US2157324A - Adjustable magnetic apparatus - Google Patents

Description

May 9, 1939- P. D. CROUT 2,157,324

ADJUSTABLE MAGNETIC APPARATUS Filed Oct. 26, 1954 2 Sheets-Sheet l FIG. I

INVENTOR PRESCOTT D. CROUT ATTORNEY May 9, 1939. P. D. GROUT 2,157,324

ADJUSTABLE MAGNETIC APPARATUS PRESCOTT D. BY Mm ATTORNEY Patented May. 9, 1939 UNITED STATES PATENT OFFICE ADJUSTABLE MAGNETIC APPARATUS Prescott D. Crout, Boston, Mass., assignor to Raytheon Manufacturing Company, Newton, Mass, a corporation of Delaware Application ctober 26, 1934, Serial No. 150,117 '7 Claims. (01. 111-119) This invention relates to an adjustable magnetic apparatus, and more particularly to such an apparatus in which the inductance thereof may be varied.

An object of this invention is to provide such an apparatus in which the current through said inductance is varied directly in accordance with the magnitude of motion of a controlling member. Another object of, the inventionis to devise a novel supporting structure for the movable magnetic member of such an apparatus. I

,' A still further object is to .provide a device of the kind indicated, which is simple and sturdy Fig. 2 is a top view of the apparatus shown in Fig. l with certain portions broken away;

I Fig. 3 is a cross-section of the upper portion of the structure taken along line 3-3 of Fig. 2; and

of the movable magnetic bar.

In my co-pending application, Serial No.

a 742,913, I have described and claimed a combined transformer and inductance control unit which is to be used in a welding machine. The present apparatus constitutes an improved form of the combined transformer and inductance control unit shown in said co-pending' application.

In any adjustable magnetic apparatus in which the inductance is varied by varying an air gap, it is difficult to obtain a linear change of 4 susceptance in accordance withthe magnitude of movement of the controlling member of the system. This is probably due to the fact that produce comparatively large changes in the susceptance, while with a longer air gap, a smaller" change in the length thereof will produce a much smaller change in susceptance. In my present invention I have eliminated this difficulty by moving a magnetic bar so as to produce a variable air gap by means of a controlling member in such a way as to produce a relatively small change in the air gapjper unit distance of motion ofsaid controlling member when said air gap is small, and an'increasingly'sr'eater' change in the air gap per unit distance of motion of said controlling member as the length of the airgap increases. I I I Fig. 4 is a side view of one of the laminations In thedrawings the combined transformer and inductance control unit consists of a transformer l and a variable inductance 2. The various coils of the transformer i and the inductance 2 are preferably mounted on a combined core member 3 having three legs 4, 5 and 6 upon which the transformer coils are wound, and three additional legs 1, 8 and 9 upon which the three inductance I coils i0, II and i2, respectively, are wound. The combined core member 3 has yokes l3 and ll completing the magnetic path for the transformer, the yoke l4 forming.

also part of the magnetic path for the inductance coils Ill, ll and I2. I, 8 and Bare formed with substantially flat pole faces and a movable magnetic bar I5 is disposed adjacent the outer ends of said pole faces. The

magnetic core 3 and its associated coils are mounted within a frame it. This frame--'-has formed thereon a number: of arms I'i; whereby the entire unit may be bolted in place into such The upper ends of the legs a welding machine as shown in my co-pending application referred to above. The said core may be bolted in place on said frame it by means of a plurality of bolts 18. The coils III, II and I2 are easily assembled on the legs I, 8 and 3 by being slipped over-the outer ends of these legs, and are retained in place by a plate i9 which may be formedof some suitable material, such as an insulating board. I The plate I9 is retained in place on the legs], 8 and 9 by means of bars clamped on opposite sides .of each leg I, 8 and 3 by means of bolts 2i.

Although I have described the above ratus as consisting of both s. transformer and an inductance unit, this invention is concerned primarily with the inductance unit itself. Thus this inductance unit could be an entirely separate member having a diflerent number .of legs and pole faces than thatidescribed above, and likewise such inductance element may be useful in a cast number of instances aside from use'in an arc welding machine. I

In order that the inductance of the element 2 be variable, the magnetic bar I! is movable with respect to the pole faces of the legs 1,3 and 9 in such a manner as to produce a variable air gap adjacent each of said pole faces. In order to support said magnetic bar i 5, a frame 22- is bolted to the frame l6 at the upper end thereof by means of a plurality of bolts 23. The frame 22 is provided with four cams 24, which cams form the supporting and guidingmembers for the magnetic bar it. The magnetic bar l5 itself consists of a plurality of magnetic laminations '26 mounted within a sub-frame 25. One of these laminations 26 is shown in Fig. 4. As will be seen, the lamination is entirely imperforate and is provided with two projecting ears 21. In order to assemble the laminations within the subappa-,

frame 25, these laminations are merely Slipped into said frame 25 with the ears 2'! resting on the two ends of said sub-frame. In order that these laminations be tightly packed, a wedge 26 which may be made of some suitable material, such as brass, may be inserted between the side of subframe 25 and the laminations 26. Since the subframe 25 consists merely of a hollow rectangular member, the sides thereof possess considerable flexibility. In order that the laminations be still more firmly clamped within said sub-frame, said sub-frame is provided with upstanding ears 29 through which passes a bolt 30. By clamping the bolt 30 onto said ears 29,-the sides of the sub-frame 25 may be bowed in sumciently to insure a firm clamping action on the sides of the laminations 26. It will beseen that these laminations are not provided with perforations for the-purpose of v bolting them into place on the sub frame. This results in an extremely simple form of lamination which is easily constructed and easily assembled. Due to the fact that the major force exerted on the laminations tends to move them in toward the pole faces of the legs I, 8 and 9' and since the ears 21 on the laminations 26 oppose such motion, the resultant action one which retains the laminations firmly in place in the desired position with respect to the sub-frame 25.

In'order to support the magnetic bar I5 on the cams 24, the sub-frame 25 has formed integrally therewith the four sleeves 33 at the four corners thereof. Two shafts 34 are passed through the two end pairs of sleeves 33, and are retained in placetherein and prevented from turning by some suitable means, such as pins 35. The shafts 34 project beyond the outer ends hooked over projections 38 formed at the two and undesirable vibration of'themagnetic bar' I5 with respect to the rest of the structure. This action is more fully described and claimed in my said copending application. In order that this function shall occur, the tension springs 31 are designed to exert sufiicient pull on the magnetic bar I5 so that no chattering occurs between-the bar I5 and its associated structure.

It is difficult to support a rigid bar'" at four movable points inasmuch as each of said points should be in intimate contact with its respective supporting surface so that excessive backlash and play is avoided and thus undesirable vibration and impact eliminated. In my device this difllculty has been avoided, and the four rollers 36 are'always maintained in intimate contact I with the four cams 24. Due to the fact that the sub-frame 25 is a simple rectangular member and the laminations 26 are merely inserted into said sub-frame, theresultant structure has a considerable amount of torsional flexibility. Thus even if the cams 24 are not accurately aligned, the sub-frame 25 will, under the action line.

of springs 3'I,twist so that each roller 36 is In intimate contact with its respective cam 24. The absence of any fastening member passing through the laminations 26 permits them to slide by each other to some degree, and thus the magnetic bar I5 participates accurately in the twisting of the sub-frame 25. In constructing the device, nospecial precautions'need be taken to align the cams 24 or the rollers 36 accurately. When assembled the bar I5 will always be firmly supported at "the four corners. The flexibility of the bar I5 and sub-frame 25 offers no disadvantage since when it is seated upon the cam 24 the rigidity of the frame 22 gives to the entire assembly the requisite stiffness.

In order further that the rollers 36 bear equally on the four cams 24, it is desirable for the force pulling the bar |5 toward the pole faces of the legs I, 8 and 9 to act through the center of said bar. Thus the projections 38 are located on the center line of bar I5, and the springs 31 exert their force along's'aid center The magnetic forceacting' on the movable magnetic bar I5 also'ls exerted in such a way that the resultant force may be considered'as acting through the center of said magnetic bar. It is ordinarily very diflic'ult to dispose the movable magnetic bar so that this result is obtained. In my device I have eliminated this difliculty by arranging the laminations 26 so that the central line 3| of'the magnetic bar I5 is at all times nearer the pole faces of the legs I, 8 and 9 than the rest of said magnetic bar on either side of said central line. This is accomplished by shaping the two ends of the sub-frame 25 so that the upper sides 32 thereof are shaped as indicated a by the dotted line .in Fig. 3. Thus merely by inserting identical laminations 26 into the subframe 25, the resultant magnetic bar takes the shape as shown in Fig. 3. Since the center of the magnetic bar I5 is thus disposed so that it is nearest to thepole faces of the legs I, 8 and 9, the resultant magnetic force exerted on said magnetic bar is accurately centered on said bar.

In order to produce the desired adjustment and motion of the bar I5, a suitable controlling arrangement is .provided therefor. Rotatably 'mounted on the bolt 30 is one end of a link 40.

The other end of said link is rotatably connected to one end ofa rod 4|. The rod 4| is free to slide through a sleeve 42 carried by a cross-bar 43 'mountedon the upper side of the frame 22. Although the rod 4| is free to slide in said sleeve 42, it cannot turn therein. This is due to the fact that the link 40 connected to the end of rod 4| .cannot turn, and thus prevents rod 4| from turning. The opposite endof the rod 4| projects through said sleeve 42, and is threaded through asu'bstantial length as indicated at 44. An actuating member -45 is provided with internal threads which engage the, external threads 44 on the rod 4|. The outer end of the threaded portion 44 ofthe rod is provided with a stop member 46 whichis fastenedin place on said rod 4| after the member 45 has been threaded,

into place. In addition to the springs 31, asmall biasing spring 41 15 provided which tends to move the reactor bar I5 to the left, as shown in Fig. 1, and likewise tends to move the link 40 and rod 4| in this same direction. Due to this biasing action, the actuating member 45 is biased so that it firmly engages the outer end of the sleeve 42. .In order to rotate the actuating member 45, itis provided-with a sprocket 46 which is engaged by a chain 49. Any suitable mechanism for moving the chain 48 may be used.

Preferably the actuating mechanism may consist of the arrangement as shown in my said co-pending application. It will be seen that as the adlusting member 45 is rotated, the rod; 4i will-be moved to the left or right as shown in Fig. 1. As

. the rod 4i moves to the right, the magnetic bar ll as pointed out above. This action causes the air gap at the outer ends of the 'pole faces on legs 1, 8 and 9 to decrease, and thus increases the inductance of the coils ll, Ii and I2. As the rod 4i moves to the left, and magnetic bar I! likewise is moved to the left, the rollers 36 are caused to ride up on the cams 24, thus increasing the air gap and decreasing the inductance of the coils Ni, ii and i2.

As will be seen from Fig. 1, the cams 24 are so formed that as the rod 4| moves to the left a definite distance when the magnetic bar i5 is in its lower position, a relatively small change in the relative position between the magnetic bar and its associated pole faces occurs. Thus a relatively small change in the length of the air gap is produced. Toward the upperposition of the bar l5, however, if the rod 4! is moved to the left the same distance, a much greater change in the air gap is produced. Although the cams 24 can be designed so that the inductance of the coils Ill, ii and i2 varies in any desired relationship with respect to the movement of the actuating member 45, I prefer that these cams be formed in such a way that the susceptance of said coils changes substantially linearly with the angular distance through which the actuating member 45 is moved. Thus when the device is used in such an arc welding machine as described in my copending application, the current through the load will vary substantially linearly with the angular distance through which said actuating member is moved. I find that these conditions may be satisfied by circular cam surfaces.

It is to be understood that this invention is not limited to the particular details of the arrangement as described above'as many equivalents will suggest themselves to those skilled inthe art. For example, certain aspects of my invention may be' useful in any magnetic apparatus in which an adjustable air gap is-desired, even those in which but a single such air gap is provided. Various other changes and uses in and for the various novel parts of my invention will readily suggest themselves. It is accordingly desired that .the appended claims be given a broad interpretation commensurate with the scope of the invention within the art.

What is claimed is:

1. In a magnetic apparatus, a magnetic core, I

'said supporting surfaces, whereby said bar is always maintained firmly seated against said supporting surfaces.

2. In a magnetic apparatus, a magnetic core, means for setting up a magnetic flux in saidcore, said magnetic core having a variable air gap between a pole face and a movable magnetic bar, said movable magnetic bar comprising a hollow frame member and a number of laminations of magnetic material inserted in said frame member,-and abutments on said laminations engaging surfaces on said frame member and opposing motion of said laminations under action of said magnetic flux, whereby said laminations are retained in place in said frame member.

3. A magnetic bar comprising a hollow frame member and a number of laminations of magnetic material inserted in said frame member, and abutments on said laminations engaging surfaces on said frame member and opposing motion of said laminations under action of a magnetic flux, said frame member having side members and end members, said side members having sufficient flexibility to permit said laminations to be yieldably wedged into said frame member.

4. A magnetic bar comprising a hollow frame member and a number of laminations of magnetic material inserted in said frame member, abutments on said laminations engaging surfaces on said frame member and opposing motion of said laminations under action of a magnetic flux, said frame member having side members and 'end members, said side members having suflicient flexibility to permit said laminations to be yieldably wedged into said frame member, and means for clamping said side members against the sides of said laminations.

5. In a magnetic apparatus, a magnetic core, means for setting up a magnetic flux in said core, said magnetic core having a variable air gap between a pole face and a movable magnetic bar, the face of said magnetic bar facing said pole faces being disposed in more than one plane, the center line of said face being disposed closer to said pole faces than the rest of said face, whereby the center of the magnetic force exerted by said magnetic flux is centered on said magnetic bar.

6. In amagnetic apparatus," a magnetic core, means for setting up a magneticfiux in said core, said magnetic core having a variable air gap between a pole face and a movable magnetic bar, the face of said magnetic bar facing said pole faces being disposed in more than one plane, a

predetermined portion of said face being disposed closer to said pole faces .than the rest of said face, whereby the magnetic force exerted by said magnetic flux is centered on said predetermined portion.

'7. In a magnetic apparatus, a magnetic core, means for setting up a magnetic flux in said core, said magnetic core having a variable air gap between a pole face and movable magnetic bar, means for supporting said magnetic bar at a plurality of movable points on opposite sides of the center line of said magnetic bar, the'face of said magnetic bar facing said pole faces being disposed in more than one plane, the center line of said face being disposed closer to said pole faces than the rest of said face, whereby the center of the magnetic force exerted by said magnetic flux is centered on said magnetic bar, and the said force is substantially equally divided between the 1siupporting points on opposite sides of said center PRESCOTT D. GROUT.

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