US2298358A - Circuit for molding work pieces - Google Patents

Description

Oct. 13, 1942. w. ERNST y2,298,353

CIRCUIT FQR MOLDING WORKl PIECES v Original Filed July 19, 1938 2 Sheets-Sheet l o e www Oct. 13, 1942. w. ERNST CIRCUIT FOR MOLDING WORK PIECES Original Filed July 19, 1958 2 sheets-sheet 2 .JAA/anim /7 WALTER ERNST;

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Patented Oct. 13, 1942 UNITED STATES PATENT OFPICE 2,298,358 CIRCUIT FOR MOLDING WORK PIECES Walter Ernst, Mount The Hydraulic De Gil Ohio, asslgnor to veloigent Corpn.,

Inc.,

Wilmington, Del., a corporation of Delaware Original application July 19; 1938, Serial No.

220,046, now Patent tell January28, 1941. Divided and this application Augusi; 16, 1938. Serial No. 225,158 I 4Claims.

applying multiple pressures to work pieces and a. method of pressing such work pieces with multiple pressures.

One object of this invention is to provide'a hydraulic circuit including a pressing plunger and means for applying a predetermined pressure initially and a higher pressure subsequently to this pressing plunger.

Another object is to provide a hydraulic press control circuit having a pump and a pressing plunger together with a two-stage pressure control mechanism for applying a moderate pressure for a predetermined timeto the pressing plunger and thereafter to apply a higher pressure thereto.

Another object is to provide a method of molding work pieces consisting in applying a moderate pressure to the material while the material softens and partially conforms to the shape of the mold and thereafter to apply a higher pressure to the material to force the softened l 22 around a ilxed plntle 23.

(ci. ca -sz) F up to the attainment of a new and different pressure level, whereupon it again shifts to its neutral or no delivery" position.

- Referring to the drawings in detail, Figure 1v 5 shows a pump having a casing lu with pads ii having ilat surfaces I 2 Ifor reciprocably supporting the shift ring or dow-'control member i3 of the pump, .bearing plates i4 being inserted therebe-v tween. Rotatable within the shift ring i3 of the l0 pump is a secondary rotor i5, provided with lateral grooves i6 engaged byvrollers il Amounted upon shafts i8, passing through the heads i9 of pistons 2li. The latter are reciprocable in radial bores 2| in a primary rotor or cylinder barrel The latter is provided with cutaway portions 2@ and 25 communicating, respectively, with longitudinal pairs of ports 2e, 2l, through which uid is .conveyed to and from the cylinder bores 22 by means of the ports 2e. The details of construction of the pump mechanism within the shift ring i3 form no part of the present invention, and may consist of one or a variety of forms. A typical form of such a pump is disclosed in the copending apmaterial into the remaining portions oi the mold, 25 plication of Walter Ernst, Ser. No. 37,028, led

this being especially valuable in the case of complicated or intricate shapes of molds.

Another object is to provide a method of mold.

ing Work pieces consisting, as described immedi- -ately above, wherein the initial pressure is applied for a predetermined period of time, at the expiration of which the higher pressure is then applied automatically.

In the drawings:

Figure 1 is a transverse section through a radial pump embodying the adjustable high and low pressure control of this invention; and

Figure 2 is a'diagrammatic View, partly in section, of a hydraulic-press control circuit utilize ing the adjustable high and low pressure conL trolled radial pump of this invention.

Figure 3 is a diagrammatic view showing a modied structure by which the high pressure of the radial pump which passes through the three-way valve is controlled directly by the ram 5 of the hydraulic motor.

In general, the adjustable high and low pressure control for radial pumps of this invention consists of a means for adjustably shifting the pressure control, such as the shift ring of the pump, to a plurality-of different stages so that the pump may deliver pressure fluid up to a certain predetermined pressure and then shift to its neutral or no delivery position, after June 2i, 1936, which application matured into Aunited states Patent No. 3,159,553, dated May 23, 1939. The shift ring i8 is provided with diametrically disposed bosses 39, having threaded sockets 3i for the reception of the shift rods 3.2 and 33.

respectively, passing through bores 3d and 35 in. the pump iu. The bores 3d and 35 are provided with leakage chambers a@ having leakage passageways Sl leading back to the interior limited in its position thereon by the head 52 and the collar 53. Leakage escaping past the piston head 5I drains back into the interior of the casing i0 by way of the passageways 54 and 55 in the shift rod 32, and thence by way of the which time it may again be placed upon delivery longitudinal passageway 56, through the Piston sageways 65 and 66 lead from the ports 62 and 64 to the end ports 68 and 61, respectively. The ports 61 and 68 are threaded so that they may be closed by means of threaded plugs. The provision of the piston areas 58 and 60 enables the exertion of different thrusts against the piston head 5I because of the difference in the areas of these annular piston surfaces.

Secured to the dat surface 4| of the side portion 39, as by the screws 68, is the control casing 1|. The control casing 1| is provided with a slot 1|EL within which a yoke 10 is arranged to slide. The control casing 1I is also provided with a cylindrical bore 12, having therein a sliding sleeve 13 for receiving a coil spring 14. One end of the latter bears against the yoke and the other end against the internal flange 15, having on its opposite side the collar 18 and ball thrust bearing 11 engaged by the hub 18 of a hand wheel 19. The latter is provided with a threaded bore 80 engaging the threaded end 8| of the shift rod 33 and locked in any desired position by the lock-nut 82. A retaining nut 83 is mounted on the extreme end of the threaded end 8|. By rotating the hand wheel 19 the coil spring 14 may be caused to engage the iiange 15 of the sleeve 13 with varying pressure, which is transmitted, through the shift rod 33, to the pump shift ring I3, and opposed by one of the piston areas upon the servomotor piston head 5|.

The control casing 1| is likewise provided with a pair of cylinder bores 84 having communicatpump |06 is provided with end plates |09, to one of which is secured the iluid outlet connection I|0 having a pressure connection and a suction connection II2. A suction pipe |I8 runs downwardly from the suction connection I2, into the interior of a iluid tank |I4. Running from the pressure connection III is a pipe |I5 leading to a four-way valve, generally designated IIB,

from which the lines ||1 and ||8 lead respectively to the ports I|8 and |20 at the opposite ends of the main cylinder |2| oi a hydraulic press, generally designated |22. This press is represented diagrammatically, and contains a piston |23 with a piston rod |24, these being reciprocable within the cylinder bore |25 within the main cylinder |2I. The hydraulic press |22 is provided with a trame |26 connecting the main cylinder |2| with the press bed |21, upon which the workpiece or die is supported. The piston rod |24 is provided with an arm |28, arranged to operate a limit switch, in a manner subsequently to vbe described.

ing ports 85 and 86 at opposite ends thereof. Re-

ciprocable in the cylinder bores 84 are piston heads 81 with piston rods 88 threaded therein, as at 89. The opposite end s of the piston rods 88 are threaded into the sockets 80 of the yoke 10. Surrounding the piston rods 88 are the packings 9|, compressed by the glands 82 for the purpose of preventing leakage. The cylinder bores 84 are closed at their opposite ends by the cylinder heads 83, having apertures 84 through which pass the stop rods 85, the opposite ends of which are threaded as at 88 into the ring 81. The latter is provided with a ridge 98 engaging a corresponding groove 88 in the hub |00 of a hand wheel IOI. The hub |00 is threaded internally, as at |02, and engages the threaded portion |03 upon the outer surface ot,

the control casing 1I. When the heand wheel |0|` is rotated, the stop rods 85 are advanced into or withdrawn from the chambers within the cylinder bores 84, thereby providing adjustable abutments against which the piston heads 81 will come to rest when the pressure fluid is supplied thereto'through the ports 86. Oil seals |04 prevent leakage around the stop rods 85 and are held in position by the retainers |05.

The radial pump and its associated control mechanism shown in Figure 1 may be utilized in` a variety oi. circuits. One such circuit is shown in Figure 2, and consists of the pump, generally designated |05, with its servomotor, generally designated |01, and control device, generally designated |08. The casing l0 oithe 75 The four-way valve I|6 is of a conventional type, and consists of a casing |30 having a bore I3I, within which reciprocate the valve heads |32 and |33 on the valve rod |34. At the end of the latter is a handle |35, shown diagrammatically as a ball, but alternatively consisting of a lever or any other suitable means of shifting the valve rod |84. The casing |30 is provided with a central port |36 for the connection of the pump pressure line H5, and end ports |31 and |38 from which the exhaust line |38 runs to the tank |I4. Also provided are two intermediate ports |40 and I4I, from which the lines ||1 and |I8 lead respectively to the main cylinder ports |I8 and |20, as previously stated. By shifting the'valve rod |34 and its heads |32 and |33,` the iiow from the pump, through the pump pressure line I|5, may be directed either to the upper or lower part of the main cylinder I2|, while the opposite side thereof is connected to the exhaust line |38, in the manner-well known to those skilled in the art. Thus, the shifting of the four-way valve |I6 controls the distribution of pressure iiuid from the pump to the press |22 in order to advance or retract the piston |23 and its piston rod |24. Y

The portion of the hydraulic circuit by which the pump and servomotor control systems are operated includes a three-way valve |42, of a conventional type, and having a valve rod |43, terminating in the armature |44 adapted to be shifted by the energization of the solenoid |45. The latter is connected to an electrical circuit. in a manner subsequently to be described. From the three-way valve |42, the exhaust conduit |45 leads downwardly to the fluid tank II4, whereas the pressure conduit |41 leads to the ports 86 at the righthand ends of the cylinder bores 84 (Figure l), from the opposite ends of which the exhaust line |48 leads downwardly to the fluid tank ||4. The three-way valve |42 is supplied with pressure iluid through the conduit |48 leading to it from the pump pressure fluid line ||5, a branch conduit |50 proceeding to one or both of the ports 62 or 64 in the servomotor casing 44 (Figu're 2).

The servomotor |01 may be caused to become operative and shift the shift ring I3 of the pump |08 to its neutral or no delivery or leakage delivery position at any one of three predetermined pressures for the same setting of the thrust of the coil spring 14 (Figure l) These three dinerent pressures are determined by the sure is desired to shift the area on the servomotor piston head Il, which is subjected to a pressure iluid reaching it from the conduit |50. If both of the annular piston areas 59 and Bl in the chambers il and 63 are subjected to this pressure fluid, then the maximum area ofthe servomotor piston 5I is in use, and a relatively low pressure in the conduit |50 will cause the servomotor piston Il to shift and overcome the thrust of the coil spring Il in or-` der to place the pump shift ring I3 in its neuno delivery tion. If the annular piston area I9 alone is subjected to this pressure iluid, then an intermediate pressure will be required to overcome the thrust of the coil spring 'Il and place the pump in its no delivery position. Ii, however, the smaller annular piston area 6c is alone subjected to this pressure huid, then a relatively high pressure in the conduit lill will be required to overcome the thrust of the the pump shift ring i3 to its neutral or "no delivery position.

llo utilize both piston areas B8 and 80 the ports tl and 88 are unplugged while the port 132 remains plugged, thereby establishing a connection between the chambers 83 and 6| by way ci' the longitudinal bores and 65. .If the larger annular piston area B9 is to be utilized, the conduit 850 is connected to the port 62, and the ports 6l, it and il are plugged. If, however, the smaller piston area i is to be utilized, the ports di, S8 and 62 are plugged, in the manner shown in Figure l.

The electrical circuit for energizing the solenoid it includes the lines and |52, leading to the contactor |58 having normally open switch blades |54 and |55, adapted when closed to connect the lines 85| and |52, respectively, with the power lines IBB and itl. The operating coil |58 of the contactor |53 is connected, hy the lines |56 and |180, tothe timingdevice iti from which the lines |62 and |83 lead, respectively, to the power line i and to the normally open limit switch ltd. The limit switch idd is adapted to be closed by the press arm id when it reaches a predetermined position, thereby connecting the line it, through the limit switch ist, to the line |65 leading to the power line i te. The spring 68 normally opens the limit switch itt when the press arm |28 is retracted.

Operation In the operation of the circuit shown in Figure 2, let it be assumed that a relatively high prespump shift ring it to its neutral position so that the connections of the servomctor itl are as shown in Figure l.. area 8E is therefore utilized for this purpose, and subjected to the pressure iiuid in the conduit |50. The hand `wheel 'i9 is then turned until the coil spring 'i4 is given the desired thrust so that, for example, a pressure of 500 pounds per square inch is required at the annular piston area 5d to compress the coil spring 'M and move the pump shift ring i3 to its neutral or "no delivery position. Let it be assumed that the 4pump |96 is in operation, supplying pressure fluid through the line ||5 and valve i i5 to the space above the press piston head |23. Ihe piston head |23 and its piston rod |24 move downwardly,- closing the press and engaging the workpiece so that pressure is built up to the specied pressure of 500 `pounds per square inch.

When this pressure is reached, the servomotor coil spring 'I4 and shift' or leakage delivery posipiston 5| will move to the right (Figure l), overcoming the thrust of the spring 14 and moving the shift ring i3 of the pump to its neutral or no delivery" position. The pump |06 will therefore temporarily hold the pressure in the pressing cylinder |2| at 500 poundsper square inch. Meanwhile, |28 closed the limit switch I, thereby starting the timing device III After the expiration of the time period for which the timing device is set, the latter closes the circuit, energizing the operating coil |58 of the contactor |53, shifting its switch blades |56 and Il! into a position to energize the solenoid III. The latter then shifts the valve rod I of the three-way valve I 42 so as to admit pressure from the conduit |48 to the conduit |41, and thence into the cylinder bores 8l against the pistons 81.

The pistons I1 then move to the left (Figure 1) carrying with them the yoke 10 and further compressing the coil spring ll. This actionl causes the shift rod 33 to move to the left, under the increased thrust oi the coil spring 14, carrying with it the pump shift ring I3, shift rod 32 and servomotor piston head tl. The pistons 81 come to rest against the ends of the stop rods 85, the positions of which may be adjusted by turningA the hand wheel lill, thereby regulating the additional compression space upon the coil spring 74, and hence, adjusting the high pressure stage of the pump. The pressure of 500 pounds per square inch now standing in the conduit |50 is therefore no longer sumcient to overcome the increased thrust of the coil spring 7G. Accordingly. the pump again delivers pressure iluid to cause the piston |23 and its piston rod |2i to exert an increased pressing edect, until the pressure rises to a suicient amount where it will again act against the annular piston area 60 and again shift the servomotor piston head 5| to the right, overcoming the increased thrust of the coil spring 'M and again moving the pump shift ring I3 to its neutral or "no delivery" position. At this greater pressure, for example 2,500 pounds per square inch, the pump is again shifted to its neutral or no delivery position automatically and without the necessity for attention on the part of the operator.

When the four-way valve IIB is shifted to supply pressure uid to the port |20 and retract the pressing piston |23, the limit switch |56 is opened vand de-energlzes the timing device iti, in turn de-energizing and opening the contactor |53 and consequently de-energizing the solenoid |45. The three-way valve |42, therefore. shifts into a position closing on the conduit |49 from communication with the conduit |41, and connecting the latter to the exhaust conduit M8. The pressure is thus released from the righthand ends of the cylinder bores 8l (Figure l) so that the thrust oi' the coil spring 'I4 moves the yoke li) and piston heads 81 to the right to the positions shown in Figure 1. 'I'he electrical and hydraulic circuits are thus placed in readiness for the resumption of another pressing stroke, and the parts come to rest in the positions shown in Figure 2.

In the circuit shown in Figure 2, the pressure iluld employed in the hydraulic circuit has also at the time the press closed, its arm shifted manually when the operator wishes to apply the additional pressing pressure. Alternatively, the three-way valve |42 may be shifted by some portion of the machine when it reaches a predetermined position, such as directly by the press arm |28. The modiiication in which the valve |42 is shifted directly by the arm |28 of the ram is shown in Figure 3. The elements in this figure which correspond to similar elements in Figure 2 have been given the same reference characters, so that no separate description appears to be necessary. Arrangements in which a valve similar to the valve |42 is shifted by an element connected to the press ram are well known to those skilled in the art and disclosed, for instance, in U. S. Patents 2,166,319 to Pocock and 2,167,941 to Ernst.

The `servomotor arrangement containing a plurality of annular piston areas adapted selectively to be subjected to pressure fluid in the hydraulic Ilcircuit is disclosed and claimed in my copending" application, Serial No. 220,046, filed July 19, 1938, now Patent No. 2,230,054 of which this application is a division. It will be observed, however, that the servomotor would be operative for the present purpose with the employment of a single piston area instead of the more convenient plural piston arrangement shown in Figure 1.

The present invention finds an important application in plastic injection molding machinery and methods. With the use of certain molding materials or compounds, it is found desirable to inject the softened material into the mold and maintain it `under a moderate pressure for a cer-4 tain time, while the material softens and partially conforms to the shape of lthe mold.

After the expiration of this time, it is then foundv useful to apply a much higher pressure to the material to force it into the more intricate corners or cavities of the mold. In the present invention, however, these two pressure stages may be severed and adjusted relatively to each other throughout a wide range of pressures so as to adapt the invention most eiciently to the particular working conditions and materials.

It will be understood that I desire to comprehend within my invention such modifications as come within the scope of the claims.

Having thus fully described my invention, what I claim as new and desire to secure by Letters Patent is:

1. In combination in a hydraulic circuit, a motor, a variable delivery pump with a shiftable flow control element connected to feed said motor, means for operating said pump at low pressure to supply low pressure iiuid to said motor during the initial portion of the Working stroke of said motor, comprising resilient means reacting to move said flow control element to full delivery position, servomotor means responsive to a predetermined pressure in said mot-or during the working stroke thereof for shifting said pump ow control element to its leakage delivery position in opposition to said resilient means, time .delay means, means movable by said motor at a predetermined point in its working strcke for operating said time delayvmeans to cause it to begin its delay period, pilot motor means for increasing the reaction of said resilient means on said flow control element during the same working stroke'of said motor to return said flow control element again to full delivery position, and valve means actuated by said time delay means at the end of its delay period while said flow control element is in leakage delivery position to feed iiuid to said pilot motor means for increasing the thrust of said resilient means to th'ereby shift said pump flow control element to full delivery position, whereby said pump is operated at high pressure to thereby supply high pressure fluid to said motor during the latter operation of the same working stroke of said motor.

2. In combination, in a hydraulic circuit, a motor, a variable delivery pump with a shlftable flow control element connected to feed said motor, means for operating said pump at low pressure' to supply low pressure fluid to said motor during the initial portion of the working stroke of said motor, comprising resilient means reacting to move said ow control element to full delivery position, means responsive to a predetermined pressure in said motor during the working stroke thereof for sluiting said pump flow control element to its leakage delivery position in opposition to said resilient means, time delay means, means movable by said motor at a predetermined point in its working stroke for operating said time delay means to cause it to begin its delay period, and valve means actuated by said time delay means at the end of its delay period for causing said resilient means to react with increased thrust on said flow control element while saidow control element is in leakage delivery position to Athereby shift said pump flow control element to full delivery high pressure position whereby said pump is operated at high pressure during the latter portion of the same working stroke of said motor.

3. In combination, in a hydraulic circuit, a motor, a variable delivery pump with a shiftable now control element connectedto feed said motor, means for operating said pump at low pressure to supply low pressure i'luid to said motor during the initial portion of the working stroke of said motor, comprising resilient means reacting to move said flow control element to full delivery position, means responsive to a predetermined pressure in said motor during the working stroke thereof for shifting said pump ow control element to its leakage delivery position in oppotion to said resilient means, time delay means, means movable by said motor at a predetermined point in its working stroke for operating said time delay means to cause it to begin its delay period, and means including a servomotor actuated by said time delay means at the end of its delay period for causing said resilient means to react with increased thrust on said iiow control element while said flow control element is in leakage delivery position to thereby shift said pump now control element to full delivery high pressure position whereby said pump is operated at high pressure during the latter portion of the same working stroke of said motor.

4. In combination, in a hydraulic circuit, a motor, a variable delivery pump with a shiftable flow control element connected to feed said motor, means for operating said pump at low pressure to supply low pressure fluid to said motor during the initial portion of the working stroke of said motorI comprising resilient means reacting to move said flow control element to full delivery position, means responsive to a predetermined pressure in said motor during the working stroke thereof for shifting said pump flow control element to its leakage delivery position in opposition to said resilient means, time delay means, means movable by said motor at a predetermined element to full. delivery high pressure position whereby said pump is operatedat high pressure during the latter portion of the same working stroke of said motor, said time delay means including electrically operated means for shifting said valve means.

WALTER ERNST.

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