INJECTION MOULDING MACHINE

Abstract: An injection moulding machine wherein the state of nozzle contact can be easily observed from the outside of a mold clamping unit (10). Monitoring holes (16a, 16b) are provided in a Fixed platen (1) of the mold clamping unit (10). The monitoring holes (16a, 16b) are caused to penetrate from at least either of the front and back sides of the mold clamping unit (10) toward a locating hole (12) for locating a sprue bush (31) of a mold. It is possible to provide shutters (22a, 22b) on the monitoring holes (16a, 16b) that are adapted to interlock with a purge shield (20) for opening and/or closing. Furthermore, it is possible to construct the injection moldig machine such that the monitoring holes (16a, 16b) can be used for unobstructed observation via windows (34a, 34b) provided in a purge shield (30).

Description: The present invention relates to an injection molding apparatus, more particularly to an injection molding apparatus equipped with clamping and injection units disposed opposite to each other. In an injection molding apparatus equipped with a clamping and an injection unit disposed confronting each other, injection is performed by causing the tip of the nozzle of the injection unit to abut against the dies fixed to the clamping unit. When the dies have been changed, the cylinder assembly of the injection unit has been changed, or when the injection unit has been turned for change of parts, it is necessary to check, at the time of the nozzle touching operation, whether the tip of the nozzle of the injection unit accurately abuts against the sprue bush of the dies while operating the injection unit manually or at a low speed. For this purpose, the abutment between the sprue bush and the injection nozzle tip, i.e. the condition of nozzle touch, is conventionally monitored through a clearance formed in the vicinity of the purge shield by an operator looking into the front side of the stationary platen (a surface on the side of the injection unit) from the front side of the clamping unit. However, a point where the sprue bush and the injection nozzle tip abut each other tends to locate in a dark place far inward from the front side of the stationary platen. Thus, it has been difficult for the operator to accurately monitor the condition of abutment. This difficulty increases as the size of the injection molding apparatus increases, since the size of the stationary platen also increases accordingly. Thus, there has been a possibility of having the resin leaked outside due to improper nozzle touch. The present invention provides an injection molding apparatus rendering it easier for an operator to monitor an abutting condition between the sprue bush and the injection nozzle tip. According to the present invention, an injection molding apparatus comprises a clamping unit having a movable platen and a stationary platen. The stationary platen has a locating hole into which the sprue of the dies is to be located, and at least one monitoring hole extending from the side thereof toward the locating hole, so that the locating hole can be monitored from the side of the clamping unit through this monitoring hole. The direction of the monitoring hole is determined so that an operator is allowed to monitor the locating hole from at least either of the front and rear sides of the clamping unit. The monitoring holes may be provided with shutters, the shutters being interlocked with a purge shield so that the monitor hole is opened together with the purge shield when the purge shield is opened. This shutter prevents the gas or resin from blowing off directly toward an operator during the purge operation. Furthermore, a window may be provided in a purge shield covering the front side of the stationary platen. The window of the purge shield and the monitoring holes are designed to cooperatively allow the operator to monitor the locating hole even during the purge operation of the clamping unit. BRIEF DESCRIPTION OF DRAWINGS Fig. 1 is a partly sectional side view showing an injection molding apparatus in accordance with a first embodiment of the present invention; Fig. 2 is a front view showing a stationary platen of the injection molding apparatus shown in Fig. 1; Fig. 3 is a horizontal sectional view taken along a line III-III of Fig. 2; Fig. 4 is a side view showing the stationary platen shown in Fig. 2; Fig. 5 is a transversal sectional view showing an essential part of an injection molding apparatus in accordance with a second embodiment of the present invention; Fig. 6 is a transversal sectional view showing an essential part of an injection molding apparatus in accordance with a third embodiment of the present invention; and Fig. 7 is a perspective view showing a purge shield shown in the third embodiment of Fig. 6. An injection molding apparatus in accordance with the first embodiment of the present invention will be explained with reference to Figs. 1-4. In Fig. 1, a clamping unit 70 and an injection unit 80 are disposed on a base 60 confronting each other. The clamping unit 70 includes a movable platen 40, a stationary platen 10 and dies 50 disposed therebetween. An injection nozzle 81 of the injection unit 80 has a tip to be brought into contact with a sprue 51 of the dies 50 when performing injection molding. As shown in Figs. 2 and 3, the stationary platen 10 has a locating hole 12 opening at a central portion thereof on the side close to the movable platen 40 (i.e. a rear side). The main body 14 of the stationary platen 10 includes a guide wall 15, which protrudes on the side of the injection unit 80 (in the forward direction), and the guide bore 13 is formed in the guide wall 15. The guide bore is gradually tapered backward until it comes to communicate with the locating hole 12. The guide wall 15 is provided with two monitoring holes 16a and 16b, the former being a through hole extending from the front side with respect to an operator's position and the latter being a through hole extending from the side opposing the above front side. The monitoring hole 16a extends straight from the outside of the guide wall 15 toward the locating hole 12 until it reaches the guide bore 13. The monitoring hole 16a has a diameter large enough to allow an operator to look into the locating hole 12 entirely through this monitoring hole 16a from the front side of the clamping unit 70. The monitoring hole 16b provided at the rear side is substantially identical in construction with the monitoring hole 16a provided at the front side except that they are symmetrically disposed. Several lightening holes 17 are provided around the guide wall 15 to reduce the weight of the stationary platen 1. A reference numeral 18 represents a hole for installing a tie bar. Upon setting of the dies 50 into the stationary platen 10, the sprue bush 51 of the dies 50 is positioned inside the locating hole 12. Thus, the monitoring holes 16a and 16b enable an operator to monitor the positional relationship between the tip of the injection nozzle 81 of the injection unit 80 and the sprue bush 51, i.e. the nozzle touch condition during the nozzle touch operation. In this case, the operator can monitor the nozzle touch condition from either the front side or the rear side of the clamping unit 70 through the monitoring hole 16a or 16b. Furthermore, provision of a plurality of monitoring holes will make it easier to monitor the abutting condition between the sprue bush 51 and the injection nozzle 81, because light is introduced inside through a monitoring hole not being used by an operator. By the way, the condition of abutting between the sprue bush 51 and the injection nozzle 81 can be adjusted by using a jack bolt or a lateral position adjusting bolt (not shown) provided in the injection unit 80 by changing the mutual position between the sprue bush 51 and the injection nozzle 81. Next, a second embodiment of the present invention will be explained with reference to Fig. 5. The stationary platen 10 is provided with a platen cover 19, on which there are provided two door plates 21a and 21b of a purge shield 20 and two shutters 22a and 22b for the monitoring holes 16a and 16b. The door plates 21a and 21b are supported on the front side of the platen cover 19 at their base ends so as to be rotatable about hinges 23, 23 provided thereon; thus, the guide bore 13 can be covered (closed) on both the front and rear sides. Although not shown in the drawing, there is provided a top board extending on the door plates 21a and 21b. Overall configuration of the purge shield 20 is a rectangular shape with an open bottom when seen from the front. The shutters 22a and 22b are provided on the platen cover 19 in such a manner that the platen cover 19 is partly replaced by the shutters 22a and 22b at the portions where phantom lines extending from the monitoring holes 16a and 16b intersect with the platen cover 19, respectively. Each of the shutters 22a and 22b is swingably supported by a hinge 24. The door plates 21a and 21b of the purge shield 20 are connected with the shutters 22a and 22b by means of thin links 25, 25, respectively. When the door plates 21 take a closed position in which each door plate is normal to the front side of the platen cover 19, the shutters 22 respectively become flush with the surface of the front plate of the platen cover 19. That is, the monitoring holes 16a and 16b are closed. In general, the purge shield 20 is equipped with limit switches (not shown) for detecting open conditions of the door plates 21a and 21b, respectively. These limit switches function to prevent the injection unit from performing purge operation. With above arrangement, only when the door plates 21a and 21b of the purge shield are opened, i.e. only when the limit switches are activated in response to the opening of the door plates 21a and 21b to disable the injection unit from performing the purge operation, the shutters 22a and 22b are opened to allow an operator to look into the monitoring holes 16a and 16b. Thus, the operator is surely protected from being directly exposed to purged resin or gas while monitoring the abutting condition between the sprue bush 51 and the injection nozzle 81. Furthermore, during the purge operation, not only the door plates 21a and 21b of the purge shield 20 but the shutters 22a and 22b are closed, so that neither the gas nor the resin will leak out of the purge shield 20 during the purge operation. Next, a third embodiment of the present invention will be explained with reference to Figs. 6 and 7. The stationary platen 10 is provided with a platen cover 19'. A purge shield 30 is attached to a front side of the platen cover 19'. The purge shield 30 consists of a main body 31 and a lid member 32, and its overall configuration is of a truncated pyramid whose top faces forward. As shown in Fig. 7, the purge shield 30 has a top board 33, although neither a rear board nor a bottom board is provided. The lid member 32 constitutes one of side surfaces of the above truncated pyramid and has a window 34a of a transparent synthetic resin board. The lid member 32 is attached to the front surface of the platen cover 19' by the hinges 35 so that the lid member is allowed to swingably turn frontward about the hinges. The main body 31 has a front plate 36 which includes an opening 37 to allow a front edge of the cylinder assembly 20 to enter. A side plate 38 has a window 34b similar to the window 34a. The main body 31 is attached to the front side of the platen cover 19' by hinges 39 so as to be swingable toward the rear side about the hinges. The purge shield 30 is formed to be large enough to allow phantom lines extending from the monitoring holes 16a and 16b to intersect with the windows 34a and 34b. (Refer to Fig. 6) The above arrangement enables an operator to monitor the abutting condition between the sprue bush 51 and the injection nozzle 81 from the windows 34a and 34b through the monitoring holes 16a and 16b even if the injection unit 20 is in a purge operation. The present invention is not limited to the embodiments disclosed by the drawings. For example, the monitoring holes 16a and 16b may be provided only in the front side of the clamping unit 70. Furthermore, in the second embodiment, if the door plates 21a and 21b of the purge shield have sizes as large as covering the monitoring holes 16a and 16b when opened, the door plates 21a and 21b themselves may be made of transparent material so that an operator become able to look into the monitoring holes 16a, 16b through the transparent door plates 21a, 21b. Furthermore, in the same embodiment, the links 25, 25 may be omitted, and the shutters 22a and 22b of the purge shield 20 can be made of transparent material so as to allow an operator to look into the monitoring holes through these transparent windows. The present invention enables an operator to perform the nozzle touch operation while monitoring the abutting condition between the sprue bush of the dies and the nozzle tip of the injection unit. Thus, the nozzle touch operation can be performed accurately. Even if the thickness of the stationary platen increases, the monitoring of the nozzle touch operation can be done easily. Furthermore, the nozzle touch operation can be monitored without the danger of being exposed to the purged gas and resin during the purge operation and the gas and resin are prevented to leak outside through the monitoring holes during the purge operation.

Claims: An injection molding apparatus comprising: a clamping unit (70) having a movable platen (40) and a stationary platen (10) for holding dies (50) therebetween; said stationary platen (10) having a locating hole (12) into which a sprue (51) of the dies (50) is to be located, and being characterised by at least one monitoring hole (16a,16b) extending from at least one side of the clamping unit (70) toward said locating hole (12), whereby the locating hole (12) of said stationary platen (10) can be monitored from said at least one side of the clamping unit (70) through said at least one monitoring hole (16a,16b). An injection molding apparatus in accordance with claim 1, wherein a said monitoring hole (16a) extends from one side of the stationary platen (10) confronting an operator, and another said monitoring hole (16b) extends from the opposite side of the stationary platen (10), both toward said locating hole (12). An injection molding apparatus in accordance with claim 1 or 2, wherein said clamping unit (70) further comprises a platen cover (19) surrounding said stationary platen (10), and a purge shield (20) which can be selectively opened and closed, said platen cover (19) has at least one shutter (22a,22b) facing to said at least one monitoring hole (16a,16b), and said at least one shutter (22a,22b) is opened and closed in response to open and close motions of said purge shield (20), whereby said locating hole (12) can be monitored through said at least one monitoring hole (16a,16b) when said at least one shutter (22a,22b) is opened. An injection molding apparatus in accordance with claim 1 or 2, wherein said clamping unit (70) further comprises a purge shield (30) disposed in front of said stationary platen (10) and provided with at least one window (34a,34b), whereby said locating hole (12) can be monitored through said at least one window (34a,34b) of the purge shield (30) and said at least one monitoring hole (16a,16b). An injection molding apparatus in accordance with claim 4, wherein said clamping unit (70) comprises a platen cover (19') surrounding said stationary platen (10), and said purge shield (30) is attached to said platen cover (19').

Inventors: ITO SUSUMU ROOM, NISHIMURA KOICHI, ITO, SUSUMU, NISHIMURA, KOICHI, ITO, SUSUMU, ROOM 7-204, FANUC MANSHONHARIMOMI, NISHIMURA, KOICHI, RM. 4-305,FANUC MANSHONHARIMOMI
Applicants: FANUC LTD, FANUC LTD.
Application year: 1993
Main classification: B29C45
IPC codes: B29C45, B29C33