Patent Publication Number: US-4584621-A

Title: Two or more than two poles switch means having unequal contact gaps and turn off capacities

Description:
This is a continuation of application Ser. No. 573,582, filed Jan. 23, 1984, now abandoned, which is a continuation of Ser. No. 387,142, filed June 10, 1982, now abandoned. 
    
    
     This invention relates to electrical switches and relays. More particularly, it relates to switches having two or more poles which have unequal contact gaps and unequal turn-off capacities. 
     BACKGROUND OF THE INVENTION 
     All the current switches and relays have two rated capacities, i.e., the turn-off capacity and the conductive capacity which is usually higher than the former. 
     Since the contacts or the poles of the conventional multi-pole switch or relay are all the same size, the rated capacities of the switch are based on the size of the contacts. However, the design of this invention provides for multi-pole switches which have different sized contacts, one size for each pole. Therefore, multi-pole switches of the present invention can be rated based on the size of the largest set of contacts. 
     The size of positioning of the contacts is impotant with respect to the electrical arcing which occurs between the contacts whenever they are opened or closed. Arcing can damage the contact points, reducing their electrical performance and requiring their frequent replacement. In a multi-pole switch, these problems are multiplied by the number of contact points contained therein. The present invention provides a multi-pole switch in which arcing is effectively limited to one pair of contact points. 
     SUMMARY OF THE INVENTION 
     This invention relates to a two pole or more than two poles switch means having unequal contact gaps and turn-off capacities. The contact points of every pole have a different turn-off capacity and a different contact gap so that when the switch is turned on or off, the contacts open or close sequentially thus effectively limiting arcing to one pair of contacts and thereby increasing the serviceable life and safety of the multi-pole switch. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows the sectional view of a two-pole embodiment of this invention. 
     FIG. 2 shows the perspective view of FIG. 1. 
     FIG. 3 is used to indicate the theory of operation of this invention. 
     FIG. 4 shows an embodiment of this invention being mechanically structured so as to be used as a two-pole knife switch. 
     FIG. 5 shows an embodiment of this invention being mechanically structured so as to use an air-pocket type of damping means. 
     FIG. 6 shows an embodiment of this invention being mechanically structured so as to use, as a damping means, a spring which has a constant diameter but a varying guage of wire. 
     FIG. 7 shows three embodiments of this invention being electrically structured so as to use: 
     (A) Using two driving coils having different operation time (A.C.). 
     (B) A delay circuit connected in parallel across the driving coils of the small contact point pair (D.C.). 
     (C) A spark capacitor C 2  connected in parallel across the small contact point pair (D.C. or A.C.). 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     This invention is further described in detail, by referring to the drawings attached, as follows: 
     FIG. 1 shows the sectional view of the two-pole embodiment of this invention, while FIG. 2 shows the perspective view of FIG. 1. As shown in FIG. 2, two armatures (2,2&#39;) are fixedly attached to an insulating base (1) which can move up and down. Each of the tips of said two armatures (2,2&#39;) is provided with a movable contact point (21, 21&#39;) respectively. The contact point (21) is bigger than the point (21&#39;). On another insulating base (3), two fixed conducting pieces (4,4&#39;) are provided. On said conducting pieces (4, 4&#39;), fixed contact points (41, 41&#39;), corresponding to said contact points (21, 21&#39;), are provided respectively. The contact point (41) is bigger than point (41&#39;). 
     FIG. 1 shows that the gap between the contact points (21) and (41), which form the big contact point pair, is wider than the gap between the contact points (21&#39;, 41&#39;), which form the small contact point pair. Upon the switch being turned on, said small contact point pair (21&#39;, 41&#39;) will be closed first because it has the smaller gap. At this time, no spark is generated because only one terminal of the load is connected to the power. Subsequently, said two big contact points (21, 41) are closed and they bear the spark. By the same token, when the switch is turned off, the contact points (21, 41) will be separated first to bear the spark that may occur; and secondly, the small contact points will be separated with no sparking occuring therebetween. The structure of this invention is much superior in service life and safety than the conventional switch because sparking will occur at only one pair of contact points. 
     When this invention is used for a multi-pole switch or relay, the size (capacity) of the switch is based upon the turn-off capacity of the big contact point pair only. Therefore, the small contact points may be made of a highly conductive element with a low capacity and with little spark corrosion resistance. The big contact points may be made of an alloy which has a high capacity and withstands mechanical shock and spark corrosion so as to ensure the long life and safety of the switch. 
     Since every contact point has its specific gap, all the small contact point pairs except the one biggest contact point pair, may have a spring (not shown in FIGS. 1 and 2) furnished between the movable contacts and the movable armatures or between the fixed contacts and the insulating base in order to permit all the movable contacts to move up and down nearly, in accordance together with the elasticity of the spring, during the movement of the switch &#34;ON&#34; or to &#34;OFF&#34;. 
     Since the switch in this invention has a specific turnoff sequence of its contact points, arcing is usually limited to the big capacity contact point pair. Therefore, said big contact point pair is usually installed on the live line side of a circuit. Furthermore, by means of the sequential opening and closing of the contact points, this invention may also be used as a relay which has a given operating sequence. The contact structure of this invention may also be used in the well-known field of manual switches (like knife switches), electro-magnetic switches, or relays. 
     Moreover, another feature of this invention is that, the opening or closing of the small contact point pairs may be electrically or mechanically delayed so that the turn-on speed of the switch may be expressed with an integral linear shape, and its turn-off speed may be expressed with a differential linear shape (as shown in FIG. 3A). In other words, during switch turn-off the switching speed of the small contact point pair is slower than that of the big contact point pair. Therefore, when the switch is turned off, the small contact point pair (which has a low capacity) remains in contact while the big contact point pair (which has a high capacity) opens up and neutralizes the circuit. Since the big contact point pair is the only one which bears a spark, and it has a high capacity, the time during which the switch is arcing is greatly reduced, thereby increasing the efficiency of the switch. 
     As shown in FIG. 1 and FIG. 3B, upon the swithch being turned on the small capacity contact point pair (21&#39;, 41&#39;) becomes conductive first. Since only one terminal of the load is connected, no spark is generated. Upon the switch being turned off, the big contact point pair (21, 41) is cut off first. In case the small contact point pair is opened too fast, a spark may occur between the small contact points (21&#39;) and (41&#39;) because the big contact points had not finished arcing and the small contact points were not completely cut off from the load within the given time period of time. 
     Therefore, a further feature of this invention is that, upon the switch being turned off, the cutting off operation of the small contact point pair should be slower by over 8.6 ms (Since the frequency of power line is 60 HZ per second, one half cycle is about 8.6 ms) than the big contact point pair. Therefore, the small contact point pair should remain in contact during the time it takes the big contact point pair to drop below the zero voltage level in order to completely eliminate the spark or arc in the small contact point pair. Then, the small contat point pair can be cut off without generating any spark because of having no load to be cut. (as shown in FIG. 3B). 
     The means by which the small or big contact point pair may be electrically or mechanically delayed when opening or closing are described below: 
     
         __________________________________________________________________________
                                      FIG.
Type  No.
         Structure           Used for Referred
__________________________________________________________________________
Mechanical
      1  An opposite concavo-convex mechanical
                             Knife    4
         damping structure between the knife
                             Switch (Man-
         and the pivot piece of a knife switch.
                             ual switch)
      2  Air-pocket type of damping means.
                             Electro-magnetic
                                      5
                             switch or relay.
      3  Two or more springs which have
                             Electro-magnetic
                                      6
         equal diameter with different
                             switch or relay
         gauged wires.
Electric
      4  A.C. Two or more sets of driv-
                             Electro-magnetic
                                      7A
         ing coils which have different
                             switch or relay
         operation times.
         D.C. A delay circuit connected
                             Electro-Magnetic
                                      7B
         in parallel across the driving
                             switch or relay
         coil of the small contact points.
         A.C. or D.C. An spark capacitor
                             Electro-magnetic
                                      7C
         connected in parallel across the two ends
                             switch or relay
         of the small contact points.
__________________________________________________________________________
 
    
     The aforesaid means are further described in accordance with the numbered sequence in the table above as follows: 
     1. As shown in FIG. 4A, a mechanical damping structure is used in a knife switch. At both sides of the knife feet (51, 51&#39;) and near the joint to the pivot pieces (6, 6&#39;) and (7, 7&#39;), four pits (53, 53&#39;) and (54, 54&#39;) are furnished. On the surface of the pivot piece that is opposite to said pits, four salient half beads (61, 61&#39;) (71, 71&#39;) are furnished correspondingly. Said two knife feet (51, 51&#39;) are respectively pivoted between said pivot pieces (6, 6&#39;), and said pivot pieces (7, 7&#39;). When the knife is moved along and arc under the salient half-beads of the pivot pieces come into contact with the pits of knife feet, a slightly mechanical damping or delaying effect will be resulted. 
     Where the position of the salient half-beads of the pivot pieces has approximately been arranged, the contact point (8) (corresponding to the small contact point pair) will, during the closing of the knife switch, be contacted first because the front end of the blade (52&#39;) of the knife is wider than that of (52). When the pit of the knife foot and the salient half-bead of the pivot piece make contact, a mechanical delaying effect will result for a short period of time; then, the other knife blade (52) will contact with the contact point (9) (corresponding to the big contact point). 
     By the same token, upon turning off the switch, the contact point (9) will be cut off first, and after a given period of delay time (the delay time generated with said mechanical damping method should not be longer than 8.6 ms), the contact point (8) will be cut off. The relations of the operation speed between said contact points are shown in FIGS. 4B and 4C. 
     2. FIG. 5 shows an embodiment of air-pocket type damping means to generate the aforesaid delay function. Said means comprises an air-pocket (10) with a ventilation hole (11), a piston (12), an iron core (13), and a coil (14). Upon the piston (12) being moved up and down, as a result of the magentic force, in an air-pocket having damping effect, the big contact point fixed at the other end of said piston will be slower to come into contact when the switch is turned on. Upon the switch being cut off, the cutting off time of said small contact points (21&#39;, 41&#39;) will lag behind the cutting off time (8.6 ms) of the big contact points (21, 41) so as to obtain the results of increasing the non-arcing time and thereby increase the switch efficiency. 
     3. FIG. 6B shows a damping mechanism comprising a spring having equal diameter with different gauged wire to be used in a relay. Said spring (15) is further shown in FIG. 6A, in which the wire diameter (r a ) at terminal (a) is smaller and becomes gradually thicker and thicker till terminal (b) (i.e. r b  r a ), but the diameter (d) of the whole spring is identical. As a result, when applying an equal force to compress or to pull said spring to a given distance, the time required at terminal (a) is shorter than that of terminal (b). When the external force is removed, the returning force at terminal (b) is greater because of its wire diameter being bigger; likewise, the time required to return to the original point at terminal (b) is shorter than that of terminal (a). 
     By means of said characteristics, it could be possible to put two said springs on the two poles of a relay which has the same contact point structure as FIG. 1, and set the position of terminal (a) and (b) reversely. If the relay has more than two poles, the arrangement of said springs is based on the load cutting off condition and the characteristics of the contact points. 
     In FIG. 6B, the small contact point is turned on first when the relay is switched to &#34;N.O.&#34; contact. Upon returning to the normal state, the big contact point will turn off first. Since the force is applied to the terminal (a) of the actuating spring (15) of the small contact point pair, its actuating time required is at least 8.6 ms later than that of the big contact point. 
     4. The fourth method to obtain the same delaying function mentioned in this invention is by using electric components, which may be applied in A.C. or D.C. circuits. 
     FIG. 7a shows an A.C. circuit in which two driving coils (16,17), having different operation times, are used for driving said small contact point pair (21&#39;, 41&#39;) and said big contact point pair (21, 41) respectively. 
     FIG. 7B shows a D.C. circuit, in which a delay circuit comprising a resistor, a capacitor, and a diode, is connected in parallel to the driving coil (16&#39;) of said small contact point pair (21&#39;, 41&#39;). Upon the switch being turned on, the current will flow thru D 2  and R, and charge C 1  to the saturation state. Upon the switch being turned off, the big contact point pair (21, 41) will be cut off first, and said capacitor C 1  will, thru D 1  and the driving coil (16&#39;), discharge so as to have the small contact point pair maintained in contact by means of the discharging current thru the driving coil. When the discharging current stops flowing in said coil, the small contact point pair will be cut off. The other diode D 2  would cut off the discharge of said capacitor C 1  to the driving coil (17&#39;) of the big contact point pair. 
     Further, there is an insert AC/DC, in which an spark capacitor C 2  is connected across the small contact point pair as shown in FIG. 7C. Upon the switch being cut off, said big contact point pair will be cut off first; under these circumstances, even the small contact point pair is cut off before the big contact point pair completing arcing however, said small contact point pair will not generate any spark because of the by-pass discharging effect of said capacitor.