US1180457A - Magnetic chuck. - Google Patents

Description

Eg Z

o. s. WALKER. MAGNETIC CHUCK. APPLICATION FILED FEB. I, I9I5.

Patented Apr. 25, 1916.

2 SHEETS-SHEET I.

` MKM/AM? 5%@ A' Mw 0. S. WALKER.

MAGNETIC CHUCK.

APPLICATION FILED FEB. I. I9l5.

1, 180,457. Patented Apr. 25, 1916.

2 SHEETS-SHEET 2.

UNITED STATES PATENT OFFICE.

OAKLEY l. WALKER, E WORCESTER, MASSACHUSETTS, AssIGNoR To o. s. WALKER Co., 0F WORCESTER, MASSACHUSETTS, A CORPORATION 0E MASSACHUSETTS.

MAGNETIC CHUCK.

Specification of Letters Patent.

Patented Apr. 25, 1916.

Application filed February 1, 1915. Serial No. 5,411.

To all whom t may concern:

Be it known that I, OAKLEY S.VWALKER, a citizen of the United States, residing at Worcester, in the County of Vorcester and Commonwealth of Massachusetts, have invented a new and useful Improvement in Magnetic Chucks, of which the following, together with the accompanyinf"l irawings, is a specification. f

The present invention relates to magnetic chucks, and has particular reference to an improved construction for a device of this class whereby the same aifords a work holding face which is peculiarly adapted for the retention of a large number of small pieces of iron or Steel placed thereon to be operated upon.

The said invention consists in the construction and arrangement of parts, set forth in the following description and illustrated in the accompanying drawings, in which- Figure 1 is a top plan view of a chuck embodying my invention. Fig. 2 is a vertical sectional view of said chuck, taken substantially in a diametrical plane. Fig. 3 is a plan view of the chuck shown in Fig. 1, the face plate thereof being removed to disclose the interior construction. Fig. 4 is a fragmentary vertical sectional view of a modified form of chuck.

Similar reference characters refer to similar parts in the different figures.

Referring to the drawings, the numeral 1 .denotes a circular base of magnetic metal,

providing a central aperture 2 for the attachment of a shaft or spindle, not shown,

` by which the chuck may be rotated. The

base l ai'ords an upwardly projecting central hub 3, and a concentric series of spaced annular flanges 4, 5, 6, 7 and 8, with their top surfaces flush with the top surface of said hub. The annular space 9 thus formed between hub 3 and iiange 4, and the concentric annular spaces 10, 11, 12 and 13 similarly formed between the flanges 4 and 5, 5 and 6, 6 and 7, and 7 and 8, respectively, receive the several circular magnetizing coils 14, 15, 16, 17 and 18 of the chuck, as shown in Figs. 2 and 3. These coils, in the present instance, are similarly wound and are connected in an electrical circuit in the manner hereinafter described.

One terminal of the innermost coil 14, in the present instance the inner terminal, has connected thereto a conductor 19 passing through a Slot 20v in the surrounding flange 4 and across the top of coil 15, as shown in Figs. 2 and 3. A Series of equidistant holes, leadmg upwardly through the flange 5 from an annular recess 21 on the under side of base l, are provided for the reception of bushings 22 of fiber or other insulating material which afford shouldered heads 23 seating against the inner wall of recess 21. The

flange 5 is counterbored from the top, asl

shown at 24, Figs. 2 and 3, providing shoulders disposed somewhat above the upper ends of the bushings 22, upon which shoul- .aers are seated washers 25 of fiber or other insulating material. Screws 26, with their heads within said counterbores and bearing against said washers, are extended through said bushings, their ends enteringan annular Contact ring 27, to draw the same into the recess 21 against the heads 23 of the bushings 22 as the screws are tightened. The spaces left between the washers 25 and the upper ends of the corresponding bushings 22 permit the several parts to be drawn into snug engagement, as will be clearly understood. The recess 21 is preferably filled with any suitable non-conducting substance, such as sulfur, poured therein in a molten State after the parts are assembled as above described, to hold them lirmly in position and to pre- Vent the access of dust, dirt and water thereto. The construction above described is also applied to the attachment of a second Contact ring 28, by screws 29 passing through the flange 6; since said attachment is effected in precisely the same manner as the attachment of ring 27, it is unnecessary to describe the same in detail.

The conductor 19 leading from the inner terminal of coil 14 is connected to one of the screws 26, as by insertion between a brass Washer and the head of said screw, as

` shown in Figs. 2 and 3, thereby being placed in electrical connection with the ring 27, which is adapted to rotate in contact with a stationary brush, not shown, included in the electrical circuit used to energize the chuck. The outer terminal of coil 14 is connected, by a conductor 30 passing through a slot 31 in the flange 4, Fig. 3, with the outer terminal of the next adjacent coil 15, and the inner terminal of coil 15 is connected, by a conductor 32, Fig. 3, passing through one of flange `5, with the The outer termithe counterbores 24 in inner terminal of coil 16.

nal of coil 16 is connected, bya conductor 33 passing through one of the counterbores 24 in flange G, with the outer terminal of coil 17, and the inner terminal of coil 17 is connected, by a conductor 34 passing through a slot 35 in the flange 7, with the inner terminal of coil 18. The outer terminal of coil 18 is connected, by a conductor 36 passing through a slot 37 in flange 7, with one of the screws 29 which secures the second ring 28 in place, thereby completing the electrical circuit through the coils of the chuck when both of said rings 27 and 28 are rotating in contact with their respective brushes, not shown.

As previously stated, the several coils are similarly wound, and it will be apparent from the above, are connected together in series. However, by reason of the above described connection of like terminals of adjacent coils, the magnetizing effect of the current passing therethrough is relatively opposite forvany two adjacent coils. This will be made apparent in the effect4 roduced upon the hub 3 and the several anges 4, 5, 6, 7 and 8, which constitute, in effect, cores for the several coils. Assuming that the passage of current through coil 14 renders the hub 3 of positive magnetic polarity,- and the flange 4 of negative polarity, as indicated by the -land signs on Fig. 2, it will be clear that the magnetizing effect of the current in coil 15, which is relatively opposite to that in coil 14, imparts negative polarity to the flange 4 and positive polarity to the next adjacent flange 5. The above alternation of polarity for the several remaining flanges is carried out by the above described connection of the coils, and said flanges, for convenience, have been design ated on Fig. 2 with alternating and signs. The work holding face ofthe chuck, which derives its magnetism through contact with the hub 3 and several flanges 4, 5, 6, 7 and 8 of the base 1, is constituted in part by a centrally disposed structure presenting an arrangement of radiating non-magnetic gaps between sections of opposite polarity, and in part by a concentric annular structure presenting a plurality of circular nonmagnetic gaps between its several sections. I have shown the central portion of said face as composed of a member 38, having a central aperture 39 coaxial with the hole 2 through the base and superposed at its central portion upon the hub 3, so as to partake of the magnetic polarity of said hub. Said member 38 provides a plurality of radiating spurs or teeth 40 which project outwardly over the top of the flange 4, being cut away on their under sides, as shown at 41, tofavoid contact with said flange. The flange 4 supports an annular skeleton plate 42, surrounding member 38 and having a plurality of inwardly projecting radial spurs 43 which enter the spaces between the teeth 40 of member 38 and are cut away, on their under sides, as shown at 44, to avoid contact with the hub 3. As will be clearly understood, the edges of the interlockinv teeth and spurs upon the member 38 anil4 plate 42, respectively, do not make contact, but present a continuous narrow gap extending between all opposing portions thereof. Said gap is filled with non-magnetic material, the same in the present instance being preferably a brazed continuous joint between the two' parts, as indicated by the heavy black zigzag line 45 on Fig. 1 which separates the two sections of opposite magnetic polarity.

For the purpose of securing additional bearing surface-between the late 42 and the flange 4, whereby the flow ol) magnetic lines of force from said flange to said plate is facilitated, the contacting surface of the plate is broadened, and recessed so as to project downwardly in contact with the sides of said flange, as shown at 46 in Fig. 2. The same detail of construction is adopted with respect toeach of the spaced rings 47 48, 49 and 50 which are superposed respectively upon the other flanges 5, 6, 7 and 8 of the base and constitute part of the circular gap portion of the work holding face. The outer peripheral side of the plate 42 is inclined downwardly, so as to converge toward the oppositely inclined inner peripheral face or side of the ring 47. This feature of construction is also adopted with respect to the opposing sides of each pair of adjacent rings 47, 48, 49 and 50, whereby the annular spa-ces between said rings are wedge shaped in cross section, as shown in Fig. 2. Within said spaces are disposed the intermediate rings 51, 52, 53 and 54 of corresponding cross-sectional shape, the same presenting outside surfaces, on the top of the face plate substantially equal in width to the outside surfaces of the rings 47, 48, 49 and 50. The

ease of assemblage afforded by this construction of wedge shaped rings, whichdo not require the same accuracy of fit as do rings having straight vertical sides, makes it possible to braze the intermediate rings 51, 52, 53 and 54 in position, thereby providingl the thin annular non-magnetic gaps 55-62 inclusive, and thereafter to machine the upper surfaces of said rings to correspond to the upper surfaces of the rings 47 48, 49 and 50. This construction also permits the broadening of the bases of the rings 47, 48, 49 and 50, as above described, to insure adequate passage of the magnetic lines of force across the joints made with the several cores, without increasing the spaces between said cores, and also without necessitating a difference in the widths of rings on the surface of the face plate.l

As will be seen, a work holding face of the character above described, presents a concentric series of magnetized sections which alternate in magnetic polarity; and between adjacent sections' of said .series are interposed concentric sections'pf magnetic metal which are not in contact"'with the magnetizing cores of the chuck,` said latter sections being separated from the magnetized sections by continuous relatively thin non-magnetic gaps. When a piece of work to be operated upon is disposed so as to bridge one of the gaps 55--62 inclusive, being thereby in contact with one of the polarized and one of the unpolarized sections of the face plate, the magnetic circuit is completed by the leakage of magnetic lines of force across the thin gap between the unpolarized section and the next adjacent polarized section, causing said previously unpolarized section to partake of a polarity opposite to that of the polarized section which is in contact with the work. The work is thereby held by the How of magnetic lines `of force therethrough, as in an ordinary magnetic chuck.

In addition to insuring a greater number of gaps to be bridged by the work, over work holding faces which do not provide such intermediate normally unpolarized pole pieces, this construction permits ample spacesfor the coils of the chuck without unduly enlarging the pole pieces which are in magnetic contact with the cores of said coils. And while the holding power for 'a single given point upon the face of said chuck is slightly decreased by reason of the necessity for the leakage of the magnetic lines across a non-magnetic gap to complete the magnetic circuit, yet the eiiiciency ofthe chuck for certain classes of Work is greatly increased by reason of the great increase in the number of holding points afforded. For it will be clear, that, for all varieties of small work, such as washers and small rings, this construction is peculiarly adapted, by reason of the relatively close arrangement of the holding points, it being practically impossible to dispose an article of this class upon the concentric portion of the tace plate without bridging two or more of the gaps 55-62 inclusive. And for work which is relatively thin, and which therefore becomes magnetically saturated by the passage of a relatively small number of lines of force,

this construction secures the most eicient retaining means possible, by greatly multiplying the number of points at which such necessarily relatively small holding forces are applied to the work. Fig. 4 shows the further application of this principle, in a chuck which is similar in construction to the chuck shown in Figs. 1, 2 and 3 except that the number of interposed normally un- !5 magnetized pole sections of the face plate is many times multiplied. In this form of the mvention the rings 63, 64 and 65 which are superposed upon the cores or ianges 5, 6 and 7 of the base l terminate in narrow tongues 66, 67 and 68, respectively, which are substantially of the same width as the several interposed concentric rings 69, which latter are brazed or otherwise joined together t0 providea series of thin non-magnetic gaps 70 between them, as shown in Fig. 4. The cutting away of the rings 63, 64 and 65 to form the narrow tongues 66, 67 and 68 provides shoulders 71 for the support of the intermediate series of rings 69, the inner and outer rings 69 of each of said series being separated from said tongues and from said shoulders by non-magnetic, preferably brazed, circular gaps 72.

The structure above described affords the same advantages as the structure shown in Figs. 1, 2 and 3 in multiplied degree, providing a very large number of points, each exerting a somewhat limited holding power upon the work which is disposed upon the face plate.

For yconvenience of manufacture and ease of assemblage, the several rings comprising the annular gap portion of the face plate of my invention may be made in halves, as shown in Fig. 1, the brazed joints 73 of each ring being disposed preferably at right angles to the joints of adjacent rings, so as to increase the structural strength of the i face plate. As shown in Fig. 2, the face plate is held securely to the base 1 by an annular joint 74, the same being preferably formed between the underside of the ring 50 and thetlange 8 by expanding a ring of soft metal into `Vthe annular space between said parts. The above construction provides .a seal against the leakage of water into the space occupied by the coils; the

' only other openings into said coil space are effectually sealed by the provision of the bushings 22 and their coperating screws and washers 26, 29 and 25, respectively.

I claim,

1. In a magnetic chuckfa work holding face comprising sections of opposite polarity, and an unpolarized section between said sections of opposite polarity and separated v from each by a non-magnetic gap.

2. In a magnetic chuck, a work holdin face, comprising a plurality of polarized sections, with a plurality of interposed unpolarized sections bet-Ween adjacent polarized sections, separated from each other and from said polarized sections by non-magnetic gaps.

3. In a magnetic chuck, a work holding face, comprising a series of sections of alternating polarity, and a series of unpolarized sections interposed between adjacent sections of said first mentioned series and separated therefrom by non-magnetic gaps.

4. In a magnetic chuck, the combination with a member providing a plurality of spaced cores of alternating,r polarity, of a face plate super-posed therein, comprisingJ a series of sections partaking of' the polarity of said cores, and a series of unpolarized sections interposed between adjacent sections of said first mentioned series, and separated therefrom byrnon-magnetic gaps.

5. In a magnetic chuck, the combination with a member providing a plurality of spaced cores of alternating polarity, of a face plate comprising a series of sections superposed upon said cores, and a series of unpolarized sections interposed between the sections of the rst mentioned series and covering the spaces between said cores.

6. In a magnetic chuck, a member providing polarized cores, and a face plate carried thereby consisting of pole pieces, each superposed on one of said cores, and having its under surface recessed to it over the upper end of the core, whereby the contact area between pole piece and core is increased.

7. In a magnetic chuck, a member providing a plurality of spaced cores, and a. face plate superposed upon said member comprising a plurality of separate sections, of which each alternate section makes contact with one of said cores.

8. In a. magnetic chuck, a member providing a plurality of spaced cores, and a face plate superposed upon said member, comprising a plurality of Sections greater in number than said cores, said sections having non-magnetic gaps between them, certain of said sections, corresponding in number to the number of cores, being each in contact with one of said cores.

OAKLEY S. WALKER. lVitnesses:

NELLE WHALEN, PENELOPE COMBERBACH.

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