US3264530A

US3264530A - Rotary actuator

Info

Publication number: US3264530A
Application number: US164568A
Authority: US
Inventors: Gerald H Leland; John L Cahill
Original assignee: Ledex Inc
Current assignee: Ledex Inc
Priority date: 1962-01-05
Filing date: 1962-01-05
Publication date: 1966-08-02
Anticipated expiration: 1983-08-02

Description

g- 2, 1966 e. H. LELAND ETAL 3,264,530

ROTARY ACTUATOR Filed Jan. 5, 1962 INVENTORS GEE/1L0 H. LELAND BY JOHN 231%:

United States Patent 3,264,530 ROTARY ACTUATOR...

Gerald H.-Leland and John L. Cahill, Dayton, 0hio, as-

signorsto Ledex, Inc, Dayton, Ohio, a corporation of Ohio Filed Jan. 5, 1962, Ser. No. 164,568 Claims. (Cl. 317-1592) This invention relates to rotary actuators adapted to convert an axial thrust to rotary movement, and more particularly, to an improved rotary actuator construction of the type described and claimed in association with an electromagnetic actuator in United States letters Patent No. 2,496,880, issued to George H. Leland, granted February '7, 1950. However, the invention is not necessarily so limited.

An object of the present invention is to provide an improved mechanism for converting axial movement into rotary movement.

The basic mechanism, in its original form shown in the aforesaid patent, No. 2,496,880, constituted a rotary solenoid including an electromagnet, an armature movable toward the magnet upon energization of the magnet and a shaft connected to the armature for movement therewith as the armature is attracted by the magnet. A plate is carried by the armature and arranged in opposed relation to a part fixed with relation to the electromagnet.

The plate and the aforesaid fixed partare separated by rotatable elements, preferably'balls. The plate or. the

fixed part, or both of them, are provided with a pluralityv the-deep end thereof. After each energization-of the coil, the plate returns to its initial position,-whereupon the ball elements again occupy a position at the shallow ends of the recesses. commercial success in its original form and with minor variations since it is of such simpledesign and capable of a million or more repeated operations.

After extended use, however, portions of the mechanism become worn and the operation of the actuator be-v comes erratic. Mutilation of the endedges of the recesses due to the impact of the ball elements against the recesses during operation of the mechanism is one'factor leading toward erratic operation of the mechanism. Another source of erratic operation due to wear is at the interface between the armature and the core. In normal operation, the armature approaches the core but never comes closer to the core than by a predetermined minimum distance termed the minimum separation or air gap.

armature contactthe core, the magnetic retention of the armature and core causes the armature to stick to the core; that is, the armature may not break away from the core upon deenergization of the magnet coil as rapidly as desired. Therefore, the mechanism may not be reset in time for the next operation.

A. further object of this invention is to prolong the useful life of rotary actuators by reducing the effects of the wear described above.

Other objects and advantages reside in the construction of parts, the combination thereof, the method of manufacture and the mode of operation, as will become more apparent from the following description.

Upon attraction of .the.

This particular mechanism has found wide Should. the minimum air gap become too small, or should the.

3,264,53ll Patented August 2, 196.6

In the drawings,

FIGURE 1 is an end elevational View of a rotary solenoid unit embodying theimprovements of the present invention.

FIGURE 2 is an. enlarged fragmentary sectional. view taken substantially along the lines 22 of FIGURE 1.

FIGURE 3 is a sectionalview taken substantiallyalong, the lines 3-3 of FIGURE I and disclosing the preferred embodiment of the invention described herein;

FIGURE 4 is a sectional view similar to FIGURE 3 of a second embodiment of the invention described herein.

FIGURE 5 is a sectional view similar to FIGURE} showing a third embodiment of the invention. 7

FIGURE, 6 is a section view similar toFIGURE 3,

showing still another embodiment of the invention.

Referring. to thedrawings in detail, the rotary solenoid comprises a housing which is preferably cylindrical'in form and which includes a ferromagnetic cup-shaped cas-f. ing 10 having a mounting plate 12 at its open end. i A

ferromagnetic element 14 is arranged concentricwiththe casing 10 and press fit therein.

shown) engaged within wells or recesses in the element 14. An annularsolenoid coil 18 surroundsthe core 16 within thecasing 10, the coil being separated from the core and the casing by a suitablev insulating member 20.

Coil 18. and core 16 comprise a conventional electrornagnet which may be electrically energized through suit- I ableleads (not shown). The

members

10, 12, 14, .16.. and 18, each remain in a relatively fixed position during operation of the. actuator- Hence, these elements. may conveniently be termed a fixed assembly.

The. central portion-of the mounting plate .12. is proend of the shaft 2-6.. For this purpose, the armature 30 is provided with a central bore or axial aperture 32.while the forward portionof .the shaft 26 is splined or knurled, as indicated at 34, and is press-lfit within the bore 32'. The armature 30-and shaft 26 are permitted to slideQ axially relative to the. fixed assembly comprising the" core 16, the coil 18, the plate 12 and the casing 10. v The smaller diameter of the coil 18 is larger than the diameter of the armature 30. so that. the armature 50 may rnove axially therein. Limitations upon the axial movement of v the armature 30 and the shaft 26 will be discussed below.

It is evident that the magnetic field created upon energization of the coil 18 will draw the armature 30 axially into the casing 10. This axial motion is converted to a rotary motion to be impressed upon the armature 30 and the shaft 26; by thefol-l-owing means. IntegralQWit-h the cup-shaped casing 10 and forming an .aper-tured base for an end portion thereof is an annular inwardly directed flange portion 3 6. The flange portion 3 6 may :be termed a fixed plate. The aperture within this; plate has .a' diameter slightly greater than that of the armature sogsq as not to restrictitsaxial motion. The casing 10 including its flange portion 36, is ferromagnetic toprovide a flux path for the magnetic field created upon energization of the coil 18. 'For best performance, the air gap between the plate or flange portion 36 .and the armature Sills as small as possible. A movable disc or plate 38 ,is fixedly. attached tothe armature 30 for. axial and rotary move;,,

ment therewith in parallel, spaced relation to the outer surface of the flange portionor fixed plate 36.

A cylindrical inwardly directed portion of the element 14 provides a core 16 for the solenoid... The mounting plate 12 may besecured to..' the element 14 by screws 15 provided with heads .(not .1

The opposing surfaces of the disc 38 and the flange portion 36 are each providml with three equally spaced arcuate, inclined recesses 40 and 42 respectively. The disc or plate 38 is oriented initially with respect to the flange portion 36 such that the ends of the recesses 40 are substantially aligned with the ends of the recesses 42. As shown in FIGURE 2, the bases of the

recesses

40 and 42 are oppositely inclined. Disposed between each pair of opposing

recesses

40 and 42 is a rotatable element, shown in FIGURES 2 and 3 as a ball bearing 44. A spring 46, housed within the hub portion 22, or some other biasing means, causes the ball bearings 44 normally to occupy the extreme shallow ends of the

recesses

40 and 42. To prevent the ball elements 44 from falling out of the aligned recesses 40 and 42, a flange may be formed on the shaft 26 adjacent to the back side of the element 14. Conveniently a snap ring (not shown) may be seated within an annular groove (not shown) in the shaft 26 located Within the hub portion 22 of the plate 12.

In operation, electrical energization of the coil 18 creates a magnetic field drawing the armature 30 into the coil 18. The disc 38 accordingly is driven inwardly toward the flange portion 36 of the cup-shaped casing 10. The inclined recesses 40 and 42 cooperate with the ball bearings 44 to permit axial motion of the disc 38 only if the disc 38 also rotates along the ball bearings 44 which roll along the cam surfaces formed at the bases of the

recesses

40 and 42. That is, relative movement of the

recesses

40 and 42 toward the ball elements 44 causes the plates to rotate. The result is that the axial motion of the armature 30 is converted to a rotary motion of the plate 38. Since the plate 38 and armature 30 are driven upon energization of the coil 18, the resulting operation may be termed a power stroke. FIGURE 2 shows the relative positions of a recess 40, a recess 42 and a ball element 44 at the end of a power stroke. Note that the ball element 44 in FIGURE 2 is cupped between the deep ends of the opposed recesses 40 and 42.

When the coil 18 is deenergized, a spring 46 within the hub 22, or other suitable return means, restores the movable assembly comprising the shaft 26, the armature 30, and disc or plate 38 to its initial angular position, thus resetting the rotary mechanism. This return movement of the movable assembly is, for convenience, termed the return stroke.

The apparatus described above produces an angular displacement of the shaft 26 each time the coil '18 is energized, the displacement being counter-clockwise as viewed in FIGURE 1 for the particular structure shown in the drawings. The direction of rotation during the power stroke may be reversed by inverting the inclination of the

recesses

40 and 42. It is to be noted that, in this particular embodiment, the shaft 26 is so attached to the armature 30 that it is both rotated and driven axially upon each energization of the coil 18. Similarly, during the return stroke, the shaft 26 is rotated in the opposite direction by suitable means, which as described above, may comprise the spring 46 housed within the hub 22. The rotary mechanism converts the rotary movement imparted to the shaft 26 into an axial movement of the movable assembly outwardly so that the armat-ure 30 moves away from the core, that is, to the left as viewed in FIG- URE 3.

As previously mentioned, rotary mechanisms of the type described above are capable of a million or more operations. However, after extended use, rotary mechanisms of this type operate erratically, partially due to the mutilation of the end edges of the recesses and the ball elements caused by the impact of the ball elements against the recesses during operation. Also, erratic operation results when the air gap between the core and the armature becomes so small that the armature does not rapidly break away from the core upon deenergization of the electromagnet.

The number of satisfactory operations may be greatly increased in accordance with this invention by interposing low friction bearer means between a portion of the fixed assembly and a portion of the movable assembly. In FIGURE 3, the low friction bearer means comprises a plurality of ball bearings 50 caged between the opposing faces of the core 16 and the armature 30 in surrounding relation to the shaft 26. For this purpose, opposed, annular ball receiving recesses are formed concentric with the shaft 26 within the opposed surfaces of the core 16 and armature 30. The ball bearings 50 may be made from a plastic, such as nylon, or metal. To avoid magnetic retention in the bearings 50, they must have a 10W magnetic susceptibility. The ball bearings 50 are of such diameter that, at the position of closest approach of the armature to the core, an adequate air gap still exists between the armature and the core. The closest approach, of course, is at the end of the power stroke. The position of the parts at the end of the power stroke is illustrated in FIGURE 3. On the other hand, the ball bearings 50 must be sufficiently large that, at the end of the return stroke, they are still retained within the opposed recesses in the core 16 and the armature 30. In other words, their diameter must be greater than the maximum air gap. With this construction, it is unnecessary to provide a separate cage for the ball bearings 50.

In addition to insuring that a satisfactory air gap is maintained between the core 16 and the armature 30, the ball bearings 50 perform another important function. At the beginning of the power stroke, the ball bearings 50 are only loosely retained between the armature and the core. There is thus no resistance to the initial axial thrust of the movable assembly and the resultant motion thereof. After the power stroke is underway, however, the ball elements 50 serve as bearers preventing further axial movement of the armature 30. Once the axial movement of the armature 30 is stopped, there is no further rotary thrust. The armature 30 and the plate 38, however, continue rotation because of their rotary momentum. Were the ball bearings 50 not interposed between the armature and the core, the continued axial movement of the armature 30 would cause a continued rotary thrust to be imparted to the armature 30 and the plate 38. Therefore, without the ball bearings 50, the impact of the ball elements 44 against the deep end edges of the

recesses

40 and 42 would be much greater. Conversely, the interposition of the ball bearings 50 between the armature and the core reduces the impact of the ball elements 44 against the end edges of the

recesses

40 and 42, thus serving to prolong the useful life of the actuator.

Although the axial thrust of the armature 30 is limited, the ball bearings 50 present very little resistance to continued rotary movement of the armature 30 and the plate 38. Accordingly, the full rotary stroke remains possible. That is, the plate 38 and the armature 30 may rotate until the ball elements 44 reach the position shown in FIGURE 2 at the deep ends of the

recesses

40 and 42.

Referring to FIGURE 4, a second embodiment of this invention is disclosed therein and like reference numbers are applied to like parts. In the embodiment of FIG- URE 4, an annular recess 52 is formed within the surface of the core 16 opposed to the armature 30 in surrounding relationship to the shaft 26 and concentric therewith. A ring 54 is nested within the recess 52. The ring 54 may be made of a plastic or an elastomeric material. Of course, the ring 54, as with the ball elements 50, must be of a low friction material and must have a low magnetic susceptibility. To retain the ring 54 within the recess 52, the outer edges of the recess 52 may be peened, as indicated at 56, over portions of the ring 54. The ring 54 serves the same function as the ball bearings 50 described in connection with FIGURE 3. The area of contact between the ring 54 and the armature 30 is sufficiently small that the ring 54 does not create an undue resistance to rotation of the armature 30.

In FIGURE 5, a third embodiment of the invention is disclosed which is quite similar to FIGURE 4. However, in this case, a ring 58, similar to the ring 54, is secured to the flange portion 36 of the casing 10, again in surrounding and concentric relation to the shaft 26. The interposition of the ring 58 between the flange portion 36 and the plate 38 again serves to insure a minimum air gap between the armature 30 and the core 16 and further serves to snub or stop the axial rotation of the armature 30 and plate 38 without substantially restricting the rotary movement of these members.

In FIGURE 6, a plurality of ball bearings 60 are mounted for rotation within an annular recess formed concentrically with the shaft 26 in the outer surface of the flange portion 36 of the casing 10. The ball bearings 60 correspond in function to the elastomeric ring 58. The edges of the recess within the flange 36 may be peened over to retain the ball bearings 60 therein. As in the case of each of the embodiments described above, the ball bearings 60 serve as low friction bearers to limit the axial movement of the armature 30 and the plate 38 without substantially restricting the rotary movement thereof and further insuring an air gap between the armature 30 and the core 16.

Another advantage in each of the aforedescribed structures is a reduction in the noise accompanying operation of the actuators. The precise reasons for the noise reduction are unknown. However, much of the noise reduction may be attributed to the reduced rotary thrust.

Although the presently preferred embodiment of the device has been described, it will be understood that within the purview of this invention various changes may be made in the form, details, proportion and arrangement of parts, the combination thereof and mode of operation, which generally stated consist in a device capable of carrying out the objects set forth, as disclosed and defined in the appended claims.

Having thus described our invention, we claim:

1. In a rotary actuator, the combination comprising: a fixed assembly including a casing and an electromagnet; a movable assembly including an armature mounted for axial and rotary movement relative to said fixed assembly and a plate attached to said armature .for movement therewith; a rotatable element mounted between said plate and a surface portion of said fixed assembly, one of said plate and said surface portion having an arcuate inclined recess therein within which said rotatable element rolls, said armature being attracted axially toward said electromagnet upon energization thereof whereupon said armature and said plate undergo both axial and rotary movement relative to said fixed assembly, said rotary movement being limited by the arcuate length of said recess; and low friction bearer means interposed between said fixed assembly and said movable assembly limiting axial movement of said movable assembly without substantially restricting its rotary movement.

2. The structure of claim 1 wherein said bearer means comprises a ring member secured to said surface portion.

3. The structure of claim 2 wherein said surface portion is located on said casing.

4. The structure of claim 1 wherein said bearer means comprises a plurality of ball bearings mounted on said surface portion.

5. The structure of claim 1 wherein said movable assembly is mounted on a shaft journalled for axial and rotary movement within an aperture in said fixed assembly.

6. The structure of claim 5 wherein said bearer means comprises a ring member surrounding said shaft and secured to said electromagnet.

7. The structure of claim 5 wherein said bearer means comprises a plurality of ball bearings housed between said armature and said electromagnet, said ball bearings surrounding said shaft.

8. In a rotary actuator, the combination comprising: a fixed assembly including a casing; a movable assembly including a plate mounted for axial and limited rotary movement relative to a surface portion of said fixed assembly; means responsive to axial movement of said movable assembly toward said fixed assembly to impart limited rotary movement to said movable assembly; and low friction bearer means interposed between said fixed assembly and said movable assembly limiting axial move ment of said movable assembly toward said fixed assembly without substantially restricting its rotary movement.

9. The structure of claim 8 wherein said bearer means v comprises a plurality of ball bearings mounted on said surface portion.

10. The structure of claim 8 wherein said bearer means comprises a ring member secured to said surface portion.

References Cited by the Examiner BERNARD A. GILHEANY, Primary Examiner.

BROUGHTON G. DURHAM, Examiner.

G. HARRIS, 1a., Assistant Examiner.

Claims

1. IN A ROTARY ACTUATOR, THE COMBINATION COMPRISING: A FIXED ASSEMBLY INCLUDING A CASING AND AN ELECTROMAGNET; A MOVABLE ASSEMBLY INCLUDING AN ARMATURE MOUNTED FOR AXIAL AND ROTARY MOVEMENT RELATIVE TO SAID FIXED ASSEMBLY AND A PLATE ATTACHED TO SAID ARMATURE FOR MOVEMENT THEREWITH; A ROTATABLE ELEMENT MOUNTED BETWEEN SAID PLATE AND A SURFACE PORTION OF SAID FIXED ASSEMBLY, ONE OF SAID PLATE AND SAID SURFCE PORTION HAVING AN ARCUATE INCLINED RECESS THEREIN WITHIN WHICH SAID ROTATABLE ELEMENT ROLLS, SAID ARMATURE BEING ATTRACTED AXIALLY TOWARD SAID ELECTROMAGNET UPON ENERGIZATION THEREOF WHEREUPON SAID ARMATURE AND SAID PLATE UNDERGO BOTH AXIAL AND ROTARY MOVEMENT RELATIVE TO SAID FIXED ASSEMBLY, SAID ROTARY MOVEMENT BEING LIMITED BY THE ARCUATE LENGTH OF SAID RECESS; AND LOW FRICTION BEARER MEANS INTERPOSED BETWEEN SAID FIXED ASSEMBLY AND SAID MOVABLE ASSEMBLY LIMITING AXIAL MOVEMENT OF SAID MOVABLE ASSEMBLY WITHOUT SUBSTANTIALLY RESTRICTING ITS ROTARY MOVEMENT.