IMPROVED RELAY AND RELAY TERMINAL
Field of the Invention
This invention relates to an improved terminal for a relay, a relay incorporating the improved terminal, and a method of manufacture of a relay incorporating the improved terminal.
Background of the Invention Relays have been in use for many years.
Essentially, a relay comprises a coil energized by a control current to move an armature. When the armature moves, a moving contact connected by a moving terminal to an external circuit is moved from its normal position to its actuated position. The motion of the armature may move more than one contact. Both normally-closed and normally-open contacts are typically provided with respect to each of the moving contacts.
Such relays, being industrial products of wide applicability, are always susceptible to improvement in manufacturing, specifically those providing reduction in cost. Reduction in cost can be achieved by simplification of the manufacturing process, reduction in parts count, and the like. The present invention is directed particularly to improvements in printed circuit board relays, that is, relatively small relays carrying relatively small currents, the contacts of which are connected to the associated control and controlled circuits by connecting pins inserted directly into holes in a circuit board and soldered to conductors disposed thereon.
Object of the Invention
It is therefore an object of the invention to provide improved relays, particularly in which the cost of manufacture is reduced.
It is a further object of the invention to provide an improved method of manufacture of a relay and a terminal therefor.
Summary of the Invention
The above needs of the art and objects of the invention are met by the present invention, according to which an improved relay includes a relay terminal comprising a single piece of sheet metal formed to include an elongated connecting pin extending through a base member of the relay for connection to an external circuit element, a portion including embossed protuberances for being reliably retained in a socket formed in the relay base member, a spring portion, an upstanding portion for carrying the contact, and a bearing area for receiving force from the armature. Similar connecting pin and mounting structure can be employed in connection with the fixed contacts of the relay. The invention also includes the method of manufacture of the terminal and the method of assembly of the relay.
Brief Description of the Drawings
The invention will be better understood if reference is made to the accompanying drawings, in which:
Fig. 1 shows an elevational view, partly in cross- section, of a relay according to the invention; Fig. 2 shows a perspective view of a first embodiment of a relay terminal according to the invention, and illustrates the socket in the base member of the relay in which the terminal is retained;
Fig. 3 shows a similar view of a second embodiment of the terminal; and
Fig. 4 shows a similar view of a third embodiment of the terminal according to the invention.
Description of the Preferred Embodiments
As shown in Fig. 1, a relay comprises a base 10 molded of plastic material. Mounted to the base 10 is a motor assembly 12, including a coil winding 14 wound on a bobbin 16, and a pole piece 18. The ends of the coil winding 14 are brought out to control current connecting pins 20, one being shown in the view of Fig. 1. When a current is passed through the coil winding 14, a magnetic field extends between the ends of the pole piece 18, attracting a movable metallic armature 22 to move rightwardly in the view of Fig. 1. When armature 22 moves, a pusher rail 24 is similarly moved rightwardly, as indicated by arrow 23. An end surface 24a on the end of pusher rail 24 is urged against a bearing surface 26a on moving terminal 26. A tongue 24b on the end of pusher rail 24 may be confined in a hole 26c punched in bearing surface 26a; see Figs. 2-4. Moving contact 28 mounted on terminal 26 is accordingly moved from its normal position shown in Fig. 1, wherein moving contact 28 is in electrical contact with a normally closed contact 30, to its actuated position, in which contact 28 abuts normally open contact 32. Other arrangements for moving the moving contact 28 responsive to motion of an armature are known, and are within the scope of the invention where not excluded by the language of the appended claims. Normally closed contact 30 is supported on a terminal 34 terminating in a connecting pin 36 extending through base 10, so as to be received within a printed circuit board or other external contact device. Similarly, normally open contact 32 is carried by a further terminal 38 similarly extending through base 10 and terminating at connecting pin 38.
Thus it will be appreciated that moving contact 28 is carried by terminal 26. Terminal 26 is formed to integrally comprise bearing surface 26a for receiving force transmitted from armature 22 by pusher rail 24, as described above, and also comprises a spring portion 26b,
which flexes to allow motion of contact 28 between the normal and actuated positions, and a connecting pin 40 extending through an aperture 42 in the base 10.
Several embodiments of the relay terminal of the invention are shown in perspective view in Figs. 2-4. In each, the terminal comprises a single piece of sheet metal (e.g. 0.005" thick beryllium-copper alloy) stamped to form a terminal precursor and then formed to take the configuration shown. The terminal precursor is shaped to include an elongated portion formed to define connecting pin 40, as well as spring portion 26b and bearing surface 26a. A hole (see Fig. 1) is typically formed in bearing surface 26a to receive a rivet securing contact 28 thereto, and a further hole 26c may be provided to receive a tongue 24b on the pusher rail 24. As shown, the bearing surface 26a and the portion of the terminal 26 to which the contact 28 is mounted are essentially continuations of the spring portion 26b.
In the Fig. 2 embodiment, terminal 26 includes one or more embossed protuberances 44 protruding from one side of a planar portion 48 of the terminal 26. Protuberances 44 are formed in a central portion 48 of the terminal 26, extending transverse to the direction of elongation of the connecting pin 40, and similarly transverse to the direction of elongation of the spring portion 26b. In each of the embodiments shown in Figs. 2-4, a plurality of essentially similar protuberances are formed; their number may vary in accordance with their desired design. In each embodiment, the protuberances are formed to provide an interference fit when the terminal is inserted into a corresponding socket 54 in relay base 10, retaining the terminal in the base.
As can be further seen in Fig. 2, the elongated connecting pin portion of the terminal precursor is bent on either or both sides of its direction of elongation to form flanges 50, 52, that is, to define a flanged connecting pin 40, generally U-shaped in cross-section.
It is also within the invention to only bend the outer flange as indicated at 50; in that case the connecting pin 40 would be L-shaped in cross-section. Flanges 50, 52 significantly stiffen connecting pin 40, and improve its solderability as compared with a flat member fitting into a round hole of the same size. The flange shown at 50 extends beyond the parallel edge of the spring portion 26b as shown, in order to provide a shoulder 55 for conveniently receiving force from a press or the like urging the terminal 26 into the corresponding receptacle 60 molded* in the base 10. A second flange 56 can be formed to provide a second shoulder 57 on the opposite side of central portion 48 of the terminal 26, again to receive force urging the terminal 26 into socket 54. In the preferred embodiment, a single receptacle 60 is molded or otherwise formed in base 10 to include aperture 42, through which flanged connecting pin 40 extends, and socket 54, into which central portion 48 of terminal 26 fits. Socket 54 may be terminated by a second enlarged portion 62 for receiving the opposite flange 57 of the terminal 26. A further enlarged portion 64 may be provided in socket 54, strengthening the tooling in which base 10 is molded.
As mentioned, protuberances 44 are embossed from the sheet metal terminal precursor to an overall thickness slightly greater than the width of the corresponding portions 68 of socket 54, ensuring an interference fit therebetween. In this way, terminal 26 is securely retained within receptacle 60. Preferably, the lower surfaces of the protuberances are chamfered, radiused, or otherwise relieved, to ease their initial insertion into the corresponding socket, and so that the force required increases during their insertion. A quantity of a setting adhesive, e.g., epoxy cement, may be provided to further ensure retention of terminal 26.
As indicated in Fig. 1, the base member 10 may integrally comprise an upstanding bearing member 10a
which supports one end of the pusher rail 24. The base 10 may also be molded to include upstanding portion 10b, corresponding to the portion of base 10 shown in Fig. 2a, in which receptacle 60 is formed, and also receiving the vertically extending portions of terminal members 26, 34, and 38.
While the normally closed terminal 34 and the normally open terminal 38 are shown being formed of relatively thick material as compared to that of terminal 26, and as being simply inserted into the base member 10, it will be appreciated that terminals 34 and 38 could be made in substantially the same manner as terminal 26. That is, terminals 34 and 38 could be made by forming sheet metal precursors and bending over edges of elongated connecting pin portions to form stiffening flanges.
Figs. 3 and 4 show alternative constructions of the terminal of Fig. 2. Terminal 70 in Fig. 3 is generally similar to that shown in Fig. 2, except that the protuberances 72 are of a different, generally ovoid shape; the corresponding receptacle in the base 10 would be shaped similarly. Fig. 4 shows a further embodiment of the terminal 74, in this case including diamond-shaped or triangular protuberances 76. In other respects terminals 70 and 74 are generally similar to terminal 26 in Fig. 2.
As can be seen in Figs. 1-4, typically the moving contact 28 on terminal 26 will extend on both sides thereof, for contacting both the normally closed contact 30 and the normally open contact 32. Such double-sided contacts may be assembled to the contact-receiving portion of the moving terminal 26 in generally known manner, e.g. by assembly of contact halves having mating concentric members extending through a hole in the terminal 26 and staking, welding, soldering, or brazing the contact halves to one another, securing contact 28 to terminal 26.
The method of fabrication of a relay terminal according to the invention therefore comprises the steps of providing a relay terminal precursor, consisting of a single piece of sheet metal having a first elongated portion forming the connecting pin, a transverse body portion forming the portion inserted into the socket in the base, and a third upstanding portion forming the spring, the contact receiving area, and the bearing surface. One or both of the elongated edges of the first portion of the precursor are bent to define a flanged connecting pin 40. The protuberances are embossed in the second portion, and a second flange 56 may be formed on the end of the second portion opposite connecting pin 40. The contact 28 is mounted to the third portion. A crease may be formed between the second and third portions, to bias the moving contact toward the normally closed contact.
The completed relay terminal can then be inserted into the receptacle in the base member as indicated in Fig. 2. As indicated, shoulders 55, 57 may be formed on either end of the second portion 48 of the terminal, in which the protuberances are formed, to receive force from a press or the like urging the terminal into its position in the base. The terminal may additionally be bonded to the base by an adhesive or the like. Manufacture of the relay is completed by assembly of the other contacts, the motor assembly including the armature, and the pusher rail or another contact-activating member, all generally as in the prior art. It will be appreciated according to the invention that the contact terminal formed according to the invention is extremely simple, including a single piece of sheet metal shaped to provide a number of separate elements. Typical prior art practices involved a separate connecting pin riveted, welded, or soldered to a transverse portion for retaining the contact 28 and to a spring portion. A much simpler and less expensive relay
terminal, and an improved method of assembling a relay, are thus provided according to the present invention.
While several different preferred embodiments of the invention have been shown and described, the invention should not be limited by the above exemplary disclosure, but only by the following claims.
