MXPA98001491A - Method and apparatus for providing protection against overloading in machines for molding by compress - Google Patents

Abstract

A method and apparatus for making plastic articles using a plurality of tools, each of which is moved by cams and includes a nitrogen cylinder where the provision is made for the prevention of catastrophic overload. For the prevention of catastrophic overload, one of the cams is supplied by a top plate and is held in a fixed, normal position by a plurality of nitrogen cylinders. The abnormal movement of the upper plate is detected and the machine stops. For protection against overload a pressure indicator is placed in the inactive load position of one of the cams and any excessive load provides a signal for an alarm, which interrupts the feeding of plastic loads and the stoppage of the machine.

Description

METHOD AND APPARATUS FOR PROVIDING PROTECTION AGAINST OVERLOADING IN MOLDING MACHINES BY COMPRESSION FIELD OF THE INVENTION This invention relates to compression molding machines and particularly to protection against overloading for compression molding machines.

BACKGROUND AND BRIEF DESCRIPTION OF THE INVENTION It is common to compression-mold plastic articles that include closures, as contrasted to the injection molding of plastic articles. Typical patents include U.S. Patent Nos. 2,072,536, 2,155,316, 2,218,456, 2,402,462, 2,891,281, 3,210,805, 4,296,061, 4,314,799, 4,343,754, 4,355,759, 4,497,765, 4,640,673, 4,755,125 and European Patent Application No. 0 091 653 A2. In the compression molding of plastic articles, there are inherent variations that can affect the resulting articles. One such REF: 26864 variations is the manufacturing tolerance applied to the tools. Therefore, the molding assemblies in a machine are not identical. In this way, when the tools are adjusted in the molding position, the volume of the space between the molding surfaces varies between the mold assemblies. An additional variation is the weight and / or volume of the plastic load that is placed inside each mold assembly. In the patent application identified above, Serial No. 08 / 473,479 filed June 7, 1995 and US Patent No. 5,554,327 incorporated herein by reference, an invention is described which provides a method and apparatus for molding by compression of plastic articles including closures, wherein the forming pressure can be controlled accurately; wherein the forming pressure can be easily adjusted; wherein the lateral forces in the tooling are not directly applied to the forming tool; where the tooling can easily be replaced; where the number and size of the tool stations can be easily changed; and wherein various types and sizes of articles including closures can be easily made by changing the tooling and the associated drive mechanisms; wherein the tooling will be compensated by variations in the weight of the mass of compressed material or load, variations in the volume of the tooling of the mold in the closed mold position and where a substantial overload such as a double load of plastic can be absorbed easily without overloading the tooling or the overall device. In the aforementioned patent application Serial No. 08 / 473,479, the method and apparatus for compression molding of plastic articles including fasteners includes providing co-actuation devices for tools that include a first device for moving a core and a core jacket in engagement with a hollow mold relative to a second tooling device. The first tooling device includes an impeller between the tooling and a fixed, upper cam. The second tooling device includes an impeller that supports the hollow mold and is associated with a fixed, lower cam. A gas cylinder charged with atmospheric gas at a predetermined pressure, preferably nitrogen, is provided in the second tooling device and controls the compression molding force. In a preferred form, a plurality of tooling devices are provided in circumferentially spaced relationship on a rotating turret supported by a central column. A common distributor supplies the pressure at a precisely controlled pressure to each of the nitrogen cylinders. In the compression molding machines described above, the individual tooling assemblies within the tooling series are each capable of absorbing tool shocks, excessive to approximately 1.27 cm (1/2 inch) while the normal deflection of the tooling is in the order of approximately 0.0762 cm (0.030 inches). During normal operating conditions, an occasional overload such as a double mass of compressed material, can be suitably absorbed by the nitrogen cylinder without exceeding the force of the limiting mold controlled by the nitrogen pressure in the system. However, a slow increase of resin cured with the tool, can eventually completely extend the stroke of the nitrogen cylinder, thus, nullifying the force that limits the characteristic of the nitrogen cylinder. In addition, a foreign body inadvertently introduced into the cavity can immediately cause an overload in the tooling as the tooling is closed by opposing the fixed cams. Among the objectives of the present invention is to provide a method and apparatus for providing protection against overload for compression molding machines.; that prevents the damage to the machines; which may include protection against overload, catastrophic; and that may include the detection of productive overload. According to the invention, a movable upper plate supports a rigid cam including a profile of the cam. At least one nitrogen cylinder acts downwardly on the top plate to maintain the top plate and the profile of the cam in a fixed position during normal machine loading. A support bracket supports the nitrogen cylinder and is secured to the base of the machine by a support member or by additional supports connected to the base of the machine. During normal operation, normal variations in the size of the mass of compressed material are compensated for by the gas cylinder within the second or lower device of the tooling as shown in the aforementioned patent application. If the load on the desired maximum predetermined machine (force) is exceeded as controlled by the nitrogen pressure to the nitrogen cylinder positioned with respect to the upper plate, the upper plate rises upwardly against the nitrogen cylinder, and in this manner the load is released. In one form, this movement is perceived by a switch and the operation of the compression molding machine stops to provide protection against catastrophic overload. In another form, a pressure indicator placed at the inactive load position of the cam continuously monitors the forces on the cam and is used to provide a signal of a condition that could lead to a catastrophic overload and to initiate action to prevent the catastrophic overload.

In the preferred embodiment, an upper cover plate is pivoted from 2 supports such that it will rise out of the forming area. A taper pin positioning system is provided in the forming area, therefore the top plate can be raised, and still move into the tapered spikes since this is re-engaged after the overload is removed. The detection means are required for lifting the upper plate, and a pivoting means is required in the alternating support structure. The spring means is provided to retain the top plate. In the form to prevent a catastrophic overload encountered during the cam shaping and retention stage, the impact of the nitrogen cylinder within the tooling is exceeded, which causes a "solid condition" of the tooling exhaust, and the force The resultant exceeds the opposing force of the nitrogen cylinder which retains the upper plate in a fixed position. This force exceeds the holding force in the upper plate and the cam allows the plate to rise to adjust the abnormal condition. The detection means signals the displacement of the upper plate, and initiates an emergency stop in the machine and a rapid depletion of the upper plate that holds the nitrogen cylinder. Therefore, the overload condition is avoided, and the machine is secured until the overload condition is removed and the machine is readjusted for normal operation. In the form to provide protection against overload, predictive, a pressure gauge placed adjacent to the inactive load position of the cam continuously monitors the forces in the upper cam. In the case of excessive loading, force is applied to one of the tooling devices. The pressure gauge signal with associated controls is used to signal an alarm, interrupt the feed of extruded loads in addition to other tooling, and stop the machine so that the affected tooling stops in one position for an operator to service the tooling.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a top plan view of a compression molding machine to which the invention is applied.

The figure. 2 is a sectional view taken along line 2-2 in FIG. 1.

FIG. 3 is a view similar to FIG. 2, the parts that are separated.

FIG. 4 is a sectional view taken along line 4-4 in FIG. 1.

FIG. 5 is an elevation view, sectional, partly of a compression molding machine including the invention.

FIG. 6A is a sectional, vertical view of a device of the upper and lower tooling.

FIG. 6B is a sectional, fragmentary view on an enlarged scale of the lower mount of the tooling device shown in FIG. 6A.

FIG. 6 is a top plan view of the compression molding machine including the invention.

FIG. 7 is a plan view, fragmentary on an enlarged scale of a portion of the compression molding machine shown in FIG. 6 FIG. 8 is an elevational, sectional, partly, fragmentary view of the portion of the machine shown in FIG. 7 FIG. 9 is a sectional, fragmentary view taken along line 9-9 in FIG. 7 FIG. 10 is a sectional, fragmentary view taken along line 10-10 in FIG. 6 FIG. 11 is a sectional, fragmentary view of an assembly of a conical spike shown in FIG. 9.

FIG. 12 is a diagram of a form of controls used for the machine for the detection of overload, predictive.

FIG. 13 is a schematic diagram of another form of controls for the machine for protection against catastrophic overload.

FIG. 14 is a schematic presentation showing the control of a machine for the detection of overload, predictive.

FIG. 15 is an electronic schematic of the detection of predictive overload and protection against catastrophic overload shown in FIGS. 13 and 14.

DESCRIPTION OF THE PREFERRED MODALITY The invention is described herein as being applied to a compression molding machine as described in U.S. Patent No. 5,554,327 and patent application Serial No. 08 / 473,479 filed on June 7, 1995, previously mentioned, incorporated by reference. With reference to FIGS. 1-4, the method and apparatus including the invention is adapted to be applied to such a compression molding machine which includes a rotating apparatus including a base 20, supporting a column 21 in which a turret or carousel 22 is mounted in a rotary manner by the tapered, upper and lower bearings 23, 24. The turret 22 includes vertically spaced supports comprising a top, annular support 22a, an annular support 22b, and an annular, lower support 22c. A plurality of upper support segments 25 are mounted on the upper support 22a and supported to define a ring. A plurality of lower segments 26 are mounted on the intermediate and lower supports 22b, 22c and abut to define a ring. Each segment 25 supports one or more devices circumferentially spaced from the impellers 34. Each segment 26 supports one or more impellers 52 adjacent to the lower end of the apparatus. The impellers 34 are mounted for vertical movement in the housings 34a devices in the support segments 25 which, in turn, are supported in an upper ring support 22a (FIGS 2, 3). A tooling upper device 27 is associated with each impeller 34 and includes a movable assembly 27a device at the lower end of the impeller 34 and a fixed mounting 27b device at a portion 26a of the segment 26 that is fixed to the support 22b. A fixed annular cam 29 is supported by the columns 30 (FIGS. 1, 4) and associated with the upper impellers 34. The impeller 34, in turn, has a cam roller 35 at its upper end for coupling the cam 29. A lower tooling device 28 is mounted on each lower impeller 52. A fixed annular cam 31 is supported on the base 20 and associated with the lower impellers 52. With reference to FIG. 6B, each lower mounting 28 of the tooling includes a mounting of the female mold 51 and a cooling water distributor 51a. Each impeller 52 has a roller 60 at its lower end for coupling the cam 31. The fixed assembly 27b is mounted on a segment portion 26a of the segment 26. The movable assembly 27a comprises a mold or core plunger 41, a sleeve of the spring loaded core 42 pushed upwardly by the springs 45 and a spacer sleeve 44 pushed downwardly by the spacer springs 43. The core 41 is made in several sections and defines a male mold. Each impeller 52 is mounted on a support body 50 that forms part of the segment portion 26b. The mold 51 has relative movement, limited with respect to the impeller 52 and is pushed without resistance upwardly by the cavity springs 53 which act by thrust pins 54. The lower impeller 52 further includes a plunger 55 which engages a plug of the spring retention 56 which, in turn, couples the piston 57 of a nitrogen cylinder 39. A centering spring 59 is interposed between the stopper of the retaining spring 56 and the plunger 55. The nitrogen cylinder 39 is supplied with nitrogen to a pressure determined exactly supplied to the area or chamber 61 under the nitrogen chamber 39 through a connector 62 having a hole. In this style of tooling, the molding force is applied through the sleeve of the core 42 and the core 41 is fixed to the sleeve of the core 42 by the lost motion connection, the core 41 is derived upwardly by the series of springs 45. The cam upper 29 is fixed and the core sleeve 42 therefore moves down a fixed stroke or stroke as controlled by the upper cam 29 (FIG 6A). The one-piece hollow mold 51 is located in the lower tool driver 52 but is free to axially move a limited amount relative to the driver 52 and the hollow mold is aided by the series of springs 53 within the lower tool driver 52. These springs 53 are limited in stroke or stroke by push pins 54, which rest on a retention device for the thrust pin 54a. The hollow mold 51 rests on the plunger 55, which is retained to limit its upward travel. The plunger 55 connects the cap of the retaining spring 56 and a spring 59 fits between the 2 components. The stopper of the retaining spring 56, in turn, brings the piston rod 57 of the nitrogen cylinder 39 into contact. The nitrogen cylinder 39 is normally completely traversed, keeping the stopper of the retaining spring 56 against the surface of the cylinder. located stop 52a in the lower tool driver 52. The plunger 55, when free, will rise by the center spring 9 until it reaches a stop surface 52b within the lower tool driver 52. The provision is made to lower the upper impeller 34 and comprises the first roller 35 at the upper end thereof for coupling the upper cam 29 to cause downward movement of the male mold assembly 32. Furthermore, a second roller 70 is provided for rotation about the same axis as the roller 35 engaging a second fixed upper cam 72 (FIG. 2) to lift the upper tooling 27 during the operation cycle in order. The provision is made to lift the lower impeller 52 and comprises a roller 60 on the impeller 52 which engages the lower cam 31. In addition, a second roller 74 is provided for rotation about the same axis as the roller 60 and engages a second cam lower fixed 77 to ensure that the hollow mold 51 is in its lowermost position to receive a mass of compressed plastic material.

During normal operation, within the shaping and retention sections (FIG 12), control of the molding force is achieved with minimal compression of the gas cylinder, for example, in the order of 0.0762 cm (0.030 inches). This control is maintained despite small variations in the volumetric capacity of the closed molds, and in spite of small variations in the weight of the masses of compressed material supplied. When the tooling transitions to the inactive load section, the upper cam has a small elevation (approximately 0.127 cm (0.050 inches)) that allows the nitrogen cylinder to make a one-way stroke and therefore substantially inactivates the load of the Mold strength. Then the force is reduced to that of the spring for the plunger in the lower tooling of approximately Force 100-150 This reduction in the compression force in the tooling minimizes the load on the structure of the machine that should exist unless the normal mold force is applied through the machine cycle. During an abnormal operating condition, which results from an excessive load of material or the introduction of a foreign body into the cavity will be kept down at a lower level than would be in the case of a normal load, by compressing the nitrogen cylinder in the lower tooling also what would be the normal condition. If this condition does not completely compress the nitrogen cylinder 39, then the molding force will be normal in the shaping and retention portion of the cycle. Clearly, there could be a condition such as the tooling transitions to the inactive load portion of the upper cam (FIG 12) and finds the stepped elevation which is in the order of 0.127 cm (0.050 inches), the cylinder of nitrogen 39 could remain partially compressed, and the piston spring 59 would be ineffective. Under this condition, the tooling will apply an abnormal rising force in the order of Force 1000 # in the upper cam that results from the pressurized gas cylinder 39 in the lower tooling, and that greatly exceeds the normal Force force of 100-150 If this abnormal condition is limited to an individual tool station, then it can be considered negligible from the point of view of loading the machine, but undesirable since the molded part will be defective, and in addition the part could fail to be disassembled from the tooling and cycle through the machine for a second time, with an additional load of material. The above condition could be described as a non-catastrophic overload. A mass load of excessive compressed material or a mass of solidified compressed material or other foreign body within the tooling cavity, or at any position within the tooling, can cause a solid condition of the tooling exhaust pipe. In this case, the nitrogen cylinder 39 within the tooling becomes completely compressed and no longer exists, thereby causing the tooling to exert excessive force against the cams. If present, this condition will become evident at some point within the cam shaping section as the tooling turret attempts to drive the tooling through the shaping section. The forces generated by this type of overload could cause severe damage to the structure of the machine and could be described as a catastrophic overload condition. It is the object of this invention primarily to provide a means to prevent a catastrophic overload of the structure of the machine, and secondly to provide an overload caution signal in the non-catastrophic machine, and in addition to contact a switch for the appropriate machine for the present overload condition. A further object of the invention is to provide a machine having continuous integral cams. With reference to FIGS. 5, 7-11, according to the invention, the compression molding machine, described above is modified such that an upper plate 80 supports the fixed cam 84 and is mounted for upward movement relative to a fixed plate 81 in the structure. At least one nitrogen holding cylinder 82 (FIG. 8) is provided on the upper plate 80 which covers the cam shaping area to maintain the upper plate 80 in the normal operating position. The nitrogen holding cylinder 82 is pressurized to provide a holding force which exceeds the normal forces on the cam 84 as the successive devices of the tooling move along the cam 84. When the top plate 80 is subjected to a Overload exceeding that normally encountered and compensated by the gas cylinder 39 within the tooling, the top plate 80 is inclined by bringing the associated cam 84 upwardly to release excessive force on the machine structure. A support bracket for the nitrogen cylinder 86 is secured to the base of the machine by a support member or by additional supports connected to the base of the machine. If the predetermined, desired maximum machine load (force), as controlled by the nitrogen pressure for the nitrogen cylinder 82, is exceeded, the top plate 80 is raised against the nitrogen cylinder 82, and therefore releases the load on the tooling and the structure of the machine. The preferred movement of the top plate 80 is pivoted from 2 supports and raised in the area of the forming area, where the force overload would first be induced. A system for the conical spigot is provided in the conforming area, therefore the upper plate can be raised, and it still shifts on the conical spike as it recovers after removing the overload. Detection means are required for lifting the upper plate, and appropriate pivoting means are required in the structure. The spring means is provided at the pivot points to retain the top plate. According to the invention, the upper plate 80 is located in the annular plate 81 by 2 assemblies of the spherical pin 90, and a mounting of the conical pin 92. The annular plate 81 is mounted to the support columns which are assembled at the base of the machine. The spherical pin mounts 90 are located in an axial plane perpendicular to a radius X to the cam shaping section, for example, in circumferential positions of about 120 degrees apart and placed symmetrically relative to the X radian through a position of conformation of the cam of 20 degrees. A plurality of nitrogen retention cylinders 82 are placed in the lower part of a clamping bracket bolted to the structure of the machine (FIGS 8, 9). Each retaining cylinder 82 includes a piston 83 that engages the upper plate 80 that covers the forming area of the cam 34 (FIG 8). The nitrogen cylinders 82 are loaded at a pressure such that the resulting holding force in the upper plate 80 is less than or equal to the maximum design operating load in the machine. With reference to FIG. 10, each spherical pin assembly 90 is mounted on the structure of the machine and includes a body 100 and extends into an opening in the top plate 80. With reference to FIG. 11, the cone pin assembly 92 includes a conical spike 118 and extends in the conical bearing 100 in the top plate 80. FIG. 12 illustrates diagrammatically the upper and lower cams and shows the representative tooling positions relative to the sections of the cam for descriptive purposes only. For a detailed understanding of the tooling configuration, reference is made to the aforementioned patent application Serial No. 08 / 473,479, incorporated herein by reference. The retention force acting downwardly on the top plate 80 is generated by the nitrogen retention cylinders 82 (FIG. 5) and is pre-set by the adjustment of the nitrogen pressure in the cylinders 82. The normal molding forces act on the upper cam 84 occur substantially in the area of the final portion of the conformation cam, and in the entire area of the retention section, during which time the mold force limiting the effect of the nitrogen cylinder of the lower tooling 39 is effective. With reference to the diagram in FIG. 12, it can be seen that with this example, a maximum of 6 tools will be placed anywhere and it is possible to calculate the generated upward force. In practice, the additional smaller forces occur in normal operation due to the effect of the plunger springs 59 in those tooling in the inactive load section. With reference to FIGS. 6 and 9, a number of lifting springs of the upper plate 95 are shown. These springs act ascendingly against the upper plate 80, thereby providing a lifting force against the upper plate 80. The aim is to ensure that once the upper plate 80 starts to rise against the nitrogen holding cylinders 82, its movement is detected and the nitrogen can be immediately exhausted from the cylinders 82. Then the aforementioned springs 95 lift the upper plate 80 and maintain the clearance on the tools for easier clearance of the obstruction condition. Although springs 95 are preferred, protection against catastrophic overload can be effected to a if springs 95 are omitted. Protection against catastrophic overloading is to ensure that the machine does not experience a load on the structure above and above the specification of design with appropriate safety factors in place. The net force holding the top plate 80 takes into consideration the effective weight of the top plate assembly around its pivot points, the downward force generated by the top plate which retains the nitrogen cylinders 82, and the upward force of the springs 95 if provided, is equal to or less than the maximum design force that can be tolerated by the structure of the machine with the appropriate safety factors in place. This net force must also be appropriately greater than the upward force in the top plate assembly applied by the tooling during normal molding conditions. The pressure adjustment, appropriate for the upper holding cylinder can be established empirically, or by calculation. With reference to FIG. 13, when a contact or air switch S device in the fixed plate 81 in the forming area detects a lifting of the upper plate (80) relative to the fixed plate (81), provides a signal to stop the machine and eliminate the pressure in the holding cylinders 82 by driving a solenoid valve. The detection of catastrophic overload as previously described is to provide protection against total overload conditions and as such is less sensitive to lower force loads. In the case of a predictive overload detection, the objective is to provide a warning of a condition that could lead to a catastrophic overload condition. With reference to FIGS. 12, 14 and 15, a pressure gauge L is immediately placed at the beginning of the inactive load section of the cam 84 and assembled in a manner well known in the art. As previously described, and under normal molding conditions, the upward force in the inactive load section of the cam 84 generated by the plunger spring of the tooling 27 may be, for example, in the order of Force 100 # per tooling . In the case of double masses of molten compressed material being inserted into the cavity, the forming force in the molding is sufficient to form the article, and the nitrogen in the lower tooling 39 will be compressed more than normal. However, if the lower nitrogen cylinder 39 is not fully compressed, the generated molding force will be normal in the forming and retaining sections of the cam 84. As this tool progresses to the inactive loading section of the cam 84, the elevation for example, 0.172 cm (0.050 inches) in this portion of the cam 82 is insufficient to allow the lower nitrogen cylinder to fully extend, and consequently the force generated by the nitrogen cylinder 39 of the lower tool 28 is applied. to the upper tool 27 and in turn to the upper tive load portion of the cam 82. As the force generated by this cylinder may be, for example, in the order of at least Force 1000 #, contrary to the normal force generated by the Force plunger spring 100-150 #, can be easily detected by the pressure gauge L and the associated controls immediately when the upper roller cam comes into contact with the pressure gauge impeller. This abnormal condition can be used appropriately to signal an alarm and / or a switch for the controlled machine. For example, as the cam roller driver 35 of the specific tooling engages the pressure indicator L, the abnormal load will be detected, and in conjunction with associated controls that include a proximity switch of the station count P, a signal it can be started to identify the damaged tool and to stop instantly feeding the masses of compressed material or extruded plastic loads to the tooling. In this way, the subsequent tooling that was in the progress of the mechanism of supply of mass of compressed material in the time of detection will not have masses of compressed material inserted, and only the few tools at that time contained between the material mass cutter compressed and the specific tooling that caused the predictive overload warning will have a load of material. As shown schematically in the FIG. 14, the controls will identify the path of the particular tooling and will bring the turret of the machine to a controlled stop such that the tooling with the excess load is presented to the position of the operator in the machine. This will allow the operator to attend to the specific tooling that has the excessive load, which causes the warning signal for predictive overload. For example, in the event that 2 successive tooling or more than a tooling in some turret revolution is detected as a predictive overload condition, the machine can be stopped in an emergency stop mode to quickly stop the machine and allow the operator attends to correct the problem. When the tooling has cleared, and the remaining seals on the following tools have been removed from the tooling, the machine can be quickly re-started, and continue to produce in the normal manner. The specific tooling that has the load of excess material had been allowed to continue unattended, it is possible that an additional load of material in the cavity, and a possible non-device closure remaining in the tooling core could cause a subsequent catastrophic overload, and initiate the protection against catastrophic overload previously described. To recover from the previous condition, it exceeds that of the described predictive overload condition. The controls for performing the above sequence are well known and understood by those skilled in the art of sequential control design and typically could be programmed into the PLC logic controller of the machine, shown schematically in FIG. 15. The PLC control also receives a signal from the top plate switch S to provide the catastrophic overload signal to prevent a catastrophic overload condition. Preferably, both the protection against catastrophic overload and the protection against predictive overload are combined in the compression molding machine with a tiltable top plate. However, any type of control can be used separately. In addition, the predictive overload protection can be applied to the inactive load portion of the fixed cam 29 of the compression molding machine shown in FIGS. 1-4. In this way, it can be seen that a method and apparatus for providing overload protection for compression molding machines has been provided; that prevents damage to machines; which may include protection against catastrophic overload; and that may include predictive overload detection, while upper and lower, integral, continuous cams are used.

It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects to which it relates.

Having described the invention as above, property is claimed as contained in the following:

Claims (51)

1. A method for compression molding a plastic article, characterized in that it comprises providing a first tool assembly having a male mold associated therewith, providing a second tool assembly having a hollow mold associated therewith, providing a first cam fixed to move the first tool assembly relative to the second assembly and a second cam fixed to move the second tool assembly relative to the first assembly, each of the cams has a shaping section, a retaining section and a section of inactive load, interpose a first fluid cylinder comprising a fluid-filled chamber and a piston in the second tool assembly interposed between the second cam and the second tool assembly for pushing the second tool assembly towards the first tool assembly for provide a molding force, limitation, constant during the complete movement of the second tooling under the activation of the second cam, providing the fluid in the first fluid cylinder at a predetermined pressure to provide a constant molding, limiting force during shaping of the plastic article of the associated tooling under the driving of the cams, provide a load of extruded material to the cavity of the hollow mold, - move the first and second assemblies under the action of the cams fixed to move the first assembly and the second assembly of the mold towards another to close the mold and provide a limitation molding force, constant in the load to compress the load to form an article, the improvement comprising the support of the first cam fixed for limited movement relative to the first tool assembly, supporting one of the first fixed cam and the second cam fixed for limited permissible movement when a predetermined force is applied to the first fixed eva, perceive the load in one of the first fixed cam and the second fixed cam, and provide a signal when the load of the first fixed cam exceeds a predetermined value.

2. The method according to claim 1, characterized in that it includes providing at least a second fluid cylinder comprising a chamber filled with fluid and a piston for pushing the cam having limited permissible movement with such force to retain the cam in a fixed position relative to the tooling during normal operation and the first fluid cylinder associated with the second tooling adapts the normal variations in the loads.

3. The method according to claim 2, characterized in that it includes the release of the fluid pressure in the second fluid cylinder when the position exceeds a predetermined value.

4. The method according to claim 3, characterized in that the support step of the fixed cam comprises providing an upper plate which supports the upper fixed cam.

5. The method according to claim 4, characterized in that the supporting step of the first fixed cam comprises the pivoting of the upper plate for the permissible movement in the forming section of the first fixed cam.

6. The method according to claim 5, characterized in that the pivoting step of the upper plate comprises providing the assemblies of the spherical pin spaced in a plane perpendicular to a radian through the forming section of the first fixed cam.

7. The method according to claim 6, characterized in that it provides a spaced location pin assembly that engages the upper plate.

8. The method according to claim 7, characterized in that it includes providing springs that oppose the force of the second fluid cylinder.

9. The method according to claim 8, characterized in that it includes providing a plurality of second fixed cylinders.

10. The method according to claim 4, characterized in that the detection step comprises the positioning of a switch associated with the upper plate in the cam shaping section in association with the cam having limited movement.

11. The method according to claim 10, characterized in that the detection of the position signal causes the activation of an alarm.

12. The method according to claim 10, characterized in that it includes the use of the signal to stop compression molding.

13. The method according to claim 12, characterized in that it includes the use of the signal to release the pressure in the second cylinders.

14. The method according to claim 10, characterized in that the detection step comprises the positioning of a pressure indicator associated with the inactive loading section of one of the fixed cams.

15. The method according to claim 14, characterized in that it includes the use of the signal of the pressure indicator to provide signal when the force in the fixed cam exceeds the force normally applied to the tooling assembly in the inactive load section of the fixed cam .

16. The method according to claim 15, characterized in that it includes the use of the signal to interrupt the step of providing loads of extruded material to the successive tooling.

17. The method according to claim 16, characterized in that it includes the use of the signal to stop the movement of the first and second tool assemblies.

18. The method according to claim 16, characterized in that it includes the use of the signal to stop the movement of the first and second tool assemblies such that the signal provided by the tooling is presented in a position accessible to the operator.

19. The method according to claim 16, characterized in that the interruption step comprises the deviation of the loads out of the position received in the cavities.

20. The method according to claim 15, characterized in that it includes the use of the signal to release the pressure in the second cylinders.

21. The method according to claim 10, characterized in that the detection step comprises the positioning of a pressure indicator associated with the inactive loading section of the first fixed cam.

22. The method according to claim 21, characterized in that the detection of the position signal causes the activation of an alarm.

23. The method according to claim 22, characterized in that it includes the use of the signal to stop compression molding.

24. The method according to claim 22, characterized in that it includes the use of the pressure indicator signal to provide a signal when the force on the first fixed cam exceeds the force normally applied to the first tooling assembly in the inactive load section of the first cam fixed.

25. The method according to claim 24, characterized in that it includes the use of the signal to interrupt the step of providing loads of extruded material to the successive tooling.

26. The method according to claim 25, characterized in that it includes the use of the signal to stop the movement of the first and second tool assemblies.

27. The method according to claim 24, characterized in that it includes the use of the signal to stop the movement of the first and second tool assemblies such that the signal provided by the tooling is presented in a position accessible to the operator.

28. The method according to claim 25, characterized in that the interruption step comprises the deviation of the loads outside the position that is received in the cavities.

29. The method according to claim 24, characterized in that it includes the use of the signal to release the pressure in the second cylinders.

30. The method according to any of claims 1-29, characterized in that it includes providing a series of devices of the first tool assemblies, the second associated tool assemblies and the first associated fluid cylinders and second set cylinders having the pressure maintained therein at the predetermined pressure to provide a molding, limiting, constant force for each tooling mounting device not affected by the other tool mounting devices during the complete movement of the associated device under the activation of the cams, the movement of the devices of the assembly of tools successively in an endless road beyond a station where a load of extruded material is successively released to a hollow mold, in addition the movement of the devices of the tooling successively passes to the fixed cams such that the cams cause each device A first tool assembly and a second tool assembly close the mold and provide a constant molding force on the load to compress the load to form an article.

31. An apparatus for the compression molding of a plastic article, characterized in that it comprises a first mold assembly having a male mold associated therewith, a second mold assembly having a hollow mold associated therewith, a first fixed cam to move the first mold assembly relative to the second mold assembly, a second cam fixed to move the second mold assembly relative to the first mold assembly, each of the cams has a shaping section, a retention section and a section of inactive load, a fluid cylinder has a chamber filled with fluid at a predetermined pressure and a piston in one of the tool assemblies interposed between one of the first fixed cam and the first mold assembly and the second fixed cam and the second mold assembly and that pushes a tool assembly towards the other tool assembly interposed with each other to provide a mold, limiting force n, constant during the full movement of the associated tooling under the activation of the cams, a means for supporting one of the first fixed cam and the second cam fixed for limited movement relative to the first tool assembly, a means for detecting the load in the fixed cam, a means for providing a signal when the movement exceeds a predetermined value.

32. The apparatus according to claim 31, characterized in that it includes means for supporting the first cam fixed for limited permissible movement when a predetermined force is applied to the first fixed cam, at least one second cylinder of fluid comprising a chamber filled with fluid and a piston that pushes the first cam downwardly with a force such as to retain the first cam in a fixed position relative to the tooling during normal operation and the first fluid cylinder associated with the second tooling adjusts normal variations in loads.

33. The apparatus according to claim 32, characterized in that it includes a means for releasing the fluid pressure in the second fluid cylinder exceeding a predetermined value.

34. The apparatus according to claim 33, characterized in that the means supporting the fixed cam comprises an upper plate supporting the upper fixed cam.

35. The apparatus according to claim 34, characterized in that it includes a means for pivoting the upper plate.

36. The apparatus according to claim 35, characterized in that the pivoting means of the upper plate comprises spherical pin assemblies spaced diametrically opposite the forming section of the first fixed cam.

37. The apparatus according to claim 36, characterized in that it includes assemblies of the spaced locating pin, which engages the upper plate.

38. The apparatus according to claim 37, characterized in that it includes springs that oppose the force of the second fluid cylinder.

39. The apparatus according to claim 38, characterized in that it includes a plurality of second fluid cylinders.

40. The apparatus according to claim 34, characterized in that the detection means comprises a switch placed adjacent to the forming section of the first fixed cam.

41. The apparatus according to claim 40, characterized in that the switch produces a signal when activated by the movement of the first fixed cam.

42. The apparatus according to claim 41, characterized in that it includes a means activated by the signal for stopping the compression molding apparatus.

43. The apparatus according to claim 42, characterized in that it includes a means activated by the signal to release the pressure in the second cylinders.

44. The apparatus according to claim 34, characterized in that the detection means comprises a pressure indicator placed adjacent to the inactive load portion of the cam and a circuit continuously monitoring the pressure indicator.

45. The apparatus according to claim 44, characterized in that the means responsive to the pressure indicator provides a signal when the force in the first fixed cam exceeds the force normally applied to the first tooling assembly in the inactive load section of the first fixed cam .

46. The apparatus according to claim 45, characterized in that it includes a means responsive to the signal for interrupting the medium that provides the loads of extruded material to the successive tooling.

47. The apparatus according to claim 46, characterized in that it includes a means responsive to the signal to stop the means for movement of the first and second tool assemblies.

48. The apparatus according to claim 47, characterized in that it includes a means responsive to the signal to stop the means for movement of the first and second tool assemblies such that the tooling is presented in a position accessible by the operator.

49. The apparatus according to claim 46, characterized in that the means for interrupting the means providing loads comprises the deviation of the loads outside the position to be received in the cavities.

50. The apparatus according to claim 45, characterized in that it includes a means sensitive to the signal to release the pressure in the second cylinders.

51. The apparatus according to any of claims 31-50, characterized in that it includes a series of devices for first tool assemblies, second assemblies of associated tools, and first associated fluid cylinders and second associated fluid cylinders having the pressure maintained in the same at the predetermined pressure to provide a molding, limiting, constant force for each mounting device of the tooling not affected by the other tooling mounting devices, means for moving the tooling mounting devices successively on an endless path beyond a station, where a load of extruded material is successively supplied to a hollow mold, and then successively passed to the fixed cams to cause each device of the first tool assembly to close the mold and provide a molding force, limitation, constant in the to compress the charge to form Ar an article.