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(11) | EP 0 181 733 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Electrosurgical switch |
| (57) @ An electrical switch assembly comprises an insulative base (10) having a power
conductor plate (12) mounted thereon and terminating in means (14) for connection
to an electrode (not shown). A pair of contact pins (16,18) are embedded in said base
and provided with means for connection to a power source. Pin (16) is in electrical
contact with and securing said plate to said base; pin (18) projects through an aperture
in the plate. An insulative casing (34) encloses said base and plate, and a resilient
conductive contact dome (36) is mounted on said plate over pin (18) and projects through
the casing. The dome (36) is capable of contacting said second pin upon being depressed,
whereby current from said power source is delivered to said electrode. |
[0001] The invention is related to an electrosurgical switch assembly making use of a resilient conductive contact dome mounted over a contact pin to establish, on depressing said dome, an electrical current to an electrode which is attached to said switch.
[0002] Electrosurgical switch assemblies for use in surgical cutting and coagulating are known. Often, such switch assemblies are disposable so that low cost construction is important.
[0003] The assembly of the invention makes use of a resilient dome which is known as such in the manufacture of switching assemblies as disclosed in U.S. Patents 3,967,084 and 4,359,614. The present assembly further makes use of low cost materials and parts which are capable of performing multiple functions as will be explained hereafter.
[0004] According to the invention, an electrical switch assembly comprises an insulative base,
a power conductor plate mounted thereon and terminating in means for connection to an electrode,
a pair of contact pins embedded in said base and provided with means for connection to a power source,
said first pin being in electrical contact with and securing said plate to said base,
said second pin projecting through an aperture in said plate,
an insulative casing enclosing said base and plate,
and a resilient conductive contact dome mounted on said plate over said second pin and projecting through said casing,
said dome being capable of contacting said second pin upon being depressed, whereby current from said power source is delivered to said electrode.
[0005] The present invention is described in detail below with reference to the drawings.
Fig. 1 is a perspective view of an electrical switch according to the invention without the insulative casing and the resilient conductive contact dome.
Fig. 2 is a perspective view of the electrical switch assembly of Fig. 1 with the insulative casing and two contact domes.
Fig. 3 is a top plan of the switch assembly in Fig. 2, partially broken away to show wire 24 and its passage, and without resilient insulative cover.
Fig. 4 is a side elevational view, partially broken away, of Fig. 3 with resilient insulative cover.
[0006] Fig. 1 shows the insulative base (10) which is the building block of the assembly receiving and locating the remaining parts of the invention. The base is made of an insulative material such as plastic, e.g. general purpose nylon plastic molding compound Zytel
[0007] A power conductor plate (12) is mounted on the base and terminates in means (14) for connection to an electrode (not shown). The plate is made from known metals or metal alloys such as copper alloys, e.g. phosphor bronze. The plate may have side panels gripping the insulative base and having fasteners therethrough such as pins to provide a reliable connection between the plate and the base.
[0008] Contact pins (16, 18, 20) act as stationary switch contacts, terminations for wires (22, 24, 26) contained in cable (28), current carriers between the wires and the power conductor plate and fasteners holding the assembly together. The pins are generally made from brass. Pin 16 is in contact with plate 12 whereas contact pins 18 and 20 are not. Apertures (30, 32) in the conductor plate avoid such contact between the plate and the pins. Pins 18 and 20 may rest on the insulative base or there may be some clearance between the bottom of pin heads 18 and 20 and the top of the insulative base. The three pins 16, 18 and 20 are embedded in the insulative base. They pierce wires 22, 24 and 26, respectively, to establish the necessary electric contact with the wires.
[0009] Fig. 2 shows an insulative casing (34) containing the insulative base (10), the power conductor plate (12) and the contact pins (16, 18, 20). The insulative material used is generally a plastic material, e.g. Surlyn . The casing provides the assembly with structural rigidity and strength. The switch assembly must be able to withstand fluids which are commonly present in the operation room, for instance, blood, alcohol, water and saline solutions, since these fluids are capable of short circuiting on penetrating the switch assembly. Because of the chemical composition of certain of these fluids, the switch assembly parts may be adversely affected due to degradation and erosion. In a preferred embodiment of the invention, the casing therefore provides fluid resistance to the assembly.
[0010] Resilient conductive contact domes (36, 38) are mounted on the power conductor plate over contact pins (18 and 20, respectively). Openings (e.g. 42) are provided in the casing to receive the contact domes so that electrical contact is established between the contact domes and the power conductor plate. The contact domes are generally in the shape of a dome having a central region of substantially planar configuration from which the remainder of the dome slants downwardly and outward to a lower rim portion. Conveniently, the lower rim portion rests on the power conductor plate to establish the necessary electrical contact with the power conductor plate. The contact domes are designed such that, on depression, the desired tactile response is attained with minimum physical space requirements. The contact dome is made of any resilient material allowing for depression of the dome to establish electrical contact with the contact pin and complete the switching circuit. A suitable material for the dome is for instance resilient stainless steel.
[0011] On depression of the dome (36) establishing electrical contact with the contact pin (18), an electrical signal is sent to a power source to which cable 28 is connected. As a result, electrical current is sent through wire 22 and pin 16 to conductor plate 12 and from there through connection means (14) to the electrode. The patient has a pad containing the other electrode underneath him and a high electrical power goes through the patient's body establishing a power circuit, as is known in the art of electrosurgical pencils.
[0012] The assembly may have a resilient insulative cover (40) mounted over the contact domes to avoid direct contact with the dome on depression thereof. The cover provides fluid resistance to the assembly. Such cover is conveniently made of the same material as the insulative casing, e.g. the above-mentioned Surlyng) material in the form of an acrylic adhesive- backed film.
[0013] Fig. 3 shows the electrical wiring of the switch of the invention. As mentioned above, wire 22 is connected with pin 16, wire 24 with pin 18 and wire 26 with pin 20. Part of the power conductor plate in Fig. 3 is broken away to show wire 24.
[0014] Fig. 4 shows the switch of the invention with the resilient insulative cover and contact dome 36 impressed to have the dome contact pin 18.
[0015] Generally, an insulative enclosure is mounted over said casing and said cover to provide an additional dielectric barrier to high voltage breakdown of the assembly and a means to comfortably hold the assembly during use. The enclosure must allow for access to the contact dome usually by having an opening at the position of the contact dome or by having resilient material at that position allowing for depression of the contact dome. Suitable materials for manufacture of the enclosure are plastic materials such as polystyrene.
[0016] It will be obvious that the assembly of the invention may have more than two contact pins. In the figures, a third contact pin 20 is embedded in the insulative base projecting through an aperture (32) in the power conductor plate, and a second resilient conductive contact dome (38) mounted on said plate over said third pin and projecting through said casing, said third pin provided with means (26) for connection to a power source of differing voltage from that of the power source connected to said second pin (18). Similarly, a fourth contact pin and a third resilient contact dome may be present. The above-mentioned resilient insulative cover may of course also be mounted over such additional contact pins.
[0017] As mentioned above, on depression of the contact dome, an electrical current is delivered to the electrode connected with the power conductor plate. As is known in the art, the electrode may be used for electrosurgical procedures such as cutting or coagulating. Dependent on the power source to which a contact pin having a contact dome is connected, different electrosurgical uses are contemplated. An electrosurgical switch having one contact dome may be used either in cutting or coagulating. A switch having two contact domes may be used for cutting and coagulating depending on which contact dome is depressed. Additional domes may be used for additional procedures.
[0018] The electrode connected to the power conductor plate may be fixedly attached to the plate or, preferably, may be removably mounted thereon. Standardized, removable electrosurgical electrodes are available on the market. The electrode's working end is shaped such that a spark is delivered to do the cutting, coagulating, etc.
1. An electrical switch assembly characterized by an insulative base (10),
a power conductor plate (12) mounted thereon and terminating in means for connection to an electrode,
a pair of contact pins (16,18) embedded in said base and provided with means for connection to a power source,
said first pin (16) being in electrical contact with and securing said plate to said base,
said second pin (18) projecting through an aperture in said plate,
an insulative casing (34) enclosing said base and plate,
and a resilient conductive contact dome (36) mounted on said plate over said second pin and projecting through said casing,
said dome being capable of contacting said second pin upon being depressed, whereby current from said power source is delivered to said electrode.
2. An assembly according to claim 1 characterized by having a third contact pin (20)
embedded in said base projecting through an aperture in said plate, and
a second resilient conductive contact dome (38) mounted on said plate over said third pin and projecting through said casing,
said third pin provided with means for connection to a power source of differing voltage from that of the power source connected to said second pin.
3. An assembly according to claim 1 or 2, characterized by having a resilient insulative
cover (40) mounted over contact domes.
4. An assembly according to claim 2 or 3, characterized in that depression of one
contact dome causes delivery of an electrical current suitable for use in electrosurgical
cutting and depression of the other contact dome causes delivery of a current suitable
for electrosurgical coagulating.
5. An assembly according to any one of claims 1 to 4, characterized in that an electrode
is mounted on said plate.
6. An assembly according to claim 5, characterized in that said electrode is removably
mounted on said plate.
7. An assembly according to any one of claims 1 to 6, characterized in that said casing
provides fluid resistance to the assembly.
8. An assembly according to any one of claims 1 to 7, characterized in that said casing
provides rigidity to said assembly.
9. An assembly according to any one of claims 1 to 8, characterized in that said casing
is enclosed by an insulative enclosure allowing for depression of said dome and providing
a dielectrical barrier to high voltage breakdown of said assembly.
10. An assembly according to claim 9, characterized in that said enclosure has an
opening at the position of the contact dome.