US 2715169 A
Description (OCR text may contain errors)
V. L. HIGH SWITCH CONTACT Aug. 9, 1955 Filed July 21. 1950 B mM M W United States Patent SWITCH CONTACT Vernon L. High, Freeport, BL, assignor to Minneapolis- Honeyweil Regulator Company, Minneapolis, Minn, a corporation of Delaware Application July 21, 1950, Serial No. 175,i)54
Claims. (Cl. 200-166) This invention relates to switch contacts and more particularly to that type in which a disk of material having favorable contact characteristics is inlaid in and clamped in a flat holder.
This invention is an improvement in the switch contact and method disclosed in the pending application Serial No. 696,558, filed September 12, 1946, by Paul R. Enzler, and it pertains to a structure having improved means for anchoring the contact disk in place in the holder.
It has for an object to provide a switch contact having A further object is the provision of a switch structure 11;,
wherein the qualities of both the metal disk and the supporting metal are improved by a work hardening of these two metals in the successive steps in processing, to thereby lengthen the life and usefulness of the switch mechanism of which these contacts form a part.
A still further object of this invention is the provision of a contact having a pattern of serrations in and about the face of an electrical contact to work harden the metal, to improve the anchorage of said contact in place, and to improve the efliciency of the contact by reducing the area of contact to increase the unit pressure between this contact and its mating contact.
Another object is the provision of a contact structure having improved means for securing a contact in a base member without the necessity of soldering, fusing or melting, but by simple deformations in the contiguous portions of the component parts.
Further objects will be apparent from the following specification, appended claims and drawings, in which:
Figure 1 shows the concave-convex contact disk in place in a base member;
Fig. 2 shows the contact disk flattened;
Fig. 3 shows the contact disk swaged in place;
Fig. 4 shows serrations formed in the contact disk and base member adjacent the periphery of said disk;
Fig. 5 shows the top face of the contact disk provided with a pattern of serrations;
Fig. 6 is a plan of a switch contact made in accordance with this invention, and
Fig. 7 is a modified form of serration pattern.
In switch contacts it is frequently desirable to form the body of the contact member of one material to provide a contact material thereon having characteristics more favorable for making and breaking the electrical circuit. One such material is metallic silver (though others are well known), too costly for use in making an entire contact and base member. This invention provides an inexpensive method for making a contact member having a contact area of silver or the like material, and a base member of cheaper material of good electrical conductivity. Toward this end, many methods have been used employing soldering, tinning, braz- "ice ing and the like, but where the contact itself is very small, damage to the contact is highly probable by these methods. Warping, mislocation and improper bonding may result to impair the life of the switch of which the contact is a part. In this invention, the liability of warping or mislocation or improper bonding is avoided, since the steps used in anchoring the contact into the fiat base member inherently function to locate it properly, flatten it to provide a true surface for a mating contact and secure it in place. The serrating step provides restricted areas of contact and processes the materials to render the contact more resistant to curling and pulling out.
A concave-convex contact disk 13 is formed with a sharp edge 20 at the junction of the concave face and side wall. There is also formed a base member 21 of gilding metal or its equal, as shown in Figure 1 provided with a depression 22 therein. The contact disk 13 is delivered to the depression 22 in an inverted position with the concave face toward the bottom of the depression and the sharp edge 20 rests upon the bottom of this depression.
in the next step, a punch, not shown, flattens the contact disk as shown in Fig. 2, causing the side wall to assume a frusto-conical shape as at 23. In deforming the metal of this disk, the bottom face is caused to assome a surface complemental to that of the bottom of the depression so that a large area of intimate contact is had for electrical conductivity from the contact disk to the base member. in another step, a punch, not shown, produces a groove 24 in the base member adjacent to and concentric with the contact disk, and causes the metal constituting the bead. 26 to be deformed toward the contact disk to engage and overlie the frustoconical wall 23 to anchor the contact disk in place.
A further step as shown in Fig. 4 provides for a forming operation on the face of the contact disk and base member to form the serration or groove 27 in the contact disk adjacent the periphery thereof, and the serration or groove 28 in the bead 2-6 adjacent the meeting edge of the bead 26 with the contact disk 13. In this operation, the ductile metals are caused to flow toward each other under high compression to form an intimate contact between these dissimilar metals so that the entire surfaces of the side walls of the contact disk and base member depression are in contact. It is necessary that the two metals be formed against each other to provide and maintain good mechanical locking between the contact disk and the base member, because in use, the repeated heating and cooling of the contact disk in making and breaking the electrical circuit causes the metal to expand and contract. If a firm anchorage is not had, the contact disk may become loose or warp out of shape, thereby prematurely becoming damaged and useless.
When the head 26 is deformed to contact the wall of the contact disk 13, inherent strains may be set up in this metal so that when the pressure is removed, these reflux strains tend to spring the bead away from the contact disk. By providing the groove 28 in this bead, these reflex strains are minimized, as the metal in which these inherent strains exist is again deformed to remove these strains, and any new strains exist only in a thin wall in greatly reduced zones.
An alternative operation is provided as shown in Fig. 5 in which the entire surface of the contact disk 13 is deformed by a pattern of serrations 29 in addition to the serrations 27 and 23 previously mentioned. The pattern of serrations may be concentric grooves as shown in Fig. 6, or some other geometrical pattern.
By providing the plurality of concentric serrations in the face of the contact disk, or any other pattern which 3 deforms a relatively large area of this contact disk, a reduced area of contact is had with a resultant benefit of a higher unit pressure occurring between the meeting contacts. 7
The operations disclosed in the foregoing are described as successive and distinct operations. However, it will be understood that some of these steps may be combined to be performed in single operation.
In the modified form in Fig. 7, the base member 21 has the contact disk 13 flattened and anchored in place as shown in Fig. 3, but the finishing punch has ribs on its face to form the serrations 32 in the pattern of .a square. Other geometrical patterns may be followed. Where the corners of the pattern extend beyond the face of the contact disk 13 they deform the metal of the bead 26 and cause a plurality of interruptions in this bead to minimize the reflex strains in the bead as described in the foregoing.
While the progressive steps for producing a switch contact of this type have been described in the foregoing, a brief resume of these steps may be had in the following. A base of gilding metal is provided with a depression 22.
A concavo-convex contact disk 13 is placed in this depression 22 with the sharp corner v20 against the face of the depression, this disk is flattened to form a frustoconical wall on the disk, a bead of the metal comprising the base member is formed around and concentric with said contact disk, and this bead is swaged against the wall of the contact disk.
In this invention a further step provides for slitting the bead 26 by a groove 28, and for a groove 27 in the contact disk adjacent the bead 26 so that the metal of both members is swaged into a continuous, uniform mechanical intimate contact under compressive stress, strengthened to'w-ithstand the repeated expansion and contraction of the pants during the making and breaking of the electrical circuit.
The provision of a pattern of serrations, to work harden the contact disk and further squeeze it into conformity within the depression, also reduces the area of contact between this contact disk and its mating contact so that a higher unit pressure is had for .a better contact.
Having thus described this invention, I claim:
1. A switch contact of the class described, comprising a flat base member having a depression therein defined by side edges and a bottom wall, a contact disk having a frustoconical peripheral wall inlaid in said depression with the bottom of said disk engaging said bottom wall of said depression, a bead in the face of said base member adjacent said depression engaging said .fr-ustocon'ica-l peripheral wall on the contact disk, said bead having a serration formed therein between the sides thereof by plastically deforming the metal of the bead adjacent said engaging edge to secure said contact firmly in place.
2. A switch contact of the class described, comprising a base member having a depression therein, a contactdisk having a downwardly flaring side wall inlaid in said depression, a bead formed on said base member engaging and overlying said side wall of said contact disk, said contact disk and said bead having a pattern of serrations formed therein by plastic deformation of the metal to work harden the faces of said metals and .lock said contact disk securely in said base.
3. A switch contact of the class described, comprising a base member having a depression therein defined by side edges and a bottom wall, a contact disk of ductile metal having side walls sloping inwardly toward the upper face,
said contact disk being inlaid in said depression with the bottom of said disk engaging said bottom wall of said depression, a bead formed on said base member engaging and clamping said contact disk in place in said depression, and a serration in said contact disk adjacent :said bead formed by plastic deformation of the metal toward the outer edge of the disk to force said contact disk into intimate contact with the wall in said depression.
4. A composite member comprising a frus-to-conical contact and a base of conducting material receiving said contact, a portion of said base overlying the conical edge of said contact to secure the contact in said base, and a circular serrati-on formed the upper face of said contact adjacent said base in and concentric with said contact.
5. A composite contact comprising a fmsto-conical insert of contact material and a base of conducting material, a portion of said base overlying the conical edge of said insert to secure .said insert in the base, and circular serrations concentric with .said insert and substantially covering said insert and the base adjacent said insert.
References Cited .in the file of this patent UNITED STATES PATENTS 1,046,823 'McBerty Dec. 10, 1912 1,058,210 Welch Apr. 8, 1913 1,905,653 Schrauz Apr. '25, 1933 2,064,998 Waite Dec. 22, 1936 2,406,327 Friedrich Aug. 27, 1946 2,419,469 Spiro Apr. 22, 1947 2,490,020 Enzler Dec. 6, 1949 2,646,613 Enzler Iuly'28, 19'53 FOREIGN PATENTS 227,441 Switzerland Sept. 1, 1943