Note: Descriptions are shown in the official language in which they were submitted.
106Z344
_ackground of the Invention
Radio frequency devices are often used in indus-
trial operations, a common example being the application of
dielectric heating to the fabrication of articles employing
a hot melt adhesive. Utilization of radio frequency energy
permits the heating of surfaces remote from the outer surface
of the article. However, the use of such radio frequency
devices may complicate the design of the apparatus due to
the care necessary in designing the power supply leads to
the load, which may be, for example, a dielectric sealer head.
While transmission lines that are somewhat flexible are
available to machine designers, the flexibility thereof is
somewhat limited, resulting in either restricted movement of
the load with respect to the power supply, or requiring
significant amounts of maintenance because of fatigue of the -
transmission lines.
While examples of non-contacting rotary coupling
members for the transmission of radio frequency power have
, ` been known, as exemplified by U.S. Patents Nos. 2,439,235,
issued on April 6, 1948 in the name of George H. Brown and
2,944,230, issued on July 5, 1960 in the name of Carl-Erik
Granqvist, we know of no such non-contacting coupling members
which permit relative linear motion between the radio
frequency load and the power supply. Such a coupler would
. . . .
1 be of advantage to a machine designer for utilization on
;? such devices as reciprocating dielectric heater elements
~i which can be arranged to follow the article, for example, a
~`~ linearly moving web, for a period of time necessary to
provide a se`al thereon and then to reverse its motion to
re-engage the web at a new location.
'~ '
.
~ 2-
.~ ,~, .
1062344
Summary of the Invention
Accordingly, the present invention provides a non-
contacting electrical coupler for connecting a linearly mov-
able radio frequency load device to a 6tationary radio
frequency power source device both having amean opereting
wavelength of ~ .
In ~ccordance with one aspect of the present
invention, the coupler comprises ~ pair of parallel first
generally tubular conductor members, each of which have an
axially-extending opening through the wall thereof. First
terminal means is provided at a first end of each of the first
conductor members for connecting each of them to opposite
sides of either the power source or the load. Means is pro- ~-
vided for electrically connecting the first conductor members
together at a distance 6ubstantially equal to ~ /4 from the
first end thereof. A pair of 6econd conductor members are
disposed one within each of the first conductor members wherein
each of the ~econd members have a length ~ubstantially equal to
/4 and are arranged for relative axial movement within the
first conductor members. Terminal means are provided at one end
of each of the second conductor members to connect them to
opposite side6 of the other of the power source or load, which
terminal members extend through the axially extending openings
through the first conductor members.
According to another aspect of the present invention,
the first conductors are disposed parallel to the direction of
the motion of the load.
..~
,
~ -3-
,,. . . . .
;, . .
1062344
In accordance with another aspect of the present
invention, the terminal means connected to the second conductor
members support the second conductor members coaxially within
the first conductor members and ~re rigidly connected to ~the
movable device.
In accordance with ~till another aspect of the
present invention, the first conductor members have a length
substantially equal to A /4 plus the distance of motion of
the second conductor members therein.
0 In accordance with yet another aspect of the present
invention, the means connecting the first conductor members to-
gether is arranged to move with the movable ~econd conductor
members ~nd the movable device, thereby substantially increasing
the amount of relative motion possible between the power supply
and the load.
~he various features of novelty which characterize
the present invention are pointed out with particularity in
the claims annexed hereto and forming part of this ~pecification. ~-
For a better understanding of the invention, its operating
advantages and the specific objects obtained by its use,
`'h .
reference 6hould be had to the accompanying drawings ~nd
descriptive matter in which a preferred embodiment of the
present invention i6 illustrated and described.
.~ . ' ' .
Brief Description of the Drawin~s
Figure 1 illustrates a first embodiment of the non-
contacting coupler of the present invention; ~ - -
Figure 2 shows a second embodiment of the non-
2 contacting electrical coupler of the present invention;
.~
, -4-
.: . -. . .. . .
106Z344
Figure 3 shows a third embodiment of the non-
contacting electrical coupler of the present invention; and
Figure 4 ~hows a view taken along line 4-4 of
Figure 3.
The present invention provides an electrical coupler
for ~onnecting a pair of radio frequency power devices for
relative linear motion therebetween without requiring wires,
brushes, or any other direct electrical contact and yet ~till
provide high transfer efficiencies. Such relatively movable
devices may be a stetionary power ~ource and a moving load,
or a stationary load, which is connected to a ~tationary power
~ource, and a moving load. It is ~nown that in quarter -
wavelength transmission lines the input impedance (Zs) i8
dependent upon the charecteristic impedance (Z0) of the
trunsmission line and the load impedance (Zr) Th(is re21ation-
~hip is expressed by the following formula: Zs = 2
From this formula it will ~e ~een that, if Z0 is a finite
value and Zr is very large in compari~on to ~Zo)2~ Zs will ~e
very lsmall. In fact, 2~ will approach 0 ohms, that is, a
~hort circuit. It will al~o be ~een that a ~mall Zr in
comparison to (zo)2 will yield a Zs that tends to approach
infinity, that is, an open circuit.
Referring now to Figure 1, two modified coaxial
,. :.~
transmission lines 10 and 12 are illustrated which comprise a
non-contacting electrical coupler in accordance with the
present invention. The transmission lines 10 and 12 comprises
first generally tubular conductor members 14 and 16, respectively,
arranged in sub~tantially parallel relationship to each other
,
-5-
. . .
. . .
10~2344
and to the direction of motion of the movable device, generally
indic~ted by arrow 18. Each of the tubular conductors, 14 and
16, has a length substantially equal to ~ /4, where ~ is the
mean operating wavelength of the devices, plus ~ length equal
to the distance of travel to be ~ccommodated by the coupler.
The two first conductor members 14 and 16 are electrically
connected together, that is, they ~re shorted, by a chorting
~ember 20 located a distance 6ubstantially equal to ~ /4
from a first end of the first conductor members 14, 16. Each
of the fir~t conductor members 14 and 16 i6 provided with
first terminal means 22 and 24, respectively, located at or
ne-r the first end thereof for electrically connecting each
of the first conductor members to opposite 6ides of one of
the electrical devices, for example, a 6tationary high
frequency power 60urce 25. The first conductor members are
provided with 610ts or openings, 26 and 28, respectively,
through the wall thereof which extend axially along the length
thereof. Two movable inner 6econd conductor members 30 ~nd 32
are disposed 6ubstantially coaxially, one within each of the
first conductor members 14 and 16. Each of the 6econd inner
conductor members has a cross-sectional form 6imilar to that
of the first, outer conductor members and has a length 6ub-
stantially equal to A/4. Each of the second conductor members
30 and 32 is provided with second terminal means 34 and 36 at
one end thereof, electrically connecting each of the second
conductor members to opposite sides of the ~econd high frequency
devic~e, for example, ~ linearly movable load 37. The 6econd
terminal means are arranged to extend through the slots 26 and
28, re ~ tively, in the first conductor members 14 and 16.
' .
-6-
' ~ ,. , ' ' ' . ,' ', .: ' '. ' ., ''' ,.,'' ' . .' '',',,,. ... . , ' '' . ' .. . ... .' ' ..
1062344
The inner, second condhctor members 30 and 32 are
supported in axially movable relationship in the first
conductors in radially 6psced, insulating relationship there-
with by the terminal members 34 and 36 which extend through
slots 26 and 28 to the linearly movable high frequency load.
The load is structurally ~upported in an insulated manner by ¦-
any co~mon mechanical arrangement. Thus, in oper~tion, as the
linearly movable load is moved in a direction parallel to
arrow 18, the inner conductor members 30 4nd 32, being physically
as well as electrically connected to the load via terminals ~4
and 36, will be moved axially within the first conductor members
14 and 16. If any additional support members are necessary for ~;
the second conductor members within the first conductor
members, they are formed of a low-loss insulator to prevent any
electrical contact between the inner conductor members and the
outer conductor members.
As described above, the first terminal members 22
and 24 connecting the outer conductor members to the power
.` ~`
~upply, and the 6econd terminal members 34 and 36 connecting
the inner, ~econd conductor members to the load, are disposed
~t the same end of the coupler. When terminals 22 and 34 ~re
closest to each other, at one limit of the axial travel, a
virtual short circuit appearsbetweenthem. The same is true
for terminals 24 and 36. Thus, the load connected to the
terminals 34 and 36 will appear substantially as if it were
connected to the terminals 22 and 24. A parasitic transmission
- line of the parallel conductor type is formed between the
first conductor members 14 and 16. The shorting stub 20,
located a distance substantially equal to ~ /4 from the - -~
,, : .
~ . ..
. .: :
-7-
~, ... ,. ,, . , . . ,. . , , . ,; . , .
-` 1062344
terminals 22 and 24 makes the parallel line effect negligible
in comparison to the load im-pedance. As the 6econd conductor
members 30 and 32 move within the first condLctor members 14
and 16, the virtual shorts from terminal 34 to the first
conductor 14, and from terminal 36 to conductor 16, move with
respect to terminals 22 and 24. This results in impedance
transformation due to the characteristics of the parasitic
transmission line. Accordingly, the amount of ~,xial movement
of the load depends, to a certain extent, upon the degree of
impedance transformation that can be tolerated. Step up
` transformation of load impedance prior to connection to the -
coupling device and/or lowering operating frequency will
reduce the affect of the parasitic line. Lower operating
frequencies will give a more constant transformation per unit
i distance than higher frequencies. Moving the terminals 22
and 24 60me distance from the first end of the first conductors
~ ,*~ , .. .
14 and 16 will tend to maximize the total travel distance
available.
A specific example of the coupler illustrated in
Figure 1 was constructed from copper tubing wherein the first
conductor members 14 and 16 had an internal diameter of 1.62
inches and a length of 34 inches. The slots 26 and 28 through
the walls of the conductor members 14 and 16 were 0.28 inches
wide. The second, inner contuctor members 30 and 32 were
formed of copper tubing having an outside diameter of 0.~0
inches ant a length of 26 inches. The operating frequency was
101 MHZ. The coupler had a usable axial travel of 9 inches.
A transfer efficiency of better than 97% was achieved for a
re6istive load range of 100 ohms to 450 ohms. With the
terminals 22 and 24 located 3 inche~ from the first end of
.,,
1062344
the first conduct~r members 14 and 16, the transfonmation
ratio varied from .98:1 to 1.3:1 for a 53 ohm load, and from
.99:1 to 1.23:1 for a 328 ohm load. This non-contacting
electrical coupler was utilized to connect a reciprocating
dielectric sealing head to a stationary power 60urce. The
6ealing head was arranged to move linearly with a moving web
while the ~ealing jaws were clamped to the web. After the
sealing cycle was completed, the jaws separated, releasing the
ealed web, and returned linearly to the 6tart position to again
clamp the web to 6tart the next 6ealing cycle. The present
non-contacting coupler device operated satisfactorily and
needed less maintenance than the flexible transmission line
previously utilized in that apparatus. Although the present ~-
coupler is intended primarily to permit linear movement of the
conductor members, a certain degree of radial movement i~also
,~ ~
3 permitted. Thus, the radial spacing of the eecond conductor
members 30 and 32 within the first conductor members 14 and 16
permit a certain, limited amount of radial movement of the
cecond conductor members therein, permitting the 6ealing ~aws
to open and close on the web. This results from the fact that ~ ~ -
it is not absolutely necessary that the second conductor
members travel on the axial centerline of the first conductor
members; in other words, the conductor members need not be
truly coaxial. This is shown by the above equation in that,
as long as the second conductor members have a length 6ub~
stantially equal to ~ /4, the impedance Z0 of the line has a
negligible effect when the load impedance Zr is large.
Thus, the non-contacting coupler conductor members
may have a configurAtion other than that of a cylindrical tube,
, ` '
;,i --9-
1062344
such as that of the second embodiment illustrated in Figure 2.
In this embodiment, elements similar to those described with
respect to Figure 1 ~re provided with the same reference
numerals with the prefix "1". In this second embodiment the
first conductor members 114 and 116 of the coupler are
constructed of 1/8" thick ~luminum channel members which have
inside dimensions of 1.5" x l.S" and a length of 35 inches.
The second, inner conductor members 130 and 132 are formed of
aluminum channel members having a thickness of 1/16", with
inner dimensions of 0.5" x 0.~" and a length of 27 inches. Ii
With this coupler a transfer efficiency of better than g4%
was achieved for resistive loads in the range of 100 ohms to
450 ohms. It will be seen that the use of the channel members
reduces the alignment problems between the first conductor
members and the ~econd conductor members when compared to those
in the first embodiment. Moreover, the "radial" vement
permitted with this embodiment is significantly increased
over that of the embodiment of Figure 1 since there is no
"top" to the first conductor members which would prevent or
limit the "radial" movement of the second conductor members
therein.
It has been found that the dimensional tolerances
of non-contacting couplers constructed in accordance with
the present invention are not very stringent. The spacing
between the first and second conductor members must be such
that arcing is prevented therebetween, and the distance
between the first and second conductor members can be as great
as 2 inches before transmission effect is lost. As previously
noted, the slots in the first conductor members may be
, .. .
10- . -
.~" -, . . , . . .. , , ,, . ~ .
106Z344
positioned about the circumference thereof other than that
shown, and need not run the entire length of the outer conductor
members. The only limitation with respect to the circumferential
placement of the axial ~lots is that they not be locsted 60
closely together that an appreciable transmission line effect
occurs between the two 6econd conductor members.
A non-contacting electrical coupler constructed in
accordance with the present invention has been utilized to
transmit 5 kw of power. Embodiments may transmit up 100 ~w
0 of power at the frequencies noted above. A practical~upper
,~ limit of frequency is approximately 1,000 MHZ. The lower
.~
operating frequency limit is determined by the 6pace ~vailable.
~he amount of linear movement possible, compared to the 1/4
1 wavelength distance, will be determined by the consistency of
;~ load impedance required. In the case where the operating
frequency is high and the linear movement is equal to 6everal
r,l quarter wavelength distances, it would be possible to locate
the connector 20 from the first end a distance equal to odd -~
multiples of the 1/4 wavelength distance. Such an application
would, without further modification, provide pulsating energy
transfer to the load with a wide range of impedance excursion.
..,
The amount of 6uch impedance excursions that can be tolerated
would determine the practicality of 6uch a device.
Another embodiment is illustrated in Figures 3 and
4 which permits the operation of a coupling device in accordance
with the present invention over extended lengths of trsvel
while minimizing, if not eliminating, the impedance excursions
noted above for travel over distances greater than 1/4 wavelength.
.~, ,,
.~; . , . . , ~
106234~
In this illustration elements similar to those illustrated in
Figure 1 are given the same reference numerals but with the
prefix "2". This embodiment permits substantially greater
axial travel than that of the devices illustrated in Figures 1
and 2. This is accomplished by substituting e moving connector
element 220 in place of the ~tationary shorting element 20 or
120 of the other embodiments. The element 220 is ~rranged to
be supported by and moved with the moving load so that the
connection bet~een the ~tationary first conductor m~mhers 214
and 216 always appears tothe moving second conductor members
230 and 232 to be spaced from the terminal connections 234 and
236 by a distance substantially equal to a quarter wavelength.
The moving connector element 220 comprises a pair
of tubular elements 240 and 242 which have cross sections
,.:,
~imilar to and ~urrounding the first and ~econd conductor
members 214 and 216. The tubular elements 240 and 242 are
disposed in spaced relationship about the first conductor
members and sre arranged for movement therealong. A compound
`~i tubular member 244 is disposed in spaced relationship about
the tubular members 240 and 242 and includes a center wall
portion 246 that extends between the adjacent tubular members.
A first end of the moving connector element 220 is formed of an
electrically conducting end plate 248 that joins the ends of the
tubular members 240 and 242 with the end of the compound
tubular member 244. The opposite end of the moving connector
element 220 is provided with a non-electrically connecting wall
member that 6upports the respective ends of the tubular members
240 and 242 and that end of the compound tubular member. The
:' , ' ' ~ ' .
1062344
moving connector element 220 is supported from the moving load
device by an insulated support 250 so that the moving connector
element is movable in spaced relation along the first conductor
members 214 and 216 along with the moving second conductor -
members 230 and 232. The moving connector element 220 has a
length substantially equal to 1/4 wavelength, the end thereof
with the conducting end plate 248 being the closest to the
second terminal means 234 and 236, connecting the second conductor
j members to the moving load, And being spaced therefrom by a
D distance ~ub~tsntially equal to 1/4 wavelength.
This results in a negligible loading from the
parasitic line no matter where the load is located relat~ve
to the terminal ~embers 222, 224. It has been found that the
parasitic transmis6ion line between the input terminal means
~ 222, 224 and the load terminal means 234, 246 will have the
`~ same effect on load voltage and feed point input impedance as
~ any normal transmission line of ~imilar construction. The
..
parasitic line is thus arranged to have an impedance equivalent
to that appearing at the load terminal means. This permit6
the greatest amount of load travel with minimal variation
of feed point input impedance and load voltage. The moving
connector element 220 functions substantially like the coupler
described in the first two embodiments. Thus, an unterminated
quarter wavelength transmission line is formed by the tubular
- elements 240 ant 242 and the stationary first conductor members
214 and 216. This results in a virtual connection, on the feed
~ide of the moving connector element 220, between the tubular
elements and the associated first conductor members 214 or 216.
'
~ -13-
1062344
The end plate 248 h~s two functions. It connect~ the
upper and lower rectangular tubular elements 240 and 242 and
it creates a short circuit between the compound tubular member
244 and the tubular elements. Ihus, the first conductor
members 214 and 216 are 6horted together. Also, the fir6t
tubular element 240 And the related portion of the compound
tubular member 244 form a quarter wav~length transmission line
which is terminated in A 6hort circuit. This ~hort is
reflected to the other(end of the line as an open circuit. ~his
0 assures open terminations for the transmission lines formed by
~i the inner tubular members and the stationary first conductor
members. Thus, the compound tubular member serves as a shield
for 6tray transmission effects. It will thus be 6een that this
embodiment extends the amount of linear movement possible.
~ While t~e embodiments described hereinabove have
i generally illustrated coupler elements wherein the fir6t,
outer contuctor members are ~tationary with the 6econd, inner
` 1 conductor members moving relative thereto, it will be appreciated
that the inner conductor members may be held atationary with
the outer conductor members moving. Moreover, it is possible
that both the inner and outer contuctor members move relative
to some fixet point ~nd with respect to each other. Further, ~ -
the connection of the fir~t conductor members to the power
60urce and the 6econd conductor members to the load can be
: .
rever~ed 60 that the first conductor members are connected
; to the load without depart~ng from the present invention.
I Still further, the movable load may be connected via the coupling
¦ element in accordance with the present invention to a second,
~ '
~ -14-
: .. . . , ,.. . . ~ -,
, , . . , . . ,; , .. ; ,.: . . . .
" . .. .. . . ~, . . . .
1062344
stationary load, which in turn is connected to a stationary
power source.
It will be understood that the first, outer
conductors are preferrably provided with insulating supports,
of a type ~nown in the art, to physically 6upport them in
operation. Also, it will be apparent to those ~killed in the
art that a balun feed connection to the first, outer conductors
will provide the most sstisfactory operation of the present
crwpler. Any type bslun connectioo msy be used.
~"
, ~ - .
:
.: .
. 1
.,-,~ :
,~1
..~
''"~! :
,' . . .
' '~ ~ ~
.~
-15-
L ' . ;,: , ~ ~ ' '
': ' ,
