Note: Descriptions are shown in the official language in which they were submitted.
~~~
47~48
--1--
TAPE RECORDER HAVING MAGNETICALLY
CONTROLLED TAPE TENSIONING
BACKGROUND O~ TH~'INVENTION
Fie'Id'o'f't'he'Invention:
~ his invention relates to tape recorders having
tape transport assemblies for driving a recording tape past
a record head and between two cartridge reels, and more
particular:ly to such recorders includlng load survey mag-
netic tape recorders having both magnetic brake and magnetic
clutch'arrangements for maintainlng controlled and substan-
tially constant tape tensions.
Description of the Prior Art:
The present invention is closely~related and is an
improvement of a load survey type o~ magnetic tape recorder
dlsclosed and claimed in U.S. Pat. No. 3~602~458, assigned
to the assignee of this invention. The tape recorder is in-
: tended for substantially contlnuous use in varying environ-
mental condltions requiring highly reliable and rugged con-
struction ~eatures. The tape transport assembly o~ the
prior recorder utilizes a mechanical ~r~ction producing
arrangement for providing a predetermined drag or retarding
force on a take-up pulley assembly that receives the supply
reel of a removable tape cartridge. The drag maintains a
predetermined tension in the recording tape as lt is pulled
- from the supply reel by a capstan assembly~of the recorder.
- The capstan is driven directly ~rom a constant speed drive
motor. A take~up pulley assembly engages the take-up reel
of the'cartridge and is drlven by a slipping spring belt
which,' in turn, is driven by the capstan assembly. Sllppage
betwe'en the sprlng belt and the' take-up pulley assembly
47~488
--2--
occurs to maintain a proper tape speed between the capstan
and the take'-up reel as the tape is fed there~o. WhIle the
a~orementioned recorder has been highly reliable and depend-
able in extended service und.er sometimes di~ferent environ-
mental conditions, reduction of the mechanical and frictional
between the retarding and driving coupling o~ the supply
pulley' and take-up pulley assemblies iæ desirable. The
associated drag cord and spring belt drive tend to be some
limitation to the li~e of the recorder and require maintenance
10 and cleaning o~ dirt and debris between the frictional .
''; engaging parts. Thus, rotational drag at the supply pulley
assembly is desired to be better isolated-~rom a stationary
retardation producing member and.the drivlng torque to the
take-up pulley assembly iB de~ired ~o be transmitted acros~ : :
a more maintenance-~ree clutch inkerface. ~ .
In U.S. PatO No. 3,636,277, a video tape recorder
requires a rotating magnetic head which has a rotation
synchronized to the tape speed by a eddy current brake and
hysteresis coupling arrangement. Further eddy current brake
and hysteresis coupling arrangement~ are described ~or the
capstan drive and guide rollers. In U.S. Pat. No. 3,967,790,
a tape cartridge drive i~ disclosed hâving a capstan drive
including a magnetic clutch which, ln turn, is coupled by
gears to a take-up reel spindle. I~ U.S. Pat. No. 3,809,336,
. a tape transport is described for bi-directional tape ~eed
and take-up. The transport includes.a separate pair o~
clutche's an~ a separate magnetic.coupling, interconnectlng
- each'of two tape spools and a drive motor. Symmetrical
operation allows the spools to be'interchanged as take-up
and supply spools operated at hi~h velocitles and subJect to
.. ~
--3--
periodic stopping and starting. An air gap space in each
magnetic coupling is exposed to small debrls and magnetic
particles capable o~ accumulating therein to alter the
torque and speed characteristics between the input and
output o~ the coupllngs. U.S. Pat. No. 3,584,250 discloses
a ~ilm pro~ec'tor take-up reel a~sembly rather than a.tape
recorder having a capstan tape drlve arrangement. The take-
: ,.~ . . .
up reel assembly includes a.magnetlc drlve coupling between
a drive motor and the take-up reel. A cyllndrical cage
carries' annular permanent magnets and a magnetically permeable
ring axially spaced from the permanent magnets. The ring i5
; ~ixed to a drive shaft of the take~up reel BO that the motor
torque is transmitted across a magnetic air gap spaclng o~
the coupling. The magnekic coupllng air gap ls ad~ustable
to ad~ust the maxlmum load transmitted by'.the coupllng.
. Upon fllm rewinding, the magnetic gap coupllng provldes
magnetic breaking as fllm ls fed Or~ of the take-up spool.
The present invention'is dlrected to an lmproved
tape drive arrangement ~or a unidirectional slow.speed and
20 continuously operating magnetic.tape recorder having a ..
magnetic brake at a supply spindle assembly and a magnetic
clutch at the take up spindle assem~ly to provide reliable
and consistent operation, and for controlling the.supply and
take~up tape.tenslons and speeds wherein the magnetic olutch
and brake arrangements.lnclude relatively mQvable parts
including a magnetized part and~a permeable magnetic part
separated by a protected non-magnet.ic gap space ~o prevent
undesirea acc'umulations of.foreign ma~erial altering desired
- rel'ati,~e rotatlon bet'ween the two magnet'ic coupllng parts.
. .
47,4
--4--
SUMMARY OF THE IN~NTION
In accordance with'the present invention, a load
research magnetic tape recorder receives a two reel tape
cartridge and includes a tape transport assembly including a
capstan aæsembly, and supply and take-up spindle'assemblies.
The capstan and take-up spindle assemblies are driven by a
' drive motor so that magnetic tape is pulled from the supply
''' ~ reel past a magnetlc record head and onto the take-up reel ' '
of the cartridge. The capstan assembly is driven directly - -
from a drive motor and engages the recording tape at a pinch
roller to continuously dri~e the tape at low tape speeds.
The supply spindle assembly includes a two-part magnetic
brake including statlonary and rotatlng par`ts with'one part
being permanently magnetized and the other part being o~ a~ -
soft or permeable magnetic material. The upper end of the
rotating part includes pins ~or engaging the hub of a tape
supply reel of the cartridge. Permanent magnet ~lux of the
magnetized part ls directed into'khe permeable magnetic
material of the other part so as to provlde'magnetic attrac-
tion therebetween producing a predetermined drag ~orce on
the supply reel as tape is pulled therefrom by the capstan.
A thin non-magnetic spacer washer separates the two'magnetic
brake parts to protect the space therebetween from accumu-
lating dlrt and debriæ and attraction of magnetic partlcles
therebetween tending to alker the magnetic retarding e~fect
thereof and producing damage to the brake parts. The spacer
washer'pro~ldes'the non-magnetic air gap spacing and e~ects
added frictlonal forces' adding to the magnetlc drag forces
of the' brake.'
The'capstan aæsembly includes a capstan shaft and
f~ 3
1~'1, 1l8g
--5--
a gear carried at the lower end thereof which is directly
driven by a drive motor pinion gear. The motor provides
constant rotating speed at the capstan. A positive driving
and non-slipping drive belt connects the capstan assembly to
the take'-up spindle assembly including a magnetic clutch.
The magnet'ic clutch has two parts including a clutch driving
part driven by the non-slipping belt and a clutch driven
- part carrying reel hub engaging pins for driving the take-up
reel of the cartridge. One of the magnetic clutch parts is
10 permanently magnetized and the other is made of a soft or ''~
permeable magnetic material so that the d~lven clutch part
is rotated by the drive motor via the magnetic coupling
between the driven and driving parts of the` magnetic clutch. ~ -
Controlled take-up reel speed is maintained by increasing , -
slippage at the clutch so the magnetlc tape speed between
the capstan and the take-up reel is substantially constant
during the tape transporting operation. A spacer washer in
, the air gap space of the magnetic cluteh prevents accumulation
of fragments o~ interfering materials.
- Accordingly 9 supply and take-up recording tape
tensions and speeds are controlled and maintained by an
improved tape transport assembly including a suppl~ spindle
assembly having a magnetic brake with a spacer member formed
between the stationary and rotational parts thereof and
~urther including a take-up spindle assembly~havlng a mag-
netic clutch with a spacer washer between the dri~en and
driving parts thereor. The magnetic clutch and'the znagnetic
brake'co'operatlvely maintain the des'ired and contr~lled tape
tensions at a tape'supply reeI and controlled speed Yariations
3o at a tape ta~e-up reel so as to pre~ent undes~red tape
. .
. .
3 47,11~8
transporting variations due to wear and contamlnatlon of the -
related mo~ing parts and to produce increased reliable and
maintenance free operation for continuous operation under
varying and o~ten extreme environmental conditions. These
and other advantages and features of the present invention
will become apparent from the description of the drawings
briefly described hereinafter.
BRIE~ DESCRIPTION OF THE ~RAWINGS
Flgure 1 is a front elevational view o~ a magnetic
tape recorder made in accordance with this invention and an
associated tape cartridge;
Fig. 2 is a cross-sectional view taken along the
axis II-II in Fig. 1 and looking in the di~rection of the
arrows with parts removed illustrating a tape transport
assembly,
Flg. 3 is an enlarged view showing o~ a take-up
spindle assembly having a magnetic clutch included in the
tape transport assembly shown in Fig. 2;
Fig. 4 is an enlarged view of a supply spindle
assembly having a magnetic brake included in the tape trans-
port assembly shown in Fig. 2;
Fig. 5 is a side elevational view w~th parts
broken away of an alternative embodiment of a magnetic ~rake
lncluding a magnetic coupling ad~usting arrangemenkj and
Fig~ 6 is a cross-sectional view~taken along the
axis VI-~I in Fig. 5 and lookIn~ in the direction of the
arrow~.
DESC~IPTION OF THE PR~FEKRED ~MBODIMEN~S
Re~erring now to the drawings and more particularly
3o to Fig. l, there is shown an electric load research tape
. " '
~2 ~ ~ 3
7 47,488
recorder device 10 made in accordance with the present
invention~ The recorder lO is typically used by electric
power suppliers for elec-tric po~er usage surveys wherein
meter pulses are recorded along with time interval pulse~ as
disclosed ln UAS~ Pat. Nos. 374709470 and 3,913,12~, bo-th
assigned to the assignee o~ this invention. The present
invention is an improvement of the recorder dislosed and
claimed in U.S. Pat. No. 3,602~458 also assigned to the
assignee o~ this invention. The general arrangement and
1~ operation o~ the recorder lO is described in the last-named --
patent except ~or the invention as ~escribed hereinO
Generally, the recorder 10 includes a frame 12
formed by a bottom plate 14, middle plate 16, and top plate
18, me frame 12 carries the tape transport assembly 20,
shown in Fig. 2 and forming an important ~eature o~ the
present invention, as described more fully hereinbelow. m e
tape transport assembly 20 lncludes a cap~tan assembly 22
including a capstan sha~t 24 and a supply spi~dle assembly
26 and take-up spindle assembly 28~ Spring loaded pins 30
o~ the supply spindle assembly 26 and s~ring loaded pins 32
o~ the take-up splndle assembly 28 are exposed through
openings of the middle plate 16. A magnetic record head 34
is carried on the middle plate 16 adJacent the capstan sha~t
24.
. .
~; A second main unit o~ the recorder 10 is a ~ape
cartridge 38 which is substa~tially~identical as described
and claimed ln the aforementioned Pat~ No~ 3,602~458 includ-
~ ing a housing 40 having rotatably mounted therein a supply
- reel 42 and take-up reel 44 carrying a predetermined length
:
,.... . .
~7,488
--8--
of magnet:ic recording tape 46 extending between the reels 42
and 44 and around the outer surface'of a spring biased pinch
roller 48. Upon inserting the cartridge 38 into the cart-
ridge recelving area over' the middle plate 16, the pinch
roller 48 ~iases the magnetic tape 46 again~t the capstan
shaft 24 and posltlons the'tape against the record head 34.
As descrlbed in the aforementioned Pat. No. 3,602,458g the
plns 30 and 32 engage the supply reel 42 and take-up reel
44, respectively. Controlled rokation of the reels is
lU provided by the tape'transport assembly 20 of the present
invention. . .
The tape transport assembly 20 is more clearly
shown ln Flg. 2 whlch is a cross-sectional`view taken along
the axis II-II of Fig. 1 and looking in the direction of t,he
arrows. The operative parts of the cartridge 38 are shown
ln Flg. 2 for a better understanding of the present lnven-
tion with the cartrldge 38 being mounted in the operative
and mounted position on the mid~le plate.16 with respect 'to
the tape transport assembly 20 of the re¢order. 10. Accord-
lngly, the reel 42 and reel`44 are shown with hub portions
42a and 44a thereof belng engaged by the,pins 30 and .32 of
the spindle'assemblies 26 and 28 as described hereinabove.
The tape driving rotation o~ the capstan sha~t 24 is pro-
vided at a gear 52 mounted on the bottom of.the ~haft 24
which meshes with a pinion gear 54.carried.by the shaft of a
drive motor:56. The drive motor 56, being carried by the
bottom plate.l4-, rotates at a predetermined substantlally
low spee'~ to:lmpart a cont~inuou~ unidirectional movement of
thé'tape'46 from the ~upply reeI 42'.onto the take-up reel
3o 44. The'rec'order 10 is -typically in contlnuous use'~or
.j ~
. .
47,488
_9_
periods in the order of one month and the tape speed moves
slowly, in the order seven inches (17.8 cm.) per hour. The
capstan shaft 24 is rotated approximately one revolution,
every 15 minutes ~or movement o~ 1.75 inchès (.4.4 cm.) of
tape movement.
The supply spindle assembly 26 forming an impor-
tant part o~ the tape transport assembly 20 includes a
spindle shaft 58 positioned so as to be coaxially aligned
along the axis 60 extending through the center of the supply
reel 42 when mounted in the recorder 10. The lower end of
the spindle shaft 58 is threaded so as to be secured.by nut
61 within a hole opening o~ the boktom plate 1.4. The upper
end o~ the assembly 26 terminates at the pins 30 carried by
a pin support disc 62 held in place at the upper end thereof
by a retaining clip 64 for rotation about the upper end o~
the spindle shaft 58. The assembly 26 includes a magnetic
brake 66 for maintaining a controlled and substantially
constant tape tension in the tape 46 as it is ~ed ~rom the
tape coil on th~ reel 42 to the pulling engagement between . '
20 the pinch roller 48 and oapstan shaft 24. '
The magnetic brake 66 is also shown in the en-
larged view o~ ~ig. 4 and includes a stationary part 68.
The stationary part 68 is permanently magnetized including a
flat ring 6.9, that is magnetlzed with several magnetic
polesf and a magnet support plate.~0 lntegrally atta¢hed by
a suitable'adhes'ive to the bottom face o~ the magnetized
ring 69. In one p.re~erred embodiment, the permanently .
magnet'i.zed ring 69 is formed o~ an Alnico 5 permanent magnet
.
material oriented per'pendlcular to the diameter and having a
3o thicknes~ in the order of o.~6 inch (0.'4 cm.), an outer
47, 4~38
-10--
diameter in the order of 1.25. inch (3.18 cm.) and a center
hole having a diameter of 0.625 inch (1.6 cm.). The magnet-
ized ring 69 i8 magnetized with eight magnetic poles circum-
ferentially spaced on the upper face of the ring 69 around
the shaft 58. The common directlon o~ magnetization o~ the
eight magnet'ic poles ls parallel with the axis 60.
. An enlarged diameter section 72 of the shaft 58 is
.I disposed in the center opening of the ring 69. The lower
part of shaft 58 extends through the center of the magnetic
support plate 70 so that a lower annular shoulder of the
j shaft porti.on 72 iS clamped against the support plate 70
: when the shaft 58 ls attached to the bottom.plate.14 by
, means of the nut 61 threaded to the thread,ed end o~the
': shaft 58.
A rotational part 7ll of the magnetic brake 66 is
formed by an annular permeable or soft magnetic plate
(~ormed of a cold rolled steel material).that is integrally
attached to the bottom o~ the pin suppork disc 62. It is to
be understood that the permanent magnet material, such as
; 20 forming the rlng 69 has a high retentivity property so that
residual magnetism therein remains substantially permanently.
The 80~t or permeable magnetic material used ~or the plates
70 and 74 has a low reluctance characterlstic whlle havlng a
relatlvely low retentivity propert~. Holes in the cenkers
of the' magnetic plate 74 and of the pin suppork disc 62
recéive the'upper end of khe spindle shaft 58. A spa¢er
washe'r 78 is mounted on the'shaft :58 and in the non-magnetic
air gap between the'magnet:i.zéd ring 69 and so~k magnetlc
plate'74., The spacer washer is pre~erably made of a non-
magnet'ic plastic ~ilm material sold under the' trademark
47348~
"Mylar" by Du Pont de Nemours, ~.I..and Company or the
equivalent. The Mylar material is a polyethylene terephthal-
ate composition which is strong and wear resistant, non-
porous and dimensionally stable at high temperatures and
further has substantially no magnetic characteristics. The
spacer'washer 78 has a thlcknes's in the order o~ 0.01 inch
(0.25 cm.) and has a outer diameter ln the order of 1.125
inch t2..9 cm.) and has a hole in the center thereof to
receive'the' shaft 58 as shown in Figs. 2 and 3.
The spacer washer 78 spaces the lower face of the
magnetic plate 74 and the' upper face of the permanent magne-
tized ring 69 so as to control the gap space.therebetween.
The gap is referred to as an air gap to dis~tingulsh'from a
low reluctance path, although the plastic washer 78 is ~
disposed therein. This provides an important advantage ln
this inventi.on in that the non-magnetic or air gap through :~
which the magnetic fluxes pass between the magnetlc poles of
the ring 69 and plate 74 is accurately controlled. Thus,
the gap spacing is variable with different thicknesses of
the washer. If the magnetic plate 74 rests on the upper
shoulder of the enlarged sha~t section 72~ extremely close
tolerances in manu~acturing must be maintained and as~embling
of the parts,must be carefully controlled in order to maintain ~.
a controlled magnetic air gap space. The use o~ the spacer
washer ellminates the very close eXaGtneSs ln these manufac-
turing oper'atlons. A furthe'r highly advantageoùs feature of
the spacer washe'r 7~ is that.the'~gap space.between the
magnetizéd ring 69 and thb magnet'ic plate.74 is occupied by
the washer 78 so that dust and magnet:ic particles are'not
attract'e:d and co'llected the'rei'n to var~ the characteristics
,: ', "" , ' `' '
47~48g
~12-
of the magnetic brake operation and cause wear and damage to
the relatively rotating parts of the magnetic brake 66. The
spacer.washer 78 additionally provides a substantial.propor-
tion o~ drag provided by the magnetic brake so that the
; overall size o~ the magnetized ring 69 may kept at a minimum
to reduce the: cost and space:required for the supply spindle
assembly 26.
- The magnetic brake 66 is assembled by first mag-
netizing the ring 69 with plural magnetic poles. Then the
integral part~ 69 and 70, washer,78 and lntegral parts 62
., and 74 are assembled to the splndle sha~t 58. A test reel
is engaged by the pins 30 and the torque required to rotate
the tes't reel measured. The ring 69 is de~agnetlzed until
the desired braking torque is ob-.tained. A calibrated torgue
of 1.2 inch-ounces is provided to rotate the disc 62 against
the drag force o~ the brake 66. Dlmensional changes in the
gap spacing between the parts 74 and 69 can produce undesired
results ~hereas use o~ the washer 78 closely.cantrols the
gap so that it ls substantialIy constant.
The tape tenslon between the reel 42 and the
capstan shaft increases slightly in.operation from a substan-
tially ~ull reel so that the tension approxlmately doubles
when the reel becomes empty of tape. It i~ belie~ed that
the permanent magnet ~luxes from the rlng 69 induGe consequent
or virtu&1 poles in the permeable magnetic plate 74. The
resulting magnet'ic attractlon between the permanent magnet
poles and ~irtual poles resists.,rotatlon of the'.plate '74.
The washer 78 produces an additional frictional ret'ardlng
force''on the plate 74.: Th.usj the '.tension in tape 46 between
the reel 42'and capstan shaft 24:is wlthln controlled low
3 47,4~,~
13-
limits3 generally in an approximate range of two to ~our
ounces; so as to be characterized as being substantially
constant. It is to be recalled that the rotation of the
reel 42 varies withln a relatively low range of speeds.
The take-up spindle assembly 28 shown in Flg. 2 is
mounted'along the axis 8b including the center axis of the
take-up reel 44 when the cartridge 38 is in the mounted and
'~` ~ operatlve position shown in Fig. 2., A magnetic clutch 82 is
included in the assembly 28 to rotate the reel 44 when it is
engaged by the pins 32 so as to wind up the tape 46 into a
coil thereon as the tape is ~ed ~rom the capstan shaft 24
and pinch roller 48. The speed is varled as the tape ll6 is
wound on the reel so that it does not pull`the tape relative
to the capstan nor allow access slack in the take-up tape ,
portion between the capstan and the coil on the reel 44.
As shown more clearly in Fig. 3, a spindle shaft
86 o~ the assembly 28 is mounted along the axis 80 and the -
lower threaded end thereof recelves a nut 87 which holds the
shaft 86 to the bottom plate 14. A bushing 88 supports the
bottom of a pulley 90 on the bottom plate 14. The bushing
88 and the pulley 90 may be made o~ an integral part. A
groove in the pulley 90 receives a belt 92 mounted in a
groove 93 at the lower end o~ the capstan sha~t 24 shown in
Fig. 2. The beIt 92 is in non-slipping engagement with the
groove 93 and the groove in the pulley 90.
A permanently mag~etized flat ring 94 is secured
by a suitable adhesive to the pulley 90 and has a hole
through the'center thereo~ ~ec'eiving the spindle shaft 86.
The magnet'ize'd'rlng 94 is made of a permanent magnet' mater-
ial such''as that describe'd for the ring 69 and includes a
, ~ .
47,il8-14-
plurality, such as eight, magneti.c poles therein circumfer-
entially disposed around the shaft 86. A stronger permanent
magneti.zing material may be used in some instances rather
than the type used for the ring 69 due to reduced space for
the ring 94. ~he magnetlzed ring 94 forms the driving part
of the magnetic clutch 82.
The drlven part of the magnetic clutch 82 includes
a permeable or soft magneti.c plate 96 integrally attached to
a pin support disc 98 corresponding to the pin support disc
62. In an alternative embodiment, the plate 96 is also
formed of a permanent magnet' material having corresponding
plural magnetic poles therein in a magnetically.attracting
relationship with the magnetic poles of the`ring part 94.
The magnetic plate 96 is positioned above the magnetized
ring 94 by a bearing washer or enlarged shaft section 100 o~
the shaft 86 so that a predetermined axial magnetic air gap
is formed between the magnetlc poles of the magnetized ring
94 and magnetlc plate g6. The air gap space of the clutch
optionally includes a Mylar spacer washer 102 formed to fit
in the space between the magnetized ring .94 and magnetlc
plate 96 to protect against aocumulation of dirt and magnet-
ized particles in the magnetic coupling space between the
parts 94 and 96.
The magnet~c:coupling between the driven part 96
and driving part 94 of the clutch 82 is also~believed due to
the'attraction between~the consequent or virtual poles
induce'd' in the plate 96 and the permanent:magnet poles of
the'ring 9~. The'changes in rel'ati~e rotation or slippage
are'due'to thb'ch'anges in the' diamet:er o~ the' tape on the
reel 44,but ~n a controlled m?nner as established by the'
..
~ 2;~3
1~7~4~8
-15-
clutch 82..
In operation of the tape tran~port assembly 20,
the supply reel 42 is considered to be lnitially filled with
a coil.thereon of the tape 46 with the take-up reel 44 belng
substantially empty of the tape 46. The motor 56 drives the
capstan sha~t 24 through'the'gears 54 and 52 at the speed of
one revolution per ~ifte.en minutes as noted hereinabove.
S~',,5~ The magnetic brake 66 produce's a drag on the reel 42 so that
reslsting torque'is developed at.the reel 42 when the capstan
10 pulls the tape 46. As understood in the operation of tape
recorders, the'supply reel 42.initially moves slower than
the take-up reel 44 due to the differences in diameters o~
coils of the' tape 46 on the reels. Initial~ly, a minimum
amount o~ sllppage and highest output speed relative to a
constant lnput speed occurs at the magnetic clutch 82 of the
take-up spindle assembly 28. Also, inltially, about three
inches o~ tape is wound on the take-up reel 44 with each
revolution thereo~ whereas approximately ten inches of tape
is ~ed ~rom the reel 42.with each revolution thereof. As
the tape 46 ls fed from the reel 42 to.reel 443 the opposite
empty and filled reel conditions are reached wherein:approxi-
mately three inches of tape wlll be fed from.the reel 42
with each revolution whlle approximately ten lnches will be
placed on the reel 44 with each revolution. .Due to the
increase'in diameter o~ the tape 46 on the ræel 44, controlled
slippage'incr:eases at .the magnet'ic clutch 82.and th.e output
speed dec'r'eases. Accordin~lyJ the magnetic c.lutch 82 ini-
tially pro~ides approximatel:y one-half.rev'olution o~ the
driven part :96. ~or each'capstan sha~t revoluti:on. At the
end o~ the'tape 'take'-'up oper'ation, the''clutch'slip increases
.. . . . . .
47,48
-16
so that the driven part 96 rotates only about .twenty percent
of a revolution relative'to: a complete rotation of the
capstan sha~t. At the end of the winding operation,'the
torque developed in the supply portion of the tape 46 between
the reel' 42.and capstan 24 will change slightly to about
twice the initial tension. As noted above, the reel 42
reaches its hi'ghest rotatlonal speed and the reel 44 reaches
its slowest rotational spee'd when the tape coil on the reel
44 includes substantially all o~ the strip of tape 46 provlded
in the cartridge 38. In typlcal operation the tape movement
is continuous for a period of one month.
An alternative embodiment of a supply spindle
assembly 108. is shown in Figs. 5 and 6 including an alter~
.native magnetic brake 110 havingla magnetlc coupling ad~us~-
ment feature. The spindle shaft 58 is substantially as
described in connection with the descriptlon of the supply
spindle assembly 28. A soft magnetic plate 74 and integral
pin support disc 62 with the pins 30 are also provided as
described herein~bove ~or the assembly 26. A series of
eight separate cylindri¢al permanent magnets 113, 114, 115,
116, 117, 118g llg, and 120 are slidably mounted.on a so~t
: or permeable magnetic support plate 121 to de~ine eight
sepa~ate magnetic poles of the stationary.part of the magnet~c
brake'llO. The permanent magnets are mounted in slots 122,
123, 124,. 125, 126, 127, 128 and 129 extending through both
the magnet support plate 121 and the bottom plate.14.
Screws' 132'.éxtending through the''slots cla~p the permanent
magnet's.ln adJu~table radial positions relative to:the
ce'nter'axis 60'o~ the'supply splndle ~ssembIy 108 when
arranged as is the' assembl'y 26. in ~he recorder. Accordingly,
47,4~8
-17-
a variable drag torque can be ad~usted by the positioning of
the separate permanent magnets.113 through 119 relative to
different radial positions of the magnetic plate 74. Fewer
than all eight of the separate permanent magnets, such as
alternate permanent magnets.113, 115, 117 and 119, may be
mounted in slots so that they can be ad~usted to provide a
desired reel drag ad~ustment to produce a desired drag
... . during the tape playout operation of the assembly 108. The
non-magnetic plastic spacer washer 78 is provided between
the faces of the permanent magnets designated 113 through
1 120 and the bottom surface of the magnetic plate 74 as
:: provided in the assembly 26. Thus, the washer 7a provides
the air gap spacing and protection o~ the magnetic air gap
from debris and magnetic parti.clesO As noted rOr the spacer
washer 78 hereinabove, ad~usting of the thickness o~ the
washer is a further means of ad~ustlng the magnetic gap
between permanent magnets and the plate 74 to ad~ust the
retarding torque or magnetlc drag produced by the magnetic
brake 110.. The washer 78 also produces additional frictional
retarding force as the plate 74 is rotated thereon.
While preferred embodiments of the presenk lnven-
tion have been described hereinabove, it is to be understood
that obvious modifications and alterations thereof may be
made by those skilled in the art without depar~ing from the
spirit and scope of the following claims. - :.
