US2091681A - Drive suitable for remote control - Google Patents

Description

E. B. HANSELL Aug. 31, 1937.

DRIVE SUITABLE FOR REMOTE CONTROL Filed Oct. 25, 1934 ATTORNEY Patented Aug. 31, 1937 UNITED STATES PATENT OFFICE DRIVE SUITABLE FOR REMOTE CONTROL Erik B. Hansell, New York, N. Y.

Application October 25, 1934, Serial No. 749,963

4 Claims.

This invention relates to drives suitable for remote control, and is herein illustrated as embodied in a radio receiving device.

It is often desirable to move to variable amount a control or other device at a distance and many mechanisms have been designed to that end, but it has been found diflicult to devise mechanism which can be easily attached to a standard article, like a radio set, and be entrusted to unskilled hands for installing it. If a control for a radio set, for example, is to be installed on one floor of a house for controlling the tuning of the set on another floor, the connections must be electrical to avoid the otherwise inevitable lost motion, and the length of the electrical connections introduces a complexity by reason of the electrical resistance which varies with their length.

If relays are introduced into the set, the complexities are added to, and parts are introduced which are likely to be damaged by rough handling in shipping. Moreover relays usually involve contacts which may become dusty and thereby of uncertain electrical efliciency. Moreover; the use of relays usually involves either timed mechanical drives or separate electric conductors for each portion of the tuned device.

Similar difllculties arise in other kinds of devices in which it is desired to drive some distant device, or part, to an accurately controlled variable extent.

According to the present invention these and other difficulties and disadvantages are overcome, and an electrical device is provided which requires a very small current, is capable of being carried on inconspicuous wires, and yet which easily and almost positively controls a device using almost any amount of power, at least any power capable of being furnished by a power electronic vacuum tube.

In the form of the device disclosed herein in some detail one side of a Wheatstone bridge contains a settable variable resistor and the other side contains a second variable resistor, which, in reality, serves as an indicator for the controlled device, herein shown as the radio tuning condenser.

These resistors are shown as balanced around the grid of an electronic vacuum tube, so that the tube may, through its plate control the grid of a second or power tube forming part of a circuit adapted to drive the armature of a motor in one direction.

The plate of the second tube is shown in turn as connected to the grid of a third tube, likewise a. power tube, forming part of a circuit adapted to drive the motor armature in the opposite direction.

These connections are shown as such that the armature is turned by the current from one tube only part of a turn under the torque of the current driving it and then is arrested by the current from the other power tube. In the structure shown, this result is attained by directly coupling the motor shaft both to the shaft of second resistor and to the shaft of the variable tuning condenser.

In the structure shown, it has been found possible to obtain satisfactory tuning by a tuning dial at a resistor connected to the radio set by upwards of fifty feet of No. 38 cotton covered copper wire, and to use a rotary motor armature specially wound with No. 44 enameled copper 'wire, with the result that a current of a few milliamperes operated the shaft of the tuning condenser.

The device is shown as adapted to use alternating current, but with some modification, mainly simplification, it may be adapted to use direct current.

The device is shown as forming part of a radio receiving set, and, to make it almost fool-proof for radio users, is shown with a push button starting device which, for some uses will prove unnecessary. Moreover the tuning knob and the resistor it controls are primarily adapted for radio use, while for other uses the resistor may take other forms, such, for example as a lightsensitive electron tube which, of course, requires no knob.

Even in radio sets a single tuning handle will often be all that is desired, and, as will appear, certain parts will then be unnecessary.

It will be noted that one variable arm of the Wheatstone bridge starts the motor and, in effect, the other variable arm stops it. It will be noted that the device requires no making and breaking of heavy currents through relays, thus making the device fool-proof in the sense that an ordinary radio set is fool proof.

Other features and advantages will hereinafter 45 appear.

The accompanying electrical diagram shows one form of the invention.

In the accompanying diagram showing the in vention as embodied in a familiar type of radio receiving set, the radio set may be tuned from any position of the parts by first pressing a push button, diagrammatically shown at I 0, so as to warm up two power electron vacuum tubes l l and I2, and incidentally vwarming other tubes described below. v

The current for warming the tubes comes from a power source shown as two leads 8 and 9 carrying a house alternating current. When the button I is pressed it closes a circuit through a conductor I5 connected to the tuning lead wire l6 connected to an arm |1 fastened to a motor armature shaft l9 butelectrically insulated from it. The arm l1 when dead lies against an arm l8 and closes a circuit from the priming transformer through wires 2| and 22. At the same time another arm 23, likewise fast on the shaft I9, but insulated from it, and lying on the spring drawn swinging arm 24 completes the circuit through a wire 25 connected to a solenoid 26 forming part of a relay 21. The circuit is thus closed through the other wire 28 of the tuning lead.

The circuit closed by the relay 21 is taken from the power source wires 6 and 9 being shown as two leads 29 and 30 put into the circuit between the lead 8 and its transformer winding 3|.

As soon as the circuit is closed, tube I2 is warmed by the current excited in conductors l3 and I4 excited by the transformer 3| and the tube causes a current to flow through the armature 32 on the shaft l9 and turn it to lift the arms l1 and 23 from their terminals l8 and 24.

This current starts because the warm cathode I 33 of the tube l2, heated by usual heater filament 34, sends electrons to the usual plate 35, closing the circuit from the lead 36, connected to one brush 31 of the armature 32. The other side of the circuit, connected to the plate 35, consists of a lead 38 coming from the secondary winding 39 of the transformer 3|. An intermediate point of the secondary 39 is connected to the other brush 40 of the armature 32 by conductor 4|.

The turning of the armature 32 permanently closes the circuit through the leads 29 and 36 by allowing the spring 42 to draw the arm 24 against the end 43 of the lead 29.

To tune the radio set there is shown a usual type of variable capacity 44 fast to an extension of the shaft I9 of the armature. To turn this capacity 44 to vary it there are shown tuning knobs 45 and 46. To effect tuning the operator presses the knob 45 against the tension of a spring 46 so as to carry the end of a stub shaft 41 against a terminal 48 of the conductor l5 which, it will be remembered, is connected to the tuning lead wire l6.

If the knob45 is then turned it carries a wiper arm 49 across a resistance 50 to vary the resistance. A carbon resistance of half a million ohms has been found satisfactory. The wiper arm 49 moving on the resistance therefore varies the amount of current which flows through it by way of conductor |5 from the tuning conductor l6 to the tuning conductor 28, the conductors l6 i the two variable resistances 56 and 53 to maintain the same voltage on the grid 5|.

If the current through the variable resistance 50 tends to set up a higher voltage on the grid 5| than the voltage set up by the variable resistance 53, the hot cathode 55 of the tube 52 sends more of its electrons to the plate 56, increasing the current going through the plate 56 and through a conductor 51 connected to the grid 58 of the power tube H. The current is able to go through the plate 56 because the conductor 51 is connected by a high resistance 59 to the plus side 60 of a continuous current source shown as a rectifier 6| taking current off the transformer 3|. Four million ohms has been found satisfactory for the resistance 59.

The current through the conductor 51 lowers the voltage in the grid 58 compared to the cathode 62 of the tube l, making it more negative in amount suificient to stop the flow of electrons from the cathode to the plate 63, and making the power tube inert compared to the power tube l2.

The connections are such that, at this time, the plate 63 through a conductor 64 changes the voltage on the grid 65 of the tube |2 so as to facilitate flow of electrons from the cathode 33' to the plate 35. This flow constitutes a current through the tube l2 and, consequently, through the conductor 36 and through the armature 32 on the shaft l9. The shaft turns.

If the knob 45 had been turned the opposite direction, the charge on the grid 58 would have been lowered or-made more to the positive, the potential would have risen on the plate 63, raising the potential on the grid 65 to stop the current from the plate 35. At the same time the increased potential on the plate 63 would cause a current to flow through conductor 64, resistance 11, conductor 36, armature of the motor 32, and back through conductor 4|, etc. to cathode 62, driving the motor in the reverse direction.

But in other words, when current from preceding tube 52 is of such magnitude that the potential across grid resistor 59 of tube raises the grid 58 (negatively with respect to cathode 62) beyond out ofi bias no current flows in tube II. By the same analysis, since tube H is now the preceding tube to 2 and it has no current flow, there will be no drop across grid resistor 11 and consequently grid 65 of tube 2 is at same potential level as its cathode, and therefore normal plate current flows in this tube. The reverse action takes place when there is no current from the preceding tube 52.

The turning of the shaft l9 turns the variable capacity 44 and with it the wiper arm 53a, changing the resistance 53 until it tends to produce the same change in voltage at the grid 5| as the variable resistance 56 changed the voltage.

The two variable resistances 56 and 53 are balanced around the grid 5| like two arms of a Wheatstone bridge. The other two arms of the bridge are shown as two, usually, fixed resistances 66 and 61 connected on opposite sides of the cathode 55 by a conductor 68. These have been found satisfactory when approximately about 5000 ohms apiece, but if it is found advantageous to use difi'erent types of resistances for variable resistances 50 and 53, the resistances 66 and 61 must be appropriately chosen. The variable resistance 53 is shown as connected by a conductor 69 through a protective resistance 16, advantageously 10,000 ohms, to the flxed resistance 61 to complete its arm of the bridge.

The variable resistance 50 is shown as connected by a conductor 1|, through the conductor 28 and a resistance 12, usually like *the resistance 19, to the fixed resistance 66, to complete the other arm of the bridge. The resistances 66 and 61 are connected across the output of the rectifier 6i through the conductor 68 and the resistances l5 and 16.

The tube 52 is shown as having an additional suppressor grid I3 connected to the cathode 55, and with a space charge or screen grid 14 connected to its appropriate voltage about 100 volts higher than the cathode, taken between resistance I5 and 16 to the conductor 68. These two grids increase the sensitivity of the tube 52.

To obtain the needed drop between the cathode 33 of tube I2 and grid 65a high resistance ll is shown between the conductor 64 and the conductor 36. It has been found possible to use 1500 ohms for this resistance and this is shown as balanced by 1500 ohms resistance at 18 in the 20 conductor 38.

To enable several turning knobs 45 and 46 to be used independently it is needful to add a stopping electron vacuum tube 19 shown as connected across the limiting resistance .16, through which flows a current depending on the setting of the variable resistors 50 and 53, thus putting cathode 80-of that tube I9, connected near the variable resistance 53', at one voltage and the grid 8| of the tube at another and lower voltage, be-

cause the grid is connected to the transformer side of the resistance 18. This difference, in

effect, makes the tube 19 dead as long as that current is passing through the resistance 18.

When the knob 45, or any other tuning knob,

is lifted to break the current through its variable resistance such as 58, the current ceases through the resistance 10, and, as a result, the tube 19 is no longer dead because electrons flow from the cathode 89 to the plate 82, causing a current through a conductor 83 which includes a resistance 84 (found satisfactory if approximately the same as resistance 59). The resistance 84 is connected to a wiper arm of a variable resistance 85 which is in series with the resistance 59. The

resistance 85 has been found satisfactory if three million ohms.

These connections cause a suitable current to be maintained in the tubes H and I2, even though no current passes through the variable resistors 59 and 53 for the following reasons:

When tubes II and i2 are normally operated by tube 52, there is always either no current 01'' maximum current flow in the respective tubes as the case may be, since the grids have either no 55 bias or bias be ond cut-off, which means motor will run in either one or'the other direction depending upon which of the two tubes has the normal current fiow. But when tube 19 controls II and I2 through resistances 84 and 85, a state 0 in between cut-ofi bias and no bias is obtained wherein current will flow in tube H but not to the extent of completely stopping fiow in tube l2 by a high negative bias. In short, a state is reached whereby an equal current flows in each tube and thus buck one another in the armature with the result that the latter stands still. The fine adjustment required is obtained by virtue of the fact that resistor is a fractional part of the total state resistor 84 and thus has but a 7 correspondingly small portion of the total plate and 85. This means that after adjustment of resistance 85 has been made, the same small potential bias is always impresed on grid of l I thus rendering this always at the half operation point. The tube 19, therefore, makes it possible to provide any number of tuning knobs 45 and 46 each having a normally idle variable resistor 50 and wiper arm 49.

It is possible to utilize the remote tuning lead conductor 28 for remote volume control. To effect this a. conductor 86 leads from the conductor 28 to a remote tuning handle shown as a wiper arm 81 running over a high resistance 88 forming a continuation of the conductor 86. To change the volume of sound the wiper arm 81 is shifted on the resistance '88 so as to alter the voltage on a screen grid 89 forming part of a radio frequency amplification tube 90 in the radio set, thus altering volume of sound.

It is possible to attach a loud speaker on to the remote tuning lead conductors 28 and i6, provided these are of sufficient gage to carry the necessary current. The loud speakers terminals 9i and 92 are shown as connected through condensers 93 and 94. To block high voltage alternating currents a choke coil 95 may be needed. The choke coil is shown in the conductor I6, between the loud speaker terminals and the grid 5i. The loud speaker unit shown at 96 connects through condensers 97, and 98 to the leads l6 and 28.

What was said above about driving the motor in one direction applies to driving it in the opposite direction with altered voltages on the grids .58 and 65, and this is true whether the polarity of the armature or of the fields is what is altered. When the variable resistance 50 re- -mains unaltered, the grids 58 and 65 balance opposing tendencies to drive the armature. In the form shown the motor is supposed to have fields of constant polarity. They may even be permanent magnets.

The armature in the device shown was wound with 44 gage enamelled copped wire to about 1500 ohms. The rotary armature used was a lap wound with back pitch of 5 and a front pitch of 3, having seven poles or armature winding elements. The motor was about the size used in toy electric trains.

Instead of the priming device described above, a switch 99 in the main 29 or 39 may be used.

It will be found useful to provide shields for at least some of the tubes of a common type.

Having thus described certain embodiments of the invention, what is claimed is."

1. A driving device including a motor having a field and an armature, a pair of electron vacuum tubes with grids and having plates providing currents adapted to move the armature relatively to the field in opposite directions, a connection to the grid of one tube from the plate of the other tube to control the current therein, a control device, and a connection from the grid of the other tube to the control device.

2. A driving device including a motor having a field and an armature rotatable relatively to the field, a pair of electron vacuum tubes with grids and having plates providing currents adapted to rotate the armature in opposite directions, a connection to the grid of one tube from the plate of the other tube to control the current therein, a voltage control device, and a connection from the grid of the other tube to the control device.

3. A power device having a motor including coils with a resistance of hundreds of ohms, a

pair of electron tubes adapted to drive the motor in either direction through the coils, one of said tubes controlling the second, a variable resistance settable to control the first tube, and another electron tube adapte'd to cause the pair of tubes to hold the motor idle when the circuit is broken at the variable resistance.

4. In a control device a rotatable motor armature, a pair of leads to carry current to the armature, an electron tube having a plate connected to supply current to one lead, a grid for the tube, control means for its grid, a second electron tube having a cathode to supply current to the same lead, a grid in the second tube directly coupled to the plate of the first tube, a bias resistor forming the connection between the coupling and the lead, and a connection between the cathode of the first tube and the plate of the second tube, means for maintaining a drop of potential along the connection, and a conductor from vthe second lead to an intermediate point of said connection.

ERIK B. HANSELL.

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