US3598936A

US3598936A - Snap-acting selector switch with double acting pawl escapement mechanism

Info

Publication number: US3598936A
Application number: US840388A
Authority: US
Inventors: Myrl J Saarem; Delbert L Merriner; Woodrow W Miller
Original assignee: Richdel Inc
Current assignee: Wells Fargo Bank NA
Priority date: 1969-07-09
Filing date: 1969-07-09
Publication date: 1971-08-10
Anticipated expiration: 1988-08-10

Abstract

A snap-acting wafer switch mechanism is provided which has particular utility in selector switch circuitry, and especially in such circuitry which includes inductive means that causes the switch contacts to have a tendency to arc and burn. The snapacting control of the wafer switch of the invention causes the movable contact to move with a snap action as the switch is turned from one fixed contact to the next so that arcing is minimized, and especially in the inductive type of load circuit.

Description

United States Patent RH 1 1 i 1 inventors Myrl 1. Sum

Arletl; Delbert L. Merriner, Glendale; Woodrow W. Miller, [.05 Augeles, all oi, Calif. App]. No. 840,388 Filed July 9, I969 Patented Aug. 10, 197 l Assignee Richdel, Inc.

Los Angeles. Calif.

SNAP-ACTING SELECTOR SWITCH WlTl-l DOUBLE ACTING PAWI. ESCAPEMENT MECHANISM 5 Claims, 5 Drawing Figs.

[1.8. CI 200/18, 200/38 R Int. Cl 1101i: 3/00, HOlh 7/08,H01h 43/10 Field otSearch ZOO/33, 17, 18,11,313 B, 38 C; 74/577, 578, 576, $68; 307/14 l .4

I56] References Cited UNITED STATES PATENTS 1,979,028 10/1934 Ewart. 74/577 M X 2,613,552 10/1952 Weidenman iiiiiiiii 74/576 2.918.969 12/1959 Kull 200/38 81 3,096,408 7/1963 Brock et a1. 200/38 B 3,156,123 11/1964 Denny 74/568 T 3,198,967 8/l965 Roberts.... 44444 307/1414 3,227,823 1/1966 Acker 200/18 3,239,614 3/1966 Simmons H 200/38 B 3,496,315 2/1970 Giese,.lr.etal. 200/18 Primary Examiner-.1. R. Scott Attorney-Jessup 8: Beecher ABSTRACT: A snap-acting wafer switch mechanism is provided which has particular utility in selector switch circuitry, and especially in such circuitry which includes inductive means that causes the switch contacts to have a tendency to are and burn. The snap-acting control of the wafer switch of the invention causes the movable contact to move with a snap action as the switch is turned from one fixed contact to the next so that arcing is minimized, and especially in the inductive type of load circuit.

ATENTED AUG] 0 I97! SHEET 2 OF 3 BACKGROUND OF THE INVENTION The selector switch mechanism of the invention finds utility in electric programmer units, and it will be described in such an environment. It will become apparent as the description proceeds, however, that the switch has general utility in selector switch circuits in which a movable contact is caused to contact successively a plurality of fixed contacts to cause different circuits selectively to be energized.

Such an electric programmer is described, for example, in US. Pat. 3,101,4l8, which issued Aug. 20, 1963, and which is assigned to the present assignee. The particular programmer unit described in the aforesaid patent is one in which a relatively simple electric programming unit is used to control automatically a number of electrically operated valves in a sprinkler system. The programmer described in the patent includes a controlled wafer-type selector switch which is effective to cause different valve circuits to be energized in a sequential manner and automatically on a day-by-day basis.

However, in order to avoid undue arcing at the contacts of the prior art wafer-type selector switch due to the inductive nature of the load, a relatively complex switching system is used in the unit described in the patent, and which assures that the wafer switch is first operated from one contact to the next, before a second switch actually causes current to pass through the wafer switch.

By use of the snap-acting wafer selector switch of the present invention, the need for the extraneous circuitry described in the patent is obviated, and the wafer switch itself may be used to perform the current switching function.

The invention provides, therefore. a snap-acting wafer-type switch mechanism which is effective to minimize contact burning, especially with inductive loads. The switching mechanism to be described includes a double-acting pawl which function as an escapement mechanism, first to release the switch armature and then to stop it after it has moved through a predetermined angular distance. Under the control of the double-acting pawl, the movable contact of the switch breaks with the previously engaged fixed contact with a snap action, and it moves half way through the angular distance to the next fixed contact. Then, the action of the double-acting pawl causes the switch armature again to be released and move the movable contact into electrical engagement with the next fixed contact, also with a snap action.

By the action described in the preceding paragraph, the switching mechanism of the invention assures that a circuit energized by a particular position of the armature of the switch, is deenergized before the next circuit is energized thereby. This prevents the two circuits being energized at the same time, which could result in excessive loading on the system. For example, when the switching mechanism of the invention is used in a sprinkler system, it permits one valve to be turned off before the next is turned on, so that full fluid pressure may be maintained at all times.

A feature of the improved wafer snap-acting switch of the present invention is that it is extremely simple from a mechanical standpoint. Moreover, the improved snap-acting wafer switch of the invention simplifies the mechanical components and associated electric circuit when, for example, the mechanism is incorporated into a programmer unit of the general type described in the aforesaid patent. Specifically, when the snap-acting wafer selector switch of the invention is incorporated into such a programmer unit, it vastly reduces the complexity and cost of the unit and also improves its performance.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a rear view showing the improved switching mechanism of the present invention mounted on a panel and incorporated into a programmer;

FIG. 2 is a front view of the programmer unit of FIG. I;

FIG. 3 is a side view of the unit taken line 3-3 of FIG. 1;

FIG. 4 is a detailed section of certain components of the switching mechanism in an expanded condition; and

FIG. 5 is a circuit diagram of an appropriate programmer in which the snap-acting wafer switching mechanism of the invention may be incorporated.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT As shown in FIGS. 1-3, for example, the switching mechanism of the invention and associated components may be mounted on a stationary support such as a panel [0. The mechanism includes a usual selector multicontact leaf switch 12 which is mounted on the stationary support It! by means, for example, of a mounting bracket 14. The leaf switch 12 includes a plurality of fixed contacts 16 to which appropriate electrical connections, such as the connection 18, may be made, and it also includes a movable contact 20 which is mounted on a drive shaft 12. As the drive shaft 22 is rotated, the movable contact 20 is caused to move from one of the fixed contacts 16 to the next, so as to establish selective electric contact with the successive fixed contacts.

A ratchet wheel 24 is keyed to the drive shaft 22, and it is engaged by a double-acting pawl 26, the pawl being pivotally mounted on the stationary support 10 by means, for example, of a screw 28. The double-acting pawl 26 forms an escapement mechanism with the ratchet 24, and the action is such that when the pawl is set in the angular position shown in FIG. 1, rotation of the ratchet wheel 24 and of the movable contact 20in the clockwise direction is prevented. A drive gear 30 is rotatably mounted on a bushing on the shaft 22 and, as shown in FIG. 4, for example, is coupled to the shaft by means of a coil spring 32, so that rotation ofthe drive gear 30 causes it to exert a resilient torque on the drive shaft 22 which, in turn, biases the ratchet wheel I! and the movable contact 20 in the clockwise direction.

Now, when the pawl 26 is released by an engagement of a protruding portion 260 of the pawl, as will be described, it moves in a clockwise direction to release the ratchet wheel 24. The ratchet wheel then turns through a limited angular distance until its next sprocket engages the right-hand end of the pawl in FIG. I. When that occurs, the movable contact 20 has moved half thedistance from the fixed contact [6 previously engaged by it, and the nextfixed contact 16. Then, when the pawl is returned in a counterclockwise direction to the position shown in FIG. I, the ratchet wheel moves through a further angular distance, so that the movable contact 20 is caused to engage the next contact 16.

Therefore, each time the pawl 26 is actuated and released, the movable contact 20 moves with a snap action to break the previously engaged fixed contact 16, and to establish itself at a distance midway between that contact and the next. Then, when the pawl is returned to its original position, the movement is completed, and the movable contact engages the next fixed contact, also with a snap action. In this way, and as described above, it is assured that the energized circuit is first broken, before the next circuit is energized. Also, it will be appreciated, that each time the pawl 16a is actuated, the movable contact moves with a snap action due to the bias force exerted on it by the spring 32.

In order to actuate the pawl 26, a program wheel 50 is mounted on a bushing on the drive shaft 22 on the opposite side of the panel ill from the components described above, and the drive gear 30 is also mounted on the bushing. The program wheel 50 turns with the drive gear 30. The program wheel includes a plurality of adjustable radial stops 52 which may be set to any desired angular position around the periphery of the program wheel 5'0. When any one of the stops 52 engages the projecting portion 26:: of the pawl 26, the pawl is actuated as deseriud above. As mentioned. the steps 52 may be manually set to any desired position around the program wheel 50, so that as the program wheel is rotated, the pawl is actuated at desired times.

essentially along the The drive gear 30 is coupled to a further gear 60 which is mounted on an idler shaft 62 with a pinion 64. A clock motor 66 is mounted on the stationary support 10, and a pinion 68 on the drive shaft of the clock motor is coupled to a gear 70. The gear 70 is mounted on a shaft 72, together with a segmented gear 74, the latter gear being mounted on the opposite side of the panel II] from the clock motor 66 and gear 70, as shown in FIG. 2.

The clock motor 66 may drive the gear 70 at a particular rate of, for example, one revolution per day, so that the segmented gear 74 rotates at the same rate. The segmented gear 74 may include segments 76 which are mounted on the segmented gear by means, for example, of screws 78. The segments 76 are of a particular arc length to cause a complete revolution of the drive gear 30 during the engagement of each segment with the pinion 64. As shown in FIG. 2, two segments 76 may be provided to cause the drive gear 30 to make two revolutions per day, one during some 6-hour interval, and another at some other 6-hour interval, as determined by the position of the segments. This causes successive solenoid valve control circuits to be turned on and off, for example, during each of the aforesaid 6-hour intervals.

As shown in FIG. I, for example, a microswitch 80 may be mounted on the stationary support 10 to be operated each time the pawl 26 is actuated. This switch, for example, may be used to control a signal, or any other appropriate device to indicate each time a circuit is activated or deactivated by the control mechanism.

The mechanism described above may be incorporated into an electric circuit, such as shown in FIG. 5.

The electrical system includes, for example, a connector strip 82 which includes a first pair of terminals A and B which are connected to the usual llO-volt source. When so connected, a transformer 84 is energized, and it develops an appropriate voltage for the clock motor 66 across its secondary. The clock motor is in the primary circuit of the transformer, and it is energized whenever the I l-volts is applied to the terminals A, B, at the same time the primary winding of the transformer is energized. The secondary circuit of the transformer is energized by closing a switch 86, causing current to flow through a fuse 88.

When the clock motor is energized, the movable contact 20 of the snap-acting wafer switch is caused to move from one fixed contact to the other, as described above, providing selective connections between the common terminal C and switching terminals D, E, F, G, H and .l on the terminal strip 82. The microswitch 80 is actuated each time the wafer switch 16 is operated, providing for a connection between, for example, the terminal A and a further terminal K. It will be appreciated that any signalling device connected across the terminals K and B will be energized by the l l0-volt AC current whenever the switch is operated.

The circuit of FIG. 5 is extremely simple in that all the electrical switching connections are performed by the selector switch itself, due to its snap-acting feature, so that additional switching circuitry is unnecessary. The switching mechanism itself is relatively simple and may be constructed at a relatively low cost. The clock motor could be placed in the secondary circuit in position to stop whenever the fuse 88 is blown. The position of the selector switch at that time will indicate which valve circuit cause the failure.

What we claim is:

l. A snap-acting switching mechanism including: a stationary support means; a drive shaft extending through said support means; a plurality of fixed electrical contacts mounted on said support means at spaced angular positions about the axis of rotation of said drive shaft; a movable electrical contact mounted on said drive shaft in position to engage said fixed electrical contacts successively upon rotation of said shaft; a ratchet wheel keyed to said shaft and having sprockets extending radially therefrom; a drive wheel mounted coaxially with said drive shaft for rotation relative thereto and about the axis of rotation thereof; resilient means coupling said drive wheel to said ratchet wheel for exerting a resilient torque on said ratchet wheel upon rotation of sat drive wheel; and a doubleacting pawl pivotally mounted as an escapement on said support means in position selectively to engage said sprockets of said sprocket wheel, said pawl permitting said ratchet wheel to move with a snap action through a limited angular distance when said pawl is first actuated to be released from one of said sprockets and so as to cause said movable contact to snap out of engagement with one of said fixed contacts, and said pawl permitting said ratchet wheel to turn through a further limited angular distance with a snap action when said pawl is subsequently actuated to engage the next sprocket on said sprocket wheel so as to cause said movable contact to snap into engagement with the next of said fixed contacts.

2. The combination defined in claim 1, and which includes a programming means coupled to said drive wheel for actuating said pawl as said drive wheel is turned to predetermined angular positions.

3. The combination defined in claim 2, in which said programming means comprises a control wheel affixed to said drive wheel and coaxial therewith, and radial stops extending out from said control wheel selectively to engage said pawl as said control wheel turns with said drive wheel.

4. The combination defined in claim 3, in which said stops are adjustable to selected angular positions.

5. The combination defined in claim I, and which includes a spring-loaded switch mounted on said stationary support means in position to be actuated by said pawl.

Claims

1. A snap-acting switching mechanism including: a stationary support means; a drive shaft extending through said support means; a plurality of fixed electrical contacts mounted on said support means at spaced angular positions about the axis of rotation of said drive shaft; a movable electrical contact mounted on said drive shaft in position to engage said fixed electrical contacts successively upon rotation of said shaft; a ratchet wheel keyed to said shaft and having sprockets extending radially therefrom; a drive wheel mounted coaxially with said drive shaft for rotation relative thereto and about the axis of rotation thereof; resilient means coupling said drive wheel to said ratchet wheel for exerting a resilient torque on said ratchet wheel upon rotation of said drive wheel; and a doubleacting pawl pivotally mounted as an escapement on said support means in position selectively to engage said sprockets of said sprocket wheel, said pawl permitting said ratchet wheel to move with a snap action through a limited angular distance when said pawl is first actuated to be released from one of said sprockets and so as to cause said movable contact to snap out of engagement with one of said fixed contacts, and said pawl permitting said ratchet wheel to turn through a further limited angular distance with a snap action when said pawl is subsequently actuated to engage the next sprocket on said sprocket wheel so as to cause said movable contact to snap into engagement with the next of said fixed contacts.

2. The combination defined in claim 1, and which includes programming means coupled to said drive wheel for actuating said pawl as said drive wheel is turned to predetermined angular positions.

5. The combination defined in claim 1, and which includes a spring-loaded switch mounted on said stationary support means in position to be actuated by said pawl.