US 2472370 A
Description (OCR text may contain errors)
June 7, 1949. D ND 2,472,370
ELECTRODE FOR HIGH-FREQUENCY HEATING OF INSULATION PREFORMS Filed Jan. 8, 1945 SOURCE OF HIGH FREQUENCY CURRENT.
SOURCE OF 7 HIGH FREQUENCY 4,
Patented June 7, 1949 EnncTRoDE FOR HIGH-FREQUENCY HEAT- ING OF=INSULATIONTREFOBMS has en Di ru ma d ke W a siego t Gu e -Hammen. In M lw ukee W S-l a c otnoliation of Delaware ApplicationlJanuary 8, 1945; Serial: No. $71,778
This invention relates, to improvements. in electrode a r ieh q e y-he i e o cy i ers, of; i bstan alln co stan l emeter compose of dieleett a m e ial. n re part ar iq eatins: herm p s c: nd; os i ne m nee u uc i rm- AL; primary, object of: the invention is to provide cooperating; high frequency electrodes. ada ed; toms s bs an ia l o m a i o he entire o n: n ula f or srnuplqf nre nrm o c ind ic l orskm- Arnothenobject is to provide a nor-mallystationary; eleot node off such lform= as ;to insureproper p ition n of-= ns lat o nrsi l o l n ri on l s rs ape wh n osi d e sen n t ser la nnshin h e Anqther -an-d more specific object isto provide a trough-shaped; supporting electrode which. not n nstab ize -:1 the. c dr c d skr hap nrei-ormswhem seated-fids w se h re resverse; relationship thereto butalso serves to im-. prove current distribution through; such prefoprns; thus overcoming: the mechanical and-electrical; disadvant es lfi t l t e h used for such purpose.
Another ohiect isetolprovidelfor use ore-an upper electrode Q i ith tnverte r u h-s e r, offlat; o m; w heut; sacri i n f: the a r tages attendant upon use; of: a. troug-h shaped; we :ot' upportinaele ro e;
Anothcn object isto provide.- f or use of cornnlementar-yl. ever ar an es l tr des: so veni a e o ae e m a e h eb we nl reterm r f r s Qt irsula or n ransverse ess s i n he b eid-ele t es i t; v: s r oun lati e a e tipn 0ft t ne phera iar goirthe e o msi w th o s qu ntsubstantiallm uniform heatingof; all portions of: eeh ierm- Qthertqbiects and; ad antag s of en on ih reinaiter, nn
The nanyiee it w nes lustr te certain embodiments of theinventio n which will now be described; it. being understood. that the invention is. susceptible oi embodiment, in other. forms without. departing from. the scope vof the apte desi ims- In the drawings, Eigure 1;, is, a sideelevational, iewlot a pa r iu er andlpw rhi hi t uency, electrodes. ofapprojiimately. semi-circular form in transverse cross section to accommodate h rsh we n. n mor p e ences, o rdi ctr o ma er al; Q eim le ewer in t a sv s a s; seamen-l he. we -electrode s vinaraselst biliz: msupmstige he prsisz ms.
Fig. 2,; is a sectional view on the line 2--2 of Fig. 3 illustrates a modified form of my invention wherein theupper electrode is of the usual flatf-orm, and the lower or supporting electrode isvin the: form of atrough; the same com.- prising a pairot longitudinally straight, flat sidesconverging at;arelatively Wide angle toward each ither-land Eigsiis a sectional view on the line 4-4 of In the'art; oitransfer-molding of thermoplastic or' thermosetting insulating materials, of the Bakelite type for instance; it has heretofore been proposed gto pmvide preformed slugs or disks ofsuch material; and toheat such slugs between a, pair of high igtequency electrodes to render the sarn e qf; the desired degree of plasticity for use in the molding; machine; especially Where a transfer molding-machine is employed.
In practice suchpref-orms are generally in the form; ofr ound disks or cylinders; because that isthe most convenient form of the pieces for use in themolding machines; and also because the die cavities; for preform-ing suchtablets are most economically made in that shape. The useo-i a pair of flat; hig-hfrequency electrodes heretofore usedfor; heating and plasticizingsuch preforms has :not been satisfactoryt asiswellknownby those skilled in this art, although there is no difficulty in insuring a o onstant unlike-diameter of all of such diskshaped prefiorms, there isaninherent likelihood. that suchr preforrns will difier from each other in thickness. on axial length. Therefore, even though a plurality of: such disk-shaped preforms are. placed} individually upon a fiat lower sup porting electrode there will likely be substantial difienence, in the; distances between the upper. ends thereof and an upper electrode of the flat type. When such. preformsare placed end, to end flatvvise in groups of two or more, to form p les, eat d fletwis p n t at pport ng electrode the aforementioned condition may be considerably aggravated. That is to say, there may be relatively wide difierences in the air gaps between the tops ofthe several piles of preforms and the flat upper electrode, with resultant uneven or'-unequal heating-- of the preforms in the various piles. Moreover, the operation of so arrangingtthe-lpreforms inpilesupon the fiat lower or supporting. electrode was time consuming, and
the. operation of gathering: the piles of heated slugs from. such. Sw m-ting electrode. and droppingtheniainto theiwellzof thetransferl-mold ng:
machine was likewise slow; whereas speed of operation in such a system is very desirable to provide for attainment of the best results.
As aforeindicated, although there are inherent differences in the heights of the preforms, due to the differences in the amounts of material em bodying the same, variations in molding pressure, presence of molding fins, etc., such preforms will all be of like diameter, and I accordingly utilize this physical characteristic of such preforms to advantage.
As shown in Figs. 1 and 2 the lower or supporting electrode iii, composed of a suitable metal is of approximately semicircular form in transverse cross section, the same preferably having curved or downwardly curled edges ii and H2 at opposite longitudinal sides thereof. The upper electrode 63 of like metal may be of exactly the same and dimensions as the electrode and is arranged in reverse relationship to the latter so as to be complementary thereto for reception thereloetween of a group of cylindrical preforms arranged end to end relationship, or with their flat ends adjacent to or contacting with each other. The upwardly extending curled or curved edges of electrode 53 are designated by numerals H3 and 55, respectively.
Also as indicated in Figs. 1 and 2 the troughshaped lower electrode i is preferably arranged lengthwise in a horizontal plane, to facilitate depositing of the insulation preforms is thereinto, either singly or in a cylindrical group. Said preforms when so deposited within the troughshaped electrode Iii are mechanically stabilized in a central position transversely thereof, as best illustrated in Fig. 2; the same being seated against the central. portion of the trough, and being spaced 2. gradually increasing distance from the trough on opposite sides of the center of the latter. The upper electrode is is preferably movable upwardly, or upwardly and laterally, a sufficient distance to facilitate depositing of the preforms within electrode i0, either manually or otherwise. Thereafter electrode I3 is lowered to a predetermined operative position, usually in contact with the preform or preforms, as shown in Figs. 1 and 2. By this means high frequency current is supplied and penetrates the preforms i B in a large number of paths extending substantially throughout the periphery thereof,
as indicated by the imaginary dotted lines I! and H3 in Fig. 2. As a consequence, substantially the entire transverse or cross sectional area of the preforms will be subjected to a like heating effect of the high frequency current supplied to electrodes ill and it, as indicated diagrammatically at 99 in Fig. 1; it being understood that electrodes ll] and i3 act as the plates of a condenser, so that with the arrangement illustrated substantially uniform heating of the entire mass of the preforms is insured. In practice care is exercised to insure that the adjacent pairs of curved edges ll, i5 and 52, i l of electrodes it and i3 are maintained spaced from each other a sufficient distance to avoid any possibility of arcing between the electrodes or short-circuiting thereof around the preforms.
After the preforms i6 have thus been subjected to a predetermined desired or required amount of heat treatment, the supply of high frequency current is interrupted in any suitable manner, whereupon the upper electrode is is'preferably raised to permit ready and speedy removal of the preforms, either manual or otherwise, for
feeding thereof into the well of a transfer molding machine or the like (not shown).
In the modification illustrated in Figs. 3 and 4, the lower or supporting electrode 20 is also of trough-shape in transverse cross section; the same having a pair of longitudinally extending straight, flat portions arranged at an obtuse angle to each other, as best illustrated in Fig. 4. This form of supporting electrode is mechanically equivalent to the electrode in aforedescribed, in respect of centering and stabilization of the insulation preforms i it. Also as indicated in dotted lines at El in Fig. 4, imaginary paths 2| of the high frequency current from electrode 20 to the preforms it are electrically and functionally quite similar to those indicated at I8 in Fig. 2.
The upper electrode 22 in Figs. 3 and 4 may be of the usual flat form, as shown; the same c0- operating with electrode 20, in respect of the preforms it, to afford substantially complete and equalized heating of the entire cross sectional area of the preforms. In practice such cooperation involves proper spacing of the upper electrode 22 from the preforms to insure the uniform heating afo "mentioned. The most closely adjacent portions of electrodes ill and 722 are maintained separated a suflicient distance for reasons set forth in connection with Figs. 1 and 2. The edges of upper electrode 22 are preferably bent upwardly, and the edges of lower electrode 20 are bent downwardly, as shown, to assist in insuring against arcing therebetween. Electrodes 20 and 22 may be supplied with high frequency current from a suitable source it, as aforedescribed.
The upper electrode 22 is movable, as described in connection with the device of Figs. 1 and 2, to facilitate insertion of the preforms into and removal thereof from the electrode 20.
The stationary lower electrodes in and 20 in the respective devices are preferably attached to suitable supporting members, fragments of which are shown at 23 and 2 3 whereas the respective upper electrodes are provided with adjustable supporting and lifting means, fragments of which are shown at 25 and 26.
Although, as illustrated herein, I prefer to pro vide for horizontal positioning of the pairs of electrodes iii, i3 and 2E], 22 to facilitate depositing of the preforms, supporting the same for heat treatment, and thereafter removing the same; it is to be understood that certain electrical and/or functional advantages of my invention may be obtained by vertical mounting of the pairs of electrodes. This is especially true with respect to vertical mounting of the semicircular electrodes it and it of Figs. 1 and 2; in which case the vertical charge or pile of preforms might be separately supported in exactly centered relationship to both electrodes of the pair. Such centering of the preforms might be conveniently provided by positioning the same within a tube of suitable glass or ceramic composition.
1. In combination, a trough-shaped sheet metal electrode for use in high frequency heating of cylindrical preforms of thermosetting dielectric molding material, means for mounting said electrode horizontally with the trough thereof opening upwardly whereby the same is adapted to act direct y a centering support for the preforms, the side edges of said electrode being equally spaced throughout the length thereof a distance greater than the diameter of the preforms to effect substantial equalization of the heating effect upon the latter of'high frequency current passed between the same and said electrode, a second electrode overlying the horizontal supporting trough formed by said first electrode throughout the length of the latter, and the longitudinal edges of said last mentioned electrode being alined with and spaced from those of the first mentioned electrode a sufiicient distance to avoid any possibility of arcing between the electrodes or short-circuiting thereof around the preforms.
2. In combination, a pair of like trough-shaped sheet metal electrodes for use in high frequency heating of cylindrical preforms of thermosetting dielectric molding material, said electrodes being of approximately semicircular form in transverse cross section, means for mounting one of said electrodes with the open side thereof facing upwardly in a horizontal plane to form a directly supporting receptacle, means for mounting the other electrode in overlying relationship to the first electrode, to complementally accommodate therebetween a plurality of the cylindrical preforms arranged in end to end relationship, the longitudinal edges of each electrode being spaced apart a distance substantially greater than the diameter of the preforms, said edges of the respective electrodes being alined with each other and spaced apart a sufficient distance to avoid any possibility of arcing between the electrodes when in use, and associated means for effecting movement of at least one of said electrodes with respect to the other.
3. In combination, a trough-shaped sheet metal electrode for use in high frequency heating of cylindrical preforms of thermosetting dielectric molding material, means for mounting said electrode horizontally with the trough thereof opening upwardly to form a supporting receptacle, the side edges of said electrode being equally spaced throughout the length thereof a distance greater than the diameter of the preforms to effect substantial equalization of the heating ef- 6 feet upon the latter of high frequency current passed between the same and said electrode, a second electrode overlying the horizontal trough formed by said first electrode throughout the length of the latter, the longitudinal edges of said electrodes being vertically alined with each other, the longitudinal edges of said second mentioned electrode being spaced from those of the first mentioned electrode a sufiicient distance to avoid any possibility of arcing between the electrodes or short-circuiting thereof around the preforms, atleast one of said electrodes being movable with respect to the other, said first mentioned electrode being of a relatively wide V-shape in transverse cross section, and said second mentioned electrode being fiat.
LESTER D. DRUGMAND.
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS Number Name Date 2,179,261 Keller Nov. 7, 1939 2,231,457 Stephen Feb. 11, 1941 2,288,268 Crandell June 30, 1942 2,303,983 Brown Dec. 1, 1942 2,304,958 Rouy Dec. 15, 1942 2,306,105 Grave et al Dec. 22, 1942 2,347,324 Johnson Apr. 25, 1944 2,390,572 DeBrabander Dec. 11, 1945 2,396,004 Gilbert Mar. 5, 1946 OTHER REFERENCES Timbi and Bush Principles of Electrical Engineering, page 481, published 1923.
Journal of Applied Physics, Oct. 1943, page 546, vol. 14, No. 10.
Electronics, March 1944, page 230.
Modern Plastics, June 1944, page 111.