US3142789A - Bidirectional positioning device - Google Patents

Description

July 28, 1964 vC. R. RHODES BIDIRECTIONAL POSITIONING DEVICE Filed July 13, 1960 I8 ROTATION INVENTOR. CHESTER R. RHODES BY Km AGENT United States Patent 3,142,789 BIDIRECTIONAL POSITIONING DEVICE Chester R. Rhodes, 206 W. Stardell St., Whittier, Calif. Filed July 13, 1960, Ser. No. 42,630 11 Claims. (Cl. 317-189) My invention relates to an electro-mechanical device and particularly to an electrically-energized magneticallyactuated bidirectional stepping device.

While the desirability of having a positioning device capable of actuation in either direction of rotation according to selected energization it is evident the prior art has been largely incapable of fulfilling the need.

- I have found it possible to accomplish selective bidirectional stepping in a novel structure having a relatively few parts, which has a strong end of step torque, a high torque to electrical power input ratio and a brake action upon the output shaft when a step is not in progress.

' The structure is comprised of a magnetic core having three axially spaced pole pieces, each having plural aligned circumferentially projecting poles. Between the pole pieces are two separate solenoids. An armature having slats of magnetic material operationally aligned with said poles surrounds the same. Each of said slats is shaped to provide an air gap of minimum reluctance for rotation of the armature in one direction, but not in the other direction. By energizing one of said solenoids with electric current the armature is caused to rotate in one direction and by energizing the other solenoid, in the opposite direction.

Substantially midway in the rotational step an auxiliary electrical contact is closed. This energizes the second solenoid. Because of the altered magnetic configuration at this time, the magnetomotive force exerted by both solenoids is additive. This gives desirable certainty to accomplishment of the step under adverse electrical, magnetic or mechanical conditions.

An output shaft journaled free of the armature has a flatted gear. A pair of oppositely disposed pawls are attached to the armature by a single pin so positioned with respect to the flatted gear that an excursion of the armature rotates the gear a fraction of a revolution corresponding to the pitch between the teeth of the gear. One projection at one extremity of what has been characterized as a pair of pawls engages the teeth of the gear for rotation in one direction and the opposite projection engages a tooth of the gear for rotation in the opposite direction.

In order that the output shaft may remain stationary when not being stepped regardless of severe vibration or other extraneous circumstances a polygonal drum is attached to that shaft in mechanical phase with the flatted gear. A pair of spring biased brake arms bear upon this drum and so retain the output shaft against spurious rotation to whatever degree may be desired. The degree of retention is determined by the force exerted by the spring.

An object of my invention is to provide a bidirectional positioning device in which the direction of rotation is completely selectable by the mode of electrical energization.

Another object is to accomplish bidirectional stepping with a device of relatively few parts.

Another object is to accomplish stepping with a strong terminal force.

Another object is to provide a relatively high torque for stepping in relation to the electrical power employed.

Another object is to provide immobilization of the stepped shaft when stepping is not in progress.

Other objects will become apparent upon reading the following detailed specification and upon examining the accompanying drawings, in which are set forth by way of illustration and example certain embodiments of my invention.

FIG. 1 shows a side elevation of my bidirectional positioning device,

FIG. 2 shows an end elevation of the same,

FIG. 3 shows a sectional elevation of the magnetic structure along section 33 in FIG. 1,

FIG. 4 shows the variation of actuating tor que as a function of rotation,

FIG. 5 is a schematic electrical circuit diagram. In FIG. 3 numeral 1 indicates a central cylindrical core, having low magnetic retentivity and formed of a material such as Armco ingot (soft) iron. In FIG. 1, 2 is the left end pole piece and 3 is the right end pole piece. The central pole piece 4 has an axial thickness approximately three times that of either end pole piece. The central pole piece 4 is shown in end view in FIG. 3. Three poles 4, 5 and 6 are seen extending radially from core 1. Similar and aligned poles are also found on the end pole pieces 2 and 3. All pole pieces are preferably one piece with core 1; all being machined from a single piece of stock, although any method by which this magnetic structure may be fabricated from individual pieces with low reluctance joints is satisfactory.

Left coil, or solenoid, 7, has the function of initiating motion of the armature in one direction and of supplying additional magnetomotive force to aid the right coil, or solenoid, 8, in completing motion in the opposite direction. By the same token, coil 7 aids the motion initiated by coil 8. For 28 volt operation each coil may be formed of approximately 3,200 turns of #33 AWG wire, the resistance thereof being approximately 50 ohms. Both of these coils are wound in the same direction; aiding. Separate connections are brought out for connection according to FIG. 5.

Looking at my device from the end shown in FIG. 2, for counterclockwise rotation coil 7 is energized first. This occurs because of the low magnetic reluctance at the coil 7 end of the device occasioned by circumferential extension 12 on slat 11 and corresponding extensions on the other slats, all to be further explained. In an analogous manner, for clockwise rotation coil 8 is energized first.

Left armature end-disk 9 is circular and is constructed of a non-magnetic material such as aluminum, or perhaps of a structurally stable insulator, such as diall phthalate, Myclex, etc. This disk serves to support the several slats 11, 14 and 15, all of which are seen inFIG. 3. The other end of each slat is supported by a similar armature end-disk 10. These end-disks are fastened to the core structure previously described for rotation by bearings. These may be ball bearings, or phosphor-bronze or graphite-bronze sleeve bearings.

As will be noted particularly in FIG. 3, each of the armature slats 11, 14 and 15 have a circumferential curvature consonant with the armature end- disks 9 and 10 and also with the outer circumference of poles 4, 5 and 6. This is so that the magnetic reluctance between the poles and the slats will be a small amount. The manner in which rotation in one direction is accomplished by exciting one coil first and rotation in the opposite direction by exciting the other coil first is seen by a careful examination of FIG. 1, in combination with FIG. 3. It is seen that extension 12 causes the reluctance to be considerably less to the lower pole of pole piece 2 (the one behind pole 5; that is, in alignment therewith, in FIG. 3) than to the upper and forward pole thereof (aligned with pole 6). When coil 7 is energized the flux flows particu larly through the part of core 1 under that solenoid, out

through center pole "piece 4, through slat 11 and the circumferential extension of the same 12 and back through end pole piece 2. Whether the flux flows in the direction indicated, or in the opposite direction is unimportant; the point is that the path outlined is theone of lowest reluctance. The magnetic force thus produced tends to reduce the reluctance even more and so the armature revolves counterclockwise as viewed in FIG. 2, as has been mentioned.

By the same process, but because of the .opposite circumferential direction of extension 13, when coil 8 is initially energized the magnetic flux flows around the right hand side of the structure of FIG. 1 and motion of the armature in the clockwise direction occurs. It is to be noted that my bidirectional motions occur because of assymetric magnetic structures and not because of magnetic polarization wherein opposed coils produce a flux that either attracts or repels a permanent magnet member. Slats 11, 14 and 15 are also formed from non-retentive Armco ingot iron, as was the stationary magnetic structure.

A left stationary end support 16 is provided as part of an outer frame of my device. Attached to it is a tube 17 through which external connections from the coils, etc. are brought beyond the rotatable armature. .A circumferential slot is cut in the left armature end-disk 9 so that this member may rotate unimpeded as far as rotation is required. A specific mechanical stop 18 in the form of a projection inward from end support 16 extends into the again circumferentially slotted armature end-disk 9. This. second slot has a specific circumferential length that limits the excursion of the armature in either direction to an arc of motion suited to progress the pawl and gear mechanism to be later described.

Right stationary end support 19 has the same general nature as the left support 16 and in addition serves to mount the remaining elements of my device. The two end supports are joined structurally by three spacer rods. These have not been shown in FIG. 1 in order that the novel magnetic structure would be clearly illustrated. Considering now particularly FIG. 2, the drive pawl is shown at 20. The projections at each extremity will be noted. The mechanism is shown in the extreme position for stepping motion counter-clockwise. The pawl is driven through pin 21, which pin is attached to right armature end disk 10. Flatted gear 22 is fastened to output shaft 23, which latter has a bearing in right stationary end 19. The output shaft is colinear with the axis of the armature but is not directly connected to the armature. The only connection is through pawl 20 and gear 22. As shown, the pawl has just completed a counterclockwise excursion against one of the teeth of the gear; having advanced the gear and output shaft one step, such as 36, one-tenth of a circumference. Gear 22 is shown with ten teeth. The bearing for the output shaft may be any of the types previously mentioned.

A brake drum 24 has a polygonal periphery of ten flats. These are aligned with the flats of the flatted gear 22. Right brake arm 25 and left brake arm 26 both press against flats of the drum during times of non-actuation. In the actuated position of FIG. 2 the left arm is removed from the drum. This occurs because the upper projection of the arm is contacted by pawl 20 in its actuating excursion. From FIG. 1 it will be noted that brake drum 24 is positioned to the right of flatted gear 22 and that therefore the extension 27 extends to the left in order to engage pawl 20. The right brake arm also has an upper projecting extension, 28.

A tension spring 29 is attached to each of brake arms 25 and 26 relatively near the bottom thereof. This causes a constantly exerted force against brake drum 24. This is from both arms when the device is not being actuated and by one when it is being actuated, as shown in FIG. 2. The spring constant is chosen to provide a necessary and sufficient braking effect upon the output shaft, but such as to be within the torque capabilities of the magnetic elements. Such a spring may be fabricated in many ways; one example being ten convolutions of approximately No. 26 AWG. spring steel wire, with a diameter of the order of one-eighth inch.

The brake arms 25, 26 are attached to stationary end support 19 by means of pivot pin 30. Thus spaced from the support and held under the head of the pin, the arms are positioned in line with the drum 24. Each of the arms have a hub thickness only half of the thickness of-the arms and these hubs are offset on left and right arms so that both fit on the pin within the axial-distance equal to the thickness of only one brake arm.

While considerable choice of materials is possible for the recited elements, I have employed bronze for the brake arms, duraluminum for the stationary end supports and machine steel of appropriate hardness for the pawl, flatted gear, brake drum and shafts.

Auxiliary contacts cam 32 is the actuating element of the auxiliary contacts group employed to give high terminal torque. It surmounts armature slat 14 near the armature end-disk 10. This is shown in full lines in FIG. 1 and in dotted lines in FIG. 2. It is centrally located with respect to slat 14, circumferentially. It is constructed of aninsulator having durable mechanical properties, such as linen Bakelite.

Circumferentially removed from the central rest posi tion of the armature slat 14 are movable left auxiliary contact 33 and stationary left auxiliary contact 34. These are mounted in similarly identified contact arms 35 and 36. The contacts may be of silver and the arms of beryllium copper. A left auxiliary contact support of linen Bakelite or equivalent 37 is attached to right stationary end support 19 relatively far removed from the rest position of slat 14. Upon support 37, double insulated support 38 is mounted. The latter holds both contact arms 35 and 36, insulated one from the other.

A right auxiliary contact support 39 is provided symetrically opposite the left support 37. Right contacts and arms are also provided, positioned as mirror images of the left contacts and arms previously described with respect to the central rest position of slat 14., The right contacts and arms are not seen in either FIGS. 1 or 2 because of positions behind other important elements. However, the placement and function thereof is evident.

Both the left and the right arms of the movable designation are moved toward the corresponding stationary auxiliary contacts by cam 32 when the armature has completed approximately half of its full excursion. It will be understood that these elements can be proportioned and positioned so that this is readily possible. The situation is the samewhether the armature excursion is to the right or the left (in FIG. 2). I

FIG. 4 shows the result of such auxiliary contacting and FIG. 5 the circuit diagram of the necessary connections.

In FIG. 5 a common electrical input terminal 55 connects to the center connection of a series-aiding arrangement of solenoidal coils 7 and 8. Terminal 56 is connected to a source of electric current along with terminal 55 when counter-clockwise motion of the armature is desired. When the resulting excursion due to excitation of coil 7 has been half accomplished movable auxiliary contact 33 contacts fixed contact 34. It is then seen that a circuit is completed through coil 8 with respect to the energized terminals55 and 56. This is so directed as to increase the total magnetomotive force acting upon the several armature slats and since these have now passed beyond the initial slat assymetry with respect to the poles of the solenoid magnetic circuit the magnetic effect is to cause rotation until the maximum area of slat and pole coincide. V

For rotation in the other direction the opposite set of auxiliary contacts are mechanically closed. This set is generically identified by reference numeral 39. The mo? tion in this second direction is initiated by connecting a source of electric current between contacts 55 and 57. This initially energizes coil 8, and after switch 39 closes, coil 7 also, in aiding relation. Capacitor 58 is for arc extinguishment and may be of half microfarad capacitance with a voltage rating of 400 volts in a practical case.

In FIG. 4 the torque exerted by the magnetic circuit withone coil alone energized and starting from the central rest position of the armature is shown by curve 51. The torque, as measured in foot pounds, is the ordinate and the abscissa is the rotation of the armature, in degrees of angle rotated through. Curve 51 has an initially relatively high value because of the asymmetry of the armature slats with respect to the poles and the fact that the force exerted between the two is largely tangential. At a degree of rotation that may be selected by the adjustment of the space between mating contacts, such as contacts 33, 34, and importantly by altering the length of cam 32, these contacts close and the second coil is also energized. In FIG. 4 this closure occurs at approximately 18. The torque is now more than doubled its prior value at the 18 rotation point and decreases somewhat as full rotation is reached according to curve 52. Curves 51 and 52 are from practice. In this way it is seen how I accomplish high terminal torque.

It will be understood that the armature is returned to its central position by the force of tension spring 29 exerted through arms 25 or 26 and projections 27 or 28 (depending upon the direction of rotation) upon pawl 20 and hence pin 21.

I have also provided a homing contact and self-interrupting arrangement comprised of elements to now be described; Element 40 is a stationary homing contact and 41 a movable homing contact. These are of silver. These are mounted on movable homing contact arm 42 and a stationary ditto 43, both of beryllium copper. An asymmetric step cam 44 is formed of linen Bakelite and is mounted centrally of movable contact arm 42. A homing contact actuating lever 45 coacts with the step cam. The lever is provided with a fulcrum near the center thereof in the form of pin 46, which is fastened to right stationary end support 19. The upper end of lever 45 contacts a lower extremity of armature end-disk 10.

7 Contact 40 and 41 are normally closed, but open the common coil circuit (55) each time the armature turns. This provides a self-interrupting aspect, so that a prolonged application of voltage across either pair of actuating terminals of the device results in only a pulse flow of current of sufficient duration to actuate it. If pulses are provided in the form of excitation provided this contactarrangement is not required.

It will be understood that an important application of my device is to step multicontact switches from one contact to another. One example is a three-gang Wafer type rotary switch assembly, each Wafer having ten contacts (corresponding to the ten position flatted gear).

In order that a homing, or return to original position aspect be provided, the actuating voltage is fed through a switch wafer having ten positions but only nine contact balls. Repeated actuation thus produces a rotational response save on the tenth position, which is thus identified be inoperability, and operation resumed by an additional shunting circuit that is closed manually or by equivalent automatic means.

In common withthe prior contact construction, 47 is the stationary homing contact support and may be constructed of linen Bakelite. Similarly, element 48 is the movable homing'contact support.

Certain modifications of my invention are possible.

The auxiliary contacts 33 and 34 are required to be open during the first part of any excursion of the armature. .These have been described as normally open in themselves and as appropriately closed by cam 32 contacting the movable contact 33 at half way through the excursion. This construction maybe reversed by simple mechanical interchange and the contacts held openby the presence of the cam 32 and the appropriate one closed by the cam moving away from it.

Brake drum 24 may be provided with shallow holes in the center of each flat and the arms 25, 26 provided the mating projections which then act to secure the output shaft from rotation save when the flatted gear is rotated a the rotation excursion, insuring that a positive action will be completed.

Other applications of my device consist of supplying relative power in increments for computer-type encoding, to position potentiometers or other variable resistors at specific values, and to operate multiposition valves.

Other modifications may be made in arrangement, size and proportions of the illustrative embodiment shown without departing from my invention.

Having thus fully described my invention and the manner in which it is to be practiced, I claim:

1. In a device having an armature and a magnetic structure internal thereto for rotation of said armature by magnetic force to a terminal amplitude,

' first means for increasing the torque upon said armature at said terminal amplitude comprising,

plural second means disposed upon said magnetic structure for providing magnetic force,

third means to energize a second means,

and fourth means mechanically related to said armature to energize an additional said second means upon rotation of said armature substantially half of said terminal amplitude of rotation.

2. The device of claim 1 in which said plural second means for providing magnetomotive force comprise plural coils related to said magnetic structure for separate initial energization to initiate rotation of said armature in 0pposite directions.

3. In a rotary magnetic device having an armature and a magnetic circuit structure having aligned poles for the rotation of said armature partially around said structure,

first means for providing increased torque at the terminal amplitude of said rotation comprising a first and a second source of magnetomotive force, second means to energize said first source,

third means to energize said second source, mechanical means circumferentially related to said armature to actuate said third means upon rotation of said armature an amount less than terminal amplitude;

said second source related to said magnetic circuit structure to provide additional magnetomotive force upon said armature from said less than terminal amplitude to said terminal amplitude of rotation.

4. The magnetic device of claim 3 having, in addition, a polygonal drum mechanically related to said armature and a pair of mechanically biased brake arms bearing upon said drum to retain said drum at terminal amplitude of rotation in the absence of further said magnetomotive force.

5. In a rotary electro-rnagnetic device having a rotationally asymmetric armature and a rotationally symmetric magnetic circuit structure coactive therewith for bi-directional rotation of said armature by reluctance reduction,

means for providing increased terminal torque for a given armature rotation comprising operationally interchangeable first and second electrical means disposed within said armature and upon said magnetic circuit structure for providing magnetomotive force,

' electrical contacts connected to said second electrical means mechanically related to said armature to actuate said electrical contacts upon rotation of said armature an amount less than the full .amount of said given armature rotation;

said second electrical means related to said magnetic circuit structure to provide additional magnetomotive force upon said armature from an amount less than the full amount of said given armature rotation to the full amount of said given armature rotation in either direction of said bi-directional rotation.

6. A magnetic device having plural magnetic circuits for selectively rotating one armature in either direction comprising a stationary magnetic structure having more than two groups of radially projecting poles, an armature having plural circumferential magnetic elements adjacent to said poles, means to selectively supply said magnetic structure with magnetomotive force, said magnetic elements circumferentially related to said poles such as to provide a magnetic path of minimum reluctance for rotation in one direction upon one of said magnetic circuits being supplied with magnetomotive force and to provide a magnetic path of minimum reluctance for rotation in the other direction upon the other of said magnetic circuits being supplied with magnetomotive force.

7. A rotary electro-magnetic device having two magnetic circuits for rotating one armature in either of two directions comprising a central core, three spaced disks thereon, each said disk having the same number of radially projecting poles, an armature having circumferential slats surrounding said poles, said slats circumferentially related to said poles such as to provide a magnetic path of minimum reluctance for rotation in one direction upon one of said magnetic circuits being supplied With magnetomotive force and to provide a magnetic path of minimum reluctance for rotation in the other direction upon the other of said magnetic circuits being supplied with magnetomotive force.

8. A rotary electromechanical device comprising a core having plural spaced poles, plural electrical means to magnetically energize said poles, an armature surrounding said poles, said armature journaled for rotation, plural elements of magnetic material upon said armature for rotating said armature by magnetic attraction of said elements toward said poles upon the magnetic energization thereof, each of said elements disposed to provide a magnetic circuit of minimum reluctance for rotation of said armature in one direction upon energization of one said electrical means and for rotation of said armature in the opposite direction upon energization of another said electrical means, plural electrical contacts connected to said plural electrical means, means to close said electrical contacts connected to said electrical means associated with the magnetic circuit having initially higher reluctance upon said armature having rotated a part of the full excursion thereof, the magnetomotive force of the electrical means thus energized adding to the magnetomotive force previously existing.

9. The device of claim 8 having in addition an output shaft and means mechanically related to said armature to both return said armature to its initial position for the next rotation thereof and to restrain the rotation of said armature shaft.

10. A rotary device electrically operable to give a change of position of an output shaft comprising a magnetic core having axially spaced pole pieces, each of said pole pieces having poles aligned one with the other, coils of wire Wound upon said core between said pole pieces, an armature surrounding said poles, said armature journaled for rotation, slats of magnetic material disposed around said armature for magnetic attraction toward said poles upon the passage of an eleotric'current through one of said coils, each of said slats shaped to provide an air gap of minimum reluctance for rotation of said armature in one direction upon passage of current through one said coil and for rotation in the opposite direction upon passage of current through another said coil, auxiliary electrical contacts adjacent to said armature, means attached to said armature to close the electrical circuit of 3 said .coil that initially had the higher reluctance magnetic gap upon said armature having rotated part of the full angular excursion thereof, the magnetomotive force of the coil thus energized adding to the magnetomotive force of the coil originally, energized,,means related to said armature to return the same to said initial position for the next rotative excursion, an output shaft, a toothed element upon said output shaft, a pawl having a pair of oppositely disposed projections, said pawl attached to said upon an electric pulse to give a change of position to an output shaft comprising a cylindrical core of magnetic material having three equally axially spaced pole pieces, each of said pole pieces having three circumferential poles aligned one with the other, two coils of wire wound for magnetic reinforcement upon electrical energization upon said core between said pole pieces, an armature surrounding said poles, said armature journaled for rotation coaxially with said core, three slats of magnetic materialcircumferentially disposed around said armature for magnetic attraction toward said poles'upon the passage of electric current through one of said coils, each of said slats circumferentially relieved of material on opposite sidesat opposite ends to provide an air gap of minimum reluctance for rotation of said armature in one direction upon passage of electric current through one said coil and for rotation in the opposite direction upon passage of current through the other said coil, two pairs of stationary auxiliary electrical contacts disposed adjacent to said armature mechanically biased to remain closed, a linear cam attached to said armature shaped to open the said electrical contact connecting the electrical circuit to that coil having the higher magnetic reluctance gap for the direction of rotation chosen, said cam shaped to close the electrical circuit of said coil initially having the higher reluctance magnetic gap upon said armature having rotated half of the full angular excursion thereof, the magnetomotive force of the coil thus energized adding to the magnetomotive force of the coil originally energized, said slats shaped to remove said high reluctance condition upon said half rotation of said armature, a spring related to said armature to return the same to said initial position for the next rotative excursion, the direction thereof determined by which of said coils is energized; an output shaft, a flatted gear upon said output shaft, a pawl having a pair of oppositely disposed projections, said pawl attached to said armature and related to said gear to rotate said gear a fixed fraction of a revolution, one said pawl projection positioned to rotate said gear upon rotation of said armature in one said direction and the other said projection positioned to rotate said gear upon rotation of said armature in the other said direction; pivoted opposed brake members bearing upon said output shaft, a spring between said members proportioned to provide breaking upon said output sufficient to prevent rotation thereof except upon rotation of said flatted gear by a said projection.

References Cited in the file of this patent UNITED STATES PATENTS 710,951 Barclay Sept. 27, 1904' 921,046 Wilson May 11, 1909 --1,877,480 Osborne Sept. 13, 1932 2,928,916 Bonanno Mar. 15, 1960 3,001,107 Rhodes Sept. 19, 1961 FOREIGN PATENTS 414,688 Great Britain July 30, 1934'

Claims (1)

1. IN A DEVICE HAVING AN ARMATURE AND A MAGNETIC STRUCTURE INTERNAL THERETO FOR ROTATION OF SAID ARMATURE BY MAGNETIC FORCE TO A TERMINAL AMPLITUDE, FIRST MEANS FOR INCREASING THE TORQUE UPON SAID ARMATURE AT SAID TERMINAL AMPLITUDE COMPRISING, PLURAL SECOND MEANS DISPOSED UPON SAID MAGNETIC STRUCTURE FOR PROVIDING MAGNETIC FORCE, THIRD MEANS TO ENERGIZE A SECOND MEANS, AND FOURTH MEANS MECHANICALLY RELATED TO SAID ARMATURE TO ENERGIZE AN ADDITIONAL SAID SECOND MEANS UPON ROTATION OF SAID ARMATURE SUBSTANTIALLY HALF OF SAID TERMINAL AMPLITUDE OF ROTATION.

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