FORM-2
THE PATENTSACT, 1970
(39 of 1970)
(39 of 1970)
COMPLETE SPECIFICATION
(Section 10)

"A RETURN PIN SPRING ASSEMBLY AND A SPRING CARTRIDGE FOR
EJECTION OF COMPONENTS FROM MOULDS"
LARSEN & TOUBRO LIMITED,
L&T House,
Ballard Esteate,
MUMBAI-400 001, Maharashtra State, India
An Indian Company registered under the
Provisions of the Companies Act, 1956
The following specification particularly describes the nature of this invention and the manner in which it is to be performed :-
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This invention is related to a return pin spring assembly and a spring cartridge for ejection moulds. This invention is beneficial in manufacturing the moulds. It is known that moulds are used for producing plastic components of consistent quality and in large quantities, using moulding machines.
PRIOR ART:
There are many types of moulds and moulding machines in use. There are many manufacturers of moulds and moulding machines. There are also many makers of standard mould-parts.
When moulds are used for manufacturing components, it is required to eject the components after every cycle using ejector pins in order to keep mould ready for the next cycle.
To build safety into the mould, it is essential to provide springs for the retraction of the ejectors, every time the ejector plate/s moves forward.
When springs are used for ejector retraction, it becomes very difficult and cumbersome to assemble and disassemble the mould. The free length of the springs creates problems in assembly and disassembly.
It takes more than one person to assemble and disassemble the mould. Much time is consumed in this activity
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Coil (compression) springs are generally used for this purpose. Another type of "spring" in use is "bow" washer/s (disc washers) where the deflection and load can be separately controlled theoretically. But practically, when bow washers are used it is much more cumbersome and susceptible for human errors, as it is difficult to know the number of bow washers used and the way in which they are assembled. This is explained in detail in figures 1, 2, 3, 4, 5 of the drawings accompanying this specification.
When compression springs are used as shown in reference fig.6, many times it may be required to add additional springs to get the desired load.
All the above requirements make the design/s of moulds more complicated and unwieldy.
OUR INVENTION:
The object of the present invention is, therefore -to devise means to simplify operations of assembling and disassembling of the moulds, and the same is achieved by introducing novel systems of return pin spring assembly/s and/or Spring Cartridge/s. The 'return pin spring assembly' or the 'CARTRIDGE' assembly is located in between punch holder plate and ejector pin retainer plate. Any desired load and deflection is possible with proper selection of the components.
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In all these assembly/s, due to their unique design it is veiy easy to assemble and disassemble the units in the mould. One person can assemble or dissemble.
This invention saves time, money and employee fatigue. There is no possibility of errors. STATEMENT OF INVENTION:
A return pin spring assembly and a spring cartridge for ejection in moulds, the said return pin spring assembly for use in case of normal loads comprises a pin having circular cross section over a particular length and oblong cross section over the remaining length, the dimensions of the said pin thus depending upon the length of ejection required to eject the component from the mould and the size of the mould, two washers of suitable thickness with one fixed washer at one end and the other moving washer, a compression spring of either circular cross section or rectangular cross section, being held in between the said washers, the said moving washer having outer circular periphery of suitable diameter and the inner periphery is oblong as per the oblong cross section of the said pin, the said compression spring being pre-compressed to the desired length and load and held in position by the said fixed washer and a screw; and the aforesaid spring cartridge for use in case of excessive or higher loads where higher ejection force is required, comprising a pin being provided with a head or collar at one end, the other end of the said pin being provided with two circular washers, one fixed with inner diameter smaller than the diameter of the said pin and the other moving with inner diameter more than the diameter of the said pin, a compression spring being provided in between the said washers and the said head or collar, the said fixed washer and a screw prevent the said spring and said moving washer from coming out of the said pin
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DRAWINGS :
The invention will now be described with the help of drawings accompanying this specification, wherein salient features have been shown by suitable numerals and referred to appropriately in the following description;
Drawings consist of 8 figures.
Figs. 1, 2, 3, 4 & 5 show the "bow" washers & usage of the same.
Fig.6 shows the return pin spring as per earlier art.
Fig. 7 shows the return pin spring assembly as per this invention,
Fig. 8 shows the spring cartridge assembly as per this invention.
Referring to Figures, fig. 1 shows a typical bow washer (1). To "flatten" this particular bow washer, some definite "load" is required in axial direction. This load causes some definite "deflection". The bow washer/s are always used in "many numbers" or plurality, and the plurality is used in combinations of pairs of bow-washers; pairs being 1-1, or 2-2, or 3-3 as shown in figures 2, 3 & 4, respectively.
Fig. 2 shows assembly of 2 bow washers (lb & lc) wherein, to "flatten" this assembly of fig.2, with respect to a single bow washer of fig.I, the load required is double, and the total deflection is also doubled.
Fig. 3 shows again, another mode of assembly of 4 bow washers (Id, le, If; lg). Compared to fig.2, for fig.3, the required load gets doubled, but the total deflection is
same, to "flatten" the assembly.
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Fig. 4 shows assembly of 6 bow washers (lh, li, lj, Ik, 11, lm). Compared to fig.2, for fig.4, required load is "3 times", but the deflection is same.
Thus, from figures 1, 2, 3, 4 it is clear that several combinations of bow washers can be used to achieve the desired load and deflection.
Fig. 5 shows a typical usage employing the assembly (2) of bow-washers (In, lo, lp, lq....). Here, the plurality of bow-washer is composed of pairs of 2-2. Bow-washers (In, lo, lp, lq) are mounted on a guide pin (3). Guide pin (3) has head or collar (4) on which assembly (2) of bow-washers is mounted concentrically. Item (5) is the common axis or centre-line of the pin (3) and bow-washers. The pin with the assembly in compressed state is employed in moulds and/or press tools for the purpose of "ejection" and/or stripping of components. A typical case shows a holder washer plate (6) holding the bow-washers, a "separator" (7) and the portion (8) which is to be "ejected". From the fig. 5, it is also evident that there exists the possibility of human errors in assembling the bow-washer springs, thereby affecting the very function of the assembly.
Fig. 6 shows as per earlier art, a return pin spring assembly (10). This consists of a "return" pin (11) serving as guide pin or location pin, during assembly and disassembly. On this pin (11) is placed a spring (12) which may better be called as the "return" spring (12). Now, the location is defined & guaranteed by the pin (11), and the retraction is assured by the return spring (12). Several such assembly / s (10) are in use in present day moulds.
Fig 7 shows our novel [pin & spring] assembly (20) or simply the return spring (20). This return spring assembly (20) has a pin (21) having circular-cross-section (22)
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over a particular length (23), and, at remaining portion of length (24), the pin (21) has an oblong cross section (25). At the junction of circular ^nd oblong sections, a specially made washer (26) is placed. The washer (26) has oblong hole (27) in the middle. The washer (26) is strong and robust. On this washer (26) a spring (28) is placed. The assembly of the return spring (20) can be made in any known manner/s out of which one possible mode is shown in fig; and thus the collar or head (29) keeps the spring "arrested" in position in between the head (29) and washer (26). Any desired deflection and load is designed and achieved by combination of parameters : spring-wire-diameter, spring-coil-diameter, spring-pitch, number of turns of spring and the like.
Fig.8 shows yet another novel system (30) Of the spring "CARTRIDGE" assembly (30). Here, the spring cartridge assembly (30) has a pin (31) having circular-cross-section (32). The pin (31) has a collar or head (33) at one end. On the pin (31), a washer (36) is placed. The washer (36) is strong and robust. In between this washer (36) and collar (33) is placed a spring (38). The assembly of this spring cartridge (30) can also be made in any known manner/s out of which one possible mode is shown in figure by items (39.1) and (39.2).
APPLICATIONS. USE, ADVANTAGES :
Any desired load and deflection is possible with phoper selection of the spring and the pin. This saves time, energy and money. There is no possibility of errors: The pre-assembled unit/s works like a cassette : Even though movement of spring is possible, the
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spring CANNOT come out of the assembly. There is no "jumping" out of the spring as was in earlier art. There is no accident.
VARIATIONS :
1. The drawing shows that the spring is made from wire having 'round' circular cross-section. The spring can be made with wire having rectangular cross-section.
2. The 'oblong' design can have other geometrical shapes : Triangular, Squarish, Pentagonal, Hexagonal... and the like.
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WE CLAIM:
A return pin spring assembly and a spring cartridge for ejection in moulds, the said return pin spring assembly for use in case of normal loads comprising a pin having circular cross section over a particular length and oblong cross section over the remaining length, the dimensions of the said pin thus depending upon the length of ejection required to eject the component from the mould and the size of the mould, two washers of suitable thickness with one fixed washer at one end and the other moving washer, a compression spring of either circular cross section or rectangular cross section, being held in between the said washers, the said moving washer having outer circular periphery of suitable diameter and the inner periphery is oblong as per the oblong cross section of the said pin, the said compression spring being pre-compressed to the desired length and load and held in position by the said fixed washer and a screw; and the aforesaid spring cartridge for use in case of excessive or higher loads where higher ejection force is required, comprising a pin being provided with a head or collar at one end, the other end of the said pin being provided with two circular washers, one fixed with inner diameter smaller than the diameter of the said pin and the other moving with inner diameter more than the diameter of the said pin, a compression spring being provided in between the said washers and the said head or collar, the said fixed washer and a screw prevent the said spring and said moving washer from coming out of the said pin.