blade wedge  216  and a lower blade wedge  218 , and snap blade  110  is disposed between an upper blade wedge  220  and a lower blade wedge  222 . Blade wedges  216 ,  218 ,  220 ,  222  operate together with the movement of butterfly assembly  105  to impart forced movement of contact blade  158  in both directions via snap blades  108 ,  110 . Blade wedges  216 ,  218 ,  220 ,  222  can be integral formations created during molding of load switch housing  102 . Accordingly, blade wedges  216 ,  218 ,  220 ,  222  are rigid and strong. 
       FIG. 21  illustrates switch  100  in a so-called “free position.” The normally closed lower terminals  186 ,  188  are in contact with lower contacts  162  of contact blade assembly  150 . Two of the lower contacts  162  at one end of contact blade  158  are in electrical contact with lower terminal contact  190  of lower terminal  186  and two lower contacts  162  at the opposite end of contact blade  158  are in electrical contact with lower terminal contact  192  of lower terminal  188 . 
       FIG. 22  illustrates switch  100  at an operating condition with plunger  112  having been depressed. Snap blades  108 ,  110  which extend angularly outwardly and upwardly from grooves  174 ,  176  toward the shaped, notched distal ends  129 ,  131  of spring  114  in the free position have been flattened in the operating condition when plunger  112  has been depressed, which in turn moves all of plunger assembly  104  downwardly. The flat blades  108 ,  110  are ready to snap the mechanism to a second position by elevating blade shuttle assembly  106 . If the contacts have become welded due to load and arcing, snap blades  108 ,  110  wedge and force transfer, to break the welds. The C-spring provides transfer snap by loading the snap blades inwardly. 
       FIG. 23  illustrates switch  100  in a so-called “reset” position in which upper contacts  160  are in electrical contact with upper terminal contacts  182 ,  184  of upper terminals  178 ,  180 . Plunger  112  has been released, and is returned to its elevated position by return spring  200 , thereby raising all of shuttle assembly  104 . Two upper contacts  160  at one end of contact blade  158  are in electrical contact with upper terminal contact  182  of upper terminal  178  and two upper contacts  160  at the opposite end of contact blade  158  are in electrical contact with upper terminal contact  184  of upper terminal  180 . Blade shuttle  152  has been elevated so as to elevate contact blade  158  toward upper terminals  178 ,  180  to place the pairs of upper contacts  160  against the upper terminal contacts  182 ,  184   
       FIG. 24  is a cross-sectional view of the switch at the reset position, as shown in  FIG. 23 . 
       FIG. 25  is a perspective view of a modification for the blade shuttle assembly. A contact blade assembly  250  thereof includes electrically isolated upper and lower contact blades  258 ,  259 . Insulation material can be provided between upper and lower contact blades  258 ,  259 . Upper contacts  260  are installed in upper contact blade  258  and lower contacts  262  are installed in lower contact blade  259 . Even if one side of the switch assembly becomes welded in either the upper or lower contact configuration such that only the opposite side operates, cross continuity does not occur because of the electrical isolation of the upper and lower contacts. 
       FIG. 26  illustrates installation of the double blade assembly in a switch  300 . The other components of switch  300  are similar to those described previously herein with respect to switch  100  and are identified with the same reference numbers. 
     The various contacts described herein, including upper contacts  160 ,  260  lower contacts  162 ,  262  and upper and lower terminal contacts  182 ,  184 ,  190 ,  192  preferably are solid silver contacts, or other high-grade electrically conductive material. In preferred embodiments therefore, contacts  160 ,  162 ,  182 ,  184 ,  190 ,  192 ,  260 ,  262  are each of convex outer shape to provide some sliding contact one against the other when electrical contact is established. Since contact blade  158  is spring mounted, some flexibility is provided whereby contact blade  158  self-adjusts while placing either upper contacts  160  thereof or lower contacts  162  thereof against upper terminal contacts  182 ,  184  or lower terminal contacts  190 ,  192 . 
     Advantages are achieved with switches in accordance with the present invention. Redundant contact points are established for each terminal contact with either two upper contacts  160  or two lower contacts  162  from contact blade assembly  150  establishing electrical contact against a terminal contact  182 ,  184 ,  190  or  192 . Using solid silver contacts allows the same switch configuration to be adaptable to low-level power applications and to high power applications. By providing convex or hemispherical contact surfaces for the stationary contact, and with the contact blade being allowed to randomly adapt to it, forces a certain amount of sliding at the point of contact while the contact is being established. Micro-sliding of the contacts is desirable for reliability by providing a micro-scouring action as the various contact surfaces slide against one another. The biasing configuration of the springs, snap blades and blade wedges provides a forced contact break in both directions. The switch therefore has high end adaptability for many uses, including handling high load levels, handling logic level loads, being totally sealed to the environment, configurable to use with multiple termination types while providing forced break in both transfer directions for added reliability. 
     Variations and modifications of the foregoing are within the scope of the present invention. It is understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned or evident from the text and/or drawings. All of these different combinations constitute various alternative aspects of the present invention. The embodiments described herein explain the best modes known for practicing the invention and will enable others skilled in the art to utilize the invention. The claims are to be construed to include alternative embodiments to the extent permitted by the prior art. 
     Various features of the invention are set forth in the following claims.