The invention relates to electrical switches, and more particularly to an electrical switch assembly including a bridging contact which is carried by a moveable shaft that selectively bridges a gap between spaced terminals depending on a position of the shaft.
Electrical switches using push button or plunger type switch actuators have many applications including use in automobile car doors, ignition circuits, power take-offs for lawn mowers and the like. These push buttons may be normally open, normally closed or a combination of the two.
It is possible to construct switches having more than two terminals which combine the features of normally open and normally closed switches. For example, a “double-pole double-throw” switch behaves as a normally open switch and a normally closed switch in parallel operated by a single plunger. When the plunger is in a normal position, one pair of normally closed terminals is bridged and a pair of normally open terminals is isolated. Alternatively, when the plunger is moved to an actuated position, the normally open terminals are bridged and the normally closed terminals are isolated. A “single-pole double-throw” switch behaves like a double-pole double-throw switch in which one of the normally open terminals is coupled to one of the normally closed terminals. When the plunger is in the normal position, a common terminal is bridged with a normally closed terminal while a normally open terminal is isolated. Alternatively, when the plunger is in the actuated position, the common terminal is bridged with the normally open terminal while the normally closed terminal is isolated.
Several proposals have been made with respect to switches in which torsion springs, leaf springs or “V”-springs are carried by plungers and used to bridge gaps between spaced terminals when the plungers are appropriately positioned. Such springs must be secured to the plungers so that the springs do not pull loose as the plungers move them into or away from engagement with the terminals. One such proposal uses a wire torsion spring having a central coil mounted on a post projecting from a surface of the plunger. An advantage of this mounting technique is that the spring may be coupled to the plunger without resort to grease to hold the parts together during assembly prior to welding. A drawback to this technique is that forming the loop which engages the post increases the cost of the spring.
U.S. Pat. No. 5,528,007 to Williams (incorporated herein by reference) concerns a plunger switch having a plunger, a retainer, a pair of terminals and an electrically-conducting wiper contact having a curved or bent middle portion defining two oppositely directed legs on either side of the middle portion. The retainer cooperates with the plunger to carry the wiper contact as the plunger moves between a normal and an actuated position. The terminals have facing contact surfaces for biased engagement with the portions of the legs exposed by the plunger and retainer to form an electrical path between the terminals when the plunger is in the actuated position. The plunger and the retainer are coupled together by arms which project from either the plunger or the retainer. The wiper contact is secured between the plunger and retainer without the need for forming a central loop in the wiper contact for engagement by the plunger.
A switch is disclosed having a switch housing defining a housing interior and an access opening that extends through a wall of the housing to the housing exterior. An actuator assembly including a shaft constrained by said housing moves along a path from a normal position to an actuated position as well as a momentary position. The shaft has an actuating portion which extends outwardly from the housing interior through the access opening. A shaft body inside the housing including a generally planar contact support that supports a number of switch contacts. A housing base positions a number of terminals having conductive surfaces for biased engagement with selected switch contacts to form an electrical path between terminals when the actuator assembly is in one of either the normal, actuated or momentary positions.
These and other advantages and features are described with reference to the accompanying drawings.
Turning now to the drawings,
An actuator assembly 20 (
A shaft body 34 disposed completely inside the housing defines a generally planar contact support 36 that supports three switch contacts 40-42 that extends through openings 37 in the contact support 36. A housing base 50 positions a plurality of terminals 60-67 having conductive surfaces inside the housing for biased engagement with selected switch contacts to form an electrical path (short) between two terminals when the actuator assembly is in one of either the normal, actuated or momentary positions.
The switch housing includes a neck portion 70 that restrains the shaft to move back and forth along an axis of the shaft neck portion. At least one spring engages the housing and the shaft body to bias the shaft into the housing. In the exemplary embodiment posts 74 extending from a surface of the shaft body 34 position two springs 75 and trap those springs between the shaft body 34 and the wall 16 of the housing.
The actuating knob 80 has an opening 80a which leads to a knob interior into which the neck portion 70 of the housing extends during assembly of the switch. The neck portion has notches 71 which key the engagement between the knob and the housing to assure the knob can only be oriented in one specific orientation with respect to the housing. The knob is coupled to and supported by the actuating portion 32 of the shaft 30. An interior surface of the knob is disrupted on opposed sides by latches having beveled portions 82 bounded by ledges 84 (
The two arms 32a, 32b that extend into the knob 80 are spaced from each other by a gap 33 that narrows as the arms flex toward each other during insertion.
An outer surface of each of the bosses has a notch at an outwardly facing corner defined by the surfaces 97, 98. The bosses further define ledges 96, 99 that end a short distance below a middle, raised portion of the bosses. The bosses 91, 92 possess a degree of flexibility. Pushing the shaft inward deflects the bosses inward as the teeth or hooks 86 bend inwardly and ride over the beveled portions 82 of the knob. During insertion the arms 32a, 32b flex toward each other. Once the shaft is seated, however, the outer surfaces of the notch defined by surfaces 97, 98 of the bosses 91, 92 prevent inward flexing of the arms and therefore strongly resist removal of the shaft from the knob.
As mentioned above, the knob 20 has three positions for selectively bridging different terminal contact combinations with one or more of the contacts 40-42.
Turning to
The generally planar section 36 of the shaft supports a generally linear array of contacts 40-42, wherein each contact is constructed from a rivet and provides the mechanism for opening or closing an associated circuit. In accordance with the exemplary embodiment shown in
A common terminal (such as the three terminals 60, 61, 62 of
The common terminal (
These contacts 40-42 are formed from metal rivets made using orbit or spin forming methods that roll the enlarged head over on the common side of the support 36 after they pushed through the openings 37 of the support 36. A length L2 (
Molding of the shaft was facilitated by inclusion of walls 113 between rivets on the actuator. The actuator is plastic and is formed by molding. Use of a mold design that forms the walls 113 helps promote uniform flow of plastic into an end region of the actuator. Additionally the walls 113 physically separate the different contacts from each other and avoid an possibility of shorting between metal terminals.
As seen in the drawings the switch 10 includes different types of electrically conductive terminals. The exemplary embodiment has a common terminal, a normally open terminal, a normally closed terminal and a momentary terminal. Each of the three types of terminals has an elongated metal leg 90 which extends from the housing base 50 and forms a part of a switch circuit controlled by the switch 10. During assembly the terminal is inserted through the base and a flexing portion 88 of the terminal bends slightly to pass through openings in the base. Once it passes through one of these openings, the flexing portion 88 snaps back to its original configuration and securely fixes the terminal to the base. The base 50 is then secured to the housing by means of ultrasonic welding or the like.
A momentary terminal 63 (
The normal or unactuated position of the switch 10 is shown in
A normally open terminal (64) has a generally flat contact engaging portion 130 supported by a doubly bent intermediate portion 132 (
The momentary and normally open terminals define notches 140, 142 bound by elongated metal strips 141, 143. The gaps extend along their respective terminals a length sufficient to isolate them from the rivet contacts with the switch assembly in the non-actuated position. Thus in the non-actuated position a contact can extend through a notch in either the momentary or normally open contact to engage the normally closed contact (if present). Furthermore, the notch 140 in the momentary contact is long enough to isolate the terminal from its associated contact with the actuator assembly in both the normal and the actuated position so that the terminal 63 is bridged only in the momentary position.
The common terminals of the switch are constructed from beryllium copper (commercially available as CL51000, 100-110 ksi tensile strength) and the regular (non-common) terminals are made from brass. One of the contacts is designed to conduct high current (15 amps) and is made from a silver copper alloy (approx 90% silver and 10% copper). The other contacts are copper rivets and are rated at somewhat less than 15 amps of current carrying capacity.
While the exemplary embodiment has been described with a degree of particularity, it is the intent that the invention include all modifications and alternations from the disclosed design falling within the spirit or scope of the appended claims.
The present application claims priority from U.S. Provisional patent application Ser. No. 60/835,309 filed Aug. 3, 2006 entitled “Plunger Switch” and which is incorporated herein by reference.
Number | Name | Date | Kind |
---|---|---|---|
3341671 | Anater et al. | Sep 1967 | A |
4839478 | Howard | Jun 1989 | A |
4894019 | Howard | Jan 1990 | A |
4924046 | Howard | May 1990 | A |
5221816 | Williams | Jun 1993 | A |
5528007 | Williams et al. | Jun 1996 | A |
5662213 | Kattler et al. | Sep 1997 | A |
5756947 | Trimble, Jr. et al. | May 1998 | A |
5775482 | Wolfe et al. | Jul 1998 | A |
5929407 | Ziem | Jul 1999 | A |
6457545 | Michaud et al. | Oct 2002 | B1 |
6618022 | Harvey | Sep 2003 | B2 |
6648092 | Michaud et al. | Nov 2003 | B2 |
7064639 | Harvey et al. | Jun 2006 | B2 |
7131509 | Harvey et al. | Nov 2006 | B2 |
7168519 | Harvey et al. | Jan 2007 | B2 |
7241958 | Pierce et al. | Jul 2007 | B1 |
20040201288 | Harvey et al. | Oct 2004 | A1 |
20060022780 | Harvey et al. | Feb 2006 | A1 |
Number | Date | Country | |
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20080029378 A1 | Feb 2008 | US |
Number | Date | Country | |
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60835309 | Aug 2006 | US |