US2581280A - Electric regulator incorporating piled up carbon elements - Google Patents

Description

Jan. 1, 1952 M. Musso 2,581,280

ELECTRIC REGULATOR INCORPORATING PILED UP CARBON ELEMENTS Filed May 18, 1949 Inventor MARCEL MUSSO Agent Patented Jan. 1, 1952 UNITED STATES PATENT OFFICE ELECTRIC REGULATOR IN CORPORATING PILED UP CARBON ELEMENTS Marcel Musso, Paris, France Application May 18, 1949, Serial No. 93,982 In France May v2.1, 1948 Claims.

larly applicable to regulating systems including thin piled up discs made of carbon compounds whereby the variations in pressure exerted on said piled up discs are obtained through automatic devices acting under the control of any electrical quantity, suchas voltage, current, etc. Where in the following description the terms voltage and current are used, they are meant to refer to any electrical quantity to be regulated by, and influencing, the systems referred to.

The known regulating systems include means act directly or otherwise on the piled up discs through the armature of an electromagnet that is urged electromagnetically in a direction in opposition to a spring so that the resulting force exerted on the piled up discs is equal to the difierence between the action of the electromagnet and that of the spring.

The movement of the armature of the electromagnet may be a translational or rotational one; in either case, the attractive force of the electromagnet depends on the square of the induction force, on the cross-sectional area of the gap and also on the inverse value of the length of said gap. It will consequently vary with the relative position of the armature and will also depend on all the circumstances that may bring about an accidental change in the induction value, such as the temperature that makes the resistance vary in the wire forming the electromagnet coil.

Similarly, any change due to wear, temperature or other reasons may modify the distance between the armature and the piled up discs and consequently modify the action of the armature.

My invention has for its object a method according to which the displacements of the movable set do not cause a change in the force or the torque acting on said movable set through the electrical quantity that governs the operation of the arrangement.

My invention has also for its object an arrangement wherein the resultant of the forces applied to the piled up discs no longer depends on the initial position of the element compressing or releasing the pile.

According to a further the arrangement may be energized not only through direct current as in priorarrangements,

but also through one-phase or polyphase alternatingcurrent and even in certain cases by means of currents having difi'erent characteristics.

object of the invention,

According to a still further object of my invention, variationsin temperature have no efiect or practically no effect, due to the electromotive principle'used, on the force or torque which act on the movable set .through the electrical quantity governing said arrangement.

My invention is also characterized by the fact that the pressure is exerted on the piled up carbon discs through development of electrodynamic forces. According to a preferred embodi- .ment, the movable set is constituted by the rotor of an electric motor.

,I will now describe embodiments of my invention in greater detail, but many changes and modifications of the embodiments shown may 'be made without departing from the spirit of the invention.

The specification is accompanied by a drawing in which:

Fig. 1 is an axial diagrammatical cross section of a regulator according to my invention.

Fig.2 is an axial .cross section of a further embodiment of a regulator according to the inven-- tion.

Fig. 3 is a detail view of the embodiment of Fig. 2 illustrating the lever arm.

Fig. 4 is a detail of Fig. 2 illustrating the shape of the cam in plan view.

Fig. 5 is a diagram illustrating the operation of the spring on the bell crank.

As illustrated 'in Fig. l, a small asynchronous motor that may be three-phased for instance and of the squirrel cage type is fed by the voltage that is to be controlled automatically.

Its rotor Z is keyed to the shaft I and is given a resistance such that the maximum torque is developed at zero speed, said torque to correspond "to the required thrust. The motor will produce a torque that is, except for the ohmic drop in potential, a function of the square of the voltage fed "to the rotor.

To one end of the "rotor shaft is keyed the hub 5 to which is secured the end of a spirally avound torsion spring 6 the outer end of which is rigid with a frame 7 secured to the flange of the casing 8; the tensioning of the spring at the start is obtained through the rotation of said frame. The itorquedeveloped by said spring opposes the electrodynamic torque developed by :the rotor.

Obviously up to a certain value of the voltage feeding it, the rotor remains stationary and beyond said value the shaft I begins rotating in its bearings 9 and Ill and develops a torque equal to the difference "between its own torque and that of the counteracting spring.

The other end of the shaft is connected to a screw and nut 3, A or similar means, the screw 3 being pinned to the shaft while the nut d is adapted to slide in a bore of the hub H, but it cannot rotate by reason of the key I2 connected to the nut and sliding in the keyway E3 of the hub II.

The resultant of the electrodynamic torque of the rotor and of the torque of the counteracting spring causes a forward or rearward movement of the nut d the end of which forms a pusher member adapted to act on the piled up carbon discs.

Obviously the pressure exerted will depend solely on the difierence between the electrodynamic torque and the torque of the counteracting spring regardless of the position of the nut and consequently the angular position of the rotor has no influence on the actual value of said pressure.

In the embodiment illustrated in Figs. 2 to 5, the elements corresponding to those shown in Fig. 1 have been given the same reference numbers.

I is the shaft to which is keyed the rotor 2 of a small asynchronous motor the field windings of which have been shown diagrammatically.

ii designates the spirally wound torsional spring that opposes the electrodynamic torque developed by the rotor. The cam H1 is connected with the rotor 2 and has an inner shape (Fig. 4) that is advantageously a cardioid.

The cam i6 acts on a roller l urged against the cam by the spring iii. For this purpose, the spring 16 is pivotally secured at ii to the lever it while on the other hand the spring is anchored at a stationary point H). The spring may be suspended at said stationary point, for instance through the agency of knives or it may be pivotally secured to a spindle so as to be capable of assuming an angular direction depending on the resultant stress exerted on it.

The lever i8 is formed by a bell crank carrying at one end the roller l5 and being pivotally secured at 20 (Fig. 5), for instance, by means of knives resting on suitable plates. The short arm 2| of the bell crank 18 carries a stud 22 by means of which pressure is exerted on the piled up elements 23.

The operation of said arrangement is as follows: under the action of the spring it, when contracted, the stud 22 presses normally on the elements heaped up at 23. The electrodynamic torque produced by the rotor under the action of the current passing through the windings of the stator causes the cam i l to rotate and the roller 15 to move so as to vary the pressure exerted on the heaped up elements at 23.

It will be easily understood that according to the direction of the forces exerted, the heaped up elements are subjected to compression or release. If said heaped up elements are inserted for instance in the field circuit of a generator, the voltage of which feeds the small asynchronous motor, an automatic regulating action in the direction required for correcting any variation in the voltage will be provided.

It is obvious that in an arrangement of this type, the torque depends chiefly on the voltage feeding the motor so that resistance Variations due for instance to variations in temperature constitute a disturbing factor of secondary importance only.

If in the arrangement disclosed a polyphase induction motor is used and connected to the poly- 4 phase A. C. system, the voltages of the polyphase system, even if the phase voltages are unequal for which the term "unbalanced is com" monly used, will be kept at an average value.

Consequently, if the generator is called upon to feed an unbalanced load while the regulator depends on the resultant of the fields produced by the 3 or N phases, the regulation will be executed with respect to the average value of the voltages of the different phases. This shows the advantage of my improved regulator over known regulators allowing action only on a single phase which could lead to the necessity of inserting a regulator in each phase.

Where it is desired to control a single phase system, the same arrangements are applicable whereby a single phase induction motor is used as a regulator, an auxiliary phase being provided in said motor fed with current that is phase shifted through an induction coil or a capacitor.

It is also possible to provide in the stator of the asynchronous motor not only one but two or more windings that may be fed with voltages or currents having the same frequency but not necessarily the same phase. The torque on the rotor shaft of the motor will be the resultant of the different superimposed torques. Such an arrangement is applicable for instance to the parallel operation of several generators.

In case of direct current, the control device may include a rotor with a constant gap having a series or shunt field according to the characteristic desired for the variations of the driving torque with reference to the electric quantity governing the D. C. feed.

With a view to avoiding the need of a commutator, of brushes and associated parts, the armature winding may be tapped at two points or even consist of cross coils, with the feed provided through flexible leads or through the springs balancing the torque.

Under such conditions, for a predetermined feed voltage, the electrodynamic torque varies obviously as a function of the sine between the rotor winding and the inducing field; however, it is certain that for a substantial angular shifting of the rotor Winding to either side of its position of maximum torque, the sine of the angle varies but little and consequently the thrusts necessary for the action on the piled up discs may be practically constant over a wide range regardless of the angular position of the rotor.

The counteracting spring may be a, coiled or a torsion spring of any suitable shape or it may be associated with a further spring acting through compression or contraction and inserted between the pusher member and the piled up discs. The transformation of the angular shifting of the rotor into a linear movement to act on the piled up discs may be achieved, for instance, by means of a connecting rod and crank pin arrangement, the axis of the piled up discs being positioned if required in a plane that is not parallel to the axis of the motor, it is also possible to use a system including a cam and cam followers moved by the motor shaft and acting on the piled up discs through a lever or similar transmission means.

What I claim is:

1. A method for applying a variable pressure on a stack of carbon elements forming a resistor influencing an electrical current to be regulated, comprising causing said current to develop electrodynamically, in combination with a magnetic circuit, the reluctance of which is constant, a

static deflecting torque depending solely on characteristics of said current, and causing said torque to produce on the resistance a pressure the value of which depends solely on the turning movement of said torque.

2. System for applying a variable pressure in an electric regulator on a stack of carbon elements forming a resistor influencing an electrical current to be regulated, comprising in combination with said resistance, an electric motor in cluding a stator, a, rotor and a rotor shaft, said motor establishing an inductive field having a constant reluctance, means for feeding said motor with the current to be regulated, resilient means arranged to act on the rotor shaft in opposite direction to deflecting torque produced in the motor, means for transforming the deflecting movement of the rotor into a translational movement, and means to transform the translational movement into pressure against the resistance elements, the value of the pressure depending solely on the value of the characteristics of the current developing the rotor torque.

3. System for applying a variable pressure in an electric regulator on a stack of carbon elements forming a resistor influencing an electrical current to be regulated, comprising in combination with said resistance, an electric motor including a stator, a rotor and a rotar shaft, means for feeding said motor with the current to be regulated, resilient means acting on the rotor shaft in opposite direction to the electrodynamic torque produced in the motor, a threaded member coaxial with and rigidly secured to the motor shaft, a nut engaging said threaded member, means for preventing said nut from rotating, and means to transform the longitudinal movement of the nut into pressure on the resistance elements, the value f the pressure depending solely on the value of characteristics of the current developing the rotor torque.

4. System for applying a, variable pressure in an electric regulator on a stack of carbon elements forming a resistor influencing an electrical current to be regulated, comprising in combination with said resistance, an electric motor including a stator, a rotor and a rotor shaft, means for feeding said motor with the current to be regulated, resilient means acting on the rotor shaft in opposite direction to the electrodynamic torque produced in the motor, a cam rigidly carried by the rotor shaft, a bell crank, a stationary pivot for the apex thereof, a roller carried by one end of the bell crank and engaging the cam. a spring supported at one end and pivotally secured at its other end to the bell crank for urging said roller against the cam, and means at the other end of the bell crank to exert pressure on the resistance elements.

5. A method for applying a Variable pressure on a stack of carbon elements forming a. resistor influencing an electrical current, comprising causing said current to develop by electromotive principles a static deflecting torque depending solely on characteristics of said current, mechanically setting a force in opposition to said torque according to the desired value to be regulated, and producing a variable pressure on the resistor, the pressure changes being solely depending on the deflecting torque.

MARCEL MUSSO.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,503,085 Blake July 29, 1924 1,892,054 I-Iinchman Dec. 2'7, 1932 1,955,111 Buckler Apr. 17, 1934 2,015,468 Brown et al Sept. 24, 1935

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