US2883596A

US2883596A - Remote control positioner

Info

Publication number: US2883596A
Application number: US539436A
Authority: US
Inventors: Jr Wilton E Boyd
Original assignee: Alliance Manufacturing Co Inc
Current assignee: Philips Home Products Inc
Priority date: 1955-10-10
Filing date: 1955-10-10
Publication date: 1959-04-21
Anticipated expiration: 1976-04-21

Description

April 1959' w. E. BOYD, JR 2,883,596

REMOTE CONTROL POSITIONER Filed Oct. 10, 1955 2 Sheets-Sheet l Fig.5

INVENTOR.

WILTON E. BOYD JR BYW April 21, 1959 w. E. BOYD, JR

REMOTE CONTROL POSITIONER 2 Sheets-Sheet 2 Filed 001;. 10, 1955 WILTON E. BOYD JR.

"-wiw a United States Patent REMOTE CONTROL POSITIONER Wilton E. Boyd, Jr., Alliance, Ohio, assignor to Alliance Manufacturing Company, Division of Consolidated Electronics Industries Corporation, Wilmington, Del.

Application October 10, 1955, Serial No. 539,436

' 21 Claims. Cl. 318-31) The invention relates in general to control and indicator devices and more particularly to a specific structural form and circuit arrangement of a control device and associated circuits for remotely controlling the position of a movable mount and to indicate the position of this movable mount. The invention may be used with remote control positioners which have recently been used with antenna rotators which are remotely controlled and which have some form of indicator means at the remote control unit. Typically there is a rotator unit mounted at the antenna location which may, for example, 'be a television antenna, and conductors connect the rotator unit to the control and indicator device which may conveniently be placed Within a building; and when used with television equipment, it may be placed near the television receiver. A source of power for the entire rotator and control device is obtained through the control -device.- In prior art forms of antenna rotators a controlled voltage is supplied from the control unit to the rotator unit which selects the direction of rotation; and then as the rotator unit rotates in response thereto, the rotator unit causes a switch to be periodically actuated to send impulses back to the control unit, which impulses are used to steppingly return the indicator unit to a neutral ofi position.

The present invention departs from this former practice by utilizing first and second relatively variable voltages as obtained at the rotator unit in accordance with rotation of this unit, and these relatively variable voltages are returned to the remote control and indicator unit to apply variable magnetic forces to move a contact in a non-step or smooth return movement until a contact is moved to an oif position whereupon the entire rotator and control unit is dc-energized.

An object of the invention therefore is to provide a remote control and indicator unit which utilizes variable magnetic forces to move a contact to a neutral or-otf position.

Another object of the invention is to provide a control and rotator device wherein a manual control knob is moved to engage contacts which then energize the entire unit to rotate an antenna mount which in turn moves a potentiometer obtaining first and second variable voltages with these variable voltages applied to the control and indicator unit to establish relatively variable magnetomotive forces which in turn act on a permeable vane which moves a contact to an ofi position. In addition the magnetomotive forces act additively to release a friction brake and when the entire unit is de-energized, the friction brake is re-applied by a spring. The releasing of the friction brake also establishes tighter engagement of the contact means; and when the contacts are moved to the disengaged position at the end of the followup movement, the spring physically separates the contacts a greater distance so as to prevent any arcing between these contacts.

Another object of the invention is to provide an electrical control unit which will respond to variations in an electrical quantity of a device, yet be insensitive to voltage variations of a voltage source supplying energy to the device having the electrical quantity.

Another object of the invention is to provide a friction brake for a movable part of a control device so that the brake is removed when the device is energized and in operation; and When the device is de-energized, the brake is actuated to hold the movable part of the meter in the previously established position.

Another object of the invention is to provide a control device having a contact and having a coil to establish a variable force in accordance with the variable control quantity and to provide an opposing force in opposition thereto which opposing force is removed when energization to the device is interrupted, so that there is no further tendency for movement of the contact when the energization to the device ceases.

Another object of the invention is to provide an electrical control device with first and second opposing magnetomotive forces, each acting on a permeable movable vane and tending to move this vane in opposite rotational directions and to provide the device with a braking system wherein the opposing magnetomotive forces are actually combined in addition to move the vane in a third direction different from either of the aforementioned opposing directions.

Another object of the invention is to provide a control device which may be used as a remote control and indicator device for the position of a movable mount at a remote location with the movable mount utilizing electrical energy and with a potentiometer in circuit and movable therewith so that the potentiometer in combination with two different coils of the device form a modified bridge circuit, which may be used to establish forces to move a control contact in the device.

Other objects and a fuller understanding of this invention may be had by referring to the following description and claims, taken in conjunction with the accompanying drawings, in which:

Figure 1 is a rear view of the control and indicator device;

Figure 2 is a longitudinal sectional view through the device on the line 22 of Figure 1;

Figure 3 is a front view of the device, with the knob removed;

Figure 4 is a rear view with parts broken away to show the internal construction;

Figure 5 is a sectional View on the line 55 of Figure 2;

Figure 6 is a view similar to Figure 5, but with the friction brake released; and

Figure 7 is a schematic diagram of a circuit arrangement of the control and indicator device in a remote indicating circuit.

The invention includes the control and indicator device 11. This device 11 may have the constructional features of the well-known magnetic or moving coil electrical meters. However, a preferred embodiment of this device 11 is as shown in the Figures 1-6, which includes generally a sheet metal frame 12,

coils

13 and 14, and a movable vane 15 which cooperates with

coils

13 and 14. The frame may have any shape desired and has been shown as having a generally flat body 18 for ease in mounting arrangements. Bars 19 and 20 are bent generally at right angles to the body 18 to hold one end of

core portions

21 and 22. A non-permeable body 23 is mounted on the frame 12 in any suitable manner such as by the peened lugs 24. In this case, the body 23 is made of die-cast zinc for ease in manufacture and ease in holding manufacturing tolerances, although it may be made of any desired material and made in any suitable manner. The body 23 has an annular ring portion 25 and a flat disc portion 26. The disc portion 26 is adjacent the frame 12 and has a central shaft aperture 27 and an eccentrically disposed tongue aperture 28. A sheet metal tongue 29 is formed in a central aperture 30 in the body portion 18 and this tongue 29 is bent generally at right angles to extend through the tongue aperture 28 in the flat disc 26.

The

core portions

21 and 22 have first and

second pole shoes

34 and 35 connected to the respective core portions, and these pole shoes are mounted on the face of the annular ring portion 25 which is remote from the frame 12. A non-permeable support 36 is mounted to the

pole shoes

34 and 35 and may be so mounted by the same means which hold the pole shoes to the annular ring portion 25 which again may be peened lugs 37. The support 36 may also act as a cover for the vane 15. The

pole shoes

34 and 35 are preferably laminated for operation on alternating current and subscribe approximately one hundred seventy degrees of are on the annular ring portion 25. The

core portions

21 and 22 extend at approximately ninety degrees relative to each other and generally parallel to the frame 12. The pole shoes gradually taper to narrower

toe portions

38 and 39.

The vane 15 has a first and a second

semicircular portion

42 and 43 with the first semicircular portion being of considerably smaller radius than the second portion. Both portions are symmetrical about a shaft 44 on which the vane is fixedly attached. The shaft is journalled in the central shaft aperture 27 in the body 23 and in another shaft aperture 45 in the non-permeable support 36. It is so journalled as to permit axial movement as well as rotational movement. A leaf spring 46 is fastened to the non-permeable support 36 as by the rivet 47, and the lower end of the leaf spring engages the rear end of the shaft 44 to move it axially so that the semicircular vane portion 43 frictionally engages a shoulder 48 formed in the annular ring portion 25. The shoulder 48 is approximately two hundred seventy degrees in extent between first and

second stops

51 and 52 which are generally adjacent the

core portions

21 and 22. Because the periphery of the second vane portion 43 is about one hundred eighty degrees of arc, these stops 51 and 52 permit approximately a ninety degree rotation of the vane 15. The tongue 29 extends to a position adjacent the first vane portion 42 so as to form a magnetic path between the vane 15 and the frame 12 through the agency of the tongue 29. The tongue 29 is separated from the semicircular portion 42 by an a r gap 53, and the semicircular portion 43 is separated from the

pole shoes

34 and 35 by

air gaps

54 and 55, respectively.

The Figure 2 especially shows that with the spring 46 urging the vane 15 against the shoulder 48, the vane 15 is to the right of the median plane of the laminated

pole shoes

34 and 35. The shaft 44 and vane 15 has enough axial movement to permit the vane to be moved into the median plane of the

pole shoes

34 and 35 against the urging of the spring 46.

The frame 12 is mounted to a control panel by supports 61 and 62. A shaft 63 is journalled in the control panel coaxial with the shaft 44 and fixedly carries a manual control knob 64. A groove 65 in the shaft 63 receives a (t-shaped ring 66 which holds a spring washer 67 against an indicator needle 68 and urges this indicator needle 68 into frictional engagement with the control panel 60. An indicator legend 69, as shown in Figure 3, may be applied to the control panel for cooperation with the indicator needle 68 to indicate the desired azimuthal direction of the antenna rotator mount. The knob 64 has a wide slot 70 to receive the indicator needle 68, and this wide slot forms a lost motion connection between the knob 64 and needle-68.

The inner end of the shaft 68 carries an insulator block 74 which carries first and

second contact arms

75 and 76.

First and

second contacts

77 and 78 are carried by the

contact arms

75 and 76, respectively, and each has a contact face disposed at approximately a forty-five degree angle to the axis of these contacts.

The shaft 44 fixedly carries a light weight contact blade 80 which may have a counterweight 81, if desired, and the upper end of which carries a double ended contact 82 having faces at a forty-five degree angle for engagement with the

contacts

77 and 78. As shown in the difference between Figures 5 and 6, when the movable vane or armature 15 is in frictional braking engagement with the shoulder 48, the contact 82 is not in axial alignment with the

contacts

77 and 78; yet when the vane 15 is magnetically pulled away from the shoulder 48 against the urging of the leaf spring 46, then the contact 82 may be in axial alignment with the

contacts

77 and 78. The

contacts

77 and 78 are physically spaced and positioned on opposite sides of the contact 82 and move as a unit in an arc with movement of the control knob 64, and the arc of movement is the same as the arc of movement of the contact 82 on the blade 80.

The Figure 7 shows a schematic diagram of the remote control and indicator unit 11 in connection with a rotator unit 85. The rotator unit 85 includes a reversible split-phase induction motor 86 having a rotor 87 and first and second stator windings 88 and 89. The rotor 87 is connected to rotate an antenna mount 90 or other load device and is also connected to move a movable contact blade 91 of a potentiometer 92. The remote control and indicator device 11 includes four interconnecting terminals 93-96, respectively, and the rotator unit 85 includes corresponding interconnecting terminals 97-11 19; respectively. Four conductors 103 interconnect these termi nals. The potentiometer 92 has an end terminal 101 connected to the upper ends of each stator winding 88 and 89 and has another end terminal 102 connected to the interconnecting terminal 100. The movable contact 91 is connected to the interconnecting terminal 99 and the lower ends of the stator windings 88 and 89 are connected to the

terminals

97 and 98.

The remote control and indicator unit 11 includes a transformer 105 having a primary 106 and a secondary 107. The primary 106 has first and

second terminals

108 and 109 and the secondary 107 has first and second terminals 110 and 111 and an intermediate terminal 112. First and second energizing

terminals

113 and 114 are provided which may be connected to an attachment plug 115 for energizing the entire unit. The primary terminal 108 is connected by a conductor 116 to the first energizing terminal 113 and to the leaf spring 46 to provide electrical connection to the double ended contact 82. An indicator lamp 117 may be connected across the

terminals

110 and 112 of the secondary 107, and a variable resistor 118 may be connected between the secondary terminal 110 and the interconnecting terminal 96. First and second directional relays.119 and 120 are provided with energizing coils'121 and 122, respectively. Each relay controls two single-pole normally open contacts denoted by the suifixes A and B. The energizing coil 121 is connected by a flexible lead 123 to the contact arm 76, and the energizing coil 122 is connected by a flexible lead 124 to the contact arm 75.

The relay contact 121A interconnects the secondary terminal 111 and the interconnecting terminal 94, and similarly the relay contact 122A interconnects the secondary second terminal 111 and the interconnecting terminal 93. A condenser 125 is connected across the

terminals

93 and 94 to providethe two phases for the induction motor 86. The relay contact 121B interconnects the primary second terminal 109 and the second energizing terminal 114, and similarly the relay contact 122B interconnects the primary second terminal 109 and the second energizing terminal 114.

The secondary first terminal 110 is connected by a conductor 129 to an end terminal 130 of the indicator coil 13 and the secondary intermediate terminal 112 is connected to an end terminal 131 of the indicator coil 14. The other end terminals of the

coils

13 and 14 are interconnected at the terminal 132 and connected to the interconnecting terminal 95.

Operation The Figures 1-5 and 7 show the entire unit in the neutral or off position with Figure 6 illustrating how the friction brake is released when the control unit is ener- 'gized. Let us now assume that the control knob 64 is grasped by an operator and moved clockwise approximately forty-five degrees. The contact 77 engages the contact 82 for electrical contacting, and this physically moves the contact blade 80 clockwise by approximately this same forty-five degree movement. The only difference in arcuate movement is that first the physical spacing between the

contacts

77 and 82 must be eliminated and this spacing is the reason for the lost motion connection 70 between the knob 64 and the indicator needle 68. Assuming that the

terminals

113 and 114 are energized, the electrical contacting between

contacts

77 and 82 will energize the directional relay 120 to close the contacts 122A and 122B. The closing of contact 122B energizes the primary of the transformer 105 so that voltages are available at the terminals of the secondary 107. This may be a reduced voltage from the usual 115 volt line voltage and may be reduced to something in the order of twenty-four volts, for example. This voltage is applied through the contact 122A to the stator winding 89, and through the condenser 125 to stator winding 88. This makes the rotor 87 rotate in a given direction which, for example, may be a clockwise rotation. This will rotate the contact blade 91 clockwise in the potentiometer 92. The voltage between the contact blade 91 and terminal '101 will thereby increase, and similarly the voltage between contact blade 91 and terminal 102 will decrease. The potentiometer 92 is energized in series with the motor 86 from the secondary 107 so that voltages are available from the potentiometer 92 whenever either relay 119 or 120 is energized. The portion of the transformer secondary between

terminals

110 and 112 plus the potentiometeir 92 provides a means for establishing first and second relatively vaniable voltages. The first voltage may be considered to be that established between the

terminals

131 and 132, and the second voltage may be considered to be that established between the

terminals

130 and 132. These relatively variable voltages are generally complementary and even though variable, add together to form a relatively fixed total voltage. This relatively fixed voltage, it will be seen, is essentially that voltage between

terminals

110 and 112 since this voltage is applied to the two

coils

13 and 14 in series.

As the movable contact blade 91 is gradually moving clockwise toward the terminal 102, the voltage applied to the coil 13 will be gradually reduced toward zero. This is because the contact blade 91 is moving toward a short circuit condition of the coil 13. At the same time this clockwise movement is establishing a continuously increasing voltage on the control coil 14.

When the unit was first energized, that is, by closing

contacts

77 and 82, this energized the motor 86 and the potentiometer 92 and applied voltages to the

coils

13 and 14. These coils established first and second magnetornotive forces which acted in opposition on the movable vane or armature 15. These magnetic forces in opposition were in opposite arcuate directions on the vane 15; however, these first and second magnetomotive forces acted additively in an axial direction on the vane 15. These additive magnetomotive forces are those which release the friction brake between the vane 15 and the shoulder 48. The first magnetomotive force, from the coil 13, travels through the core 21, through the pole shoe 34, across the air gap 54, through the vane 15, the air gap 55, the pole shoe 35, the core 22, and the metal frame 12 to return to the core portion 21 by way of the ear 19. At the same instant of time flux established by the coil 14 travels through the core portion 22, the pole shoe 35, across the air gap 55, through the vane portion 43, across the air gap 54, through the pole shoe 34, the core portion 21, and through the sheet metal frame 12 to return to the core portion 22 through the rear 20. It will be noted that these magnetomotive forces are in opposite directions in the vane 15; and when these magnetomotive forces are approximately equal, the flux from each byapasses through the vane portion 42, the air gap 53, and the tongue 29 to the permeable frame 12. Thus, these first and second magnetomotive forces act in opposition on the vane 15 as far as arcuate direction is concerned. However, because of the axial displacement of the vane 15 and the pole shoes 34 and 35, the two magnetomotive forces act in addition in an axial direction to attempt to pull the vane 15 into the plane of the pole shoes 34 and 35 against the urging of the spring 46. This moves the vane 15 away from the shoulder 48 to release the frictional brake and thus the vane 15 is free to rotate.

The vane and the contact blade have previously been rotated to near the clockwise limit position. This limit position would be where the edge of the semicircular vane portion 43 would abut the stop 52, as shown in Figure 4 since this figure is a rear view. As shown'in the difierences between Figures 5 and 6, this axial movement by the additive combined magnetomotive forces estab lishes the

contacts

77 and 82 in even tighter mutual engagement for good electrical connection. Therefore, this may be considered a magnetic means for holding the contacts in engagement after they are once moved into engagement by the control knob 64.

The gradually increasing first voltage on the coil 14 and the gradually decreasing second voltage on the coil 13 will continually and gradually change the relative magnetomotive forces of these coils which act on the vane 15 in an arcuate direction. These changing magnetomotive forces will thus eventually reach a relative strength whereat the vane 15 is moved to an arcuate position just a little more clockwise than the position to which it was moved by the control knob 64. This will therefore separate the previously established contact between the

contacts

77 and 82. The opening of these contacts will de-energize the relay coil 122 to open contacts 122A and 1223. This de-energizes the entire transformer and de-energizes the motor 86 and potentiometer 92. Likewise it de-energizes the control coils 13 and 14. This de-energization collapses the flux from the two magnetomotive forces and thus the armature 15 is no longer held in the position shown in Figure 6 and instead the spring 46 will axially move the vane 15 into contact with the shoulder 48 to re-establish the friction brake. This holds the contact blade 82 in a definite arcuate position so that the entire unit will not become accidentally energized. Also, the axial movement of the vane 15 and contact 82 by the spring 46 effects a relatively large separation between the

contacts

77 and 82 to prevent any arcing between these contacts. This is a definite advantage of the present invention to provide relatively large movement between small and light contacts without any snap action, as is provided in toggle action switches and the like, to make this control and indicator unit feasible.

If the knob 64 is now moved counterclockwise approximately forty-five degrees so that the indicator needle 68 is positioned approximately vertically, then the contact 78 will electrically contact the contact 82 and physically move it and the vane 15 back to the position shown in the various figures of the drawing. The lost motion connection 70 between the knob 64 and the needle 68 will thus come into play because the knob has been moved in a direction opposite to that in which it was formerly moved; and thus the contact 78 must travel a relatively greater distance in order to physically engage the contact 82. This electrical contacting will again energize the transformer 105 through the relay 121. Energization of this relay will energize the motor 86 for counterclockwise rotation and move the potentiometer contact blade 91 counterclockwise toward the vertical position shown. This also energizes the control coils 13 and 14 gradually increasing the voltage on coil 13 and decreasing the voltage on coil 14. Initial energizetion of these coils again magnetically releases the friction brake on the armature and then the relatively changing magnetomotive forces act on the vane 15 until they finally move it slightly counterclockwise and consequently move the contact blade 8% slightly counterclockwise so that contact 82 is moved to a position out of engagement with contact 78. When this happens, the entire unit is tie-energized and the antenna mount 90 has been moved to the desired location.

The indicator needle 68 is moved with the control knob 64 to indicate the desired position or azimuthal direction of the antenna mount 96, and the indicator lamp 11'7 will be energized upon energization of the entire system and will be extinguished upon de-energization of the entire system so that itsextinguishinent is an indication that the antenna mount has been rotated to the desired location. Therefore, this may be considered, together with the needle 63, to be an indicator of the actual position of the antenna mount 9t). The variable resistor 118 may be used to compensate for different lengths of conductors interconnecting the interconnecting terminals 93 to 16%). Different voltages will actually be applied to the motor 86 and potentiometer 92 in accordance with the voltage drop in the interconnecting conductors 103 which may be anywhere from twenty-five to one hundred fifty feet in length depending upon the physical spacing between the rotating unit 85 and the control unit 11.

The entire unit works well despite varying line voltages because, as the line voltage increases, the first and second variable voltages increase in direct proportion; and therefore the effect of this increasing voltage is counterbalanced by being applied to the

coils

13 and 14 in proportion to the position of the potentiometer contact blade 91.

It will be noted that the control and indicator device 11 together with the rotator unit 85 form an automatic stepless self-positioning rotator operating on the principle of a divided voltage through the potentiometer 92.

There is no impulsing voltages sent from the rotating unit 85 to the control device 11, rather first and second relatively variable voltages are returned to the control and indicator device 11 to magnetically act on the vane 15 to slowly move the contact blade 36* to an off or neutral position which de-energizes the entire system. It also will be noted that the contact points are magnetically held in a closed position until the antenna mount has reached the desired location. The transformer secondary 107 has a voltage tap 112'at a voltage approximately equal to the voltage at the potentiometer terminal 101 to eliminate need for an extra interconnecting conductor between terminal 1531 and terminal 131. This permits the entire system to be interconnected by only four conductors rather than by five conductors. The direction of rotation of the antenna mount 50 is controlled by

relays

119 and 120 closing the circuit. The friction brake 15-48 holds the vane 15 steady in the off position to prevent any false energization of the entire system, and also the indicator needle 68 continuously indicates the position of the antenna mount when the entire system is tie-energized. Also, the de-energization of the entire system permits the spring 46 to retract the contact points to eliminate any arcing, thus prolonging the life and dependability of the contacts and the entire system. It will also be seen that if a conductor were provided between the terminal 101 and the terminal 131, there would thus be established a form of bridge circuit between the, potentiometer 92 and the control coils 13 and 14. This bridge circuit re-establishes itself in neutral or ofi position whenever the voltages on the

coils

13 and 14 are of such relative strength to arcuately act on the vane 15 so that it moves the contact blade to a neutral or off position. The actual circuit shown in Figure 7 is thus a modified bridge circuit because the terminal 131, rather than being connected to the ter minal 101 of the potentiometer 92, is instead connected to a point 112 on the transformer 107 which is at approximately the same potential as terminal 101. This provides first and second relatively variable voltages to the

coils

13 and 14 so that they act the same as they would in an ordinary bridge circuit yet permits elimination of this fifth interconnecting conductor.

The first and second relatively variable voltages are relatively variable electrical signals obtained by some form of a movable means on an electrical impedance 92. The

coils

13 and 14 are signal responsive means which cooperate with the armature 15 to exert first and second opposing forces thereon, which forces are arcuate in direction, and also exert forces in addition generally at right angles to these arcuate forces.

The impedance 92 may be considered a reference means which obtains a variable voltage reference which in connection with the portion of the secondary 107 between

terminals

110 and 112 supplies the relatively variable voltages to the control coils 13 and 14 which also may be considered as electrical signal means or signal responsive means exerting a variable force on the armature or vane 15. These relatively variable voltages on the

coils

13 and 14 exert forces in arcuate directions on the vane 15 which are varied between unbalanced and balanced conditions. As the control knob 64 is moved, which moves both the contact 82 and the vane 15, this sets in motion the chain of events which causes the magnetic forces on the vane 15 to be unbalanced relative to the new position of the vane 15. This unbalanced condition maintains the engagement of the contact 82 and the selected one of

contacts

77 and 78, and the magnetic forces are in such a direction to move the vane toward a balanced condition. As the balanced condition is approached, the resultant force in an arcuate direction on the vane 15 decreases and the balanced condition is reached as the contacts separate. This de-energizes the entire device and thus permits the spring 46 to axially separate the contacts and to re-engage the brake.

Although this invention has been described in its preferred form with a certain degree of particularity, it is understood that the present disclosure of the preferred form has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and the scope of the invention as hereinafter claimed.

What is claimed is:

1. A remote control positioner, comprising, a movable mount, an impedance having movable means moved in accordance with movement of said mount to establish a variable voltage, a frame, a coil mounted on said frame, a vane cooperable with said coil, said coil upon being energized establishing a magnetomotive force in turn establishing a first force to move said vane in a first direction, first and second contact means, control means connected to electrically engage said first and second contact means to establish movement of said mount, means to vary the energization of said coil in accordance with said variable voltage to vary the force in said vane, means connecting said vane to at least one of said contact means to electrically disengage said contact means, means opposing said first force in said vane, brake means coacting with said vane and having engaged and released conditions, means to combine in addition forces from said coil energization means and said opposing means to establish said brake means in said released condition, and means to establish said brake means in said engaged condition and to inhibit the effect of said opposing means upon disengagement of said contact means.

2. A remote control positioner, comprising, a rotatable mount, means including an impedance having movable means driven in accordance with said mount to establish first and second relatively variable voltages, a frame, movable permeable vane means mounted on said frame, first and second coils connected to be responsive to said first and second voltages and first and second magnetomotive forces in said vane means, contact means, control means connected to said contact means to electrically engage same to establish rotation of said mount, said first and second magnetomotive forces establishing forces in said vane means for urging said vane in first and second opposing directions for establishing a follow-up movement relative to said frame to establish an electrically disengaged condition of said contact means, brake means having engaged and released positions and cooperable with said vane means, means to urge said brake means into said engaged position, and means to establish additive forces from said first and second magnetomotive forces to move said vane means in a third direction diiferent from either said first or second direction to move said brake means into said released position.

3. A stepless antenna rotator, comprising, an electrical motor connected for rotating an antenna mount, means including an electrical impedance having a movable contact driven in accordance with rotation of said motor to obtain first and second relatively variable voltages, a magnetic armature mounted for movement along an axis, electromagnetic means cooperating with said armature to exert an unbalanced force thereon at least at a relatively unbalanced condition of said armature and said electromagnetic means, first and second contact means relatively axially movable, friction brake means coacting with said armature and having engaged and released positions, spring means to move said armature in a first axial direction to engage said brake means, manual control means connected to provide relative movement between said first and second contact means for electrically contacting same and connected to establish a relatively unbalanced condition of said armature and said electromagnetic means, means including said electrical contacting of said first and second contact means to provide rotation of said electric motor and energization of said impedance, circuit means interconnecting said electromagnetic means and said impedance to apply said first and second relatively variable voltages to said electromagnetic means to move said armature in a second axial direction against the urging of said spring means to release said brake means, means including said first and second relatively variable voltages applied to said electromagnetic means to reestablish a relatively balanced condition of said electromagnetic means and said armature to relatively move said first and second contact means to a position out of mutual engagement to de-energize said motor and said impedance and electro magnetic means and to re-engage said brake means.

4. A remote control positioner, comprising, a movable mount, means including an electrical impedance having movable means driven in accordance with movement of said mount to obtain first and second relatively variable electrical signals, armature means having an axis and mounted for transverse movements, electrical signal responsive means cooperating with said armature means to exert a force thereon, first and second contact means relatively transversely movable, movable control means connected to provide relative transverse movement between said first and second contact means for electrically contacting same and connected to provide relative transserse movement between said armature means and said signal responsive means, means including said electrical mounted so as to establish contacting of said first and second contact means to energize said impedance and to provide movement of said mount, circuit means interconnecting said impedance and said signal responsive means to supply said first and second relatively variable electrical signals to said signal responsive means to transversely move said armature means, means interconnecting said armature means and one of said first and second contact means to relatively move said first and second contact means to a transverse position out of electrical engagement to effect cessation of movement of said mount and to de-energize said signal responsive means.

5. A remote control positioner, comprising, a movable mount, means including an electrical impedance having movable means driven in accordance with movement of said mount to obtain first and second relatively variable electrical signals, armature means having an axis and mounted for axial and transverse movements, electrical signal responsive means cooperating with said armature means to exert a force thereon, first and second contact means relatively transversely movable, brake means coacting with said armature means and having engaged and released positions, first urging means to urge said armature means in a first axial direction to engage said brake means, movable control means connected to provide relative transverse movement between said first and second contact means for electrically contacting same and connected to provide relative transverse movement between said armature means and said signal responsive means, means including said electrical contacting of said first and second contact means to energize said impedance and to provide movement of said mount, circuit means interconnecting said impedance and said signal responsive means to apply said first and second relatively variable electrical signals to said signal responsive means to transversely move said armature means and to provide movement to said armature means in a second axial direction against the urging of said first urging means to release said brake means, means interconnecting said armature means and one of said first and second contact means to relatively move said first and second contact means to a transverse position out of electrical engagement to effect cessation of movement of said mount and to de-energize said signal responsive means, and deenergization of said signal responsive means permitting said first urging means to move said armature means in said first axial direction to re-engage said brake means,

6. An antenna rotator, comprising, an antenna mount, a motor connected for rotating said antenna mount, means including an electrical impedance having movable means driven in accordance with rotation of said antenna mount to obtain first and second relatively variable elec trical signals, a rotatable and axially movable armature, electrical signal responsive means cooperating with said armature to exert a force thereon, first and second contact means relatively arcuately movable, brake means coacting with said armature and having engaged and released positions, first urging means to move said armature in a first axial direction to engage said brake means, movable control means connected to provide relative arcuate movement between said first and second contact means for electrically contacting same and connected to provide relative arcuate movement between said armature and said signal responsive means, means including said electrical contacting of said first and second contact means to provide rotation of said antenna mount, circuit means interconnecting said impedance and said signal responsive means to apply said first and second relatively variable electrical signals to said signal responsive means to arcuately move said armature and to provide movement to said armature in a second axial direction against the urging of said first urging means to release said brake means, means interconnecting said armature and one of said first and second contact means to relatively move said first and second contact means to an arcuate position out of electrical en- 11 gagement to efiect cessation of rotation of said antenna mount and to de-energize said signal responsive means, and de-ene'rgization of said signal responsive means permitting said first urging means to move said armature in said first axial direction to re-engage said brake means.

7. An antenna rotator, comprising, a motor connected for rotating an antenna mount, means including an electrical impedance having movable means driven in accordance with rotation of said antenna mount to obtain first and second relatively variable voltages, a rotatable and axially movable magnetic armature, electromagnetic means cooperating with said armature to exert a force thereon, first and second contact means relatively arcuately and axially movable, brake means coacting with said armature and having engaged and released positions, spring means to move said armature in a first axial direction to engage said brake means, movable control means connected to provide relative arcuate movement between said first and second contact means for electrically contacting same and connected to provide relative arcuate movement between said armature and said electromagnctic means, means including said electrical contacting of said first and second contact means to provide rotation of said antenna mount, circuit means interconnecting said impedance and said electromagnetic means to apply said first md second relatively variable voltages to said electromagnetic means to arcuately move said magnetic armature and to provide movement to said armature in a second axial direction against the urging of said spring means to release said brake means, means interconnecting said armature and one of said first and second contact means to relatively move said first and second contact means to an 'arcuate position out of electrical engagement to cease rotation of said antenna mount and to de-energize said electromagnetic means, and de-energization of said electromagnetic means permitting said spring means to move said armature in said first axial direction to re-engage said brake means and to physically separate said first and second contact means to prevent arcing therebetween.

8. An antenna rotator, comprising, a motor connected for rotating an antenna mount, means including an electrical impedance having movable means driven in accordance with rotation of said motor to obtain first and second relatively variable voltages, movable control means, indicator means moved in accordance with said control means to indicate the desired posit-ion of said antenna mount, a rotatable and axially movable magnetic armature, first and second contact means relatively arcuately and axially movable, brake means coacting with said armature and having engaged and released positions, spring means in said control and indicator means to move said armature in a first axial direction to engage said brake means, movement of said control means electrically contacting said first and second contact means and physically rotating said first and second contact means, relay means, means including said relay means and said electrical contacting of said first and second contact means to provide rotation of said motor, electromagnetic means in said control and indicator means connected to said impedance to utilize said first and second relatively variable voltages to arcuately move said magnetic armature and to provide movement to said armature in a second axial direction against the urging of said spring means to release said brake means, said armature moving in an arcuate direction to relatively move said first and second contact means to an arcuate position out of electrical engagement to tie-energize said motor and said relay means and said electromagnetic means, and de-energization of said electromagnetic means permitting said spring means to move said trmature in said first axial direction to re-engage said brake means and to physically separate said first and second contact means to prevent arcing therebetween.

9. A stepless antenna rotator, comprising, a reversible electrical motor connected for rotating an antenna mount,

means including an electrical potentiometer having a movable contact driven in accordance with rotation of said motor to obtain first and second complementary voltages each of which is variable and the sum of which remains substantially constant, manual control means including first and second contact means physically spaced apart and movable as a unit in an arc, indicator means moved in accordance with said manual control means and movable in said are to indicate the desired position of said antenna mount, third contact means axially movable and arcuately movable in said arc, a magnetic vane in said control and indicator means connected to rotate and axial- 1y move with said third contact means, friction brake means coacting With said vane and having engaged and released positions, spring means in saidcontrol and indicator means to move said vane in a first axial direction to engage said brake means, arcuate movement of said manual control means and first and second contact means in either direction electrically contacting said third contact means and a selected one of said first and second contact means and physically rotating said third contact means with said first and second contact means, first and second relay means, means including said relay means and said electrical contacting of said third and said selected one of said first and second contact means to provide first and second selected rotations of said electric motor, first and second electromagnetic means in said control and indicator means connected to said potentiometer to utilize said first and second varying complementary voltages to establish opposing forces to arcuately move said magnetic vane in a selected direction and to provide movement to said vane in a second axial direction against the urging of said spring means to release said brake means, said vane moving in said selected arcuate direction to move said third contact means to an arcuate position out of electrical engagement with said selected one of said first and second contact means to tie-energize said motor and said relay means and said electromagnetic means, and de-energization of said electromagnetic means permitting said spring means to move said vane and third contact means in said first axial direction to re-engage said brake means and to physically separate said third contact means and said selected one of said first and second contact means to prevent arcing therebetween.

10. A stepless antenna rotator, corn-prising, a reversible electrical motor connected for rotating an antenna mount, means including an electrical impedance having a movable contact driven in accordance with rotation of said motor to obtain first and second relatively variable voltages, control means including first contact means movable in an arc, second contact means arcuately movable in said are, a magnetic vane in said control means connected to rotate with one of said first and second contact means, arcuate movement of said control means and first contact means electrically contacting said first and second contact means, relay means, means including said relay means and said electrical contacting of said first and second contact means to provide first and second selected directions of rotation of said electric motor, and electromagnetic means in said control means connected to said impedance to utilize said first and second relatively variable voltages to arcuately move said magnetic vane to more said one of said first and second contact means to an arcuate position out of electrical engagement with the other of said contact means to tie-energize said motor and said relay means and said electromagnetic means.

ll. A stepless antenna rotator, comprising, a reversible electrical motor connected for rotating an antenna mount, means including an electrical impedance having a movable contact driven in accordance with rotation of said motor to obtain first and second relatively variable voltages, manual control means including first contact means movable in an arc, indicator means moved in accordance with said manual control means and movable in said are to indicate the desired position of said antenna mount, second 13 contact means arcuately movable in said are, a magnetic vane in said control and indicator means connected to rotate with one of said first and second contact means, arcuate movement of said manual control means and first contact means electrically contacting said first and second contact means, relay means, means including said relay means and said electrical contacting of said first and second contact means .to provide first and second selected directions of rotation of said electric motor, and electromagnetic means in said control and indicator means connected to said impedance to utilize said first and second relatively variable voltages to arcuately move said magnetic vane to move said one of said first and second contact means to an arcuate position out of electrical engage ment with the other of said contact means to de-energize said motor and said relay means and said electromagnetic means.

12. A stepless antenna rotator, comprising, a reversible electrical motor connected for rotating an antenna mount, means including an electrical impedance having a movable contact driven in accordance with rotation of said motor to obtain first and second relatively variable voltages, manual control means including first contact means movable in an arc, indicator means moved in accordance with said manual control means and movable in said arc to indicate the desired position of said antenna mount, second contact means axially movable and arcuately movable in said arc, a magnetic armature in said control and indicator means connected to rotate and axially move with said second contact means, friction brake means coacting with said armature and having engaged and released positions, spring means in said control and indicator means to move said armature in a first axial direction to engage said brake means, arcuate movement of said manual control means and first contact means electrically contacting said first and second contact means and physically rotating said second contact means with said first contact means, relay means, means including said relay means and said electrical contacting of said first and second contact means to provide first and second selected directions of rotation of said electric motor, electromagnetic means in said control and indicator means connected to said impedance to utilize said first and second relatively variable voltages to arcuately move said magnetic armature and to provide movement to said armature in a second axial direction against the urging of said spring means to release said brake means, said armature moving in an arcuate direction to move said second contact means to an arcuate position out of electrical engagement with said first contact means to de-energize said motor and said relay means and said electromagnetic means, and de-energization of said electromagnetic means permitting said spring means to move said armature and second contact means in said first axial direction to re-engage said brake means and to physically separate said first and second contact means to prevent arcing therebetween.

13. A stepless antenna rotator, comprising, a reversible electrical motor connected for rotating an antenna mount, means including an electrical potentiometer having a movable contact driven in accordance with rotation of said motor to obtain first and second complementary voltages each of which is variable and the sum of which remains substantially constant, manual control means including first contact means movable in an arc, indicator means moved in accordance with said manual control means and movable in said arc to indicate the desired position of said antenna mount, second contact means axially movable and arcuately movablein said arc, a magnetic vane in said control and indicator means connected to rotate and axially move with said second contact means, friction brake means coacting with said vane and having engaged and released positions, spring means in said control and indicator means to move said vane in a first axial direc tion to engage said brake means, arcuate movement of said manual control means and first contact means in exassase cess of a predetermined amount electrically contacting said first and second contact means and physically rotating said second contact means with said first contact means, relay means, means including said relay means and said electrical contacting of said first and second contact means to provide first and second selected directions of rotation of said electric motor, electromagnetic means in said control and indicator means connected to said potentiometer to'utilize said first and second varying complementary voltages to arcuately move said magnetic vane and to provide movement to said vane in a second axial direction against the urgingof said spring means to release said brake means, said vane moving in an arcuate direc-' tion to move said second contact means to an arcuate position out of electrical engagement with said first contact means to de-energize said motor and said relay means and said electromagnetic means, de-energization of said electromagnetic means permitting said spring means to move said vane and second contact means in said first axial direction to re-engage said brake means and to physically separate said first and second contact means to prevent arcing therebetween, and second indicator means actuated in accordance with movement of said vane for indicating rotation of said antenna mount.

14. A stepless antenna rotator to move an antenna mount from an initial position to a desired position, com prising, a reversible electrical motor connected for rotating an antenna mount, means including an electrical potentiometer having a movable contact driven in accordance with rotation of said motor to obtain first and second complementary voltages each of which is variable and the sum of which remains substantially constant, manual control means including first contact means movable in an are from a first to a second position corresponding to said desired position, lost motion means, indicator means movable through said lost motion means in accordance with said manual control means and movable in said are to indicate the desired position of said antenna mount, second contact means axially movable and arcuately movable in said arc, a magnetic vane in said control and indicator means connected to both rotate and axially move with said second contact means, friction brake means coacting with said vane and having engaged and released positions, spring means in said control and indicator means to move said vane in a first axial direction to engage said brake means, arcuate movement of said first contact means from said first to said second position in excess of a predetermined amount which corresponds to said lost motion means establishing electrical contact between said first and second contact means and physically rotating said second contact means with said first contact means, relay means, means including said relay means and said electrical contacting of said first and second contact means to providefirst and second selected directions of rotation of said electric motor to rotate said antenna mount to said desired position, electromagnetic means in said control andindicator means connected to said potentiometer to utilize said first and second varying complementary voltages to arcuately move said magnetic vane and to provide movement to said vane in a second axial direction against the urging of said spring means to release said brake means and to magnetically urge together said first and second contact means, said vane moving in an arcuate direction to move said second contact means to an arcuate position out of electrical engagement with said first contact means to de-energize said motor and said relay means and said electromagnetic means, de-energization of said electromagnetic means permitting said spring means to move said vane and second contact means in said first axial direction to re-engage said brake means and to physically separate said first and second contact means to prevent arcing therebetween, and second indicator means actuated in accordance with movement of said vane for indicating rotation of said antenna mount.

15. A stepless antenna rotator, comprising, energizing 15 means, a control unit having a frame, a shaft journalled in said frame, first and second control coils on said frame, first and second pole shoes cooperating with said first and second control coils, respectively, a permeable vane fixed relative to said shaft and adapted to be in magnetic cooperation with said pole shoes, a movable commoncontact moved with said shaft, a control knob substantially axially aligned with saidshaft, first and second movable control contacts spaced a fixed distance apart and movable as a unit by said control knob on an are about the axis of said shaft and disposed on either side of said movable common contact, a reversible electric motor, a potentiometer having a movable tap, means for controlling first and second directions of rotation of said motor and energize tion of said potentiometer from said energizing means by the electrical contacting of said movable common contact and the selected one of said first and second movable control contacts asmoved by said knob, energizetion of said potentiometer establishing first and second variable control voltages thereon with respect to said mov able tap, means for moving said potentiometer tap .in accordance with rotation of said motor, means for utilizing said first and second control voltages to control the relative energization of said first and second control coils, and the relative energization of said control coils effecting movement of said vane and movable common contact to open the previously established electrical contact between said common contact and the selected one of said first and second control contacts.

16. A homing stepless antenna rotator, comprising, a remote control unit and a rotator unit with interconnecting conductors therebetween, said remote control unit including, a transformer having a secondary with first and second end terminals and an intermediate terminal, said remotecontrol unit having a frame, first and second control coils on said frame, first and second pole shoes cooperating with said first and second control coils, respectively, a permeable vane axially movable and rotatable relative to said pole shoes and adapted to be in magnetic cooperation with said pole shoes, a shaft journalled in said frame and fixedly carrying said vane for rotation therewith, a movable contact blade moved with rotation of said shaft, a control knob substantially axially aligned with said shaft, first and second movable control contacts spaced at fixed distance apart and movable as a unit by said control knob on an arc about the axis of said shaft and disposed on either side of said movable contact blade, a forward and a reverse relay each having an energizing coil and a single throw contact, first, second, third, and fourth interconnecting terminals for said interconnecting conductors on said remote control unit and fifth, sixth, seventh, and eighth interconnecting term nals for said interconnecting conductors on said rotatorunit, means for connecting one end of said first control coil to said transformer secondary intermediate terminal, means for connecting one end of said second control coil to said secondary first terminal and to said fourth interconnecting terminal, means for interconnecting the other ends of said control coils and connecting same to said third interconnecting terminal, means for energizing said transformer, means for providing energization to said movable contact blade on said shaft, means for connecting said forward relay energizing coil between said first control contact and said energizing means, means for connecting said reverse relay energizing coil between said second control contact and said energizing means, means for connecting said forward relay contact between said first interconnecting terminal and said secondary second terminal, means for connecting said reverse relay contact between said second interconnecting terminal and said secondary second terminal, said rotator unit including a reversible motor having first and second windings, means for connecting said first motor winding to said fifth interconnecting terminal, means for connecting said second motor winding to said sixth interconnecting terminal, a potentiometer having first and 16 second terminals and a movable tap, means for moving said tap by rotation of said motor, means for connecting the other ends of said motor windings together and to said first terminal of said potentiometer, means for connecting said movable tap to said seventh interconnecting terminal, means forconnecting said second potentiometer terminal to said eighth interconnecting terminal, and said interconnecting conductors including first, second, third, and fourth conductors interconnecting the said first, second, third, and fourth interconnecting terminals with said fifth, sixth, seventh, and eighth interconnecting terminals, respectively. v

17. A homingstepless antenna rotator, comprising, a remote control unit and a rotator unit with interconnecting conductors therebetween, said remote control unit in cluding, a step-down transformer having a primary and a secondary each with first and second end terminals and said secondary having an intermediate terminal, said remote control unit having a frame, first andsecond control. coils on said frame, first and second pole shoes cooperating with the proximal ends of said first and second control coils, respectively, a permeable vane axially movable and rotatable relative to said pole shoes and adapted to be in magnetic cooperation with said pole shoes, a shaft journalled in said frame and fixedly carrying said vane for rotation therewith, permeable return means cooperating with a central portion of said vane and the distal ends of said control coils, a movable contact blade moved with rotation of said shaft, first and second movable control contacts spaced a fixed distance apart and movable as a unit on an are about the axis of said shaft and disposed on either side of said movable contact blade, a control knob axially aligned with said shaft, an indicator movableby said knob, lost motion means between said knob and said indicator, means to move said first and second control contacts from said control knob, frictions means between said knob and said frame to maintain the set position of said knob, a forward and a reverse relay each having an energizing coil and first and second single throw normally open contacts, first, second, third, and fourth interconnecting terminals for said interconnecting conductors on said remote control unit and fifth, sixth, seventh, and eighth interconnecting terminals for said interconnecting conductors on said rotator unit, means for connecting one end of said first control coil to said transformer secondary intermediate terminal, means for connecting one end of said second control coil to said secondary first terminal and to said fourth interconnecting terminal, means for interconnecting the other ends of said control coils and connecting same to said third interconnecting terminal, first and second alternating current source energizing terminals, means for connecting said primary first terminal to said first energizing terminal,

means for connecting said primary first terminal to said movable contact blade on said shaft, means for connecting said forward'relay energizing coil between said first control contact and said second energizing terminal, means for connecting said reverse relay energizing coil between said second control contact and said second energizing terminal, means for connecting said forward relay first contact between said first interconnecting ter minal and said secondary second terminal, means for connecting said reverse relay first contact between said second interconnecting terminal and said secondary second terminal, means for connecting said each of said forward and reverse relay second contactsbetween said primary second terminal and said second energizing terminal, a condenser connected across said first and second interconnecting terminals, said rotator unit including an alternating current two-phase reversible induction motor having first and second stator windings, means for connecting said first stator winding to said fifth interconnecting terminal, means for connecting said second stator winding to said sixth interconnecting terminal, a potentiometer having first and second terminals and a movable tap, means for moving said tap in accordance with rotation of said motor, means for connecting the other ends of said stator windings together and to said first terminal of said potentiometer, means for connecting said movable tap to said seventh interconnecting terminal, means for con meeting said second potentiometer terminal to said eighth interconnecting terminal, and said interconnecting conductors including first, second, third, and fourth conductors interconnecting the said first, second, third, and fourth interconnecting terminals with said fifth, sixth, seventh, and eighth interconnecting terminals, respectively.

18. A remote control positioner, comprising, a movable mount, reference means responsive to movement of said mount to obtain a variable voltage reference, movable means operatively connected with first contact means, electrical signal means responsive to a variable voltage to exert a force on said movable means to cause motion thereof, second contact means movable relative to said first contact means to provide electrical contact, control means for moving said second contact means, means including said electrical contact of said first and second contact means to energize said reference means and provide for movement of said mount, circuit means to interconnect said reference means and said electrical signal responsive means to energize same whereby the force on said movable means is varied betwen unbalanced and balanced conditions responsive to the variable voltage reference on said reference means first to maintain engagement of said first and second contact means during said unbalanced condition and a subsequent disengagement of said first and second contact means as said balanced condition is approached to effect cessation of movement of said mount and to de-energize said electrical signal means.

19. A remote control positioner, comprising, a movable mount, reference means responsive to movement of said mount to obtain a variable voltage reference, movable means operatively connected with a first contact and mounted for axial and transverse movements, electrical signal means responsive to a variable voltage to exert a force on said movable means to cause motion thereof, second contact means movable relative to said first contact means to provide electrical contact, brake means coacting with said movable means and having engaged and released positions, first urging means to urge said movable means in a first axial direction to engage said brake means, control means for transversely moving said second contact means, means including said electrical contact of said first and second contact means to energize said reference means and provide for movement of said mount, circuit means to interconnect said reference means to said electrical signal responsive means to energize same to transversely move said movable means and to provide movement to said movable means in a second axial direction against the urging of said first urging means to release said brake means whereby the transverse force on said movable means is varied between unbalanced and balanced conditions responsive to the variable voltage reference on said reference means first to maintain engagement of said first and second contact means during said unbalanced condition and a subsequent disengagement of said first and second contact means as said balanced condition is approached to effect cessation of movement of said mount and to de-energize said electrical signal means, and de-energization of said electrical signal means permitting said first urging means 18 to move said movable means in said first axial direction to re-engage said brake means.

20. A remote positioner, comprising, in combination, motor means connected for rotating a mount, reference means driven in accordance with rotation of said motor means to obtain first and second relatively variable voltages, an armature mounted for movement along an axis, force means cooperating with said armature to exert an unbalanced force thereon at least at a relatively unbalanced condition of said armature and said force means, first and second contact means relatively axially movable, brake means coacting with said armature and having engaged and released positions, urging means to urge said armature in a first axial direction to engage said brake means, control means connected to provide relative movement between said first and second contact means for electrically contacting same and connected to establish a relatively unbalanced condition of said armature and said force means, means including said electrical contacting of said first and second contact means to provide rotation of said motor means and energization of said reference means, circuit means interconnecting said force means and said reference means to apply said first and second relatively variable voltages to said force means to move said armature in a second axial direction against the urging of said urging means to release said brake means, means including said first and second relatively variable voltages applied to said force means to re-establish a relatively balanced condition of said force means and said armature to relatively move said first and second contact means to a position out of mutual engagement to deenergize said motor means and said reference means and force means and to re-engage said brake means.

21. In a remote control positioner having a movable mount, comprising, in combination, reference means responsive to movement of said mount to obtain a variable reference, movable means operatively connected with first contact means, electrical signal means responsive to said variable reference to exert a force on said movable means to cause motion thereof, second contact means movable relative to said first contact means to provide electrical contact, control means for moving said second contact means, means including said electrical contact of said first and second contact means to energize said reference means and provide for movement of said mount, circuit means to connect said reference means to said electrical signal responsive means to energize same whereby the force on said movable means is varied between unbalanced and balanced conditions responsive to the variable reference on said reference means first to maintain engagement of said first and second contact means during said unbalanced condition and a subsequent disengagement of said first and second contact means as said balanced condition is approached to efiect cessation of movement of said mount and to de-energize said electncal signal means.

References Cited in the file of this patent UNITED STATES PATENTS