US2256225A - Electroresponsive device - Google Patents

Description

Sept. 16, 1941. L. w. THOMPSON ELECTRORESPONSIVE DEVICE Filed Nov. 29, 1940 Inventor:

n m r O O h flt Q W 5 i H 9% 9 b Patented Sept. 16, 1941 ELECTRORESPONSIVE DEVICE Louis W. Thompson, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application November 29, 1940, Serial No. 367,865

2 Claims.

This invention relates to electroresponsive devices and more particularly to improvements in primary electroresponsive controllers for automatic regulators.

In conventional devices of this type the element which responds to the regulated quantity or condition also provides the power for selectively closing one or the other of two sets of contacts. These contacts are in circuits which control the direction of operation of a regulator.

In accordance with this invention I provide a novel and simple controller in which the burden or load on the element which responds to the regulated quantity is reduced to a minimum. This is done by practically eliminating all friction tending to retard motion of the element and by obtaining the power for positively operating the contacts from a secondary element. Another feature of the invention is that whenever a regulating change is required the contacts are periodically closed instead of being continuously closed, thereby producing an intermittent operation of the regulating means. This tends to prevent hunting or overshooting of the regulator. In addition, my device also provides for varying the ratio of time closed to time open of the periodically closed contacts in such a manner that this ratio increases in proportion to the degree of departure of the regulated condition from a normal value, that is to say, in proportion to the need for regulation.

An object of the invention is to provide an improved electroresponsive device.

Another object of the invention is to provide a unitary primary electroresponsive controller for automatic regulators which is highly sensitive in operation and which inherently tends to prevent hunting of the controlled regulator while at the same time correlating the degree of regulation produced with the degree of regulation required.

The invention will be better understood from the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

In the drawing Fig. 1 is a detailed perspective view of an embodiment of the invention and Fig. 2 is a circuit diagram showing how my invention may be used in an automatic rheostatic generator voltage regulator system.

Referring now to the drawing and more particularly to Fig. l, the operating element comprises an electromagnet having a winding l for responding to the value of any suitable electrical function of a non-electrical quantity and having a movable armature assembly consisting of a. solenoid core 2 and mechanical linkages 3, 4 and 5. This assembly is mounted from a fixed 'support 6 by means of four crossed leai springs 1. Two of these springs are shown as horizontal and two are vertical. They provide a pivotless and frictionless mounting which confines the motion of the armature assembly to rotation about a substantially fixed axis coinciding with the intersection of the planes of the leaf springs. Thepull of the magnet is balanced by a weight 8 which is adjustably positioned on a rod 9 by means of a set screw ill. The rod 9 extends outwardly from a member H which is rigidly fastened to the arm 5. The position of the weight 8 is so adjusted that the armature assembly will be balanced when the value of the regulated condition to which the operating magnet responds is at a given or predetermined normal value.

In order to insure that the armature assembly will have a predetermined normal position corresponding to the normal value of the regulated condition the rod 9 is also provided with a U- or horseshoe-shaped armature or keeper I2 for cooperation with a permanent magnet I3. The magnetic force exerted by the magnet i3 on the armature i2 tends to bias the armature assembly toward a normal or neutral position. The strength of this biasing force is adjustable by means of a slotted block of metal M in which is mounted an eccentric l5 which is rotatable by means of a knurled adjusting knob l6. Rotation of this knob will move the magnet i3 toward or away from the armature l2 thereby strengthening or weakening the centering force.

The lower end of the arm 5 is bent at right angles to form a stop for a leaf spring H which is quantity to be regulated or any suitable electrical fastened at its inner end to the arm 5 by means of a screw i8 and which is fastened at its outer end to an H-shaped piece of any suitable material 19 by means of another screw 20. Above the member i9 and on opposite sides thereof are contact operating members 2| and 22 for operating respectively separate sets of contacts 23 and 24. These sets of contacts are normally open and each set has a movable contact carried by an individual leaf spring 25 mounted on suitable supports 26 (only one of which is shown). In order to give rigidity to the mounting of the movable contacts and to confine their motion to rotation about particular axes separate blocks 21 of any suitable material, such as hard rubber or steel, are fastened to the springs at an intermediate point thereon by means of screws 28. These blocks in turn are fastened to fixed supports 29 by means of pairs of leaf springs 30 at right angles to the springs 25, thus producing the same kind of crossed spring mounting as is provided for the armature assembly.

By means of this construction an upward force applied to the contact operating members 2 or 2i will rotate the blocks it about axes which co-= incide with the line of intersection of the planes of the crossed springs 25 and 36 thereby closing the respective sets of contacts.

Below the piece is is a roughly U-shaped member 3i attached to a suitable support 32 by means of a fiat leaf spring 33 so that the piece 38 is limited to motion in a vertical direction as viewed in the drawing. This member is reciprocated continuously in a vertical direction by means of a cam 34! driven by any suitable means such as an electric motor 35. The cam engages a roller 38 attached to the member 3i so as to reduce friction and Wear.

The upper ends of the arms of the U-shaped member 3| are beveled so as to vary the ratio of the time open to the time closed of the contacts as will be described hereafter.

The operation of Fig. l is as follows: The parts are shown in the positions they assume when the device responds to the normal value of the regulated condition. These positions are such that the member I9 is in registration with the opening or slot in the U-shaped member 3% so that the arms thereof pass freely on both sides of the member l9 as the member 3! is reciprocated. If now the regulated condition departs from normal, balance between the pull of the magnet and the pull of the weight 8 will be disturbed and the armature will rotate in one direction or the other thereby moving the member 59 to the right or the left as the case may be. This will position the member i9 over one of the arms of the U-shaped member 3! so that it will be periodically pushed in an upward direction whereby it will engage either the contact operating; member 2| or the contact operating member 22 thereby causing periodic closing of the corresponding set of contacts in the manner previously described. By reason of the beveled shape of the ends of the arms of the U-shaped member 3| the member I9 will be pushed further and further upward for every upward movement of the member 3i, or in other words it will start to rise sooner and will return to its original position later, as the member l9 moves further to the right or left away from its normal position. Consequently, as this degree of right and left motion is proportional to the deviation of the regulated condition from normal it follows that the ratio of time closed to time open of the contacts will increase as the departure of the regulated condition from normal increases.

In Fig. 2 the operating winding I is connected across a generator 31 through a conventional rheostat 38 for limiting its current and adjusting the setting of the device. The contacts 23 and 24 control respectively the energization of a series pilot motor 39 through respective field windings 40 and 4| for causing the motor to operate in opposite directions. The motor is connected to drive a rheostat 42 connected in series with a field winding 43 for the generator. The system is so adjusted that when the generator voltage is normal the contacts 23 and 24 remain open. If now the voltage departs from normal in either direction the contacts 23 and 24 close in the manner described above thereby periodically energizing the motor which thereby steps the rheostat 52 along in the proper direction to raise or lower the current in the field winding at so as to restore the generator voltage to normal. The step by step action of the motor prevents over travel of the rheostat or hunting of the system and the variation in the ratio of time open to time closed of the contacts insures that the motor will operate faster as the degree of departure of the voltage from normal increases and will operate slower as the voltage returns to normal. The invention is obviously not limited to generator voltage regulators and its application to other voltage regulators,'such as feeder voltage regulators, will occur to those skilled in the art.

It will be noted that in my device the operating element is required to do no more than move a light-weight balanced armature assembly about a substantially frictionless pivot. As a result the device is very sensitive in operation. Fur thermore, it will be observed that the force which closes the contacts is obtained from a secondary source of power, namely the motor 35, which is continuously operating and which may readily provide ample power for causing firm, positive engagement of the contacts thereby minimizing arcing and burning away of the contacts.

While there have been shown and described particular embodiments of this invention, it will be obvious to those skilled in the art that various changes and modifications can be made therein without departing from the invention and, therefore, it is aimed in the appended claims to cover all such changes and modifications as fallwithin the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. A primary electroresponsive controller for an automatic regulator comprising, in combination, an electromagnet having a winding which is energized in accordance with the value of a condition to be regulated and having a movable armature assembly, a set of crossed leaf springs for providing a frictionless pivotless mounting for said armature assembly, means attached. to said armature assembly for balancing the pull of said winding thereon when said winding is energized in accordance with the normal value of said condition, two sets or normally open contacts, one contact of each set being crossed leaf spring mounted, a continuously reciprocating member for engaging a part of said armature assembly whenever said assembly departs from its normal position so as to impart a reciprocating motion to said part, means responsive to said reciprocating motion of said part for periodically closing one or the other of said sets of contacts depending upon the direction of the departure of said ar mature assembly from said normal position, and

. means for increasing the ratio of the time closed to the time open of said sets of contacts in proportion to the magnitude of the departure of said armature assembly from said normal position.

2. A primary electroresponsive controller for an automatic regulator comprising, in combination, an electromagnet having a winding which is energized in accordance with the value of a condition to be regulated and having a movable armature assembly, a set of crossed leaf springs for providing a frictionless pivotless mounting for said armature assembly, means attached to said armature assembly for balancing the pull of said winding thereon when said winding is en;- ergized in accordance with the normal value of said condition, means including an adjust-ably positioned permanent magnet for biasing said armature assembly toward a predetermined normal position, two sets of normally open contacts, one contact of each set being crossed leaf spring mounted, a continuously reciprocating member for engaging a part of said armature assembly whenever said assembly departs from its normal position so as to impart a reciprocating motion 10 sition.

LOUIS W. THOMPSON.

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