FORM2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)

1. Title of the invention. - A CONTROLLER UNIT FOR PRECISELY ACHIEVING
THE CLOCKWISE AND ANTI-CLOCKWISE MOVEMENT OF THREADED CORE.
2. Applicant(s)
(a) NAME :
(b) NATIONALITY :
(c) ADDRESS :
LARSEN & TOUBRO LIMITED
An Indian Company.
L & T House, Ballard Estate, Mumbai 400 001 State of Maharashtra, India
3. PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed:


TECHNICAL FIELD OF THE INVENTION
The present invention relates to an injection molding apparatus for making components having internal and external threading and more particularly to a controller unit for actuating a limit switch which in turn sends a signal to a PLC wherein the PLC controls the clockwise and anticlockwise rotation of motor which in turn rotates screw means/unscrewing maechanism.
BACKGROUND AND THE PRIOR ART
One of the most common methods for shaping raw thermoplastic materials is a process called injection molding. Injection molding is accomplished by an apparatus which is frequently referred to as injection molding apparatus.
As a result of the injection molding process, there is some amount of shrinkage in the plastic which is often referred to as processing shrinkage. Owing to this processing shrinkage molded parts tend to be retained on mold cores. Various types of ejectors are used to release parts depending on the shape of the moulded part. Usually the mold core and thus ejector mechanisms are located at the moving platen of the injection moulding machine. For ejection of the component from core, there should be no portion of the steel remains in the undercut of the


component, which will obstruct the removal of the component. In other words all the undercuts in the line of draw should be released before ejection of the component. To release undercuts, slides and split cavities are generally needed.
If release of threads is not possible by means of slides, split cavities, collapsible cores, or if witness line is not acceptable, then unscrewing mechanism is employed. Unscrewing mechanism includes rotating as well as linear motion of either the threaded core or the component.
Prior unscrewing mechanism used method to control the clockwise and anticlockwise movement of the motor has been explained in figure 1.
It consists of a pinion, rack or worm gear, the rack of worm gear is connected to a rod leading to two actuator pullies. The pinion gear is connected directly or indirectly (through gear train and bearings) to the motor. The rotary motion of the pinion is converted to translating motion with the help of rack or the worm gear. This translational motion is further used to activate the plunger. The plunger will activate the electrical limit switch. This method is associated with a lot of disadvantages, namely, as follows:
a. Occupies more space;
b. Transmission system is more complicated;


c. Requires additional elements for location and
fixing;
d. More weight; and
e. More costly.
The present invention provides a controller unit which surmounts the aforesaid disadvantages by providing appropriate signals for limiting the direction of rotation of the hydro motor. In the present invention, the mould consists of an unscrewing mechanism to relieve the threaded under cut actuated by hydro motor and gear trains. The actuation of hydro motor for screwing and unscrewing is achieved by clockwise and anti-clockwise rotation of hydro motor which is transferred to the spindle where threaded core is mounted by means of gear trains. For actuating the hydro motor, clockwise and anti- clockwise, programming is done by PLC available on moulding machine. PLC circuit requires signals for initiating the clockwise and anti - clockwise rotation of motor. This is achieved by using limit switch to send signals at maximum engaged and retracted position of threaded core.
OBJECTS OF THE INVENTION
Thus one object of the present invention is to overcome the problems of the prior art.


Another object of the present invention is to control the clockwise and anticlockwise rotation of a actuating motor.
Yet another object of the present invention is to obtain an essentially ideally controlled unscrewing mechanism.
Yet another object of the present invention is to send signals to PLC by actuating limit switch at required positions thru very compact over mounted device.
SUMMARY OF THE INVENTION
According to one aspect of the present invention there is provided a controller unit for use in injection molding apparatus to precisely achieve clockwise and anticlockwise movement of threaded core said injection molding apparatus, said unit comprising:
a cam assembly comprising a cylindrical cover means securing lead screw therein being mechanically coupled to a motor on one end and a guiding means on the other end, said guiding means providing mechanical support to said lead screw,
wherein said cam assembly comprising cam dog and nut held together by alien screw means being disposed in a slot provided in said cam assembly so as to allow two degrees of freedom (up and down motion) to said cam dog means;
31 MAR 2009

said cam dog means being operatively connected to said
lead screw for actuating means;
a limit switch;
a PLC circuit; and
wherein rotary movement of said motor being transmitted to said cam dog means through said lead screw such that said rotary movement in co-operation with said slot means is converted into a linear motion of a cam dog means in a manner that said cam dog activates said limit switch which in turn sends signal to said PLC circuit for changing direction of rotation of said motor.
According to another aspect of the present invention there is provided a cam assembly comprising a cylindrical cover means securing lead screw therein being mechanically coupled to a motor on one end and a guiding means on the other end, said guiding means providing mechanical support to said lead screw,
wherein said cam assembly comprising cam dog means being disposed in a slot provided in said cam assembly so as to allow two degrees of freedom to said cam dog means adopted to actuate switching means by way of its to and fro linear movement.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 2 illustrates an undercut


Figure 3 illustrates the detailed sectional view of the mould assembly
Figure 4 illustrates the zoomed view of the mould assembly
Figure 5 illustrates another detailed sectional view of the mould assembly
Figure 6 illustrates the device assembly which comprises a cam dog (1); a cover cylinder (2); a bush (3); a lead screw (4); a nut (5) and alien screws (6).
Figure 7 illustrates the different views of the cam dog of the assembly
Figure 8 illustrates the different views of the cover cylinder
Figure 9 illustrates the top view and the side view of the bush
Figure 10 illustrates the lead screw of the assembly
Figure 11 illustrates the nut of the assembly


DETAILED DESCRIPTION OF THE INVENTION
Injection Moulding:
Injection moulding is one of the major processing techniques for converting thermoplastic materials into different shapes. In said process, the plastic raw material is heated until it melts and then forcing such melted plastic under pressure with the help of injection moulding machines into a cold mould where it cools and solidifies. Thereafter, the mould is opened and the product is ejected out.
Injection Mould:
Injection mould, mainly consist of two halves, namely, a fixed half and a moving half. The fixed half or the cavity side of the mould is secured with the stationary platen of the machine. The sprue for filling the cavity is in this half aligned with the nozzle of machine. The moving half or the core half of the mould is secured to the moving platen of the machine. Arrangement for ejection of the part is also provided in this half. The die cavity, which forms the part being moulded, is machined into both halves of the die block. In operation, both these halves are closed each other under machine tonnage and collectively they form the impression, which has the shape of the component. Then, melted plastic is injected through feed system arrangement provided on the


mould into the impression where it cools and solidifies. The die is designed so that the moulding remains in the ejector half when the mould opens taking advantage of the shrinkage property of the plastic or by other means. The moulding is then pushed out with ejector pins provided on the mould.
Stages in Injection moulding process:
1. Mould Closing
2. Injection of the material
3. Cooling of the component 4 . Mould opening

5. Removal of undercuts in the line of draw if any
6. Ejection of the component
Due to the shape of the component mould steel may come in the pockets of component which creates obstruction for ejection. This hidrance are often termed as undercuts.
Release of undercuts, calls for additional design features in the mould, such as opening of the mould in multiple daylights (stages) etc. Additional release surfaces can be provided by slides and split cavities. Moulds with slides, release external undercuts with the aid of angle pin, cams, and hydraulically or pneumatically actuated mechanisms. Internal undercuts can be released with the help of angle lifters, sprung cores, collapsible cores or internal slides. Threads, both external & internal can be released by

- Slides
Removable inserts (loose inserts)
Collapsible cores
Unscrewing cores / sleeves, etc.
The present invention is drawn towards such a system which controls the rotating movement of the motor thereby controlling unscrewing mechanism for removal of undercuts in the line of draw before ejection. The system essentially comprises an assembly; a limit switch, a PLC and a motor. The assembly subsequently is made up of six components. The components of the assembly have been discussed below.
Cam dog (1) : It has got two points A and B as shown in figure 7 for actuating limit switch, it is mounted on to a nut by means of an Allen screw (6). it is designed to slide smoothly over the slot provided on cylinder cover. Various working length of limit switch can be achieved by maintaining the distance between the point A and B.
Cover Cylinder (2) : As the name suggests, it covers and locates all the elements of the assembly. It has got a cylindrical structure as shown in figure 8. Entire unit is mounted on the mould by Allen screws.
Bush (3) : It is mounted on cylinder cover and provides support and guidance for the lead screw to rotate.


Lead Screw (4): It is the link that connects the motor to the modular device. One end of this is connected to the motor through pinion gear (mould element) and the other end is supported and guided on the bush. It has got some threaded portion for the nut to move up and down which in turn causes the movement of cam dog. The lead screw has been illustrated in figure 10.
Nut (5) : It has got an internal thread, which suits with lead screw. It is designed to move over the male threads provide on lead screw and has also got provision to mount cam dog on it.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The invention lies in the controller unit for precisely achieving the clockwise and anti clockwise movement of threaded core by actuating the limit switch.
In a preferred embodiment working of the system can be explained as follows. The lead screw that is connected to the rotating source (motor) has got threading of 1mm pitch {can vary depending on requirement) on it. It is supported and guided at the other end by guiding means which is a bush. There is one round nut provided on the lead screw. On the nut one cam dog with desired profile is mounted and fastened together by means of a screw. This makes it a sub assembly (nut, cam dog and screw) and acts like a single unit. 'Cylinder cover' covers the


entire assembly and has got provision to clamp the unit on the mould. The cam dog is guided thickness wise in the slot provided on cylinder cover and maintained a precision sliding fit between them. So when the lead screw rotates clock wise, it will pull the sub assembly as the rotary motion of this is arrested which leads to the linear movement of the cam dog in one direction. The cam dog comprises plural flanges projecting outwards on both sides to a predetermined length in manner to get in touch with the limit switch as and when the lead screw is rotated, which rotation in turn actuates the nut providing the cam dog to move in linear motion. The cam dog is located in a slot such that only two degrees of freedom is allowed for its movement. This movement will cause the activation of the first plunger of the limit switch and send signal to PLC. After receiving signal, as per program, motor starts rotating anti clockwise who in turn rotates lead screw and will push the cam dog in opposite direction. This causes the activation of second plunger of the limit switch at desired position. The pitch of the lead screw and nut threads is maintained' as lmm. So in this case, one complete rotation of the motor will result in lmm linear movement of the cam. Different combinations can be attained by varying the actuating points of cam and by varying the pitch of the screw.


Advantages :
• There is a precise control on rotary movement of the threaded core for clockwise and anticlockwise direction.
• The controller unit can be attached outside the mould, so it is advantageneous for visibility and maintenance.
• The actuation block can be replaced easily for the changing number of rotation, if required.
• The limit switches can be kept out of the mould, so it is out of high temperature and oily region.
• Dismantling and maintenance is easy without disturbing the setting and assembly of the complicated mould.


WE CLAIM
1. A controller unit for use in injection molding apparatus to precisely achieve clockwise and anticlockwise movement of threaded core said injection molding apparatus, said unit comprising:
a cam assembly comprising a cylindrical cover means securing lead screw therein being mechanically coupled to a motor on one end and a guiding means on the other end, said guiding means providing mechanical support to said lead screw,
wherein said cam assembly comprising cam dog means being disposed in a slot provided in said cam assembly so as to allow two degrees of freedom to said cam dog means; said cam dog means being operatively connected to said lead screw by connecting means; a limit switch; a PLC circuit; and
wherein rotary movement of said motor being transmitted to said cam dog means through said lead screw such that said rotary movement in co-operation with said slot means is converted into a linear motion of a cam dog means in a manner that said cam dog activates said limit switch which in turn sends

signal to said PLC circuit for changing direction of rotation of said motor.
2. Controller unit as claimed in claim 1 wherein said cam dog means comprises plurality of flanges slidably located on said slot means projecting to a pre-determined length so as to actuate the limit switch.
3. A controller unit as said in claim 1, in which different working lengths / rotations can be achieved by varying actuating points in flange of cam dog and by varying the pitch of lead screw and nut.

4. Controller unit as claimed in claim 1 wherein said connecting means is a nut.
5. Controller unit as claimed in claim 1 wherein said cam dog means further comprises of alien screw adapted to connect said cam dog means to said nut.
6. Controller unit as claimed in claim 1 wherein said guiding means is a bush.
7. A cam assembly comprising a cylindrical cover means securing lead screw therein being mechanically coupled to a motor on one end and a guiding means on the other end, said guiding means providing


mechanical support to said lead screw, wherein said cam assembly comprising cam dog means being disposed in a slot provided in said cam assembly so as to allow two degrees of freedom to said cam dog means adopted to actuate switching means by way of its to and fro linear movement.
8. Cam assembly as claimed in claim 6 wherein said guiding means is a bush.
9. Cam assembly as claimed in claim 6 wherein said switching means is a limit switch.
10. Cam assembly as claimed in claim 6 wherein said cam dog means comprises plurality of flanges slidably located on said slot means projecting to a pre¬determined length so as to actuate the limit switch.
11. A controller unit for use in injection molding apparatus to precisely achieve clockwise and anticlockwise movement of threaded core substantially as herein described and illustrated with reference to the accompanying figures.

Dated this 31st day of March 2009
Saloni Rastogi Of S. Majumdar & Co, Applicant's Agent