Electromagnetically powered drive for a high speed counter
C United States Patent l 1 1 nu 3,879,601 Gamble Apr. 22, 1975 [5 ELECTROMAGNETICALLY POWERED 327x125 ill/I966 Gunst 215/9 c DRIVE FOR A HIGH SPEED COUNTER 3.340.520 9/!967 Candclise 335/226 X 334L694 9/l967 Hcimbcrger et al. 235/92 C [75] Inventor: John G. Gamble. Simsbury. Conn. [73] Assignee: Veeder Industries Inc.. Hartford. Prmmy Shaw Conn Assistant Eraminer-Joseph M. Thesz. Jr. Attorney, Agent. or Firm-Prutzman, Hayes. Kalb &amp; [22] F|ledz Jan. 29, I973 Chilton [2| I App]. No.: 327,7[6  
 [57] ABSTRACT [52] Cl 235/92 C: 235/92 R; 335/266 An electromagnetic operator comprises a plurality of [511 Int. Cl. G06m m0 idemica&#39; slenids &#34;wumed base and 581 Field of Search 235/92 c. 1 c. 91 M: having magneic which independem 335/266 each other. The solenoids attract a common armature and are connected in parallel electrical circuit rela- {561 References and tionship with the paralleled solenoids connected in se- UNITED STATES PATENTS ries with a single resistor to provide a faster acting armature with lower power consumption. 2.760.02fi iii/i956 Horlacher 335/226 X 123x359 3/1966 Eincm ct al 235/92 c 6 Claims 4 Drawing Figures PATENTEE APR 2 219. 5  
 FIG. 4  
 SHEET 2 0f 2 TIME l l l l l ELECTROMAGNETICALLY POWERED DRIVE FOR A HIGH SPEED COUNTER This invention relates to an electromagnetically powered drive and is especially concerned with such a drive for actuating a high speed counter such as disclosed in the US. Pat. No. 3,578,954 assigned to the assignee of the present invention.  
  A drive for a high speed electromagnetieally powered counter should provide for a rapid build-up of mechanical power when a pulser energizes the solenoid operator of the counter in response to a functioning of a pulser which is responsive to&#39;movements to be counted. This requires a high rate of flux generation in the solenoid to provide a rapid build-up of magnetic forces to attract the armature in accordance with Coulombs Law. However. the inductance of the electrical coil of the solenoid causes a counter EMF to be generated in the coil which, in accordance with Lenzs Law, is in a direction to oppose the applied voltage. Such counter EMF is proportional to the rate of change of flux in the solenoid which is greatest when the pulser first functions to energize the coil and delays the current buildup in the solenoid.  
  1n the past, electromagnetieally powered operators for high speed actuation have had an increased voltage applied across their windings to increase their speed of operation. However. this increased the counter EMF when the coil was first energized to decrease the rate of current build-up. Since, for a given solenoid, flux is proportional to current and the mechanical force attracting the armature is proportional to flux, such an increase in applied voltage was accompanied by an increase in the build-up of mechanical force but required a disproportionate increase in power to increase the speed of operation. in addition, this resulted in greater shock impact of the armature on the core of the solenoid of the operator which in turn caused armature bounce or rebound producing an instability of operation and increased wear and significantly decreased life. When used as a drive for a high speed counter, the instability sometimes caused false counts and erratic operation. This invention overcomes these problems by providing a stable, high speed electromagnetically powered drive suited for actuating a high performance high speed counter without an increase in power.  
  It is the primary object of this invention to provide an electromagnetically powered drive wherein the rate of build-up of mechanical forces attracting the armature is increased.  
  Another object of this invention is to provide an electromagnetically powered drive having a reduced time for substantially increasing the build-up of attracting force on the armature wihtout an increase in the voltage applied to the solenoid of the drive.  
  Still another object of this invention is to provide a high performance counter having a soft high speed electromagnetically powered drive.  
  A further object of this invention is to provide a soft stable high speed electromagnetically powered drive.  
  Other objects will be in part obvious and in part pointed out more in detail hereinafter.  
  A better understanding of the invention will be obtained from the following detailed description and the accompanying drawing of an illustrative application of the invention.  
 In the drawings,  
  FIG. 1 is a fragmentary side view of a high performance counter incorporating an exemplary electromagnetically powered drive of this invention;  
 FIG. 2 is a partial top view of the drive of FIG. 1;  
  FIG. 3 is a schematic electrical circuit suitable for the practice of the invention; and  
  FIG. 4 is a graph representative of the build-up of flux in an electromagnetic drive and a prior art drive.  
  As shown in the drawings. an electromagnetic drive 10 is provided with an L-shaped base 12 on which a solenoid 14 having a winding 15 and an iron core 16 is mounted. An armature 18 hinged to the base 12 at 20, is connected to a ratchet wheel 22 of a counter through a verge 24 and a pull rod 26 for advancing the count indicated by the counter in discrete steps indicative of the number of movements being counted. A pulscr, e.g., switch contacts 28, is provided for closing and opening the electrical circuit for energizing the solenoid winding 15 in response to the movements to be counted which cause the closure of the switch 28 by a switch actuator 30.  
  As best shown in FIG. 2 the electromagnetic drive 10 includes a second solenoid 14&#39; having a winding 15&#39; and an iron core 16 mounted on L-shaped base 12 to the side of the first solenoid 14. Preferably. in the prac&#39; tice of this invention, solenoids 14 and 14&#39; have the same number of turns, N, of the same wire size. and the iron cores l6 and 16&#39; have the same magnetic reluctance. The L-shaped base 12 together with the armature 18 and the cores 16, 16&#39; form two independent magnetic circuits for the two coils.  
  As shown in FIG. 3, the windings 15 and 15&#39; are also connected in parallel across the applied voltage and have a resistance R and an inductance L.  
  Schematically, a resistor 32 is shown as being connected in series with the paralleled windings 14 and 14.  
  When a voltage, V, is applied to a normal electromagnetic operator having a single solenoid such as solenoid 14, a current, I, flows through the winding 15, to cause the current through the winding to build-up to steady state conditions.  
  It is well known that the self-inductance. L. of a solenoid is stated by the equation:  
 where N is the number of turns of the winding, 1 is the current, and is the flux.  
  It is also well known that the time constant, T,., for a coil, that is the time required for the current to reach 63.2% of its steady state value after voltage, V, is applied, is given by the equation:  
 where L is the self-inductance of the coil and R is resistance. Substituting the value of L in equation (l) for L in equation 2, the resulting equation is obtained:  
 Iii.  
 Since 4) is proportional to l, equation 3 can be expressed as:  
 4 l T u:  
  Curve A of FIG. 4 illustrates the build-up of flux in a prior art electromagnetic operator having a single so lenoid with T indicating the time constant. T of the operator at a fixed circuit reluctance and connected across a given voltage, V.  
  In accordance with this invention, I have provided a plurality of solenoids which exert independent attraction or pull on the armature to provide an operator capable of reliable operation at increased speed or at the same speed with less wear requiring less power.  
  As disclosed above. the illustrated embodiment is provided with two solenoids 14, 14&#39;, which are connectcd in parallel with each other and in series with pulser 28 across a source of voltage, V. Solenoids l4, 14&#39; have magnetic circuits which are isolated from each other and have no magnetic coupling. As shown, a resistor 32 is connected in series with the paralleled solenoids 14, I4.  
  Since each of the solenoids l4, l4 attract the armature l8, their attracting force is added mechanically. and accordingly each needs to contribute only one-half the mechanical force required to power the armature. To achieve this, the steady state voltage applied across solenoid l4 and solenoid 14&#39; need be only one-half which it would be if only a single solenoid of identical electrical and magnetic properties were used. To reach this result, resistor 32 is sized to produce one-half the steady state voltage drop with voltage, V, applied to the same operator having a single identical solenoid 14. The steady state voltage drop across each of the solenoids l4, 14&#39; will also be one-half the voltage, V.  
  With such an arrangement as shown in FIG. 3, curve B of FIG. 4 represents the build-up offlux for attracting the armature by one of the solenoids l4, 14&#39;. It will be appreciated that. under the circumstances indicated, the current through each of the solenoids l4, 14 will be one-half the total current since these solenoids are electrically connected in parallel so that each carries only one-half the current which passes through resistor 32 which limits the steady state current to the same current level as in the representative prior art operator described above.  
  As shown, in FIG. 4, T indicates the time constant. T for a single one of the indentieal solenoids l4, l4, and graphically illustrates that its time constant is onehalf that of the prior art operator using an identical solenoid as represented by point T of curve A.  
 Since solenoid l4 and solenoid 14 are acting on the armature 18 simultaneously, their pull or attractive force on armature 18 is double that of either one alone. This is represented graphically by curve 28 which demonstrates that the time T required to develop a given flux level for attracting armature 18 is one-half as long for two solenoids 14, 14&#39; arranged in accordance with this invention as when an identical solenoid is used alone to power a prior art operator as described above.  
  Accordingly, for a given level of attractive force on the armature 18 the use of a pair of identical solenoids having independent magnetic circuits and connected electrically in parallel and in series with a resistor having a resistance value equal to that of one of the solenoids will produce a faster acting armature than a single identical solenoid acting alone.  
  it is further apparent that ifa plurality, P, of magnetically isolated solenoids are connected in parallel electrically to power a common armature, the force required of each solenoid will be l/P times that of one of the solenoids acting alone. This will result in a further reduced time constant for the operator which may be represented by a fraction in which the numerator is l and the denominator is the number, P, of solenoids powering the common armature.  
  As will be apparent to persons skilled in the art, various modifications, adaptations and variations of the foregoing specific disclosure can be made without departing from the teachings of the present invention.  
 I claim:  
  I. An electromagnetically powered drive comprising a source of pulses, a plurality of solenoids having magnetic circuits which are independent of each other and a common armature means attracted by said solenoids simultaneously, said solenoids being connected in series with said source of pulses and in parallel electrical circuit relationship with each other, and a resistor to decrease the time constant of the solenoids and limit the steady state current therethrough electrically connected in series with said paralleled solenoids.  
  2. The drive of claim 1 wherein the number of turns and the resistances of said solenoids are substantially equal.  
  3. The drive of claim 1 wherein the solenoids share a common base.  
  4. The drive of claim 3 wherein said common base for said solenoids forms independent magnetic flux path for each of said solenoids.  
  5. The device of claim 1 including a mechanical counter connected to said armature to be actuated thereby.  
  6. The device of claim 1 wherein the resistor is sized to produce a steady-state voltage drop equal to the voltage drop across the solenoids.