US3142006A

US3142006A - Permanent magnetic chuck

Info

Publication number: US3142006A
Application number: US61291A
Authority: US
Inventors: Stead Clifford
Original assignee: Taft Peirce Manufacturing Co
Current assignee: Taft Peirce Manufacturing Co
Priority date: 1960-10-07
Filing date: 1960-10-07
Publication date: 1964-07-21
Anticipated expiration: 1981-07-21
Also published as: GB941633A

Description

July 21, 1964 c. STE/1n PERMANENT MAGNETIC CHUCK 5 Sheets-Sheet 1 Filed oct. '7, 1960 July 21, 1964 CS1-EAD 3,142,005

PERMANENT MAGNETIC CHUCK Filed Oct. '7. 1960 I5 Sheets-Sheet 2 lll llllllllnlllllll MQW "1 zg [m h LL -H negli KI i 34 Ci' III l 'Q 'A' VIM ` ffii [Il n m `o\\ 2:: P if* July 21, 1964 c, s'rEAD 3,142,006

PERMANENT MAGNETIC CHUCK Filed Oct. 7, 1960 3 Sheets-Sheet 3 x my WN am United States Patent O l 3,142,006 PERMANENT MAGNETHC CHUCK Ciidord Steed, North Smithiieid, RJ., assigner to The Taft-Peirce Manufacturing Company, Woonsocket, IM., a corporation of Rhode Island Filed Oct. 7, 1960, Ser. No. 61,291 1S Claims. (Si. 3l.7 159) The present invention is concerned with improvements in work holding chucks of the permanent magnet type having one or more shiftable packs embodying magnet elements in association with a top work plate having pole pieces the packs being shifable at will to provide an on or work holding position and to an ofi or work release position.

A particular feature of the construction resides in the character of the body member and the top work plate resulting in an exceptionally rigid support for the work piece. Magnetic chucks of the type concerned require a box like construction in which are slidably mounted a pack embodying magnets. This requires that the pole pieces in the top work plate extend over unsupported or open areas where the pack or packs are positioned. However, the top plate which carries the work pieces is commonly subjected to high stresses tending to deflect the top plate and assembly and result in inaccuracies in the finished work piece. The present invention provides a construction exceptionally effective in meeting this condition. It embodies a body construction in which spaced transverse bars comprising conductor poles are cast integral with the side walls, the spaces between the integral transverse bars forming open ended channels in which `are mounted individual bars comprising magnetic poles. The ends of all of the bars or pole pieces preferably have openings or notches through which extend tie rods at each side. An interlocking matrix of plastic nonmagnetic material is cast into the spaces between bars and around the rods forming a unitary top plate of strong rigid character.

The construction has the further advantage of economy of manufacture. The open ended channels are readily machined by cross cuts and the inserted bars may be placed in position and held by the tie rods in a form and the matrix of nonmagnetic material cast throughout the desired areas firmly and accurately securing the inserted individual bars in position.

The rigidity and accuracy of the construction, and the operation of assembling and securing the parts into a unitary member are aided and enhanced by the use of a nonmagnetic matrix material comprising an epoxy resin.

A further major feature of the invention resides in the employment of two packs arranged to be shifted in parallel channels within the chuck body but in opposite directions simultaneously to like on or off positions. Since magnetic forces seek the shortest possible return path, which is a condition created when the magnetic pack is in the off position, a reluctance to shift from olf to on position commonly requires considerable effort to move a single pack. However, in the arrangement of the invention, the two packs moving in opposite directions introduce balancing forces which, in eifect, cancel out the reluctance.

Still further features and advantages of the present chuck involve the construction and relation of elements and manner of assembly of the shiftable packs. Each pack consists of a series of transverse bars or plates held together by tie rods passing through openings in the bars the openings being considerably larger than the diameter of the rods and the spaces around the rods and between the bars being filled with a continuous matrix of epoxy resin as in the case of the work plate.

lllti Patented July 21, 1964 ice The invention accordingly comprises a permanent magnet chuck having the features of construction, combination of elements and arrangement and relation of parts which will be exemplitied in the construction hereinafter set forth. Reference therefore should be had to the following detailed description taken in connection with the accompanying drawings, in which:

FlG. 1 is a view in plan of the complete assembled chuck;

FIG. 2 is a side elevation thereof;

FIG. 3 is a fragmentary cross section taken on the plane 3 3 of FIG. l showing one of the shiftable packs in its ofi position;

FiG. 4 is a fragmentary cross sectional view taken on the plane 4 4 of FIG. l showing the other pack in its corresponding ofi position;

FIG. 5 is a plan View of the body member which includes transverse bars across the top integral with the body member;

FIG. 6 is a side elevation of the body member of HG. 5;

FIG. 7 is a fragmentary view of operating elements mounted in the end or" the body member adapted to effect shifting of the packs;

FG. d is a fragmentary cross sectional view taken on the plane 8 8 of FIG. l;

FiG. 9 is a fragmentary cross sectional view generally similar to the view of FIGS. 3 and 4 but showing one of the packs in its on position;

FiG. l0 is a plan view of one of the shiftable packs; and

FIG. ll is a side elevation thereof.

The general features of the particular embodiment of the invention depicted in the drawings comprise a main body part itl shown as an individual element in FIGS. 5 and 6 and assembled in FIG. 2; a bottom plate 11 on which the body member i6 rests and a top work plate section 12 which includes transverse bars i3 formed integral with the body member liti. The body member i@ including the transverse bars i3 and the bottom plate Il are comprised of magnetically permeable metal. In the illustrated chuck the body member is provided with three vertical walls comprising the side walls 15 and 16 and the intermediate wall i7 adapted to rest on the bottom plate l1 which is secured to the vertical walls by cap screws threaded into a plurality of openings in the vertical walls of the body member It) as indicated for example at Ztl and 21. The spaced vertical walls 15, 16 and 17 define two longitudinal spaces or

channels

22 and 23 in which are mounted the shiftable packs Z4 and 25 respectively, the packs resting on the base plate 11 but having a close tit with the bottom surfaces 26 and 27 of the transverse integral bars I3, the bottom surfaces 216 being closely ground and lying in a common plane and similarly the bottom surfaces 27 (FIG. 7). The body member liti includes a top plate section 30 at one end and a top plate section 31 at the opposite end each section being integral with the body member. End plates 32 and 33 (FIG. 2) are removably secured over the ends of the body member, the end plate 32 enclosing an eccentric mechanism for shifting the packs as will be described below. Located between each end plate 32 and 33 and the body member is a gasket seal 32a and 3m respectively which may be of a neoprene rubber composition commonly used for such purposes. The top plate section 3l may have secured thereto an end stop plate 3F held in pla by suitable screw bolts 36. The back side of the chuck may also have a stop plate 37 as` indicated in FIG. l secured to body wall l5 by suitable screws such as indicated at 38. Mounted within the body member at the right end as shown in FIGS.

1 and 2 and in vertical broken away section in FIG. 7 is an eccentric mechanism or crankshaft for shifting the two packs, the mechanism including a cross shaft 4t) having suitable bearing mounts 41 and i2 in the respective side walls and 16. Mounted upon or integral with the cross shaft 40 are two spaced

eccentrics

46 and 47 on which are mounted links 4S and 49 respectively the link 48 being connected to the shiftable pack 2liand link 49 to the pack 25 as will be described in more detail below.

As has been stated above the body member 19 includes the integral cross bars 13 extending over the three vertical walls and preferably slightly beyond the vertical wall at each side as indicated particularly in FIG. 5. The transverse bars 13 therefore dene transverse channels 5b and inserted in each of these channels is an individual bar 51, the bars 51 being smaller than the channels and surrounded by and insulated from the adjacent integral bars by non-magnetic material as indicated at 52.

The bars 51 at each end thereof have a notch 55, as indicated in the detail cross sectional View of FIG. 8, and the integral bars 1.3 of the body member 11i are provided with similar notches 56 (FIG. 6). Extending through the successively

alternate notches

55 and 56 at each end of the bars are tie rods 6@ and 61. The tie rods are shown in FIG. 1, and a fragment tie rod 61 is shown in FIG. 5. The top end plate 30 is provided with a notch 62, and similarly the top end plate 31 is provided with a notch 63, each in alignment with the notches 56. FIG. 6 shows these notches at one side of the body member but it will be understood that the opposite side is similarly formed. In assembly the tie rods are easily inserted laterally from the side in each case and the desired non-magnetic material is then cast throughout the various spaces, the non-magnetic material between the top transverse bars being shown at 52 and the material extending into the notches 55 being indicated at 64, see for example FIG. 8 in this latter respect. The cast plastic material therefore forms a continuous network or matrix acting in conjunction with the

tie rods

60 and 61 to hold the parts forming the work plate section 12 in one solid unitary member of very rigid character. The character of the work plate section together with the fact that the bars 13 are cast integral with the vertical walls results in a work supporting surface practically free of deflection under any stress to which it is normally subjected.

The non-magnetic material may vary depending upon the circumstances and accordingly may be the usual type of Babbit or a suitable plastic material. It has been found that a particularly advantageous type of material which is exceptionally effective in the present construction in achieving a strong rigid unitary base plate and free of liquid leakage comprises an epoxy resin composition. The properties of the epoxy resins of course differ somewhat dependent upon the exact chemical composition, the epoxy resin here employed being of the casting type hardenable by chemical reaction with a suitable reagent. Just prior to casting and shaping of the material an appropriate reagent is added thereto and the plastic material becomes strong and hard within a matter of a few hours at least. A particularly satisfactory epoxy resin is one sold under the trade name Isocast to which is added a hardener No. 16 sold under the trade name Isochem In the form of chuck specifically illustrated in the drawings, two shiftable packs operable in parallelism are employed, and the body member 10 has an intermediate wall 17 integral with the body member which serves to define the two

channels

22 and 23 for the respective packs and to help support the overhead transverse bars and add to the rigidity of the work supporting surface in general. It will be understood, however, that in some cases, depending upon the conditions including the dimensions of the work table and various parts, and whether a single shiftable pack will suffice, sulcient rigidity may be attained without the embodiment of the intermediate vertical wall.

Referring to FIGS. l0 and ll showing the construction of one of the packs, which may be assumed to be the pack 24 but is representative also of the pack 25, it will be seen that the pack comprises a series of transverse bars or plates which are alternately metal bars 70 of magnetically permeable material such as cold rolled steel, and magnets 71 of well known type such as Alnico. The pack is provided with an end plate 72 at the left end and an end plate '73 at the opposite end, the latter having a pair of ears 74 in which is pivotally secured the operating link 49 heretofore referred to. Extending through the pack are a pair of tie rods 75 and 76 the tie rods being threaded into the end plate 73, the opposite ends of the tie rods also being threaded and extending through the end plate 72 with clamping nuts 77 applied to the respective ends. It will be observed that the magnets 71 are shorter than the steel bars 7 tl; and also that the holes through all of the bars are substantially larger than the inserted tie rods. In assembly the parts are all positioned preferably in a suitable form and held in proper relation and then the non-magnetic plastic material is cast throughout all the open spaces. Accordingly it surrounds the tie rods 75 and 76 within the enlarged holes of the respective bars as indicated at 78, and extends into the spaces between the successive bars as indicated at 79, and also around the outer ends of the magnets, as indicated at 3u. The plastic material therefore forms a continuous matrix helping to hold the assembled parts as a unitary rigid member.

An important feature of the invention resides in the balanced arrangement of the two

packs

24 and 25 and the operating mechanism therefor. As previously described the operating mechanism includes a common operating shaft 4t) and the

eccentrics

46 and 47 with their connections to the

respective packs

24 and 25. The relation of the eccentrics and their proportions are such that upon rotation of the shaft 40 the two

packs

24 and 25 are moved in opposite directions but to similar positions functionally. The shaft iti may be rotated from any suitable means which in the present case comprises a handle secured in a collar S6 which in turn is secured to the shaft 4@ by a suitable means such as a set screw 87. FIGS. l, 2, 3 and 4 show the stacks both shifted to their off position, which for the stack 24 is its extreme position to the left (FIG. 3), and for the stack 25 is its extreme position to the right. In each of these positions the lines of magnetic force are bypassed through the magnetically permeable pole pieces in the top plate as indicated at in FIGS. 3 and 4. Upon rotation of the handle 85 clockwise in FIG. 2 through a suitable angle, which in the present case is about the pack 24 is shifted to the right and the pack 25 to the left in FIG. l and each of the packs is now in a position corresponding to that shown in FIG. 9 which represents the pack 24 and a section similar to FIG. 3 except that the pack has been moved to the right. In this position each of the magnet bars 71 in the shiftable pack is located directly under a conductor pole piece 51 in the top plate and correspondingly each conductor bar 70 in the pack is located directly under one of the conductor poles 13 integral with the body member 111 and the lines of force are caused to extend up through the work piece W as indicated at 91 in FIG. 9.

Various changes may be made in the above construction and different embodiments of the invention could be made without departing from the scope thereof, and it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. In a permanent magnetic chuck, a body member having vertical side walls and upper bars extending transversely between the side walls and integral therewith, said bars being spaced laterally from each other forming transverse channels open at each end, and an inserted transverse bar mounted in each of said channels between said integral bars and separated therefrom and supported in each case by solid cast non-magnetic material, said lntegral and inserted bars each comprising a pole piece and each having an upper surface located in a common plane and forming the top surface of a work plate.

2. In a magnetic chuck, a body member having vertical side walls and upper bars extending transversely between the side walls and integral therewith, said bars being spaced laterally from each other forming transverse channels open at each end, and an inserted transverse bar mounted in each of said channels between said integral bars and separated therefrom in each case by non-magnetic material, said bars comprising pole pieces, and tie rods extending successively through said integral and inserted bars.

3. In a magnetic chuck, a body member having side walls and upper bars extending transversely over the side walls and integral therewith, said bars being spaced laterally from each other forming transverse channels open at each end, an inserted transverse bar mounted in each of said channels and laterally spaced from the adjacent integral bars in each case, said bars being of magnetic material, tie rods extending through said integral and inserted bars, and a matrix of non-magnetic material cast around said tie rods and in the spaces between bars to bind the parts together in a unitary assembly.

4. In a magnetic chuck, a body member having side walls and upper bars extending transversely over the side walls and integral therewith, said bars being spaced laterally from each other forming transverse channels open at each end, an inserted transverse bar mounted in each of said channels and laterally spaced from the adjacent integral bars in each case, said bars being of magnetic material, tie rods extending through said integral and inserted bars, and a matrix of non-magnetic epoxy resin plastic material cast in place around said tie rods and in the spaces between bars to bind the parts together 1n a unitary assembly.

5. In a magnetic chuck, a body member having side walls and upper bars extending transversely over the side walls and integral therewith, said bars being spaced laterally from each other forming transverse channels open at each end, an inserted transverse bar mounted in each of said channels and laterally spaced from the adjacent integral bars in each case, said bars being of magnetic material, each of said bars having an opening in r each end, a tie rod extending successively through said openings at each end, and a matrix of non-magnetic material cast around said tie rods and in the spaces between bars to bind the parts together in a unitary assembly.

6. In a magnetic chuck, a body member having vertical side walls with a space therebetween and upper bars extending transversely between the side walls and integral therewith, said bars being spaced laterally from each other forming transverse channels open at each end, and an inserted transverse bar mounted in each of said channels between said integral bars and laterally spaced from the adjacent integral bar in each case, a matrix of nonmagnetic material cast in the spaces around said insert bars to form with said integral bars a work plate, a bottom plate on which said side walls rest, and shiftable means embodying magnetic elements mounted in said space between the side walls and resting on savimd base plate, said integral and inserted bars comprising pole pieces in association with said magnetic elements.

7. In a magnetic chuck, a body construction including a work plate having pole pieces therein, a pair of shiftable packs embodying magnetic elements mounted adjacent said plate, each of said packs being shiftable to on and olf positions but in opposite directions for 6 the corresponding positions, a common operating means mounted in said body construction and operating connections therefrom to each of said packs for simultaneously operating said packs in opposite directions and correspondingly simultaneously to on or olf positions as elected.

8. In a magnetic chuck, a body construction including a work plate having pole pieces therein, a pair of shiftable packs embodying magnetic elements mounted adjacent said plate, a pair of eccentrics rotatably mounted in said body construction, means for rotating said eccentrics simultaneously, an operating connection from one of said eccentrics to one of said packs and an operating connection from the other eccentric to the other pack whereby rotation of said eccentrics shifts said packs, the eccentrics and operating means and packs being so related that a predetermined operation of the eccentrics causes the two packs to be shifted simultaneously in opposite directions to chuck on positions respectively, and further predetermined operation of the eccentrics causes the two packs to be shifted simultaneously in opposite directions to chuck off positions respectively.

9. In a magnetic chuck, a body construction including a work plate having pole pieces therein, a pair of shiftable packs embodying magnetic elements mounted in said body construction adjacent said plate and adapted to be shifted in parallel paths, a pair of eccentrics on a common shaft rotatably mounted in said body construction transversely of said paths, means for rotating said eccentrics, an operating connection from one of said eccentrics to one of said packs and an operating connection from the other eccentric to the other pack whereby rotation of said eccentrics shifts said packs, the eccentrics and operating means and packs being so related that a predetermined operation of the eccentrics causes the two packs to be shifted simultaneously in opposite directions to chuck on positions respectively, and further predetermined operation of the eccentric causes the two packs to be shifted simultaneously in opposite directions to chuck off positions respectively.

l0. In a magnetic chuck, a body member having a vertical wall at each side and an intermediate vertical wall, said walls being parallel and deiining two longitudinal extending openings, upper bars extending trans versely over said side and intermediate walls and cast integral therewith, said bars being spaced laterally from each other forming transverse channels open at each end, and an inserted transverse bar mounted in each of said channels and laterally spaced from the adjacent integral bars in each case, each of said bars being of magnetic material, non-magnetic material cast in the spaces between bars, a base plate on which said walls rest, and a pack embodying magnet elements mounted in each of said longitudinal openings and shiftable longitudinally thereof.

ll. In a magnetic chuck, a body member having a vertical wall at each side and an intermediate vertical wall, said walls being parallel and defining two longitudinally extending openings, upper bars extending transversely over said side and intermediate walls and cast integral therewith, said bars being spaced laterally from each other forming transverse channels open at each end, and an inserted transverse bar mounted in each of said channels and laterally spaced from the adjacent integral bars in each case, said bars being of magnetic material and each of said bars having an opening at each end, a tie rod extending successively through said openings at each end, a matrix of non-magnetic material cast in the spaces between bars and around said tie rods to bind the bars and tie rods into a unitary assembly, a base plate on which said walls rest, and a pack embodying magnet elements mounted in each of said longitudinal openings and shiftable longitudinally thereof.

12. In a magnetic chuck, a shiftable pack comprising a plurality of bars extending transversely of the direction of shifting of the pack and including magnet bars arranged successively and parallel but spaced from each other, tie rods extending through aligned openings in the successive bars longitudinally of the pack, said openings being larger than the diameter of the tie rods, and a matrix of nonmagnetic material cast in said spaces and extending into said openings around said tie rods.

13. In a magnetic chuck, a shiftable pack comprising a plurality of bars extending transversely of the direction of shifting of the pack and including magnet bars arranged successively and parallel but spaced from each other, tie rods extending through aligned openings in the successive bars longitudinally of the pack, said openings being larger than the diameter of the tie rods, and a matrix of nonmagnetic epoxy resin plastic material cast in said spaces and extending into said openings around said tie rods.

14. In a magnetic chuck, a shiftable pack comprising a plurality of alternately permanent magnet and magnetically permeable bars extending transversely of the direction of shifting of the pack and arranged successively and parallel but spaced from each other, tie rods extending through aligned openings in the successive bars longitudinally of the pack, said openings being larger than tle diameter of the tie rods, and a matrix of non-magnetic epoxy resin plastic material cast in said spaces and extending into said openings around said tie rods.

l5. In a permanent magnetic chuck, a body member having vertical side Walls and upper bars integral therewith and extending transversely from the outer surface of one side wall to the outer surface of the other side Wall, said bars being spaced laterally from each other forming transverse channels open at each end, and an inserted transverse bar mounted in each of said channels between said integral bars and extending at each end over the respective side wall and separated from the adjacent integrai bar and from the side Walls in each case by solid cast non-magnetic material, said integral and inserted bars each comprising a pole piece and each having an upper surface located in a common plane and forming the top surface of a work plate.

References Cited in the tile of this patent UNITED STATES PATENTS 2,286,238 Simmons June 16, 1942 2,609,430 Bower Sept. 2, 1952 2,700,744 Simmons Jan. 25, 1955

Claims

1. IN A PERMANENT MAGNETIC CHUCK, A BODY MEMBER HAVING VERTICAL SIDE WALLS AND UPPER BARS EXTENDING TRANSVERSELY BETWEEN THE SIDE WALLS AND INTEGRAL THEREWITH, SAID BARS BEING SPACED LATERALLY FROM EACH OTHER FORMING TRANSVERSE CHANNELS OPEN AT EACH END, AND AN INSERTED TRANSVERSE BAR MOUNTED IN EACH OF SAID CHANNELS BETWEEN SAID INTEGRAL BARS AND SEPARATED THEREFROM AND SUPPORTED IN EACH CASE BY SOLID CAST NON-MAGNETIC MATERIAL, SAID INTEGRAL AND INSERTED BARS EACH COMPRISING A POLE PIECE AND EACH HAVING AN UPPER SURFACE LOCATED IN A COMMON PLANE AND FORMING THE TOP SURFACE OF A WORK PLATE.