US1510455A - Differential-control magnet - Google Patents

Description

Oct. 7 1924.

W. W. BCHER DIFFERENTIAL -CONTROL MAGNET Filed March 20. 1919 Patented Oct. 7, 1924.

UNITED -sTATEs PATENT OFFICE.

WILLIAM W. BCHER, OF CHICAGO, ILLINOIS, ASSIGNOR, BY MESNE ASSIGNMENTS, TO KOHLER COMPANY, OF KOHLER, WISCONSIN, A CORPORATION OF WISCONSIN.

DIFFERENTIAL-CONTROL MAGNET.

Application led March 20, 1919. Serial No. 283,909.

To all whom t may concern:

Be it known that I, WILLIAM W. BCHER, citizenv of the United States, residing at Chicago, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Differential-Control Magnets, of which the following is a speciiication.

My invention relates to improvements in i. differential control magnets and it more especially consists of the features hereinafter pointed out in the annexed claims.

The purpose of this invention is to provide a super-sensitive magnet control whose responsiveness is not jeopardized by the use of very heavy currents to which the magnet may be subjected; to provide such a relation of parts that these ends will be brought about in a simple, compact and eicient man- I ner; to also provide a magnet that is readily assemblable and which may use form-wound coils; and that will provide an efficient relation of parts comprised in the magnetic circuit so as to produce the required initial I pull with very weak currents.

Withfthese and other ends in view I illustrate in the accompanying drawing such instances of adaptation as will disclose the fundamentally broad features without limit- I ing myself to the specific details shown.

Fig. 1. is an elevation in section.

Fig. 2 is a diagram of related electric circuits, in series, for automatically changing over the connections toprotect the sentitive l coil from heavy currents.

Fig. 3 is a diagram similar to that shown in Fig. 2 showing the coil windings in parallel relation to each other. i

Fig. 4 is a plan of a slotted insulating I washer.

Fig. 5 is an elevation in section of a modified core.

Magnets of the type disclosed herein are specially applicabley to the initial controlof I isolated electric generating units in which the entire starting control current is of such small amperage that the tine wire coil must have many turns to concentrate enough iuX to energize the magnet to attract its armal@ ture.

The usual pivoted armatures are liable to stick, besides requiring an excessive wattage in the coil to operate them. The type of starting currents mentioned and further exemplitied in my Patent #1,292,699 and an application Ser. 283,910 of March 20, 1919, are limited in amperes through the use of low voltage batteries of about 24 volts or even less for starting purposes. Such currents are caused to momentarily flow over the usual service mains having normal or standard voltage current consuming devices connected thereto, at about 110 or 115 volts. Plants of this kind must be started through the turning on of a single lamp of small capacity but of the same voltage as that of the service mains. This means that the total wattage at the low voltage yof the battery will be very small indeed. In order to respond to this delicate current the present magnet has been invented. It operates continuously withoutomissions, because the parts are simple and the moving portion is reduced to aI minimum weight.

The magnet windings comprise two formwound coils, the fine wire one, 24, terminating at and 36. The coarse wireU coil 31 has an inner terminal 33 to which the outer end of the tine wire coil is attached. Its outer terminal is at 32. The line Wire coil 24 is separated from the core 6 and the heavy winding 31 by insulation 25. This insulation is of the usual well known ilexible type and if desired the same may enclose the ends of this coil, so that the coil can be passed into the other winding. When so assembled the two coils can be handled as a unit. By inserting the core 6 within the yline wire coil 24 and placing insulating washer. 26 on the core at the outer end of the coils and an iron head on shoulder 28, and insulating washers 21 and 2O and 5 on the inner or armature end of the coilsl and the flat iron ring 7 pressed onto the shoulder of this end of the core the coils with the assembled parts will constitute a unit.

The magnet units are held on iianged supports having the projecting rim 3 formed of iron so as to coact with the iron head 7 to form an annular air gap 8 between them. The thick insulating washer 5 fits inside of the rim or flange 3 where it is held by screws 4. This fastening in itself would not hold the outer heads in place so a thin iron casing 3() is placed over the coils and also fastened by the screws 4. This casing has a flange 29 that engages the outer iron head 27 so as to l hold all the parts against endwise displacement. t

l'llhe support 2 may be of any desired form and it may be attached to an insulating base .1 or secured wherever desired, the only limiting condition in practice being that ample provision be made adjacent the armature stem 15 to accommodate the required electrical contacts which are to be controlled by the. magnet.

This type of a magnet supplies an ideal magnetic circuit which insures the greatest possible sensitiveness of the moving parts of the system. rlrhe magnetic circuit of the combined coils is through the core 6, outer head 27, casing 30, flange 3, across air gap 8,'and over head 7 onto the core at its armature end.

rl`he moving element of the magnet-or the armature, is made as light as possible so as to be sensitive to the weakest currents used in the fine wire coil. A guide stem 15 slides in a central hole 37 of the core 6. lt has a shoulder 12 against which a thin iron armature diaphragm 11 rests while held by nut 13. The stem 15 is threaded at 14 up to the shoulder 12 for nuts 12 and 17. The latter hold contact disk 15 in place on the stem at various distances from armature 11.

A clearance recess 9 is formed in the armature end of the core 6 to accommodate, the shoulder 12 and thus admit the diaphragm 11 to approach the flat ring 7 and the flange 3 as close as the paper or other thin insulation 10 will permit.

The armature 11, after having been initially moved into contact with the insulation 10 remains in its attracted position principally through the residual magnetism in' the adjacent iron parts. The entire magnetic circuit is then composed of highly permeable elements, since the diaphragm 11 spans the air gap 8. This insures steadiness of action under fluctuating current conditions in the magnet coils. As the coarse wire of coil 31 has but a few turns compared to fine wire coilI 24, at minimum currents within lts range the attraction of coil 31 will be small. v r.

If the initial starting demand for current is greater than that required for a single lamp the fine wire coil will be pro tected in any event against overheating because the contact plate 15 will, as soon as the diaphragm 11 has been attracted, automatically cut in the coarse wire coily 31 to carry the heavier current. When this has taken place the fine wire coil 24 may be entirely c'ut out or remain connected in parallel. Even if the coil 24 remains in parallel relation theI magnetism it can produce, on account of its high resistance will be Very small, in addition to that of coil 31, hence the residual magnetism of the parts plays a Y cooperative rle.'

The combined attraction of the two coils when they are in parallel, or of one coil alone, added to the residual effect is sufficient to hold the diaphragm 11 attracted, under extremely Weak current-s, but the initial magnetic flux would not be dense enough to produce the required magnetism to raise the armature throughout its entire distance from a position of rest. ln practice the relative resistance of the two coils has been found to be approximately of the order, 445 to .075, though any other working ratio may be employed according to the exigencies that may arise whatever ratio is selected the armature 11 must instantly drop when current is cut off from either coil and it must also be instantly attracted when the circuit is again closed but it must not drop under any other conditions.

The contact disk 15 is insulated from the threaded portion of the stem 15 by bushings 16. lt coacts in its inner or upper position with contacts 18 and inv its outer position with contacts 19. These contacts maybe used for other purposes than those herein exemplied, or more contacts and additional disks 15 may be used in any desired combination so long as provision is made for the automatic connection of the coarse wire coil after the fine wire coil has performed its lfunction. v

The magnet heads 27 and 7 have insulating washers placed between them and the coils.- Next to permeable head 27 washer 26 is found. Next to the armature end of the coil a washer 21 having an enlarged central opening 22 and a tangential slot 23 to accommodate the initial end of the coarse wire coil, is placed. This is followed by a thin washer 20 and a thick one, 5, to complete the insulation at this end of the coils.

It will be noted that on account of the carefully planned magnetic circuit a very dense field will be produced in the annular air gap 8, even with very weak currents.-

The diaphragm 11 is practically in parallel relation to the head 7 hence it becomes very responsive to the magnetic conditions ofthe air gap field.

The circuits exemplified in Figs. 2 and 3 are jvholly suggestive as they may be varied almost indefinitely. As instanced, 41 represents a motor. 42 a battery or other source of current. 43 identifies service lamps, 44 a lamp switch and 19 any desired connection to be controlled by the idle position of the diaphragm, for instance the grounding of a magneto, etc.l

When the magnet is used on a base 1, the base may serve., as a stop to the outward movement of the stem 15. The spring contacts 19 may serve the same purpose. The core 6 may have a hole throughout its length and a long` stem 38 used instead of the short stem 15. Limit nuts 39 at the outer end of lll the stem will also serve as stops to limit the movement of the armature ll-away from the magnet.

If the magnet casing 30 and the connected parts with the coil terminals protruding through the slot 34 of the casing, be mounted vertically, gravity will in all ordinary cases serve to move the armature in opposition to the pull of the magnet, but if for any reason further assistance is required on account of another position of the magnet, or because of any other condition a coil spring 40 may be att-ached to stem 15 or stem 38 at the bottom end, as suggested in Fig. 5.

What I claim is:- L

l. An electromagnet structure comprising a coil or coils constituting a unit having a core opening therethrough, a. rmeable core in such opening, insulating eads adjacent the coil supported by the core, large and reduced diameter permeable heads also supported by the core a flanged permeable support larger than the reduced diameter head so as to leave an air gap between the support -and the head, the said support being atings are assembled, permeable heads at? tached to the core, an external permeable support adjacent one of the heads forming an air gap between the head and the support, a permeable diaphragm operable across the air gap, means for controlling the movement of the diaphragm, a permeable casing surrounding the windings, a flange at one end of the same adapted to engage the other head, and means for attaching the other end of the casing to the support.

In testimony whereof I aix my signature.

WILLIAM W. BCHER.

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