Electrical switch

An electric switch having contact elements designed in the form of contact pins is disclosed. Contact pins and flat springs are arranged in units, each unit having a contact pin and an associated flat spring, and each unit extending in the make/break direction of the switch. Each contact pin-flat spring unit is held between a contact carrier and a cage. The cage may be held in place by outer ends of the flat springs. A tubular conductor or a contact blade can be used as a mating contact. The mating contact is in electrical connection with the contact pins when the switch is in the make position. The individual contact elements can be easily replaced, and a standard design contact element can be used in switches of various sizes and types. A switch according to the present invention is particularly suitable for use with large surge currents.

BACKGROUND OF THE INVENTION 
This invention relates generally to electric switches, and more 
particularly to an electric switch having contact elements which are 
provided with spring members, which are arranged on at least one contact 
carrier, and which are intended to mate with a contact having at least one 
tubular conductor or at least one contact blade. 
One such conventional switch is taught in the published German Patent 
Application 11 91 465. The switch taught therein is intended for handling 
large surge currents, and has a contact comprising a slotted elastic tube. 
When the switch is in the make position, the slotted tube is mated with a 
solid contact. Once so mated, the contact segments formed by slotting the 
tube are forced against the solid contact by the inherent springiness of 
the contact segments themselves, and by forces supplied by additional 
springs. 
A switch according to this conventional design requires slotted contact 
segments which are relatively long in order that the contact segments are 
able to respond to the pressure of the additional springs. Such a 
structure creates a long current path which results in high short circuit 
forces and heat generation. Moreover, even if only one of the slotted 
contact segments becomes mechanically damaged or burned, it is necessary 
to replace the entire slotted tube. 
It is an object of the present invention to provide an electric switch in 
which the dimensions of the contact elements in the make/break direction, 
as well as in the cross-section direction, are relatively small. 
Yet another object of the present invention is to provide an electric 
switch in which individual contact elements can be easily replaced. 
Moreover, it is an object of the present invention to provide contact 
elements which can be used in switches of various sizes, and which allow 
short connections, even when used in conjunction with tubular conductors 
having large diameters. 
SUMMARY OF THE INVENTION 
According to a preferred embodiment of the present invention, contact 
elements are designed in the form of contact pins. Each contact pin is 
associated with a flat spring which extends in the circuit make/break 
direction of the switch. The flat springs and the contact pins are held 
between a contact carrier and a cage. The ohmic resistance of each contact 
pin is smaller than that of its associated flat spring. The contact 
carrier may be made of copper; the contact pins of hard electrolytic 
copper; the flat springs of slabbed spring steel wire, and the cage of 
glassfiber reinforced polyamide. 
According to a preferred embodiment of the present invention, a contact pin 
and a flat spring are mated to each other so as to form a single unit in 
order to facilitate assembly and disassembly of the switch. 
According to the present invention, each contact pin can be individually 
replaced. The dimensions of the contact pins can be kept relatively small, 
thereby permitting a standarized contact pin to be used in switches of 
various sizes. A switch according to the present invention provides a 
short current path and thus relatively small short circuit forces.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to FIG. 1, an electric switch includes a contact pin 1 having a 
recess 2, and a flat spring 9 having ends 9' and 9". The recess 2 is 
substantially larger than the thickness of the flat spring 9. The end 9' 
of the flat spring is bent so as to form a loop, and the loop is 
accommodated in the recess 2. The spring force exerted by the looped end 
9' of the flat spring against the inner surface of the recess firmly holds 
the contact pin and the flat spring together as a unit. Arranging the 
contact pin and the flat spring together as a unit facilitates assembly 
and disassembly of the switch. 
The contact pin 1 has a contact area 3 which makes contact with a contact 
carrier 6. The contact pin 1 also has a contact area 4 which makes contact 
with a tubular conductor 12 when the switch is in the make position. 
The flat springs 9 are arranged within a cage 5 which has a recess 5' and 
an outer part 5". The outer part 5", which supports the flat springs 9, is 
provided with slots and teeth 5'" so that it is designed in a comb-like 
fashion as best illustrated in the lower half of FIG. 1. The cage 5 is 
held in place by the inwardly bent ends 9" of the flat springs 9. The 
right edge of the cage 5 is thus held resiliently in place, allowing the 
cage to follow any non-coaxial position of the tubular conductor 12. 
Preferably, the cage is conical and the outer, tapered surface of the 
outer part 5" of the cage cooperates with the tubular conductor 12 so as 
to center and support the tubular conductor about the cage. 
The contact pin-flat spring units are arranged in groups of three within 
the slots of the cage 5, and several such groups are arranged at the 
perimeter of the cylindrical contact carrier 6. The contact carrier 6 
includes an annular groove 6' which accommodates the ends of the contact 
pins 1 having the contact area 3. As such, the contact pins 1 are 
swivel-mounted on the contact carrier. Swivel-mounting the contact pins in 
the groove of the contact carrier fixes the position of the contact pins 
in the make/break direction of the switch. 
The contact carrier 6 includes bores 8 which accommodate fastening bolts 7. 
The fastening bolts 7 connect the contact carrier to a first conductor 
(not illustrated). The tubular conductor 12 is connected to a second 
conductor (not illustrated). When the electric switch is in the break 
position illustrated in FIG. 1, the first conductor is electrically 
disconnected from the second conductor. As the switch goes from the break 
position to the make position, the tubular conductor 12 comes in contact 
with the contact areas 4 of pins 1. In the make position, the tubular 
conductor 12, the contact pins 1 and the contact carrier 6 form a circuit 
which electrically connects the first conductor to the second conductor. 
The contact carrier 6 may have a casing 10. The casing 10 protects the end 
of the tubular conductor when the switch is in the make position, and 
protects part of the contact pins 1. The case 10 includes a cut-out 11 
which accommodates the tubular conductor in the make position. The casing 
10 is not illustrated in the lower half of FIG. 1. 
The contact region between the contact area 3 of the pin 1 and the contact 
carrier 6 may be shaped as desired. The contact pressure between the 
contact area 3 and the contact carrier 6 is generated by the flat springs 
9. The contact pressure is increased when the switch is in the make 
position and the tubular conductor 12 is in contact with the contact areas 
4 of the contact pins and depresses the contact pins radially inwardly. 
Referring to FIG. 2, a compact electric switch includes a contact pin 1 
having a recess 2, and a flat spring 9 having ends 9' and 9". The recess 2 
is equal in size to the thickness of the flat spring, and accommodates the 
end 9' of the spring. So accommodated, the contact pin 1 and the flat 
spring 9 form a unit. 
In this embodiment, the cage includes an outer part 5" and a recess 5'. The 
contact pins 1 are held in the comb-shaped recesses 5' of the cage such 
that the outer ends 9" of the flat springs 9 rest directly at the contact 
carrier 6. 
Fastening rings 13 are accommodated in shallow grooves included in the 
contact carrier 6. Alternatively, the fastening rings can be attached to 
the contact carrier by heat shrinking. The fastening rings 13 fix the 
contact pin-flat spring units and the cage in the make/break direction of 
the electric switch. 
Referring to FIG. 3, a view through the line III--III of FIG. 2 is 
illustrated. As in the embodiment illustrated in FIG. 1, the contact pins 
1 are arranged in groups of three, and several such groups are arranged 
around the perimeter of the contact carrier 6. 
Referring to FIG. 4, another embodiment of the present invention is 
illustrated in which the flat spring 9 is bent repeatedly, thereby 
reducing the length of the switch in the make/break direction. The contact 
pin 1 is swivel-mounted in the groove 6' of the contact carrier 6. An 
outer end 9" of the flat spring 9 presses the cage 5 against the contact 
carrier 6 as well as in the direction of the contact pin 1. 
Referring to FIG. 5, another embodiment of the present invention is 
illustrated in which the contact pin includes a projection, rather than a 
recess, to accommodate the flat spring. In this embodiment, an end 9' of 
the flat spring 9 lies against a projection 14 of the contact pin 1, and a 
bent end 9" of the flat spring 9 engages a portion of the cage 5. The cage 
5 is held by the bent end 9" of the flat spring. 
In this embodiment, only one flat spring 9 is used for each group of three 
contact pins. FIG. 6 illustrates a top view of the flat spring 9. The end 
9' of the flat spring which supports the three contact pins 1 is provided 
with slots 9'" such that there are three ends 9'. Each of the three ends 
9' independently support a contact pin 1. 
Referring to FIG. 7, another embodiment of the present invention is 
illustrated in which the contact pins 1, the flat springs 9 and the cage 5 
are arranged inside a cylindrical contact carrier 6. The contact carrier 6 
is connected to a conductor part 15 by fastening bolts 7. The tubular 
conductor 12 is illustrated in the make position. 
Referring to FIG. 8, another embodiment of the present invention is 
illustrated in which two rows of contact pins 1 are arranged at a contact 
carrier 6 in mirror-image fashion. Fastening bolts 7 connect the contact 
carrier 6 with a first conductor (not illustrated). The embodiment 
illustrated is designed to serve as a contact piece for a tubular 
conductor arriving from the right. Alternatively, in place of the contact 
carrier 6 and fastening bolts 7, a circular or cylindrical contact carrier 
shorter than the axial length of the two contact elements may be used. The 
alternate embodiment would accommodate a tubular conductor at both sides, 
and thus can serve as a tubular conductor coupling. 
The two rows of contact pins are electrically connected in series. 
Alternatively, there may be more than two rows of contact pins. And, 
alternatively the pins may be arranged in a unidirectional rather than a 
mirror-image fashion. The arrangement of two or more rows of contact pins 
makes it possible for a switch having given contact element and contact 
carrier dimensions to handle larger currents, with only the first row of 
contact pins being exposed to substantial arcing. 
Referring to FIG. 9, another embodiment of the present invention is 
illustrated in which two cages 5 are connected to plate-shaped contact 
carriers 17 by dovetail joints 16. A contact pin 1 rests at a step-shaped 
rise 17' of the contact carrier 17. A flat contact blade 18 is illustrated 
in the break position. In the make position, the flat contact blade is in 
contact with a contact area 4' of the contact pin 1. Alternatively, the 
contact carrier may be ring-shaped or pot-shaped. 
The principles, preferred embodiments and modes of operation of the present 
invention have been described in the foregoing specification. The 
invention which is intended to be protected herein, however, is not to be 
construed as limited to the particular forms disclosed, since these are to 
be regarded as illustrative rather than restrictive. Moreover, variations 
and changes may be made by those skilled in the art without departing from 
the spirit of the present invention.