US1796193A - Thermostatic control mechanism - Google Patents

Description

March 10, 1931. EATON 1,796,193

THERMOSTATIC CONTROL MECHANISM Filed Nov. 26, 1924 IN VEN TOR. Harrison H. Edfon Patented Mar. 10, 1931 STATES PATENT OFFICE HARRISON H. EATON, OF TOLEDO, OHIO, ASSIGNOR TO THE ELECTRIC AUTO-LITE COMPANY, OF TOLEDO, OHIO, A

CORPORATION OF OHIO THERMOSTATIO CONTROL ME GHAINISM Application filed November 26, 1924.

This invention relates to improvements in regulating mechanism for dynamo-electric machines. More particularly, the invention relates to improved means for regulating the electrical output of a dynamo-electric ma chine in accordance with temperature conditions in the machine and in the surrounding atmosphere.

In the patent to Alvin E. Buchenberg, No. ,918, and in the co-pending application f Alvin E. Buchenberg, Serial No. 305,899, ii-ed June 21, 1919, there is described mechanism for controlling the regulation of a dynamo-electric machine in accordance with 11: outputand temperature conditions, dependent upon speed and load. In the disclosures above referred to, the general type of regulation employed is known as third brush regulation, consisting in a shunt wound machine, one terminai of the shunt field being connected to an auxiliary brush positioned interm diate the main load brushes, this securing a drooping characteristic to the machine voltage with increase of speed, due to internal clcctro-magnctic armature reactions with the R id ype of machine, the movement of th third brush from its normal position causes a variation in the voltage characteriszi tic, the movement in one direction, for er:-

a A e, dependent upon the direction of the windings ot the machine, causing a flatter curve than normal, and movement in the other dir ction causing a curve having higher ordi- 1 'nate than normal. In the disclosure of the patent and application above referred to, control of the third brush is obtained by thermostatic means opcrating to cause pivotal moven" nt of the third brush, such movement being in the proper direction to secure in summer time or in conditions of high load pronounced heating effects, a diminution of the machine current, and on the other hand, causing a movement of the third brush in cold weather or low load to increase the machine output. Certain deficiencies arise in mechanism in which the control of the third brush is brought about by a pivotal movement thereof, such, for instance, as that due to the shining of t ie point of brush contact on the Serial No. 752,340.

commutator, the brush having a new bearing area at each shifted point.

It is accordingly one of the important objects of the invention to provide means for shifting the third brush of a third brush regulated dyn amo-electric machine rectilinearly in counterdistinction to a pivotal movement. Another object is to provide improved and simplified mechanism controlled by a thermostatic device for shifting a brush of a dynamoelectric machine or similar machines or mechanism. It is an important object of the invention also to pr vide simple and effective means whereby the expansive action of a thermostatic device may be utilized to its maximum extent and efliciency. Further objects reside in the employment of a compact and inexpensive unit for shifting brush mechanism in accordance with temperature conditions which may be readily assembled and applied, and which is capable of eihcient operation under widely dii r'erent conditions of use.

Broadly stated, my invention consists in the utilization of a bodily movable support to which an electrical contacting device, such as a brush, is attached, and a temperature responsive element, such as a bi-metal thermostat operated to impart in accordance with temperature conditions, a movement to said moving support.

In order to set forth the invention so as to be clearly understood, I shall describe the same in connection with a specified embodiment thereof, which may be preferred, referring to the accompanying drawing, in which:

Figure 1 is a View of the inner side of the thermostatic device as positioned on the brush holder and with a brush in contact with the machine commutator;

Figure 2 is a view of the device looking toward its base as shown in Figure 1;

Figure 3 is a detail of the brush holder unit; and

Figure 4 is a wiring diagram of an electrical circuit in which the mechanism might be utilized.

Referring to the drawings, I have shown an end shell 10 of a dynamo-electric machine on the interior of which is secured a brush holder plate 11,

ure 1.

holder 11, adapted to have limited rotational movement by means of the pin 12, fixed to the end shell 10, and a cooperating slot 13, the pin and slot forming the holding means of the brush holder. Attached to the brush at a point adjacent where the third brush 14 is properly positioned, is an arcuate plate 15, any suitable means of attachment to the plate 15 being utilized as for example, bolts or rivets passing through the plate and the brush holder. flange 11.

Extending from the plate 15 are stud pins 16 and 17, these pins being positioned adjacent the base of the plate as shown in Fig- Pivotally mounted on the stud 17 is an L-shaped link or bell crank 19, one end of which extends to a point somewhat above the plate 11 at which point a stud 20 is secured, and the other branch of the link extending in a general direction parallel to the axis of the plate 11 and toward the end of said plate adjacent which point it terminates. 7

To the pin 16 is pivotally mounted a straight coupling link 21, one end being pivotally mounted on the stud 16, and the other end having pivotal engagement with a stud 22. The studs 16, 17, 20 and 22 all extend outwardly from the base plate 15 in the same direction and are adapted to receive and support a brush holding plate 23, this plate being pivotally mounted on the studs 20 and 22 and slidably mounted on the studs 16 and 17 through slots 25 and 26, cut in the plate 23 in a direction generally on the axis thereof.

The plate 23 is the brush holding support, the specific element of the support comprising a main pivot pin and a U-shaped sheet metal brush holding member 31 having parallel sides 32 and 33 adapted to receive the pivot pin 30 and a bridging portion 34 between the side plates 32 and 33 which is extended and bent angularly to form an engaging member 35 for the brush 14, the extreme end of the member 35 terminating in a reinforcing and contacting hook 36. A bolt 37 is shown for binding the brush 14 to the extension plate 35.

Means for normally maintaining the brush in close bearing upon the commutator 40 is shown, consisting in a coil spring 41, one free end of which engages a stud 42 projecting from the plate 23, and the other free end there of engaging the free side of the bridge 34 of the brush holder. As' the spring is under compression, it is evident that the brush 14 is forced closely into engagement with the commutator surface. 7 r

Note should be made of the lock washers 50, the same being U-shaped plates fitting into circumferential notches of the studs 20, 22, 30 and 42, these washers effectively preventing disengagement of the various cooperating parts of the mechanism.

It is evident that should pivotal move ment be imparted to the link 19, that the plate 23, by reason of its pivotal engagement with the stud 20, will be moved approximately linearly to an extent limited by the length of the slots 25 and 26. The exact direction of movement imparted to the plate 23 will, of course, vary with the mode of suspension of the plate 23 and the position of the supporting pins; and such movement may be given as to cause a smooth uniform pressure of the brush 14 on the commutator throughout its movable range.

Means for accomplishing the shifting of the brush holding plate 23 consists in a thermostatic element which may take the form of a bi-metal strip, one metal having a different rate of expansion per degree of temperature than the other, the plates being fastened to each other in such relationship that heating will tend to open out the normal U- shaped formation as shown in Figure 1, for example, and cooling will tend to contract the arms of the thermostat; but the alternate contracting and expansion of the thermostat, one arm of which is fixed in a pin 61 projecting from the base plate 15, and the other end of which is secured to the axially projecting arm of the link 19, causes pivotal movement of the link 19 about its pivoted stud pin 17, thus imparting to the plate 23 approximate rectilinear movement and thereby securing a variation in the relative position of the brush 14, effective to control the regulation of the dynamo-electric machine. Brass and steel are examples of metals usable in the thermo static device described.

In Figure 3 is shown means of insulating the pivoted pin 30 of the brush holder, this consisting in the use of insulating washers 7 0, 71 and 72, and a cylindrical insulator 73 about which the coil spring 41 is mounted. The field coil is connected to the brush through the screw 37.

Figure 4 shows an electrical system forautomobiles in which the thermostatic brush holding device may be utilized. The dynamo-electric machine 80 has main brushes 81 and 82 and a third brush 83 adapted to be moved on the commutator of the machine by the thermostatic device 84. The shunt field coil 85 is connected at one end to the thermostatic device and at its other end to the main brush 82. The dynamo-electric machine is connected to a battery 86 through a conven tional form of cutout 87 anda st rting motor 88 having a series coil 89 is also connected to the battery 86 through starting switch 90. An ignition system generally indicated at 91, is connected across the battery through an ignition switch 92.

The utilization of the invention in a starting, generating and ignition system such as is illustrated in Fig. 4 is particularly advantageous. Automotive vehicles employing such a system are subject to considerable variation in load and speed and are subject to use atall times of the year under conditions of considerable variance. In winter time, the electrical system of an automobile is subject to heavy load, the lights being on a greater portion of the time and the starting load being greater than normal, due to the stiffening of the lubricants and the consequent frictional resistance to the moving parts. Moreover, the engine fuel is not so readily ignited because of its lower ignition point. In the summer, on the contrary, conditions are somewhat reverse, the amount of night driving being considerably diminished with a lesser burning of the automobile la1nps,the frictional resistance of starting being less than in winter and the liquid fuel being more volatile. Consequently, the drain on the battery is less in summer than in winter and the thermostatic means employed becomes of real value in'controlling the regulation of the dynamo-electric machine output so that a greater output is obtained in winter in the range of speeds of the machine over that obtained in the summer throughout the same speed range.

The operation of the thermostatic device may now be readily understood. It may be assumed, for example, that the armature of the machine has a direction of rotation such as is shown by the arrow in Figure 1 in a clockwise direction. Should the temperature, effective to energize the thermostat 60 increase, the free arm thereof will expand as indicated in direction by the arrow, causing a pivotal movement of the L-shaped link 19, the free end of which moves in the direction of the arrow at the terminal of the link. This operation results in a movement of the brush 14: to the left in a direction opposite that of the rotation of the armature and thereby causing a diminution of the output of the generator. Subsequently, when the temperature affecting the thermostat arising from heat derived from the machine windings or from outside atmospheric temperatures or from both causes, decreases, the brush will be shifted to the right in the direction of the armature rotation and the output will automatically be increased for the same speed values. There is thus an automatic control of the third brush regulation dependent upon temperature conditions from any source affecting the thermostat.

Since the amount of charge that a storage battery in a system of the type described receives from a generator, is dependent upon the length and speed of run of the automobile where the driver of the automobile operates his car for a short interval only, the battery may receive insufficient charge. This may occur particularly in the winter, when the drain on the battery is at its maximum. It is desirable, therefore, that the charging rate be as high as possible to utilize to the utmost, the movement of the car on short runs. To fix the charging rate at its maximum value, however, would result in an over charge on long run and hence the necessity of some type of control arises. This control is amply provided for in the thermostatic device of the present invention which permits a setting of the electrical units for maximum generator output for short runs while on long runs when the heat of the generator coils become effective, cuts down the charging rate to safe values. In this way, maximum efliciency may be obtained from the dynamo-electric machine and the greatest effectiveness from the electric system, as a whole.

lVhile the description of the invention has been confined largely heretofore to the use in connection with an automo ve vehicle, it is, of course, obvious that the thermostatic unit may be readily applied to various other machines and mechanism in which it is desirable that a control or a movable part of the machine or mechanism be moved to alter the characteristics or condition of operation in a cordance with temperature conditions, the temperature being such as is derived from the machine itself or from various external fem both of these sources comnned.

[in important characteristic of the invention exists in the approximate linear movement of the movable regulatory brush instead of a pivotal movement as in other arrangements. The mechanism is such that the brush here referred to as the third brush is shifted bodily without appreciable rotation on its support axis, this insuring continuous and unmodified contact of the brush end with the commutator. In electrical machine operation, it is well known that as a carbon brush, for example, bears upon a rotating commutator, it smoothes out a contacting surface which gives a maximum conductivity between the brush and the commutator, insuring a minimum of sparking. To pivotally rotate the brush accordance with output or temperature conditions would cause a constant variation of the contact points of the brush and the commutator, thus diminishing the conductivity at this point and interfering in a measure with the electrical efficiency of a machine. By providing for a uniform unrotational movement of the brush, the bearing surface is maintained approximately constant, and electrical conductivity between the brush and commutator maintained generally at its maznmum value. Another i1nportant advantage of the invention arises from the link construction which permits compact assembly of the device as a whole. The holder unit may be secured to the ordinary brush holder of a generator without taking up any appreciable space.

The mechanism also readily permits the utilization of a spring for maintaining a constant uniform pressure of the brush upon the commutator. Note should be made further of the advantageous use of the thermostat which because of the U-shaped bend of the bi-metal parts of the same, permits a relatively large movement of the free end of the thermostat metal.

While I have described the embodiment of the invention which has certain advantages, it should be understood that various modifications of the same may be made, such changes, however, coming within the spirit of the invention and properly comprehended in the scope oi the claims hereto appended.

Having thus described my invention, What l claim as new is 1. in a commutator brush shifting device,

a support; a pair of levers pivoted to said support; a plate pivoted to levers, said levers having angular relationship with each other; temperature responsive means to move said plate; and a brush holder ri idly secured to said plate.

In a commutator brush shifting device, a support; a pair of levers pivoted to said support; a plate pivoted to said levers, said levers having angular relationship with each other. said plate having slots through which the pivots supporting said levers are adap ed to extend; temperature responsive means to move said plate; and a brush holder rigidly attached to said plate.

8. In a commutator brush shitting device, a support; an L-shaped lever pivoted to said support; a second lever pivoted to said support, and spaced from said first lever; a plate pivoted to said levers, with said levers in angular relationship with each other; a brush holder rigidly mounted upon said plate; and temperature responsive means to rotate said L-shaped lever about its pivot.

l. in a commutator brush shifting device, a support; an L-shaped lever pivoted to said support; a second lever pivoted to said support and'spaced from said first lever; a plate pivoted to said levers with said levers in angular relationship with each other; a pin attached to said plate; a brush holder insulatingly mounted upon said pin; and temperature responsive means to rotate said L-shaped lever on its pivot. V

In a commutator brush shitting device, a support; an L-shaped lever pivoted to said support; a second lever pivoted to said support and spaced from said first lever; a plate pivoted to said levers with said levers in angular relationship with each other; a brush holder rigidly secured to said plate; and a thermostat connected between said first lever and said support.

.6. Ina commutator brush shifting device, a support; an L-shaped lever pivoted to said support;a second lever pivoted to said support and spaced from said first lever; a plate pivoted to said levers with said levers in angular relationship with each other; a pin attached to said plate; a brush holder insulatingly mounted upon said pin; and a thermostat connected between said first lever and said support.

7. In a thermostatic device, the combination of a support, an L-shaped member pivotally mounted on said support, a plate pivotally connected to one arm of said member, a contact device secured to said plate, and a thermostatic'element secured to said support and the other arm of the L-shaped member whereby variation in temperature conditions adjacent the thermostatic element causes pivotal movement of the L-shaped member and consequent movement of said contact member.

8. in means for bodily shifting a brush on a commutator of a dynamo-electric machine, the combination of a brush holder, a lever pivotally mounted on said holder, a rigid member pivotally connected to said lever, a brush connected to said member and adapted to contact with said commutator, and means for imparting pivotal movement to said lever and consequent bodily movement to said brush.

9. In means for bodily shifting a brush on a commutator of a dynamo-electric machine, the combination ot a brush holder, a lever pivotally mounted on said holder, a rigid member pivotally connected to said lever, a brush connected to said member and adapted to contact with said commutator, and means for imparting pivotal movement to said lever and consequent approximate linear movement to said brush.

10. In means for bodily shifting a brush on a commutator of a dynamo-electric machine,the combination of a brush holder, a lever pivotally mounted on said holder, a rigid member pivotally connected to said lever, a brush connected to said member and adapted to contact with said commutator, and thermostatic means responsive to variations in temperature for imparting pivotal movement to said lever and consequent bodily movement to said brush.

In testimony whereof, I aflix my signature,

HARRISON H. EATON.

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