This patent document describes a method and apparatus for vacuum die casting. It involves using a two-part hood or enclosure that surrounds the die members. The hood is evacuated prior to each casting operation to produce smooth, non-porous castings. The hood sections separate along the parting line between the die members. Passages allow coolant to circulate through the die members, and a manifold in the hood accommodates different inlet/outlet connections needed for different die member configurations.

1. * GB780126 (A)
Description: GB780126 (A) ? 1957-07-31
Method of and apparatus for die casting under vacuum
Description of GB780126 (A)
PATENT SPECIFICATION
Date of Application and filing Complete Specification: Jan. 7, 1955.
780,126 No. 517/55.
Complete Specification Published: July 31, 1957.
Index at acceptance:-Class 83(1), F(1C010:D:1H:2A:11C:11U:18).
International Classification:-B22c, d.
COMPLETE SPECIFICATION
Method of and Apparatus for Die Casting under Vacuum I, DAVID MILTON
MORGENSTERN,:I Citizen of the United States of America, of 21111
Edgeeliff Boulevard, Euclid, State of Ohio, United States of America,
do hereby declare the invention, for which I pray that a patent may be
granted to me, and the method by which it is to be performed, to be
particularly described in and by the 'following statement:-
This invention is concerned with the trend in the art of die casting
which has to do with the evacuation of the die cavity prior to each
casting operation for the obvious purpose of producing smooth surface
castings that are substantially non-porous and of increased density
throughout. This method is commonly referred to as vacuum die casting.
Although the desirability of such a method has long been recognized,
means for carrying it out in an economical and commercial way have
heretofore been lacking.
The measure of success in the production of high quality castings by
this method depends upon the degree of vacuum that can be created and
maintained in the die cavity until supplanted by the molten material;
and the practicability of the method from the standpoint of
manufacture or mass - production, depends largely upon the speed at
which the die cavity and communicating spaces can be evacuated to the
required extent.
The invention hence consists of the improvement, in the method of die
casting wherein molten material is delivered to a die cavity defined

2. by and between two relatively movable die members, of the steps of
relatively moving the die members initially into closely spaced
relation to each other and enveloping the die members in a
substantially airtight enclosure; evacuating the enclosure while the
die members are in the said spaced ..S relation to each other; moving
the die members into engagement with each other to close the die
cavity while the enclosure is in evacuated condition; delivering
molten material to the die cavity; chilling 50 the material to
solidify it; and opening the enclosure in order to gain access to the
die members and moving the die members apart for the removal of the
casting. 55 The invention further consists of the combination, in a
die casting machine of the type including die members that are
relatively movable toward and from each other and by and between which
a die 60 cavity is defined, the cavity being substantially closed and
conditioned to receive a charge of molten material when the members
are in engagement with each other, and power mechanism for effecting
65 relative movement between the die members, of the following:
equipment including a separable enclosure enveloping the die members
and made up of two parts that are movable with 70 the respective die
members, each said part being sealed against leakage at the joint
between it and the die member surrounded by it, normally extended
sealing means for closing the joint 75 between the two parts of the
enclosure when the two parts are relatively near each other and before
the two parts finally meet, means evacuating the enclosure when
initially sealed by the seal- 8 ing means, and during which evacuation
the power mechanism functions relatively to move the die members
together to close the die cavity in preparation to receive a charge of
molten material. 85 As is well known in the art, it is necessary to
change one set of die members for another each time a machine is set
up for producing a different kind or size of article, and die members
having go90 780,126 liquid cooling facilities, as many have, may
differ from one another in the number and location of inlet and outlet
connections for the coolant.
$ The equipment of my invention includes a two-part hood or enclosure
that surrounds the die members, the parts whereof separate
substantially on the parting line between said members.
In order that the invention may be clearly understood, reference will
now be made to the accompanying drawings in which one constructional
form is illustrated, by way of example, and in which:
Fig. 1 is a fragmentary sectional side elevation of a die casting
apparatus incorporating my improvements, showing the die members
slightly separated and the hood sealed and evacuated, as indicated by
the condition of the gasket; Fig. 2 is a section substantially on the
line 2-2 of Fig. 1, with certain parts beyond the plane of section

3. omitted; Figs. 3, 4 and 5 are enlarged sectional details of the hood
in the region of the sealing gasket, the respective views showing the
condition of the gasket when the die members are slightly separated
and before the hood is evacuated; after evacuation of the hood, as in
Figs. 1 and 10, and when the die members are in contact with each
other; Figs. 6 and 7 are sectional details, at right angles to each
other. of a coolant manifold that is incorporated in the hood, Fig. 7
being taken on the line 7-7 of Fig. 6; Fig. 8 is a frapmentarv
sectional side elevation of the apparatus as it appears between cycles
of operation; Fig. 9 is a similar view, showing the die members in
contact with each other and with molten material displaced from the
charging cylinder into the die cavity, and Fig. 10 is a diagrammatie
representation of the apparatus and the system of controls by which a
cycle of operation is rendered automatic, the parts being shown, as in
Fig. 1, in the positions they occupy at the time of evacuation of the
hood and the spaces communicating therewith.
The die casting machine, generally, is of conventional design and
construction.
It includes the usual stationary die plate 1 and movable die plate 2,
the latter being slidable along rods 4 that are eonnected at their
forward ends in the customary manner to the stationary die plate 1.
An enclosure or hood. designated generally by the reference numeral 5,
constitutes an important part of my equipment and it comprises a
stationary section 6 and a movable section 7. Each of the sections
includes top, bottom and side walls, and extendino- about the open
side of the se:ti-in 6 is an inwardly extending flange 9. to the outer
surface of the inner edge portion of which is seeured the
oearresponding portion of a 70 gasket 10. As best appears from Fig. 2,
the gasket 10, as well as the cross seetional shape of the hood is
rectangular.
This gasket is desirabl made of a very durable, flexible plastie
material that wil175 withstand, for a (-,llsiderable length of time,
the high templatures to which the gasket is subjeeted without its
effectiveness becoming imnpaired. A material especially suited to the
purpose is one 80 known to the trade as Neoprene. When relaxed, the
gasket assumes a dished shape, as illustrated in Figs. 3 and 8. A
flange 12 surrounds and extends outwardly from the open side of the
hood85 section 7. and its smooth forward face provides a seat for
the.asket 10. The hood seetions 6 and 7 include base plates 14 and 15,
respectively, and the ends of the sections adjacent said plates are
pro-90 vided with the respective flanges 16 and 17 that are secured by
screws 18. to said base plates. The j tilts between the hood sections
and base plates are shown as sealed by gaskets 20 The hood sections95
are fastened to the die plates 1 and 2 by clamps 22.

4. Located within the hood. and secured to the base plates 14 and 15 h-by
a suitable number of screws 23 are a stationary die 100 member 24 and
a movalle die member 25.
Ordinarilyv. in the absence of the hood or enclosure, these die
members would be attached directly to the die plates 1 and 2. The
adjacent faces of the opposed die 105 members are contoured to define
between them die cavities 26 that communicate, through runnmmers 27.
with a sprue 28. By mechanism later to be described. the die plate 2
is moved toward and from the die 110 plate 1, and in order to insure
proper registration of the die members as they approach each cother.
Ioeating pins or dowels 30q that are 'carried by the movable die
member 25. enter bushed recesses 31 115 in the stationary die member
24.
The ejecting mechanism by which castings are dislodeed from the
movable die member, ineludes a head 35 that is located to the rear of
the body portion of 120 said member and t,-, which are secured
ejecting pins o6. These pins extend through bores in tlme movable die
member and when the di,-,re in condition to receive a char -- -,4
m,!tcn material. the 125 forward ends 4f.i pins. arie sulhtaitiallv
flush with thel exp-,ed surface of the movable die memnr Thile
retraction of the ejecting pins to bring albout this condition is
effecte4 hi push rods 37 that 130 780,126 are fastened to the head 35
and are guided through bores of the movable die member.
As the movable die member 25 closely approaches the stationary die
member 24, the forward ends of the push rods 37 engage the latter die
member thereby to arrest forward movement of the head 35 and
consequently of the ejecting pins 36, while the die member 25
completes its forward travel.
When the die plate 2, with the parts carried thereby, is being
retracted to the position shown in Fig. 8, actuators or plungers 40,
that are slidably supported by said die plate 2, engage the usual
stationary abutment 41, thereby to arrest further rearward movement of
the head and the ejecting pins 36, along with the push rods 37. It is
this action that causes the casting to be dislodged from the movable
die member.
There is provided sealing and lubricating means for the actuators or
plungers 40. These plungers are guided in bushings 43 that fit tightly
within holes in the die plate 2. Intermediate the ends of the bore of
each bushing 43 is a relatively wide circumferential channel within
which a ring 44 of felt or other absorbent material is confined, the
same being saturated With a lubricating oil. Within circumferential
grooves beyond the ends of the ring 44 are confined 0-rings 46 that
seal the bushing against leakage about the plunger 40 and serve as
wipers to confine the oil to the region between said 0-rings.

5. An annular groove in the inner end of each bushing 43 contains an
O-ring or other suitable packing means 47 for preventing leakage
inwardly across the end of the bushing and about the corresponding
plunger and through the hole in the base plate 15 through which the
inner end of the plunger projects. Located forwardly of the stationary
die plate 1 is a pot or crucible 50, common to die casting machines
employed for handling zinc, lead, or tin alloys, or other materials
having similar melting and solidifying characteristics. Suitable
heating means, such as a gas burner (not shown) is situated in heat
exchange relation to the crucible for keeping the contents thereof in
molten condition.
Supported in the usual way within the crucible 50 is a charging
chamber or cylinder 52 that communicates, through a port 53, with the
crucible 50, and, through a so-called gooseneck 54 and nozzle 55, with
the sprue 28 of the stationary die member 24, the die plate 1 and the
base plate 14 being apertlured for the acconunmmodation of the nozzle.
A charging piston 58 is reeiprocable in the cylinder 52 and the rod 59
thereof has connection, through the usual coupling 60, with the rod 61
of a piston 62 that operates in a cylinder 63. This latter cylinder is
a part of a pressure fluid system, desirably hydraulic, hereinafter70
to be described, and by means of which various parts of the apparatus
are operated.
The feeding means for the molten material, as so far described, will
be75 recognized as conventional in character, and to adapt it to my
purpose, a valve 65 is employed for closing the port 53 through which
the crucible 50 and the charging cylinder 52 communicate. This 80S
valve is carried by the lower end of a lever 66 that is pivotally
connected at its upper end to the rod 68 of a piston 69 that operates
in a cylinder 70. The lever 66 is fulcrumed intermediate its ends in
a85 bracket 72 that is shown as extending laterally from the charging
cylinder 52.
The cylinder 70 is also included in the pressure fluid system referred
to above.
With reference to Fig. 10, there is a 90 further cylinder 75 that
forms a part of said system and is a constituent of the power means
for reciprocating the movable die plate 2 and the parts carried
thereby. Working within the cylinder 7595 is a piston 76, the rod 77
of which has operative connection, through links 78, with toggle
joints 80. Each toggle joint is pivotally connected at one of its ends
to the movable die plate 2 and at its 100 opposite end to a stationary
part 83 of the die casting machine.
In Fig. 10 is also shown a so-called vacuum tank or enclosure 85.
Communication between this tank and the hood 5 105 is had through
pipes 86 and 87, shown as joined through two branches of a T 88.

6. The other branch of said T has connection with a valve 90 that is
biased, as by a spring 91, to open position thereby to 110 place the
interior of the hood 5 in communication with the atmosphere. The valve
90 is closed by means of a solenoid 92. The pipe 86 is communicatively
connected, through a T 94 and a pipe 95, 115 with a suction pump 96,
shown as driven by an electric motor 97. Valves 98 and 99 are located
in the pipe 86 on opposite sides of the T 94. These valves are biased
to open position and are adapted to be 120 closed by means of pressure
fluid under the control of the respective solenoids 100 and 101. When
said solenoids are deenergized, the pressure fluid has access to said
valves and holds them closed, as will 125 hereinafter more fully
appear.
By means of the suction pump 96, a vacuum of relatively high degree,
say approximately 29 inches, is maintained in the tank 85. The
interior of the hood 5 130 780,126 may immediately be placed in
comrmuni ation with the tank or enclosure s., as well as with the
suction pump 96, by opening the valves 98 and 99. As will later
appear. when approximate equilibrium is attained between the hood and
tank, the valve 98 will he closed and communication with the hood will
be confined to the suction pump 96.. This continues through 10the
casting operation, after which the valve 99 will he closed and the
valves 98 and 90 opened, resulting in the reestablishment of
communication between the pump and tank, and the opening of the space
enclosed by the hood 5 to the atmosphere. These several steps are
included in a cycle of operation later to be described.
Before describing the operating and control system by which a cycle of
operation is automatically carried out. I may explain that it is
common to provide passages, such as those designated 103, in either or
both of the die members, through which water or other suitable liquid
coolant may be circulated. Also, for the production of different sizes
and styles of castings, different die members have to be used. Some
die members.
because of the shape and character of the die cavities, have to be
provided with circulating passages for the coolant that may have a
plurality of inlet and outlet connections. To provide for these
different possible conditions I include in the hood a manifold
designated 105, sectional details of which constitute Fios. 6 and 7 of
the drawings. The manifold is shown as an elongated body that has
bores 107 and 40108 extending inwvardly from its opposite ends, one
constituting an outlet passage and the other an inlet passage for the
coolant. Ports 109 and 110 lead downwardly from said bores and open
through the bottom of the body, adjacent which said ports are enlarged
and threaded for the reception of the threaded ends of elbow fittings
112. The ports 109 and are controlled by valves 113, the stems of

7. which are threaded through the top of the body in alignment with said
ports.
Each bore 107 and 108 has a hose conneetion at its outer end, that of
the bore 107 being slhownv at 115 in Fig. 6. The manifold is showin as
applied to the hood section 7 immediately to the rear of the flange
12. and one or more of the elbow fittings 112 of the manifold are
adapted to he connected with similar fittings of the underlying die
member througi-h loops :.f tubing designated 116 that are attached
livy unions to the fittins of the manifold and die member. Access to
the interior of the hood. for making the foregoing conneetions and for
other purposes. is had through one o-r me handl hole-. such as that
desiamited 11-. tie sae being shwv as liv'at- d n ilc top wall of thle
section 7. The}iiv i,le is c]os-d by a plate 119. sealed to, the
underlying wall 70 about the hand hole l, a aslket 120.
As previously mentioned, the cylinders 63, 70 and 75 are hneluded in a
pressure fluid systenm. desi.ayl hvlcraulie. In the cease of a
hydraulic system. there is the 75 usual tank from whi-ch the liquid is
drawn and to which it is ricuirnied. A pump.
usually operated by an electric motor, withdraws the liquid from the
tank and delivers it at the required pressure to the80 cylinders.
under the control of suitable valves. Since hy-draulic systems of this
sort are so well known it is regarded unnecessary to show the tank and
pump and the part of the system involving them. 85 The omission of
these parts simplifies considerably the dia'ra) of Fig. 10. This view
does include. hi xwever. hydraulic valves. preferably -l the spool
type. for controlling the adnii-ion of the liquid90 to the various
cylinders. adll the escape of the liquid thereArom Associated with the
respective cylinders 6t3 and 70 are valves 125 and 123. whlile two
v-alv-es, 127 and 128s. are assowit,1 with the cylindler 95 for a
reason that will] presently appear.
It may be explainedl at this point that relatively large sp,,l ralves
are used in conjunction with 1l, t lindlers 63 and 75.
because these lx ti are required to 100 handle liquid in eowisiderable
volume, this heinm indicated by ti, facet that. in practice, the
condfluits,a, pipes used therewith are in excess of,ie inch. Onl thle
other hand. a relativel- small spool valve is 105 used with the
eylinder 70. the pipes or conduits leading to and from the same being,
in practice. ltout one-half inch.
In the digranmmalea view of Fig. 10, however, relative sizes or
proportions are 110 ignored in favor of c]arity of illustration.
Beeause of the size ctf the valves 125, 127 and 128 an apprecill l,
molunt of power is required to shift tile spools thereof.
For this puirp,:,e I:aploay a pressure 115s fluid system. preferab l
pneumatic. Such system inhvolves, e-ide- a motor driven air pump or

8. '-mpres-or (not shown), pilot valves dvesimt; d 130. 131 and 132,
assoeiated, respewqicly with the larger 120 hy-drautlie yah-es 12.5.
127 and 128. Since hydraulic valve 12 is considerably smaller than
tlh,-:,t1s it requires less power to shift its -pl Consequently the
spool of this ire can readily be 125 moved in one dietirn byL a
spring, and in the opposite -ire-tion by a solenoid.
The solenoid for (,periating the hydraulic valve 126. and those used
to actuate the pilot valves 130. 131 and 132, will be 130 cylinder 75
and move the piston 76 therein to approximately the position shown in
Fig. 10 which disposes the movable die member 25 in closely spaced
relation to the stationary die member 24. At that 70 moment a
so-called "die cracking limit switch" 155 is closed by a cam 156 that
is shown as connected, through a rod 157, to the piston 76. This
establishes a circuit designated 160 that includes a solenoid75 161.
This solenoid, now being energized, shifts the spool of the pilot
valve 132 to a position that results in the delivery of compressed air
to the right hand end of the hydraulic valve 128, shifting the 80
latter valve to the position shown which results in cutting off the
supply of pressure fluid to the left hand end of the cylinder 75. It
will be observed from Fig.
that the liquid from the right hand end 85 of the cylinder 75, in
advance of the piston 76, is permitted to pass through the valve 127
and on to the tank or reservoir of the system. The present electric
circuit 160 includes, also, a circuit 90 closer 162 that is biased to
closed position.
It will be seen from the foregoing that, upon closing of the die
cracking limit switch 155, the piston 76 is relieved of the impelling
influence of the pressure 95 fluid. However, through momentum of the
moving parts, the piston will coast for a slight distance and move the
cam 156 far enough to close what may be termed a "die cracked limit
switch", 100 designated 163. This switch closes a circuit 164 which
separates into three branch circuits 165, 166 and 167, the branch 166
including a circuit closer 170 that is biased to closed position and
1OS beyond which said circuit 166 divides into sub-branch circuits 171
and 172.
The branch circuit 165 includes an electric timer 174 of conventional
type which has operative connection with the 110 previously mentioned
circuit closer 162 that is in the circuit 160. The timer, upon being
energized, after an interval of time for which it is set, functions to
open said circuit closer 162. However, 115 during this interval of
time, several things occur. It will be observed that the presently
closed sub-branch circuit 171 contains the solenoid 92. Accordingly
this solenoid is energized to close valve 90. 120 It should be
remembered that, with the dies in "cracked" relation, the sections 6

9. and 7 of the hood 5 are close enough together to seal the joint
between said sections (see Figs. 3 and 4). It will 125 further be
observed that the sub-branch circuit 172 includes a solenoid 175
which, when energized, conditions the hydraulic valve 126 to direct
pressure fluid into the left hand end of the cylinder 70 and 130
designated by reference characters in the course of the following
description. Also, the electric circuits, timers, and other devices
involved in the operating and control system will be introduced as
this description proceeds.
Referring to Fig. 10, the positive and negative sides of the circuit
that supplies current to the system are designated, respectively, 135
and 136. In the former is the main switch 137, the closing of which
conditions the apparatus for operation by completing a circuit
designated 140. This latter circuit includes the solenoid 100,
hereinbefore described as controlling the operation of the valve 98.
It is clear from the illustration that the valve 98 is biased to open
position and is closed when pressure fluid, such as compressed air, is
admitted to the actuating part of the valve under the control of a
pilot valve of the spool type designated 141. This pilot valve is
biased to open position by a spring 142 and is shifted to closed
position by the solenoid 100. Inasmuch as this solenoid is presently
energized by the closing of the main switch 137, the valve 98 opens to
establish communication between the tank 85 and pump 96. Also included
in the circuit 140 is a circuit closer 145 that is biased toward
closed position and is opened in the course of a cycle of operation of
the apparatus, as will presently appear.
146 designates a switch, preferably of the push button type, that,
upon actuation, initiates a cycle of operation of the apparatus. This
switch is, therefore, termed the starting switch. Associated with it
is a holding circuit designated 147 that includes a switch 148 that is
biased to open position and is closed by a solenoid 149 when
energized. As will clearly appear from the diagrammatic representation
of this device, when the starting switch is closed current will be
delivered to the solenoid 149, whereupon switch 148 will be rendered
effective to close the holding circuit, so that the starting switch
may now be released. A circuit designated 150 will thus be closed
which includes a solenoid 151 that operates the pilot valve 131, said
circuit including a circuit closer 152 that is biased toward closed
position.
Upon energization of the solenoid 151, the pilot valve 131 is moved in
a direction to deliver compressed air to the left hand end of the
hydraulic valve 127 and shift 60the spool of the latter to a position
that will result in delivery of pressure fluid to the hydraulic valve
128. At the beginning of this present phase of the operation the valve

10. 128 is in a condition to permit the pressure fluid to pass on to the
780,126 6 780,126 permit return of fluid from the opposite end of the
cylinder to the tank of the hydraulic system. The resultant movement
of the piston 69 causes the valve 65 to close the inlet port of the
charging cylinder 52 so tlhat, when the hood and die cavity are as
will presently appear.
-aeacuated, there will be no tendency for atmospheric pressure to
displace molten material from the crucible 50 through said port and
commrunicating spaces to the space between the dies.
The branch circeit 167 includes a circuit closer 176 and a switch 177.
the latter being operatively associated with the piston 69. and being
biased to open position. The switch is closed by a thrust element 178
that is carried by the piston when the latter approaches the right
hand end of its stroke (as the parts are viewed in Fig. 10). Beyond
the switch 177, so to speak, the branch circuit 167 divides into
sub-branch circuits 180 and 181. The former sub-branch circuit
includes an 26 electric timer 182 that has operative conneetion, as
indicated in the diagram. with the circuit closer 14. in the circuit
140.
This timer, when energized, will, after a brief interval of time for
which the instrument is set, open the circuit 140, thereby to
deenergize the solenoid 100 and allow the spring 142 to shift the
pilot valve 141 to a position that will effect the closing of the
valve 9.8. In the meantime, the solenoid 101, which is in the
sub-branch circuit 181, will be energized and thereby condition a
pilot valve 184 to cause valve 99, wherewith it is associated, to
open.
At the present time, therefore, the space enclosed by the hood 5 is in
communication solely with the suction pump 96.
While the condition just described prevails, the time interval, for
which the electric timer 174 is set, comnes to an end and the timer
functions to open the circuit 160. This circuit, as will be recalled,
includes the die cracking limit switch 155 and the solenoid 161.
Therefore, said solenoid will be deenergized, 50, whereupon the spring
loaded spool of the pilot valve 132 will shift to the right and cause
similar movement of the corresponding element of the hydraulic valve
128, resulting in delivery of pressure fuid again to the left hand or
rear end of the cylinder 75. As a consequence, the piston 76 will be
moved to the limit of its forward stroke, and the movable die meriber
25 will be brought into contact with the stationary-- die member 24,
thereby to close the die cavity. It should be kept in mind, however,
that the parts are shown in Fig. 10 in the positions they occupy wvhen
the die members are "c'racked" and the hood is evacuated, and not in
the positi, ns Li -t referred to, when the die imenibers ar tc,gether

11. and the die cavity closed, as il1nmlrited in Fig. 9.
Situated inii the ptju1 of the cam 156 is a so-called "die el-ed"
limit switch 185.70 This switch is bi;a-ecl to open position, and is
closed by szild -;iun when the piston 76 reaches the ritirh hand end
of its stroke. as abeoe explained. The switch is in a circiit 1-6 that
divides into75 four branches PS. 189, 190 and 191. The first of these
hraimhes, 188. includes a circuit closer 19:3 i id a solenoid 195.
associated with the previously mentioned pilot valve 130. Said pilbt
valv-e is biasedO80 to a position wherelin it directs compressed air
to Th, lower end of the hydrauLlic valve 12-, thereby to position the
spool of the litter valve so as to direct pressute fluid to the
bottom85 of the eylindlr 63 and lift the piston 62 thereiin.i thereby
effecting retraction of the clarging piston 58. However, when the
svlenod 195 is energized, these conclitions will be reversed and the o
pressure fluid will lie directed to the top of the cylinder 63 thereby
to depress the piston 62 and proje,-t lthe charging piston 58 toward
the hottim of the chargingcylinder 52, resulting in molten material0s
being displaced tihrouglh the gooseneek 54, nozzle 55 into the spae
between the die members.
The branch cir:uit 189 includes an electromagnetic me lnS or solenoid
196,100 that is operatively;a soeiated with the circuit closer 176. VA
ordingly, energization of this solenoid results in opening the circuit
167 and its branches 180 and 181. The branch cirenit 190 includes
anjos electric timer 197, that is operatively connected to the two
previously mentioned circuit closers 170 and 193 and functions, after
a relatively brief interval of time for which the instrument is set,
110 to open the circuit 166. with its branches 171 and 172. and the
circuit 188. In the branch circuit 191 is an electric timer 198 that
has operative connectionll with the circuit closer 152 in the circuit
150.115 Accordingly, a given interval of time after this final circuit
191 is energized, the circuit 150. thirolh which a cycle of operation
is initited, and all other circuits eontrolied ly the starting switch
120 146, will be opened thereby to conclude the cycle.
With the eharame.,nd performance of the control s-ystem in miind, the
operation of the apparatuin y -e revieweld)riefly 125 as ollows: The
p:r irtus is placed in operative condh-,. closing the main switch
1:37. Th!],_ ltishes communication between the uit pump 96 and the
tank 85, it being assumed that the motor 130 780,126 780,126 97 is
energized at al] times the die casting apparatus is in operation. A
cycle is started by momentarily depressing the button 146. The circuit
closed by the starting switch is locked in by the action of solenoid
149 and switch 148, as previously explained. Henceforth, the cycle
progresses automatically. The movable die member is advanced toward
the stationary die member 24 and is stopped with the die members

12. slightly spaced apart or in "cracked" position. The sections of the
hood 5 are brought into a similar relationship and the gasket 10 seals
the joint between them. The valve is closed to shut off communication
between the crucible and charging cylinder and the valve 99 opened.
The opening of the latter valve subjects the interior of the hood to
the relatively high vacuum that prevails in the enclosure or tank 85.
This results in an almost instantaneous evacuation of the hood
including, of course, the die cavity, which is, at this time, in free
communication with the interior of the hood, and immediately
thereafter the valve 98 will close becaune of the opening of the
circuit closer 145 by the timer 182. This action is timed to occur at
about the moment of equilibrium between the hood and tank, and the
hood is now subjected solely to the evacuating action of the pump 96.
While this condition prevails, the movable die member 25 is brought
into contact with the stationary die member 24 to close the die cavity
26, and pressure fluid is delivered to the top of the cylinder 63,
thereby, through the piston 62 and its operative connections with the
charging piston 58, to depress the latter to force molten material
from the cylinder 52 through the intercommunicating passages into the
die cavity. A "chilling" period of required duration now prevails
under the control of the timer 198, and just prior to the termination
of such period the valve 99 closes and the valve 98 reopens. With the
hood 5 now cut off from the suction apparatus, the valve 90 is caused
to open and admit air at atmospheric pressure to the hood. The
electric timer 198 then functions to open all circuits excepting
circuit 140. One result of this is to cause the hydraulic valves 127
and 128 to direct pressure fluid to the forward end of the cylinder 75
so as to retract the piston 76 and allow the fluid from the opposite
end of the cylinder to return to the' tank. As the piston 76 moves
rearwardly it will cause retraction of the die member 25, the opening
of the hood 5, and the actuation of the ejecting mechanism to dislodge
the casting. The parts are thus illustrated in Fig. 8, which view
shows the condition of the apparatus between cycles, with the charging
piston 58 retracted and the valve 65 open.
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* 5.8.23.4; 93p