US2412366A - Pressure fluid follow-up motor - Google Patents

Description

Dec. 10, 1946.' A, SPENCER ET AL 2,412,366

' PRESSURE FLUID FoLLow-UP MOTQRv Filed March 19. 1942 2 Sheets-Sheej'. 1

ai l

. Dec. l0, 1946. A. SPENCER ET AL- 2,412,366

PRESSURE FLUID vFOLLOW-UP MOTOR Filed March 19. 1942 2 sheets-sheet 2 Patented Dec. 10, 1946 UNITED SATES PRESSURE FLUID FOLLOW-1UP MTR land, a British company Application March 19, 1942, Serial No. 435,349 In Great Britain March 19, 1940 5 Claims. 1

This invention relates to power transmissie systems, of the repeater type, particularly applicable to the fire control of guns, of the kind wherein movement of the gun or other object to be moved is dependent upon the relative displacement of two members, one member being associated with the repeater apparatus forming part of the power drive controlled by the signal.

The invention is primarily concerned with such electric distant transmission systems employing two synchronous motors of the Selsyn type, one unit constituting the initiating unit or transmitter and the other unit the cancelling unit or receiver. Each unit has a three phase field and a single phase salient two pole armature. In such a system, the units are in wired connection with a thermionic amplifier so that the latter is controlled in its amplifying action according to the angular displacement between the rotors of the units, the output of the thermionic amplifier being applied to a repeater motor in direct or indirect connection with the rotor of the cancelling unit, the system including an hydraulic power amplier for actuating the gun or other object to be moved as a result of angular movement of the repeater motor. In such a system the rotor of the initiating unit is initially movable through the medium of a predictor or other controlling mechanism, the output of the thermicnic amplifier and direction of current flow being respectively proportional to the angular displacement between the two units and the direction of displacement, movement of the repeater motor thereby taking place according to the direction of displacement and in accordance with the output available from the thermionic amplifier, the repeater motor, by virtue of its direct or indirect connection with the rotor of the cancelling unit, serving to bring the rotors once more into coincidence whilst at the same time transmitting the required motion to the gun or other object to be moved through the medium of the hydraulic power amplifier. Such a form of electric distant transmission system employing Selsyn units forms the subject of copending application Serial No. 435,356, filed March 19, 1942, whilst the hydraulic power amplier forms the subject of copending application Serial No. 435,348, filed March 19. 1942, the hydraulic power amplifier comprising an hydraulic engine preferably of the swashplate actuated type employing a control valve for varying the volume of the supply of the fiuid medium, the torque obtainable` on the output shaft of the amplier being thus dependent on the position of the valve, the valve having either a rotary motion or a combined sliding and rotary movement. The invention is, however, also applicable to any other form of electric transmission system wherein movement of the gun is dependent upon the relative displacement of two members, one member being associated with the signal and the other member being associated with the follow-up apparatus forming part of the power drive controlled by the signal.

In such electric distant transmission systems where the movement of a signal, for example, the rotor of the Selsyn initiating unit is used to originate the movement of the repeater apparatus, the position-of the signal relative to the position of the repeater apparatus must be out of coincidence before a movement of tht,` repeater apparatus takes place in an endeavour to restore concidence. In o-rder to maintain the velocity of the signal equal to that of the repeater appara-tus, an increase of mis-alignment between signal and follower must give rise to a speed increase of the follower whilst a decrease of mis-alignment must decrease the speed of the follower. f

The chief object of the invention is to correct automatically for any angular lag or mis-alignment between the signal and the follower, and furthermore to correct for any electrical lag which may occur in the system so as to obtain complete coincidence in the system throughout.

The hydraulic power amplifier hitherto used incorporates a differential gear interposed between the input shaft and the main controlling valve controlling movement of the output shaft leading to the gun elevating or training mechanism. The invention consists broadly in the interposition of a further diierential between the repeater motor and the input shaft of the hydraulic power amplier, the outer, or planet carrying, member of the differential being driven preferably through the medium of a further small hydraulic power amplifier from the main control valve operating shaft so as to advance the input shaft of the main hydraulic power ampli- -fier automatically and thus obtain complete col'incidence between the signal and follower. By

suitable correction of the gear ratio' connecting the input shaft with the valve operating spindle this correction, may be increased, thus anticipating the electrical lag in the system.

In order that the said invention may be clearly understood and readily carried into effect, the same will now be described more fully with reference to the accompanying drawings in which Fig. l illustrates dagrammatically the disposition of the main component parts of the system, Fig. 2 is a longitudinal section through the power arnplifler-the output shaft of which is connected to the driven load, and Fig. 3 is a longitudinal section through the supplementary power amplifier the input shaft of which is driven from the valve spindle of the amplifier shown in Fig. 2. Figs. 2 and 3 together correspond to Fig. 1 of the before referred to application Serial No. 435,348 to which cross reference is made for a more complete disclosure of details.

In the construction illustrated, the apparatus includes a Selsyn initiating or transmitter unit I, the rotor 2 of which represents the position of the signal. The rotor of the Selsyn unit I is operated from the output shaft of a predictor or other controlling device and is connected with a repeater electric motoru 3 through the medium of a thermionic amplifier 4 and by the same means is ccnnected with the winding of a rotor 5 of a, further Selsyn unit 6 constituting the cancelling unit o-r resetter.

The electric motor 3 through the medium of a differential gear 'I drives the input shaft I4 of an hydraulic power amplifier 9 which, through the medium of its output shaft Il?, serves to move a gun or other object in training or elevation. The details of construction of this power amplifier are shown in Figure 2.

When therrotor of the Selsyn Unit I is out of alignment with the rotor of the Selsyn unit t, current is delivered by the thermionic amplifier 4 to cause angular movement of the repeater motor, in a direction according to the relative direction of -displacement between the two Selsyn rotors.

The torque transmitted to the output shaft l! is under the control of a valve I2 in the hydraulic power amplifier 9, the valve I2 serving to control the duantity f uid supplied to the amplier, and the opening and closing of this valve I2 is under the control of a differential gear I3 therein, shown in Fig. 2, the speed of the output shaft I0 being determined by the opening of the valve and being therefore a function of the'angular displacement between the input shaft I4 and output shaft I0.

It will thus be seen that in accordance with the above description and ignoring the function of the differential gear 1 interposed .between the repeater motor and input shaft I4, there is in the firstV case an angular displacement between the signals, that is to say, between the rotor of the initiating Selsyn unit and the rotor of the Selsyn cancelling unit whose shaft forms a continuation of the main shaft 8 of the electric motor. There is a further angular displacement between the input shaft i4 of the hydraulic power amplifier and its output shaft lli' and this displacement increases in value with the speed of rotation.

As a result of langular movement of the repeater motor 3, the valve I2 will be partially opened, the output shaft Il) being also rotated but not to such an extent as to obtain complete coincidence.

By the provision of the differential gear 'I between the repeater motor shaft and the input shaftV I 4 of the hydraulic power amplifier, this lack of coincidence is rectified. between the motor shaft 8 and the input shaft I4 of the hydraulic power amplifier 9. The valve spindle I of the valve l2 associated with the hydraulic power amplifier operates the input spindle I5 of a further small hydraulic power amplifier I'I which is constructed and adapted to operate in the same manner as the hydraulic power amplifier 9, and is shown in 4 detail in Fig. 3. The amplifier Il through the medium of its output shaft i8 operates the differential gear 1 interposed between the motor shaft 8 and input shaft It of the main hydraulic power amplifier 9 so as to advance the input shaft to correct for the two angular displacements hereinbefore referred to. In this way the differential gear 1 cancels the differential gear I3 situated in the hydraulic power amplifier ii, thus eliminating the angular lag. The gear ratio may be so chosen that this correction also includes the angular lag which exists between roto-r 2 and rotor t, thus tending to reduce the angular lag between the rotor` 2 :and the output spindle it to zero.

' The differential gears l and i3 may be of any suitable construction and are shown diagrammatically. Referring in the first instance to the differential "l, driving and driven gear-wheels 2G and 2I are secured to shafts 8 and i 4, gear wheels 2l! vand 2 I meshing respectively with planet pinions 22 and 23 which themselves intermesh, the latter being mounted upon a planet carrier 24, the latter being in geared connection as shown with the shaft IB. The differential gear i3 is of identical or similar construction, similar reference numerals being employed, the gear wheels 2t and 2l in this case being attached to shafts I4 and I0, the planet carrier 24 being in geared connection with the shaft I5.

For the purpose of understanding the differential gears if it is assumed that the planet carriei` 24 is held stationary, and remembering that gears 22 and 23 are in mesh with each other, and also respectively in mesh with gears 20 and 2l, it will be perceived that there is a direct drive from shaft 8 to shaft I4 which, if gears 22 and 23 are alike and if gears 2li and 2l are alike, would have a one to one relationship. Next assume that the shaft I 4 is held stationary, and it will be apparent that rotation of the gear 2i! will cause the planet carrier 24 to rotate because the meshing gears 22 and 23 can walk around the gear 2i. Then, it is clear that if both the gears 2l and the planet carrier 24 are free to rotate there will be a different action-and as so far discussed the like differential gear at I3 will through the movement of the` planet carrier control the valve I2 to in turn control the rate of rotation of the shaft Iii. As so far described the differential gears introduce their differential action which, in the case of differential I3, is designed to control the valve I2. Returning to the differential gear l, it is apparent that the action of the differential can be modified by applying a control or restraint on either the shaft I4 with its gear 2| or the planet carrier 24. Here it is the planet carrier 24 which is utilized, and this is done as explained by the additional power amplifier Il operated from the shaft I5 that is driven from the planet carrier of the differential I3, the control coming back to the shaft I8 and the gear in mesh with the periphery ofthe planet carrier 24 of the dierential l.

Remembering that the electric motor 3 is under the control of the amplifier i always trying to keep the Selsyn unit 5, which is the follow-up or cancelling unit, in step with the unit I and further remembering that the valve i2 is operated by the differential I3 so that the function of angular dis placement between the shafts I4 and I2 is determined by the extent of opening in valve l2 v(it is apparent that the component of motion of one of two differentially operable members will vary with the resistance to movement of the other component), it should now be apparent that while the differential I3 wi11 introduce the angular dis placement between the shafts I4 and I5, the inherent characteristics of such a construction as disclosed will introduce a lag. But the magnitude ofthis lag, reflected in the speed of the shaft I5, can be used to control a second differential in the same drive (remembering that shaft 3 is in alignment with shaft I4 so Idifferential l is interposed in the shaft drive between the follow-up motor 3 and the differential i3), the control of the differential 1 from the planet carrier of differential I3 being utilized to cancel the lag introduced by the differential I3.

The hydraulic power amplifiers 9 and I1 may, as aforesaid, be assumed to be of identical construction.

Referring now particularly to power amplifier 9 (Fig. 2), rotation of shaft IB is obtained by sliding the Valve I2 so that oil under pressure in pipe 25 passes through port 26 to actuate the pistons of the swashplate arrangement, while simultaneously the sliding movement of I2 uncovers port 2l' to exhaust the oil through pipe 28. Conversely, if hydraulic valve I2 is being slid in the opposite direction, port 2l is exposed to the pressure side and portlZS becomes the exhaust side, while naturally the swash plate turns the opposite direction. It will be seen that rotation of shaft I4 via gears 24 and 29 causes the valve I 2 to slide as indicated above on account of the worm gear 35, and that at the same time, it causes shaft I5 to rotate.

On account `of the differential gear I3, it will be noted that rotation of shaft Il! always tends to close the sliding valve I2, and that therefore for a given load the amount of displacement of valve I2 from its neutral posi-tion determines the speed of shaft IIB; equally there must therefore be a displacement between shaft I4 and I0 in order to rotate shaft Ii), and the higher the speed and the greater the load, the greater valve opening is required and the greater is the angular displacement between I4 and I0.

It will also be appreciated that the amount of angular displacement between I4 and I0 is at all times reflected in a corresponding angular displacement of the shaft I5. As the shaft I5 is coupled to the input spindle I6 of another but smaller hydraulic power amplifier, the shaft IS and therefore the differential gear` l, will be rotated as a function of the rotation of I5, that is the amount of displacement from neutral position of sliding valve I2, and that is in turn the amount of displacement between shaft I4 and shaft Iii. Rotation of the shaft I8 causes shaft I4 to be advanced on the position of shaft 8, and consequently the angular lag obtaining at any moment between it and IG is thereby cancelled, so that angular displacement of the shaft 8 `gives rise to exactly similar angular displacement of shaft The above description is based on the assumption that the same characteristic exists for the speed response of the repeater motor due to angular displacement between the rotors of the Selsyn units as for the speed response of the hydraulic power amplier, due to the angular displacement between the input shaft and output shaft. Should these characteristics be sufficiently different to matter in actual practiceoperation of the ydifferential gear 7 can take place through the medium of cams or similar gearing to match the resulting characteristics. The action of the small hydraulic power amplifier H is irreversible for the torques dealt with, the output shaft forming a heeling point for the differential gear interposed between the electric motor and the main hydraulic torque amplifier. In practice` a controlling valve I9 is included in the oil outflow pipe leading from the small hydraulic power amplifier with the object of restricting the oil flow through the amplifier and eliminating immediate response to minute rapid fluctuation of the main controlling valve in the main hydraulic power amplifier.

The dials and pointersl shown are included merely to show more clearly the operation of the apparatus and form no part of the invention.

What we claim and desire to secure by Letters Patent of the United States is:

l. A power transmission system of the followup or repeater type including a repeater motor, a hydraulic power amplier having an input shaft, a controlling valve, and an operating shaft for said valve, and a differential gear operated from the input shaft of the power amplifier for operating said shaft for said valve, having in combination therewith an additional differential gear interposed between the repeater motor and said input shaft for the purpose of lag correction, said last named differential gear including an outer or planet carrying member and means driven from said valve operating shaft for operating said member so as to advance the input shaft of said hydraulic power amplifier automatically to obtain complete coincidence between the signal and follower.

2. A power transmission system, as claimed in claim l, including an additional hydraulic power amplier interposed between said valve operating shaft of the power amplifier and the outer or planet carrying member of the additional differential gear.

3. A power transmission system, as claimed in claim 1, said additional hydraulic power amplier being interposed between said valve operating shaft of the power amplifier and the outer or planet carrying member of the additional differential gear and including an oil supply pipe and a controlling valve in said oil supply pipe for restricting oil flow therethrough to thereby dampen immediate response to minute rapid fluctuation of the main controlling valve in the main hydraulic power amplifier.

4. A power transmission system comprising a Selsyn transmitter unit operated by the output shaft of a controlling apparatus, a Selsyn receiver unit, a thermionic amplifier in wired connection with said transmitter and receiver units, an electric motor in wired connection with said amplifier and energized by said amplifier as long as there is lack of coincidence between said transmitter and receiver units, the direction of rotation of said motor being determined by the direction of misalignment between the units, said electric motor being mechanically coupled with the rotatable part of said receiver unit to rotate the latter until alignment is restored, an hydraulic power amplifier having a sensitive low torque input shaft, a high torque output shaft and a valve controlling the flow of fiuid to the amplifying mechanism, a differential gear connecting the low torque input shaft with said valve to effect its opening and closing movements and also connected with said high torque output shaft, said output shaft operating the object to be controlled, said electric motor being in driving connection with the input shaft of the power amplier, a differential gear interposed between the driving connection on said electric motor and said input shaft for the purpose of lag correction and means driven from the operating mechanism of said valve and connected with said last named diierental to advance the input shaft of said amplier automatically to obtain complete coincidence between the transmitter and receiver units.

5. A power transmission system as claimed in claim 4 including an additional hydraulic power amplifier interposed between the valve operating mechanism of the main power amplifier and the outei' o1' planet carrying member of the additional differential and including an oil supply pipe incorporating a manually actuated controlling valve for restricting oil ow through said additional power amplifier to thereby dampen immediate response to minute rapid fluctuation of the main controlling valve in the main hydraulic power amplifier.

ARTHUR SPENCER.

JOHANN HERMANN ABBINK-SPAINK.

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