US2972467A

US2972467A - Magnetically operated actuator

Info

Publication number: US2972467A
Application number: US858889A
Authority: US
Inventors: Wilbert M Gilman
Original assignee: Rivett Lathe & Grinder Inc
Current assignee: Rivett Lathe & Grinder Inc
Priority date: 1959-12-11
Filing date: 1959-12-11
Publication date: 1961-02-21
Anticipated expiration: 1978-02-21

Description

W. M. GILMAN MAGNETICALLY OPERATED ACTUATOR Feb. 21, 1961 2 Sheets-Sheet 1 Filed Dec. 11, 1959 Feb. 21, 1961 w, GlLMAN 2,972,467

MAGNETICALLY OPERATED ACTUATOR Filed Dec. 11, 1959 2 Sheets-Sheet 2 I I Mafia/Z72 6267/1472 5% FM, H

United States Patent Wilbert M. Gilman, Lathe & Grinder, of Massachusetts Filed Dec. 11, 1959, Ser. No. 858,889 7 Claims. (Cl. 251-438) Wellesley, Mass., assignor to Rivett Inc., Brighton, Mass, a corporation The present invention relates to an improved magnetically operated actuator, and is herein disclosed in a preferred form as embodied in a direct current solenoid type actuator in which the solenoid armature is given a relatively small movement toward and away from the magnetic source and is at the same time given a turning movement by suitable mechanical means.

It is a principal object of the invention to provide a magnetically operated actuator of the type referred to which is well adapted for eflicient and certain operation with a minimum expenditure of power to shift longitudinally hydraulic valve and similar controllers which are moved with varying degree of resistance and difiiculty from one to another position.

It is more specifically an object of the invention to provide a novel and improved motion conversion device which is particularly adapted for converting a rotary component of motion of an actuator which may be of the general type described to a linear motion, which operates with a minimum frictional loss, is extremely compact, and is readily set up to vary the force exerted upon the actuated controller without substantial change in the power input to the device as may be required during the travel of the controller from one to another position.

With these and other objects in view as may hereinafter appear, the several features of the invention consist in the devices, combinations and arrangement of parts hereinafter described and claimed, which together with the advantages to be obtained thereby will be readily understood by one skilled in the art from the following description taken in connection with the accompanying drawings in which:

Fig. 1 is a view partly in section of a solenoid actuated four-way valve illustrating particularly a shiftable valve spool or valving element and one of the two direct current magnet actuators associated therewith;

Fig. 2 is an exploded isometric view of the cam unit for converting rotational movement of the magnet actuator into a linear motion for actuating the valve spool;

Fig. 3 is a sectional view taken on a line 3-3 of Fig. 1 illustrating particularly the arrangement of the motion conversion device of Figs. 1 and 2;

Fig. 4 is an enlarged detailed sectional view illustrating particularly-the motion conversion device and adjacent the parts being valve spool in e s Fig. 5 is a sectional view similar to left hand magnet actuator has been energized and with the valve spool fully advanced to the right;

Fig. 6 is a detailed sectional view taken on a line 6-6 of Fig. 7 of a modified form of a motion conversion device including an elastic hinge for effecting a guided movement in an axial direction; and a Fig. 7 is a sectional view taken on a line 7-7 of Fig. 6.

The magnetically operated actuator which forms the subject matter of the present invention comprises gen- Fig. 4 in which the erally a rotatable magnet and magnet assembly in which the armature has imparted thereto a rotational movement by means of a cam and follower connection as it is drawn axially, and in combination therewith a motion conversion device comprising two superimposed cylindrical bodies axially aligned with the armature, of which one is connected to be moved longitudinally and rotationally by the armature and the other, which may be defined as the output element of the actuator, is shifted only in a longitudinal direction by means of a cam and follower connection between said cylindrical bodies. In the combination referred to the rotary armature and magnet assembly is preferably of the type having a direct current magnet and a contoured cam and follower connection for imparting rotational movement to the armature which will provide a substantially even torque versus angular position characteristic for the said assembly. The motion conversion unit of applicants improved magnetically actuated actuator includes a cam and follower connection which is contoured to provide an operating characteristic which is combined most efiiciently with the operating characteristic of the magnet and armature assembly to provide a new and useful multiplied axial motion of the output element of the device with a desired force versus point in axial stroke characteristic along the length of the stroke of said output member.

This improved actuator has been found particularly valuable for use in a low energy circuit for the shifting of hydraulic valves and similar controllers which at certain points of their travel may encounter a heavy resistance which would normally be overcome only by the expenditure of energy greatly in excess of the capacity of such a low with the present invention a motion conversion unit is combined with the rotary magnet and armature assembly above described in such a manner as to provide a combined electrically and mechanically powered impulse which will be sulficient actuator has the further advantage that even where the energy is available, substantial savings and power may be effected by virtue of the fact that it becomes unnecessary to utilize oversize actuating components in order to overcome points of heavy resistance above referred to in the movement of the controller.

The particular embodiment of the invention shown in the drawings comprises a magnetically actuated hydraulic four-way valve having a valve body 10 and a valve spool 12 shiftable from the neutral position shown in Fig. l to two alternative limit positions. It will be noted that the valve spool 12 is acted upon at each end by coiled centering springs including at the right hand end of the stem a spring 14 seated between a fixed end abutment 16 and a washer 18 which engages against the valve spool.

a shouldered portion of the valve spool 12.

The hydraulic valve above generally described is adapted to be actuated by means of two direct

current solenoid actuators

28 and 30 mounted at opposite ends of the valve body 10, said solenoid actuators being of a type having an armature axially shiftable through a relatively small distance and having further mechanical means for effecting a rotational movement of the armature simultaneously with the longitudinal movement thereof.

In the illustrated construction there is provided between each of the magnetic actuators referred to and the valve spool 12 a motion conversion device for converting the rotary movement of the armature into a controlled lengthwise movement. Inasmuch as the magnetic actuators and motion conversion devices at the opposite ends of the valve body are identical, only the magnetic actuator and motion conversion device shown at the left in Fig. l have been fully illustrated and will be described in detail.

The magnetic actuator 30 specifically comprises a casing which is secured to the left hand end of the valve body 10, and an electromagnet including a coil 32 rigidly mounted in the casing. An armature 34 is provided, adapted for axial and rotational movements with respect to the coil 32 and casing 30. v

The means disclosed for imparting rotary movement to the armature comprises a plate 35 which is connected with the armature for both axial and rotary movement therewith. This plate is arranged on the outer side thereof and in opposed relation to the end wall of the relatively fixed electromagnet outer core 36, and the opposed surfaces of the wall and plate are each provided with three arcuate recesses or grooves 37, 38, the recesses in the plate being opposed to the corresponding recesses in the wall. The inclined recesses are so arranged that when the armature is in its normal or inoperative position to the left, shallow end portions of the recesses of each pair will be in overlapping relation one to another. Rotatable elements, preferably balls 40, are supported in the respective pairs of recesses. When the magnet is energized and the armature moves toward the same, the pressure of the plate on the balls causes the plate to rotate as it moves axially due to the inclined cam surfaces of the recesses.

To increase the torque on the armature at the beginning of its axial move when the pull of the magnet thereon is relatively weak, the inclination of the bottom sur face of each recess may be substantially greater adjacent the shallow end thereof than it is at the deeper end. In this manner the lengthwise linear stroke of the armature 34- is converted to a rotary stroke. The armature 34 of the magnetic actuator, as shown in the drawing, is constructed and arranged to move axially approximately while a rotational movement which may vary widely with specific requirements between 25 and 95 by way of example, is being imparted thereto by the cam recess and ball arrangement above described.

In accordance with the invention the rotary movement of the armature 34 above described is converted into an axially directed linear movement by means of a motion conversion device which is comprised essentially of three parts as follows. An inner cylindrical hub 46 is mounted directly onthe solenoid output shaft 48 of the armature 34 by means of a transverse pin 49. This hub accordingly simultaneously moves to the right and rotates with the solenoid armature 34. On the outside of this hub are three symmetrically spaced helical grooves 50 cut at a desired angle. This inner hub 46 is surrounded by a sleeve- 52 through the walls of which are out three similar helical grooves 54 which align with the grooves 50 in the inner hub. In each pair of grooves is a steel ball 56. The helical grooves 50, 54 are so con structed and arranged as to provide a composite helix angle which may be varied at any point along the length of the respective grooves to control the amount of mechanical advantage, i.e., the conversion ratio during the stroke of the armature 34.

Attached to and forming an integral part of this inner sleeve 52 is an outer sleeve 58 with three more equally spaced grooves 60 cut longitudinally in the outside surface. These comprise guide races which are aligned with three corresponding races or slots 62 in an outer surrounding sleeve 64 which is stationary. Steel balls 66 located in each of the outer pairs of

grooves

66, 62 guide the inner sleeve so that it is free to move axially but is prevented from rotating. The rotation of the cam produced by energizing the solenoid causes the

intermediate sleeve assembly

52, 58 to move to the right, by a distance dependent upon the radius and angle of the helical grooves. To this motion produced by the rotation of the armature is added the direct linear component of its axial stroke.

It will be noted that the use of three equally spaced races both for the inner helical grooves and the outer longitudinal grooves provides an inherently balanced and stable configuration in which the loads are divided between each of the three races comprising the force transmitting and guiding system respectively.

While the longitudinal groove and ball construction illustrated for guiding the

intermediate sleeve assembly

52, 58 in the longitudinal direction is preferred, it will be understood that other means to this end may be employed, as for example, the elastic hinge particularly illustrated in Figs. 6 and 7. Such an elastic hinge is provided by means of a steel washer 67 cut through at one point on its circumference and having a metal thickness small as compared with its radial width. With one end of the cut washer fixedly mounted at 68 and the other end attached to the

sleeve assembly

52, 58, at 69 the sleeve assembly is confined to an axial movement limited only by the practical limits of axial deformation of the washer below the yield point. In this form of the motion conversion unit the outer fixed sleeve 64, the

grooves

60, 62 and steel balls 66 have been replaced by the steel washer 67 The axial thrust of the

intermediate sleeve assembly

52, 58 induced by the energizing of the magnetic actuator operates to effect a corresponding shift of the valve spool 12 by means of the following connections: Nested within the hub member 46 is a cup 70 having the lip portion thereof formed as a flange which overlies the end of the inner hub sleeve 46 and is attached to the end of the

intermediate sleeve assembly

52, 58. The cup 75 provides support for a plunger 72 which is spring pressed to a fully extended position by means of a coiled compression spring 74 seated at one end against the base of the cup 70 and at its other end against the base of a recess within the plunger 72. The plunger is arranged to engage against an adjacent end of the valve spool 12. Outward movement of the plunger from the cup is limited by suitable retaining means, as by staking of the surrounding cup 70 so that the upset surfaces 75 thus formed will engage in the milled slots 77 shown cut in the periphery of the plunger 72. The spring 74 is for the purpose of biasing the cup 70,

sleeve assembly

52, 58 and associated parts axially to the left and causes the hub sleeve 46 and armature 34 to be rotated to the fully retracted inoperative position of Figs. 1 and 4.

By way of example it is assumed that the spool 12 of the illustrated valve assembly is adapted for an overall movement of about /8", that is 7 in either direction from the intermediate neutral pos1tion of Fig. 1.

The

intermediate sleeve assembly

52, 58 is given a motion in the order of which is controlled by the contour of the cam grooves 50, 54. The magnetic actuator and motion conversion device generally indicated at 28 associated with the right hand end of the valve body 10 are similarly constructed.

An important characteristic of the low direct current input magnetic actuator described consists in the more nearly constant torque developed throughout the solenoid stroke, as compared with the variable force vs. stroke characteristic of the conventional direct current or alternating current solenoids. This, in combination with the ability to vary the helix angle of the motion conversion device, provides the means for obtaining a desired force vs. stroke characteristic. For the most effective operation of the spool valve illustrated, it may be desired to provide a low helix angle in the mid position region in which the lost motion of the plunger 72 is taken up, and the actuating force of the solenoid is applied to the spool or, in this same type of valve it may be desired to provide an additional impact force to move the spool by adopting a conversion cam characteristic which will develop a pronounced hammer blow against the valving element which is separated from the output element of the motion conversion device for a fully retracted position thereof. In this instance a relatively large helix angle is employed at the beginning of the stroke which is thereafter decreased to a smaller angle so that a triggering action is provided which requires the solenoid resultant force to build up to a predetermined value before the initial motion starts. Once motion begins the force is increased rapidly by the reduction in the helix angle so that the armature is caused to accelerate rapidly and to attain a considerable velocity at its point of contact with the part to be moved. The grooves 50, 54 are contoured to provide a low composite helix angle at any precise point in the movement of the valving element at which a relatively heavy force is required.

A brief statement of the operation of the motion conversion unit shown follows: In the event that the valve spool 12 is in the intermediate or neutral position, as shown in Fig. 1, the energizing of either magnetic actuator as, for example, the magnetic actuator 30 will cause the

sleeve assembly

52, 58 of the motion conversion device to be advanced with increasing rapidity; first, to compress the spring 74 and thereafter, as the plunger 72 becomes seated within the cup 70, through this plunger to contact the spool 12 thus starting its motion. The impact of the moving

sleeve assembly

52, 58 and associated parts may be sufiicient to overcome any tendency of the valve spool to stick in the intermediate neutral position, or if necessary, a low helix angle of the grooves 50, 54 may be employed to increase the force applied at this oint.

p In the event that it is desired to return the valve spool to its intermediate neutral position, both of the magnet actuators are de-energized, permitting the valve spool 12 to return to its intermediate rest position under the influence of the centering springs 14, 20. Whenever both solenoids are de-energized and the spool 12 is accordingly in the mid-position, each solenoid is returned to its respective retracted position by the action of its individual return spring. In such manner the compression spring 74, acting against the cup 70 moves the

sleeve assembly

52, 58 to the left rotating the sleeve hub 46 and armature 34 to the initial rest position of Figs. 1 and 4.

While the motion conversion device of the present invention is here shown as applied to a two solenoid spring centered spool valve, it will be understood that the device is equally applicable for actuating other types of valves including two position single solenoid spring return and two position double solenoid, detent held, valves, and is also equally applicable to those classes of valves in which the axially movable valving element is known as a poppet, plug, slide, needle, cone or the like.

The invention having been described what is claimed is:

l. A magnetic actuator which comprises in combination a supporting structure, a rotary armature and magnet assembly comprising a magnet supported by said structure, an armature supported by said structure for longitudinal movement along a predetermined axis under the influence of said magnet and for rotary movement on said axis, and cam and follower means for effecting a rotary movement of the armature simultaneously with said longitudinal movement, said rotary armature and magnet assembly having a substantially uniform force versus rotational travel characteristic, and a motion conversion device comprising at least two superimposed cylindrical bodies in axial alignment with said armature, means connecting one of said cylindrical bodies to be moved by said armature, and means mounted in said structure confining the other of said cylindrical bodies for movement only along said axis, registering grooves in the adjacent faces of said cylindrical bodies, and ball means engaging simultaneously in each of said grooves, said grooves being angled with relation to one another 6 along the length of said grooves in accordance with a force versus axial movement characteristic to provide a predetermined over-all force versus point in axial stroke characteristic of said magnetic actuator.

2. A magnetic actuator according to claim 1 in which the means mounted in said structure confining said other of said cylindrical bodies for movement only along the axis of the armature comprises a longitudinal groove in a fixed portion of said structure, a longitudinal groove in said other cylindrical body registering with the groove in said structure, and ball means engaging simultaneously in said registering grooves.

3. A magnetic actuator according to claim 1 in' which said means mounted in said structure confining said other of said cylindrical bodies for movement only along the axis of the armature comprises an elastic hinge in the form of a flat coil spring member secured at one end to said structure and at its other end to said other cylindrical body.

4. A magnetic actuator which comprises, in combination, a supporting structure, a rotary armature and magnet assembly including a magnet, and an armature supported by said structure for longitundinal movement along a predetermined axis under the influence of said magnet and for rotary movement on said axis, and cam and follower means acting on said armature for effecting a rotary movement of the armature simultaneously with said longitundinal movement in accordance with a predetermined force versus rotational travel characteristic, and a member disposed with relation to said mag netic actuator to be shifted thereby along an axis, and a motion conversion device interposed between said armature and axially shiftable member comprising at least three superimposed telescoping sleeves in axial alignment with said armature including an outer sleeve fixedly supported with relation to said structure, an intermediate sleeve adapted for axial movement for moving said shiftable member, and an inner sleeve secured to said armature for axial and rotational movement therewith, registering grooves in the adjacent faces of the outer and intermediate sleeves, and connecting ball means engaging simultaneously with said registering grooves confining said intermediate sleeve to an axial movement only with relation to said structure, and registering grooves in the adjacent faces of said inner and intermediate sleeves, and connecting ball means engaging simultaneously in said registering grooves, said registering grooves being contoured with relation to one another along the length of said grooves in accordance with a force versus axial movement characteristic so that said longitudinal and rotary movements of the armature and attached inner sleeve will effect an axial movement of said intermediate sleeve in accordance with a predetermined over-all force versus point in axial stroke characteristic of said mag netic actuator.

5. For use in a device comprising a magnetic actuator having a structure including a magnet, and an armature supported by said structure for longitudinal movement along a predetermined axis under the influence of said magnet, and for rotary movement while moving axially on said axis, and a member disposed in axial alignment with said armature to be axially shifted thereby, the combination of a motion conversion device interposed between said armature and axially shiftable member in axial alignment therewith comprising at least two superimposed cylindrical bodies, one of said cylindrical .bodies being attached to said armature and the other of said cylindrical bodies being connected to move said shiftable member, longitudinally extending registering grooves in one face of said latter cylindrical body and in said structure and ball means engaging simultaneously with said longitudinally extending registering grooves thereby confining said latter sleeve to an axial movement only with relation to said structure, and registering grooves in the adjacent faces of said cylindrical bodies and ball means engaging simultaneously in each of said grooves, said grooves being angled with relation to one another along the length of said grooves in accordance with said pattern so that longitudinal and rotary movements ofthe armature and attached cylindrical body will effect an axial movement of the cylindrical body having a force versus point in axial stroke characteristic determined by said pattern.

6. A solenoid actuated fluid valve assembly which comprises, in combination, a magnetic actuator having a structure including a magnet, and an armature supported by said structure for longitudinal movement along a predetermined axis under the influence of said magnet and for rotary movement while moving axially on said axis, a fluid valve including a valving element disposed 'with relation to said magnetic actuator to be shifted along an axis thereby, and a motion conversion device interposed between said armature and valving element comprising at least three superimposed telescoping sleeves in axial alignment with said armature including an outer sleeve fixedly supported with relation to said structure, an intermediate sleeve adapted for axial movement for moving said valving element, and an inner sleeve secured to said armature for axial and rotational movement therewith, longitudinal registering grooves in the adjacent faces of the outer and intermediate sleeves, and connecting balls engaging simultaneously with said longitudinal registering grooves to confine said intermediate sleeve to an axial movement with relation to said structure, and registering grooves in the adjacent faces of said inner and intermediate sleeves, and connecting ball means engaging simultaneously in said latter registering grooves, said latter registering grooves being contoured with relation to one another along the length of said grooves in accordance with a force versus axial movement characteristic so that said longitudinal and rotary movements of said armature and attached inner sleeve will effect an axial movement of the intermediate sleeve in accordance with a predetermined overall force versus point in axil stroke characteristic of said magnetic actuator.

'7. In a device comprising a structure, and an actuator supported by the structure having a substantial component of rotary movement on an axis, and an actuated member disposed in axial alignment with said actuator to be shifted longitudinally thereby along said axis, the combination of a motion conversion device interposed between said actuator and said member comprising at least three superimposed telescoping sleeves in axial alignment with said actuator, including an outer sleeve fixedly supported with relation to said structure, an intermediate sleeve adapted for axial movement for moving said member, and an inner sleeve secured to said armature having a component of rotational movementtherewith, longitudinally extending registering grooves in the adjacent faces of the outer and intermediate sleeves, and connecting ball means engaging simultaneously with said registering grooves confining said intermediate sleeve to an axial movement only with relation to said structure, and a plurality of sets of registering grooves in adjacent faces of said intermediate and inner sleeves at spaced intervals about the periphery thereof. and connecting ball means engaging simultaneously in said registering grooves, said registering grooves being contoured with relation to one another along the length of said grooves in accordance with a pattern so that said rotational component of movement of said actuator and attached inner sleeve will effect an axial movement of said intermediate sleeve having a force versus point in axial stroke characteristic determined by said pattern.

References Cited in the file of this patent UNITED STATES PATENTS 1,765,377 Marks June 24, 1930 2,752,513 Boyd June 26, 1956 2,828,636 Hall Apr. 1, 1958