US2938703A - Electromagnetic control device - Google Patents

Description

May 3l, 1960 G. E. mm 2,938,703

ELEQTROMAGNETIC CONTROL DEVICE Filed March 4, 1957 INVENToR. Gera/d E. Dlez ELECTROMAGNETIC CONTROL DEVICE Gerald E. Dietz, Milwaukee, Wis., assignor to Baso Inc., Milwaukee, Wis., a corporation of Wisconsin Filed' Mar. 4, 1957, Ser. N0. 643,840

5 Claims. (Cl. 251-129) This invention relates in general to electromagnetic devices having an armature and electromagnet and more specifically including means improving the operating characteristics thereof. In many control devices employing electromagnetic operators, the noise of operation is objectionable when said control devices are disposed in commercial and/or domestic applications. It appears that such noise is generally created by both the initial impact on attraction of the armature to the magnet core and in A.C. power devices by the vibrational forces created by the change in polarity of said alternating current.

A general object of this invention is to provide a device which employs a non-magnetic material directly within the armaturemagnet air gap to reduce impact and vibrational noise therebetween. A further object of this invention is to provide a device of the aforementioned characteristics wherein the aforementioned non-magnetic material is resilient in nature and reduces the wear on the pole faces and armature surfaces which'would be occasioned without said material.

rA further object o-f this invention is to provide a device ofthe character aforementioned wherein the resilient material takes the form of a uniform thin film that is interposed between the entire mating surfaces of the armature and magnet preventing all contact therebetween.

-A further objectl of the invention is to provide a device of the type set forth above wherein the ilm, the magnet,

and the armature have the characteristic such that after numerous cyclings ofthe armature and magnet sufficient to wear out said film, the device still remains noise-free due to self-lapping of said magnet and armature.

-Another object of this invention is to provide a device as set forth above'whe'rein the lm has the characteristics of reducing the distortion caused by impact of the yarma-V ture'and magnet, which normally tends to deleteriously affect the `mating surfaces thereof.

Another object of the invention is to provide -a device substantially as set forth-in the foregoing paragraphs wherein the resilient film is fixed relative to either the magnet or the armature to increase its operative life by avoidance of impact upon a crinkled portion of the iilm that would be created by a lrn loosely disposed between the `armature and magnet.

Another object of the invention is to provide a lm which is formed in the shape of a circular disc so as to facilitate self-centering and mounting of said disc in a circular bore during the initial assembly of the device.

Another object of the invention is to provide a device as above characterized where the film forms a nonmetallic air gap which reduces the cohesion forces between the larmature fand electromagnet and also reduces the effect of residual magnetic attractionvupon deenergization of the electromagnet.

A further object of the invention is to provide a device of the type aforementioned wherein the lm disc is composed of materials that are commercially available in 2,938,703 Patented May 3l, 1960 'ice large quantities 4at very close tolerances of thickness so that the magnetic characteristics of the device may be standardized.

A further object of the invention is to provide a control device having a non-metallic air gap which is ruggedly practical, easy to handle in mass production techniques, is non-corrosive when exposed to the ow of fluid fuel, and is otherwise well-adapted to the purposes for which it is designed.

The novel features that are characteristic of `the invention are set forth with particularity in the appended claims. 'Ihe invention itself, however, both as to its organization and method of operation, together with additional objects and advantages thereof will best be understood by the following description of a specific embodiment when read in connection with the accompanying drawings, in which:

Figure l is a view, partially in section, of applicants novel control device ina system for controlling uid fuel, the device being shown in the deenergized state, portions of said device and the system being shown semidiagrammatically;

-Figure 2 is a fragmentary sectional view of the device depicted in Figure l, the parts being shown in energized position, and

Figire 3 is a view of applicants device along lines 3-3 of Figure l. v

The precise form of electromagnet, armature, biasing spring, and valve chosen to illustrate the present invention are of the form set forth in detail in the copending application of Russell B. Matthews and Robert A. Merrell, Serial No. 499,932, filed April 7, 1955, and assigned to the assignee of the present invention.

For purposes of understanding the present invention, suffice it to say `that the electroresponsive control device 10 controls the llow of uid fuel to a main burner 11 by controlling the fluid flow in a supply conduit 12. The device 10 is here show-n in the form of `an energized-open deenergized-closed valve assembly powered by a suitable source of alternating current 13 through lines 18 having interposed therein a thermostat conventionally illustrated at 14.

More particularly, the valve assembly 10 may comprise the electromagnetic subassembly operator portion 9 and the valve portion 8. The valve portion 8 `is formed with an inlet 8a, outlet 8b and intermediate valve seat 8c.

` The operator assembly 9 may be sealingly -attached to the valve'portion 8 at 7 comprises a generally rectangular casing 23. As shown in Figure l, a generally U-shaped electromagnet 15 having pole faces 16 on the terminal surfaces of legs 15a and 15b is xedly and axially disposed within the upper portion of the casing 23. The legs 15a and 15b sealingly extend through suitable sealing material 33 into a -bore 27 formed in the lower portion of casing 23 forv coaction with a movable substantiallyv circular disc armature 19. A shading plate 31 is dis-l posed for coaction with magnet legs 15a and 15b to shift the phase of alternating current in a manner well understood in the art. y

lAs casing member 23h is provided to position the shading member 31 in operative relation lto rthe pole faces 16 and to clampingly hold the parts in assembled relation.

A suitable winding 17 is disposed'on leg 15a of magnet core 15, said winding when energized by the source of alternating current 13 through conductors 18 being v operable to attract the armature 19 against the bias of a flat spring 20. The spring 20 is of the type set forth lin detail in the aforementioned copending lapplication of Russell B. Matthews and Robert A. Merrell. For purposes of the present application, it is to be noted that -the spring 20 is a fiatl spring which may Ibe so positioned with respect to a suitable shoulder surrounding bore 27 and Aso formed with apertures or slots 26a, that upon the armature 19 being positioned in the deenergized position shown in Figure 1, the apertures or slots 20a in said spring 20 are substantially aligned and closed off by said armature 19 to prevent any substantial fuel flow into the armature pole face area within the bore 27.

Movement of the armature 1910 the attracted posi- -tion shown in Figure 2 from the retracted position shown in Figure 1 in turn causes movement of a valve member 21 which is mounted relative to the armature 19 for movement therewith by a suitable stem 30 and retainer assembly 22. It is to be noted that the connection between the stem 30 and the armature 19 is somewhat sloppy which affords a slight mass in motion effect in the initial attraction of the armature, and, also provides sufficient slop for accurate seating of -the valve upon seat 8c when the magnet is deenergized.

Means for reducing the noise ordinarily created by initial impact of the armature 19 upon the pole faces 16 of magnet 15 and for absorbing the hum or chatter occasioned by change in polarity of the A.C. winding is provided by a resilient film 25 which may comprise, for example, a polyester film having a tradename of Mylar, cellulose acetate, or cellulose nitrate. The film is preferably cut in a circular shape of slightly smaller diameter lthan the diameter of bore 27. The film is interposed directly between the pole faces 16 and the armature 19. It is to be noted that the armature 19 is circular in -form and is smaller in diameter than the disc 25. vThis relationship affords sufficient extra stock of film 25 to assure coverage of the armature even if the film disc 25 is not centered exactly within the bore 27. The disc 25 is preferably of one to three mils thickness depending upon the magnetic characteristics desired. However, this thickness -of film is on the assumption that a relatively small armature and magnet are to be used and thus is illustrative and is not intended to bein any way limiting. The disc 25, during assembly -of the device, may be ce'- mented, as at the center thereof 26, to the casing member 23b intermediate the pole faces of the magnet. The adhesive used may be as suitable and desired, one such adhesive being, Afor example, a commercially available type having a tradename Pliobond No. 20. By the cementing of the disc 25 at the point 26, kthe disc 25 is fixed relative to the ymagnet pole faces 16 and hence upon the cycling of the armature 19 there will be no tendency of the disc to move relative to the pole faces. If the disc 25 were instead loosely disposed within the vbore 27 without any fixing thereof relative to either the armature or magnet, it will Vhave the tendency to crinkle and rupture upon repeated impacts caused by cycling of the device.

It has been found, upon extensive testing, that a Mylar film of one mil thickness plus or minus .00015 tolerance will wear through at the pole face armature mating surfaces upon a cycling of between 100,000 to 200,000 times. This is equivalent of five to ten years of normal field life of the particular devices tested. After cycling said 100,000 to 200,000 times, it has been found that, the valves in which the film had worn through still exhibited no A.C. hum or chatter due to a self-lapping caused by the repeated impact of the armature 19 relative to said pole faces during said cycling. Thus, even when the lm disc 25 wears out, the device has selfeliminated the soi-called A.C. chatter or hum, the elimination of said chatter or hum being .a major desired characteristic afforded by the film in the first instance.

Another advantage of placing the film disc 25 directly between the armature-magnet mating surfaces is that it tends to reduce the abrading or eroding of the mating surfaces of the armature and magnet. Also, as shown most clearly in Figure 2, when the armature and magnet are in attracted relation, the apertures or slots 20a in flat spring 20 are distorted and no longer engage the underside of the armature 19 as shown in Figure l. However, the magnet pole faces 16 and armature 19 are clampingly engaging the disc 25 to thereby substantially protect said surfaces from possible deleterious effects from the uid fuel. Thus, as aforestated, the spring 20 and underside of armature 19 protect the armature and pole faces when the device is in a deenergized state and the disc 25 protects said surfaces when the device is energized.

It is to be further noted that the disc 25 becomes important as a non-magnetic air gap material for overcoming the effects of residual magnetism when the winding 17 of the device is powered by direct in distinction to alternating current. Since the change of polarity in A.C. power usually negates residual magnetism, this characteristic of the disc 25 is not as important in A.C. powered devices.

Having thus described a single embodiment of the resilient non-metallic air gap material and magnetic valve structure, it is to be understood that the illustrated form was selected to facilitate the disclosure of the invention rather than to limit the number of forms which the invention may assume. Various modifications, adaptations and'alterations may be applied to the specific form shown to meet the requirements of practice, Without in any manner departing from the spirit or scope of the present invention, and all such modifications, adaptations, and alterations are contemplated which may come within the scope of the appended claims. What is claimed as the linvention is:

l. A control device comprising a magnet having pole faces and armature movable between attracted and retracted positions with respect to said pole faces, and combination air gap and cushioning means comprising a thin uniform film of resilient plastic non-magnetic material having a first portion fixed relative to said magnet, said film also having a second portion interposed between and coextensive with said magnet pole faces and arma ture, whereby upon movement of said armature to attracted relation to said pole faces said film absorbs the shock of impact of said armature to thereby reduce wear of said armature and pole faces and also provides a uniform non-metallic gap therebetween.

2. A control device comprising, a source of alternating current electricity, an electromagnet energized by said source and having pole faces, an armature movable to attracted position from retracted position when said electromagnet is energized, and combination air gap and cushioning means comprising a thin uniform film of resilient `plastic non-magnetic material having a first portion fixed relative to said electromagnet, said film also having a second portion interposed between and coextensive with said magnet pole yfaces and armature, whereby upon movement of said armature to attracted relation by said energized electromagnet said film absorbs the initial shock of impact of said armature, provides a uniform non-metallic gap between armature and pole faces, and absorbs the vibrations of said armature ordinarily occasioned by the change of polarity of said alternating current.

3. A control rdevice comprising a casing having a circular bore, a magnet and circular disc armature disposed within said bore, said armature being movable axially Within said bore toward and away from said magnet, and a circular disc of resilient plastic non-magnetic material disposed transversely within and having a diameter slightly smaller than said bore, said disc having a central portion fixed to said casing and having peripheral portions interposed between and coextensive with the mating surface of said armature and magnet to prevent any direct contact therebetween.

4. A control device comprising a casing having a circular bore, a generally U-shaped magnet having a pair of legs terminating in pole faces, a circular disc armature cooperable with said magnet and movable axially within said bore toward and away from said magnet, a casing member disposed in transverse relation to said bore and having a portion intermediate said magnet leg, land a circular disc of resilient non-magnetic plastic material extending transversely within and having a diameter slightly ysmaller than said bore, said disc being centrally fixed to said casing member portion and having freely movable peripheral portions interposed between and coextensive with the mating surfaces of said armature and magnet to prevent any direct contact therebetween.

5. In a iluid fuel control device including a valve body having flow passage means therein and a valve member for control of fluid fuel through said passage, an operator comprising an armature and energizable magnet disposed within the flow passage means and connected to said valve member, biasing means cooperable with said armature and biasing said armature toward a retracted position, said magnet when energized being operable to move said armature to an attracted position, said biasing means and said armature preventing substantial contact References Cited in the iile of this patent UNITED STATES PATENTS 1,323,778 Lemp Dec. 2, 1919 2,267,411 McNairy Dec. 23, 1941 2,550,297 Ray Apr. 24, 1951 2,735,047 Garner Feb. 14, 1956 OTHER REFERENCES Germany, Ser. No. R10428, printed Jan. 19, 1956 (KL63c 5303).

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