FIELD OF THE INVENTION The present invention relates to an injection mechanism of Cold Chamber High Pressure Die Casting (HPDC) machine. More specifically it relates to an improvement in conventional machine injection mechanism, conducted by replacing its hydraulic intensifier with a link mechanism. The present invention ensures high degree of utilization of hydraulic potential energy produced by the system and more reliable process. This present invention may be adapted for conventional High Pressure Die Casting Machines of the day.

BACKGROUND OF THE INVENTION As known HPDC machine mainly consist of Die closing mechanism, Injection mechanism and Ejector mechanism.

Die closing mechanism (Lock End) has the function of closing die halves together and to form die cavity(s). Usually die casting machine capacity is specified in terms of its locking force. Injection mechanism (Shot End) has the function of filling die cavity 82 with molten light metal like Aluminum alloy and squeezing it further.

Function of Ejector mechanism is to eject out the casted part.

Conventional HPDC machine injection process is operated with potential hydraulic energy discharged from accumulator(s). This energy transmission is through all hydraulic set of mechanisms.

Injection process (shot operation) broadly comprise of three phases.

During first two phases injector velocities are principally monitored as per given manner of shot setting.

As shown in Fig.4, during these phases fluid metal reaches near to the level of almost full filled die cavity 83. During filling phase when premier control is on injector ram velocities, major part of potential energy discharged from accumulator gets converted into kinetic energy and pressure built in injector(shot) cylinder piston side chamber depends on molten metal mass and its fluidity, injector mechanism’s moving parts mass and their friction. During this phase counter force of cavity filling is very less. Accordingly momentum during this phase is low.

This segment 88 covers most part of the actual shot stroke.

At the end of cavity filling when almost no air is left in die cavity, metal flow reached up to narrow gate entry of overflow(s) 83 and metal flow is restricted, then counter force starts increasing rapidly. This counterforce causes pressure building in piston side chamber of shot cylinder.

When predetermined pressure or stroke position is reached hydraulic intensifier 93 is actuated. Once die cavity is almost filled, third phase is applied. This phase is also called as intensification phase or squeezing stroke 89. During this phase injector cylinder intensification pressure and in turn specific casting pressure (metal pressure) is monitored.

During this final filling and intensification phase moving parts velocity, kinetic energy drops rapidly and pressure built is highest i.e. maximum potential energy is possessed by moving parts. The squeezing stroke happens to be up to 1 % of total stroke. For instance, squeezing stroke happens to be less than 10mm for total stroke of 1000mm.

All injection phases are completed in time bound manner. This aspect is one of parameters that influence the casting quality. During this conventional injection mechanism operation high amount of high pressurized hydraulic fluid discharged from accumulator gets depressurized and high amount of potential energy discharged from accumulator is wasted.

Another drawback of conventional injector mechanism is low momentum generated during filling phases. Low momentum is highly sensitive to external process fluctuations including fluid metal flow turbulences happening as per the cavity geometry. This shortcoming of less tolerant process compromises the quality of cast piece.

The activity prior to injection shot is to pour molten metal quantity into the filling chamber (sleeve) 84. Said activity has unavoidable variation in poured metal quantity. Another drawback of conventional injector mechanism is final intensification force applied on molten metal for the length irrespective of variation in metal quantity. It is applied through the length till injector motion stops itself. This increases flashing tendency and many times flash is controlled by reducing shot force or over tightening of die locking or reducing some other input parameters. Flashing and other adapted preventive remedies have negative effect on casting quality.

OBJECT

The aim of this invention is to provide an injector mechanism for pressure die casting systems that overcomes the drawbacks of cited prior art with adherence to the essential requirement that this invention should not require any change in conventional injector control systems used for first two phases (Filling phases), that is except for intensification phase and should have matching injection stroke profile and to finish complete injection stroke in the similar time bound manner.

Within the scope of this aim an object of invention is to provide injection mechanism that ensures higher degree of utilization of hydraulic potential energy produced by the system by cutting down energy wastage.

Another object is to provide injection mechanism constituted to produce higher momentum during injector motion to make the process most tolerant to external fluctuations.

Another object is to provide injector mechanism that is constituted to allow an automatic injection stroke adjustment responding to the variation in metal quantity. Another object is to provide an additional injection stroke control feature that allows die caster to limit the squeezing stroke length. This feature will provide an advantage for the process optimization.

Further object is to provide injection mechanism that allows energy saving. Further object is to provide injection mechanism that allows for considerable overloading of die casting machine.

SUMMARY OF THE INVENTION

Object to provide a solution to overcome the drawbacks of cited prior art, the basic idea of present invention solution is to replace conventional hydraulic intensifier at shot end by a link mechanism for injection shot finishing and squeezing stroke operation^ Intensification Phase ).

The link mechanism is incorporated in injector mechanism in such a way that it does not make any change in the given manner of operation of first two filling phases.

Fig.1 illustrates the schematic diagram of the present invention. In the fig. 1 upper half portion shows finished injection stroke, whereas lower half portion shows home position before shot operation.

The link mechanism 15 is interposed between Shot cylinder piston rod 16 and shot plunger rod 14 with its shot plunger 85 inserted in the sleeve 84. The present invention injector mechanism contains Stroke adjustment mechanism 20.

This link mechanism 15 comprises Link assembly 25, Link assembly locking hydraulic cylinders 18, Slip Stroke hydraulic cylinder 21 and Squeeze Stroke Adjustment mechanism.

In order to employ Link mechanism’s considerable mechanical advantage exclusively for intensification phase stroke and not to have its effect on prior filling phase stroke (first two phases) a sub mechanism is incorporated, which unlocks link mechanism at predetermined position of stroke. After this unlocking only, links are free to move. Thus no change is required in the given control system for first two filling phases.

Basic structure of the mechanism:

As shown in Fig.1 and Fig.2, Shot plunger rod 14 is connected to Slip stroke cylinder piston rod 35, that is Slip stroke cylinder piston rod can move Shot plunger rod and vice versa.

Diameter of Slip Stroke Cylinder will be little more than diameter of conventional shot cylinder. This depends on recommended and safe working pressure of hydraulic fluid and the shot force. Slip stroke cylinder body 38 is fixed on Front plate 31 of link mechanism. Squeezing Stroke Adjustment mechanism interposed between Slip stroke cylinder 21 and Cross head plate 17 which is connected to Shot cylinder piston rod 16.

Stroke adjustment shafts 19 are connected to Intermediate plate 32 and Lock Wedge mechanism fixed 23 on Shot End Platen 29.

The present invention mechanism operation sequence:

After pouring molten metal in sleeve 84 injection shot is initiated.

Shot cylinder stroke starts with Shot cylinder shaft carrying link assembly 25 in locked condition. During this segment of stroke as link mechanism is in the locked condition motion force of shot cylinder piston rod is directly transmitted to shot plunger rod 14.

At the predetermined position 76 link mechanism 15 is unlocked. At this point Intermediate plate 32 is anchored, Collar nuts 24 on rear side of Length adjustment shafts 19 hits on Shot end platen 29 and are locked in the position by hydraulic wedge lock 23. This Intermediate plate 32 anchoring starts link assembly movement. Hereafter motion force transmission from Shot cylinder piston rod 16 to shot plunger rod 14 is started trough link mechanism 15, which is indirect motion transmission.

Link mechanism geometry is designed in such a way so as to have force multiplication factor of one during this switchover and for next some part of the stroke. Stroke length covered having multiplication factor of one is approximately 92% of total stroke length.

At the end of filling phase when counter force increases shot velocity starts retarding with building pressure inside the shot cylinder piston side chamber. On reaching predetermined pressure in the shot cylinder, analog signal of Pressure transducer (not shown in figure) 11 opens solenoid valve 43. This starts draining of Slip Stroke cylinder 21. This is end of filling phase and start of Slip stroke.

During Slip Stroke, motions of Front plate 31 with Slip Stoke cylinder body 38 fixed on it are continued but Shot plunger rod 14 remains stationary. This is situation of stationary piston and moving cylinder body. During Slip Stroke motion transmission between Front plate 31 and Shot plunger rod 14 is disconnected.

When Front plate position is reached to the corresponding position 40 to have preset squeezing stroke length and Shot plunger rod 14 at the position 67 where it was at the start of slip stroke, the piston rod 33 of squeezing stroke setting cylinder 22 has pushed mechanical shut-off valve 46 and have hermetically shut off the drain duct 37 of Slip Stroke Cylinder 21. Slip stroke is terminated. The phenomenon of reducing gap in between Cross head plate 17 and Front Plate 31 is used to mechanically shut-off the drain duct 37 of Slip Stroke Cylinder 21. This Slip Stroke drain shut- off position which controls squeezing stroke length is set, by adjusting the position of piston rod 33 of squeezing stroke length setting hydraulic cylinder 22. During this motion disconnection and reconnection, Slip stroke cylinder is acted like clutch operation in engine power transmission.

The termination of slip stroke restarts indirect motion of Shot plunger rod 14, but this time motion force transmitted is high by virtue of mechanical advantage of link mechanism. This is switchover to intensification Phase (Squeezing Stroke). Link mechanism geometry is designed to have increasing force multiplication during this stroke, at 5+ times and for last nearly 1 mm above 13 times. During this phase motion force is transmitted through link mechanism 15 and Slip Stroke Cylinder 21. During intensification phase final multiplied force is transmitted through Slip Stroke Cylinder with building fluid pressure (compressing) inside chamber 36. This will also act as hydraulic damper. Level of Maximum pressure built inside is controlled by proportional relief valve 41. This pressure is equal to Intensification force divided by surface area of piston of Slip stroke cylinder 21.

When shot cylinder stroke is reached to its end position 59, Front plate at its end position 09, squeezing stroke is finished with preset length.

After solidification (cooling) time finished, during die opening Slip stroke cylinder 21 will be filled to its home position. This activity will push out the biscuit 92 (plunger follow through).

The present invention consisting link mechanism by virtue of its mechanical advantage provides force multiplication of five plus times for a length well sufficient for intensification phase segment (squeezing Stroke). This characteristic allows for the reduction of Shot Cylinder diameter to less than half of the conventional machine and reduction in its swept volume to approximately half of the conventional machine. Accordingly hydraulic potential energy supplying accumulator capacity also is reduced. It is approximately of half capacity with respect to accumulator of conventional machine.

This accumulator capacity reduction ensures higher degree of utilization of hydraulic potential energy created by system, by cutting down energy wastage.

As described in prior art, conventional injector mechanism has low momentum generated during filling phases. There is under utilization of hydraulic potential energy discharged from accumulator.

The present invention consisting link mechanism has added mass. Total mass of moving parts of the present invention is estimated to be four to five times of total moving mass of conventional injector mechanism. Accordingly when link mechanism is incorporated, filling phase momentum is high, but well within accumulator capacity. This high momentum fills the cavity very effectively overcoming cavity filling turbulences caused due to cavity geometry. This high momentum will even enables to cast less fluid alloy. Also cavity filling process is most tolerant to external fluctuations and capable of casting more intricate geometric shapes with betterment of cavity filling characteristics.

The present invention mechanism contains Slip Stroke Cylinder. Primary function of Slip Stroke Cylinder 21 is to disconnect and reconnect the motion force transfer between link mechanism 15 and Shot Plunger rod 14 which injects fluid metal into the die cavity 82.

This motion disconnection stroke happens when a predetermined pressure is reached in shot cylinder, said position depends on the quantity of molten metal. Motion transfer reconnection happens as per the preset squeezing stroke length. That is the length of this disconnected stroke segment i.e. slip stroke gets adjusted according to the variation in quantity of molten metal. After motion transfer reconnection, squeezing stroke happens. This squeezing stroke is consistent despite of the said variation in metal quantity. This novel feature of automatic adjustment of Slip stroke segment length responding to variation of metal quantity provides consistent length squeezing happening thereafter, cuts down flashing tendency. That is the present mechanism provides a consistent volumetric squeezing of casting in formation. This novel feature of varying length Slip stroke of the present invention eliminates the drawback of conventional mechanism which causes intensification force applied on molten metal through the length irrespective of variation in metal quantity.

Further according to the present invention intensification (squeezing) stroke length happens to be as per the corresponding length preset at squeezing stroke adjustment mechanism. This allows die caster to limit the length of squeezing stroke segment (reduction within maximum possible length). This added control feature will enable die caster to use final squeezing stroke of higher force with limited squeezing length than the reduction in shot force. That is the feature allows for the limiting of volumetric squeezing. Said control provides an advantage for casting parts requiring short cavity filling time but less volumetric squeezing and thin wall parts. This is process optimization.

According the present invention when accumulator capacity is reduced with respect to conventional mechanism, also it’s charging time is brought down to half time. Thus machine pump motor on-load time for accumulator charging is reduced to half. This makes considerable saving in machine running energy.

Similarly Shot cylinder rod side chamber volume is reduced. This will make energy saving during returning of Shot Plunger rod. Traditionally for a given cast part, die casting machine selection is done on the basis of Specified locking force of machine, the total projected area of corresponding die cavity and applied specific casting pressure. Intent is total casting force should not exceed die locking force.

According to the present invention when injector process is optimized with controlled consistent length of squeezing stroke, cutting down flashing chances and effective cavity filling achieved by high momentum during cavity filling will allow for considerable overloading of the die casting machine. That is given dies may be shifted from higher specification machine to lower specification machine. Thus all objects of the present invention are attained.

Some important aspects of the present invention:

Damping of higher dynamic power generated through acceleration of heavy mass will happen as follows:

Velocity retardation during cavity filling finishing will be delayed by virtue of increased inertia. This will consume the power. When slip stroke cylinder draining is stopped by shutting off drain valve system motion force will build pressure inside slip stroke cylinder chamber 36 to initiate squeezing stroke.

All shot cylinder motion power is transmitted through working fluid filled slip stroke cylinder 21. Once slip stoke is started thereafter it will provide a cushioning effect.

Durable life of added new parts and assemblies of the present invention: Unlike similar link assembly on lock end side, the Shot end side link mechanism holds some advantages. Shot Injection force has to overcome collinear cavity filling counter force and to force squeezing through collinear sleeve Not subjected to any shock force or imbalanced (off-center) force.

No formation of force couple.

Major L link motion is through 35° only. Therefore the present invention mechanism even though subjected to high accelerations will provide longer durable life than the life of lock end side link assembly (same machine part).

Effect of high speed hitting of Collar nuts 24 on Shot end platen 29:

Stroke adjustment shaft collar nuts will hit shot end platen at relatively high speed. But except intermediate plate anchored at that time, motion of machine’s shot cylinder plunger rod, link mechanism and moving parts ahead of it will be continued hence there will not be any major momentum break. Load on subjected parts will not be higher. (Mass of Intermediate plate, stroke adjustment shafts and Nuts ‘Velocity at that time). Possibility to Increase squeezing stroke length beyond 1% of total stroke:

It is a possible to increase the squeezing stroke beyond 1% of total stroke for a very unlikely situation. Rapidly increasing final squeezing force is applied only at the end of stroke. The present invention link mechanism provides increasing force multiplication factor of 4+ for approximately 1.5% of total shot plunger stroke length. Therefore it can be extended up to 1.5% of total shot plunger stroke length. The present invention has biscuit accommodation capacity of about 10% of total stroke length. This may be extended.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is showing schematic top view of the present invention comprising Link mechanism 15 interposed between Shot cylinder piston rod 16 and Injector plunger rod 14. Upper half portion shows finished injection stroke, and lower half portion shows the home position before shot operation.

FIG. 2 is showing a section view of Slip stroke cylinder 21, drain duct 37, mechanical shut-off valve 46 and Squeezing stroke length setting hydraulic cylinder 22.

FIG. 3 is graph, to be followed for deriving advance length of piston rod 33 of Squeezing stroke length setting cylinder 22 for the desired Squeeze stroke length. This graph is scatter line graph of points joining, positions of Front plate 31 from the end point of total shot stroke (X axis) and corresponding balance gap reduction length at that position (Y axis). Said gap is the distance between Front plate 31 and Cross head plate 17.

FIG. 4 is a sectional view showing basic structure of the conventional die casting machine and illustrates the associated details of injector stroke. FIG. 5 is a graph showing respective movement lengths and positions of Shot cylinder piston rod 16, Front plate 31 and Injector plunger rod 14.

FIG. 6 is showing estimated injection stroke profile, Velocity curve, Metal pressure curve and Stroke advance of the present invention in comparison with an example of conventional mechanism injection stroke profile of the same parameters.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

A preferred embodiment of the present invention will be described below with reference to drawings and it will be followed by the description of comparative non limiting example. The present embodiment is conducted by modifying conventional machine injector mechanism, by replacing its hydraulic intensifier and its dedicated accumulator by a link mechanism. All other unchanged main components of conventional injection mechanism such as shot cylinder, its accumulator and shot plunger rod can be appropriated. Since the present embodiment does not require any change in conventional control system employed for first two filling phases, it can be appropriated. Accordingly new components such as link mechanism comprising its sub assemblies and control system for intensification phase will be described below. FIG.1 is an overall schematic top view of the present invention shot end containing the link mechanism.

There is single shot cylinder 11, which will drive all injector movements either directly or indirectly, through link mechanism.

All injector motions operated by said shot cylinder will be through pressurized hydraulic fluid supplied by its accumulator and will be regulated by the control system of given conventional injector mechanism. As hydraulic intensifier and its accumulator are eliminated, its associated control system is discarded.

Structure of embodiment mechanism is illustrated in fig. land fig. 2: The Shot cylinder 11 is fixed on Shot End Platen 29. Front end of Shot cylinder piston rod 16 is connected to Cross head plate 17. Link assembly 25 drive end is linked with Cross head plate 17. Rear ends of linked assembly 25 are connected to Intermediate plate 32. Front ends of Link assembly 25 are connected to Front plate 31. Intermediate plate 32 and Front plate 31 slides on guide bars 28. Slip stroke cylinder body 38 is fixed on front plate 31. Injector (shot) plunger rod 14 is connected to Slip Stroke cylinder piston rod 35. Slip stroke cylinder 21 is a single acting cylinder. Piston rod Position detecting hydraulic cylinder 22 is fixed on Cross head plate 17. This cylinder is part of Squeezing stroke length setting mechanism. Two single acting hydraulic cylinders 18 are fixed on rear side of Front plate 31. These cylinders will lock link assembly 25 and also act as stoppers to avoid excess travel of Shot cylinder piston rod 16. Stroke adjustment shafts 19 are connected at rear side of Intermediate plate 32. Hydraulic lock wedges 23 are fitted on rear side of Shot End platen 29. Setting of Stroke length of the present mechanism: As illustrated in Fig. 4 Active sleeve length 90 (filling chamber length) is the length of complete travel of shot plunger rod during dry shot (without metal shot). This active sleeve length varies from die to die. According to design of working of the present mechanism it is required to adjust the stroke length of mechanism after every die set-up change or change in active sleeve length 90.

Intent of this stroke adjustment is to have complete designed travel movement of link mechanism 15 and its front plate 31 so as to employ Link mechanism’s highest mechanical advantage exclusively for intensification phase stroke 89 and not to have its effect on prior filling phase stroke 88 (first two phases). Accordingly length of indirect stroke of Front Plate is constant for all length strokes. Length of direct shot stroke 76 with locked link mechanism is adjusted as per active sleeve length 90.

Active sleeve length is sum of Travel length of Front plate (indirect motion) and Length of direct motion transmission (locked link mechanism) So the length of direct motion transmission is the distance between Shot end platen 29 and collar nuts 24 of stroke adjustment shaft 19.

Accordingly the Stroke adjustment shaft 19 length is adjusted by adjusting the positions of collar nuts 24.

Non limiting example: For Active sleeve length of 850mm and Complete Front Plate travel of 114mm. Distance between Shot end platen 29 and Collar nuts 24 will be 736mm (850-114).

Home positions of involved elements of the embodiment are as follows: Returned (at rear end) Shot plunger 14, Returned Shot cylinder piston rod 16. Slip stroke piston side chamber 36 prefilled. Piston rods 27 of Link assembly locking hydraulic cylinders 18 in advanced position. This condition disables the reduction of gap length between Front plate 31 and cross head plate 17 and locks the link assembly 25.

Squeezing stroke length presetting hydraulic cylinder piston rod 33 advanced by corresponding length for desired squeezing stroke length. Open Hydraulic wedge locks 23.

All above hydraulic operations are carried by pressurized hydraulic fluid supplied by machine pump or hydraulic accumulator.

Non limiting example: According to the graph illustrated in Fig.3, the corresponding advance position of Piston rod 33 of Squeezing stroke length setting cylinder 22 is derived. For aforesaid example of total stroke length 850mm and for Squeezing stroke length of 7.5mm, Piston rod 33 advance position 55 will be 51.3mm. Said advance position of Piston rod 33 is set by actuation of solenoid valve 44, regulated by analog signal of advancement.

This freedom to set (to limit) the squeezing stroke length provides an additional advantageous control for Die caster.

Sequence of the embodiment injector mechanism process events:

Prior to die closing hydraulic accumulator is charged with line pressure. This accumulator provides pressurized hydraulic fluid to shot cylinder through hydro-electric control system.

After die halves closing, forming cavity 82 in between them and pouring molten metal in sleeve 84, then injection shot is initiated.

Shot cylinder 11 stroke starts with its Piston rod 16 carrying Crosshead plate 17, link assembly 25 in locked condition, Front Plate 31 and Intermediate plate 32 sliding on Guide bars 28. During this segment of stroke as link assembly 25 is in locked condition motion force of shot cylinder piston rod 16 is directly transmitted to shot plunger rod 14. At predetermined stroke position 76, Collar nuts 24 on Stroke adjustment shafts hits on Shot end platen 29. When limit switches (not shown in Fig.) have sensed approaching nuts, hydraulic locking wedges 23 are actuated and collar nuts are locked in the position. There is sufficient time for wedge locking as there is no back force till intensification phase (squeezing stroke) is triggered. At this time Intermediate plate 32 gets anchored at the position 76 as it cannot move any further and backward. This event starts motion of links of link assembly 25. Hereafter Shot cylinder rod 16 and Cross head plate 17 drives link assembly 25 and front plate 31. This is start of indirect motion force transmission according to the geometry of link assembly. This switching of direct motion to indirect motion is smooth as Link mechanism geometry is designed in such a way to have force multiplication factor of one during this switchover and next some part of stroke. Total stroke covered having force multiplication factor of one is approximately 92% of total stroke 90.

During this indirect motion transmission stroke, gap in between Front plate 31 and Cross head plate 17 goes on decreasing. Aforesaid limit switches actuation opens open- shut solenoid valve also (not shown in figure). Which allows for pushing back of piston rods 27 of Link assembly locking single acting small diameter cylinders 18, that is hydraulic locks are opened. There is sufficient time for said action as switchover from direct motion to indirect motion takes place with multiplication factor of one. That is there is no immediate motion of front plate 31 with respect to Cross head plate 17. Also for safety parallel spring loaded check valve acting little above line pressure may be provided on return line to allow the said retraction.

The motion of shot cylinder piston rod 16 and indirect motions of front plate 31 and Shot plunger rod 14 are continued.

At the end of filling phase when counter force increases shot velocity starts retarding with building of pressure in shot cylinder 11. This position of pressure building depends on the quantity of molten metal. In case of the present invention by virtue of high momentum inertia due to added mass delays the velocity retardation and provides crucial high momentum during final cavity filling. This delayed retardation dampens high inertia. This is damping of high dynamic force generated by accelerating heavy mass.

On reaching predetermined pressure in the shot cylinder, communication of analog signal of Pressure transducer (not shown in figure) opens solenoid valve 43. This starts draining of Slip stroke cylinder chamber 36, through connected duct 37. This stops indirect movement of die’s Shot plunger rod 14. This is an end of filling phases and start of Slip stroke.

During Slip Stroke, motions of Shot cylinder piston rod 16 and indirect motion of Front plate 31 and Slip Stoke cylinder body 38 fixed on it are continued but Shot plunger rod 14 remains stationary by virtue of cavity filling counterforce. This is situation of stationary piston and moving cylinder body. This is Slip Stroke and during this Slip Stroke motion transmission between Front plate and Shot plunger rod is disconnected.

While Front plate 31 is reaching to the corresponding position 40 to have squeezing stroke through the preset length (Stationary Shot plunger rod at the position 67 where it was at the start of slip stroke), with the reducing gap in between Front plate 31 and Cross Flead plate 17, The advanced Piston rod 33 of squeezing stroke setting cylinder 22 first push closes mechanical shut-off valve 46, just then Conical tip of the rod press rests on the conical step bore of Drain duct 37 and the Drain duct is hermetically blocked. Slip stroke is terminated.

The phenomenon of reducing gap in between Cross Head 17 and Front Plate 31 is used to mechanically shut-off drain duct 37 of Slip Stroke Cylinder 21. This Slip stroke is completed in milliseconds depending on its length and speed of Shot cylinder plunger rod during this time.

The termination of slip stroke restarts indirect motion of Shot plunger rod, but this time motion force transmitted is high by virtue of mechanical advantage of link mechanism. This phase is continued till the end of Shot cylinder piston rod 16 stroke. When drain flow from Slip Stroke cylinder is stopped, cylinder body 38 possessing high motion force, first compresses the enclosed hydraulic fluid in piston side chamber 36 till it overcomes the counterforce of cavity filling, then its piston rod 35 starts to move. Thus intensification phase (squeezing stroke) is initiated.

Link assembly geometry 25 is designed to have increasing force multiplication during squeezing stroke, at 5+ times and for last nearly 1 mm above 13 times.

During intensification phase final multiplied force is transmitted through Slip Stroke Cylinder with building fluid pressure inside chamber 36. This will also act as hydraulic damper.

The excess compression that is, pressurization of hydraulic fluid or intensification pressure inside chamber 36 of Slip Stroke cylinder is regulated by proportional relief valve 41. For safety there is parallel spring loaded check valve with some higher level.

Slip stroke cylinder pressure monitored is equal to desired final intensification force divided by surface area of Piston of Slip stroke cylinder. Where intensification force considered is preferably five times of Shot cylinder force (Shot cylinder pressure * Surface area of Piston of Shot cylinder). Shot cylinder pressure may be regulated accordingly.

During this intensification phase (squeezing) motion, reducing gap between Front plate 31 and Cross head plate 17 has pushed back the advanced Piston rod 33 of Squeezing stroke setting cylinder 22 to its home position ( 0 position). The check valve 45 allows this pushing back, but still there will be sufficient force to hold the hermetical shut-off position of valve 46. This sufficient force is by virtue of surface area difference of piston side chamber and rod side chamber of the cylinder 22.

The Slip Stroke time consumption is compensated by reduction in pressure rise time of squeezing phase by virtue of inertia of moving parts. When shot cylinder stroke is reached to its end 59, Front plate 31 at its end position 09, squeezing stroke is finished with preset length. When Shot cylinder stroke is ended, Cross head plate 17 rests on retracted piston rods 27 of link assembly locking cylinders 18. (Cylinder stroke is equal to Gap reduction length)

After cooling time finished, during die opening solenoid valve 42 opens and fills Slip stroke cylinder with a line pressure to its home position. This activity pushes out the biscuit 92 (plunger follow through). This length of push-out is equal to the length of Slip stroke happened.

On the completion of set Shot plunger return time all moving parts of injector mechanism are moved to their respective home positions. One mistake proofing (Poka-Yoke) is required. It is required to ensure Slip stroke cylinder is pre filled to its home position before Shot plunger rod retuning. Accordingly essential feed- back signal may be included.

At the end of Shot plunger return solenoid valve 43 is opened to pressure line for a short time to ensure the retuning of spring loaded mechanical shut-off valve to its home position.

The advance position of Piston rod 33 of Squeezing stroke length setting cylinder 22 is reset by actuation of solenoid valve 44, regulated by analog signal of advancement. If there is any error of squeezing stroke length, that may be compensated during resetting advance length of Piston rod. Since the present embodiment is the modification of mechanical mechanism of the conventional injector assembly various non limited system control circuits (electric and hydraulic) and alternate control valves may be adapted for the present invention.

Description of non limited comparative example: Data of referred example: Machine locking force 1400 ton, Shot plunger stroke length 850mm, Intensified force 109 ton, Intensification pressure 300 kg per Sq.cm, Shot Cylinder Diameter 215mm.

During intensification phase, the present invention mechanism by virtue of its mechanical advantage provides force multiplication of five plus times. Whereas Conventional mechanism has a hydraulic intensifier with pressure multiplication factor of up to 2 times. The high multiplication factor allows for the reduction of Shot cylinder diameter (area).

The present invention Shot Cylinder of dia.145mm delivers Intensification force of 116 Ton. at shot cylinder pressure of 140 kg per Sq.cm against conventional Intensification force of 109 ton delivered by shot cylinder of dia. 215mm at intensification pressure 300 kg per Sq.cm.

Thus Shot cylinder area is reduced to 45% of conventional size.

However due to inclusion of link mechanism the present invention requires longer Shot cylinder stroke of 944mm to produce Shot plunger stroke of 850mm.Accordingly swept volume of Shot cylinder is reduced to approx. 50% of conventional Shot cylinder. Swept volume reduced from 30.8 liter to 15.6 liter.

Accordingly hydraulic accumulator capacity reduced to approx. 50%. Also an accumulator for hydraulic intensifier is eliminated.

This will reduce accumulator charging time for every shot cycle.

For instance For a pump of 180 LPM accumulator charging time will be brought down from 10.3 sec to 5.2 sec for every shot cycle. (Calculation without any spare capacity) Similarly Shot cylinder rod side chamber volume is reduced. This will make energy saving during returning of Shot Plunger rod.

This is considerable energy saving and machine running cost saving.

Effects of mass addition:

It is estimated that the present invention has added mass of 500kg (for 1400Ton machine), about four times with respect to estimated 125kg mass of moving parts of conventional injector mechanism.

That is moving parts mass of the present invention will be approx five times of conventional injector.

Comparative momentum at velocity of 5 m/s.: Conventional Injector momentum will be 625kg. m/s. (125 * 5)

The present invention Injector momentum will be 3125kg. m/s. (625* 5) As illustrated in the Fig. 6:

Increased mass will require higher driving force, means higher pressure to create the force. This relatively higher pressure building will take some time resulting in somewhat slow start and lower acceleration 71. This increased moving mass will increase shot motion momentum and inertia.

However velocity rise position may be shifted short accordingly.

Once the high velocity attained after acceleration said additional pressure rise provides higher metal pressure 72 for cavity filling.

In case of the present invention by virtue of high momentum inertia delays the velocity retardation 74 at the end of filling phase and provides crucial high momentum when there is highest cavity filling counter force due to flow turbulences during final cavity filling. This delay for velocity retardation compensates the lower acceleration during velocity rise.

In case of the present invention by virtue of high momentum inertia and high force multiplication factor towards the end of stroke will reduce time of final metal pressure rise (squeezing) 75.

In Fig. 6 slip stroke event 73. This is anticipation for Slip stroke of 40mm, corresponding Shot cylinder piston rod stroke of 81mm is completed in 0.03 sec at the speed 2.7m/s.