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Патент USA US3087296

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April 30, 1963
Original Filed March 5, 1959
3 Sheets-Sheet 1
Aprll 30, 1963
Original Filed March 5, 1959
5 Sheets-Sheet 2
' April 30, 1963
w. .1. HELWIG
Original Filed March 5, 1959
3 Sheets-Sheet 5
Mía/@WJ f/W/a
United States Patent Ü
of a bell jar type of enclosure within which the envelope
parts of a tube are placed. While this type of processing
avoids the pressure differential characteristic of Sealex
machines in that the entire space within the bell jar en
closure is evacuated, thus equalizing the pressure on the
inner and outer surfaces of the envelope parts, it is subject
William J. Helwig, Kearny, NJ., assignor to Radio Cor
Original application Mar. 5, 1959, Ser. No. 800,357. Di
vided and this application Mar. 30, 1960, Ser. No.
Patented Apr. 30, 1963
poration of America, a corporation of Delaware
9 Claims. (Cl. 53-9)
4to a discontinuity of a‘n even more serious kind than that
associated with Sealex machines. Consequently, the bell
jar type of processing Ádevice does not lend itself to effi
10 cient mass production of electron tubes.
Accordingly, it «is Kan object of the invention to pro
vide an improved method and apparatus :for vacuum
and/ or heat processing workpieces in a continuous flow
This invention relates to an appara-tus for and method
of processing articles, s-uch as electron tubes, and in par
ticular is concerned with an improved method of and
apparatus for heat treating and/or vacuum processing
work-pieces fed in a continuous flow.
This application is -a division of my copending applica
`It is a further purpose to provide an evacuating and
sealing apparatus which includes a structure defining a
continuous flow path 4therethrough for articles, such as
electron tube workpieces to' be processed, and wherein
tion, Serial No. 800,357, filed March 5, 1959, now Patent
Num-ber 3,057,1'130.
the flow path has an ambient for avoiding objectionable
While the invention will be described in an environment
of a softened seal region.
having. utility in evacuating and sealing electron tubes, 20 suck-'in
Another .object is to provide a method of and apparatus
it is not limited to such utility. Indeed, an apparatus and
for first evacuating a space defined by loosely pos-i-tioned
method incorporating the invention has utility in a wide
parts arid then sealing .the par-ts, in an operation
range of applications involving the vacuum and/ or heat
treatment of articles and materials in a continuous flow
4One type of apparatus employed on a relatively large
scale for processing electron tubes to provide an evacuated
and sealed envelope is known as a Sealex machine. This
involving continuous travel of the parts in a predeter
mined path, for increasing the efficiency and speed of .tube
A further aim is to provide means defining a predeter
mined path `of Itravel of tube envelope parts, wherein the
path is characterized by a convex temperature profile ex
type of machine includes two turrets, on one of which 30
tending Ifrom one end of the path to the other, for pro
a stern wafer is sealed to a bulb of an electron tube, and
viding relatively low temperature at the path ends to fa
on the other of which the envelope `formed by the stem
cilitate loading and unloading parts at such ends, and a
and bulb is evacuated through an exhaust tubulation, and
relatively high temperature at a region intermediate the
the tubulation is pinched ofi’.
This type of apparatus is characterized by several ob 35 ends of the path, for sealing said parts together;
Another purpose is to provide means defining a path
jectiona'ble features. One of such objectionable features
having a convex temperature gradient and a concave
resides in a discontinuity in the processing. Such dis
gas pressure gradien-t therealong, for facilitating a con
continuity arises as a consequence of the need to trans
tinuous evacuating and sealing operation.
fer 'workpieces from one to the other of the aforemen
A further object is to provide an evacuating and sealing
tioned two turrets. Such transfer usually is effected man 40
apparatus having a structure including a rectilinear tube
ually and involves a time interval, during which the work
and heating and evacuating means distributed along the
pieces are removed from machine control. Not only does
length thereof to provide a temperature an-d degree of
this time interval represent an undesirable time delay in
evacuation within the tube having a gradient rising from
tube manufacture, lbut it is accompanied by risks of tube
damage incidental to tube handling and iby the expense 45 one end of .the tube to -an intermediate portion thereof,
and falling from said intermediate portion to the other
of operator attendance.
end of the tube, for facilitating not only a continuous
In addition to the aforementioned discontinuity in op
processing of workpieces carried through said tube, from
eration, Sealex machines are accompanied by the disad
one end thereof to the other, .but also the loading and un
vantage that the evacuating operation is effected under
conditions wherein the outer wall of the tube envelope 50 loading of the workpieces at the tube ends.
A further object is to provide an evacuating and sealing
undergoing evacuation 4is subjected to atmospheric pres
apparatus having path-determining means responsive in
sure. Since the tube envelope is usually heated during
enlargement ,to increasing temperatures to provide in~
the evacuating operation by heating means directed to
creased access of said parts to an evacuating means at rela
driving out occluded gases from the tube elements, the
glass of the envelope is raised to a temperature that may 55 tively high temperatures.
Another purpose is to provide a rectilinear tubular
be high enough to set strains therein, in response to
evacuating oven and a workpiece carrier made of such
stresses produced by the pressure differential on the outer
materials that -the inner diameter of said oven- is en
and inner walls of the envelope. Such strains Imay pro-`
larged at a region >of maximum temperature while the
duce cracks in the tube envelope, thereby destroying fur
ther yutility of the tube. Furthermore, the pressure dif 60 carrier is substantially free from enlargement transversely
of the tube, to facilitate evacuation of a space defined by
ferential referred to produces objectionable suck~in of the
said carrier in the aforementioned region. Another pur
portion of the exhaust tubulation softened for pinch-off.
poseV is to provide an evacuating system lwherein two or
In .the evacuation and sealing ofthe envelopes of cer
more evacuating means overlap in a region where the low
tain tube types provided with exhaust tubulations, the fore
going objectionable features of Sealex machines, in re 65 est gas pressure is desired.
Another aim of »the invention is to provideV an evacuat
spect of discontinuity and pressure differential, have been
ing and sealing apparatus having a structure defining a
’toleratedV in View of the relatively high speed of process
rectilinear path therethrough, and including Work carriers
ing .that such machines provide.- However, cer-tain other
adapted to close effectively from the ambient atmosphere,
tube types having no exhaust tubulations in the envelopes
thereofH and requiring sealing -of- envelope parts after 70 regions of said path, for facilitating the evacuation of
electron ytube envelope workpieces carried through the
evacuation, cannot be processed by Sealex machines.
F or processing such other tube'types, use has been made
aforementioned regions.
One embodiment of the invention selected for illustra
tive purposes only, zcomprises a structure including a
vertically supported metal tube having a predetermined
inner diameter and a plurality of aperture groups spaced
axially thereof. The tube is embraced at regions includ
ing at least one aperture group by duct means communi
cating with an evacuating means. The two aperture
groups adjacent to the opposite ends of the metal tube
are each associated with an evacuating means having a
capacity of gas conductance that is appreciable in rela
tion to the gas conductance through open ends of the
tube to the two aperture groups aforementioned. Several
groups of apertures in an intermediate portion of the
tube are connected to a third evacuating means of greater
Work carriers of the type referred to may be loaded
continuously in tandem relation into the lower end of the
metal tube, either manually or mechanically, to assure a
predetermined rate of travel of previously loaded car
riers through the tube. This rate is related to the capaci
ties of the evacuating means and heating means, and
must be sufliciently slow to assure desired evacuation of
envelope parts on the carriers and desired sealing of the
parts after evacuation.
Carriers with evacuated and sealed electron tubes
«emerging from the upper end of the metal tube may be
4removed manually or mechanically.
Further features and advantages of the invention will
become apparent as the present description of an embodi
eñiciency than the ñrst named evacuating means. Thus, 15 ment thereof proceeds,
the latter evacuating means may comprise mechanical
In the drawing, to which reference is now made for a
vacuum pumps, while the third means may constitute oil
consideration of an embodiment of the invention, by way
diffusion pumps backed up by mechanical pumps.
of example,
To further increase the efficiency of the evacuation of
FIG. 1 is an enlarged view in elevation, partly broken
the intermediate portion of the tube in the embodiment 20 away, of envelope workpieces that may be processed by
referred to, a first chamber embracing several groups of
an apparatus according to the invention;
apertures is connected to an oil diffusion pump backed
FIG. 2 is a partly sectional schematic elevational view
up by a mechanical pump, while a second chamber within
of an apparatus embodying the invention;
the ñrst chamber embraces at least one group of aper
FIG. 3 is an enlarged fragmentary view, partly in sec
tures of said several groups and is connected to an inde 25 tion, of the loading and retaining mechanism employed in
pendent oil diffusion pump backed up by a mechanical
association with the apparatus shown in FIG. 2;
pump. In this way, the gas pressure differential within
and outside of the inner chamber is reduced for increased
eñiciency of evacuation of the portion of the tube em
FIG. 4 is an enlarged sectional View in elevation of a
work carrier and bafñe used in the operation of the ap
paratus shown in FIG. 2;
braced by the inner chamber.
FIG. 5 is an enlarged sectional view in elevation of the
The foregoing combination of evacuating means pro
structure of a portion of the apparatus depicted in FIG. 2;
vides a gas pressure gradient in the metal tube which is
FIG. 6 is an enlarged sectional view taken in the gen
concave in profile, that is, the gas pressure in the portion
eral direction of arrow A shown in FIG. 5;
of the tube embraced by the aforementioned inner charn
FIG. 7 is a perspective structural view of the apparatus
ber is lowest and increases toward both ends of the tube. 35 shown schematically in FIG. 2 with certain parts, shown
In the embraced portion of the tube, therefore, maximum
evacuation of an envelope defined by workpieces takes
in FIG. 2, omitted in the intere-sts of clarity;
FIG. 8 is an enlarged sectional view taken along the
line 8_8' of FIG. 5;
FIG. 9 is a fragmentary perspective view of a portion
For heating the interior of the metal tube -to provide 40 of the radiant heating means;
predetermined heat zones for degassing, cathode activa
FIG. 10 is a schematic view of an actuating system that
tion and sealing, a system is provided having a moderate
may be employed in connection with the loading mecha
heating capacity in relation to the portion of the metal
nism shown in FIG. 3;
tube embraced by the outer evacuating chamber afore
FIG. 1l shows an enlarged fragmentary elevation of a
mentioned, and excluding the portion embraced by the 45 portion of the processing tube of the apparatus shown in
inner chamber, and an appreciably high heating capacity
FIGS. 2, 5 and 7, and depicts one of several similar sets
adjacent to the last named tube portion. The inner cham
of openings in the processing tube; and
ber is spaced along the axis of the metal tube from both
FIG. l2 shows an enlarged fragmentary elevation of
ends of the outer chamber, and the outer chamber is dis
the processing tube and depicts another set of openings
posed intermediate the tube ends. In this way, the tem 50 therein.
perature gradient, from one end of the metal tube to the
The workpieces lto be processed by the apparatus of
other, is substantially convex in profile, so that an inter
the invention may comprise a metal bulb 10 made of steel,
mediate portion of the tube is at sealing temperature and
for example, and an electron tube mount including a stem
the ends of the tube are relatively cool for convenient
12, made of a ceramic, such as Forsterite, having
loading and unloading of the workpieces.
55 lead wires 14 extending therethrough, as shown in FIG. l.
To reduce gas conductance from the ends of the tube
A ring 16 of brazing material made of an alloy, such as
to the several pumping regions, a novel carrier for work
Nioro solder, known in the trade, is disposed adjacent to
pieces is provided having one or more spaced wafers of
the periphery of the wafer 12, and the end of the bulb
a diameter to provide a relatively small clearance iit with
1i), closed by loosely positioning the wafer :12 thereon,
the inner wall of the metal tube adjacent to the cooler 60 The periphery of the wafer 12 may have a coating 18
end portions thereof. In this way, when the metal tube
thereon, made of molybdenum, for example.
is fully »occupied by work carriers, interior portions along
A processing of the described workpieces by the appara
the length of the tube are appreciably blocked against
tus, according to the invention, involves evacuating the
passage of gas admitted from the external atmosphere.
envelope loosely defined by the wafer :12 and the bulb 110,
An important feature of the invention resides in appro 65 degassing metal components of the electron tube shown
priate selection of materials for the metal tube and work
place, and accordingly, the parts are sealed in this portion
to preserve the aforementioned maximum evacuation.
in FIG. 1, activating a cathode, -not shown, inconporated
carrier wafers, so that the metal tube may have an ap
in the electron tube aforementioned, and sealing the pe
preciable coetîicient of expansion causing its inner diam
riphery of the wafer 12 to the inner wall of the bulb 10.
eter to enlarge at the hotter intermediate portion thereof,
while the wafers do not enlarge appreciably. Thus, the 70 When the bulb 10 and wafer `12 are in the loosely as
sembled position shown in FIG. 1, suñ'icient communica
annular spacing between the inner wall of the tube and
-tion between the space deñned by the bulb and Wafer, and
the periphery of -a wafer is enlarged at the intermediate
the exterior is provided, so that when the parts referred
portion of the tube where evacuation is most eñîcient.
to are placed in an ambient of reduced gas pressure, the
This enlarged space facilitates evacuation of envelope
gas pressure within the space aforementioned is reduced
workpieces supported on the work carriers.
correspondingly. Furthermore, in the position shown, a
heating of »the solderk ringV 16 to its melting point tern
perature, will cause the melted solder to flow downwardly
between-the periphery of the wafer `12 >and Ithe inner wall
of the bulb le, to provide a hermetic seal therebetween»
when the solder is cooled to hardness.
For accomplishing the foregoing» vacuum processing
and heat treatment of the electrontube vvorkpieces` de-scribed, an apparatus is provided includinga tube 20deiining a path of travel for the workpieces fromone end
ofA air under pressure, not shown, through a three-way
valve 54. The valve S4 includes a valve member 56. hav
ing-a T-shapedchannel `58 and shown in a position wher -
in the channel provides communication between duct ‘52
and a duct @communicating with the atmosphere. Rota
tion of the valve member 56 in a counterclockwise di
rection, asviewed in FIG. l0, and lthrough an- arc of 90°,
will permit communication only between duct 52 and>
a duct 62. connected to the aforementioned source of air
of the tube to the other in a continuous flow, as shown in 10 under
To` aetuate thevalve member 56 successively to the ltwo
FIGS. 2, 5 and 7. The tube 20 is approximately ten
feet long. The apparatus includes `a plurali-tyof com
bined carriers and baffles 22, one of whichisshownina
FIG. 4. Each carrier includes-a cylindrical portion 24,
positions referred to, -a solenoid 64 includes a piston >66
pivotally linked toV an arm `68v connected- to the valve
member. The solenoid has la structure-for normally dis
posing the piston 66 in extended position. In this posi
having openings 26 and extending from one` sideof a 15 tion the upper `surface of the .piston head 44 (FIG. 3)
bafñe disc 28 defining two flanges or baffles 30 and 31,
is flush with the upper» surface of .table 46'. However,
and a supporting recess 32, on which the electronV tubey
when the solenoid is-connected- to a source of A.C. elec-The
workpieces shown in FIG. l' are adapted to rest;
trical energy, it retracts piston `66, ‘therebyV actuating thev
cylindrical portion 24 surrounds thezworkpieces, and the
valve member~56-to a position wherein the channel there
bañle disc 2S provides `a cavity 33 into which the lead 20
in communicates with- ducts 52 and k62 and the source
wires 14 of workpieces supported in a lower carrier-may.r
of air under pressure.l This causes the piston 42 and
extend. A plurality of carriers are adapted to be received‘t
the piston head 44 to rise through table 461 for pushing a
in tube 2i) in tandem relation.
work carrier loaded" on the upper surface of the piston
The carriers 4are preferably made ofv a materialwhich 25. head,_up into‘tube 20 :and toL a position wherein the ñiange
exhibits a small heat retaining property. Thus, if. the
v30 onsthe carrier is above pin34- for‘preventing return
specific heat of the carriers is relatively small, the car->
downward movement ofthe loaded carrierV onv subsequent
riers will cool rapidly and assume substantially roonr
retraction of the` piston 42~and head 44.
temperature when unloaded Ifrom tube 20. When the
For controlling the feed of work carriers into; the tube
composition of. `the carriers 22 is cold rolled steel and`
20, at a, rate- of.y say one carrier per minute, »a switching
their structure is as shown in FIG. 4, their heat retain
arrangement (FIG. 10)' is-> provided. across». the A.C.
ing property is sufñciently small'to permit convenient
power line serving the solenoid 64. This. switchingv ar
unloading thereof, after passage through theheat zonesV
rangement includes a switch 7-0, normally open, and
to be described at a rate to be specified herein.
adaptedto be closediby aca-m 72 having a switch clos
Work carriers 22 may. be fed successively into the 35A
ing. lobe “74. The cam is rotated` counterclockwise, as
lower open end of tube 20, shown in FIG. 3,- either
viewed in FIG. l0, on an axis 76 by a shaft 78 engaging
manually or mechanically. The rate of feed should be
the cam connected-to a motor. 80Ltrhrough» a gear box Í82,
such as to assure suflicient time Áfor several processing-ele
to. provide a rate of" one rotation through 360° per'
ments disposed outside of and extending along the-tube,
to operate on the workpieces. In one example, to be de 40 minute.
The lower end portion 40 of. processing-tube 20 has a
scribed, this rate is one carrier per minute.
of its Wall removed, as shown at 84, 85 (FIG. 3).
In the example shown -in FIGS. 2, 5 and 7, the process
The removed portion includes an arc of at- least 180° to
ing tube 20 is disposed in vertical position. Conse
quently, the combined weight of the carriers previouslyy
allow. a carrier~22 to be inserted` therein in coaxial and
operating relation with respect to theA tube> 20. The in
loaded into the tube will rest on the lowermost carrier. 45 serting operation is facilitated by> the-fact that the upper
To support the column of carriers in tube 20, between
surface ofïcylinderhead 44 is flush with the upper sur
loading operations, a stop structure is provided, ‘asA shown
in FIG. 3, comprising a pin 34 urged by a spring'36 into
distended position through the wall of tube 20~and into
faceoh table 46lbetween» intermittent loading movements
ofY the piston head. This facility in the inserting opera
tion renders the use ofy manual means feasible. However,
the path of travel of carriers therein. A head 3-8 on the 50
mechancial` means, not shown, may be used for inserting
pin determines its maximum distended position. The
work carriers into the lower end of the processing tube.
portion of the pin 34 extending into the tube 20* is bev,
For a reason tha-t will become apparent, the cylinder
eled on its lower side, so that »a forceful extension of a.
4Sàispreferably supported by table 46, by means of suit
carrier 22 into the lower open end 40 ofthe tube will
ablebrackets 86, `88,v as shown in FIGS. 3 and l0. As
cause the flange 30 on the carrier to bear against the bev 55 has previously beenmentioned, the table, in turn, is sup
elled side of pin 34, thereby causing the pin to retract
portingly fixed to the lower end' of the tube 20. As «a
against spring 36 and permitting the flange 30 to pass
consequence, axial» expansions ofthe tube 20.will not
upwardly beyond lthe pin. As soon as the flange 30 clears
effect the-flush position of the piston head' 44 with re
the pin 34, the pin is free 4to spring out'to distended
spect to the upper surface of table «46, which is impor
position, for engaging the underside of flange 30 and re 60 tant in facilitating loading of carriers into the tube.
straining falling movement lat the carrier 22.
As the work carriers 22 are raised in -tube 2t), the
While it is feasible to feed work carriers manually into
uppermost carrier'in the column will emerge from the
the lower end portion `40 of the processing tube 20 at the
upper end of the tube. The-emerging work carrier» may
required rate, it is preferable to utilize mechanical means
be removed either manually or by mechanical means,
for this purpose, in view of the appreciable weight of the 65 not shown.
column of work carriers wit-hin tube 20, and which re
For suitably vacuum treating, the workpiece in the
quires lifting manually in a manual feed. A suitable
work carriers 22,` as the carrierstravel through Áthe proc.
mechanical system 37 I(FIG. 2) for feeding carriers into
essing tube 20, suitable means are provided for produc
the lower end of tube 2,0 is shown in FIGS. 3 and l0.
ing a gas pressure gradient within tube 20 thatis con
The system may include a piston 42 having an enlarged 70
cave in profile along thek tube. That is to say, the gas
head portion 44 extending through an opening in Ia table
pressure at the- open. ends of the tube 20 is atmospheric
46 fixed as by welding to the lower end of processing tube
and decreases toward an intermediate portion of the
Ztl. 'The piston 42 extends into a pneumatic cylinder 48
tube 20, at which the pressure is sufficiently reduced for
having an upper duct 50 communicating with the atmos
phere, and a lower duct 52 communicating with a source 75 providing a desired ambient having a degree of evacua
tion required in the envelopes of the electron tube work*
p The nieans for providing the aforementioned gradient
in gas pressure comprises a system for producing Zones
surrounding axially spaced portions of the tube 20, each
having a desired pressure to produce -the gradient ’re
ferrea te. The wan of the 'tube 2e is provided with @pasings at each z_one f_o'r equalizing theßgas pressure
each Zone and the interior of the adjacent tube portion.
to, which is approximately 0.0002 mm. of mercury, the
tank 110 is connected to an oil diffusion pump 124
backed up by a mechanical pump 126, by means of a
high conductance duct 128, as shown in FIG. 2. The oil
diffusion pump has a capacity of 500 liters per second,
and may be of a commercially available type known by
the designation CEC-MCSOGB The mechanical back
up pump used, has a capacity of sixty-live cubic feet per
minute, _and islkrìown commercially by the designation
Adjacent the intermediate portion of the tuber20, two 10 Kinney KÜHAGS.
overlapping zones are provided for maximum evacuation
of this portion.
Reference to FIGS, 2 and 5 reveals one specific form
that the aforementioned pressure reducing means may
For providing communication between the low gas
pressure ambient ‘produced in tank 110, _and the interior
of the- tube‘ portion embraced by the tank, a plurality of
sets of openings are provided in the wall of tube 20.
As shown in FIG. 2, two mechanical vacuum 15 One of two sets of openings shown schematically at 129,
pumps 90, 92 are connected to fittings 94, 96 embracing
130 in FIG. 2, and of the type shown in FIG. 11 and
portions of the tube 20 adjacent to its ends and deñning
comprising twenty-eight openings each, is disposed in
chambers or tanks 98, 100, respectively. The vacuum
the wall of each portion of the tube 20 located within
pumps referred to may be of the type known commer
the space defined by each of bellows 112, 114. Each
cially as Kinney KDH65. Two sets of openings 102, 20 set is spaced about thirty-five inches from the adjacent
104 in the wall of tube 20 provide communication be
end of tube 20. An additional set of openings 131, also
tween the chambers 98, 100, respectively, and the in
similar to the set shown, »in FIG. 11, is spaced inwardly
terior of the adjacent portions of the tube.
of tank 110 from opening set 129, a distance of about one
Each set of openings 102, 104 comprises twenty-eight
foot. Further sets of openings 132, each comprising four
openings’106 extending along the tube 20 a distance of 25 openings spaced around tube 20, as shown in FIG. 12,
about one and one-half inches, as shown in FIG. 11.
each having a diameter of one quarter inch, are dis
Each opening is about one quarter inch in diameter, and
tributed between opening sets 130 and 131. The open
each set includes seven annular arrays of four openings
ing sets 132 are spaced about one and one-half inches
each, the openings in each array being equidistantly
from each other and from sets 130, 131 axially of tube
spaced around the tube 20. Adjacent arrays are stag 30 20
gered circumferentially of the tube 20 to permit a group
This arrangement of openings in the -wall of tube 20
ing of the twenty-eight openings in a one and one-half
assures a reasonably constant pressure within tank 110
inch length of the tube without appreciably weakening
of about 0.0002 mm. of mercury, even though workpieces
the tube, and for desired air ñow conductance between
located within the region of the tube 20 encompassed by
the chambers 98, 100 and the interior of the adjacent 35 the tank 110, may be releasing considerable quantities of
portions of tube 20.
Pumps 90, 92 produce a degree of evacuation of cham
However, the gas pressure in tank 110, and the interior
bers 98 and 100, and the interior of adjacent portions
portions of tube 20 to which communication is afforded
of the tube 20, that is dependent on several factors.
opening sets 129, 130, 131 and 132 aforementioned,
These factors constitute the capacity of the pumps, the 40 by
is not suñ‘iciently low to provide a desired evacuation of
air ñow conductance between the ends of the tube 20 and
workpieces being processed. Therefore, a second tank
through the sets of openings 102, 104 referred to, and
133 is disposed lwithin tank 110, and embraces a length
the degree of blockage to such ñow presented by the
of tube 20 having an axial extent of about one foot.
work carriers 22.
The second tank, or inner vacuum chamber 133 is semi~
With the capacity `of the aforementioned pumps 45 cylindrical in shape and includes a dat side 134 remov
known, the air dow conductance and the degree of block
ably iixed to the semi-cylindrical portion 136. The iiat
age to now may be controlled to provide a gas pressure
side referred to is ñxedly supported on an air duct 138,
in chambers 98, 100 and the adjacent interior regions of
which extends through and is hermetically sealed to the
the tube 20, that is less than 1/0 mm. of mercury, and
wall of the larger tank 110.
about 6 mm. of mercury. Thus, it has been found by 50
For evacuating the interior of the vacuum chamber 133
applicant that a desired control of air ilow conductance
t0 a gas pressure of about 0.00001 mm. of mercury, the
is realized when tube 20 is provided with an inner diam
duct 138 is connected to an oil diffusion pump 140
eter of 1.055 inches, when the portions of tube 20 having
backed up by a mechanical pump 142. The oil diiîusion
the sets of openings 102, 104 are spaced approximately
140 has a capacity of three hundred liters per
twenty inches from the adjacent ends of the tube, and 55 pump
and is of a type known commercially by the desig
when the clearance between the inner wall of the tube
CEC-MCF3‘00. The mechanical 'back-up pump
and the periphery of ñange 20 on Work carriers iilling the
is of a type available commercially under the designation
tube is about 0.003 inch when cold. The gas pressure
Kinney KS13.
referred to is, of course, also dependent on the gas pres
To provide communication ‘between the vacuum cham
sure in the portion of the tube 20 intermediate the cham 60
ber 133 and the interior of the portion of tube 20 which
bers 98, 100:
it surrounds, two sets of perforations '1414, 146 of the
For reducing the gas pressure in a relatively long inter
type shown in FIG. 11 are provided through the wall of
mediate portion of tube 20, a relatively large diameter
the tube portion referred to. These two( sets of perfora
chamber or tank 110 is provided which embraces the in
termediate portion aforementioned, as shown in FIGS. 2 65 tions are spaced about nine inches from each other,
and 5. The tank 110 is cylindrical in shape and about
axially of tube 20. Intermediate perforation sets 144,
four feet long and has a diameter of about one foot.
146, are provided three sets of openings 148 of the type
End portions of the tank are hermetically sealed around
shown in FIG. 12. The opening sets 148 are spaced
the tube 20 by means of bellows 112, 114. The tank
about one and one-half inches `from each other axially
is supported by a bracket 116 resting on four legs, three 70 of tube 20. These tive sets of openings in the tube por
of which 118, 120 and 122, are shown in FIG. 7. The
tion embraced by the inner vacuum chamber 133 eii`ec~
tank 110 serves the two functions of providing a low gas
tively eliminate any appreciable pressure differential be
pressure ambient about the aforementioned intermediate
tween the vacuum chamber and the space within the
portion of tube 20, and of supporting -tube 20.
tube portion referred to. Thus, the pressure in this space
For providing the low gas pressure ambient referred 75
is maintained reasonably constant at 0.00001 mm. of mer
cury, even though workpieces processed in thespacef
evolve an appreciable quantity of gas.
It will be appreciated trom thek foregoing that-»the-`
pressure diñerential between the interior of tanks 1101
and 133 is appreciable. To preserve this pressure dif»
assuresv that ».theworkpieces are graduallyv raised. to a seal->
ingltemperature through a. gradient at.;whichï-outgassing.
and cathode activationß `priorxio sealing, >and
which gradually-is reducedltolroom: temperature toavoid
ferential and yet allow expansiveA movements between the
inner tank 133 and the tube* 20, the inner tankîis'pro
vided with sleeves 150,152; which are hermetically sealed
to end‘portions of tank-133 and embrace the tube 20-?
in‘snug and> yet movable engagements. To this end the 101
clearance between the sleeves 150,11‘527and theV tube 20`
is about 0.003 inch radially.
It will be appreciated further yfrom theY foregoing ’that-v
the' gas lpressure Zones in chambers 983100, 110ïand 133
communicating withl the interior of the tube`20g"producev
a gas pressure gradient within tube- 20"that is conc-ave
in profile along’ the tube; Thus, at'the" ends of `the tube,A
the gas pressure is'atmospheric. From the' ends ofthe
tube, regions of progressively reduced gas pressure are
provided, until at the inter-mediate'portionf ofthe tube
embraced by vacuum chamber 133, a ¿gas pressure of
about 0.00001 mm. of mercury is realized. Thispres-v
sure gradient is obtained without closing the*v endslof `the
adapted ` to. produce a temperatureV gradient along thev
tube »201that-is: substantially’. convex in profile. This
objectionable. >strains inl ' the ' workpieces.A
The heating- system`- referred toA includes radiantl heat
producing structuresy 176,1 177 î spacedalong the tube 204
within tank 110, and a radio lfrequency heating structureV
17 8i'î positioned between thev - radiantrï heating-structures
176', 177'.I Eachîwoffheat-radiating structurescornprises;
two semi-cylindric-ally»«insulatingmembers 180;; 182 rma-de.
of'an»insulatingfrnateriah such asAlundum4 asshown.
ind-716895,A 8f-andiß9.-` The »insulating-»members -‘180',. 182.l
have`Ã> inwardly ~extendin g ribs 184,' defining; a .plurality ofelongated recesses 186 extending longitudinally ofitu-be
205? Avk wireà 188‘ made of a high electrical resistance
material, such'as Nichi-ome, is disposed in the recesses.
Th'ecend‘s ‘ of f the resistance kwire 188` in: heating4 struct-ure
176 are connected toca suitablesource-ofëelectrical power,
not shown,~ throughï leads 190; 192“,v andithe wire 188
in-"heatin'g structure» 177 ‘ï is/‘lalso connected ’ to .a >suitable
source of-electricalfpower‘- through leads l1194,' 196.
tube 20. While the workcarriers 22- eiiî‘ect partial clo
Eachï' of the- radiantheatingA strluctures~1»76,- 177, also
sure of the end portions of the tube, suñicient clearance' 25 includes: two concentric and radially spaced'iheatk re».
between the' sides ofthe carriers and the inner wallV of
the tube is found necessary’ for »free travel ofthe-work'
carriers through the tube. This clearance,~ Vwhile expos-`v
ing the interior of the tube'20 to atmospheric pressure, is
insufficient, according to the invention, to preventV the
flectingcyl-inders~198', 200>rnadeëof a-highly heat're
-iiecting‘mater-ial, suchl as stainless-steel;
The temperature produced-Ã wit-hi-n‘ tube 20l ‘by the
radiant heatingstructureslfîú, 177`A energizedjby azsixty
cycle"v commercial current,L is about 800°
high degree of evacuation'secured in an intermediate
portion of the tube.
As has been indicated previously herein,‘ the tank 110
peratureappearsina region'relativelyy close to the ends
tube 20. The tank 110 is well suited to serve a support
178 surrounding-'a portion offtub’e 20'intermediate the
ofthe inner vacuum chamber;133rf-andïdecreases Vtowards
the’ remote 'ends‘oflthe #heating structures aforementionedî
not only serves to produce a’ zone of desired low‘ gas
This gradient is* produced; partly' as a'consequence of
pressure, but also provides support -for the processing 35 heat ygenerated -` byn the radio frequency heating - structure
function, since it is ruggedly supported on’ bracket 116,'
radiant’ heatingl structures 17-6‘, 17 7 i
as previously described,
The radio frequency-heating structure 178 »corn-prises a
The tube 20 is supported at end portions of tank 110ïby 40 tubular coil`202,l made Aof‘an electrically conductive ma
means ofthe bellows 112, 114 previously referred to.
terial, such as copper, embracinga portionl of tube 20,
Thebellows include sleeves 160, 162'which fixedly en-l
including opening sets"1'44,'~ 146 and 148 `rin the» tubefwall,
gage the outer surface of the t be 20. The corrugated
in‘suitable‘spacedïrelation-to the tube. The endsoftthe
cylindrical bellows bodies 164, 166 `are fixed at on‘e
coil 2,02 pass through theiiat side 134 of the vacuum
end thereof, las yby ‘brazing or welding, to the peripheries
chamber 1313, and through'the‘side’wall oftank 110, by
of sleeves 160, 162. The other ends of the cylindrical
means of -radio frequency energy'feed-throughvconnec
bellows are fixed suitably to edges definingopenings in
tiorr`204, shown‘in‘FIGS. 5 and 6. This »feed-through
the end »walls of tank 110, as bybrazing or welding. v The
connection,l as shown in FIG. 6, includes-coaxial ducts
bellows bodies may be -made `of'a material, such as 'stain-l
206", 208, made of electrically conductive material, such
less steel, and the thickness/of the side walls of the
as copper and‘supportedby; a body> of- compressible in
bodies 164, 166 may be from twenty to’ thirty rnil-s, if 50 sulating material ' 210; The » material 210' '~ is A compressed
the bellows alone are relied upon to support the tank 110.
in the annular space between ducts 206ïand» a plug
'In additionto supporting the tank 110', the 'bellows
212A of insulating'rnaterial, ñxed tothe body 214» defining
112, 114 exert-a tensile `force on the portion of tube 20
duct 206, by two screwsA 216; The feed-through connec
extendingV therebetween. This tension isV desirable t0
tor referredto, is hermetically sealedthrough the walls
prevent buckling or other deformation of'tube 20l in re
ofthe tanks 110 and 133‘by'engagements involving con
sponse to relatively high processing temperatures.
tacts between the tanks‘and the'outer duct member 206.
if desired, the suppo-rting function of the bellows 112,
This duct'mernberv is'operatediat RF ground, not'only» to
114l may 'be supplemented by an additionalV structure.
permit direct contact with the tanks 110î and ~173, but to
This additional structure includes three~armed spiders
168, 1.70 iixedly clamped around. portions of tube 20
spaced from the -bellows referred to, Compression
springs 172, 1.73 bear against the outer `surfaces of the
avoid'ob'jectionable reactance effects with the tanks afore
Inner duct 208 is connected to an RF source-217’having
frequency of ab'o‘ut‘fourV hundred kilbcycles and a power
end walls of tank 110 and the arms of the two spiders
aforementioned. The springs are guided by rods 174,
175 which are'freely movable through the »spider arms.
lf this additional support andtensioning structure is used,
the material of the bellows bodies may have a reduced
thickness of ten mils, for example.
In addition to providing an evacuated »ambient for
evacuating the enclosurefformed by envelope workpieces,
it is also desirable to heat- the workpieces` iirst to dçgas
the material of the workpieces and activate a. cathode
included within the envelope workpieces, and iinally. to
seal the envelope workpieces to preserve the evacuated
output-of about’two kilowatts;
The coaxial ducts` 2,06k and 208, andthe coil 202 are
hollow, toallow' a cooling' fluid from a source 2_»17`to
liow therethrough.
It is desirable that the` magnetic iiux produced by the
coil 202 penetrate to the interior of the adjacent region
_of processing tube 20, To' this end, desirable flux corn
munication to the interior of the tubev 20 is provided, not
only by opening sets 144', 146 and' 14S-in the tube wall,
but also as a consequenceof the'non-magnetic material
of" which the tubes is' made, andëthe-«thinness ofthe tube
Thus; the tube’2'0l is made of a non-magnetic ma
space therein. To this end a heating system is provided 75
terial, such as an alloy known in the trade as Inconel,
connected to the several zones along the tube Ztl, to pro
vide an indication of the gas pressures therein, and should
be examined before and during the operation of the ap
paratus, to assure that the gas pressures comply with the
specifications set forth in the foregoing.
and the wall thickness of the tube is about 0.035 inch.
This composition of tube 20, the thinness of the wall
thereof, and the openings 144, 146 and 148, allow the
RF fiux produced by coil 202 to extend into the interior
of tube 20, and through openings 26 in the work carriers
therein, for heating the workpieces by RF energy induced
portant that no workpieces remain in the tube r20.
spaced heat shields 220, 222 are disposed in spaced rela
of the apparatus, to allow all carriers having workpieces
When operation of the apparatus is stopped, it is irn
therein. The RF coil is adap-ted to produce an ambient
is because such remaining workpieces will be only partially
in which the workpieces are raised to a temperature of
processed on resumed operation of the apparatus. The
about 950° C.
10 effects of initial processing of workpieces remaining in
To confine the heat produced by coil 202 to a region
the tube after stoppage of the apparatus will be lost. To
relatively close to the tube 20 and remote from the walls
meet this problem, it is desirable to load a sufficient num
of the vacuum chamber 1‘33, two concentric and radially
ber of empty carriers 22 into tube 20 prior to stoppage
tion around the coil 202. The shields referred to are 15 therein, to be unloaded before operation of the apparatus
made of a material having a high heat reflecting property,
is stopped. This expedient is also of advantage, in that
such as stainless steel.
the tube 20 will be full of work carriers, when operation
It is preferable to employ an RF coil for heating the
is resumed, for improved efficiency of operation, as afore
ambient of maximum evacuation, since the coil includes
a relatively small mass that is more readily degassed than 20
the radiant heating structures before referred to.
The material of the tube 20 and the composition of the
work carrier 22 are such as to permit appreciable radial
What is claimed is:
l. Method of vacuum processing a workpiece compris
ing passing said workpiece through a tube having an open
loading end and at least two apertures in the wall thereof
expansion of the tube 20 at the hottest region thereof, at
spaced along said tube and from said loading end, produc
which maxim-um evacuation of the workpieces is desired, 25 ing a first space of relatively low gas pressure around a
while the carrier is free from appreciable radial expansion.
length of said tube having said two apertures, and pro
This desirable result is obtained when the tube 20 is
ducing a second space of yet lower gas pressure withinI
made of Inconel, as previously mentioned, and when the
said first space and around only a portion of said length
carrier is made of cold rolled steel.
having one of said apertures remote from said open end,
The unequal expansions of the tube 20 and the carrier 30 whereby the gas pressure differential inside and outside of
22, referred to, due to the difference of coefficients of
said second space is relatively small for efficient evacua
expansion of the materials used in tube 20 and the work
tion of said tube portion.
carrier 42.2, enlarge the space between the inner wall of
2. Method of vacuum treating a workpiece comprising
tube 20 and the peripheries of the flanges 30, 3‘1 of the
placing the workpiece in a carrier having one coefficient
carrier 22. This is desirable in that it reduces resistance 35 of expansion and deñning a workpiece retaining space,
to conduction of gas from a region between two carriers
transporting said carrier through a tubular member hav
when such region is between two sets of openings in the
ing a different coefficient of expansion from said one co
tube wall. This reduction in flow resistance contributes
efficient of expansion in a path having regions of decreas
to increased efficiency of the evacuating means at the
ing gas pressures, and successively increasing the spacing
region of the tube 20 where maximum efficiency is desired. 40 between said carrier and said tubular member as said
At such regions of maximum efficiency the work receiv
carrier traverses said regions.
ing space may be considered to be defined in part by the
3. Method of vacuum treating a workpiece comprising
|wall of the carrier and in part by the wall of tube 20.
transporting said workpiece in a predetermined direction
For example, the wall of the tube 20 complements the
through regions of decreasing gas pressures in a carrier
wall of the carrier at the regions of openings 26 thus 45 having a workpiece receiving space defined by a wall,
fully enclosing the space receiving the workpiece.
However, the increase in the radial spacing produced
moving said carrier in one direction in a transporting op
between the inner wall of the tube 20 and the carrier 22
places a burden on the flanges 30, 31 to prevent tilting of
the carriers in the tube. This burden is successfully met
by the axial displacement of the two ñanges referred to.
through a distance inversely related to the magnitude of
eration, said regions being defined by walls and moving
said last walls in a direction normal to said one direction
said gas pressure for efficient evacuation of said space.
4. Method of evacuating a predetermined first region
communicating with and surrounded by a second region,
described, is that it avoids suck-in of the sealing ring 16
comprising reducing the gas pressure in said second region
when heated to melting temperature. This advantage
including said first region to a predetermined value, and
occurs from the fact that the Nioro solder ring 16 is' 55 further reducing the gas pressure in said first region while
raised to melting temperature only in the region of tube
preserving the gas pressure in said second region at said
20 encompassed by the vacuum chamber 133». The ring
predetermined value.
An important advantage of the processing apparatus
is cooled to hardness while in the portion of tube 20Á sur
rounded by the radiant heating structure 176, which is a
5. Method of vacuum treating a workpiece comprising
moving said workpiece through a path having an environ
region surrounded by tank '110, and in which the degree 60 ment of successively spaced regions of decreasing gas
of evacuation is sufficiently high to avoid suck-in of the
pressure, and increasing the exposure of said workpiece
solder material prior to its hardening.
to said environment as said workpiece moves through said
It is preferable to commence operation of the apparatus
regions of decreasing gas pressure.
with the tube full of carriers 22, preferably empty of
6. Method of joining in a seal, adjacent portions of
workpieces. The presence of carriers throughout the tube 65 envelope parts having a softening response to a predeter
will result in a partial closure of end portions of the tube
mined temperature, said method comprising transporting
to the atmosphere and improve efficiency of operation.
said envelope parts in loosely assembled envelope relation
Before the first carrier with a workpiece is loaded,
in a first path having a heat gradient from room tempera
however, it is desirable to assure that the several zones
ture to said predetermined temperature, then transporting
along the tube 20 are heated to a specified temperature 70 said envelope parts in said relation in a second path con
pointed out previously herein. This determination is
made by inspecting the several thermocouples 224, shown
stituting a continuation of said first path and having said
predetermined temperature distributed substantially uni
formly therealong, whereby said adjacent portions are
in FIG. 7, and extending from the several heat zones
along the tube 20 within tanks 110> and 133, to the ex
softened and joined in a seal, and maintaining substantial
terior of tank 110. Suitable gauges, not shown, are also 75 ly the entire of said second path in an ambient of sub
stantially uniform evacuation, for preserving said seal
from a harmful pressure differential while said adjacent
portions are at sealing softness.
7. Method of evacuating and sealing electron tube work
pieces, comprising continuously feeding said work-pieces in
tandem relation in a predetermined path, reducing the gas
pressure in the ambient of said path to provide a concave
pressure gradient along said path wherein the ends of said
temperature, said temperature gradient and said pressure
gradient being so related that said seal is progressively
hardened to prevent migration of the seal region in re
sponse to an increasing pressure differential between said
space and said second ambient produced by increasing
gas pressure in said second ambient.
9. The method of evacuating and sealing electron tube
workpieces, comprising the steps of continuously feeding
said workpieces in succession along a predetermined path,
path are at atmospheric pressure and an intermediate
reducing the gas pressure from atmospheric pressure in
portion of said path is at a desired reduced gas pressure 10 regions along said path to a region along said path of
for evacuating said workpieces and while in communica
minimum gas pressure, and increasing the gas pressure
tion with said ends, and increasing the temperature in
along said path from said minimum to atmospheric pres
said ambient to provide a convex temperature gradient
sure, applying heat to said workpiece along said path and
along said path wherein the ends of said -path are at sub
increasing said heat in steps from room temperature to a
stantially room temperature and said intermediate portion 15 maximum temperature at the point of minimum gas pres
is at a temperature for sealing said workpieces, whereby
sure for sealing said workpiece after evacuation thereof
said workpieces are evacuated and sealed in a continuous
and thereafter decreasing the temperature in steps along
said path to room temperature.
8. Method of joining in a seal, adjacent portions of
envelope parts having a softening response to a predeter 20
References Cited in the file of this patent
mined high temperature and a hardening response to a
predetermined low temperature, said method comprising
moving said envelope parts with said portions in loosely
adjacent relation in a iirst path having an evacuated arn
bient at said high temperature, for evacuating a space 25
defined by said parts and joining said parts in a soft seal,
and then moving said joined parts in a second path extend
ing from said first path and in a second ambient having
an increasing gas pressure gradient and a temperature
gradient decreasing from said high temperature to said low 30
Walker et al ___________ __ May 1, 1934
Williams _____________ _- Feb. 29, 1944
Ray _________________ __ July 31, 1945
Ropp et al ____________ __ May 16, 1950
Berch ________________ __ Nov. 7, 1950
-Johnson et al ___________ __ Dec. 5, 1950
Hensgen ______________ __Feb. 5, 1957
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