Universal Electrode Holder

The present invention relates to electrode holders and, more particularly, to a universal electrode holder that may be employed in conjunction with apparatus for the removal of metal by electrical machining techniques.

Typical of such apparatus is an electrical discharge machining device (EDM), wherein a supply of dielectric fluid is delivered to the working faces of the electrodes, usually through internal passages in the electrodes. With machines of this type various sizes and shapes of electrodes are employed which, thereby compounds the task of attaching a fluid supply to such diverse electrodes. Moreover, the variation in electrode designs necessitates the use of special holders for different types. For example, a long electrode having planar side edges might require one type of holder; whereas an annular disc or plate-type electrode might require another type of holder. Oftentimes a V-shaped clamping block is employed as a holder, thereby requiring the electrodes to have shanks for gripping contact with the clamping block. This general type of holder makes precise positioning of the electrode with respect to the work stock extremely difficult (if not impossible) when the electrode has to be changed and/or replaced.

The foregoing problems, as well as others not specifically mentioned, are overcome according to the teachings of the present invention, which provides a universal electrode holder wherein a single fluid supply hook-up suffices for substantially all types and sizes of electrodes.

Further, the electrode holder of the present invention permits the mounting of either long, planar surfaced electrodes or shankless plate or disc-type electrodes without necessitating any changes in the fluid supply thereto or the fitting of the individual electrode with fluid couplings.

According to the present invention, the electrodes may be either side or bottom mounted to the holder body with assurance that repeatable and precise positioning is accomplished without any adjustments in the event an electrode has to be replaced with a substitute, due to wear or the like.

Essentially, then, the universal electrode holder of the present invention comprises; a holder body having at least one sidewall, which is stepped to define a vertically disposed lower portion and vertically disposed upper portion arranged outwardly of the lower portion and integrally connected thereto by a substantially horizontally disposed connecting portion; a reference or abutment plate fixed to an end wall of the holder and having a reference surface disposed normal to said one side wall; an indexing plate movable fixed for surface to surface engagement with the lower and connecting portions for selectively positioning an end indexing surface thereof in an adjustable spaced relationship relative to the reference surface; clamp means selectively securable in a plurality of predetermined positions along the upper portion for rigidly clamping an electrode to the holder body while positionally located by surface engagement with the indexing and reference surfaces and the connecting and lower portions; and conduit means defined by the holder body and by cooperation of the lower portion and indexing plate for supplying dielectric fluid to the electrode when the same is clamped to the holder body.

The present invention also contemplates the provision of registration means on a bottom face of the electrode holder body, which includes at least two ribs depending from the bottom face and having intersecting longitudinal axes; the ribs being structured for alignment and engagement with complementary structure on a shankless electrode, whereby the same may be precisely positioned and secured to the bottom face. The conduit means defined by the holder body may additionally provide a supply of dielectric fluid to the shankless electrode.

In accordance with the present invention, means provided on the top face of the electrode holder body facilitate mounting thereof in alignment with complementary structure on the mounting head of an EDM device, and if desired, to place the conduit means of the holder body in flow communication with a source of dielectric fluid. Alternately, the mounting head of the EDM device may be fitted with a side mounted fluid supply block having a supply passage adapted to be automatically aligned with the conduit means of the holder body incident to mounting thereof on the mounting head.

Other features and advantages of the present invention will become readily apparent as a detailed description thereof proceeds.

For a fuller understanding of the present invention reference should now be had to the following detailed description thereof taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a front elevational view of the electrode holder of the invention depicting an electrode bottom mounted thereto;

FIG. 2 is a view of the electrode holder similar to FIG. 1, but depicting an electrode mounted to a sidewall thereof;

FIG. 3 is a side elevational view of the electrode holder of FIG. 2 looking in the direction of line 3--3 thereof;

FIG. 4 is a bottom view of the electrode holder looking in the direction of line 4--4 of FIG. 1;

FIG. 5 is a plan view of an electrode mounted to the bottom face of the electrode holder looking in the direction of line 5--5 of FIG. 1;

FIG. 6 is a bottom view of the electrode depicted in FIG. 5;

FIG. 7 is a fragmentary sectional view depicting the electrode holder mounted to the head of an EDM device; and

FIG. 8 is a fragmentary view of an alternate form of means to facilitate the mounting and alignment of the electrode holder to an EDM device or the like.

Referring in detail to the drawings, the electrode holder according to the present invention includes a body 10 of general block form and having a top face 12, a bottom face 14, a pair of sidewalls 16 and 18 and a pair of end walls 20 and 22. Sidewalls 16 and 18 are substantially perpendicularly disposed with respect to end walls 20 and 22 and with respect to faces 12 and 14. At least sidewall 16 is stepped to define a vertically disposed lower surface portion 24, a vertically disposed upper surface portion 26 arranged relatively outwardly of or to overlie lower surface portion 24, and a substantially horizontally disposed connecting surface portion 28 integrally joined in a right angular relationship to surface portions 24 and 26.

By now referring particularly to FIGS. 2 and 3, it will be understood that reference and indexing means are operably associated with holder body 10 for the purpose of positionally locating a first type of electrode E of rectangular cross-section adjacent side wall 16 in engagement with lower and connecting surface portions 24 and 28. Specifically, the reference means is best shown in FIGS. 1-4 as including a reference or abutment plate 30 removably secured to end wall 22 by means of a threaded fastener device 32 received in an appropriately located one of a plurality of threaded apertures 22a opening through the surface of end wall 22. In the illustrated construction, reference plate 30 is provided with a reference or abutment surface 30a, which is clamped against the surface of end wall 22 and arranged to project transversly of lower and connecting portions 24 and 28.

It will be understood that the illustrated reference plate 30 may be replaced with any suitably constructed extension member, as required to locate surface 30a in an outwardly spaced relationship relative to the surface of end wall 22 in order to accommodate for mounting of an electrode having a substantially greater widthwise dimension than that illustrated in FIG. 2.

Now referring particularly to FIGS. 1, 2 and 4, it will be understood that the above mentioned indexing means is preferably in the form of an elongated, indexing plate 34 of rectangular cross-section, which is provided with an indexing or end surface 34a intended to be disposed in a parallel relationship to reference surface 30a, and rear side and upper edge surfaces 34b and 34c intended to be disposed in surface to surface sliding engagement with lower and connecting surface portions 24 and 28, respectively. Preferably, the outwardly facing side surface 34d and the lower edge surface 34e of plate 34 are disposed to lie essentially flush with or slightly inwardly of upper surface portion 26 and bottom face 14, respectively. Indexing plate 34 is formed with a pair of slots 36, which extend lengthwise of the plate in an essentially parallel relationship to each other and edge surfaces 34c and 34e, and which are positioned for alignment with a pair of parallel rows of threaded apertures 38 opening through lower surface portion 24. Slots 36 and apertures 38 are sized to receive fastener devices 40, which serve to selectively and releasably retain indexing plate 30 in a desired adjusted position determined by the widthwise dimension of electrode E to be secured to holder body 10. For instances where an electrode to be mounted has a substantial widthwise dimension, which for example can not be accommodated for by the fixing of an extension member to end wall 22 in the manner mentioned above, it is contemplated that a suitable fixture be mounted on end wall 20, as by fastener devices received within threaded apertures similar to those provided for end wall 22, for the purpose of extending lower and connecting surface portions 24 and 28, as required to support and increase the range of sliding movements of plate 34.

Preferably, holder body surface portions 24 and 28 and indexing plate surfaces 34b and 34c are suitably polished and/or machined to provide for intimate, surface to surface sliding engagement of the indexing plate with the holder body, as well as intimate surface to surface abutting engagement of such holder surface portions with the upper end and rear side surfaces of electrode E. In like manner, reference surface 30a and indexing surface 34a are preferably polished and/or machined, so as to permit intimate, surface to surface abutting engagement thereof with parallel edge surfaces of electrode E in the manner shown in FIG. 2.

By again referring to FIGS. 2 and 3, it will be understood that suitable clamping means is provided for securing side mounted electrode E in place between reference plate 30 and indexing plate 34 and in engagement with holder sidewall portions 24 and 28. Such means preferably includes a clamp arm 42 selectively securable to holder body 10 by a threaded fastener 44 sized to loosely extend through an elongated arm slot 42a for receipt within a selected one of a plurality of threaded apertures 26a, which open through upper surface portion 26 and are spaced apart lengthwise thereof. Clamp arm 42 includes, when in its operative position shown in FIG. 2, a lower end section 42b adapted to be arranged in a facing relationship with lower surface portion 24 for surface bearing engagement with the outwardly facing or front side surface of electrode E, as viewed in FIGS. 2 and 3, and an upper end section 42c, which is threaded to receive a clamping or adjustment screw device 46 arranged to have its inner end bear against upper surface portion 26. As will be apparent, adjustments of screw devices 44 and 46 serve to displace and/or tilt arm 42 as required to accommodate for the mounting of electrodes of varying thickness, whereas threaded apertures 26a permit placement of the clamp arm at various positions lengthwise of upper surface portion 26, as required to appxoximately center the clamp arm relative to electrodes of varying widthwise dimensions.

By the provision of cooperating surfaces 24, 28, 30a and 34, a precise reference orientation is provided for permitting replacement of one electrode with an identically sized electrode, without necessitating any adjustment of parts other than adjustment of screw devices 44 and/or 46, as required for electrode unclamping/clamping purposes. Further, it will be appreciated that surfaces 24, 28 and 30a cooperate to provide an accurately defined reference for use in mounting electrodes of varying size relative to holder body 10.

The universal electrode holder of the present invention also provides a bottom mounting support for a second type of electrode shown as a plate type electrode E', which obviates the prior requirement that the upper surface 50 of such electrode be fitted with a separately fabricated or integrally formed shank for electrode support and orientation purposes. Specifically, holder body 10 is provided with registration means, such as may be defined for example by four ribs 60, 62, 64 and 66 arranged to depend from holder bottom face 14; and electrode mounting means, such as may be defined by apertures 68 having lower ends opening through holder bottom face 14 and upper ends communicating with access cavities 70 and 72, which in turn open through holder body side walls 20 and 22, respectively.

As best shown in FIG. 5, shankless upper surface 50 of electrode E', as fabricated for use with the present holder, is provided with a pair of intersecting channels 74 and 76, which are complementary to and sized to receive ribs 60, 62 and 64, 66, respectively, with the ribs preferably bottoming out within their respective channels and surface 50 disposed in intimate surface to surface engagement with bottom surface 14. Preferably, electrode E' would be provided with threaded openings 78 disposed for alignment with apertures 68 in order to permit threaded fastener devices 80 to be inserted within the cavities 70 and 72 and passed downwardly through apertures 68 for receipt within such threaded openings for electrode mounting purposes. It is, however, specifically contemplated that apertures 68 may be threaded and openings 78 formed as bore openings, such as to permit threaded devices, not shown, to be passed upwardly through electrode E' for mounting purposes.

In the case of an EDM or similar apparatus, a dielectric fluid must be supplied to the working face or faces of electrodes mounted on holder body 10. It is, therefore, a further feature of the present invention that holder body 10 incorporates conduit means for supplying dielectric fluid to the electrodes, regardless of the size of such electrodes and whether same are mounted to depend from the side or bottom of the holder body. To this end, holder body 10 is provided with a vertically extending through passageway 90 having its upper and lower ends 90a and 90b threaded to removably receive fluid flow blocking plugs, not shown, and arranged to open centrally of holder top and bottom faces 12 and 14, respectively. As best shown in FIG. 7, passageway 90 is disposed in flow communication with the inner ends of side passageways 92 and 94, which in turn open outwardly through said wall 18 and lower surface portion 24, respectively, and have their respective outer ends 92a and 94a threaded to removably receive fluid flow blocking plugs, also not shown.

Now referring to FIGS. 1, 3 and 7, it will be noted that the outer end of passageway 94 opens centrally of a channel recess 96, which extends lengthwise of lower surface portion 24 with its opposite ends arranged slightly inwardly of end walls 20 and 22. It will also be noted that electrode E is provided with a passageway 98 for conveying dielectric fluid to its working or lower end, not shown, and that such passageway is provided with an inlet end 98a, which is arranged to open through its rear side surface for alignment with channel recess 96, when the electrode is clamped in mounted position, as best shown in FIGS. 2 and 3. As will be apparent, when indexing plate 34 and electrode E are positioned and clamped to holder body 10, as best shown in FIG. 2, the planar rear side surface 34b of the indexing plate and the planar rear side surface of the electrode cooperate with lower surface portion 24 to provide a flow passageway extending along channel 96 for directing dielectric fluid between side passageway 94 and electrode passageway inlet end 98a for all adjusted positions of the indexing plate, as determined by the length of slots 36 and the placement of threaded apertures 38. When it is desired to supply dielectric fluid to side mounted electrode E, the lower end 90b of passageway 90 is normally suitably plugged, and the outer end of said passageway 92 or the upper end 90a of passageway 90 connected to a suitable source of dielectric fluid, depending upon the type and design of machine with which the present invention is employed, and the other of such outer or upper ends fitted with an appropriate plug, as in the case of lower end of passageway 90, to prevent the loss of dielectric fluid.

Again referring to FIGS. 4 and 5, it will be noted that relatively inner ends of ribs 60, 62, 64 and 66 are spaced radially from passageway 90, and that fluid distributing channels 100 are provided in electrode upper surface 50 and arranged such that their inner ends 100a communicate with channels 74 and 76 adjacent their juncture and relatively inwardly of ribs 60, 62, 64 and 66. The outer ends 96b of channels 100 communicate with desired numbers of dielectric fluid distributing orifices 102, which extend through electrode E' and are arranged in a pattern determined by the configuration of the contoured working or lower face 50' of electrode E', and thus the desired distribution of dielectric fluid across such face. It will be understood that when electrode E' is clamped to holder body 10, their facing or engaging surfaces, cooperate to provide fluid flow passages, whose inner ends communicate with passageway 90 and whose outer ends communicate with orifices 102. If desired, the center of electrode E' may be provided with an additional orifice 98' disposed in alignment for flow communication with passageway 90. When it is desired to supply dielectric fluid to a bottom mounted electrode E', the outer end of side passageway 94 would normally be suitably plugged, and the outer end of said passageway 92 or the upper end of passageway 90 connected to a suitable source of dielectric fluid, depending upon the type and design of machine with which the present invention is employed, and the other of such outer or upper ends fitted with an appropriate plug, as in the case of said passageway 94, to prevent the loss of dielectric fluid.

Any suitable means may be provided on top face 12 of holder body 10 to facilitate the alignment and mounting thereof relative to the head of an EDM apparatus or the like, which is shown for purposes of reference and designated as H in FIG. 7. one form of such means is illustrated, as by way of example, in FIGS. 1, 2, 3 and 7 as comprising a pair of concentrically arranged circular projections 120 and 122, which extend upwardly in stepped fashion from top face 12. Projections 120 and 122 may be formed integrally with holder body 10 and adapted for insertion within a complementary formed recess 124 provided in head H for abutting engagement therewith. Holder body 10 may be fixedly secured to head H in any suitable fashion, such as by clamps or by threaded fastener devices received for instance within threaded apertures 12a provided in top face 12. Another type of holder body alignment and mounting means is shown in FIG. 8 as being in the form of a shank 122' of rectangular cross section, which may, if desired, be provided with a through bore opening communicating with passageway 90.

The provision of upwardly opening passageway 90, and the extension thereof mentioned in connection with the construction of FIG. 8, enables the conduit means of holder body 10 to be placed in direct flow communication with a suitable source of dielectric fluid for those instances when the mounting head of EDM apparatus is formed with a supply passageway. However, not all mounting heads of commercially available EDM apparatus are provided with a suitable fluid supply passageway, and this is particularly true of apparatus of the type permitting programmable, automatic replacement of a plurality of electrodes on a common mounting head. In these prior constructions, it is necessary for each electrode to be attached to a flexible supply conduit leading to a supply manifold or alternatively, for a workman to couple/uncouple a single supply conduit to each electrode as it is placed/removed from association with a common mounting head. Therefore, it is an important feature of the present invention to provide an arrangement, wherein fluid distributor means is permanently fixed to the mounting head of an EDM machine and automatically coupled in flow communication with the holder body of the present invention as an incident to its placement in mounted association with the mounting head. Specifically, the present invention contemplates that the fluid distributor means be in the form of a fluid distributor block 126, which is suitably secured to head H by a bolt 128 or the like and provided with an internal passageway 130 having an inlet end placed in flow communication, via a suitable fitting 132, with a source of dielectric fluid and a discharge end 134 disposed for alignment with side passageway 92 of holder body 10. An O-ring or the like 136 is preferably provided on block 126 in surrounding relation to discharge end 134 for providing fluid sealing engagement of holder body side wall 18 with the distributor block. With this construction, a suitable flow control valve, would be employed to control the flow of fluid between the source and the distributor block, such that the flow fluid is automatically interrupted during an automatic electrode changing operation effected by removably placing successive holder bodies and their associated electrodes in mounted association with head H.

Although certain preferred embodiments of the present invention have been disclosed and described in detail, various changes will obviously occur to those skilled in the art, and therefore it is intended that the present invention be limited only by the scope of the appended claims.