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Патент USA US3080483

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March 5, 1963
3,080,473
v. K. KENNEDY
PRESSURE AND THERMAL MATERIAL FORMING DEVICE
Filed Aug. 2, 1955'
2 Sheets-Sheet 1
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65
INVENTOR.
VERNAL KENNETH KENNEDY
?w 725-5
BY
March 5, 1963
3,080,473
v. K. KENNEDY
PRESSURE AND THERMAL MATERIAL FORMING DEVICE
Filed Aug. 2, 1955
2 Sheets-Shee't 2
A
4w
4; 7. 2
IIIIII/I/I
IN VEN TOR.
VERNAL KENNETH KENNEDY
BY
Aaent
United States Patent 0 "
3,080,473
Patented Mar. 5, 1963
2
1
so that the forming tool may be returned to its rest
3,080,473
PRESSURE AND THERMAL MATERIAL
FORMING DEVICE
Vernal K. Kennedy, "an Nuys, Cali?, assignor to
Lockheed Aircraft Corporation, Burbank, Calif.
Filed Aug. 2, 1955, Ser. No. 525,838
8 Claims. (Cl. 219-449)
position.
A feature of the present invention resides in the fact
that the areas adjacent the thermally conditioned area
have ‘accumulated heat present so that additional material
forming in these adjacent areas requires less “dwell time”
than the initial forming operation. Since material form
ing is dependent upon a ‘?xed “dwell time” for every
operation, loss of strength due to overheating is negated
This invention relates to thermal forming devices and
more particularly to an improved thermal forming device 10 ‘and a series of forming operations may be accomplished
having variable “dwell times” which is time-saving for
which relies on the thermal condition of the material
being formed to control the forming operation.
many operations.
‘It is a general object of the present invention to provide
In the held of sheet metal forming, and other similar
a novel means for thermally conditioning material so that
applications such as the heading of rivets, rigid material
often is formed by heating the material to a condition 15 ?orming thereof will not occur below ‘a minimum required
where it becomes pliable followed by the application of
temperature.
a strong force or pressure which forms the material into
Another object of the present invention is to provide a
rapid and emcient means for forming material thermally.
‘Still another object of the present invention is to pro
a desired shape. For example, in conventional dimple
forming machines, forming tools are employed having
a?‘ixed thereto several heating elements. Upon engage 20 vide a novel thermal forming means having an economical
and simpli?ed thermally operated mechanism for provid
ment of the tools with the material, heat generated by the
elements is transferred to the material by means of the
ing positive operation control.
A further object of the present invention is to provide
novel means for controlling the application of pneumatic
period,” and is determined in part by the area being 25 pressure placed on the forming tool.
heated and the type of material used. Usually at the end
An additional object of the present invention is to pro
of a dwell period, a timer switch is employed to cause a
vide a method of forming rigid material so that the pres
tools for a predetermined period of time. This period of
time is generally known as the “time setting” or “dwell
strong force or pressure to be applied to the forming
tools which causes the material to assume the shape of
ence of a strong force will be applied only when the ma
terial has been thermally conditioned.
the forming tools. If additional dimples are to be formed, 30
With the above and other objects in View, my invention
the dwell period remains constant for each dimple
consists in the arrangement, combination and details of
‘formed, regardless of the material temperature.
construction disclosed in the speci?cation and drawings,
A di?iculty exists in such a conventional thermal form
in which:
ing device due in part to the fact that the strong force
FIGURE 1 is a side elevational View of a thermal dim
is sometimes applied before the material has been ade~ 35 pling device in accordance with the present invention be
quately heated. Forming in this manner causes the shaped
ing shown partly in fragmentary section;
material to be brittle, which results in cracking and
FIGURE 2 is a front elevational view taken along line
2—2 of FIGURE 1 showing a trigger mechanism em
eventual breakdown of the material. Furthermore, the
forming operation is slow and ine?icient due to the lack
ployed in the device :of FIGURE 1;
of positive control of the forming tools during the opera 40
FIGURE 3 is an enlarged front elevational view of the
tion. This generally results in a loss of material strength
trigger mechanism shown in FIGURE 2;
due to overheating.
FIGURE 4 is a schematic drawing of the device shown
These difficulties are overcome in the present invention
in FIGURE 1 ;
in which I provide heating elements ai?xed to a forming
FIGURE 5 is an enlarged sectional view showing the
tool having the con?guration of the shape desired in the 45 forming tools employed in the device of FIGURE 1
material. Heat generated by the elements is transmitted
initially shaping material to form [a dimple;
to the material in order to make it pliable. A low pneu
FIGURE 6 is an enlarged sectional view showing the
matic pressure means is employed for initiating move
forming tools employed in the device of FIGURE 1 hav
ment of the forming tool which commences the operation
ing formed approximately 85% of the dimple shape;
cycle. A trigger mechanism, following the movement of 50 FIGURE 7 is an enlarged sectional view showing the
[the forming tool, operates a valve switch means which
forming tools shown in FIGURE 1 completing a dimple
connects a high pneumatic pressure means to augment the
{applied low pressure thus further activating the forming
forming operation;
FIGURE 8 is a side elevational view in section show
tool. The additional pressure forces the forming tool to
ing another embodiment of the present invention for
complete the forming operation. It is to be understood 55 shaping rigid sheet material; and
that the pressure system employed may take a form other
FIGURE 9 is a side elevational view in section showing
than pneumatic such as ‘for example a steam or hydraulic
the embodiment of FIGURE 8 at the completion of the
?uid system.
shaping operation.
The action of the trigger mechanism and therefore the
Referring to FIGURE :1 and FIGURE 4, a pair of
60
activation of the valve switch means is dependent upon
forming tool means 1d and 11 are provided for shaping
the material temperature during the initial cycle of op
a sheet of rigid material 12. The forming tool means
eration since ‘as the material becomes more pliable, the
are con?gured in such a manner that their co-action when
forming tool is pressed further against the material. If
activated produces a desired shape in the material.
the material has not been properly thermally conditioned,
A conventional heating means, such as electrical heat
ing devices 13 associated with the forming tool means,
the rigidity of the material will prevent the activation of
are employed for thermally conditioning the material by
the trigger mechanism.
generating heat via the forming tool means into the sur
Thus, it can be seen that the application of high pneu
rounding material area. The heating devices are elec
matic pressure will not occur until the thermally condi
trically connected to boxes such as junction box 14 by
tioned material has become pliable.
70
means of a connector lead 15. An electrical source (not
Exhaust means are provided for disposing of the air
shown) is connected to the junction box via cable 16
which forced the forming tool to complete the operation
3,080,473
3
which provides the required high current for generating
tending therethrough' and forming a right angle within the ‘
heat to the material. 'Each junction box is provided with
a start button 17 and stop button’ 18 for controlling the
operation of the heating devices.
. V
center of the low pressure valve.
_
.
The piston 3a is activated by’ energizing solenoid 48
V
which arranges passage 55 so that pneumatic pressure is '
The forming tool means are attached to a base assem
applied through a coupling arrangement 56 extending
bly 19 having an open .cut-out portion represented by the
numeral 20‘. The forming tool means are located within
55 is further arranged to‘ exhaust pneumatic pressure
the open cut-out portion so that material 12 may be
within operating chamber ‘29 by connecting the coupling
passed into engagement therewith.
arrangement to an exhaust outlet 57 whenever solenoid
through casing 32 into operating chamber 29. Passage
.
A tubular or cylindrical passage 21 is provided inrthe 10 48 is de-energized. Disposing of accumulated pressure
' base assembly extending from the top thereof to the open
allows the piston to return to its rest position.
cut-out portion. A shaft portion 22 of the formingrtool
A‘ high pressure valve'58 is coupled between the high
means 10 passes through the cylindrical passage and is
pneumatic pressure source 42 and the low pressure valve
resiliently mounted therein by means of a spring 23 com—
46 and is constructed similarly thereto. The high pres
pressed ‘between a bushing 24 affixed to the base assem 15 sure valve is operated by a solenoid 59‘ which when ener
bly and a retaining ring 25 ail‘ixed to the shaft portion.
gized applies high pneumatic pressure directly to the low
A top bushing 26, af?xed to the top portion of the cylin
pressure valve to advance the piston. De-energizing of
drioal passage co-acts with bushing 24 to guide the shaft ‘ solenoid 59 causes the high pressure valve to disconnect
portion perpendicularly to the material 12..
the high pressure from the piston cylinder.
Forming tool means Ill may be moved longitudinally
A probe so ispprovided on the end of the'extension arm
within the cylindrical passage to effect engagement with
which passes through the outer casing at the end of a
the material by any conventional means. A cylinder 27,
piston stroke. The probe is employed for tripping switch
having a pair of operating chambers 2d and 29' and‘ a
5% which in turn breaks electrical contact to solenoid 43
piston 60 within operating chamber 29‘, is employed in
and causes its de-energization.
the device of FIGURE 1 which is suitable for activating
the forming’ tool means. The operating chambers are
separated by ‘a casing wall 31 ofra casing 32 which forms
operating chamber 29‘. The piston located in operating
, 7
v7
_
A trigger mechanism, represented by the numeral 62,
is mounted on the front. of the base assembly adjacent
the shaft portion and is shown more clearly in FIGURE
2 and FIGURE 3. The trigger mechanismVi-s employed
for controlling the operation of solenoidr59 and com~
chamber 29 is attached to an extension arm 33'ivhich
passes through the casing wall into the operating chamber 30 prises a plunger 63 slidably mounted in a groove 64 and
28 via a sleeve 34.
i
7
engageable with a set screw 65.
Operating chamber 28 is formed by an outer casing 35
7
One end of the lower cam means extends beyond the
7 Outer casing to engage plunger 63. The plunger is
which has attached thereto‘ a ?at top cam means 36.
Cylindrical passage 21 extends through the base assembly
moved longitudinally in groove. 64 by the pivotal action
to operating chamber 2%}. A lower cam means 37 is piv 35 of the lower cam means.
otally mounted within operating chamber 28 and is pro
In this manner, the movement
of the‘plunger follows the ‘movement of forming tool
videdwith a ?at cam surface 38 and an angular cam
surface '39 which is engageable with the shaft portion of
the forming tool means.
means It). '
A bellcrank 66, af?xed to set screw ‘as, pivots when’
the set screw is engaged by the plunger so that its move
A?ixed to extension arm'33 within operating chamber 40 ment is transferred via a push-rod 67 toactivate a switch
28 is a pair of rollers 44) and 41 arranged to ride on the‘
68 which controls the high‘ pressure valve solenoid. ‘A
top cam means and the ?at cam surface, respectively.
spring 6% is provided for returning the bellcranlt and the
Piston movement is rectilinear on the flat top cam means
plunger to their initial’positions. An adjustable microm- . V
36. ‘Progression of piston 30 forces the lower cam means
to pivot. Inasmuch as angular cam surface 3%‘ is in
eter 70' mounted on the base assembly is employed for
engagement with the shaft portion, any pivotal move
tripped, prior to operation. ~
manually controlling the point at which the switch isv
ment of lower cam means 37 positions the shaft portion
In FIGURES 5-7, a dimpleforming tool means is
shown for forming a dimple in'she'et material during three
stages of operation. FIGURE 5v shows the initial engage
ment of'forming tool means ‘1d! and 11 with the material
longitudinally in the cylindrical passage and thereby posi
tions forming tool means 10 in a perpendicular relation
ship to the material.
'
Piston movement is effected by employing a pressure
system such as a pneumatic pressure system for example.
High pneumatic pressure is provided from any suitable
source (not shown) through a system-network repre
sented by an ‘arrow 42‘.
.
The pneumatic system comprises a low pneumatic pres
sure regulator means 43 having a gage 44; for indicating
' llil when activated by the low pneumatic pressure means
to form approximately 15% of the dimple. A pilot nub
7-1 and a receptacle 72'. are provided as a means for pilot
ing the forming tool.
55
'
a
.
'Heat, generated by a pluralityof heating elements such
as element 73 affixed to'heating device l3,v is. applied to.
thermaterial.
‘ l
.
the pneumatic pressure applied to the subsequent systeml ~
V In FIGURE 6; the material has been thermally condi
A check valve 45 is coupled to ‘the low pneumatic pres~
tioned to the yield point where it has become work-able.
- suremeans through which the low pressure passes. The 60 The continued application of low pressure to the form- ,
check valve serves‘to maintain the pneumatic pressure
ing tool has effected approximately 85 %' of the dimple.
?ow with" as little ?uctuation as possible. A low pres ‘ 7 It should be noted that the partially formed dimple has
sure valve 46 is connected tothe check valve via a. pneu~
been accomplished only'as the material becomes more
matic'reservoir 47. The low pressure valve is electri
and more pliable and that noportion of the material ‘has
< cally operated by means of a solenoid d3. ' The‘ solenoid
been formedwhich has not been thermally prepared. .
is connected to ground via lead 49‘ and‘ connected to a
7 FIGURE 7 shows a completed dimple formed in the
‘positive source of potential (not shown) via a switch ‘50,
. a foot pedal switch means 51, and a lead 52.
vmaterial ‘as .a result ‘of applying high pneumatic pressure
' when the material has been properly conditioned. Since
the application of high pressure occurs when the material '
ranged to form a movable core within the solenoid 4d
70 is' thoroughly conditioned to be worked, the completed a
A rod 53,"composed of maghetizable material,’ is ari
‘ so that when the solenoid is energized the rod will move.
Attached to the rod on one end is a pivotal extension
54 which; is’ attached to the low pressure valve yandmo‘vs
I able therewith.
'
form is’notsusceptiblef to cracking due to brittleness as‘a
result of using conventional methods and apparatus.
The embodiment of the present invention, 'as shown in
' FIGURES 8 ‘and 9, shows a pair of forming tool means
The, low pressure, valve is provided with passage 55 ex? 75 74 and 75 con?gured to produce a Iight-aQsIed‘foId, or
l
3,080,473
5
bend in rigid sheet material 76. Heating elements, such
6
23 which forces plunger 22 upward was placed under
as element 77, are embedded in the forming tool near the
compressive force during the travel of the piston 30 to
surface of material engagement. A face plate 78 a?‘ixed
ward the left as shown in FIGURE 4. It is this stored
to forming tool means 75 is made of a hard material, and
is employed as a form to provide a fold in the material
being formed when forming tool means 74 is activated.
mechanical energy which quickly repositions the piston
for the next forming operation.
Sufficient pneumatic pressure is retained in the pneu
matic system and reservoir 47 to permit ef?cient re
Forming tool means 74 is activated by applying pres
activation of piston movement upon another depression
sure to a piston 79 within a cylinder 80. Activation of
of the foot pedal.
the forming tool means 74 compresses a spring 81 located
The pneumatic pressure system employed in FIGURE
within a chamber '82 formed by the forming tool means 10
1 may be used to activate forming tool means '74. Op
74. This arrangement allows an extension 33 to engage
eration of the bellcrank and switch arrangement 91 is the
the material to be formed and to bend this material
same as for the device shown in FIGURE 1.
against the hard face plate 7%. Heating elements 77,
Having described only typical forms of the invention I
such as those embedded in the forming tool, are carried
by the extension so that the material is thermally condi 15 do riot wish to be limited ‘to the specific details herein
set forth, but wish to reserve to myself any variations or
tioned at all times during the forming operation.
modi?cations that may appear to those skilled in the art
In this embodiment of the present invention a plunger
and fall within the scope of the following claims.
84 is resiliently mounted on the forming tool means 74
I claim:
by means of a spring 85 and a mounting bar ‘86. Threads
1. A forming device for shaping a material having a
67 are provided on one end of the plunger to receive a
certain yield point at which the material becomes fully
nut 88 and spacer 89' so that the plunger 84 may slide
pliable comprising, the combination of a base assembly,
longitudinally through a hole (not shown) in the mount
ing bar.
a forming tool movable on the base ‘assembly, means car
noid to energize and is represented by the numeral 91.
relationship to the material for making the material pli
able, activating means carried by the base assembly for
moving the forming tool, a ?uid pressure system connected
ried on the base assembly for supporting the material and
The bellcrank and switch arrangement as described in
the device of FIGURE 1 is used in the embodiment of 25 for cooperating with the tool in shaping the material,
heating elements a?ixed to the ‘forming tool in thermal
FIGURES 8 and 9 to cause the high pressure valve sole
The pneumatic pressure system as described in the
device of FIGURE 1 is used in the embodiment of FIG
URESv 8 and 9 and therefore is not repeated in the draw
mgs.
Actual operation will be described with reference to
FIGURE 4 in which the depression of foot pedal 51 com
pletes an electrical circuit via switch 50 to energize sole
noid 48. Energizing this solenoid draws rod 53: into its
core (not shown) causing low pressure valve 46 to ar
range passage 55 so that low pneumatic pressure ?owing
through low pneumatic pressure regulator means 43 is
applied to cylinder 27. As pneumatic pressure is applied
to chamber 29, piston 30 is forced to move within the
cylinder. Roller 41 connected to extension arm 33 fol
lows this movement by riding on ?at cam surface 38.
This action causes cam means 37 to pivot. Inasmuch as
to the activating means comprising a low ?uid pressure
valve and a high ?uid pressure valve, the low ?uid pres
sure valve adapted to initiate the material forming cycle
when the material is partially pliable, a trigger mechanism
arranged to continuously follow the movement of the
forming tool during the forming cycle, and the electrical
means actuated by trigger mechanism and adapted to op
erate the high ?uid pressure valve so that pressure is
applied to the activating means in response to the fully
pliable condition of the material, and means responsive
to the movement of said forming tool for exhausting
the high pressure being applied to said tool.
2. In a thermal device for forming rigid material hav
ing a certain yield point at which the material becomes
fully pliable the combination comprising, a low pneumatic
shaft portion 22 rides against angular cam surface 39,
the shaft portion is forced downward against the tension 45 pressure regulator means, a high pneumatic pressure
means, a solenoid operated low pressure valve connected
of spring 23. This action engages forming tool means 10
to the low pneumatic pressure regulator means, a solenoid
with the material (not shown).
operated high pressure valve connected to the high pneu~
Heat generated by the heating elements 13, shown in
FIGURE 1, embedded in the forming tool means is trans
mitted to the material 12. As the rigid material becomes
more pliable due to this heating, the forming tool means
is lowered still further since the low pneumatic pressure
matic pressure means and further connected to a line be
tween the low pressure valve and the low pneumatic
pressure regulator means, a check valve connected to the
low pneumatic pressure regulator means, a pneumatic
reservoir connected between the check valve and the high
pressure valve, a forming tool means for shaping the
ment of the forming tool means, eventually engages set
material, means for supporting the material and for co
55
screw 65 attached to bellcrank 66. As the plunger moves
is still being applied. Plunger '63 following the move
down, the bcllcrank pivots and acts against spring 69.
Push-rod ‘67, carried by the bellcrank, engages switch ‘68
operating with the tool in shaping the material, thermal
elements a?'ixed to the forming tool means for condition
mg the material to a pliable condition, means electrically
activating the low pressure valve to initiate the actuation
solenoid 59 causes high pressure valve 58 to arrange its 60 of the forming tool means into engagement with the ma
which closes an electrical circuit. The closing of switch
68 applies positive potential to solenoid 59. Energizing
passage 92 to permit the application of high pneumatic
terial, a trigger mechanism continuously movable with
the forming tool means when the material becomes par
tially pliable, adjusting means for regulating the move
ment limits of the trigger mechanism, means for electri
piston to complete its stroke within the cylinder and com
cally activating the high pressure valve in response to
65
plete the forming operation. The completion of piston
the trigger mechanism movement whereby the forming
stroke causes probe 60 to open switch 50 which causes
tool means completes the forming of the material when
solenoid 48 to de-energize. This» action causes passage
the material is fully pliable, means responsive to the move
55 to connect cylinder 27 with exhaust outlet 57. The
ment of the forming tool means for electrically discon
accumulated pneumatic pressure within cylinder 27 may 70 nectmg application of high pneumatic pressure from
escape and thereby allow the piston to return to its initial
the forming tool, and an exhaust means for dissipating
position. Piston 30 returns to its initial position by rea
accumulated pneumatic pressure when the high pneumatic
son of spring 23 forcing plunger 22 upward and hence
pressure -is disconnected from the forming tool means.
pressure to piston 3%‘ via low pressure valve 46.
The application of high pneumatic pressure forces the
cam means 37 is pivoted clockwise so that rollers 41
3. Apparatus for heat-forming a metal element com
travel toward the right to‘ reposition the piston. Spring 75 prising titanium or like materials, said apparatus compris
3,080,473.“,
7
8i
ing mutually opposed forming dies, means operatively
erating said second valve, a plunger contacted at the
loose end of said cam member, said plunger engageable
' associated with said dies for heating the metal element
to be formed there/‘between to predetermined working
temperature, means operable during such heating to ap
ply pressure to the element between such dies with arforce
materially less than the force required for completing
the forming operation, causing detectable initial deforma
with a ?rst switch means, said ?rst switch means operat
ing said second solenoid foroperating said second valve
7, to control vsaid high pressure means, said extension arm
having means a?ixed thereto for operating a second switch
means, said second switch means operating said ?rst sole
tion thereof when said temperature is reached, means
noid to operate said ?uid valve for exhausting the ?uid
‘adapted to detect such initial deformation, and means con
from said ?uid operating chamber, through said exhaust
trolled by said latter means and operable in response to 10 » port, and said ?rst solenoid initially actuated by a
said detection to increase said force materially to a value
manual control.
7
effective to complete the forming operation.
4. Apparatus for thermally and physically shaping ma
7. A forming device for shaping material having a cer
tain yield point at which the material becomes pliable
terial having a certain yield point comprising a movable
as de?ned in claim 6 wherein said ?rst switch means has
forming tool, a support vfor said material cooperating 15 associated therewith an adjustable micrometer means for
with said tool in shaping the material,’ heating elements
accurately controlling the operation of said switch with
associated with said tool for transmitting heat to said
respect to the movement of said shaft portion and said
material, a pressure operated means moving said tool, a
forming tool.
low pressure means and a high pressure means associated
8. A forming device for shaping material having a cer
with said pressure operated means, said pressure operated
tain yield point at which/the material becomes pliable
means ?rst activated by the low pressure means, a ?rst
means responsive to the movement of said tool for sensing ,
the plasticity of said material, said ?rst responsive means
initiating the actuation of said high pressure means when
comprising a heated tool, a support cooperating with said
tool in shaping said material, a ?uidoperating piston for ‘
moving said tool against said material a piston rod con
nected to said piston and having a forming, head con
said certain yield point is reached, said ?rst responsive 25' nected to the free end thereof, said tool reciprocably
mounted in said head and resiliently urged downwardly
means connected to said pressure operated means, a sec
ond responsive means also connected to said pressure
operated means, said second means responsive to the
and restrained within said head, a switching means as
sociat'ed with said device for increasing the ?uid pressure
movement of said tool for sensing the ?nal shape of saidv
operating said piston, said switch means comprising an ad
material and said second means exhausting the high pres 30 justable set screw attached to said forming head and a
sure from said pressure operated means.
'
mechanically actuated electrical switch means connected
5. Apparatus for thermally and physically shaping ma-'
to said support means, said set screw actuating said
terial having a certain yield point as de?ned in claim 4
switching means as said tool and said forminglhead re
wherein said first responsive means has associated there
forced'downwardly toward said support, the point of said
with an adjustable micrometer for manually controlling 35 .movement at which said switching means is .autuated
the point during the movement of said tool at which
being accurately adjustable by means of said set screw.
said material has attained its ?nal shape. '
6. A forming device for shaping a material having
ReferencesCited in the ?le of this patent
a certain yield point at which the material becomes'plia
UNITED STATES PATENTS
ble comprising, a forming tool, a support for cooperating, 40
with said ‘tool in shaping the material, heating elements
associated with said tool, said forming tool having a shaft
portion attached thereto, said shaft portion spring biased
to retract said tool from said support, a cam member
465,089
1,174,446
1,261,943
1,295,048
Ries _________________ __ Dec. 15,
'Rietzel ________________ __ Mar. 7,
Lashar _______________ __ Apr. 9,
Macdonald ___________ __ Feb. 18,
1891
1916
1918
1919
1,848,271
having an angular cam surface engaging the end portion
1,951,426
of said shaft, said cam pivotally connected to said device,
2,331,537
a piston positioned within a ?uid operating, chamber,
2,395,849
said chamber being a?‘ixed tosaid device, an extension
2,405,033
arm integrally‘c'onnected to said piston by one end there
of and having a?‘ixed to the opposite end thereof a roller, 50 2,407 ,314
Phelps _______________ __ Mar. 8, 1932
Littler _; ________ __‘_____ Mar.'20, 1934
Mason _______________ “Sept. 10, 1946
said roller engageable with said cam and with a ?at cam
2,449,247
Paucek __ ___________ __ Sept. 14, 1948
surface integrally al?xed to said device, said ?uid op
erating chamber having connected thereto a ?rst valve,
said ?rst valve having an exhaust port associated there
with, said valve controlled by a ?rst solenoid, a ?uid’
2,459,047
2,460,519
2,592,672
2,737,224
Scharf _______________ __ Jan. 11,,
Marchant ______________ __ Feb. 1,
Fischer ______________ 2. Apr. 15,
Jones __, _____________ __ Mar, 6,
pressure system connected to said valve having a low
pressure supply means and a high pressure supply
means, a second valve disposed in said high pressure
means for controlling the emission of high pressure ?uid
to said ?uid operating chamber, a second solenoid op
2,743,933
Clark _______________ __ Oct. 12, 1943
Collom et al ___________ __ Mar. 5, 1946
Grimes _______________ __ July 30, 1946
7
1949
1949
1952
1956
Baines ________ a. ______ _._ May'l, 1956.
2,852,060’ r
Gunther _____________ __ Sept. 16, 1958
OTHER REFERENCES
Metal Industry-The disclosure on page 213 for‘ Sept.
13, 1946.
'
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