US2705064A

US2705064A - Electromagnetic fluid mixture clutch

Info

Publication number: US2705064A
Application number: US155468A
Authority: US
Inventors: William P Lear; Joseph M Boshka
Original assignee: Lear Inc
Current assignee: Lear Inc
Priority date: 1950-04-12
Filing date: 1950-04-12
Publication date: 1955-03-29
Anticipated expiration: 1972-03-29

Description

March 1955 w. P. LEAR ETAL ELECTROMAGNETIC FLUID MIXTURE CLUTCH Filed April 12, 1950 pwzwroast- Wllliam E? Lear 6; Joseph 77?. Bosh/(a BY W 0i United States Patent ELECTROMAGNETIC FLUID MIXTURE CLUTCH William P. Lear, Santa Monica, Calif., andJoseph M.

Boshka, Holland, Mich, assiguors to Lear, Incorporated, Grand Rapids, Mich, a corporation of Illinois Application April 12, 1950, Serial No. 155,468

7 Claims. (Cl. 192-215) So-called dry powdered iron electromagnetic clutches relay for their action upon the interposition between the driving and driven members of a mass of iron par ticles, e. g., terrum and carbonyl iron and the temporary unification of these members and the particles through the medium of magnetic flux. dition of the clutch the mass of particles lies idly in a cavity within the clutch, while upon energization of the clutch coil practically all of the particles are drawn into a desired orientation between the driven member, e. g.

a cup, and the pole pieces forming part of the driving 0 member. Thus the driving member, driven member and the mass of particles, bonded by the magnetic flux, revolve as a unit. Such clutches are characterized by high pullin and running torque, and, due to the absence of the large rubbing surfaces found in disc types of electromagnetic clutches, have long life. it is possible to provide very little clearance between the driving and driven members, hence a narrow gap and consequent high efficiency in the magnetic circuit.

By utilizing a cup rather than a disc for the driven member advantage may be taken of the greater torque available at the larger diameter, and this, together with the use of a narrow gap filled with the mass of iron particles makes for a highly efficient mechanism capable of operation on currents on the order of a fraction of an ampere. Accordingly a clutch of this kind is ideally adapted for use with servo-mechanisms driven from a push-pull amplifier of conventional design, e. g. automatic pilots for aircraft.

A principal object of the invention is to provide an improved form of electromagnetic clutch utilizing iron particles as the intermediary for engaging the clutch, and in which the actual zone of engagement is constituted by a relatively narrow annular body of iron particles coacting frictionally with similarly narrow pole pieces of the driving member and a correspondingly narrow region of the driven member, such zone lying at a maximum peripheral position.

Another object lies in providing non-magnetic barriers at each side of the engaging zone further to concentrate the available flux.

A further object lies in forming one or both of the pole pieces in a novel manner to present a narrowed area of magnetizable material at the actual engaging zone.

Still another object is to provide a cup-shaped driven member which cup is cut out in a novel manner to permit rapid distribution of the iron particles from idle condition to driving position upon energization of the clutch, and to reduce friction between the driving and driven members and the particles during idling of the clutch.

Generally regarded, the instant improvements in one aspect involve forming the pole pieces of the driving member in their relation to the cup-shaped driven memln the disengaged conher in such fashion that a highly concentrated flux field M 2,705,064 Patented Mar. 29, 1955 ice is formed, the iron particles then filling the gap between the driving and driven members to provide a flux path of extremely low reluctance. In another aspect the invention contemplates the provision of non-magnetic barnets on either side of the poles to minimize to a considerable degree the fringe flux. in still another aspect the invention includes a driven cup which has apertures for permitting rapid distribtution of the iron particles to the zone of engagement. In another respect the invention contemplates a novel composition of particulate magnetizable material and other ingredients in combination wtih the remaining elements of the clutch.

Referring to the drawing which depicts one form in which the invention may be embodied in practice:

Fig. l is a vertical medial cross section through the clutch of the invention;

Fig. 2 is a right hand end elevational view thereof, but with the brush structure omitted for clarity;

Fig. 3 is a half-cross-sectional view taken on the line 3-3 of Fig. 1; and

Fig. 4 is a cross-section taken on the line 4'4 of Fig. 3 showing the driving cup.

Turning to the drawing, the invention clutch comprises a driving member 10, a driven member 11 and a mass of magnetizable particles 12 for providing driving engagement when subjected to a magnetic field. Driving member 10 is constituted by an annulus 15 of paramagnetic material, e. g. Armco iron, an inexpensive composition having high magnetic permeability and good machining qualities. Secured to the right end face thereof is a disc 16 of Bakelite or equivalent insulating material having good mechanical strength, the junction being effected by dowel pins 17. Secured to both the anulus 15 and disc 16, by the same pins 17, is a ring gear 18 through which power is transmitted to the clutch by a pinion carried on the shaft of a motor (not shown). As will become evident the driving member 10 has a greater mass, by far, than the driven member 11, and it is therefore preferred that the part of greater mass be maintained in constant rotation to reduce inertia effects upon engagement. By providing a shoulder on the an nulus 15 and fitting a recess of the gear 18 snugly thereover adequate support is given the latter. Moreover by interposing a narrowed peripheral portion of the disc 16 between the gear and annulus the disc is properly carried and supported with respect thereto.

Grooves 21-21 in the outer face of disc 16 are fitted with slip rings 22-22 against which brushes 23-23 are adapted to bear, and by means of which current may be brought to the slip rings and thence to the clutch energizing coil to be described.

Supported by its right-hand end within the interior of the annulus 15 is the generally cylindrical clutch core 27 of the cross section shown. A recess 28 of generally trapezoidal cross-section carries the clutch energizing winding or coil 31 of pan-cake form. Conductors 33-33 are passed through a notch 34 and aperture 35 in the core 27, and connect the ends of the winding 31 with the rings 2222.

The flat left-hand face 24) of the core 27 and the lefthand wall of the recess 28 between them define a somewhat conical portion forming the inner pole piece 30, and whereby the flux emanating from the coil 31 is concentrated into a zone defined by the narrow peripheral face 37 of pole piece 30, such flux path being indicated by arrows.

To provide a barrier at one side for the magnetic flux a non-magnetic ring 41, e. g. brass, is brazed or otherwise united to the inner adjacent sloping face of the recess 28. Ring 41 is so dimensioned as to provide a tight fit against the inner surface 32 of the annulus 15, thus to support the core 27 at its inner end.

A reduced portion of the core 27 is fitted into an aperture 26 in the disc 16 to provide additional support for the latter. For cooling the clutch a plurality of fins 43 may be provided at the right-hand end of the core 27.

At its left end the annulus 15 is provided with an inwardly extending flange 46, the inner axially extending cylindrical face whereof, constituting the other pole piece, is substantially coextensive with. the face 37 of the pole piece 30. Acting as a magnetic barrier on the left-hand surface of the pole piece 46 is a second non-magnetic ring 48 brazed or otherwise united with the annulus 15. Thus the flux across the pole pieces 30 and 46 is substantially confined to the relatively narrow cylindrical faces thereof, and fringe flux accordingly reduced to a negligible minimum.

An end housing 51 is tightly fitted over the ring 48, and is secured in any convenient manner to the annulus 15, thereby to enclose the inner parts of the clutch and to define a cavity 52 for the clutch driven member and the particulate composition to be described. Housing 51 may be provided with circumferential fins 49 to facilitate cooling.

Rotatably supported in

ball bearings

53 and 54 mounted in the housing 51 and core 27 respectively is a shaft 55, and keyed thereto is the cup-shaped driven member 57 comprising a disc portion 58 of non-magnetic material, e. g. brass, to which is brazed a paramagnetic ring 59. This latter is so proportioned as to lie in the gap defined by the pole pieces 30 and 46.

Deposited in the cavity 52 is a mass of paramagnetic material, preferably comprised as follows:

By weight- 75% ferrum 25% carbonyl E iron to which is added by weight:

2% lubricating graphite /2 of 1% boron nitride and ball milled for 72 hours with /1 steel balls to insure complete homogeneity. After being milled and until used the composition is stored in a dry place. A sufficient quantity of this composition is added to the clutch to fill completely the spaces intermediate the driving and driven clutch members. In the drawing such mass of material is indicated by stippling. It has been found advisable to run-in the clutch for a period of time, which has been found to cause a reduction in the original mass of powder, i. e. packing. Accordingly additional powder may be added to fill again the indicated spaces. Notwithstanding even further minor packing during the life of the clutch the efliciency is not reduced, since there will be an ample supply of powder to insure that the expected magnetic driving connection Will be achieved.

It will be noted from the drawing that the peripheral portion 40 of the driven member 57 is of such cross section as to position the same as nearly as possible to the magnetic gap defined by the poles 30 and 46, and hence to provide a non-magnetic barrier radially inwardly and as a companion to the barrier ring 48. However a sufiicient throat 50 must be provided to permit proper distribution of the powder 12.

In order to reduce rubbing friction between the driven member and the powder, it is preferred to provide the disc portion 58 of the driven member with apertures 61 of as large a size as possible consistant with mechanical strength of the driven member, thereby to reduce the superficial area of the member and therewith the undesirable friction; and to notch or cut-out the flange 59 thereof for the same purpose. Furthermore such foraminous configuration of the driven member provides a passage from one face to the other thereof, thereby permitting rapid distribution of the magnetizable powder in the space beween the pole pieces, and its rapid dissemination therefrom.

While it is believed that the operation of the clutch is more or less apparent from the preceding description, it will be understood that the clutch driving member, being constantly rotating, will have its winding 31 supplied with energizing current via the brushes 23-43 and slip rings 2222. Accordingly a flow of energizing current will create a concentrated magnetic field across the pole pieces 30 and 46. Thereupon a quantity of the powder in greater concentration than the deenergized status will be found in the gaps intermediate the pole pieces and the flange 59 to lock the driving and driven members together for joint rotation.

In effect the particles have been found to act more like a solid than a comminuted mass thereby to provide virtually a non-slipping transmission of torque in the fully energized condition.

While we have shown a particular embodiment of our invention, it will be understood, of course, that we do not wish to be limited thereto, since many modifications may be made, and we therefore contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of our invention.

Having thus described our invention, what we claim and desire to secure by Letters Patent is:

1. An electromagnetic clutch comprising a rotatable driving member including a pair of annular poles so disposed as to define an annular gap, electrical means carried by said member for providing magnetic flux in said gap upon energization of the clutch, a rotatable driven member including a paramagnetic annular part positionedin said gap and defining an outer annular gap and an inner annular gap, a casing carried by said driving member for enclosing said gap and driven member, a mass of pulverulent paramagnetic material disposed in said casing the bulk of which material is adapted upon energization of the clutch to take up a position in said gaps for uniting said part and driving member for joint rotation, a non-magnetic annular element united with said driving member and positioned on one side of said outer gap, a second non-magnetic annular element united with said driving member and positioned on the opposite side of said outer gap and bridging across both said gaps, and a non-magnetic annular element united with said driven member and positioned adjacent said inner gap on the same side thereof as said driven member.

2. An electromagnetic clutch comprising a rotatable driving memberincluding a pair of annular poles so disposed as to define an annular gap, electrical means carried by said member for providing magnetic flux in said gap upon energization of the clutch, a rotatable driven member including a paramagnetic annular part positioned in said gap, a casing carried by said driving member for enclosing said gap and driven member, a mass of pulverulent paramagnetic material disposed in said casing the bulk of which material is adapted upon energization of the clutch to take up a position in the spaces defined by said annular part and gap for uniting said part and driving member for joint rotation, a non-magnetic annular element united with said driving member and positioned adjacent said gap at that side thereof opposite said driven member, said non-magnetic element being bridged across said gap, and a second non-magnetic annular element united with said driven member and positioned on the same side of said gap as said driven member.

3. An electromagnetic clutch comprising a rotatable driving member including a pair of annular poles so disposed as to define an annular gap, electrical means carried by said member for providing magnetic flux in said gap upon energization of the clutch, a rotatable driven member including a paramagnetic annular part positioned in said gap, a casing carried by said driving member for enclosing said gap and driven member, a mass of pulverulent paramagnetic material disposed in said casing the bulk of which material is adapted upon energization of the clutch to take up a position in the spaces defined by said annular part and gap for uniting said part and driving member for joint rotation, a nonmagnetic annular element united with said driving member and positioned adjacent said gap at that side thereof opposite said driven member, and a second non-magnetic annular element united with said driving member and positioned on the same side of said gap as said driven member.

4. An electromagnetic clutch comprising a rotatable driving member including a pair of annular poles so disposed as to define an annular space therebetween, the end faces of the poles being substantially coplanar, a rotatable driven member including an output shaft, a web portion extending radially from said shaft and a magnetic flange portion disposedrin said space to define with said poles an inner annular gap and an outer annular gap, electrical means carried by said driving member for providing magnetic flux in said gaps, a casing carried by said driving member and surrounding said poles and driven member, a mass of pulverulent magnetic material contained in said casing, a part of said material being adapted, upon energization of said electrical means, to take up a position in said gaps to couple said driving and driven members for joint rotation, a first non-magnetic ring united with the outer pole at the end face substantially thereof and having a face coplanar with the inner axially-disposed face of said outer pole, a second non-magnetic ring united with both said poles and bridging said gaps and the end face of said flange portion, and a third non-magnetic ring united with said flange portion and positioned closely adjacent the outer end of the inner gap but sufficiently far to permit unimpeded circulation of the pulverulent material into and out of said inner gap upon energlzation and deenergization of said electrical means.

5. An electromagnetic clutch comprising a driving member of paramagnetic material, said member having an internal space, an energizing winding mounted in said space, slip ring and brush means operatively associated with said member for connecting said winding to an ex ternal current source, said member comprising a substan tially cylindrical inner part and an annular outer part, said inner part having a radially outwardly extending pole piece including a face disposed substantially axially of said member, said outer part having a radially inwardly extending pole piece including a face disposed substantially parallel to said first face and defining therewith a magnetic gap, a driven member having a paramagnetic part positioned in said gap to define with said faces a pair of annular spaces, a casing carried by said driving member and enclosing said driven member, and a mass of pulverulent paramagnetic material disposed in said casing the bulk of which material is adapted, upon energization of the clutch, to be positioned in said spaces to unite said driving and driven members for joint rotation, a nonmagnetic element in contact with said pole pieces on that side thereof opposite said driven member and bridging said gap, to confine said material to said spaces, and a second non-magnetic annular element juxtaposed to the outer face of said inwardly extending pole piece and continuing to said gap.

6. An electromagnetic clutch comprising a driving member of paramagnetic material, said member having an internal space, an energizing winding mounted in said space, slip ring and brush means operatively associated with said member for connecting said winding to an external current source, said member comprising a substantially cylindrical inner part and an annular outer part, said inner part having a radially outwardly extending pole piece including a face disposed substantially axially of said member, said outer part having a radially inwardly extending pole piece including a face disposed substantially parallel to said first face and defining therewith a magnetic gap, a driven member having a paramagnetic part positioned in said gap to define with said faces a pair of annular spaces, a casing carried by said driving member and enclosing said driven member, and a mass of pulverulent paramagnetic material disposed in said casing the bulk of which material is adapted, upon energization of the clutch, to be positioned in said spaces to unite said driving and driven members for joint rotation,

a non-magnetic element in contact with said pole pieces on that side thereof opposite said driven member and bridging said gap, to confine said material to said spaces, and said driven member being provided witha non-magnetic annular part disposed contiguous to said gap.

7. An electromagnetic clutch comprising a driving member of paramagnetic material, said member having an internal space, an energizing winding mounted in said space, slip ring and brush means operatively associated with said member for connecting said winding to an external current source, said member comprising a substantially cylindrical inner part and an annular outer part, said inner part having a radially outwardly extending pole piece including a face disposed substantially axially of said member, said outer part having a radially inwardly extending pole piece including a face disposed substantially parallel to said first face and defining therewith a magnetic gap, a driven member having a paramagnetic part positioned in said gap to define with said faces a pair of annular spaces, a casing carried by said driving memher and enclosing said driven member, and a mass of pulverulent paramagnetic material disposed in said casing the bulk of which material is adapted, upon energization of the clutch, to be positioned in said spaces to unite said driving and driven members for joint rotation, a nonmagnetic element in contact with said pole pieces on that side thereof opposite said driven member and bridging said gap, to confine said material to said spaces, a second non-rnagnetic annular element juxtaposed to the outer face of said inwardly extending pole piece, and said driven member being provided with a non-magnetic part both said element and part being disposed contiguous to said gap.

References Cited in the file of this patent UNITED STATES PATENTS 2,315,298 Thompson Mar. 30, 1943 2,488,079 DeLavaud et al Nov. 15, 1949 2,488,827 Pensabene Nov. 22, 1949 2,519,449 Findley Aug. 22, 1950 2,525,571 Winther Oct. 10, 1950 2,573,065 Salemme Oct. 30, 1951 2,575,360 Rabinow Nov. 20, 1951 OTHER REFERENCES Magnetic Fluid Clutch in Servo Applications, Electronics, November 1949, pages -103.

The Magnetic Fluid Clutch, AIEE Transactions, vol. 67, printed December 13, 1948.

Contributed Original Research, Journal of Applied Physics, vol. 20, December 1949, pages 1137-1140.

Claims

1. AN ELECTROMAGNETIC CLUTCH COMPRISING A ROTATABLE DRIVING MEMBER INCLUDING A PAIR OF ANNULAR POLES SO DISPOSED AS TO DEFINE AN ANNULAR GAP, ELECTRICAL MEANS CARRIED BY SAID MEMBER FOR PROVIDING MAGNETIC FLUX IN SAID GAP UPON ENERGIZATION OF THE CLUTCH, A ROTATABLE DRIVEN MEMBER INCLUDING A PARAMAGNETIC ANNULAR PART POSITIONED IN SAID GAP AND DEFINING AN OUTER ANNULAR GAP AND AN INNER GAP, A CASING CARRIED BY SAID DRIVING MEMBER FOR ENCLOSING SAID GAP AND DRIVEN MEMBER, A MASS OF PULVERULENT PARAMAGNETIC MATERIAL DISPOSED IN SAID CASING THE BULK OF WHICH MATERIAL IS ADAPTED UPON ENGERGIZATION OF THE CLUTCH TO TAKE UP A POSITION IN SAID GAPS FOR UNITING SAID PART AND DRIVING MEMBER FOR JOINT ROTATION, A NON-MAGNETIC ANNULAR ELEMENT UNITED WITH SAID DRIVING MEMBER AND POSITIONED ON ONE SIDE OF SAID OUTER GAP, A SECOND NON-MAGNETIC ANNULAR ELEMENT UNITED WITH SAID DRIVING MEMBER AND POSITIONED ON THE OPPOSITE SIDE OF SAID OUTER GAP AND BRIDGING ACROSS BOTH SAID GAPS, AND A NON-MAGNETIC ANNULAR ELEMENT UNITED WITH SAID DRIVEN MEMBER A POSITIONED ADJACENT SAID INNER GAP ON THE SAME SIDE THEREOF AS SAID DRIVEN MEMBER.