US2396596A - Regulating mechanism - Google Patents

Description

March 12, 1946. T. w. MOORE REGULATI NG MECHANISM Filed Feb. 12, 1944 Z2 if e 9 y J 9 Patented Mar. 12, 1946 REGULATING MECHANISM Thomas W. Moore, Dayton, Ohio, assignor to The Leland Electric Company, Dayton, Ohio, a corporation of Ohio Application February 12, 1944, Serial No. 522,119

9 Claims.

This invention relates to regulators and more particularly to regulators of the carbon pile type.

It is the principal object of the invention to provide a carbon pile regulator in which the characteristic of the sprin means and that of the opposing solenoid are made to vary in corresponding relation, leaving a resultant of the proper amount for effecting compression of the pile, and in which the spring is so arranged that its internal stress condition makes it adaptable for operation with accuracy and reliability over different pressure and displacement ranges by suitable adjustment of the pile.

It is a further object to provide a spring means for a carbon pile regulator in which the spring force is made to accurately correspond with the non-linear force characteristic of the solenoid with the spring being shaped of varying cross section such as to develop a substantially uniform internal stress characteristic throughout, making it possible for the regulator to be operated over different ranges of adjustment.

Other objects and advantages will be apparent from the following description, the accompanying drawing, and the appended claims.

In the drawing:

Fig. 1 is a view partially in side elevation and partially in vertical section of a regulator constructed in accordance with the present invention, on a scale somewhat larger than full size;

Fig. 2 is a plan view of the contact assembly showing the spring arms mounted thereon with the armature disc being removed;

Figs. 3 and 4 are views in plan and side elevation respectively of one of the spring elements utilized in the present invention; and

Fig. 5 is a plan view of a modified form of spring element.

Referring to the drawing which discloses a preferred embodiment of the invention, the carbon pile itself is shown at H), comprising a number 01' small discs of carbon which are stacked inside tube II of ceramic or other electrical insulating material capable of carrying away the heat developed in the pile. The tub I I is received within a metal shell l2 which is provided with a number of deep radiating fins l3 in order to facilitate the dissipation of the heat generated in the pile.

The shell I2 is formed with an end flange l5, and means are mounted on this end flange for adjusting the pressure applied to the end of the pile, and hence the range of adjustment over which the pile operates. This means comprises a disc-shaped member l6 having a centrally located flange H the inner portion of which is threaded as shown at I8 to receive an adjusting screw or ferrule l9. The inner end 29 of ferrule l9 bears against the pile so that upon changing the setting thereof the position of this end of the pile may be varied, and hence the range of adjustment thereof predetermined, suitable means being provided for retaining the ferrul in any adjusted position. The disc i6 is mounted between insulating washers 22 and 23 and is fastened to the end flange [5 by means of a series of screws 24 around which is an insulating sleeve 25 so that it is electrically out of contact with the frame l5, but physically supported thereon. An electrical connection 21 is made to the disc l6 which thus connects with the one end of the pile.

The solenoid is shown at 39, which is received within a magnet case 3! having outwardly projecting flanges 32 and 33 thereon, being also formed integrally with an inwardly projecting flange 34. The magnet case is of suitable magnetic material, and is detachably secured to the frame member l2 by means of through bolts 3.5 which extend through the respectiv flanges I5 and 33, the bolt being shouldered as shown in order to provide for the proper spacing of the respective parts from each other.

An end disc 31 is secured in place by means of screws 38 extending into end flange 32, the end cap 31 being centrally apertured and threaded as shown at 40 to adjustably receive the core 4| therein. Washers 42 held in place on the end cap 31 by means of bolts 43 bear against the end of the core and provide for securely fastening the same in any adjusted position.

The armature 45 is mounted in position immediately adjacent and overlapping both the inner end of flange 34 and core 4|. The armature is carried by spring contact assembly which supports a carbon button 47, such button comprising the contact for the opposite end of the pile l0, and also providing for applying the variable pressure to the pile. The carbon button 41 is received within a socket formed by member 48, which is held on metal disc 49 by screws 58 which extend into and secure th armature disc thereto. The screws have insulating washers 5! under their heads and are further insulated by washer 52. The electrical connection is made to the socket 453 by connection 54, this electrical contact thus being completely insulated from the armature and other parts of the magnet case, and providing for connection only to the carbon button 41 and the carbon pile.

The spring means is also carried by the assembly, being secured to the metal disc 49 by a series of screws BI and is in the form of a series of spring members or leaves 62 having the individual form shown in Figs. 3 and 4. The base 83 of each spring member is received between the plates 49 and 52, notches 64 being provided to permit the passage of screws iii for retaining the assembly. The outer portion of the spring is given a small inclination toward its abutment which as shown in Fig. 4, may be of the order of 7. This bend occurs along the line 65, which in the assembled form is located immediately adjacent the periphcry of the discs 49', 52, and hence approximately at the beginning of the unsupported and flexible portion of the spring. The spring assembly is enclosed within a casing or shell 67 which is received over screws 35 and which seats against the outer periphery of flange 53, thus preventing access of dust and foreign matter into the spring assembly.

The spring abutment is provided by means of an annular disc 59 which is seated against the outer face of flange 2-6 of the magnet case, and annularly outwardly of the armature Against this disc 69 there is positioned the actual abutment member 68 which is in the form of a ring of bimetal which has the frusto-conical shape shown in Fig. 1. It is against the exposed face of this abutment that the outer ends of the spring arms 62 bear, each of the elements thus being inclined toward the other, and the several spring arms engaging the abutment at spaced points around the periphery thereof.

It will be clear that the abutment thus serves as a pressure surface against which the springs may work, and the surface of which is conically shaped so that in response to application of increasing pull by the solenoid, the armature moves toward the abutment and the spring arms wrap the surface of the abutment, thereby shortening the efiective length of the spring and increasing the resultant force of resistance of the spring in a non-linear manner, substantially corresponding with the characteristic of the solenoid itself. In response to temperature changes, the abutment will move relatively to the spring and thus provide for increasing or decreasing the air gap, with a corresponding change in the current flow through the solenoid at which equilibrium is reached. This change in current results in a voltr age change which compensates for the change in resistance brought about by temperature fluctuations.

As shown in Fig. 3, the spring arm is not of uniform cross-section, but that portion of it which is subject to stress, that is, the portion outwardly of the contact assembly, is made of variable cross-sectional area, tapering and progressively decreasing outwardly from the spring assembly to the outer end thereof. The spring in engaging the abutment acts essentially as a beam, the effective length of the beam changing in accordance with the length of the spring which has wrapped the abutment. For any given loading the bending moments progressively increase from the point of application of the force inwardly to the point of support of the spring, and with the construction as herein shown and described, the section of the spring which is required to transmit this force progressively increases in a corresponding manner. As a result, there is developed a substantially uniform internal stress per unit area throughout the length of the spring subject to stress, and thus the entire working or stressed section of the spring is made to work at a substantially uniform unit stress, this being true regardless of the extent of the outer end portion of the spring which has wrapped the abutment.

This provides a highly important result in relation to the operation of the regulator, particularly with respect to the adjustment screw I9 which may be varied to change the position of the pile over a substantial range, and throughout which range the pile will continue to respond to the operation of the solenoid in the same corresponding relation, substantially balancing the characteristic thereof over such complete range. Where a spring arm of uniform section is used, it is found that the adjustment of the pile is rather difilcult and quite critical, and that the operation of the regulator is suitable at most for only a very limited range of adjustments, limiting the conditions under which the pile can be used. Thus with a spring arm of uniform section the spring does not uniformly wrap the abutment but the outer end portion of such a spring is relatively stiff and unyielding. The bending all tends to occur at the Zone of maximum bending moment, viz, where the spring emerges from the armature assembly. This causes the armature to be excessively stiff in the positions where the air gap is large, and thus limits the range of accurate and reliable operation to a small part of the range of displacement making it necessary to adjust the regulator for operation over only that relatively small part of the range where the air gap is small.

In the present invention, by reason of the tapering cross-section of the spring arms, the outer portions of the arms are not stiff but are capable of yieldi-..g, so that the bending is actually distributed over the substantially entire working or stressed portion of the spring and further, the outer ends of the arms are permitted to flex into flat contact with the abutment and the proper and accurate wrapping action of the abutment thus secured. With this construction the range of displacements over which the regulator can satisfactorily operate is not limited to only a small part of the range, but proper operation is obtained over the entire range from large to small air gaps. Thus the pile can be adjusted by means of screw 19 to operate in any selected portion of that range, with good regulation being secured throughout, and with much greater stability than is obtainable with the ordinary spring, the regulator showing practically no tendency to hunt or flutter throughout such range.

This greater flexibility of adjustment is particularly desirable where the regulator is to be subjected to wide vairations in atmospheric conditions, primarily, temperature and humidity. In the ease of unusually low temperatures for example, a temperature compensated regulator having spring arms of uniform section loses accuracy and requires readjustment. Unless reset it is then unsuitable for operation at normal temperatures because of instability. The elfect of humidity is to cause a shortening elongation of the carbon pile itself, again necessitating readjustment as the moisture content of the pile changes, which it tends to do in operation as its temperature rises under load. With the construction of the present invention the pile retains its accuracy of adjustment over a full range of displacements so that even wide change of tem 9.. ture and moisture content do not objectionably affect its operation, and it remains both stable and accurate. For example, with springs of uniform section an accuracy of :3% was obtainable over a range of displacements of the end of ferrule 59 of about .005 inch; with the present construction, the same accuracy, viz., 153%, is obtained over a range of displacements of approximately .020 inch, with the regulator retaining its essential stability over an even greater range, thus being much less subject to destructive oscillations.

Fig. 5 shows a modified plan view of a spring arm, in which the arm likewise tapers and is of reduced cross-section outwardly from its point of support, the side surfaces however being defined by two curved lines rather than by straight lines. The important characteristics is the reduction in the cross-section at such a rate as to establish the proper internal force conditions throughout the range of operation of the pile and to properly balance the magnetic characteristics of the regulator, the actual section of the arm being selected as desired for developing this condition.

While the forms of apparatus herein described constitute a preferred embodiment of the invention, it is to be understood that the invention is not limited to these precise forms 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. A carbon pile regulator comprising an electromagnet having an essentially non-linear characteristic, a carbon pile, an abutment, a spring for opposing the force of said electromagnet, said spring being arranged to wrap said abutment to change the effective length thereof and to develop an. increasing spring force opposing and substantially balancing the pull of said electromagnet.

said spring having a variable width decreasing toward the outer end thereof providing for developing a substantially uniform internal stress characteristic throughout the portion thereof subject to stress.

2. A carbon pile regulator comprising an electromagnet having an essentially non-linear characteristic, a carbon pile, an abutment, a spring adapted to engage said abutment for opposing the force of said electromagnet, said spring having a tapering width outwardl from its point of support providing for the distributed flexing and bending of the stressed portion thereof.

3. A carbon pile regulator of the character described which comprises an electromagnet, a carbon pile, an abutment, spring means of substantially uniform thickness adapted to engage said abutment to oppose the force of said electromagnet, said spring means having an outwardly tapering cross-section providing for distributed bending throughout the stressed portion thereof.

4. A carbon pile regulator of the character described which comprises an electromagnet, a carbon pile, an abutment having an inclined working face, spring means having outwardly extending arms of substantially uniform thickness inclined toward and adapted to engage said working face for opposing the force of said electromagnet, said spring means having an outwardly tapering cross-section providing a yieldable outer end portion for flatly engaging said abutment and accurately wrapping the same.

5. A carbon pile regulator of the character described which comprises an electromagnet having a core, an armature separated from said core by an air gap, a carbon pile, an abutment, spring means adapted to engage said abutment for opposing the force of said electromagnet, said spring means having an outwardly tapering width providing for distributed bending throughout the stressed portion thereof, and means for changing the displacement of said pile while retaining the accuracy and stability of said regulator over substantially the entire range from large to small air gaps.

6. A carbon pile regulator comprising a solenoid having an armature and adapted to develop an essentially non-linear characteristic, spring means carried by said armature, a fixed abutment in position to engage said spring means and adapted to be wrapped by said spring means with a resultant shortening of the effective length thereof, the width of said spring means decreasing outwardly from said armature toward the outer end thereof providing for the bending of the portion thereof which wraps said abutment.

7. A carbon pile regulator comprising a solenoid adapted to develop an essentially non-linear characteristic, a carbon pile, an armature assembly, spring means for applying pressure to said carbon pile in opposition to the pull of said solenoid on said armature, an abutment located radially outwardly of said armature and adapted to engage said spring means and to be wrapped thereby as said armature moves inwardly toward said solenoid, the width of said spring means progressively decreasing oi-utwardly thereof to provide for distributing the bending throughout the entire working length of said spring means.

8. A carbon pile regulator comprising a solenoid adapted to develop an essentially non-linear characteristic, a carbon pile, an armature assembly, spring means for applying pressure to said carbon pile in opposition to the pull of said solenoid on said armature, an abutment located radially outwardly of said armature and adapted to engage saidspring means and to be wrapped thereby as said armature moves inwardly toward said solenoid, the width of said spring means progressively decreasing outwardly thereof to provide a yieldable outer portion capable of progressively bending in wrapping contact with said abutment, and means for shifting the position of said pile relative to said abutment to change the range of adjustment of said regulator.

9. A carbon pile regulator comprising a solenoid adapted to develop a substantially nonlinear force characteristic, a magnet case for receiving said solenoid, an adjustable core within said solenoid, an armature in magnetic relation with said magnet case and said core and subject to the force of attraction of said solenoid, a carbon pile, a contact assembly for applying pressure to said carbon pile, said contact assembly including means for receiving and supporting said armature thereon, said abutment having a generally conically shaped surface, spring means carried by said contact assembly and normally projecting in deflected relation in opposing contact with said conically shaped surface and adapted to wrap said surface in response to movements of said armature to change the effective length of said spring, the portion of said spring which is subjected to working stress having a width of substantially uniformly tapering dimensions outwardly of said assembly providing for distributing the bending over the stressed portion thereof, and means for changing the range of displacements of the carbon pile.

THOMAS W. MOORE.

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