MOTOR-DRIVEN MOLD CLAMPING MECHANISM FOR INJECTION MOLDING MACHINES

Abstract: Motor-driven mould clamping mechanism generating a large clamping force when a motor of a small output is used, has ball nuts engaged with threads which are cut in the opposite directions in ball screws rotated by motors, and movable wedges connecting together by links. According to the rotation of the motors, the links contract or expand to move the wedges forward or backward with a large force. When the wedges are moved forward, they press and engage fixed wedges formed on a mould base of a mould, so that the mould is set firmly on a fixed board or a movable board.

Description: The present invention relates to a die clamp mechanism for removably mounting dies on a stationary board and a movable board of an injection-molding machine. In an injection-molding machine, dies are mounted on a stationary board and a movable board by the so-called "direct fastening" or "click fastening." In the former case, each die is fastened to its corresponding board, stationary or movable, by screwing mounting bolts into tapped holes which are formed in the stationary or movable board so as to be in alignment with mounting holes of the die. In the latter case, on the other hand, clamp plates, which are attached individually to the stationary and movable boards for movement, are driven toward the dies by manual operation or by means of a hydraulic mechanism, and a mold base of each die and clicks of its corresponding clamp plate are pressed against one another for engagement, thereby fastening the dies to the stationary and movable boards. In the case of a motor-operated die injection-molding machine in which a mold clamp mechanism, injection mechanism, etc. are driven by means of motors, however, a die clamp mechanism should preferably be driven also by means of motors. Thus, when hydraulically driving a die clamp mechanism of a click-fastening type in a conventional manner, a hydraulic mechanism must be provided only for die mounting, resulting in poor economy. US-A-4,500,275 discloses a motor-operated die clamp mechanism according to the precharacterising part of the attached claim 1, employing a screw to apply clamping force to a mold of an injection molding machine. DE-A- 3 610 060 shows a hydraulically operated clamp mechanism where a "toggle-knee" or cams are used to generate the clamping force. The object of the present invention is to provide a motor-operated die clamp mechanism of an injection-molding machine capable of producing a great clamping force even with use of motors having low output torque, without using a hydraulic mechanism to mount dies on a stationary board and a movable board of an injection-molding machine. According to the present invention, there is provided a motor-operated die clamp mechanism of an injection-molding machine, comprising a plurality of pressure means disposed individually on a stationary board and a movable board of the injection-molding machine so as to be movable towards and away from dies on the respective boards and to press the dies onto the associated boards, a rotary motor for actuating at least one of said pressure means, and transmission means for transmitting the rotary force of the motor to the or each associated pressure means, characterised in that there is a plurality of said rotary motors, said pressure means comprise movable wedges, and each said transmission means comprises a pivotable lever means which is actuated by rotation of a shaft driven by one of the rotary motors and which transforms and amplifies the force applied by the associated motor and transmits it to the associated movable wedge in a plane parallel to the associated stationary or movable board. According to the present invention, as described above, the die clamp mechanism is driven by means of motors, so that a hydraulic mechanism need not be used for the clamp mechanism. Thus, there may be provided a clamp mechanism which is particularly adapted for a motor-operated injection-molding machine and is low-priced. Since the rotary force of the motors is amplified by means of the transmission means, moreover, small-output motors can be used, thus permitting a low-priced clamp mechanism to be obtained. Brief Description of the Drawings Fig. 1 is a front view showing a motor-operated die clamp mechanism according to a first embodiment of the present invention; Fig. 2 is a schematic view taken along line II-II of Fig. 1; and Fig. 3 is a front view of a clamp mechanism according to a second embodiment of the present invention, provided on the stationary-board side of an injection-molding machine. In Figs. 1 and 2, a motor-operated die clamp mechanism according to a first embodiment of the present invention is preferably provided in a motor-operated injection-molding machine (not shown in detail) of a type which drives various operating mechanisms, such as a mold clamp mechanism, injection mechanism, etc., by means of motors. In the injection-molding machine, a movable board 2 is driven so as to approach and leave a stationary board 1 by means of the mold clamp mechanism, and dies 3 can be removably mounted on the stationary and movable boards 1 and 2. Fixed wedges 5 are fixed individually to the respective opposite end portions of the upper and lower edges of a mold base 4 of each die 3. Thus, in the present embodiment, four fixed wedges 5 are provided for each die 3. Each fixed wedge 5 is formed so that its thickness is reduced toward the outer edge of the mold base 4, that is, an end face 5a of each fixed wedge 5 remote from the mold-base side forms a slanting surface. The die clamp mechanism with the aforementioned construction for mounting the dies 3 on the stationary and movable boards is composed of first and second clamp mechanism sections which correspond to the elements 1 and 2, respectively. Each of these clamp mechanism sections includes clamp portions, four in number or as many as the fixed wedges 5 attached to its corresponding die 3. Each clamp portion includes a movable wedge 6 which, opposed to its corresponding fixed wedge 5, constitutes pressure means in conjunction with the wedge 5. The wedge 6 is reduced in thickness toward its distal end, and its end face 6a on the mold-base side forms a slanting surface. Moreover, the wedge 6 is disposed to be rectilinearly movable toward and away from the die 3, within a hole 7a in its corresponding wedge retainer 7, which is disposed in alignment with the fixed wedge 5 and fixed to the stationary or movable board 1 or 2, as a transmission mechanism, which, composed of elements 8 to 13 and P1 to P4, serves to amplify the rotatory force of a motor (mentioned later), operates. More specifically, the movable wedge 6 is rockably supported on one end of a coupling member 8 of the transmission mechanism by means of a pin P1. Links 9 and 10 are rockably supported, at one end thereof, on the other end of the member 8 by means of the pin P2. The other ends of the links 9 and 10 are rockably coupled to ball nuts 11 and 12 by means of pins P3 and P4, respectively. The ball nuts 11 and 12 are threadedly engaged with a small-diameter screw portion 13a and a large-diameter screw portion 13b, respectively, of a ball screw 13 which, in conjunction with the nuts, constitutes means for converting the motor rotation into a rectilinear motion of the movable wedge. Both the screw portions 13a and 13b are formed with threads such that their threading directions are opposite to each other. As described above, the clamp portions with the aforementioned construction are arranged individually opposite to the four corners of the mold base 4 of each of the dies 3 on the stationary- and movable-board sides. The adjacent ball screws 13 at the upper or lower edge of the stationary or movable board 1 or 2 are formed integrally with each other through the medium of a junction 14, thus forming a screw body 13'. More specifically, at the junction 14 of the screw body 13', a projection formed on one of the respective opposite faces of the ball screws 13 which forms the screw body 13' is fitted in a recess formed on the other (not shown). Further, both ends of the screw body 13' are rotatably supported on its corresponding board, out of the stationary and movable boards 1 and 2, by means of bearings 19, and also, one end of the screw body 13' is operatively connected to a motor 15 with brake gear by means of a coupling 17 and a flexible joint 18. Thus, two motors 15 are provided for each of the stationary and movable boards 1 and 2. In Fig. 2, numeral 20 designates a tie rod. The movable board 2 is movable along the tie rod 20. Additionally speaking, Fig. 2 shows a state in which the clamp portions on the left and right half portions are in different operating positions, to meet the convenience of the following description (same for the case of Fig. 3, mentioned later). Actually, however, the clamp mechanism is constructed so that the two clamp portions associated with one screw body 13' always take the same operating position. The following is a description of the operation of the motor-operated die clamp mechanism with the aforementioned construction. Let it be supposed that all the clamp portions of the clamp mechanism take an operating position (shown in the left half portion of Fig. 2) such that the movable wedges 6 are retreated. First, the dies 3 on the stationary- and movable-board sides, in contact with each other, are arranged between the stationary and movable boards 1 and 2 which are spaced at a predetermined distance from each other. Then, all the motors 15 are driven in synchronism with each other, in a predetermined rotating direction. Since the small-and large-diameter screw portions 13a and 13b of each ball screw 13 are threaded reversely to each other, the ball nuts 11 and 12, threadedly engaged, respectively, with the screw portions 13a and 13b, which rotate accompanying the motor rotation, move so as to approach each other along the screw portions. As a result, the links 9 and 10 are gradually closed in a contracted manner, so that each movable wedge 6, which is coupled to both the links by means of the coupling member 8, slides inside the hole in the wedge retainer 7, thus advancing toward the die 3. In doing this, the movable wedge 6 is driven by means of a great force of e.g. about 10 to 20 tons, which is obtained by amplifying the motor's rotatory force by means of the transmission mechanism, which is composed of the links 9 and 10, ball nuts 11 and 12, and ball screws 13. As the movable wedge 6 advances, the slanting surface 6a of the wedge 6 slides on the slanting surface 5a of the fixed wedge 5, thereby gradually pressing the slanting surface 5a. Thereafter, when the movable wedge 6 reaches its forefront position shown in the right half portions of Figs. 1 and 2, it engages the fixed wedge 5 with a great force of pressure. Thus, the dies 3 are securely fixedly mounted on the stationary and movable boards 1 and 2, individually, by the wedge effect. Subsequently, brake gears (not shown) attached to the motors 15 are worked to lock the output shafts of the motors and the ball screws 13 so that these elements cannot rotate, thereby maintaining this mounting state. In removing the dies 3, on the other hand, the clamp mechanism is operated in the manner reverse to the steps of procedure for the die mounting. More specifically, after the brake gears are disengaged, all the motors 15 are reversed. As the motors reversely rotate in this manner, the ball nuts 11 and 12 move away from one another along the screw portions 13, thereby spreading the links 9 and 10. Thereupon, the movable wedges 6 move away from the dies to be disengaged from the fixed wedges 5, as shown in the left half portion of Fig. 2, so that the dies 3 are allowed to be removed from the stationary and movable boards 1 and 2. Fig. 3 shows a motor-operated die clamp mechanism according to a second embodiment of the present invention, the mechanism being mounting on a stationary board 1. Also, a clamp mechanism (not shown) with the same construction is mounted on a movable board 2. The clamp mechanism of the present invention differs from that of the first embodiment in the arrangement of the transmission mechanism. In Fig. 3, like reference numerals are used to designate those elements which are common to both these embodiments, and a description of those elements is partially omitted. In Fig. 3, a pin 8a, which is attached to a shaft 8b of each coupling member 8, is guided by means of a guide member 24 to be engaged with a slot 21b which is formed in the outer half portion of a link 21 so as to extend along the axis of the link. Further, the link 21 is swingably supported, at an intermediate portion thereof, by a shaft 25 which is supported on its corresponding board, out of the stationary and movable boards 1 and 2. A pin 26a, which is attached to its corresponding end portion of a plate member 26 fitted with a ball nut 22 for integral movement, is engaged with a slot 21a which is formed in the inner half portion of the link 21 so as to extend axially. The link 21 is designed so that the distance between the shaft 25 and the slot 21b is set to a value smaller than the distance between the shaft 25 and the slot 21a. A ball screw 23, which is threadedly engaged with a ball nut 22, is rotatably supported on its corresponding board, out of the stationary and movable boards 1 and 2, by means of bearings (not shown), and is also connected to the output shaft of a motor 15 by means of a coupling 17 and a joint 18. The operation of the clamp mechanism with the aforementioned construction will be described. Prior to the mold mounting, the ball nuts 22 are brought to positions close to dies 3, as shown in the left half portion of Fig. 3, thereby causing the movable wedges 6 to be disengaged from the fixed wedges 5. Subsequently, the dies 3 are disposed between the stationary and movable boards 1 and 2, and all the motors 15 are then driven in a predetermined rotating direction, so that the ball nuts 22, which are threadedly engaged with the ball screws 23 rotating together with the motors, are biased individually away from the dies 3. As a result, the two links 21 associated with each ball nut 22 rock in directions opposite to each other around their corresponding shafts 25. Thereupon, the movable wedges 5, which are coupled to the individual links 21 by means of the coupling members 8, advance toward the die 3, thus taking their forefront position shown in the right half portion of Fig. 3. In this position, the movable wedges 6 are engagedly pressed against the fixed wedges 5 with a great force, so that the die 3 is mounted on its corresponding board, out of the stationary and movable boards 1 and 2. Then, brake gears (not shown) are worked to maintain the die mounting state. A description of the operation for the die removal is omitted. The clamp mechanism according to the present invention is not limited to the embodiments described above. Although the small- and large-diameter screw portions 13a and 13b are provided in the first embodiment, for example, the screw portions may have the same diameter. Although the adjacent ball screws 13 are formed integrally, moreover, they may be formed independently and driven separately by means of motors for their exclusive use. The second embodiment may be modified in like manner. In the embodiments described above, furthermore, the dies are clamped at their upper and lower edges. Alternatively, however, they may be clamped at both side edges.

Claims: A motor-operated die clamp mechanism of an injection-molding machine, comprising a plurality of pressure means (6) disposed individually on a stationary board (1) and a movable board (2) of the injection-molding machine so as to be movable towards and away from dies (3) on the respective boards (1,2) and to press the dies (3) onto the associated boards (1,2), a rotary motor (15) for actuating at least one of said pressure means (6), and transmission means (8 to 13, 8 and 21 to 26) for transmitting the rotary force of the motor (15) to the or each associated pressure means (6), characterised in that there is a plurality of said rotary motors (15), said pressure means (6) comprise movable wedges, and each said transmission means comprises a pivotable lever means (9,10,21) which is actuated by rotation of a shaft (13,23) driven by one of the rotary motors (15) and which transforms and amplifies the force applied by the associated motor (15) and transmits it to the associated movable wedge (6) in a plane parallel to the associated stationary or movable board (1,2). A motor-operated die clamp mechanism of an injection-molding machine according to claim 1, wherein each said die (3) has a mold base (4) formed with a plurality of fixed wedges (5) on the peripheral edge portion thereof, each said pressure means (6) comprises a movable wedge which is arranged for rectilinear motion so as to be movable toward and away from one of said fixed wedges (5) and has a slanting surface (6a) adapted to be in sliding contact with a slanting surface (5a) formed on the fixed wedge (5) corresponding thereto, and each said transmission means (8 to 13) includes conversion means, comprising a screw (13,23), for converting the rotary force of the associated motor (15) into a working force for rectilinearly moving the associated movable wedge (6). A motor-operated die clamp mechanism of an injection-molding machine according to claim 1 or 2, wherein each said transmission means (8 to 13) includes: a ball screw (13) having first and second screw portions (13a,13b) threaded reversely to each other and integrally movable, said ball screw (13) being operatively coupled to an associated rotary motor (15); first and second ball nuts (11,12) threadedly engaged with respective ones of said first and second screw portions (13a,13b); and link means (9,10) for coupling said first and second ball nuts (11,12) to the associated movable wedge (6), said link means (9,10) being adapted to spread or contract in accordance with the rotating direction of said associated rotary motor (15), thereby to cause said movable wedge (6) to make a rectilinear motion, whereby the rotary force of the motors (15) is amplified and transmitted to the movable wedges (6). A motor-operated die clamp mechanism of an injection-molding machine according to claim 1 or 2, wherein each said transmission means (8 and 21 to 26) includes: a ball screw (23) operatively coupled to an associated rotary motor (15); a ball nut (22) threadedly engaged with said ball screw (23); and a link (21) pivotably supported at an intermediate portion thereof and pivotably coupled, at its ends, to said ball nut (22) and to a movable wedge (6), respectively, whereby the rotary force of the motors (15) is amplified and transmitted to the movable wedges (6). A motor-operated die clamp mechanism of an injection molding machine according to claim 4, wherein each said link (21) is pivotably supported such that the distance between said intermediate portion and its ball-nut end is greater than the distance between said intermediate portion and its movable wedge end. A motor-operated die clamp mechanism of an injection-molding machine according to any one of the preceding claims, wherein the injection-molding machine has its operating mechanism sections driven individually by means of motors.

Inventors: YAMAZAKI, SEIJI FANUC UTSUGIRYO
Applicants: FANUC LTD.
Application year: 1988
Main classification: B29C45
IPC codes: B29C45