Reed Switch Devices

Abstract

The invention relates to a reed switch device wherein a bar magnet is mounted in such a way that the on-off switch differential is minimized. The device may be used to respond to changes in speed, pressure, temperature, or inclination.

Description

The invention relates to magnetically actuated reed switches and especially to self contained switches that are adapted to be pressure sensitive, temperature sensitive, speed sensitive, or responsive to the tilt or inclination of the switch.

In carrying out the invention there is provided a switch housing having a first compartment which contains the reed switch. A second compartment in the form of a raceway for the magnetic actuator is provided in the housing parallel to the reed switch compartment. And means are provided connected to or a part of the second compartment for moving a bar magnet placed in the second compartment relative to the reed switch so as to actuate the switch.

The reed switches herein disclosed are particularly applicable to stationary machines in which it is desired to provide means responsive to temperatures or pressure, or to machinery which tilts or rolls in which case the reed switches response to such tilt or roll.

Features and advantages of the invention may be gained from the foregoing and from the description of a preferred embodiment of the invention which follows.

In the drawing:

FIG. 1 is a sectional view of a magnetically actuated reed switch that may be mounted on a member to respond to the tilt or inclination of the member;

FIG. 2 is a sectional view of a pressure sensitive magnetically actuated reed switch;

FIG. 3 is a sectional view of a temperature sensitive magnetically actuated reed switch;

FIG. 4 is a perspective view of a governor-type magnetically actuated reed switch;

FIG. 5 is a sectional view taken along line 5-5 of FIG. 4;

FIG. 6 is a schematic representation of a flow switch employing a magnetically actuated reed switch; and

FIG. 7 is a schematic representation of a float switch embodying my invention.

Reference will first be made to FIG. 1 of the drawing which illustrates a tilt or inclination switch embodying my invention. A switch housing 10 is shown having two separate compartments, one of which 11 is provided to hold a reed switch 12. The dimensions of the compartment are such that the reed switch is snugly and securely held when placed in compartment 11. In other words, switch 12 cannot move relative to housing 10. The flexible leads 13 to the reed switch contacts exit from the housing through a niche 14 formed in the end wall 15 of compartment 11.

Housing 10 may be molded of any suitable plastic material, but a low friction one may be preferred for a reason to be made clear hereinafter. The second compartment 16 formed in housing 10 is shown with a divider section 17 that extends from the rear wall 20 of housing to the front wall (not shown). The divider section will preferably be molded integrally with rear wall 20 but lengthwise it is foreshortened compared to the length of the housing so as to provide a passageway between its ends and the ends of housing 20. Thus, compartment 16 is divided into two sections, the upper one of which may be termed a raceway 21 for a permanent magnet that is provided to actuate reed switch 12.

A front cover shaped to the elevational outline illustrated in FIG. 1 will be provided and it may be fastened to the main body of housing 10 by screws threaded into the screw holes 22. If a fluidtight housing 20 is preferred, the front cover may be secured to the housing by a suitable adhesive, or a proper gasket may be provided with the screwed on cover.

A permanent magnet 23 is provided in raceway 21. The magnet is attached and centered at each end to a ferrous ball 24 which is dimensioned to just fit within raceway 21. The balls may be secured to the magnet by magnetic attraction alone or they may be adhered thereto by a suitable adhesive. The magnet, however, is smaller in cross section than the diameter of the balls 24 so that the magnet travels in the raceway without touching any of its walls. Thus there is a minimum of friction when the manet and ball assembly moves back and forth in raceway 21. Also, if, as mentioned before, a low friction material is used for the housing, the friction is further reduced.

It should be noted that the ferrous balls serve still another useful purpose. That is, they serve to reduce the on-off switch differential. In other words, a smaller movement of the magnet 23 away from the position in which it caused the contacts of switch 12 to engage will cause the contacts to separate than if the ferrous balls were not provided. It is the weight of the ferrous balls that counters the forceful attraction to the engaged contacts of the reed switch. Without the weight of balls 24 and the air gap provided by the suspension of the magnet in raceway 21, the magnet would be reluctant to move away from the engaged contacts, or to move into position to actuate the separated contacts, except at extreme angles of tilt.

If it is desired that the switch should be a time delay switch, compartment 16 can be filled with a silicone liquid. In this way, the magnet and ball assembly will not immediately respond to a tilt or inclination of housing 20 but rather will respond after a time dependent on the relative size of the passageways provided between the ends of dividing section 17 and the endwalls of housing 10. Furthermore, if a time delay only in operating reed switch 12 is desired, an apertured reset flap valve 25 can be provided. In the FIG. 1 illustration, the movement of the magnet and ball assembly to the left, assuming a counterclockwise tilt of housing 10, will be delayed because the silicone fluid has to pass through the small aperture 26 provided in flap 25, the flap being itself immovable because its free end abuts dividing section 17. However, the rightward movement of the magnet and ball assembly is not delayed beyond the delay introduced by the use of the silicone liquid because flap 25 freely pivots about pin 27 thus allowing the silicone liquid to flow out of raceway 21.

If the switch is to operate relatively quickly and have a time delay introduced when being restored to its normal nonoperated condition, the flap 25 would be provided at the left end of housing 10 instead of at the right end, and it would abut the left end of dividing section 17. The fluid also serves to stabilize the operation of the switch by damping out vibrations that might otherwise cause unwanted operations.

The tilt switch described may be mounted directly on the machine or device whose tilt is to be monitored, or it may be mounted on a shaft and actuated by a component of that machine. In the latter case an extension 28 may be molded onto housing 10 and an aperture 29 provided therein through which a mounting shaft would pass.

Having thus described a basic magnetically actuated reed switch according to may invention, attention is directed to the remaining figures of the drawing wherein other applications of the switch are shown.

FIG. 2 illustrates a pressure sensitive switch 30. In this embodiment the switch housing 31 comprises two compartments, one, 32, for the reed switch 36, and one, 33, for the magnet 34. The housing may be molded of one piece since there is no dividing section as in the FIG. 1 embodiment. Also, the end of compartment 32 may be closed by a threaded plug 35. In this way access to the reed switch 36 is readily possible.

As before, magnet 34 is supported in compartment 33 by a pair of ferrous balls 37 which serve the same purpose as previously disclosed. A compression spring 40 is provided between magnet 34 and the closed end of compartment 33. The other end of compartment 33, i.e., housing 31, is provided with an internally threaded fitting 41 which permits attachment of switch 30 to a pressure joint which it is desired to monitor.

An apertured flap 42 may be provided if a time delay is desired after the pressure builds up but before switch 36 contacts engage. The switch can be used to monitor either liquid or pneumatic pressure due to the close fitting of balls 37 in the compartment, the balls thus serving as a piston.

Adjustment of the switch to respond to a pressure that is selectable in advance may be effected by a screw 43 that will adjust the end position of spring 40 and hence the degree of compressibility that will be required before magnet 34 moves into operating range of switch 36. Also, the position of switch 36 in the compartment can be varied.

The FIG. 3 embodiment of the invention illustrates a temperature sensitive switch 44. Again the switch housing comprises two compartments 45 and 46. Reed switch 47 is positioned in compartment 45 while magnet 50 is positioned in compartment 46. To the left of compartment 46, in the illustration, a temperature sensitive bellows device 51 is provided. Device 51 may be snapped past short flexible fingers 52 integrally formed in the interior of housing 48 to hold the device in the housing.

The housing is threaded as at 49 to permit the switch being secured to the heat source to be monitored. Of course, other securing means could be provided such as a flange which could be simply screwed to some heated element.

The magnet assembly, including magnet 50 and the two ferrous balls 53, is positioned against the plunger 54 of bellows device 51 by a light compression spring 55 whose only purpose is to keep the magnet assembly in contact with the bellows device. Thus as the bellows device expands and contracts in accordance with temperature changes, magnet 50 moves to the right and to the left in compartment 46.

The position of the magnet that will operate the switch will be dependent on the position of switch 47 in compartment 45. This of course can be made adjustable by simply sliding switch 47 to the right or to the left in the compartment.

Instead of the bellows 51 and spring 55, compartment 46 could be provided with a quantity of mercury and sealed. In this case, the switch would be mounted on end in a vertical position, and the magnet assembly would float on the column of mercury. Thus, as the mercury changed its volume in response to temperature changes, the magnet would move up and down and actuate the reed switch accordingly.

In FIG. 4 a governor-type switch 60 is illustrated. Here the switch comprises two separate housings, one of which 61 is mounted on a disc 62 that is rotatable. This housing contains the magnet assembly that includes the magnet 63 and the two ferrous balls 64 that support the magnet within the housing. A compression spring 65 urges the magnet assembly against the inner (with respect to the disc) end wall 66 of the housing. A screw 67 threaded into housing 61, which is internally threaded a substantial distance along its length, determines the initial compressibility of spring 65. By turning the screw 67 further into housing 61 a greater compression of spring 65 is obtained and hence disc 62 will have to rotate at a greater speed in order for the centrifugal force to move the magnet assembly out towards the edge of the disc. By reducing the initial degree of compression of the spring, a lesser speed of disc will throw the magnet assembly towards the edge of the disc.

The reed switch 70 to be operated by the magnet is mounted stationarily apart from the disc and the magnet 63 passes below it. The switch 70 could be mounted in a housing integral with housing 61 but in such case a pair of conducting rings (not shown) would have to be provided on disc 62 to permit connection of the reed switch contacts to external circuitry.

FIG. 6 illustrates an aerodynamically shaped vane-type flow switch which may be pivotally inserted in a conduit through which a fluid flows. The switch is quite similar in principle to the embodiment shown in FIG. 1 since, in effect, it measures the tilt of vane 72. Vane 72 is designed in turn such that its inclination is a measure of the fluid flow, i.e., velocity, past the vane. The switch comprises a reed switch 73 and a magnet assembly comprising a magnet 74 supported by a pair of ferrous balls 75 moving in compartment 76 formed in vane 72. Compartment 76 may be formed as a closed elongated loop with the magnet moving in one leg of the loop. In such a case, the compartment can be filled with a silicone liquid for purposes set forth in describing FIG. 1.

The vane 72 is provided with a mounting shaft 76 about which it pivots. The shaft may be hollow and the leads 77 from reed switch 73 passed through it to external circuitry.

In FIG. 7 there is shown a float switch embodying the principal of the invention. In the illustration a fragment of a liquid containing tank 80 is shown. An insulated fitting 81 is provided in the tank wall near the point where the liquid level is to be monitored. Two electrical terminals (not shown) are provided in the fitting so that the reed switch contacts can be connected to outside circuitry. To the terminals are connected two springs 82, 83, which serve to pivotally support the float switch 84 within the tank. As will be seen, the springs also serve as conductors for the reed switch contacts. The reed switch 85 is mounted in a block 86 of float material and its contacts are connected to the springs that support block 86. A raceway 87 is provided in block 86 adjacent to switch 85 and a magnet 90 is supported in the raceway by a pair of ferrous balls 91. The float switch and supporting springs can be designed to respond to a change from a tilted to a level position or vice versa, depending on the application for which it is provided.

Having thus described the invention, it is clear that many apparently widely different embodiments of the invention can be made without departing from its spirit or scope, and therefore it is intended that the specification and drawings be interpreted in an illustrative rather than a limiting sense.

Claims

I claim:

1. A low reluctance switch apparatus comprising a reed switch mounted for actuation by a bar magnet, a housing, a raceway formed in said housing adjacent said reed switch, and a magnet assembly positioned in said raceway for movement therealong past said reed switch, said magnet assembly comprising a bar magnet and spherically shaped means mounted at each end of said magnet for supporting said magnet in, but spaced from the walls of, said raceway, whereby the magnet assembly can move in the raceway with a minimum of friction said spherically shaped means being formed of a ferromagnetic material which in addition to adding weight to said magnet to facilitate its movement in said raceway also concentrates the magnetic flux produced by said magnet through said spherically shaped means thereby sharply defining the magnetic filed and reducing the on-off switch differential.

2. Switch apparatus according to claim 1 wherein said raceway is connected at both ends to a fluid chamber to form a closed fluid path, and including a viscous fluid in said raceway and fluid chamber whereby movement of said magnet assembly in said raceway will be impeded by the viscous fluid in the closed path to thus provide a time delay in the actuation of said reed switch.

3. Switch apparatus according to claim 2 including valve means at one end of said raceway for restricting fluid flow therein in one direction but not in the other.

4. Switch apparatus according to claim 1 including spring means mounted at one end of said raceway for biasing said magnet assembly away from a switch actuating position, and a pressure connection at the other end of said raceway for connecting said switch apparatus to a pressure source.

5. Switch apparatus according to claim 4 including valve means at said other end of said raceway for restricting movement of the pressure medium in one direction in said raceway but not in the other.

6. Switch apparatus according to claim 4 including adjustment means for varying the biasing effect of said spring means.

7. Switch apparatus according to claim 1 including a temperature sensing means mounted in the switch housing and having a member movable in said raceway in response to temperature changes, and spring means mounted in said raceway for biasing said magnet assembly against said movable member.

8. Switch apparatus according to claim 1 including a member adapted for rotary motion on which said housing is mounted with its raceway oriented in a radial direction, spring means for biasing the magnet assembly towards the inner end of said raceway, and means for adjusting the compression of said spring means.

9. Switch apparatus according to claim 1 wherein said housing is in the form of a flow vane, and including means for pivotally mounting said housing in a conduit through which a fluid flows.

10. Switch apparatus according to claim 1 wherein said housing is in the form of a float member, and including resilient means for pivotally mounting said housing to the wall of a vessel in which a liquid is stored.