US2884572A - Magnetic chuck - Google Patents

Description

April 28, y1959 c. A. MAYNARD 2,884,572

A MAGNETIC CHUCK Filed May 25, 1955 I 2 Sheets-Sheet 1 aww @we www ATIYS.

April 28, 1959 c. A. MAYNARD MAGNETIC CHUCK 2 Sheets-Sheet 2 Filed May 25, 1955 United States MAGNETIC CHUCK Application May 25, 1955, Serial No. 510,970

4 Claims. (Cl. 317-159) The present invention is directed to an improved magnetic chuck of the type adapted to hold a ferromagnetic Work piece in position for a metal working operation such as cutting, shaping, grinding, or the like.

In the magnetic chuck of the present invention, there is provided a compact, easily operable mechanism which can very simply and quickly shift the magnetic lines of flux on the working surface of the magnetic chuck so as to produce a work holding condition or render said surface substantially neutral magnetically or even reverse the polarity as may be required to release the work.

An object of the present invention is to provide an improved magnetic chuck assembly having the characteristics mentioned above.

Another object of the invention is to provide a laminated type of magnetic chuck of compact construction.

A still further object of the present invention is to provide a magnetic chuck including interleaved sets of ferromagnetic and permanently magnetic members arranged in such a manner that the two sets of members cooperate in one position to provide a magnetic field capable of holding a ferromagnetic work piece on the surface of the chuck, and in another position yto short circuit the magnetic lines of ux to leave said surface substantially neutral magnetically.

Another object of the present invention is to provide a magnetic chuck having alternate poles both at right angles and parallel to the sides of the chuck, and means for varying the strength and polarity of the poles.

-A further description of the present invention wiil be made in conjunction with the attached sheets of drawings which illustrate a preferred embodiment of the invention.

In the drawings:

Figure 1 is a plan view of the magnetic chuck of the present invention;

Figure 2 is a broken cross-sectional view taken substantially along the line II-ll of Figure l;

Figure 3 is a cross-sectional view taken substantially along the line lll-Hi of Figure l;

Figure 4 is a fragmentary, exploded view of the magnetic chuck assembly, illustrating the manner in which the various ferromagnetic and permanently magnetic materials are aligned;

Figure 5 is a broken elevational view of one of the ferromagnetic spacer elements employed;

Figure 6 is a fragmentary cross-sectional plan view of the assembly in the deenergized position, illustrating the flux path which exists at that time; and

Figure 7 is a view similar to Figure 6 but illustrating the elements in the magnetizing position.

As shown in the drawings:

In Figure l, reference numeral 10 indicated generally a non-magnetic housing composed of brass or similar nonmagnetic material and including a pair of opposed side rails 11 and 12 and opposed end rails 13 and 1d.

The upper face of the magnetic chuck assembly presents a substantially smooth plane surface upon which arent O 2,884,552 Patented Apr. 28, 1959 ICC a ferromagnetic work piece may be laid in any position to accommodate engaging the work piece. As best seen in Figures 1 and 4, the work piece engaging surface of the magnetic chuck assembly includes a spaced series of ferromagnetic spacers indicated by numeral 16, and interleaved therewith a series of magnet carrier elements 17. The spacers 16 and the magnet carriers are secured together in the manner about to be described.

As best seen in Figure 5, each of the ferromagnetic spacers has a plurality of apertures 16a adjacent the top edge thereof, and a similar set of apertures 16b adjacent the bottom edge thereof. As best seen in Figure 2, each of the magnet carriers 17 is slidably received between a top rail 18 and a bottom rail 19 composed of non-magnetic material. Each of the rails 13 and 19 has apertures 18a and 19a, respectively, spaced to register with the apertures 16a and 16b respectively. A plurality of locking pins 21 are passed through the registering apertures and are peened over at their ends or otherwise fastened to prevent relative movement between the pins 21 and the housing 10.

The magnet carriers 17 are movable relative to the ferromagnetic spacers 16, as each of the magnet carriers 17 has a slot 17a formed therein through which a rod 22 extends. The rod 22 is free to Slide relative to the ferromagnetic spacers 16 by the provisions of elongated. slots 24 in the spacers 16 to accommodate such movement.

One end of the rod 22 is received through a slot 12a in the side rail 12 and is secured to a link 26 opera by means of an operating handle 27. A pvot is for the movement of the magnet carriers 1"/ with respect to the ferromagnetic spacers 16 is provided by a rod 28 which extends through the side rails, the ferromagnetic spacers 16, and the bottom rails 19 associated with the magnet carriers 17. Thus, as evident from Figure 2, operation of the handle 27 is effective to shift the magnet carriers 17 relative to the ferromagnetic spacers 16 to chane from the energized to the deenergized condition of the chuck, or vice versa.

As best seen in Figure 2, the magnet carriers 17 may each consist of a non-magnet carrier frame, or strip 31 composed of brass or the like in which a plurality of bar type permanent magnets 32 are positioned. The magnets 32 may be any of a large variety of permanent magnet materials, preferably of high coercive force, such as the Indox or the Alnico type. In accordance with the present invention, the bar magnets 32 are magnetized not along their long dimension, but along their thickness dimension as indicated by the solid arrows of Figure 3. As also evident from that gure, rthe magnets 32 are arranged so that each adjacent magnet has a direction of magnetization which is from the next adjacent magnet. The `significance of this arrangement will become more apparent in succeeding portions of this description.

The ferromagnetic spacers 16 are illustrated in Figure 5 of the drawings. A spacer 16 may consist simply of a relatively thin plate of iron or other ferromagnetic material having a set of non-magnetic portions such as are provided by a spaced series of windows 33 and 34 and notches 36 cut from the bottom edge of the spacer 16.

In the deenergized position of the chuck, illustrated in Figure 6, that is, with the position of the handle 27 shown in Figure 4, the ferromagnetic spacers 16 effectively provide a shunt for the magnetic flux lines, leaving the work engaging surface of the chuck in a magnetically neutral condition. Also as shown in Figure 6 by the dotted ux lines indicated therein, a low reluctance path is established in a horizontal direction because the ferromagnetic spacers 16 bridge the space between adjoining magnets 32 in the same magnetic cars) rier 17. The tendency of the ux path to be established in -the vertical direction is thereby minimized.

When, however, the opera-ting handle 27 is moved to the left, when viewed as in Figure 4, this magnetic shunt is broken by reason of the fact that the non-magnetic portions 33, 34 and 36 are disposed in alignment (Fig. 7) with the legs 32a of the magnet carrier 17 which extend between the individual magnets 32. In this alignment, the non-magnetic portions produce a high reluctance path to the establishment of magnetic fields in the horizontal direction and therefore the ux is shifted to the relatively low reluctance path provided in the vertical direction. This is best illustrated in Figure 3 of the drawings, where the dotted lines illustrate the flux path through a work piece W, and the solid arrows indicate the direction of magnetization of lthe adjoining magnets 3 2. It should be noted that in the energized condition, the flux paths for adjoining magnets are in aiding relation through the ferromagnetic spacers 16, so that a strong magnetic field is produced at the upper edges of the ferromagnetic spacers 16. Preferably, the magnet carriers 17 are moveable slightly beyond the magnetically neutral position into a position where a eld is established of reversed polarity as compared with the field existing during the work holding condition. This relatively weak reversed field existing in the surface of the chuck assists in releasing the ferromagnetic work piece.

With the arrangement shown, it is desirable to compensate for end effects which might occur if the magnets 32 were all of the same size and equally spaced in their respective carriers. For this purpose, an end magnet 39 (Figure 2) is provided in each carrier 17 which is substantially one-half the width of the other permanent magnets 32. The function of the end magnet 39 is to produce an equivalent magnetic circuit at the end of the magnetic chuck to prevent the establishment of a substantial magnetic eld at the ends of the chuck when the chuck is in its deenergized position.

The operation of the magnetic chuck of the present invention should be evident from the foregoing description. In the deenergized position of the chuck, the ferromagnetic spacers 16 are aligned with the magnet carriers 17 in the position shown in Figure 6 so that a magnetic shunt exists between the oppositely oriented magnetic faces of the permanent magnet members. In this position of the assembly therefore there is substantially no ux in the vertical direction, so that the work engaging surface of the chuck is in a substantially neutral position magnetically. When the shunt has been removed, by movement of the operating handle 27 to the left as viewed in Figure 4, the shunt is removed and replaced by a relatively high reluctance path in the horizontal direction. Hence, the magnetizable work piece W placed upon the surface of the magnetic chuck will bridge the space between adjoining permanent magnets, whether in the same carrier or in adjacent carriers, and will provide a complete ux path in the vertical direction, as best seen in Figure 3. With sufficiently strong permanent magnets, the work piece W will be held in position with sufficient force to enable the work piece to be trimmed, ground, butfed, or otherwise acted upon by suitable metal working equipment.

Ta release the work piece, it is simply necessary to move the operating handle 27 to the right, as seen in Figure 4, thereby reestablishing the magnet shunt in the longitudinal plane and permitting the work piece W to be lifted easily from the surface of the chuck. Moving the magnet carriers 17 beyond the neutral position establishes a weak eld of opposite polarity from the original polarity and aids in releasing the work piece.

It will be evident that various modifications can be made to the described embodiment without departing from the scope of the present invention.

I claim as my invention:

l. A magnetic chuck assembly comprising a non-magnetic housing, a plurality of non-magnetic magnet carriers disposed within said housing, a plurality of substantially flat magnets magnetized along their shortest dimension and carried by each of said carriers in spaced relation, a plurality of magnetic spacer elements disposed within said housing, one of said spacer elements being disposed between each successive pair of magnet carriers, said housing, said magnet carriers, and said spacer elements providing a planar working surface at one side of said housing, said spacers having apertures therein arranged so that in and out movement of said magnet carriers relative to said spacers causes said apertures to define high reluctance paths for magnetic ux tending to pass between magnets in adjoining magnet carriers transversely of said housing in one position of such movement, whereby flux may pass through a ferromagnetic object disposed on said working surface, said magnet carriers and said spacers being moveable into another position in which said spacers provide low reluctance paths between said magnets in adjoining magnet carriers, and means for causing such relative movement.

2. The assembly of claim l in which said spacers are iixedly secured in spaced relation within said housing and said magnet carriers are moveable relative thereto.

3. In a magnetic chuck assembly, a housing, a plurality of elongated magnet carriers disposed in parallel spaced relation within said housing, said magnet carriers each comprising a non-magnetic framework having spaces therein arranged to accommodate flat permanent magnets, a ilat permanent magnet located in each of said spaces, said permanent magnets being magnetized in a `direction normal to their exposed faces, a plurality of magnetic spacers in parallel spaced relation within said housing, one of said spacers being disposed between each successive pair of magnet carriers, said spacers each having non-magnetic portions therein arranged, upon relative movement between said carriers and said spacers, to provide high reluctance paths for flux through said spacers and into another position in which said spacers provide low reluctance paths for flux between oppositely ydisposed magnets.

4. In a magnetic chuck assembly, a housing, a plurality of elongated magnet carriers disposed in parallel spaced relation within said housing, said magnet carriers each comprising a non-magnetic framework having spaces therein arranged to accommodate flat permanent magnets, a iiat permanent magnet located in each of said spaces, said permanent magnets being magnetized in a direction normal to their exposed faces, the direction of magnetization of each magnet varying from that of the magnets which adjoin it, a plurality of magnetic spacers in parallel spaced relation within said housing, one of said spacers being disposed between each successive pair of magnet carriers, said spacers each having non-magnetic portions therein arranged, upon relative movement between said carriers and said spacers, to provide high reluctance paths for ux through said spacers and into another position in which said spacers provide low relnctance paths for ux between oppositely disposed magnets.

References Cited in the tile of this patent UNITED STATES PATENTS 2,187,240 Karasick ..-Jan 16, 1940

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