US3486139A

US3486139A - Reed switch arrangement for dc magnetic circuit

Info

Publication number: US3486139A
Application number: US674781A
Authority: US
Inventors: George W Armstrong; Robert J Neff
Original assignee: ROBERT J NEFF
Current assignee: ROBERT J NEFF
Priority date: 1967-10-12
Filing date: 1967-10-12
Publication date: 1969-12-23
Anticipated expiration: 1986-12-23

Description

Dec. 23, 1969 w Ms fio g ET AL. r 3,486,139

REED SWITCH ARRANGEMENT FOR DC MAGNETIC CIRCUIT Filed 001. 12, 1967 FIG-2 FIG-1 I3 26 ,i i 75' v I f 25' I 1 1O 20 w 19 1 E I I I i IN l/E/V TORS GEORGE W. ARMSTRONG 8: ROBERT J. NEFF A TTOR/VE Y8 United States Patent US. Cl. 335-151 6 Claims ABSTRACT OF THE DISCLOSURE A reed switch is operated in response to the operation of a solenoid coil by forming a slit in the coils magnetic yoke and positioning the reed switch in the stray flux path formed at the slit.

BACKGROUND OF THE INVENTION In the application of Net]? and Armstrong, S.N. 587,132 filed Oct. 17, 1966, there are shown and claimed solenoidoperated flow control valves and circuits in which a reed type switch is positioned in closely coupled relation to the magnetic field of the coil. The reed switches in that application operate as a holding circuit for the coil, and thereby eliminate the need for separately actuated relays. The invention disclosed therein has particular utility for use in circuits and apparatus disclosed and claimed in the US. patent of Armstrong et a1. 3,082,433 of Mar. 26, 1963.

In the preferred embodiment as shown and claimed in the Nelf and Armstrong application identified above, the reed switch is positioned axially within the central opening of the solenoid so as to be subject to the magnetic field of the coil. This arrangement while having many advantages over prior art devices, often, however, results in an increase in the overall height of the coil. It also preferably utilizes a specially formed non-magnetic reed switch retainer, and potting compound or other means for securing the reed switch within its retainer, adding somewhat to the cost of the device.

SUMMARY OF THE INVENTION The present invention is directed to the combination of a reed switch and an electric solenoid having a magnetic flux guide or yoke which lowers the reluctance of the return flux path and therefore increases the efficiency of the solenoid. If a reed switch is positioned adjacent such a yoke it has been found that there is insufiicient stray magnetic field to operate the switch. In the present invention, a discrete magnetic discontinuity is formed in the yoke at a position adjacent the reed switch thereby forming a localized area of high reluctance. Preferably, this discontinuity is formed simply by cutting a small transverse slot into the yoke at a location opposite the leaves of the reed switch. This has the effect of forming discrete magnetic poles across the slot gap when the solenoid coil is actuated by a source of DC current, thereby defining a localized stray magnetic field at the gap sufficient to 0perate the reed switch. This arrangement does not materially weaken the yoke nor does it materially reduce the magnetic effectiveness of the yoke, since only a small gap or cut is necessary and since the magnetic leaves of the reed switch themselves, tend to form a path of relatively high permeability parallel to or across the gap.

It is within the scope of the invention to form such a discrete discontinuity by any suitable means, effective for the intended purpose, such as by forming a localized groove transversely of the yoke. Further, if a complete slit or gap is formed, it may be desirable to fill the gap 3,486,139 Patented Dec. 23, 1969 with non-magnetic material, such as epoxy or solder, in order to retain the integrity of the gap and prevent it from being contaminated with iron filings or the like.

It is accordingly an important object of this invention to provide a compact reed switch arrangement for electric solenoids in which the reed switch can be positioned between the yoke and the coil.

A further important object of this invention is the provision of a reed switch arrangement in association with an electric solenoid having the usual magnetic yoke, in which a discrete magnetic discontinuity or a localized area of high reluctance is formed adjacent to a reed switch for operating the reed switch by the stray magnetic field formed at such area in response to the operation of the coil.

The invention thus has particular utility in use with DC operated solenoid flow control valves, as holding circuits for valves of the general type disclosed in the above-identified Netf and Armstrong application.

These and other objects and advantages of the present invention will be apparent from the following description, the accompanying drawings and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation of a solenoid coil and reed switch arrangement constructed in accordance with this invention;

FIG. 2 is a rear perspective view of the apparatus of FIG. 1; and

FIG. 3 shows the application of such a reed switch and solenoid coil combination in a flow control valve incorporating a self-holding circuit.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings which illustrate a preferred embodiment of the invention, a solenoid is shown in FIG. 1 as having an electric coil 10 with a generally C-shaped yoke 12 partially encircling the coil 10. Thus, the yoke 12 has an upper leg 13 which extends across the top of the coil, a back 15 which extends downwardly axially of the coil and a lower leg 16 which extends across the bottom of the coil. The yoke is commonly made of suitable magnetic material, such as soft iron, forming a high permeability path exteriorly of the coil for the return of flux from one end of the coil to the other. Commonly, such electric solenoids are formed with a centrally axially formed aperture 18 therethrough for accepting a suitable armature, typical details of which are described in connection with the structure of FIG. 3.

The electric coil 10 may be of any suitable cross-sectional configuration, such as round, as sohwn, or octagonal. In either configuration, a generally wedge-shaped, axially aligning opening or clearance space is formed at 19 between the back 15 of the yoke 12 and the adjacent surface of the coil. Two such openings 19 are formed at, one on either side of the center of the coil 10. This space is normally sufficient to receive a reed switch 20 wholly therein, and inwardly of the vertical edge of the back 15. A typical reed switch suitable for this purpose may be the Form A by Hamlin, Inc., Lake Mills, Wis., and includes a pair of spaced

magnetic leaves

21 and 22 sealed within a glass envelope 23. When the switch is subject to a magnetic field, the

leaves

21 and 22 form the opposite poles of the magnet and are thus attracted together closing the magnetic and electrical circuit through the switch 20.

We have found that a reed switch of the type defined above can be effectively operated by positioning the switch axially within the recess 19, and by forming in the back 15 of the yoke 12 a discrete magnetic discontinuity adjacent the switch leaves, such as by cutting a short transverse slit 25 in the back. The slit 25 need only extend approximately the width of the reed switch and may be formed with a quite narrow gap, such as inthe order of .010 inch, or less. However, the slit 25 preferably extends a width which is greater than the transverse width of the switch 20 for ease in installing the switch but, as shown in FIG. 2, less than one-half of the width of the yoke back 15. The slit 25 thus defines in the yoke a discrete area of high magnetic reluctance. When the coil is energized from a source of DC power, magnetic poles are formed across the gap defined by the slit 25 causing a localized area of stray flux at the gap sulficient to operate the reed switch 20. The reed switch 20 may be held in position by insulating tubular coverings 26 on the ends and on the leads and by wrapping with tape, or by potting in place with a suitable potting compound, as described.

In FIG. 3 there is illustrated a pilot-valve or diaphragm type of solenoid-operated flow control valve 30 constructed according to this invention, in which like parts have been given like reference numerals as used in FIGS. 1 and 2. Thus, it will be seen that the solenoid is formed with a central opening 18 defined by tubular magnetic inserts 31 and 32 extending from the opposite ends of the opening 18, and a non-magnetic armature retainer 33 is positioned within the opening 18 and includes a sliding magnetic armature and valve member 35 formed of suitable armature material.

A simplified holding circuit for the flow control valve is somewhat diagrammatically illustrated in FIG. 3 as including a source of DC power 36 connected to be applied to the coil 10 by a switch 37. The reed switch 20 has its leads connected in parallel to the switch 37 through a circuit interrupting switch 38. Momentary closing of the switch 37 directly energizes the coil 10. The stray field at the gap 25 closes the

leaves

21 and 22 of the switch 20, forming a parallel holding circuit which will retain the coil, and the associated flow control valve in the operated condition until such time as the circuit is interrupted to the reed switch in any known and suitable manner. The switch 38 may be momentarily opened to break the holding circuit for the coil 10.

It is therefore seen that this invention provides a new combination of magnetic solenoid valve and reed switch which is compact since the switch 20 is positioned wholly within the width of the yoke 12 between the adjacent surface of the coil 10 and the inside surface of the yoke back 15.

The switch 20 is protected from damage by reason of its location between the yoke back and the coil. Also the slit 25 extends only a short transverse distance across the back and does not materially weaken the yoke nor does it materially lessen the etfectiveness of the yoke as a low reluctance magnetic path. Also, the gap defined by the slit 25 can be filled with a non-magnetic material to retain the strength of the yoke and to maintain the effectiveness of the gap, to prevent rust in the gap and to prevent bridging by magnetic particles.

It is not necessary that the switch be used to control the supply of current to the coil 10. It may be used to control apparatus or indicators, such as an indicator light, at a remote point and at a different voltage than that used to operate the coil 10. Also, the switch 20 may be for the sequential switching of a number of similarly arranged units.

While the form of apparatus herein described constitutes a preferred embodiment of the invention, it is to be understood that the invention is not limited to this precise form of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

1. The combination of a reed switch and a solenoid coil in which said coil has a yoke extending substantially to the opposite ends thereof defining a high permeability flux return path, the improvement comprising a magnetically-operated reed-type switch positioned adjacent said yoke, and means in said yoke defining a discrete magnetic discontinuity extending transversely of said return path partially the width of said yoke forming a localized region of relatively high magnetic reluctance adjacent said reed switch while not materially affecting the overall reluctance of said return path, said region of high reluctance being' sufficient to cause a stray flux field to operate said reed switch when DC power is applied to the solenoid coil.

2. The combination of claim 1 in. which said discrete magnetic discontinuity is defined by a transverse slit cut partially through said yokel 3. The combination of claim 1 in which said yoke is generally C-shaped with its opposite ends in overlying relation to the ends of the coil and with a back extending adjacent one side of the coil in which said discontinuity is formed in said back, and in which said reed switch is positioned inwardly of the outer edges of said back between said back and said coil with the leaves thereof adjacent said discontinuity.

4. The combination of a reed switch and a solenoid.

coil in which said coil has a yoke witha back portion extending substantially to the opposite ends thereof defining a high permeability flux return path for said coil, the improvement comprising a magnetically-operated reed-type switch positioned adjacent said yoke back portion, and means in said back portion defining a slit adjacent a reed switch extending transversely of said back portion a distance which is substantially less than the Width thereof and forming a localized region of relatively high magnetic reluctance sufficient to cause a stray flux field to operate said reed switch when DC power is applied to the solenoid coil.

5. The combination of claim 4 in which said yoke is generally C-shaped with its opposite ends in overlying relation to the ends of the coil and with said back portion extending adjacent one side of the coil, and in which said reed switch is positioned inwardly of an outer edge of said back portion between said back portion and said coil.

6. A combination of a reed switch and a DC operated electric solenoid valve comprising a valve coil, a generally C-shaped magnetic flux return yoke having opposite ends in overlying relation to the ends of the coil and a back extending adjacent one side of the coil, means on said back defining a magnetic gap in the order of .010 inch across and having a transverse width which is less than half that of said back, and a magneticoperated reed-type switch positioned adjacent said gap for operation with the application of DC current to said coil by the localized magnetic field formed at said gap.

References Cited UNITED STATES PATENTS 2,181,423 11/1939 Gille 335-251 X 2,778,900 l/1957 Lenning 335-154 X 3,390,361 6/1968 Bodge 335-154 X BERNARD A. GILHEANY, Primary Examiner.

R. N. ENVALL, JR., Assistant Examiner