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July 23, 1946. s. I. HITCHCOCK 2,404,710 PERMANENT MAGNET STRUCTURE Filed July 2, 1943 8Y - 7340.17.’ Wm I A 77'0R/VEV 2,404,716 Patented July 23, 1946 UNiTED STATES PATENT ()FFICE 2,404,710 PERDIANENT MAGNET STRUCTURE Stanley Isaiah Hitchcock, London, England Application July 2, 1943, Serial No. 493,238 In Great Britain July 14, 1942 1 4 Claims. (Cl. 175-367) 2 material. ble comprises members 28 composed of soft iron or other magnetic material having a high ini tial permeability and intervening spacing mem bers 25 or non-magnetic material, the members 28 and ‘it being enclosed within a surrounding frame 32 which may conveniently be die-cast It has been found in the course of experiments that if the poles of a permanent magnet are joined by a soft iron or other member of mag from a suitable non-magnetic material. The table is slidably mounted on a base like wise built up of members 39 of soft iron or other This invention relates to permanent magnet structures wherein a permanent magnet is asso ciated with a soft iron or other armature mem ber separated from the pole faces of the magnet by an intervening air gap or layer of insulating netic material having a high initial permeability 10 magnetic material having a high initial perme such as “Mu-metal” which is divided up into sec ability and intervening non-magnetic spacing members 3%, the members 30 and 3! being also tions, the sections being separated by non-mag enclosed within a surrounding frame 32a com netic material, that the lines of magnetic force posed of non-magnetic material and formed for will pass through the sections, although the sec~ tic-ns with the intervening layers of non-magnetic 15 example by a die-casting process. The members and so may if desired be of laminated con material will have a higher reluctance than in the member comprised of a single piece of soft struction. Located within the base is a permanent mag iron or other magnetic material. net 33 the end faces of which adjacent the poles It is proposed therefore in accordance with the present invention to provide a permanent mag 20 contact the adjacent members 38. The upper, lower and lateral faces of the magnet may either net with such a ?ux path, and to construct an be in contact with the members 38 or separated other member for use with such a magnet, in a therefrom by intervening spacing members of similar manner, said other member being sepa non-magnetic material or alternatively separat rated from the sectioned member providing the ed by an intervening air gap. The members 30 ?ux path by an air gap or a layer of non-mag and 3| and permanent magnet are contained netic material, said other member and perma within a surrounding frame 3241 which may be nent magnet being relatively movable to permit conveniently die-cast from a non-magnetic ma of the sections comprising the flux path and the other member to lie opposite one another or to terial. The upper member or table when not in opera occupy a position in which they lie in staggered tion occupies the position shown in the ?gure relationship. In this way the degree of attrac in which position the members 28 of the table in tive force between the permanent magnet and the absence of the workpiece ful?ll the function the other member can be varied as it has been of a keeper. the members 28 absorbing the un found as a result of experiments, that when the wanted magnetic ?ux, the lines of magnetic flux various sections are oppositely arranged the lines following a zig-zag path of least reluctance of magnetic force pass mainly through the flux through the members 353 and 28, the lines of mag path, the attractive force exerted on the other netic ?ux being con?ned to the inner ends of member being nil or small whilst when the sec the members 23. When the table is moved into a tions occupy a staggered position the lines of magnetic force take a zig-zag path. through the 40 position in which the members 28 and 3B are in alignment, the lines of magnetic ?ux emanating ?ux path and the other member, the attractive from the poles of the magnet 33 pass upwardly force being then materially increased. through the aligned members 38 and 23 into the In order that the said invention may be clearly understood and readily carried into effect, the workpiece thus exerting a powerful attractive same will now be further described with refer ence to the accompanying drawing, wherein the single ?gure is a sectional view disclosing a mag ' force on the workpiece and maintaining it in position on the table. When it is desired to in crease the magnetic attraction to maintain the workpiece in position, the table is moved into a position in which the parts 25 and ?il are disposed The application of this invention that is 50 in alignment, movement being effected by the lever 34 which is pivotally connected with the shown in the ?gure comprises a magnetic bench base at the point 35 and pivotally connected to which includes a base and an upper member or the upper part or table at the point 35. table on which a workpiece or workpieces can be What I claim and desire to secure by Letters placed and retained ?rmly in position thereon during a machining or other operation. The ta 65 Patent of the United States is: netic bench constructed in accordance with the present invention. 2,404,710 3 1. A permanent magnet structure comprising a permanent magnet having a flux leakage path rift bers of high initial permeability separated by intervening members of non-magnetic material, between its poles, and an armature member for use therewith said flux leakage path and arma one of said elements overlying the other with the members of both elements extending in the same ture member being constructed in a similar man direction, one of said elements containing a per her and being built up of a series of members manent maget, and means for imparting move composed of soft iron or other magnetic material having a high initial permeability and interven ing spacing members of non-magnetic material, members of high initial permeability of said ele ment to and from staggered position with respect ment to the other of said elements to shift the and means for moving said armature member to the like members of the other element to thereby Vary the density of the magnetic ?eld endwise from a position in which the soft iron members of the armature and flux leakage path existing between the two elements. 4. A magnetic workbench comprising a table lie opposite or in line into a position in which the parts occupy a‘ staggered position and vice for the reception of the Work, and a base, said versa, for the purpose of controlling the pas- 15 table and said base each including a series of sage of the lines of magnetic force emanating members of high permeability material sepa~ from the permanent magnet, through the arma“ rated by intervening members of non-magnetic ture member, and thereby increasing or decreas material, the members of said table and said base ing the attractive force between the permanent extending in the same direction, the members magnet and its associated armature member. 20 included in said base enclosing a permanent mag~ 2. A magnetic Workbench comprising an upper table net, the being members each enclosed included within in said abase surrounding and member or table and a lower member or base, the table including a series of members com frame of non~magnetic material, and means for posed of soft iron or other magentic material imparting movement to said table in a direction having a high initial permeability and separated at right-angles to the length of said members to by intervening members of non-magnetic mate move the members included in said table into and out of staggered relationship with regard to rial, the lower member likewise comprising a se— ries of soft iron or like members with interven the members included in said base to thereby ing non-magnetic spacing members, the lower control the liners of magnetic ?ux emanating from member containing a permanent magnet and the permanent magnet, the members when in line means for imparting relative movement to the permitting the maximum number of lines of mag upper and lower members to bring the soft iron or netic ?ux to pass through the work, and the like members in the upper and lower members work to be held ?rmly on the table, the members into a position in which they occupy a relatively when in a staggered position providing an alter staggered postion, or an inline position for the 35 native path for the lines of magnetic ?ux of a purpose of causing the permanent magnet to exert lower reluctance than that which they would a suf?ciently high degree of magnetic attraction have to take to pass through the work, the num on a workpiece placed on the table to retain it in ber of lines of magnetic flux passing through position thereon, or, to so reduce the magnetic the work being thus reduced to a minimum, attraction to permit of the workpieces removal. 40 thereby enabling the work to be removed from 3. A permanent magnet structure comprising the table without dif?culty. two elements each including a like series of mem STANLEY ISAIAH I-II'I‘CHCOCK.