Note: Descriptions are shown in the official language in which they were submitted.
This inVention relates to method and apparatus for
continuously forming molecularly or~ented articles generally
comprising a rotary ~tretch-Blow mold machine.
While the blow molding art goes back over one
hundred years, it has only been in the last twenty years or so
that blo~ molding of hollow plastic articles such as containers
has achie~ed significant commercial success. Along with the
increased interest in blow molding techniques has come the
strong desirability ~or improving the strength and other
properties of finished containers prepared in this manner.
Known ways of improving strength in plastic containers include
changing the chemical structure of the plastic material during
synthesis by means of strength imparting modifiers or increasing
the wall thickness of the finished article. The former way may
undesirably affect other properties of the material while the
latter could be rather costly.
Another attractive way of improving the strength
properties of a finished container involves the molecular
orientation of the thermoplastic material being blow molded
into the container. Generally speaking, molecular orientation
of a s-~itable thermoplastic material is obtained by stretching
such material while in the solid state at a temperature just
below its cr~stalline melting point. However, while orientation
can result in a su~stantial increase in tensile strength it
cannot be obtained using a conventional blow molding operation.
One method of obtaining the desired oriented product is shown
in Wiley et al, U.S. Patent No. 3,507,005 and involves extruding
a hollow parison, cooling it to room temperature, carefully re-
heating it to just ~elow its crystalline melting point, grasping
the parison at one end while pinching or clamping it at the
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other end and stretch~ng Lt longitudinally. Then while still
held at the ~irst end the parison is enclosed in a mold and
blown to conform to tne shape thereof. Such a process is some-
what complex and does not readily lend itself to the high
speed fabrication which is desired in a successful commercial
operation. Another method for preparing oriented containers
involves the initial preparation of an elongated thermoplastic
workpiece such as a prePorm closed at one end. The preform is
then brought to the necessary temperature and placed in an
enclosed mold oVer a rod which is extended to stretch said
preform after ~hic~ it is blo~n using pressurized air to
obtain an article having the des~red biaxial orientation. While
such method represents an attractive way to prepare oriented
containers, it must ~e carried out in apparatus suitable for
high speed fabrication to make it economical.
Although a large number of blow molding devices
;` suitable for continuous high speed production have been
; disclosed, most are directed to the conventional, non-orientation
blow molding process and do not concern themselves ~ith the
~ethod wherein a rod is extended and retracted in the mold
during fa~rication of the container.
; The present invention relates to an apparatus and
; method capa~le of continuously forming molecularly oriented
~ articles, said apparatus comprising a multi-station rotary
stretch-blow molding machine particularly adapted for rapid
< feeding and discharging from said machine.
More specifically, t~e present invention provides
an apparatus for continuously forming molecularly oriented
articles generall~ comprising a plurality of radially partible
blo~ moIds disposed at angular intervals on a support mounted
on a frame and adapted for continuous rotation about a
substantially vertical axis, mold moving means for moving the
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10~6U~
mold sections of said molds ~etween open and closed positions
in synchron~zation wi~th rotation of said support, strPtch
rod means for each mold opera~le in comhinat;on w~th said
mold mov~ng means and ~ncluding stretch rod positioning means
for longitudinally reciprocating a stretch rod while within
a cavity of said mold, pressurized fluid means associated
with said stretch rod and a vertical container discharge chute
in the vicinity of the cavity of each mold.
In another em~odiment of this invention, a stretch-
blow mold machine having a stretch rod which is reciprocally
movable both within the mold cavity and into and out of the
cavity is provided ~ith feeding and discharge means for
simultaneously feéding a workpiece while discharging a
molecularly or~ented blown article.
From a process standpoint, there is provided in the
process of blow molding articles from preforms which includes
the steps of positioning such preforms within cavities of
continuously moving and successively presented blow molds "
; distending the preforms within the moving molds to form the
articles and discharging the art;cles from the still-moving
molds at an eject station prior to charging with additional
preforms, the improvement comprising holding or storing a
preform temporarily at each such moving mold while an article
' is being formed in the cavity therein from a prior preform.
~ In describing the overall invention, reference will
; be made to the accompanying drawings wherein:
FIGURE 1 is a schematic side elevational view showing
one mold station of the rotary blow molding machine and~incor-
porating the novel apparatus components of this invention;
FIGURE 2 is a schematic plan view showing one mold
station of the rotary blow molding machine;
;~ FIGURE 3 is a schematic front elevational view of
one mold station of the rotary blow molding machine; and
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FIGU~ES 4 to 11 are partially sectioned elevational
side views showing the sequence of operation of one mold
station at various times during i~ts rotation a~out the rotary
support,
Referring to the drawings, there is illustrated in
Figure 1 a rotary ~low molding machine designated generally
as 10 for cont~nuously forming molecularly oriented articles
such as containers and part~cularly bottles. Only one mold
station is shown, however a plurality of identical mold
stations are equally spaced at intervals around the periphery
of the supportLng structure.
Blow mold`machine 10 comprises a vertical shaft 12
carrying a huh 14 for continuous rotation therewith by
conventional drive means such as a motor, gear reducer, or the
like~ not shown, ~ixedly attached to hub 14 is a circular
mold supporting plate 16.
A plurality of identical mold units generally
; indicated by the numeral 1~, only one of which is shown
and which ~ill be descriBed hereafter in detail, are equally
spaced about the supporting plate 16.` Each of the mold units s
18 comprise partible mold sections 20a and 20b which in the
closed position define cavity 22, the surface of which
conforms to the shape of the body of a hollow article such as
a bottle to be molded therefrom from a thermoplastic material
(see Figure 8~o Mold sections 20a and 20b may be convention-
ally secured ~e,g. by bolts or clamps) in mold platens or
carriers 24a and 24~,which in turn are operatively associated
with the remainder of the apparatus in a manner to be described
hereafter ~n more detail.
Each platen 24a and 24b of partible mold unit 18 is ~ ;
slida~ly supported by guiae rods 26, 28, 30 and 32 which also
maintain the alignment of the platens and attac~ed molds
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(see Figure 3L. The ~our guide rods are f~xedly attached to
the support~ng structure w~ich l~s mounted on t~e support~ng
plate 16.
Outer mold sect~on 20~ and platen 24b is reciprocally
moved between open and closed positions by the movement of'tie
roas 34 and 36 ~igure 2~ which are secured to the platen by
any conventi~onal means and ~llustrated e.g. by bolts (Figure 1).
There are provided actuat~on means for synchronization of mold
movement w~th the rotation of the supporting plate 16 through
the use o~ a scotch yoke assem~ly, or equivalent, as described
below.
~ s ~llustrated in F~gure 1 mold opening and closing
cam 38 is fi~edly attached to the base of the machine. Cam
roller or follower 40 ~s attached to lever 42 and moves within
the contoured slot 44 found in cam 38. Lever 42,is connected
to shaft 45 through detent Ctorque limiting device) and gear
assembly 46. The shaft 45 is connected to a cam or eccentric
member 48 and this to a pair of crank or lever arms 50a and b.
The lever arms are connected through connecting pin 52 and
bearing 53. Lever arm 50b is attached to another cam 54.
Bearing 53 is free to move about the conn,ecting pin and fits
into a slot 56 on plate 58 of the scotch yoke assembly (Figure
2). Tie rods 34 and 36 which are secured to the outer mold
section 20b and platen 24b are fixedly attached to plate 58
of the scotch yoke assembly and reciprocally move in a lateral
direction with rotation of the shaft 45 through the action of
the components described above.
Inner mold section 20a and platen 24a also move with
rotation of the s~aft 45 but to a lesser degree than the outer
mold. This is accomplished through the interaction of cams
48 and 54 and their associated rollers 60 and 62. The rollers
are attached to platen 24a ~hich in turn is supported and
reciprocall~ slides on guide rods 26, 28, 30 and 32.
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Inner mold sect~on 20a is ~oyed throu~h the force of spring5
26c and 28c pos~tloned on gu~de rods 26 and-28 respectively
CF~gure 1~ and those on gu~de rods 30 and 32 (not shown) which
push aga~nst platen 24a and the rollers 60 and 62'as cams 48
and 54 moYe to the le~t when the mold is opening.
In synchronization with movement of the mold sections,
the stretch rod 64 ~s ~ein~ moved to the desired operating
positions as follows:
Stretch rod 64 is moved between its fully extended
position ~Figures 4 and 7~ and its position just prior to the
start of the stretching operation (Figures 5 and 6) through
the movement o~ housing means such as air cylinder 66 by
the action of air cylinder cam 68 and air cylinder cam rollér
(followerl 70. Stretch rod 64 is affixed to the air cylinder
shaft (not s~o~n) in air cylinder 66 and moves in combination
with said air cylinder and shaft. Air cylinder 66 is connected
to cam roller 70 ~y ~racket 74. Bracket 74 and air cylinder
66 slide in ways or tracks ~not shown) in the supporting
structure or frame designated generally as 77 which is attached
to rotating support 16. As the support 16 rotates, air
cylinder 66 moves in the tracks via interaction with cam roller
70 which moves within the slot 72 of cam 68 which is fixedly
attached to the non-moving base of the machine. Cam 68 shown
; - as a box cam travels a]l the way around the rotary machine
.~ , ,
and depending on the shape or direction of the contoured slot
72, cam roller 70 and the connected air cylinder 66 and asso-
ciated structural components move up and down as desired as
the support 16 rotates. By this action stretch rod 64 is ~ ;
raised from the beginning of the stretch operation ~Figure 6)
; 30 to its fully extended position (Figure 7).
In the embodiment illustrated, the withdrawal of
stretch rod 64 from the mold cavity 22, i.e. from its stretch
.
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106ti~
beginning or after blo~ position (Figure 6 and 8) to its com-
plete removal from the cavity CFigures g and 101 is carried
out ~y the appl~cation of a~r to t~e top side of the piston
(~o~ shown) ~n a~r cylinder 66. This causes the shaft attached
to the piston and the connected stretch rod 64 to be pushed
downward lowering said rod ~nto sealing plug 76 as shown in
Figures 9 and 10. Application of air pressure is through valve
79 and actuation of this valve is via valve actuation means.
Actuation of this valve is caused through interaction of cam 81,
1~ fixed to the base of the machine, and cam roller 83 connected
to the valve ~y rod or shaft 85. The valve 79 is affixed to
; the supporting structure 77 in a conventional manner not shown
and rotates with said structure as support 16 to which it is
attached is rotated. The cam roller 83 travels along cam 81
completel~ around the machine and by its movement it changes
the direction of valve 79 causing air to be applied to one side
or the other of the piston in the air cylinder thereby raising
or lowering the stretch rod 64. Air is also being applied when
the stretch rod is ~eing moved within the cavity by the inter-
2Q action of cam 68 and cam roller 70. This air is applied to the
bottom of the piston in air cylinder 66 through air valve 79
and keeps the stretch rod 64 extended during this part of the
cycle. The actual air supply connections from valve 79 to
the air cylinder 66 has not ~een shown so as not to further
complicate the drawings and distract from the essential features
of this invention.
In the embodiment illustrated in Figures 7 to 10, neck
jaws 78a and 78b open and close around the neck of the workpiece
and blown article through the movement of air cylinders 88 and 90
3a ~hich are affixed to the mold sections 20a and 20b and platens
24a and b, T~e respective ~aw~ can be further moved, for reasons
to ~e described ~elow, By movement of the respective pistons
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and connected s~afts of the air c~lInders 88 and 90.
Actuation of such mo~ement can ~e by any of the conventional
means, not shown, such as a cam or dog fixed to the base
of t~e machine wh~ch tr~ps lim~t sw~tches to open or close
the air supply valve.
Sealing plug 76 is moved up to seal the neck of
the workpiece and the stretch rod when the mold is closed
through means of sealing plug cam 80 and sealing plug cam
roller 82 CFigure 1~. Cam 80 is attached to the non-moving
base of the machine and cam roller 82 travels in an up and
down manner along the cam there~y moving the sealing plug which
is attached to it via the action of lever 84 and eccentric
member 86 as the support 16 rotates. Spring 87 CFigure 1)
holds the plug 76 when it is in sealing engagement and thus
cam 80 does not have to completely go around the machine and
may only be placed in positions where the sealing plug 76
is to be lowered. In other words the cam roller 82 can be
allowed to travel freely until it again engages the cam 80.
As shown in Figures 4 to 11 feeding and discharge
2Q means are provided to rapidly feed workpieces 92 and discharge
blown articles 98 ~rom eac~ stretch-blow mold. A plate 94
is af~ixed to outer mold section 20b a~d platen 24b~and moves ~-
in a lateral manner along with the movement of such parts through
.. :
rotation of support 16 and the means described above. The
~ workpiece or preform 92 is dropped into guide means, i.e. a
chute or funnel 96 preferably located in the vicinity of the
cavity of each mold station ~y a conventional pick and place
device or other means. The vertical chute or workpiece-holder
96 is supported in a conventional manner, not shown, preferably
3Q - by support 16 or by some other structure or apparatus and along
with plate 94 provides a means for guiding and retaining the
workpiece 92 until t~e mold ~as opened and stretch rod 64 is in
position to receive ~t and start t~e sequence for forming an
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1~6~0~5
article, At the same tLme, a blown article such as bottle 98
is being d~scharged from the mold through opening 100 in
support 16, associ~ated Wl`t~ a conventional discharge chute,
as shown. ~lternat~vel~, such discharge opening and chute
supported from support 16 could be upwardly disposed on the'
axis at cavity 22 to accommodate an upwardly discharging system.
The bottle 98 is retained in the outer mold section 20b by re-
taining means comprising the overlay section at the top of
outer mold 2ab and through ~aw means i.e. the right neck jaw
78b which has a shape or configuration which surrounds a
significant portion or section of the neck of the bottle 98
~Figure 10~. Thus the bottle moves with the right hand mold
20b and neck ~aw 78B. When the bottle is generally over open-
ing 100 (Figure 11~, the neck jaw 78b is pushed laterally to the
left by actuation of releasing means comprising air cylinder
90 and its connecting shaft thereby releasing the bottle from
the mold section of half 20b.
In alternat~ve systems to that just described, for
example one wherein the articles are discharged upwardly from
the open mold, cylinder 66 and its associated air circuitry may
not be required since it will not be necessary to completely
extract rod 64 from the mold cavity with such systems. Or, even
with such just-described arrangement, it may be possible via
proper cam designs to retract the rod from the cavity via t'ne
mechanical cam-follower system above described.
To put the apparatus in proper perspective and par-
ticularly to describe the synchronized action of the respective
components, the operation will be described with particular
reference to Figures 4 to ll which show the sequence~of events
taking place in one selected mold at different times as the
support 16 is being rotated.
The operat~on begins as shown in Figure 4 when a new
workpiece 92 such as-a previously formed thermoplastic preform.
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which has ~een reheated to or~ent~tion temperature and having
a tubular body with one open end and one closed end is dropped
onto a ~ully extended stretch rod 64 and a formed bottle 98 is
~fully separated from mold sect~on 20~ and beginning its descent
through discharge opening 100. The preform 92 is free to drop
onto the rod extending upwardly on the axis of t~e mold cavity
since plate 99 has been moved along with mold section 20b and
platen 24b thereby clearing the lower end of chute 96 above
the now open mold.
In the next step shown in Figure 5, the bottle 98
is now dropping out o$ t~e mold cavity into opening 100 and
optional chute or funnel 102. During this time the stretch rod
64 holding the ne~l~ charged preform ~2 is retracting (lowering)
to its normal start ~stretch beginning~ position. This is
carried out by rotation of support 16 causing cam roller 70
to move within the slot 72 to the lower position in cam 68.
. . ~
The air cylinder 66 being affixed to the roller through bracket
, ~ ,: ,
74 thereby moves in tracks in the frame or supporting
structure lowering the stretch rod 64 and the preform 92 to
its position where stretching ~egins. Application of air
to the lower s~de of the piston in air cylinder 66 keeps the
stretch rod 64 stead~ during movement and also retains it in
the position to which lowered through the action of cam 68 and
; cam roller 70 (see Figure 1~.
~s the support 16 continues to rotate, the mold sec-
tions 20a and 20b and their respective platens 24a and 24b
are beginning to close as shown in Figure 6. This happens
through interaction of the mold opening and closing roller 40 ~-
in the contoured slot 44 of mold opening and closing cam 38
~igure 11. The roller 4a moves ~ith rotation of the support
16 causing the shaft 45 to rotate through the action of
connecting lever 42 and thereby causes the scotch yoke assembly
and particularly lever arms 50a and 50b to rotate. This
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~ \
action causes the tie rods 34 and 36 which are connected
thereto to rec~procally ~oVe in a lateral direction thereby
beginni~g to close outer platen 24~ and îts mold section 20~.
At the same tl~me ~nner mold section 20a is also moving toward
a closed pos~tion through movement of cams 48 and 54 to the
right causing rollers 60 and 62 to move in that direction along
with platen 24a whic~ ~s attached thereto (see Figure 1~. It
is to be noted that rotation of the scotch yoke assembly and
particularly lever or crank arms 50a and 50b is desirably
slightly greater than 180 to make the mold sections squeeze
together w~en closed and there~y lock themselves through the
added tension or clamping force. Cam 38 does not have to
go completely around the machine and may only be placed in
sections where opening and closing of the mold is desired.
As the mold sections 20a and 20b close, neck jaws
78a and 78b also close around the neck of preform 92 through
moVement of air cylinders 88 and 90 which are attached to
said mold sections and platens 24a and 24b. At the same time,
the sealing plug 76 begins to move up through the action of
sealing cam 80, sealing cam roller 82 and lever 84 as shown
in Figure 6,
When the mold sections 20a and 20b reach their
;; fully closed position as shown in Figure 7, sealing plug
76 moves up to seal the neck of the preform 92 and stretch
rod 64.
After the mold closing action is complete and mold
cavity 22 is fully sealed, the preform is distended. Pre-
fera~ly, stretch rod 64 ~egins to rise via movement of cam
roller 70 in cam 68 through continued rotation of support
16 ~see Fi~ure 1). This action causes the tightly held preform
92 to stretch longitudinally as stretch rod 64 approaches
and reaches its fully extended position sho~n in Figure 7.
When stretch rod 64 is ~ully extended, pressurized air is
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provided through open~ngs ~not shown) in stretch rod 64
via a~r supply means 55 causing stretch in the radial direc-
tion, the preform 92 thus becoming fully stretched and
biaxiall~ oriented. Blow a~r may alternately be provided
through the seali~ng plug in a manner not shown.
Due to the clos~ng of the mold, plate 94 is returned
to its position below chute 96 and a new preform 92a îs dropped
; into the chute by external means ~not shown) and retained or
obstructed in its passage by said plate 94. The preform 92a
is now ready for feeding to the blow mold station below
(Figure 7). Holding or storing a preform 92, which has been
inserted in holder 96 from an upstream station, temporarily in
such holder 96 at each moving mold station while an article
is being formed in such mold from a prior preform in the
manner illustrated increases the period during which the mold
may remain closed and functianing on the prior charged preform.
In other words, if the preform were to be charged directly
to the mold from the prior upstream station, as opposed to
merely dropping onto stretch rod 64 from a position already
2Q at such continuously moving station, the mold stations would
have to remain open longer during each cycle, and thus for
a system of equ~valent capacity to that illustrated, additional ;
stations would have to be added, thus increasing the complexity
of the system. Therefore, system efficiency is substantially
increased by loading individual preforms 92 at a charging
station into holders 96 adjacent to and moving with such molds
while articles are being formed within such molds from prior
1 preforms. The molds are then charged directly from such
` holders, preferably while the preforms are at molecular
orientation temperature, during or after discharging articles
formed from prior preforms from the molds at the eject station,
and ~h~le the molds traverse a closed circular path.
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After completing the stretching and blowing
operation, stretch rod 64 begL`ns to retract through the
action of cam roller 70 ~n cam 68 via continued rotation of
support 16. Stretch rod 64 then reaches its intermediate
position ~ithin the cav~t~ 22 as shown in Figure 8.
Stretch rod 64 cont~nues to retract until it is
free of thé mold cav~ty 22 as shown in Figure 9. This happens
when continued rotation of support 16 causes cam roller 83
to move along cam 81 thereby actuating valve 79 allowing
air to be applied to the upper s~de of the piston housed in
air cylinder 66 push~ng attached stretch rod 64 in a downward
position, The mechanical and pneumatic retracting actions
described above may be carried out simultaneously. Simultan-
eously, sealing plug begins to retract from its seated
position to release the blow air from the blown bottle 98.
This is actuated through movement of roller 82 along cam 80
in cooperation with lever 84.
Stretch rod 64 and seal plug 76 is now fully re-
; tracted and the mold sections 20a and 20b begin to open with
continued rotation of support 16 through the action of roller40 and cam 38, reversing the closing operation described above
; (see Figure 10.) -The formed bottle 98 is carried along with
the outer mold section 20b and is held there by the shape
or configuration of the overlay at the top of said section
(bottom portion of bot'tle) plus the configuration of the
surrounding neck jaw 78b. To aid in the movement of the
formed bottle 98 with outer mold sections 20b, as the mold
begins to open neck jaw 78a is moved laterally to the right
against the neck of said bottle by action of air cylinder 88
and its connecting shaft. This added force helps the outer
mold section 20b retain the formed bottle when the mold seal
is first broken and the respective mold halves are separatin~.
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l.~ti~009
As shown ~n Figure 11, the outer mold section 2~b
has now moved into pos~tion generally above d~scharge opening
100 in support 1~. At this t~me, t~e bottle 98 is now released
from its retent~on b~ outer mold section 20b by lateral movement
, of neck jaw 7~b to the left through actuation of air cylinder
90 causing the nec~ of the bottle 98 and the bottom thereof
(facing up~ to move clear of the mold section. At the same
time stretch rod 64 ~egins to extend itself between the mold
sections 2~a and 20b through the application of air to the
lower side o~ the piston housed ~n cylinder 66, or alternatively ~ ;
via coaction bet~een follower 70 and cam 68 reversing the
retraction procedure described above. Alternate means such
as forced air means ma~ be provided in outer mold 20b to help
push the bottle out.
When stretch rod 64 continues to fully extend
itself between the open mold sections 20a and 20b as shown in
Figure 4 the sequence is complete. This is caused by the
moVement of cam roller 70 in cam 68 through continued rotation
: of support 16, reversin~ the procedure described above for
retracting stretch rod 64. Stretch rod 64 is now in positlon
to receive a ne~ preform 92 and repeat the sequence of operation.
The embodiments described above show a preferred
rotary stretch-blow molding machin,e wherein the operation of
the blow molds are synchronized with movement of the
respective stretch rods to provide a facility capable of
preparing molecularly oriented articles in a rapid continuous
- manner thereby saving time and also saving space by the compact-
ness of the arranged equipment.
Variations in the equipment, as would be obvious
to one of ordinary skill in the art, may be implemented. For
example, the opening and closing moVements of the mold
sections may ~e per~ormed in a more conventional manner, ;~
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OU~
wherein both mold sections are moved an equal amount. Ho~ever
of course, the adv~nta~e of economiziny on space as presented
by the preferred embod~ment o~ t~is invention is particularly
strong when commerc~al operati~ons are involved. It is further
noted that Both stretch rod positioning means may be actuated
by mechanical means such as cams. However, it is considered
more pract~cal for commerc~al operations to use the preferred
combinat~on o~ mechanical and pneumatic means. While the
actuation devices shown are a preferred embodiment, other
lQ conventional electrical, mechan~cal, fluidic and instrumenta-
t~on means may ~e used including for example electric timers,
solenoids, cams, pneumatic and hydraulic cylinders, switches,
etc.
The above description and particularly the drawings
are set forth for purposes of illustration only and are not to
be taken in a limited sense. Various modifications and
alterations will be readily suggested to persons skilled in
the art. It is intended, therefore, that the foregoing be
considered as exemplary only and that the scope of the inven-
2~ tion be ascertained from the following cl~ims.
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