Compression molding apparatus

Abstract: A compression molding apparatus for instantaneously applying a high pressurizing force in the final stage of compression molding comprises a gear (7) mounted on a screw shaft (5) and rotatable by a pair of pinions (11) driven by a pair of hydraulic motors (12), to drive a plunger (3) which compresses a composite material (A). In the final stage, by using a pair of pressure actuators (10) provided in a pressure applying system (6), pressurizing force is instantaneously applied through the gear (7) to the screw shaft (5) by a torque arm (8) and a lock-piece (22) respectively.

Description: This invention relates to compression molding apparatus, particularly but not exclusively for forming firebricks. Referring first to Fig. 11, a conventional compression molding apparatus 1h, using a hydraulic press, generally comprises a press frame 2h, a hydraulic cylinder 5h provided on the upper side of the press frame 2h, a pressurization block 4h provided on the lower side of the hydraulic cylinder 5h, and a plunger 3. A composite material A is placed in a cavity defined by a pedestal J and a metal mold I, and is then compressed by pressure from the plunger 3. The pressurization requires 600 mm of stroke and more than 1,500 tons of pressurized force. Repetitive high-speed pressurization, known as "bumping down molding", has recently been adopted for high-density molding pressurization. That is, at the final stage of molding pressurization, a range of 0.1-0.3 mm of compressed deformation is repeated a multitude of times, to increase the density of the molding. In the art described thus far, a very large apparatus, capable of generating the necessary high pressure, is used to create a great force at the final stage of the compression. As a consequence, the apparatus is costly due to the complicated circuitry and the various control valves used for controlling the abundance of highly pressurized flowing oil. There is no convenient means by which the pressurized compression may take place in two stages, instead of employing a fixed high pressure from the initial stage to the final stage of compression. A mechanical friction press is not suitable for avoiding this problem because of the noise and vibration created during the pressurization process. It is therefore an object of the present invention to provide compression molding apparatus of low cost and simple structure which is capable of generating a very large instantaneous pressurizing force at the final stage of compression. DE 547950C discloses compression molding apparatus comprising a screw press in which pressurization is carried out by moving a pressurization block by means of a screw shaft. The present invention is characterised by a gear fixed to the screw shaft, primary means for driving said gear including a pinion engaging the same, and secondary means for driving said gear comprising a pressure applying system engageable with and disengageable from said gear. In one form of the invention the said pressure applying system comprises a torque arm rotatably mounted on the said screw shaft, a mechanical clutch for causing the torque arm and said gear to be engaged and disengaged, and a pressure actuator coupled with the said mechanical clutch. In another form of the invention the said pressure applying system comprises a torque arm rotatably mounted on the said screw shaft and formed with a window at the outer end thereof, a lock-piece mounted in the said window to slide in the radial direction and having gear teeth selectively interlockable with the said gear, a detachable actuator for moving the said lock-piece towards and away from the said gear, and a pressure actuator connected to the end of the torque arm for rotating the same. In a further form of the invention the said pressure applying system comprises a base member fixed outwardly of the said gear, a detachable arm rotatably connected to the said base member at one end, a lock-piece having gear teeth selectively interlockable with the said gear and slidably mounted on a guide shaft on the said detachable arm, a pressure actuator for moving the lock-piece towards and away from the said gear, and a detachable actuator connected to the other end of the detachable arm. In yet another form of the invention the said pressure applying system comprises a U-shaped base member fixed outwardly of the said gear, a guide arm mounted slidably on the said base member to slide radially with respect to the said gear, a detachable actuator between the said guide arm and the said base member, a lock-piece having gear teeth selectively interlockable with said gear and slidably movable along a guide shaft on the said guide arm, and a pressure actuator for causing the said lock-piece to move along the said guide shaft. In compression molding apparatus according to the invention the screw shaft is rotated by the driving device in order to compress, for example, a composite material for making a firebrick. Then at the final stage, when compression molding is advanced, the pressure applying system is capable of engaging and disengaging the gear to achieve the degree of pressurization necessary for the completion of the compression molding. Some embodiments of the invention will now be described by way of example and with reference to the accompanying drawings, in which:- Fig. 1 is a side sectional view showing a first embodiment of the present invention; Fig. 2 is a plan view, from direction X in Fig. 1; Fig. 3 is a cross-sectional view on line Y-Y in Fig. 2; Fig. 4 is a plan view of a pressure applying system shown in Fig. 1; Fig. 5 is a plan view showing an OFF state of gear teeth shown in Fig. 4; Fig. 6 is a view from direction P in Fig. 4; Fig. 7 is a plan view of a pressure applying system of another embodiment of the invention; Fig. 8 is a view from direction Z in Fig. 7; Fig. 9 is a plan view of a pressure applying system of yet another embodiment of the invention; Fig. 10 is a plan view of a pressure applying system of a further embodiment of the invention; and Fig. 11 is a side sectional view of a conventional compression molding apparatus using a hydraulic press. In the drawings, the same reference numerals are used to designate components or parts similar to those already described with reference to Fig. 11. Referring first to Figs. 1 to 3, a screw shaft 5 is rotatably mounted in the upper side of a press frame 2 of a compression molding apparatus 1. A pressurization block 4, engaged with the screw shaft 5, is mounted to move slidingly in the axial direction while being engaged with the press frame 2 in a non-rotating manner. A gear 7 is fixed to the upper end of the screw shaft 5. The gear 7 is driven through a pair of pinions 11 mounted symmetrically with respect to the shaft, by driving means such as a pair of hydraulic motors 12. The two hydraulic motors 12 are each connected to a hydraulic pump (not shown) and are able to rotate at high speed in both directions. The driving means may employ a geared motor capable of switching the direction of rotation. The gear 7 is provided with a pressure applying system generally indicated by reference numeral 6. As shown in Figs. 4 to 6, the pressure applying system 6 comprises a torque arm 8, a mechanical clutch in the form of a pair of lock-pieces 22 for causing the torque arm 8 and the gear 7 to mutually engage and disengage, and a pair of pressure actuators 10 rotatably connected to the lock-pieces 22 by pins 24, the actuators facing each other in parallel at the outer ends of the torque arm 8. The central portion of the torque arm 8 is rotatably mounted on the upper end of the screw shaft 5, above the gear 7. The inner sides of the lock-pieces 22 are rotatably connected to the respective outer ends of the torque arm 8 by pins 23, and the outer sides of the lock-pieces are rotatably connected to the respective pressure actuators 10 by the pins 24. The lock-pieces 22 are formed with gear teeth 22a for selective interlocking with the gear 7 on each side thereof. Each of the pressure actuators 10 is connected through a hydraulic pipe (not shown) to a source of hydraulic pressure. Furthermore, at the other ends of the actuators 10, a pair of blocks 9 are rotatably fitted for receiving reaction force. Reference 8a indicates a stopper for the lock-piece 22 when it is drawn back to disengage from the gear 7, and reference 22b indicates a stopper for the lock-piece when engaged. A method of molding a firebrick will now be described as an example. A composite material for making a firebrick A is introduced into the space defined by pedestal J and metal mold I. The screw shaft 5 is then rotated at high speed in both directions in turn by the hydraulic motors 12, so as to move plunger 3 up and down in the vertical direction to cause the material A to be repeatedly pressurized by the pressurization block 4. When the composite material A has been compressed to a specified height, the pressure actuators 10 are extended so as to cause the lock-pieces 22, which up to now were in the positions shown in Fig. 5, to rotate and engage their gear teeth 22a with the gear 7, whereby the torque arm 8 and the gear 7 are interconnected, as in Fig. 4. The pressure actuators 10 are then further extended to cause the screw shaft 5 to be rotated by means of the gear 7, and thus move downwardly, at low speed, whereby the composite material A undergoes a final pressurization which is controlled as a defined pressurizing force or compression amount. Upon thus completing the molding, reverse operation causes the gear teeth 22a and the gear 7 to be mutually disengaged so as to disconnect the torque arm 8 from the gear 7. The operation is finally completed when the plunger 3 is lifted by rotating the hydraulic motors 12 in the reverse direction. When final pressurization is carried out by repeated pressurization, by extending the pressure actuators 10, so-called "bumping down molding" takes place by virtue of the vibrating movement of the torque arm 8 at a very small stroke. Figs. 7 and 8 show another embodiment of the invention. In the pressure applying system 30 of this embodiment, a torque arm 31 comprising a pair of fan shaped wings is rotatably mounted on the upper end of the screw shaft 5, above the gear 7. The torque arm 31 is formed with a quadrilateral windows 31a at each of its ends, in each of which windows is provided a mechanical clutch in the form of a lock-piece 32, slidably movable in the radial direction. On the inner side of each lock-piece 32, gear teeth 32a are formed to selectively interlock with the gear 7, and between the lock-piece 32 and the outer boundary of the quadrilateral window 31a, a pair of parallel detachable actuators 35 are provided. Furthermore, at the outer sides of the torque arm 31, a pair of pressure actuators 33 are rotatably mounted by way of arm pins 34, so as to face towards each other in parallel. In this embodiment, after pressurization by operation of the hydraulic motors 12 is completed, the detachable actuators 35 are operated to urge the lock-pieces 32 inwardly, whereby the gear teeth 32a are interlocked with the gear 7, following which the pressure actuator 33 is operated to add rotating force to the gear 7. Fig. 9 shows another embodiment of the invention. In the pressure applying system 40 of this embodiment, a base member 48 is provided in the press frame 2, outwardly of the gear 7 in the radial direction, to which an end of a detachable arm 41 is rotatably connected by a pin 43. A plate 47 is provided at the other end of the detachable arm 41, from which a pair of parallel guide rods 46 extend at right angles to the plate 47. A lock-piece 42 is slidably mounted on the guide rods 46. The lock-piece 42 is formed with gear teeth 42a for selective interlocking with the gear 7, and a pressure actuator 44 extends between the lock-piece 42 and a pin 43. Beyond the end of the detachable arm 41, a detachable actuator 45 is coupled to the arm at right angles thereto. In this embodiment, after the pressurization caused by operation of the hydraulic motor 12 is completed, the detachable actuator 45 is operated to interlock the gear teeth 42a and the gear 7 by pushing the lock-piece 42 and the detachable arm 41 towards the gear. Then, the pressure actuator 44 is operated to add rotational force to the gear 7, whereby the final pressurization takes place. Fig. 10 shows a further embodiment of the invention. In a pressure system 50, a U-shaped base member 58 is provided in the press frame 2, radially outwardly of the gear 7, and a detachable arm 51 is slidably mounted in the base member 58 to be movable radially of the gear 7. A pair of parallel guide rods 56 extend lengthwise of the arm 51 and slidably mount a lock-piece 52. The lock-piece 52 is formed with gear teeth 52a for selective interlocking with the gear 7, and a pressure actuator 54 is mounted between the end of the lock-piece 52 and the detachable arm 51. A detachable actuator 55 extends at right angles to the detachable arm 51. In this embodiment, after completion of the pressurization caused by operation of the hydraulic motor 12, the detachable actuator 55 is operated to interlock the gear teeth 52a and the gear 7, by pushing the lock-piece 52 and the detachable arm 51 towards the gear 7. Next, the pressure actuator 54 is operated to add rotational force to the gear 7, whereby the final pressurization takes place. In the above described arrangements, the pressure-mounting systems 6,30,40, and 50 are symmetrically provided in a horizontal direction, but alternatively only one arm need be provided. In operation of the above described arrangements, the following advantageous effects are produced: (1) In the last stage of the pressurization, a very high pressurizing force can be instantaneously applied. (2) The apparatus can be provided as a simple, lightweight structure at low cost. (3) Hydraulic pressure is input to the gear as torque instead of working as a direct pressurizing force, resulting in less wasted pressure and thus less wasted energy than in the prior art.

Claims: Compression molding apparatus comprising a screw press in which pressurization is carried out by moving a pressurization block (4) by means of a screw shaft (5), characterised by a gear (7) fixed to the screw shaft, primary means (12) for driving said gear including a pinion (11) engaging the same, and secondary means for driving said gear comprising a pressure applying system (6;30;40;50) engageable with and disengageable from said gear. Apparatus according to claim 1, wherein the said pressure applying system (6;30) comprises a torque arm (8;31) rotatably mounted on the said screw shaft (5), a mechanical clutch (22;32) for causing the torque arm and said gear (7) to be engaged and disengaged, and a pressure actuator (10;33) coupled with the said mechanical clutch. Apparatus according to claim 1, wherein the said pressure applying system (30) comprises a torque arm (31) rotatably mounted on the said screw shaft (5) and formed with a window (31a) at the outer end thereof, a lock-piece (32) mounted in the said window to slide in the radial direction and having gear teeth (32a) selectively interlockable with the said gear (7), a detachable actuator (35) for moving the said lock-piece towards and away from the said gear, and a pressure actuator (33) connected to the end of the torque arm for rotating the same. Apparatus according to claim 1, wherein the said pressure applying system (40) comprises a base member (48) fixed outwardly of the said gear (7), a detachable arm (41) rotatably connected to the said base member at one end, a lock-piece (42) having gear teeth (42a) selectively interlockable with the said gear and slidably mounted on a guide shaft (46) on the said detachable arm, a pressure actuator for moving the lock-piece towards and away from the said gear, and a detachable actuator (45) connected to the end of the other end of the detachable arm. Apparatus according to claim 1, wherein the said pressure applying system (50) comprises a U-shaped base member (58) fixed outwardly of the said gear (7), a guide arm (51) mounted slidably on the said base member to slide radially with respect to the said gear, a detachable actuator (55) between the said guide arm and the said base member, a lock-piece (52) having gear teeth (52a) selectively interlockable with said gear and slidably movable along a guide shaft (56) on the said guide arm, and a pressure actuator (54) for causing the said lock-piece to move along the said guide shaft.

Inventors: HAGUCHI HIROSHI, HAGUCHI, HIROSHI
Applicants: MITSUISHI FUKAI IRON WORKS, KABUSHIKI KAISHA MITSUISHI FUKAI TEKKOSHO
Application year: 1996
Main classification: B30B1
IPC codes: B30B11, B28B3, B30B9, B30B1