Electrical switch for alternating current

An electrical switch for use in alternating current circuits is constructed to provide slow contact separation and positive switch action. A pivotally mounted operating handle accepts a pivot pin at one end of a link member. A pivot pin at the other end of the link member fits into a brush lifter. Angular motion of the operating handle produces rectilinear motion in the brush lifter which results in opening and closing the switch contacts. A unique arc shield which encircles one out of each pair of contacts, protects the switch mechanism from destructive effects of contact arcing.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to electrical switches and particularly to switches 
for use in alternating current circuits. 
2. Description of the Prior Art 
Lever operated switches for use in electrical circuits are well known in 
the art. Such switches provide a convenient means for manually switching 
electrical current. 
Numerous U.S. patents have been issued which disclose lever type switches 
wherein movement of the lever acts directly on a plunger or similar member 
which in turn acts upon the electrical contacts. These patents include: 
Chebrou and Lemp--U.S. Pat. No. 1,196,662; Bissell et al.--U.S. Pat. No. 
1,465,412; Meuer--U.S. Pat. No. 1,717,057; Krieger--U.S. Pat. No. 
2,133,545; Von Hoorn--U.S. Pat. No. 2,150,013; Bentley--U.S. Pat. No. 
2,366,474; Wiggins--U.S. Pat. No. 2,578,494; and Bussman--U.S. Pat. No. 
2,880,291. 
In other instances, U.S. patents have issued for lever operated switch 
mechanisms wherein the lever acts upon a link which pivots in such a way 
so as to cause the closing or opening of the contacts. These patents 
include: Binswanger--U.S. Pat. No. 485,028; Teruzzi--U.S. Pat. No. 
2,550,623; Ranzanigo--U.S. Pat. No. 3,603,755; and Strobel--U.S. Pat. No. 
3,808,386. 
Where high currents are being interrupted by switch contacts, an arc may be 
formed at the contact surfaces, resulting in the generation of heat and 
hot gases. It is desirable to shield the remainder of the switch structure 
from the potentially destructive effects which can result from arc 
generated heat and gases. Contact shielding has been used for this 
purpose, as shown in U.S. Pat. No. 2,486,127, issued to Davies. 
The present invention seeks to improve the prior art by providing a 
relatively high current interrupting capability in a small package with a 
minimum number of parts. The parts can be easily assembled, thereby 
reducing the cost of the switch. 
SUMMARY OF THE INVENTION 
The present invention switch is operated by manually manipulating a 
pivotally mounted handle from the ON to the OFF position and vice versa. 
The action of the handle is transmitted to the contacts via a link and 
brush lifter which bears against a contact lever to open the contacts. 
Contact closure force is provided by a spring which tends to hold the 
contacts closed. This arrangement provides for an easily operated, low 
friction mechanism. 
Indexing of the handle is provided by two springs. These springs apply a 
force to the brush lifter which is transmitted through the link to the 
handle. The link pivots at each end on two pins, one of which engages the 
handle while the other engages the brush lifter. When the handle is in the 
off position, the link is nearly straightened out between the handle and 
the brush lifter. In order to prevent an accidental switch closure due to 
shock or vibration of the operating mechanism, the handle is held in the 
OFF position by virtue of the fact that the slot in the handle which holds 
one of the link pivot pins is off center with respect to the center line 
of the handle. 
When the handle is manipulated, the slot which holds one of the link pivot 
pins passes through an arc which provides a low friction method of 
changing the orientation of the link between the handle and the brush 
lifter. This arrangement minimizes the probability of the handle being 
stopped in an intermediate position between ON and OFF, thus assuring 
positive switch action. 
When switching alternating current, a slow contact separation is desirable. 
This minimizes the energy dissipated in an arc at the contacts by limiting 
arc length until the alternating current is extinguished as it passes 
through a zero point. Since contact separation in the present invention is 
caused by manual force on the handle, which is opposed by two brush lifter 
springs and a contact closure spring, the resulting contact separation 
acceleration is minimized, reducing contact speed upon separation. 
Even with a slow contact separation, arcing can occur when high currents 
are interrupted. A uniquely designed arc shield encircles one of the 
contacts in the present invention, to minimize destructive effects of 
contact arcing on surrounding structures. 
Use of the several features of the invention in combination permits the 
manufacture of a highly reliable, yet economical, switch in a compact unit 
capable of relatively high ratings, such as 60 amperes at 600 volts, AC.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to the drawings, FIG. 1 shows a three-pole switch, which is 
representative of the present invention, with the operating handle 10 in 
the ON position. The switch enclosure 12, such as of molded insulating 
material, is large enough to contain three poles. However, it will be 
understood that the invention applies as well to switches of less or 
greater complexity which contain a different number of poles. 
Faceplate 14, such as of metal, is mounted to enclosure 12 by four 
faceplate bolts 16, 18, 20 and 22. This serves to hold operating handle 
pivot pin 24 in slots 26 and 28 of enclosure 12. Mounting holes 30, 32, 34 
and 36 are provided in face plate 14, for mounting the switch on a control 
panel. 
FIG. 2 is a side elevation view of the switch of FIG. 1, showing apertures 
38, 40, and 42 through which conductors of a circuit controlled by the 
switch can be inserted. A like number of apertures is provided on the 
opposite side of the switch (not shown). Enclosure 12 is shown to consist 
of two components 12A and 12B. These enclosure components 12A and 12B and 
faceplate 14 are held together by faceplate bolts 16, 18, 20 and 22. 
Faceplate bolt 16 is shown to illustrate the method used to attach 
enclosure components 12A and 12B to faceplate 14. 
FIG. 3 is a cross section view of the switch of FIG. 1, taken through line 
III--III in FIG. 1. Link 44 is shown with pin 46 located in U-shaped 
operating handle slot 48, and pin 50 located in U-shaped brush lifter slot 
52. Operating handle 10 is shown in the ON position. When operating handle 
10 pivots on pivot pin 24, link 44 tends to straighten out between 
operating handle 10 and brush lifter 54, thus forcing brush lifter 54 away 
from faceplate 14 and toward contact levers 56, 58 and 60. Brush lifter 
springs 62 and 64 provide means for exerting a force on brush lifter 54 
which is directed toward faceplate 14 and tends to ensure positive 
operation of the operating handle. This feature is explained in greater 
detail in the description of FIG. 8. Slots 66 and 68 are provided in 
enclosure component 12A to accept mounting screws which pass through 
mounting screw holes 30 and 32 in faceplate 14. 
FIG. 4 is a side view of operating handle 10, which shows how operating 
handle slot 48 is off center with respect to center line C--C. Operating 
handle stops 11 and 13 are also shown. 
FIG. 5 is an end view of operating handle 10, showing how operating handle 
pivot pin 24 extends from both sides of the operating handle 10. 
FIG. 6 is a cross section view of the switch of FIG. 1, taken through line 
VI--VI in FIG. 1. Contact lever 70 is fixed at fulcrum 72 and carries 
movable contact 74 at the opposite end. Contact lever spring 76 exerts a 
force on contact lever 70 to maintain engagement between movable contact 
74 and stationary contact 78. It should be apparent that contact lever 70 
could be made of a spring material, thereby eliminating the need for 
contact lever spring 76. As operating handle 10 is moved from the ON 
position to the OFF position, link 44 pushes brush lifter 54 into contact 
lever 70, compressing contact lever spring 76 and separating movable 
contact 74 from stationary contact 78. Arc shield 80 which encircles 
stationary contact 78 protects structures adjacent to stationary contact 
78 from the destructive effects of heat and gases produced by an arc 
between contacts 74 and 78. A conductor connection means consisting of bus 
bar 82, conductor clamp 84, and conductor clamp bolt 86 is attached to 
stationary contact 78. A similar conductor connection means consisting of 
bus bar 88, conductor clamp 90, and conductor clamp bolt 92 is attached to 
contact lever 70 at fulcrum 72. Note that all parts of both conductor 
connection means are recessed within enclosure 12 so that no electrically 
live parts are present on the external surfaces of the switch. 
FIG. 7 is a plan view of the bottom of the switch of FIG. 1, showing 
faceplate bolts 16, 18, 20 and 22. Six conductor clamp bolts 86, 92, 94, 
96, 98 and 100 are shown to accommodate the three poles of the switch 
shown in this embodiment. 
FIG. 8 is a schematic representation which depicts the function of the 
operating handle 10 and link 44 which produces rectilinear movement of the 
brush lifter. When operating handle is in the ON position, slot 48 is 
positioned such that link pin 46 is in position A and link pin 50 is in 
position B. When the operating handle is switched to the OFF position, 
slot 48 is positioned such that link pin 46 is at position C and link pin 
50 is at position D. This results in the rectilinear travel of link pin 50 
from position B to position D, which is a distance F along center line 
E--E. Since link pin 50 is located in slot 52 of brush lifter 54, the 
brush lifter also will move a distance F. 
FIG. 8 can also be used to illustrate the slow speed contact separation 
principle of this invention and the positive switch position feature. When 
operating handle 10 pivots around pivot pin 24, link pin 46 moves along an 
arc from position A to position C. This results in the movement of link 
pin 50 from position B to position D. It should be apparent that since the 
arc length from A to C is considerably larger than the distance F from B 
to D, and each link pin travels from its ON to OFF positions in the same 
amount of time; the velocity of link pin 50 will be smaller than the 
velocity of link pin 46. Therefore, the contact separation speed will be 
less than the operating handle speed. This ensures the desired slow 
separation of contacts which is beneficial when interrupting alternating 
currents. 
The positive switch position feature of this invention is provided by the 
brush lifter springs that produce a force which is transmitted via link 44 
to operating handle 10. It should be apparent to those skilled in the art 
that when operating handle 10 pivots to the point where link 44 is in line 
with center line E--E, the mechanism is in an unstable state. That is, the 
slightest movement of operating handle slot 48 to the right or left in 
FIG. 8 will result in the operating handle 10 being driven to pivot around 
its pivot pin 24 until one of the operating handle stops 11 or 13 contacts 
faceplate 14. This ensures that operating handle 10 can only stop in the 
full ON or full OFF position. 
FIG. 9 shows the placement of insulating arc shield 80 around stationary 
contact 78. By completely encircling stationary contact 78, the arc shield 
80 provides maximum protection for structures in the vicinity of 
stationary contact 78. In this embodiment, arc shield 80 is held in place 
by virtue of the fact that the edge of the arc shield fits in a gap 
between enclosure component 12B and bus bar 82, as shown in FIG. 6. 
There has been presented a simple embodiment of this invention which 
utilizes a small number of parts, thus facilitating assembly. However, it 
should be apparent to those skilled in the art that the invention may be 
practiced in forms additional to those specifically described and 
illustrated herein. For example, link 44 and link pins 46 and 50 could be 
molded as a single piece and the link pins could pass through holes in 
operating handle 10 and brush lifter 54, rather than resting in slots as 
shown in the preferred embodiment.