US2287880A - Apparatus for operating vibratory motors - Google Patents

Description

June 30, 1942.

H. H. HITTSON APPARATUS FOR OPERATING VIBRATORY MOTORS Filed Jan. 10, 1941 41070? GENE/FAME M0703 GEM/[19703 lbs 151:9?

/NVEN7'OR HARKER H. HITTSON, BY 44 724M,

Ari-9.

Patented June 30, 1942 2,287,880 APIAARATUS FOR. OPERATING VIBRATORY MOTO Harker H. Hittson, Columbus, Ohio, assignor to The Jeffrey Manufacturing Company, a corporation of Ohio Application January 10, 1941, Serial No. 373,985

Claims.

This invention relates to. a method of and apparatus for operating and controlling vibratory motors, and more specifically vibratory motor conveyors, so as to maintain the amplitude of vibration of the vibratory motor or conveyor deck substantially constant at a pre-selected value which may be varied over a wide range.

An object of the invention is to provide a new and improved method and apparatus of the above mentioned type in which the amplitude control is automatic and continuous and is effected by adjusting the frequency of the current delivered to a vibratory electro-magnetic motor toward or from its natural period of vibration so that said amplitude of vibration is maintained substantially constant within a narrow range at a preselected value which may be varied under the control of the operator.

Another object of the invention is to provide apparatus of the above mentioned type in which the control circuit is simplified from previously known control circuits and in which the frequency of the current delivered to the vibratory motor is controlled independently of the natural period of vibration of the vibratory motor, but which bears a variable relation to said natural period of vibration to effect the desired amplitude control.

Other objects of the invention will appear hereinafter, the novel features and combinations being' set forth in the appended claims.

In the accompanying drawing:

Fig.1 shows a preferred embodiment of the system of my invention;

Fig. 2 shows a modification of a portion of the system of Fig. 1; and

Fig. 3 shows another modification of a portion of the system of Fig. 1.

It may be pointed out that many of the details of the control system herein disclosed are identical with the system illustrated particularly in Fig. 4 of the application of Clyde W. Baird, Serial No. 371,314 for a Vibration control apparatus, filed December 23, 1940, but certain fundamental differences have been made in the system of said Baird application which make for an entirely different overall mode of operation.

Referring particularly to Fig. 1 of the drawing, the system of my invention includes a pair of power mains I and In! which are fed from any desired source of alternating current and provided with a magnetic switch 2 having a start push button 3 which is normally open, and a stop push button 4 which is normally closed.

When the switch 2 is closed, as hereinafter described, after a predetermined time interval following the energization of a circuit for heating the filaments of the gaseous discharge tubes, in response to the operation of push button 3, a transformer 1 is energized, the secondaryterminals of which areconnected to the plates of gas-filled electronic discharge tubes 8 and 9 which act as a full-wave rectifier to rectify the alternating current delivered thereto, which rectified current is delivered over conductors I0 and H to a vibratory motor I2 preferably forming a vibratory conveyor such as disclosed in the patent to James A. Flint, No. 2,094,787, dated October 5, 1937, there being an ammeter provided in conductor to as illustrated at I3.

To start the operation of the system a switch I4 is closed which energizes a transformer I5 which has three secondary windings, the righthand one of which energizes the filaments and cathodes of the electronic discharge tubes 8 and 9, .the left-hand one of which energizes the filaments of electronic discharge tubes 49 and 50 and also supplies the voltage for a full-wave rectifier bridge 8| which provides a direct current negative bias on the grids of the tubes 49 and 50, all over obvious circuits. The more complete circuits for the tubes 49 and 50 and the bridge 8| are described hereinafter. The third of said secondary windings of transformer l5 energizes the heater filaments of electronic tubes'3l and 83 in series, thus insuring that either both or neither of said tubes will be energized at the same time.

The closing of the switch [4 starts into operation a filament heating time delay circuit I! which is similar to that described in complete detail in the above-identified application of Clyde W. Baird, which is operative so that after a predetermined time interval its relay I8 is energized and in addition to closing a holding circuit on itself, connects conductors l9 and 20 by way of normally open contacts 2| which makes voltage available for the magnetic switch 2 since conductor I9 is connected to main I through switch [4, and conductor Ml extends to said switch 2. A signal lamp 22 connected through a resistor to conductor I9! and also connected to conductor 20, is energized upon the closing of contacts 2|,

thus signaling the operator that he may close the contacts of switch 2 by pushing the button 3. This time delay relay I1 is provided to insure adequate heating of the cathodes of gaseous discharge tubes 9 and 9 before voltage is applied to the anode or plate circuits thereof to prevent damage to said tubes. When relay 2 is closed, power is supplied to tubes 9 and 9 and this closed conditionis indicated by signal lamp I6 being energized through the third set of terminals of said switch and through contacts 2I.

The method oi? automatically controlling the amplitude of vibration of the vibratory motor I2 to maintain it substantially constant within a Dre-selected but adjustable range, as determined by the operator, is fundamentally different from the method disclosed in the above identified application of Clyde W. Baird and from other known prior devices. The frequency of the impulses or undulations of the current which flows to the motor I2 is not necessarily or even probably the same as the natural period of vibration of said motor I2, but the natural period of v1- bration of the motor I2 is an important factor and the frequency of the current delivered to said motor I2 is regulated automatically so as to move toward or from said natural period of vibration in response to amplitude variations from a pre-selected value. In this connection it is a known characteristic of a vibratory electromagnetic motor that if the current delivered to it is substantially constant, its amplitude may be adjusted by adjusting the frequency of the current toward and from said natural period of vibration either above it or below it. The maximum amplitude will be realized when the delivered frequency coincides with .the natural period of vibration and if the delivered frequency moves either above or below the natural period, the amplitude of vibration will progressively decrease with the departure therefrom.

I make use of this phenomena by delivered current to said motor I2 at a frequency which is to be controlled and varied automatically in response to amplitude variations from a preselected value so as to bring the delivered frequency closer to the natural period of vibration. of the motor I2 in case the correction requires an increase in the amplitude of vibration,and-

conversely if an opposite correctionis required.

There is another important distinction 'betweenmy system. and that of the Baird application above mentioned, in that there is no difllculty from thejsource 4II-so that there is no current flow in "resistors 48and '44, but durirmunstable conditions=-or when the-amplitude of vibration or alternating current because an alternating;

current generator of one kind or another is provided and this insures alternating or undulating current of-approximately the requiredstartin frequency, and control is effected by adjusting this frequency whenever necessary.

. 'It is evident that the current which flows through the tubes 8 and 8 would be direct ourrent in the absence of some modifying means,

and this modifying means which is eilective to convert it into impulses or undulating current at a controllable frequency, includes the grids of said tubes 8 and 8 which are connected together .8 connected thereto.

and to a conductor 25, said grids having a filter A I shall now describe the pickup and automatic v control circuit which, as above stated, follows in many details the disclosure of the application;

' of Clyde W. Baird, above identified, and particularly thesystem shown in Fig. 4 of .the drawing mum amplitude control resistor 32, and amplitude control resistor 34 having a variable tap 35. The operator by adjusting tap 35 variably preselects the operating amplitude of vibration within the limits provided by the maximum, the

minimum of which may be controlled by resistor 38 and its variable tap. The adjustable voltage as determined by the position of the variable tap 35 is transferred to transformer 38 having in its output circuit a full wave rectifier vacuum tube 31 which rectifies the current, delivered thereto which flows through balancing bridge resistor 38 provided with a lay-pass filter condenser 39. Resistor 38 is'one' branch of a bridge, the other branch of which includes a source of constant direct current voltage indicated generally by the reference character 48. Said source of constant direct current voltage is provided by a transformer 82 which derives power from the mains I and IM over an obvious circuit when switch I4 is closed. Connected to the secondary of the transformer 82 is a full wave rectifier including, a vacuum tube 83, the output circuit of which extends from the cathode to the center tap of the secondary of the transformer 82 and includes a bridge or network 84 comprising a condensor 85 having a resistor 88 connected across the terminals thereof and across which terminals there is connected a neon tube 81 and a resistor 88, that is, neon tube 81 and resistor 88 are effectively connected in series and together are in parallel withresistor 88 and condensor 85.

In such a network the voltage drop across the terminals of the neon tube 81 will be substantially. constant regardless of any variations in line voltage, and thisconstant voltage'dropis connected in the bridgework including resistors 38 and-tworesistors 43 and which are connected acrossconductors 4I and 42.fi In other words, a bridgework is formed byresistors 38, 43 and 44- and the constant direct current. voltage source 48, and during stable conditions the voltage drop across resistor 38 will match the constant voltage of the motor. I2 increases or decreases rfrom its preselected'--value; there will be 'a current: flow throughres'istors 43 and44 in opposite directions where 'opposite conditions prevail, to effect automatic. control as hereinafter described.

The-center tap of the two resistors 43 and 44 is -connected-to the negative terminal of the full wave'rectifier 8| which provides a normal negative bias on the two gaseous discharge tubes 48 and 58 as hereinafter described. Filtering condensors 41 and 48 are connected across resistors 43 and 44, respectively, through the full wave rectifier 8|.

The control grids of the gaseous tubes 48 and 5 are connected through. protecting resistors to conductors 42 and M, respectively, and the input circuits to said tubes are connected to the cathodes thereof from the center tap of the condensors 41 and 48 through a network formed by ccndensor 55 and adjustable resistor 58 to provide an anti-hunting circuit for the motor 24 hereinafter described more completely.

Tubes 49 and 58 have stabilizing or. protecting grids which are connected in parallel with the cathodes. The negative bias provided by the full wave rectifier bridge BI is sufllcient to bias the tubes 48 and 58 normally to cut off, and these tubes will only fire in response to an unbalanced condition. For example, if the amplitude of vibration of the motor I2 exceeds a preselected value, the voltage drop across resistor 30 will exceed the fixed voltage derived from source 40,

and current will flow through resistors 43 and 44 in that sequence. The voltage drop across resister 43 will oppose the negative bias on bridge so that the grid of tube 49 becomes less negative and this tube will fire. The voltage drop across resistor 44 will simultaneously increase the negative grid bias on tube 50 which is without consequence. Conversely, if the amplitude of vibration of the motor I2 falls below the preselected value, the voltage drop across resistor 30 will fall below the voltage of the constant source 40, and current will flow through resistors 43 and 44 in that sequence, in which case the voltage drop across resistor 44 will reduce the negative bias on the grid of tube 50, causing it to fire, while the voltage drop across resistor 43 increases the negative bias on the grid of tube 49, which is without consequence.

The above-described anti-hunting network was described as in the input circuits of tubes 49 and 50, but it is also in the output circuits thereof since it leads to the cathodes of said tubes, and said output circuits extend from said cathodes through said anti-hunting circuit by way of common conductor 54 to a common terminal of a pair of primary windings of separate transformers 52 and 53, the other terminals of which are connected to the anodesor plates 49 and 50, respectively.

The secondaries of transformers 52 and 53 are connected across a pair of shading coils 51 and 58, respectively, of the motor 24, which motor 24 adjusts the variable tap I 02 of a motor driven rheostat I03, as hereinafter described more comconductors 59, 60 and GI. .The motor 24 is of well known construction and when shading coil 51 is short-circuited it will rotate in one direction, and when shading coil 58 is short-circuited it will rotate in the opposite direction, and when neither is short-circuited, it will not move. These coils 'I,an d 58 are normally energized because the miotor 24 has a field coil 62 which is constantly I energized whenever switch 2 is closed since it is connected directlyacross conductors I and IOI.

I By virtue of the magnetic coupling between the coil 52 and the shading coils 51 and 59, voltage is normally induced in each of said shading coils I and this voltage is delivered to the secondary windingsof the transformers 52 and 53 by way of conductors 59, 60 and GI, this voltage being the r' vplatevoltage for the two tubes 49 and 50 after it is stepped up by transformers 52 and 53. As a result-whenever tube 49 becomes conducting as above described, it effectively short-circuits transformer 52 which effectively short-circuits shading coil 58 thereby causing a corrective adjustment of the variable tap I02. Similarly, when tube 50 becomes conducting transformer 53 is effectively short-circuited and shading coil 51 is short-circuited causing a reverse corrective operation of tions. The frequency of the current delivered to said motor I2 is determined by a small motor 1 generator set A which is preferably a direct current motor driving an alternating current gen- I This motor generator set A is very small control the grids of the tubes 0 and 9, the output pletely, the connection between said transformer .secondaries and shading coils being by way of 1 thereof extending to said grids by way of conductors 25 and I04, conductor I04 leading to the cathodes of said tubes 8 and 9 through a protective resistor, and conductor 25 leading to .the grids through the filter 26 as above mentioned.

It is of course evident that the frequency of the current on the conductors 25 and I04 will control the frequency of the current delivered to the motor I2 over conductors l0 and II. Also the frequency of the generator of the motor generator set A or in other words the frequency on the conductors 25 and I04, may be adjusted by adjusting the speed of the driving motor of said motor generator set and this is adjusted automatically by adjusting the variable tap I02.

In addition to the rheostat I03 I preferably also provide a rheostat I05 which is manually adjustable and which is preferably so adjusted that in case the frequency variations are below the natural period of vibration of the motor I2, it would be impossible even though all of rheostat I03 is cut out, to generate a frequency by motor generatorset A, which is in excess of the natural period of vibration of the motor I2.

From the above description it is obvious that in the operation of this system the adjustable contact 35 may be moved to any desired position by the operator to give a preselected normal amplitude of vibration of the motor I2. This is preferably effective with the pointer I02 substantially midway of its two extreme positions on the rheostat I03. Under these conditions the frequency of the motor generator set A is such that if it is increased the amplitude of vibration of the motor I2 will increase, and if it is decreased said amplitude of vibration will decrease. This assumes that the operation of the motor I2 is at a frequency below the natural period of vibration, but of course the control may be operated always above the natural period of vibration by obvious adjustments. If the amplitude of vibration thereafter increases, the pointer I02 will be automatically adjusted to decrease the frequency of the motor generator set and thus automatically decrease the amplitude of vibration until it returns to its preselected value. A reverse condit-ion will produce a reverse result and thus the amplitude of vibration will always be maintained constant.

The apparatus above described from the pick up device 2! through the motor 24 constitutes means for constantly and automatically measuring the amplitude of vibration of the motor I2 by comparing it with a preselecteddesired value.

If pointer I02 is stationary said motor amplitude coincides with said preselected value. If it moves to the left or the right the amplitude is too low or too high, as the case may be.

In Fig. 2 I have shown a modfication of the preferred embodiment of my invention in which the motor generator set A is made of much greater capacity than that previously described so that its output is fed directly to the motor I2 by way of -conductors I0 and II. In other words, this eliminates the tubes 9 and 9 and their various controls as well as the transformers I. This will also involve certain obvious changes in the connections to the switch 2.

In Fig. 3 of the drawing I have illustrated another modification of the preferred system of Fig. 1, in which a non-rotary type of generator is substituted for the .rotarygenerator A,'said non-rotary generator being illustrated at B. This generator B may be of any well known design such as low frequency electronic tube oscillater or a relaxation oscillator of known design.

The frequency variations in this system are obtained by adjusting the value of some impedance, such as an adjustable condenser, reactor or resistor, this adjustment ofcourse being effected automatically by the motor 24.

Obviously those skilled in the art may make various changes in the details and arrangement of parts without departing from the spirit and scope of the invention as defined by the claims hereto appended, and I therefore wish not to be restricted tothe precise construction herein disclosed.

Having thus described and shown an embodiment of my invention, what I desire to secure by Letters Patent of'the United States is:

1. In combination, a vibratory electro-magnetic' motor which has a natural period of vibration, means for delivering current impulses of variable frequency to said motor including electronic valve means, means for constantly and automatically measuring the amplitude of vibration of said motor, means controlling said valve means including a variable frequency source to determine the frequency of the current impulses delivered to said motor, said measuring means being connected to vary the frequency of said variable frequency source in response to measured changes injthe amplitude of vibration of said motor, all whereby said amplitude of vibration of said motor is maintained substantially constant.

2. Vibration control apparatus comprising the combination with a vibratory electro-magnetic motor having a natural period of vibration, of m ms for supplying variable frequency current to said vibratory motor including electronic tube means capable of producing direct current and having control grid means, a motor generator set having a variable speed motor and connected to control said grid means thereby to control the frequency of the current delivered by said electronic tube means to said motor, means constructed and arranged to respond differently to reverse variations inthe amplitude of vibration of said vibratory motor from a preselected motor of said motor generator set upwardly or downwardly selectively, thereby to adjust the frequency of the current delivered to said vibratory motor toward or from its naturalv period I vibration and thereby to maintain the amplitude motor having a natural period of vibration, of

means for supplying variable frequency current to said vibratory motor including electronic tube means having control grid means and a variable frequency generator connected to said grid means to control the frequency of the current delivered to said motor, means constructed and arranged to respond differently to reverse variations in the amplitude of vibration of said vibratory motor from a preselected value, and means operable by different responses of said response means to adjust the frequency of the variable frequency generator selectively upwardly or downwardly thereby to adjust the frequency of the current delivered to said vibratory motor toward or from its natural period of vibration and thereby. to maintain the amplitude of vibration ofsaid vibratory motor substantially constant.

4. Vibration control apparatus comprising the combination with a vibratory electro-magnetic motor having a natural period of vibration, of means for supplying variable frequency current to said vibratory motor including electronic tube means having control grid means and a variable frequency electron discharge generator, means connecting said generator to said control grid means, means constructed and arranged to respond. differently to reverse variations in the amplitude of vibration of said vibratory motor from a preselected value, and means operable by difierent responses of said response means to adjust the frequency of the variable frequency generator selectively upwardly or downwardly thereby to adjust the frequency of the current delivered to said vibratory motor toward or from its natural period of vibration and thereby to maintain the amplitude of vibration of said vibratory motor substantially constant.

5. Vibration control apparatus comprising the combination with a vibratory electro-magnetic motor having a natural period of vibration, or means for supplying variable frequency current to said vibratory motor including an oscillating generator, and means constructed and arranged to respond to variations in the amplitude of vibration of said vibratory motor from a preselected value, and means controlled by said last named means to adjust the frequency of the current delivered to said vibratory motortoward or from its natural period of vibration thereby to maintain the amplitude of vibration of said vibratory motor substantially constant.

HA-RKER H. HITISON.

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