US2340342A - Typographical casting machine - Google Patents

Description

J. c. PLAsTARAs 2,340,342

TYPOGRAPHICAL CASTING MACHINE Filed Aug. 27, 1941 10 Sheets-Sheet 1 Feb. 1, 1944.l

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:E i l Y TTOENEYS Patented Feb. 1, 1944 TYPOGRAPHICAL CASTING MACHINE James C. Plastaras, Laurelton, N. Y., assignor to Mergenthaler Linotype Company, a corporation of New York Application August 27, 1941, Serial No. 408,456

72 Claims. (Cl. 199-47) This invention relates to typographical casting machines, such as Linotype machines of the general organization represented in U. S. Letters Patent to O. Mergenthaler, No. 436,532, wherein a melting pot or so-called metal pot is arranged to deliver molten metal into a slotted mold and up against a composed line of matrices to produce a type bar or slug bearing on its edge type characters corresponding to the intaglio characters of the matrices.

In these machines, the molten metal is introduced into the mold by means of a spring-actuated pump piston or plunger arranged Within the pot and controlled in its action by a rotary cam which, as well known, makes one complete rotation for each cycle of operation of the machine. The cam is so shaped as normally to maintain the pump plunger in a raised position out of action, and at one point in its circumference is formed with a depression which, at the proper time, permits the plunger to descend more or less gradually and uniformly under the influence of its actuating spring to fill the mold with molten metal for the casting operation. 'Ihe metal pot is formed with a throat having a passage leading upwardly from a well at the bottom of the pot to a mold engaging mouthpiece standing at a height above the level of metal in the pot and,

hence, above the level of the metal in the throat prior to casting.

With this arrangement, upon the descent of the plunger to force metal from the pot into the mold, a large volume of metal has to be displaced to fill the throat before the actual introduction of the metal into the mold; and a corresponding Volume of air is displaced and forced into the mold from the throat and exhausted from the mold as the latter fills with metal. The exhaust of air from the mold has always been troublesome because of the fact that the mold is artificially cooled and some of the air may become trapped by the formation of a film of solidified metal against the Walls of the mold before the mold is completely filled. The air which is trapped in the mold results in the production, of a slug having a porous or spongy texture, rendering it unt for use because of the likelihood of its breaking down or because of its having a defective casting face in the event that air has become trapped in the regions of the intaglio characters punched in the matrices. Moreover, the pressure exerted on the metal by the plunger is not uniform throughout the metal injecting stroke of the plunger, due to the relaxation of the plunger-actuating spring, so that the metal enters the mold under a gradually diminishing pressure and, hence, at a gradually diminishing ve,- locity.

Furthermore, these machines are equipped with molds of different sizes adapted to be selectively brought into use, and the same spring-actuated plunger is relied upon to inject the metal into the mold regardless of its size. Thus, the texture or density of slugs of different sizes is necessarily not uniform; and this condition is further aggravated by reason of the accumulation of metal oxide on the walls of the upper portion of the throat, the oXide deposit choking the .throat passage and decreasing the volume and the time allotted for the operation of the pump plunger, is limited to about one-ninth of the casting cycle, or the time it takes the cam shaft of the machine to -partake of a 40 rotation. This is dueto the fact that the machine parts are 'extremely heavy and in effecting the lookup operations before casting and the matrix distributingY operations after casting heavy springs, cams and, levers are required which for smoothness and 'efficiency of operation with minimum Wear and possibility ofv breakage have to be operated so slowly as to consume the remainder of the casting cycle. Also, regardless of the size of the slug being cast, the casting period remains the same, and while it may be sufficiently long for the solidiiioation of the metal for slugs within a 'small size range, it is so inadequate for the larger size slugs that( when the plunger is suddenly raised at the end of the casting period the back Vdraft often'sucks some of the unsolidied metal from the mold and leaves the slug with a spongy ragged base" or else renders it wholly unsuitable for use. Attempts have been made to increase the casting period, but because of the impossibility of shortening the time for the lookup and distributing operations such attempts have necessarily resulted in prolonging the casting cycle vand thus decreasing the efficiency ofthe machine. These and many other difculties are well known to the art, and it would serve no useful purpose to discuss the matter further.

The primary object of the present invention is to obviate the foregoing and other diiiiculties and,

to this end, the invention provides an improved form of metal pot and metal injecting mechanism, as well as an improved form of automatic safety means to prevent casting in the event that the machine fails to function properly during the casting cycle of operation, and also an improved form of metal pot mouthpiece Wiper. The invention, while adapted for use with any of the present day commercial "machines, :has lbeen developed particularly as part of a complete .machine which is substantially new in its entirety. Otherl phases of the new machine are dealt with in the Plastaras copending applications Serial Nos. 311,091, 355,434, 377,364, 383,133 and 390,558 flled respectively on December 27, 11939, September 5, 1940, February 4, 1941, lvl-'arch 13, 1941, and April 26, 1941.

One of the principal features of the invention is the rapid introduction of metal into the mold under uniform high pressure and with a minimum volume Vof air to be exhausted from the mold. Generally speaking, the metal pot ,is formed so that the contained molten metal may be maintained at an unusually high level, and the metal injeotingmechanism isadapted to-be operated in stages, with `a pause between stages, for the introduction of the metal into the mold in such manner that only the volume of air occupying the mold cavity needs Y,to .be displaced by the incoming metal. .More speccaily, the metal potvcrucible is .formed .with `two compartments, one a `main compartment corresponding except for size to thecruoible'of the present commercial machine, and .the otheran Aauxiliary compartment or a reservoir `from which molten metal is dipped and fed to the maincompartment to maintain a constant high level of metal therein. The metal pot is `mounted-to move horizontally into and out of casting relation tothe mold, and the different stages of loperation of the pump plunger take place in timedrelation to the movements of the metal pot.

`The active-strokeof the pump plunger is carried out in threestages: In the first stage, it is moved .downwardly to a predetermined advance position to shut off communication between the main .compartment ,and the pump well prior to the forward movementof the pot into casting re- `lation .to the mold. The plunger remains in such advance position while the metal pot is moved to its casting position. After such movement of the metal pot, the plunger is moved to a second ad- Vance position'to raise the metal in the throat passage above the level of the metal in the main compartment so as thereby to exhaust the air from said passage. Thereafter, and in the third and .final stage of its `active stroke, the Aplunger is ,movedall the way down to complete its stroke and inject the .molten metal into the mold under uni- .form pressure and at a high velocity, forming a dense slug body having a casting face of solid sharply denedcharacters by llingthe mold and the intagliooharacters inthe matrices completely before the metal has an opportunity to chill and solidify. The return stroke of the plunger -is ef- `.active `stroke exhausts the air from the throat passage, the maintenance of the plunger in its first advance position during both the forward and return movements of the metal pot before and after casting causes the plunger to perform a further function. By shutting oif communication between the main compartment and the pump well, without raising the level of the metal in the throat passage, the plunger removes the small quantity of metal in the well and 4throat passage from the influence of the larger body of metal in the main compartment, and leaves it subject to atmospheric pressure at the discharge end of the Athroat passage only; hence, regardless of the amount of displacement of the metal in the main compartment due tothe sudden stopping of the r-metal pot inweither of its extreme positions, the

metal in the well willnot be affected thereby and the possibility of metal spilling from the upper point, all as will be explained more fully hereinafter. Y

The operation of the `pump plunger in stages is effectedby two separatemeans operating successively and individually. Thus, the rst two stages of the active stroke of the plunger and the nal stage of its return stroke, or in other Words the movements of the plunger to and from its advance positions, are effected by a cam on the main cam shaft of the machine; whereas the plunger movements for the third stage of its active stro-ke and the first stage of itsreturn stroke are effected by an individual powerunit in the form of apneumatically operatedl double-acting piston controlled byan automatically operated valve. Normally, the plunger actuating piston is held against movement byV a tripdog, Yand the plunger has a yielding connection with the piston `to provide for relative movement whereby the plunger can be moved independently to andfro-m its advance position. When the dog is tripped and releases the piston, which previously has been placed under a full headl of pressure, the latter picks up the plunger at its second Vaolvance'position and effects the third Vstage of the active stroke thereof for the injection'of the metal into the mold. At the same time, a clipper operated by the plunger actuating piston is immersed in the molten metal in the reservoir. When the metal in the mold has had an opportunity to solidify, and while the metal pot is still in casting position, the control valve is automatically reversed to effect the movement of the piston in the opposite direction and raise the plunger until it is arrested in its irst advance position, the yielding connection permitting the piston to complete its return movement. The dipper, too, is raised at this time and feeds enough metal into the main compartment to restore the level of metal therein to normal. After the metal pot has been returned to its original or inactive rearward position, the plunger advancing means operates to permit the further raising of the plunger to its uppermost position of rest under the influence of the yielding connection.

The automatic safety means to prevent casting when the machine fails to function properlyis in the form of a pneumatically operated stop device controlled by a system of valves and normally operative to prevent the operation of the pump plunger. Each of said valves is operated by a movable part of the machine during the casting cycle thereof, and all of the valves must be operated in order to render the stop device inoperative so that casting can take place. According to a preferred embodiment thereof, .the stop device comprises a pair of pivoted arms or stops held by a spring so that one of the stops is located to prevent the movement of the pump plunger to its advance position and the other is in position to prevent the tripping of the dog which holds the plunger actuating piston against operation. A small pneumatically operated piston is arranged to overcome the action of the spring and rock the stops in unison to their inactive positions. However, a full head of pressure sumcient to overcome the action of the spring will not be admitted into the cylinder in which the piston works unless all of the valves previously referred to are operated, as just stated; and each of the valvesV will be operated only when the machine element which controlsY it is in its proper position.

The flow of compressed air for releasing the pump stops is controlled by a valve operated by the clamping of the composed line of matrices and expansible spacebands between the vise jaws through a yielding slide rod arranged in the left-hand jaw with one end projecting beyond the line contacting face thereof. When the composed line completely lls the space between the vise jaws, whether by its expansion under the influence of the spacebands during justification, or by the inward movement of one or both of the jaws in quadding or centering the line, the slide rod will be moved relatively to the jaw and by such movement cause the valve to be opened to supply the compressed air for effecting the release of the pump stops. However, since there are other conditions which must be fulfilled before the machine is properly conditioned for casting, another of said valves is operated by the movement of the metal pot into its casting position or into contact with the rear face or the mold, but if for any reason the metal pot fails to lock up tightly against the mold, thevalve will not be operated and the pump stops will not be released. Likewise, the mold is moved forward to lock up against the composed line of matrices, and in so doing it operates another of the valves controlling the release of the pump stops, but if for any reason the mold fails to partake of its full forward movement, even though the metal pot subsequently moves into contact with thev mold and operates the valve with which it is associated, nevertheless the valve controlled by the movement of the mold will not be operated and the pump stops will not be released.

The improved pot mouthpiece wiper is adapted to clean the mold engaging surfaces of the mouthpiece, just before the latter engages the mold for the casting operation, and comprises a wiping element which is mounted to yield relatively to its support to avoid interference with the mold carrier when in casting position.

In the accompanying drawings, the invention has been shown merely by way of example and` in preferred form and obviously many variations and modications may be made therein which will still be comprised within its spirit. It is to be understood, therefore, that the invention is not limited to any specific form or embodiment except insofar as such limitations are specified in the appended claims.

Referring to the drawings:

Fig. 1 is a side elevation, as viewed from a position at one side of the machine, of a portion of the machine including the metal pot, some of the parts being broken away;

Fig. 2 is a side elevation similar to Fig. 1, but as viewed from a point nearer to the metal pot, some of the parts being broken away and some of them being in section to show the interior construction;

Fig. 3 is a front elevation of the metalpot and associated parts, some of the parts being broken `away and others being in section to show the interior construction;

Fig. 4 is a vertical section, taken on the line 4--4 of Fig. 3 looking in the direction of the arrows;

Fig. 5 is a side elevation, partly broken away, of the connection between the pump plunger and its operating piston;

Fig. 6 is a front elevation, partly in section and partly broken away, of the pump plunger and mechanism for controlling its operation;

Fig. 7 is a top plan View, taken on the line 1-1 of Fig. 3;

Fig. 8 is a front elevation, partly in section, of the cam mechanism for controlling the operation of the pump plunger;

Fig. 9 is a perspective view of the cross-head connected to the lower end of the plunger operating piston;

Fig. 10 is a front elevation of a portion of the vise and casting mechanisms, partly broken away and partly in section, showing the relation of the pump stop mechanism thereto;

Fig, 1l is avertical section, taken o-n the line II-II of Fig. l() looking in the direction of the arrows;

Fig. 12 is a vertical section, taken on the line I2-l2 of Fig. 10'looking in the direction of the arrows;

Fig. 13 is a vertical section, taken on the line l3-l3 of Fig. 10 looking in the direction of the arrows;

Fig. 14 is a vertical section, taken on the line lll-I4 of Fig. 10 looking in the direction of the arrows;

Fig. 15 is a horizontal section, taken on the line |5|5 of Fig. 14 looking in the direction of the arrows;

Fig. 16 is a horizontal section, taken on the line I6I6 of Fig. l0 looking in the direction of the arrows;

Fig. 17 is an end elevation of the left hand vise jaw and pump stop control mechanism associated therewith;

Fig. 18 is a perspective view of the structure shown in Fig. 17; and

Fig. 19 is a top plan View of the pump stop and its actuating plunger.

General description Referring particularly to Figs. 2 and 4, a line of matrices M is presented to the face of a slotted mold A by a vertically movable transporter or first elevator T. The transporter T is adapted to carry the line from a lower line receiving position to an upper line transfer position, being arrested at an intermediate casting level by the engagement of a lug t on the front face of the transporter slide T1 with a retractible paw] V1 pivotally mounted on the top of the vise frame V.

The mold A is supported in a holder A1 and, as usual, comprises a lower body portion a, an up er cap portion al, and intermediate liners a2 (Fig. 16), forming a mold cavity a3. In the new machine, and as set forth in the aforementioned Flastaras application Serial No. 355,434 the mold holder A1 accommodates but a single mold and is adapted to swing upwardly from its normal vertical or slug ejecting position into a horizontal or casting position, and return, during each casting cycle of the machine. While in its horizontal swinging movement is effected.) Vmechanism includes a rocker arm B1, fulcrumed position, the mold holder A1 is moved forwardly and rearwardly into and out of contact with the `composed iine before and after casting, the vari- Vous movements of mold holder being brought about by corresponding movements of a hollow rock shaft B (see Figs. 1, 10 and 16) on which it ismou'nted. Thus, the rock shaft B is rotatably mounted in a -pair of fixed bearings C and C1, the former locatedrnear the front of the rock lshaft and the latter just rearwardly of its center.

once during each casting cycle by a worm gear D10. (The power for rotating the rock shaft in `'the reverse direction, i. e., to swing the mold holder from casting to ejecting position is pneumatic, although the operation is under the control of the same cam through which the initial IThe operating near its center on a pin e supported in bosses el on'themachine frame E, and formed at its upper end with a gear sector bmeshing with gear teeth b1 formed around a portion of the periphery of the 'rock shaft B at the rear end thereof. At its lower end, the rockerarm B1 is equipped with an anti-friction roller (not shown) arranged to track along an edge cam D1 keyed to the earn shaft D. Upon the inauguration of the casting cycle, as the cam shaft D rotates, the cam follower rides onto a highportion thereof and causes theroclrer arm B1 to swing in a clockwise direction (looking from the front of the machine in l) to rotate the rock shaft B through an angle of 90 to bring the'mold holder A1 to its horizontal or casting position (Figs. 10 and 16). During the engagement of the cam follower with the high portion of the cam D1, those movements incidental to the actual casting of the slug take place, i. e., the mold holder A1 is moved forwardly to force the mold A into contact with the composed line of matrices M, as in Figs. 4 and 16, the slug cast, and the mold holder then moved rearwardly to carry the mold out of contact with the composed line. Thereafter, the mold holder A1 is swung downwardly to its normal vertical or ejecting position.

The forward and rearward movements ofthe mold holder A1 are eifected through corresponding movements of the rock shaft B on which it is mounted, the mechanism employed (Fig. 1) being actuated from the cam shaft D and including a rocker arm F fulorumed near its center for rocking movement in a fore-and-aft vertical plane. At its lower end, the rocker arm F is provided with an anti-friction roller f constrained to follow a cam track d presented between two cam elements D2 and D3 on the cam shaft D. The rocker arm F is bifurcated at its upper end to straddle a fore-and-aft rod F1 located immedicately below the rock shaft B. The bifurcated portion of the rocker arm F engages between a forward enlarged portion f1 of the red F1 and a collar f2 xed to the rod at the rear of the arm F, the forward enlarged portion f1 being guided for fore-and-aft sliding movement in a xed portion of the machine, and the collar f2 banking against the front end of a housing F2 through which the rod F1 extends and which is guided for fore-and-aft movement in an extension of the xed bearing support C1 for the rock shaft B. At its rear end, the housing F2 is formed with a flange f3 which engages in an annular groove b2 formed in the outer peripheral surface of the rock shaft B and forms the connection between the rod F1 and the rock shaft B to effect the movements of the latter in response to corresponding movements of the rod. It is pointed out that the interposition of the rod F1 and associated parts between the rocker arm F and the rock shaft B is to afford a yielding connection (enciosed within the housing F2 and not shown) to allow the rocker arm F to partake of its full stroke during the casting cycle and prevent damage to the parts in the event that for some reason or other the full movement of the rock shaft B is prevented. 1t might also be stated that the teeth b1 at the rear end of the rock shaft B, which are engaged by the gear sector b, are vof sufficient length to allow for the fore-and-aft movements of the rock shaft.

For 'further details of the structure and operation of the mold holder A1 and its operating mechanism, reference may be had to the Plastaras application Serial No. 355,434, the foregoing description being deemed suiflcient for a clear understanding of the present invention.

In the casting position, the line of matrices M confined between a pair of vise jaws G and G1 (Fig. l5) movably mounted in the vise frame V, he line being justified or expanded endwlse by spacebands I-I to ll completely the space between the jaws (compare Figs. and 16) or else one or both of the jaws G and Gl being moved in wardly from full Vline position to contact and exert a clamping pressure on the line.

The vise jaw and justifying mechanisms, which form a part of the new machine in which the present invention is embodied, are fully shown and described in the aforementioned Plastaras application Serial No. 383,133, to which reference may be had for more detailed information. As therein stated, perhaps the best way to understand the improved vise jaw mechanism is to con- Sider it'as a line quadding and centering attachment. Actually, when the machine is at rest, both jaws are urged outwardly by power devices individual to the respective jaws. However, after the line has been positioned between the jaws and the machine cycle inaugurated, the power devices reverse the forces acting upon the jaws, urging them inwardly to their casting positions. After casting, the forces acting upon the jaws are again reversed, to reestablish the original conditions, so Ythat the composed line may be withdrawn from between the jaws for distribution.

The various conditions of vise jaw operation are determined by permitting free movement of the jaws by the forces which act upon them or by limiting their inward movement through the medium of adjustable stops which may be selectively interposed in the paths of the jaws. Thus, when it is desired to cast a line of full length (regardless of its actual length), a stop adjusted to full line position is interposed in the path of each jaw to prevent its movement inwardly beyond the adjacent end of the mold slot. Different settings of the stops will produce lines of correspondingly different measures. Moreover, by setting the stops inwardly from their full line positions, the inv/ard qua-sliding movement ol the jaws will be arrested to give a fixed indention at either or at both ends 0f Vthe line, as may be desired.

For free or random quadding with either jaw,

Y the casting position of that jaw is determined by dlrect contact with the line when backed up by the other'fixed jaw, Whose casting position is determined by its respective stop. For a centering operation, the stops of both jaws are disabled,

and the jaws coupled together for equi-distant movement so that their casting positions will be determined by direct contact with the line when it has assumed its centered position.

The jaws are pneumatically operated .by separate and distinct air cylinder and piston devices controlled by automatically operated valves which alternately `charge and vent the cylinders to urge the jaws inwardly and outwardly at the proper stages in the machine cycle. Hydraulic mechanisms, one for each jaw, exert clamping pressure to hold the jaws in their casting positions..

When both jaw stops are active, as will be the case when a line of full measure is cast, or when the stops are set for fixed indention at either or at both ends of the line, the hydraulic mechanisms will hold the jaws lmly against their stops as the spacebands are driven up to justify the line as well as during the slug casting operation. When both stops are inactive, as in centering, the hydraulic mechanisms will act to produce a line squeeze, since, under those conditions, the line `itself is all that determines the casting positions` of the jaws. During random quadding with either jaw, the hydraulic mechanism associated with the fixed jaw will hold it firmly against its stop, whereas that associated with the quadding jaw, whose 3 stop is ,.inactive, will exert a squeezing pressure upon the line, since under this condition, too, the line itself determines the casting position of the M etal pot and pump plunger `Coming now to the present invention, the metal pot O (see particularly Figs. 4 and '7) comprises a crucible O1 which is divided by a transverse partition O2 intoV a front main compartment O3` and a rear auxiliary compartment or reservoir O4 from which molten metal O5"v is supplied to the main compartment. The upper edge of the partition O2 is cut away, as at o1 (Fig. 4), to a depth corresponding to the level at which the metal is to be maintained in the compartment O3, e.,`

the cut away o1 provides for an overflow` of metal from the compartment O3 back into the reservoir O4. Associated with the compartment O3 are the well O6 located at the bottom thereof, the cylinder O'I in which the pump plunger P works, and the throat passage O8 leading from the well to a point above the level of the body of metal in the compartment, the upper end of the passage being provided with a perforated mouthpiece O9. As usual, the wall oi the cylinder O" is, formed with a porto for the admission of metal from the compartment O3 into the well O6 when the plunger P is in its uppermost position, the port `being adapted to be closed by the'plunger during the metal injecting operation. Electrical heating elements I are arranged-interiorly of the crucible O1 around the side and bottom walls of bothlthe compartment O3 and reservoir O4 in direct contact with the metal O5 therein; and similar heating elements I1 for the well O6 and throat passage O8 are arraIl-ied` in an exterior chamber throughout the length of the throat passage. The

Crucible O1 is removably supported in 'a jacket;

O11 which completely surrounds and is insulated from the sides and bottom thereof; and the top of the Crucible Ol is also enclosed by an insulated jacket O12 except for a central opening O13 (Fig. '7) above the compartment `O3 and reservoir O4 which is closed by a removable cover plate (not shown).

In the present instance, the metal pot O is' mounted on a carriage K supported in the machine frame E and adapted forhorizontal foreand-aft movement into and out of casting rela,-`

tion to the mold A. At its four corners, the carriage K is equipped with rollers lc which ride on rails formed by channel members e2 of the frame (See Figs. 2 and 3).

The reciprocation of the metal pot is effecte Vby the cam D2 in cooperation with a second cam D4 also lixed to the main cam shaft D, the cams Dz and D11 providing between them a trackway' adapted to receive a roller k1 journalled in the end of a short arm K1 of a bell crank lever KZ pivoted on the machine frame (Figs. 1, 2, 4, '7- and 8). A long arm K3 of the lever is connectedl to a rod K4 pivoted to one arm of a bell crank` lever K5, the other arm of which is connected at one end of a toggle link K6 having its opposite end connected to a lug at the rear `of the metal pot O. The lever K5 is pivotally` connected at the front end of a bolt KI which' extends through an opening in a xed block K11 and is held by a nut threaded on the end of said bolt. Thearm K3 of the bell crank lever K2 is connected to the rod K4 by means of a link K9 having spaced arms which present at their upper ends a collar K10 encircling the rod K1 and acting as an abutment for a relief spring K11 which reacts between the collar and a pair of ,adjust--` ing lock nuts K12 threaded onthe rod at its.' lower end. An adjustable wedge-shaped element:

a position to insure a proper lockup between the.V metal-pot mouthpiece O9 and the rear face of. the mold, on the one hand, and betweenthe.

front face of the mold and the composed line,

on the other hand.` For this purpose, the wedge-4 shaped element K13 is formed with arms k2 which straddle the block'K vertically and carry each an adjusting screw k3 adapted to engage the top and bottom surfaces of the block. When the bolt K'1 is loosened, by turning the screws Yk3 in,` one direction or the other, thewedge-shaped elev ment K13 can be moved up or down, as the case may tbe; and `when the bolt is tightened therel after,l it will occupy a different fore-and-aft; positionand thus relocate the pivot point forthe lever K5.

The pump plunger P is end of a plunger rod P1 by which it is attached to the power means for effecting its reciproca. tion in the cylinder O1. VA plate P2, formed withV an `opening p adapted :to register with an opening p1 in .the head of `the plunger, is arranged inside the plunger for adjustability to effect.

eitherY complete or partial registry of said openings, .as'desired, whereby a metal by-pass of determinable sizeis provided so that the plunger can partake of a full downwardstroke durin each castingoperation.

,. The full-stroke Dperation Vof the O11! vextending from the rear of the well upwardly connected-to the lower,

plunger,l P is desirable for two reasons: First, itkeeps the inner wall of the cylinder O7 free from metal dross and oxide which would otherwise rapidly accumulate Vthereon below the plunger. .'llhus, if it should happen that a series of small slugs were being cast, the plunger would move only a short distance downwardly in the cylinderOl, and below that point the cylinder wall .would become fouled suiciently thereafter to interfere with the movement of the plunger for a longer stroke in casting the larger size slugs. Secondly, the full-stroke operation of the plunger is important in connection vwith the operation of the metal transfer dipper .which is to be described hereinafter.

Pump plunger Operating mechanism The pneumatically operated means for reciprocating the pump plunger P comprises an air cylinder YS supported above the metal pot O on a cross-head K11 (Figs. 1, 2, 3 and 6) connected to the upper ends of posts K16 which rise from opposite sides of the carriage K to which they are rigidly secured. A double acting piston S1 (Fig. 2), arranged within the cylinder S, is adapted to be controlled by a two-way valve S2 (Fig. `8) which admits air into the bottom or top of the cylinder S to move the piston up or down. The opposite ends of the cylinder S are closed by removable caps s which are clamped in place against the ends of the cylinder by bolts s1 extending between the caps s exteriorly of the cylinder. The upper cap s is formed on its inner surface with a recess s2 into which a Asleeve s3 is fitted and which sleeve receives the upper portion of the piston S1. A compression spring s1 is arranged to surround the sleeve Y.s3 and bears against a shoulder 35 formed on the piston'S1, the spring being capable of expanding sufciently to maintain an effective engagement with the shoulder S5, at all times. Below the shoulder .95, the piston S1 is enlarged to provide a'lower portion s@ in sliding engagement with the inner surface of the cylinder wall s1. As best shown in Figs. 2 and 8, an air pipe S3 leads from the valve S2 to the upper cap s, opening into the cylinder S within the sleeve S7 above the upper end of the piston S1; and an air pipe S1 leads from the valve S2 to the cylinder S and communicates with ,the interior thereof :below the lower end of the piston S1.

The'two-way valve S2 (Fig. V8) is one of sev-Y eral Valves comprising a manifold, secured to the frame E at the front of the machine near Vthe base, and comprises a valve ho-using S5 having a body portion S0 and Va cap portion S'7 removably secured thereto. a chamber S11 into which air under pressure is supplied through a duct s0 formed in the body' portion S6 andV which in turn is connected to an airsupply pipe S9. The chamber S0 is connected byducts s0 and S10 in the body portion to `the.

air pipes S2 and S4, respectively, leading` to the cylinder S, and also communicates with an exhaust duct s11 in the body portion. Within the chamber S0, there is arranged a valve slide S10` spring-pressed against the body portion Sand adapted when in its uppermost position, as shown in Fig. 8, to connect the duct S9 with the exhaust duct S11 through a recess S12 formed in the inner faceof the Valve slide forexhausting air from the top Vof the cylinder S. At the .same time,

.communication is established between the ducts s3 and S10 to admit air to the bottom of the cylinder S. On the other hand, when thevvalve The cap portion S7 presents slide lS10 is moved to itslowermost position, theV ducts S10 and S11 are connected throughthe re-V cess s12 to exhaust Vair 'from thebottom fof 7the cylinder S, and air from the .ducts8 lay-passes the Valve slide S10 andk enters the duct s0 fcrcharging the top of the cylinder S.

The valve slide S10 is moved toits .diierent'positions by a rocker arm .S.11.fulcrumed .at its-.center in the body portions6 and connected atiits opposite ends by ball and socket .joints withthe valve slide S10 and with a vertical slide bar S12, respectively. The slide Ybar S12 is mounted `in upper and lower guideways formed inthe valve housing S5 and provided Vat its upperend with an anti-friction roller s12 held Vin engagement with an overlying edge cam S13 by a tension spring S11` connected bya pin s11 to the lower end of the slide bar and pulling upwardly `thereon from an overlying fixed portion of the valve housing. The cam S13 is made fast Yto a :fore-,and-aft shaft S15, journalled in a fixed portion of the machine frame below the main Ycam 4shaft D, by which it is rotated through a train of three gears S16, S1'1and S18 (Fig. 2). The gear S16 is ysecured to the shaft S15, while the gear S17, of vthe vsame diameter, is secured to the main cam .shaft D. The third gear S12, `independently mounted, is an intermediate gear interconnecting the other-two. The movements of the valve slide S10 are controlled by the cam S13 in timed relation to the movements of the metal pot O into and out of casting position. Since` the valve slide S10occupies only upper and loweroperative positions, the cam is formed with concentric high and low portions $15 and S10, respectively, the high portion being operative when the cam-is at rest and during a part of its rotation to maintain the `valve l,slide in its upper position, and Vthe low portion .S16 coming into operation during the rotation of the cam to move the valve slide temporarily to its lower position. Y

At the start of the casting cycle, when the cam shafts D and S15 commence to rotate in the direction indicated by the arrows in Fig. 8, the roller S13 rides :along the high portion .s1-5 of the cam S13 and the parts remain in the positions lshown until just before the metal pot O starts `to move to casting position, at which time the roller S13 rides ontoV the low portion S16 `of the cam and permits the spring S11 to contract and raise the slide bar S12 to move .the valve slide to `its vlower position. In this lower -position of the valve slide S10, as stated, air is exhausted from the bottom of the cylinder S and admitted to the top of the cylinder, placing the piston S1 u-nder a full load of pressure. The low portion S10 of the cam S13 is suiiiciently long to maintain the valve slide S10 in its lowerposition until the metal has been injected into the mold and had `an opportunity to solidify, and then, before the return movement of the'metal pot is effected, the roller S13 rides up on to the high portion S15 of the cam and depresses the slide bar S12 to raise the valve'slide back to its original upper positionY to effect the exhaust of air Vfrom the top of the cylinder S and the admission of air to .thebottom `of the cylinder to raise the piston S1 therein.

The piston S1 is provided withfarrod /s17'ex- Y piston S1. rIhe'hollow block S10 is drilled through from top to bottom to form an enlarged upper cylindrical bore S and a lower cylindrical bore S of smaller diameter, thus forming a shoulder s21 at the bottom of the larger cavity. The `upper bore S19 is adapted to receive the end oiv the piston rod S12, which extends a shortl distance thereinto, and to accommodate the upper end of a rod Z slidably arranged in the lower bore s20 and projecting beyond the lower end of the block. A

the plunger rod P1 thereto by a pin Z3. The upper end of the plunger rod P1 is provided with a block P3 threaded thereon and formed with a neck portion `p2 adapted to t within the bifurcation 23 in the block Z2. The neck portionp2 is formed with an open ended slot p3, adapted to receive the supporting pin Z3, and is maintained in engagement with the pin by a pawl Z4 `pivoted within the bifurcation and pressed against the top edge of the neck portion p2 by a compres- The plunger rod P1 is equipped v( sion spring Z5. with a handle P4 for moving the rod to make and break its connection with the block Z2. Inmaking such connection, it is only necessary to locate the neck portion p2 of the block P3 relatively to the bifurcation z3 and pull on the handle PA1 (Fig.

4), the upper end of the neck portion p2 engaging a cam surface e4 on the pawl Zl1 and forcing the latter upwardly to allow the neck portion p2 to enter the bifurcation until the pin Z3 strikes the end wall of the slot p3, whereupon the spring Z5 forces the pawl to the position shown in Fig. 5 to hold the parts together. The disconnection of the plunger rod P1 from its operating mechanism is effected simply by pushing on the handle P1 to forcethe pawl Z1 upwardly and disengage.

the pin Z3 and slot p3.

In the assembly of the parts, the plunger P must be accurately located as to height within the cylinder Or1 in order to uncover the port o"v when in its uppermost position and to 4cover the port when in its advance position, and of course it is preferable that the movement required to locate the plunger in its advance position be as little as possible. Such adjustment of the plunger P is accurately obtained by its threaded attachment to the block P3, which permits the plunger to be rotated independentlyr of the block to raise or lower it for alignment with Ythe top` of the port o while the block P3 remains in posii tion for the entry of the neck portion p2 thereof into the bifurcation z3 and the block Z2.

The mechanism which controls the movement of the pump plunger to and from its advance position comprises a rocker arm J controlled by a cam D0` on the main cam shaft D. The rocker arm J is pivotally mounted on a `pin 74:5 supported in the cross-.head extension ,K11 and passing through a spacer bushing 7' formed integrally withthe rocker arm approximatelymidway of` its length. The inner Vendof the rocker arm J is formed with a nose portion 7'1 adapted to overlie a lug Zrl projecting from the block Z2 to which the plunger rod P1 is connected.

The rocker arm J is operated by the cam D0 through a yoke J1 land a flexible pushrod J2.

extending vertically between the yoke and rocker arm and formed of upper and lower telescoping sections i2. and (i3, respectively. As best shown in Figs.,2, 3 and 8, the yoke J1 is horizontally disposed, being pivotally supported at one end on the smooth shank of a screw E3 threaded into a boss e4 on the frame E and having its opposite or free end connected to the lower section i3 of the push rod J2, which latter is formed with a ball i4 arranged to seat in a socket in the end of the yoke and be held therein by a removable cover plate i5. About midway of its length, the yoke J1 is formed with a depending bifurcated lug :i6 which supports a roller j" adapted to track along the edge of the cam D0. The flexibility of the push rod J2 is in part for the purpose of rendering it capable of yielding in the event of too much resistance being oered by the rocker arm J, whereby the yoke J1 is permitted to rise and fall as the cam D6 rotates even though the rocker arm J is restrained from moving. Thus, the upper end of the lower i sectiony3 of the push rod J2 terminates in an enlarged head portion i3 housed within the tubular upper section 7'2. The lower section :i3 has a 4 sliding fit Within the section i2 and a compression spring J3 is conned between the head portion i3 and a plug i0 threaded into the upper end of the section i2. Like the lower end of the section i3, the end ofthe plug 7'3 extending above the section i2 is formed with a ball :1'10 arranged to seat in a socket in the end of the rocker arm J and be held therein by a removable cover plate ;i11.

Because of its flexibility, the push rod J2 is also able to rock in a fore-and-aft vertical plane by virtue of its ball and socket connection with the rocker arm J and yoke J1. This is necessary to permit the movement of the rocker arm J along with the metal pot.

The piston S1 is held in its upper position, as shown in Fig. 1, by a dog L (Fig. 6) which is supported on a roller L1, pivoted to the cross-head extension K11, and carries a roller Z arranged to engage beneath a hardened plate S20 on the block S10. The opposite end of the dog L is pivoted to one end of a bell-crank lever L2 supported in the cross-head extension K1rl and normally held in the position shown in Fig. 3 by a compression spring L3 arranged between the extension K17 and an upstanding lug l1 on the lever L2. 'Ihe other end of the; lever L2 extends toward the side of the machine in position to be engaged by its actuating means for rocking it against the pressure of the spring L3 to the4 dotted line position shown in Fig. 6 to retract the dog L and move the roller l clear of the plate S20 and permit the operation of the piston S1. The active position of the dog L, that is, the extent to which it projects beneath the plate S20, is determined by an adjusting screw Z2 carried by the lever L2 and abutting against the end of a stop L1`dowelled into the extension K1".

The operation of the dog `L is controlled by a cam D7 (Figs. l, 2 and S) fixed on the main cam shaft D and operating through a yoke L5 rock-Y ably mounted at one end on the screw E3 in side byside relation to the yoke J1 and being equipped with a roller Z3 adapted to track on the edge of the cam D7. The free end of the yoke L5 is connectedto the dog actuating lever L2 by a flexible push rod L0 which is identical with the push rod J2.

As, will be observed in Fig. 8, the cam DG has concentric high, low `and intermediate portions d3, d3 and d2, respectively. The cam D'I'has con- `centric high and low portionsd@` and d5, respectively. The partsare .shownin theirvnormalipo sitions of rest with the roller 7'? in Contact withk the low portion d3 of the lcam D6 andthe rollerv Z3 in` contact with thelow portionvd5v of the cam D7'. sition shown in Fig. 3 and the pump plunger P is in its uppermostposition with the blocksZZ andthe push rodJ2 to rotate the rocker arm J clockwise (Fig. 3). The movement `of the rocker arm J moves the pump plunger P downwardly to its` advanoegposition against the action of thecompression springV Zlso as 'toclose the port-o` and keep it closedA during the castingoperation; compare Figs. 3 and 6. Subsequently, after 'the metal pot has been moved to casting position; the

roller i7 rides momentarily up onto the high portion d8 of the cam D6 to rock the arm J further inthe `saine direction and move the plunger P downwardly to a secondadvance position. This raises the vmetal `in the throat passage O8 upto the mouthpiece O9 andcompletely exhausts the air from the passage. Vllhilev the roller il remains on the highV portion d of the cam D6, the roller Z3 rides up onto the high portiond1 of the cam Dlt-o lift the yoke L and, through the push'rod L6, retract the dog L to permit the descentgo'f the pump plungervforthe injection of metal into the mold. The roller j" then rides down from the high portion d1 to the intermediate portion d2; andthe roller Z3 -remain-son the high portion d4* of the cam D7 until after the piston S1 '-in the cylinder S'returns to its uppermost position'in effecting the return stroke of the pump lplunger P, whereupon it rides down onto theA low portion d5 to allow the yoke L5 to drop as the-dog Visre'- turned to its active position by the compression` spring L3. It is notl until after thisy that the roller. 7'7 ridesnfrom theintermediate portion d2 down onto the low portion dvof the cam D6 to n allow the yoke d1 to-drop andi-permit the compression spring Z1 to expand and, through the slide rod Z, raise the pump plunger Pto itsuppermost position. Thus, the multi-stage operation of theV pump plunger, in both its active and return strokes, iseffected.

Dipper A vertically reciprocable'dipper N, operated conjointly-with the pump plunger P, is arranged to feed a quantity of the molten metal O5 Vfrom the reservoir O1 into the compartment O3 after carried by an arm `N2 rabbeted in the side face of the block S16 and fastened thereto. Thearm N2 extends Yrearwardly beyond thevertical plane of the crucible partition02, and at its free end itis formed with a bifurcated boss N3 to receive e Yupper end bearing againsta sleeve NG press-tted into the boss N3 and held therein against relative downward movement by a nut-NI threaded on the upper end ofthe rodand Vcontactingjthe Theupper end ofthe top surface ,of the boss.

rod N1 nts slidingly'within the sleeve VVN6 and isk At this time, the vrocker arm 'J is inthe poopening n thereinwill be iiush with the top edgel of the cutaway portion o1 ofthe partition O2.

With this arrangement, when the piston S1 moves downwardly to eiect the activestroke of the pumppl-unger-R lthe `clipper N, because ofthe sliding connection of the rod N1, with the arm N2, willbe free' to iio'at'on the surface of the mol'- ten metal O5 in the reservoir 'Oi and later be slowly immersed in the molten metal by the eX- pansion of the springV N4. When the piston S1 is subsequently moved upwardly on its return stroke, the dipper N will alsorrise (to the position shown in Fig. 4) and feed a charge of molten metal through the opening ninto the compartmentO3. The size of the dipper N is such that it will contain a volume'of metal slightly greater than that displaced from the compartment O3 in casting the largest size slug for which the machine is adapted, so asto maintain a constant high levelof .metalin the compartment O3 under all conditions. When small size slugs are cast, the excess metal fed to theicompartrnent O3 will merely overflow the cutaway portion o1 of the partition O2 and run back into the reservoir O4.

The yielding connection between vthe dipper rod N1 andthe supporting armk N2 is to prevent the splashing of the metal in the reservoir when the'jdipper N is immersed therein in its downward movement. Thus,.when the bottom `of the dipper` N strikes the body of Vmetal O5, the resistance offered by the metal will cause the spring YNi to 'yield as the supporting arm N1 continues itsirapidand uniform downward movement alongwith theblock S16, the spring N1 expanding thereafter, when the arm N2 has come to rest, to cause the part-s "to resume their vnormal positions with the: lowermost fastening nutV N8V in Contact withY the upper end of the sleeve N6. Because the upump `plunger P partakes Vof a full `stroke each time'itis operated, the dipper N is free to partake of fa full stroke each time it isimmersed and its Icomplete immersion isy thusassured. The upward movement of the dipperi N, ofcourse, is effected through the rigid connection afforded by the engagement of" the nut N8' and sleeve N6 as the arm-N2 is Yraised along with the block S16 during the return of the vpiston S1 to its upper position-in theoylinder-S.

yInits normal -oriuppermostposition the dipper Y N extends above thelevelof'the body of molten each casting operation. Thus, the dipper N is l metal@5 in the reservoir 1O1with its metal holdingchamber N9completely exposed to the at'- mosphere, vanclits proximity to the surface-of the metal O5 lvariesaccording to the changing level of the metal a's ythe latter is drawn'oi'and replenished-from time to time. If the dipper `N were tov have yno contact with the metalIO?5 at such time,

the metal .might solidify and accumulate on the clipper so rapidly that.V the dipper would ll enough `toreduce ,its :capacity below the minimum requirement-s Vand the opening 7L would becomef In order to.

clogged in .a relatively shorti time. avoid this; a .skirt portion N10 is .provided by extendingthe :four sides of the dipper downwardly a suiiicient distance to insure atleast partial immersion'inthe molten metal Yat the lowest contemplated'levelthereof. 'The heat escapes most rapidly through the rod N1, and forthis reason cross `ribs N12/are arranged to extend downwardlyY from the bottom of 'the dipper inthe plane ofthe rod vlili-gndip in'the metal. Thusffheat from the bodyA of'meta'l'05 is conducted` to tliedipper by the skirt` N1o and ribs N12 to prevent the solidication of metal therein before it has an opportunity to drain therefrom, the lm of metal which clings to the walls of the dipper solidifying only to the iiaking point and returning readily to a molten state the next time the dipper is immersed. At the four corners of the dipper N, the downwardly extending skirt N10 is apertured as at N11 to prevent the formation of an insulating pocket of air below the under surface of the dipper bottom.

Pot mouthpiece wiper The improved mouthpiece wiping mechanism (Figs. 2, 3, 4, and 7) comprises a wiping element Q mounted at the forward ends of a pair of arms Q1 and Q2 arranged on opposite sides of the metal pot O and pivoted at their rear ends in forwardly extending arms Q1 and q2 of a bracket Q3 arranged at the rear of the metal pot. Near its rear end, the arm Q2 is formed with a depending lug Q3 provided with a laterally extending pin Q4 to which one end of a tension spring Q'1 is fastened, the opposite end of the spring being secured to a pin Q5 projecting from the bracket Q3. The spring Q1 is adapted to rock the arms Q1 and Q2 to the dotted line position shown in Fig. 2 to carry the wiping element Q downwardly across the face of the mouthpiece O. The action of the spring Q4, however, normally is constrained by the engagement of a roller Q6 on the arm Q2 with the horizontal top surface of a head portion Q2 of a vertical slide bar Q5 arranged in a guideway e5 (Fig. 3) formed in an upward extension E1 of the frame.E (see also Fig. 7), being removably held in the rguideway e5 by a cover plate e3. The head Q2 of the slide bar Q5 is long enough to permit the fore-and-aft movement of the wiping mechanism along with the metal pot O and still have the roller Q6 remain in contact with it. The lower end of the slide bar Q5 rests on the top surface of a horizontal arm q2 of a lever Q6 pivoted to the frame E and having a vertical arm Q9 equipped with an anti-friction roller Q1u at its lower end adapted to 4track on the edge of a cam D8 xed to the cam shaft D. The cam D8 is so formed that, at the proper time, the roller Q will ride into a depression d6 therein and the spring Q4 will exercise itself to rock the arms Q1 and Q2 to the dotted line position shown in Fig. 2, forcing the slide bar Q5 downwardly as indicated by the dotted lines in said figure and moving the wiping element Q downwardly across the face of the mouthpiece 02. This action ismomentary and thereafter the roller Q10 rides up out of the depression d6 in the cam D8 and lifts the slide bar Q5 against the tension of the spring Q1 back to its upper full line position, thereby moving the wiping element Q upwardly across the mouthpiece O9 and restoring it to its upper position.

The wiping element Q is resiliently mounted on the arms Q1 and Q2 for the two-fold purpose of providing for a yielding pressure as the wiping element Q moves over the face of the mouthpiece O9 and of enabling the wiping element to be supported rearwardly out of its wiping position when not in use so as to avoid interference of its supporting means with other parts of the machine during the wiping operation, as would be the case if the arms Q1 and Q2 were extended farther toward the front of the machine. The arms Q1 and Q2 are rigidly spaced apart by the tubular bar Qr1 set back a short distance from the forward ends of the arms. In advance of the bar Q", a plate Q2, to which the wiping element Q is attached by screws Q11, is pivotally mounted by means of pin Q12 projecting from opposite ends thereof and extending through apertures in a pair of side plates Q13 secured one to the end of each of the arms Q1 and Q2. The side plates Q13 are pivoted at the outer side edges of the arms Q1 and Q2 on screws Q14 and held against stops Q15 by tension springs Q16, being free to rock clockwise (Fig. 4) whenever the action of the springs Q16 is overcome. This isa safety feature to prevent damage to the parts in casev some obstruction should be accidentally placed in the path of movement of the wiping element Q in its downward movement which would tend to force the wiping element rearwardly. The yielding wiping pressure is alforded by a pair of tension springs Q1'l each secured at one end to the rear face of the plate Q8 and at its opposite end to an ear Q18 at the rear edge of the respective side plate Q13. The springs Q1'1 hold the plate Q2 rearwardly against the front edges of the side plates Q13 but allow it to swing forward as the wiping element Q moves over the face of the mouthpiece O1 during its ywiping movement. Timing of operation.

. It may be well at this time to review the operation of the parts thus far described. At the. time the line of matrices M is located in casting position, the parts occupy the positions shown in Fig. 2, with the line of matrices M, the mold A and the pot mouthpiece O2 in horizontal foreand-aft spaced apart relation. With these parts in such position at the start of the casting cycle., as the main cam shaft D commences its rotation (in the direction of the arrow in Fig. 8), the mouthpiece wiping operation is effected by the` roller Q10 riding into and out of the depression d6 in the cam D8 to cause` the wiping element Q to` be moved quickly down overthe mold engaging face of the mouthpieceO2 and back again to its original position. About the time that the wiping operation is completed, the roller i2 rides up onto the intermediate portion d2 of the c am D6 and rocks the yoke J1 upwardly, this movement of the yoke J1 being transmitted by the flexible rod J2 to the rocker arm J which in turn presses down on the lug Z2 and moves the pump plunger P to its first advance position ,as shown in Fig. 6 (and by the broken `lines in Fig. 4) against the action of the spring Z1. As will be seen in Figs. 4 and 6, in its advance position the pump plunger P covers the port o in the wall of the cylinder O2 and shuts olf communication between the compartment O3 and the well O6. Continued rotation of the cam shaft D now causes the roller k1' (Fig. 2) to ride along its trackway and be shifted from the position atthe' left to that at the right indicated byV the dotted circle to which the reference character`k1` has also been applied.` As a result, the lever K2 isv rocked counterclockwise (still referring to Fig. v2) and, through the linkK9, rocks the lever K5 clockwise to straightenout thetog.

gle link K6 and move the carriage K forward, thejV metal pot O and the 'mechanisms supportedl thereon moving as a unit with the carriage until; the mouthpiece O9 is forced against the rear face of the mold A under a heavy lookup pressure determined by the strength of the spring K11.V In the meantime, the mold holder A1 has been `moved forward by the arm F (Fig. 1) to bring the ffront face of the mold A into engagement A with the line of matrices M (see Fig. 3), the

lockuplpreparatory to the injection of ymetal into the mold cavity a3 from the metal pot is thus completed.

All thiswhile, therotation of the :cam shaft VD has effected a' rotation of the cam shaft S15 through `the gears S16, S17 and S18, and at Vabout this. time the cam S13 (Fig. 8) has been rotated sufliciently so that theroller S13 rides down onto the 10W `portion S15 of the cam `and permits the springs14 to lower the valve slide S1o to establish communication rbetweenf'the ducts s1 and S11, on

the one hand, and the ducts S5 and S9, on theV other. Such operation of the valve slide S10 exhausts the air from the` bottom of the cylinder S and admits a full head of pressure to the top of the cylinder.

NoW as the cam shaft D continues to rotate, the roller 9"' rides Vup onto the high porti-on d8 of the cam D6 and e-ects'the further downward movement of the plunger P to its-second advance position for raising the metal in the throat passage O8 up to the mouthpiece O9. Thereafter, the roller Z3 rides onto the high portion d1 of the cam D1v and lifts Vthe yoke L5 and iexible rod L6 to rock the lever L2 clockwise (Fig. 6) and retract the dog 1L to the broken line position (same iigure). This releasesv the piston S1 in the cylinder S for downward movement Aboth by the. head lof air pressure already established in the top of the cylinder and by the spring s4, which latter is intended primarily to overcome the inertia of the piston. Because the pump plunger P is `at this time in its second advance air pressure Aacting onv the piston S1 is great enough to effect the desired quick and forceful active stroke of the `pump plunger P and bring about a rapid injection of metal into the mold cavity; As previously pointed out, the movementof the'V pump plunger P to its second advance position raised the metal in the throat passage O8 and, in so doing, displaced the air contained in the throat passage and exhausted it through the mouthpiece O9 into the atmosphere, with the result that at the time of the injection of the metal into the mold A substantially the only air to be exhausted from the mold cavity a3 is that contained in the cavity itself.

Reference to Fig, 8 will show that the roller .913 remains von the low portion S of the cam S13 for a period of Vtime (about a '20 rotation of the cam shaft or one-ith of the casting cycle) suflicient to insure the solidication of the metal in the mold cavity a3 before riding onto the high portion s15 of the cam to depress the slide bar S12 and shift the valve slide S10 to its original upper position, for venting-the cylinder S at the top and charging it at-the bottom to raise the piston S1 and effect the return .stroke of the pump plunger P. It is. pointed out that the upward stroke of the piston S1 `is much less abrupt than its downward stroke. In the latter instance, the spring s4 0perates'to overcome the inertia of the piston and assist the compressed air `in forcing the'piston downward, andk is employed to augment the force ofthe compressed air not because of a drop in pressure during the initial downward movement of the piston S1, the space in the cylinder serving tof house. the :spring providing for asubstantial reservoir of air under pressure, but because'the spring constitutes a medium in which may be stored the excess energy available in the compressed air during the return stroke of the plunger P. The utilization of such excess energy, in turn, leads to the desirable result that upon the upward stroke of the piston the compressed air acts alone both-to raise the piston and compress the spring and, initially at least,` i. e., before a full head of air pressure is built up, the Inovement of the plunger is slow enough so that a forced back draft on .the metal in the throat O8 is obviated.

During all this time, however, the rollers i7 and Z3 have remained in engagement with the portions d2 and d4 respectively, cf their respective cams D6 and D1 to hold the rocker arm J in the position to which it was originally moved and to maintain the dog L in its retracted position. Hence, as the pistonS1 rises and effects the return stroke of the pump plunger P, the rocker arm J engages the lug Z'I on the block Z2 andI arrests the pump plunger Vin its rst advance position, the spring Z1 yielding to permit the piston S1 to rise to its uppermost position in the cylinder S. Thereupon, the roller Z3 rides onto the low portion d5 on the cam D7 to allow the yoke L5 to drop and the spring L.3 to expand and return the dog L to its operative position with the roller Z engaged beneath the block S16. At this point in the rotation of the cam shaft D, the roller k1 follows its trackway and returns to the left-hand position shown in Fig. 2, rocking the levers K2 and K5 to the positions shown therein and effecting the rearward return movement of the meta-l pot O. Thereafter, the roller i7 rides down onto the low portion d3 of the cam D6 to `allow the yoke J1 to drop and relieve the pressure on the rocker arm J, whereupon the compression spring Z1 expands to complete the return stroke of the pump plunger P, and the parts then occupy their original positions when the cam shafts D and S15 subsequently come to rest.

By Way of recapitulation, one purpose of eiiectr ing both the active andv return strokes of the pump plunger P in stages is to prevent metal from spilling from the throat passage OB through the mouthpiece O9 during the movements of the metal pot `O into and out of casting position. When the pump plunger? is in its rst advance position, it covers the port o in the wall of the cylinder O7 and shuts oif communication between the large body of metal in the compartment O3 and the relatively small body of metal in the Well O6 and throat passage O8. The metal pot O stops more or less abruptly in its extreme positions, and hence the metal in the compartment O3 has a tendency to slosh about. By shunting off communication between the compartment O3 and well O6, this action of the metal in the compartment O3 during the forward movement of the metal pct O has no effect whatever on the metal in the Well and throat passage. During the return movement or" the metal pot O, the volume of metal in the well O6 and throat O8 has been lessened by the amount of metal injected into the mold, and, moreover, by the returnrof the pump plunger P to its rst advance position 1e reduced volume of lmetal has been sucked back to such a low level in the throat passage that there is no danger of its spilling; whereas, if the pump plunger P had been returned far enough to uncover the port o in the wall of thecylinder O1, metal would flowV from the compartment O3 into the well O6 and raise the level ofthe metal

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