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' Aug. '13, 1963
|_,
BA|§NEs
l
3,100,856
VARIABLE ELECTRICAL TRIMMER CAPACITOR
Filed March 1:5." 1961
INVEN TOR.
A TTOA’NEYS
than
1
Unitedstéf?sPate?t {0 > icev
.
2
1’ 1
7 tion. of back-lash is
‘
‘
'
'
‘
Patented Aug. 13, 19%3
accomplished Without the ‘use of
3,100,856
.
‘VARIABLE .ELECTRECAL TR?
springs.-
.
.
--,
»
‘
.
., Freeport, NY. 7 a v.A further object of the invention is to provide a
Llewellyn-T. Barnes, 1155 Atlanti trimmeratype piston capacitor which is composed of few
1 t
Filetl'Mar. 13, 1961,;Ser, No; 95,191,‘
.
.
5 Claims. . (Cl; 317F249),
parts,‘ is simple to construct and assemble, lends itself
‘~ ‘
jto mass production techniques, and at the same time is
‘ ‘My invention relates to variable electrical. capacitors
ellective to prevent rotation of the piston.
and. speci?cally to capacitors of the trimmer'tjype which’
-
4
Additional objects ‘and advantages, of the invention
are used to produce‘ precise‘ capacity‘ variations.
_
will“, become apparent duringthe course of the follow
The ‘present, invention is a continuation-input- of .my 10 ing speci?cation when taken in connection with the ac~
[.i .copending ‘application Serial‘ nogsznas, ‘?led October
‘112, 196i}; ‘for ‘Economy Piston Capaciton-
In‘
, vco'rnp-anying ‘drawings, in ‘which:
“ "
‘
' t ' ’ FIG. 1 is a longitudinal sectional view of a capacitor ~
y aforementioned United States patent applica
‘made 'ingaccordance with the invention; and,
‘non, S'erial‘No. 62,295, I‘, have disclosed a trimmer ca-'
>
‘paci‘t'or of‘ the type in which a piston" constituting a
' i
7 FIG. ,2" is atransverse section taken along line 2-2 of I.
FIG. 2.
movable electrode‘ is slidablewithin a‘cylindrical body
' I: Y3 With ‘ continuing reference to the drawings, wherein. ~
‘made of dielectric material and‘having ‘an,external.con'- ' 7 like reference numerals designate similar partathere is
' gductive coating constituting‘ the ?xed electrode‘ or‘ plate ‘ 1 shown ‘a capacitor "it? made in accordance with the
' ‘of the capacitor. The piston'hias an internally threaded ’ ' invention and having a frontjend bushing ‘12. The.
" bore. which receives the threaded end of la rotatable ad
.busliih'g'lZ is formed with a central aperture 'Mconi
justing member in such a- manner that whenthe adjust
niunicating
bushing 12 also
withhas‘
ana inner
chamfer‘ed
bore or‘tape'red
‘orchamber'
inner16,surface '
‘ ing member‘is rotated, the piston is ,rnoved, axiallyrela- '
tive tothel ‘cylinder coating, ‘thereby changing the ca
pacitance ofythe. unit. An anti back-lash mounting is
' 18‘ adjlace'nfaperture lif‘or a reason hereinafter 6X5
vplained. Bushing 12 is also provided with‘ front circum- '
' supplied ‘for. the Tadjustingjme‘mbe‘rin the nature of‘a 25’ ,fe‘renti‘al flange 26‘ from which projects a tubular portion,
spring “exerting outward pressure on’ the vadjusting mem- _ 22 of reduced, diameteriand de?ning the inner bore in.
‘ A hollow cylinder ‘24, made of a dielectricvmaterial
' ‘her-‘in such a manner asto maintain the threaded. con-x
neotion under constant tension. f
such as quartz,v glass, ‘fTitania” or the like, ‘is rigidly and,‘
concentrically attached to the‘ ‘bushing =12. A band 25
/_
.- The use of ‘a spring to provide,isui?cientitension to ~
eliminate- back-lash has been found effective
opera
30
- tion, but has also presented several practical disadvan
tages. The springs themselves are relativelyfcostly and ‘
_0f_ afconductive metal such as silver, is ?tted about the
'outersurface of cylinder .24. adjacent the rear end thereof,
and isjsecured to said cylinder. outer surface, as'by’
cementing. Asian alternative, the band may be sprayed
wonjthe cylindersurface and then ?red;
. increase ‘ the ‘over-all .manufacturing'cost. of the innit.»
Further, their tension is affected during continuousjp'use .
and" they are subject to breakageundenheavy use and I
' . The tubular'portion 22 of bushing 12 is inserted within,
> the'front open end of cylinder 24- and is secured therein
»adverse weather conditions.‘ r g
invention? to provide a . asbycementing-with the‘; end oifincylinder 24 abutting’
It‘ is an object‘ or the pre,
mimmemapacimr ‘of, the type, described in whichanalteiir " hanger-'20 and ‘chamber “l6wcornnrunioating with the in?
nate“
the adjusting
means‘, ismember
providedand
.to‘lproducejzfa
.toprev‘entlbaclc-las'h,
lbias‘ringpforce
thereby:
,on 450
uterior‘j'of?cylinder 124.
"
" Y
" "
‘
'
~
The/capacitor in also includes an ‘adjusting member
eliminating the use offsprings ‘for thisjpu'rpo’se.
Min iggtéd .generallyz'"by",reference numeral 28‘ and com- .' " ‘
In ‘accordance, with ',the -~ present invention, there {15
prisinga.cylindricaLshankQtD terminating at one end .
. in an enlargedithieaded portion 32." The other end of
i "- cylindrical
provided ’ a"body,
piston
one
(trimmer,
highv dielectric
typeficapacitor
material;having
JAnn'adeg
a ' ,shankj?ii'carries anlintegral terminalhead piece 34;. The
jjiustingTrr‘ie‘mbenfwhich. isthreadedl for, “only a small I.
’_ I ,iiendof'lthe;piston?isiattachedrtoia'iwa
apertu
en'having'asqu '
re ‘which‘l‘coa'cts with ‘a; squareprojeotion
h .
,‘IheadLpiece'134'hasilataperingiinner portion 36 which‘ is
xcornplementarygto the tapered surfacelti ot'b’ushing 12'
V-adjacent- aperture .14. a In assembly, the bushing‘ 12 can
‘slid into thejfrontendl of; hndet-Qdlyvdth.thethead
,iece. 34 of) the mounted ‘adjusting member zgpassin'g <
hrough the" bushing bore lldiuntil tapering por-tion?36
headupiecesi'nt is seated, upon-the, tapered surface 18
linder‘gfancl thereby, prevent th
’ bushing‘ 12.
4 f?tltéliioynw; 19513399361"?
conduct ebafnd.
din
l'iistitutesa?nedielectrojdie of i V
Xteriorly of’ the dielectric Wall‘ ofjcylin
rapacitorl'ir? also includes a movable elec-, _ .
y by" referencenu-meral 38., ' Elec
rider lll-talongtheiinner surface‘, ,
a.
central threaded. to
“ cylindricalgmetal piston'i4tthaving
2-, and ' alwas'her, is, madam
‘ lnbneondnctive ‘mate
?et?dbf peyote‘ “Wash? '44 is’ PrWi
quarecentraléapertureda whic
threaded
,One r, of ‘ the; objects -of4?the‘ invention 1s; to‘. piovide a
’ pistonj‘type trimmer capacitor of the character described Q i'tightly ?tted, within ‘the rear openend of cylinder" '24,’ “ and
which‘ requires‘ a minimum of ‘machiningito-“produce.
V cemented‘in place. The .endcap 48!, is providedjgv‘ith an ‘
integralinwardly-projecting postSli of square cross'lse‘c-f' 7'
y it ‘Another object- of the invention is t'oproyide aPiston-p
tion;v Post 5% is sized to ‘closely ?t within the“ square
' .ty‘pe
is extremely
trimmer economical
capacitor of-the
in manu?aoture
character described
in thatv ‘eliminawhich ' j'apert'nrevenfofwasher 44-.‘ ‘Thus','w-hile washer 44 can‘
.,
‘3,100,856 I
‘ ‘
asviewed in FIG. 1, away from the band 26, and the'area
of registry of the electrodes gradually decreases until the
slide along'post 5t), neither washer 44 nor the piston ‘40
carried thereby can rotate relative to post St) or cylinder ‘
24. Electrode 38 therefore is constrained to move longi
rear edge of the piston 40 reaches‘the forward (or vright
hand) edge of the band 26, constituting the position of
A keyhole-like slot 52 is provided in the threaded end 5 minimum capacitance. ' To permit such position to be‘
‘portion 32 of shank 30, the slot 52 permitting a'slight , reached, the washer ‘i4 is cupped or depressed at its cen- '
ter, as indicated at 74, this depressed ‘central ‘area’ provid
deformation in the length of said threaded end portion 32. _
ing clearance about the shank‘t-hreaded end portion-32 y
The end of the threaded end portion 32 normally abuts’
tudinally through cylinder 24 without rotation therein‘.
the facing end of the square post 50.
~ I
when the piston ‘it? approaches ‘its position of minimum' _
s
capacitance. Also thetorward portion of piston 40 is
The square post 5%) is provided with an internally
threaded bore 54 which is threaded in the opposite direc
'
provided with a reduced diameter, indicated at '76, which ‘ Y
the within the bushing borelld in the‘ position of minimumv
tion of the internal threaded bore 42.. , A tension screw 56
‘ is threadedly engaged in the threaded bore 54. ‘The ten- _
‘capacitance.
sion screw has a conicalor pointed, tip .58 at'the inner
end thereof facing the threaded end portion 32 of shankf
. ‘Thus, it‘is seen
'
-
'
‘
’
‘from’ the above description, theonly' '
30. The pointed tip 58 forms a hearing or pressure point
pieces
ring areofthecapacitor
threaded10portion
which 32,
require
ltension
extensive
screw._machin'-,x
56. and '
:and seats in a conical depression .60 in thefend ‘face 62' of
1 internally threaded piston 40 and square extension 570.’
The complete unit is easily assembled with a
V
thé‘thrfeaded end portion 32 of shank 30 in bearing, en
of cementing and soldering.- Thus, production costsandp'
gagement. The opposite end of the tension‘ screw’ 56 is._,
. provided {with a 'kerf or slot 64 for facilitating the rotation 20 ‘assembling costs ‘ are considerably decreased and ,the
capacitor is capable of being more economically :manu; ' '7 -.
. "orf‘thelf tension screw 56 and hence the position’itof the
' ._bearing‘58.
Thus, a screwdriver or‘s‘imilar'tool may be 1 '
> factured than was heretofore feasible.
‘Linserted through the rear open end of bore 54 until it
7
*
‘
It will be noted that the novel construction of the piston ,
The'tension‘
4t) and washer 445 permits the piston to travel'bet‘ween a ‘
screwv 56 can then be manually adjusted until thejproper 25 position of complete registry with the‘?xed electrode “or
band 26 and a position wholly out of registry with said’ '
"tension is provided against the adju‘sting'member thread
band26, while at the same timekeeping the length of the
' ed end portion 32.
'
‘
' ‘engages thekerf not tension scre'w‘Sd.
Under pressure oftension screw 56, the sections ‘of the , .
cylinder 24 to a minimum. Thus, a trimmer capacitor of . .
threaded endrporrtion 32 are pressed together, bringing
exceptionally small lengthfis provided ?or‘use withiminia
the external threading slightly out of alignment with the so) V_ture electrical units or the like.
While a preferred embodiment of the invention has \begn 7‘:
meshing internal threading’42 of piston 40, and thereby
creating a drag on this screw threading. This tensioned
I shown and described herein, it is. obvious that numerous 1 >7
drag serves to provide smooth, uniform and ?ne adjusting
movement or the piston .40, and also holds the latter in
changes, additions and omissions may be made in-such"
embodiment without departing from the spirit ‘and ‘scope
precise adjusted, position at all timesQeven whensuh
of the invention.
jected tojarring, vibration or the like, and also eliminating
back-lash and creepage. Because of the reverse thread-_
'
'1
'What I claim is:
_
.
'
_
‘
‘I
l. A trimmer capacitor comprising a hollow cylinder
v ' ing of the bore 54.-and its contained tension screw 56, and
_1 'formed of a material having a high dielectric constant, an.
because of the point contact provided by the tip-j58 of , ' adjusting member rotatably mounted in said cylinder and “ ,
said screw'56, rotation of adjusting member 28
not 40 including a shank extending vaxially‘ into the‘ interior of. ~ :
Q ‘ produce ‘a corresponding ‘rotation of tension screw‘ 56.
said ‘V-cylinder,‘ an ‘externally-threaded‘terminal portion :at '
' .> ‘Screw 56,‘ rather, .will- tend to remain immovable.
the; end'of said shank andhaving a slottherein for defoli
The forward end ofheadépiece' ‘34 projects slightly.
', outwardly from the bushing‘, apertursm and is provided
vmation. of the external ‘threading thereof, a piston elec?
trode slidable in, said cylinder; said-piston electrode having ' V
with a kerf 66 .at the outer end-thereof for the reception "
aninternally-threaded,
the threaded‘terrninal
longitudinal
portionof'
through
said shank,
borereceiv~v
means . 1 I
* ‘of a screwdriver 'or' similar‘ bladed‘ toolL‘which may be . ing
' . used to (facilitate. the rotation thereof.durings‘adjustment. 1 > ‘for. preventing rotation ofv'said piston ‘electrode within a I
' The‘ piston fit), front end'bushingfl-lzyand adjusting
V j 4 member 28‘ are made of a; conductive metal
‘ an extremely low- coe?’icient?of. thermalexpansion.
said cylinder so thati‘js'aid piston electrodeislmoved‘rlo?gi- . f‘.
‘:haS" ‘
“4
tudinally througyhsaid‘cylinderpwhén said. shank is .r'o
tated,_ and adjustable means icarrie'drby saidfjmeans'for' _
terminal postidiiv is mounted onuthe front end of bushing‘ ' preventing rotation of stride-piston‘ .elec'trodeexte
' Inland isithusfelectrically"connected-to piste-r1110‘ through; ' longitudinally throughv the bore. of js'aid-piston'electrode ' "
‘‘ andengagingsaid terminal portio'n ofes‘a'ild shank ‘for? '
- ?the‘conductive jadjustingmember28. A ring or rings'70"
V ‘ '
and‘inteigralterminalpost 72 are secured to the band-'26 ‘it? forming‘ 'saidterminal portion otsaid shank’iso'that s d1:- "
on cylinder 24 by solderingjtojprovide electrical ‘contact 3,55 i‘terniinalportion of saidshankllis maintainedjn‘ tight "
norm, engagement ‘with :said‘ ‘piston electr'ojd' "
‘therewith.
stitutes the ?xed electrode‘of the capacitor'l’ilgfifThei band‘. 7: .- ' »
26 and electrode 38 are separated‘by'rthe body ofrcylin'lder '
‘ i- 7 2,4, which has arhigh dielectric constant.
capacitance‘ :1 '
_, _~ ‘of the unitis changed rotating’fadjustingTscrewfi28, th‘ _ '
‘bushing vlfriction‘allyinter?t ‘ :rwith‘iand closin" off
endgo?said cylinderrseid
- “rotation being translated S into longitudinal movementv ff
1 i‘ piston’ 4p0ico-nstituting movable'electrode r?liltrelativell't't)
Iformedofal'material having‘ \a high?fldielectr'i‘e ‘constant,
,
,
.
. ‘ \ an; adjusting j member extending frotatably ‘through: _ said
',- ?xed band ‘26. 'I’The movable "electrode 38 receives cits. ‘4 * ‘bushing‘aperture; ‘said
6 charge; through. terminal! 68,‘ Jbushing? :12 and“ adjusting
.
lure.“communicating‘ With- the?nterior ‘or said' 'cylin 11,,
, 65
‘
?iusring'member
having.V a‘i'headI
llocatedfcutside ‘said bushin‘gjashank
‘
carried bysa
' '
’ member‘lass The engaging lt'aper'in “surfaces-.718 of the 1 ' ' ‘and :ext ,n'd' g;‘longitudinally-rand, centrallyaint
bushing-‘1,2; and ' surfaces-‘376 of'gthef headpiece .34 provide
7 I“good/electrical
adjustingmember
contact
28,;Iunder
hetweenjthebushing
the .biasing force‘12of andthe
tension"
screws
In theposrtion of the capacitor shown-in FIG. ‘1, the
j g . piston 'd'?is in registry with the ?xed electro-delband‘lzd, .
y. ., constituting a position f-of maximum capacitance. when.
p {' ytheli’shank?ll isrotate-dby'nianual' turning of the ‘head-l
terior :bf» said cylinder, and “Jan.externally?hreaded. te‘ri
minale'p'or'tion ‘at theIe'nd-of- said'ishankfa cylindrical ‘
‘ton electrode‘ slidahlein' said cylinder jandhavin'g ac ‘
tral‘intiernallyrtlireaded through-‘bore receiving thegthre‘aded
terminal portloii of said sha'nlg'said piston carlryingaite
vminal member having a ‘non-circular. .aper'tureinjcom .
‘ munlcationfwith said threaded bore, and an endlca'pljs'ee
. >
cured‘ .to the other end of, said cylinder .qoppositei saidv ' "
' pie'cef34,‘the piston 49; travelsdn a'right-ihand‘ direction 75,}bushing». and having a longitudinally-extending post ‘of i' I
3,100,856
5
non-circular cross-section, said post slidably receiving the
non-circular aperture of said terminal member and ex
post ?tting slidably Within said non-circular aperture ‘for
preventing rotation of said piston electrode within said
cylinder so that said piston electrode is moved longitudi
nally through said cylinder When said shank is rotated,
tending through the threaded bore of said piston and in
abutting relationship with said terminal portion, said post
preventing rotation of said piston electrode within said 5 said post having an internally threaded bore threaded in
cylinder so that said piston electrode is moved longi
the opposite direction to said bore in said piston electrode,
tudinally through said cylinder when said shank is ro
a tension screw secured in said bore in said post and
tated.
'
engaging said terminal portion, said terminal portion hav
3. A trimmer capacitor comprising a hollow cylinder
ing a key-hole slot therein so that force exerted by said
formed of a material having a highv dielectric constant, a 10 tension screw on said terminal portion deforms said ter-'
bushing frictionally inter?tting with and closing oif one
minal portion to maintain said terminal portion in tight
end of said cylinder, said ibushing‘having a through aper
frictional engagement in said bore in said piston electrode.
ture communicating with the interior of said cylinder,
5. A trimmer capacitor comprising a hollow cylinder
an adjusting member extending rotatably through said
formed of a material having a high dielectric constant, a
bushing aperture, said adjusting member having a head 15 bushing frictionally inter?tting with and closing off one
located outside said bushing, a shank carried by said head
end oflsaiid cylinder, said bushing having a through aper
and extendingforwardly into the interior of said cylinder,
ture communicating with the interior of said cylinder,
,and an externally-threaded terminal portion at the for
an adjusting member extending rotatably through said
ward end of said shank, a cylindrical piston electrode
bushing aperture, said adjusting member having a head
slidable in said cylinder and having an internally-threaded 20 located outside said bushing, a shank carried by said
through bore receiving the threaded terminal portion of
head and extending iinto the interior of said cylinder, and
said shank, said piston carrying at its forward end a
an externally-threaded terminal portion at the end of said
member having a non-circular aperture in communica
shank, a cylindrical piston electrode slidab'le in said
tion with‘ said threaded ‘bore, and an end cap secured
cylinder and having an internally-threaded bore receiv
to the forward end of said cylinder opposite said bush 25 ing the threaded terminal portion of said shank, said pis
ing and having a post of non-circular cross-section ex
, ton carrying a member having a non-circular aperture
tending longitudinally through-said threaded bore toward
in communication With said threaded bore, and an end
the threaded terminal portion of said shank, said post ?t
cap secured to the other end of said cylinder opposite
ting slidably within said non-circular aperture and pre
said bushing and having a longitudinally-extending post
venting rotation of said piston electrode within said cyl 30 of non-circular cross-section, said post ?tting slidably
inder so that said piston electrode is moved longitudinally
within said non-circular aperture and preventing rota
through said cylinder when said shank is rotated, the
tion of said piston electrode Within said cylinder so that
terminal portion of said shank being slotted for deforma
said piston electrode'is moved longitudinally through
tion thereof, and adjustable screw means carried by said
said cylinder when said shank is rotated, said post having
post engaging said terminal portion of said shank for de 35 an internally threaded bore threaded in the opposite di
forming said terminal portion of said shank so thatsaid
terminal portion of said shank is maintained in tight fric
' tional engagement with the internally'threaded bore of
said piston electrode.
rection to said bore in said piston electrode, a tension
screw secured in said bore in said post and engaging said
terminal portion, said terminal portion having a key-hole
slot therein so that force exerted by said tension screw on
4, A capacitor comprising a hollow cylinder, an adjust 4.0 said terminal portion deforms said terminal portion to
ing member rotatably mounted in said cylinder, said ad
maintain said terminal portion in tight frictional engage
justing member having an externally-threaded terminal
ment in said bore in said piston electrode.
portion disposed in said cylinder, a cylindrical piston elec
References Cited in'the ?le of this patent
trode sllidable in said cylinder and having an internally
threaded bore receiving said terminal portion, a member
UNITED STATES PATENTS
having a non-circular aperture, said member being ?xed
2,059,816
Schwarzhaupt __________ __ Nov. 3, 1936
to said piston with said aperture being in communication
FOREIGN PATENTS
with said bore, an end cap secured to said cylinder, said
end cap having a post of a non-circular cross-section, said _
743,842
Germanyv ______________ __ Jan. 4, 1944
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