Plastic and nonmetallic article shaping or treating: processes – Mechanical shaping or molding to form or reform shaped article – Shaping against forming surface
Reexamination Certificate
1999-05-06
2001-07-17
Mackey, James P. (Department: 1722)
Plastic and nonmetallic article shaping or treating: processes
Mechanical shaping or molding to form or reform shaped article
Shaping against forming surface
C425S451900, C425S595000
Reexamination Certificate
active
06261505
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a mechanism for applying a clamping force to a columnar member which has particular utility in machines for molding articles.
Clamping systems for molding machines typically use means to lock the tiebars in order to connect and disconnect clamping pistons to them. For example, French patent 2,411,694 illustrates a friction means for gripping the column of a three platen machine in order to connect a clamping piston to the column. The design uses a conical locking ring that is pushed into a tapered sleeve, which causes the locking ring to deflect inward and grip the column passing through its central bore. FIG. 4 of this patent shows how the locking ring has longitudinal slots cut through it to facilitate this deflection. The problem with this approach is that the locking ring must slide inside its mating tapered piece in order to be deflected. The high forces generated during this sliding action cause wear on the mating surfaces which substantially shorten the useful life of such a device. Furthermore the friction in the conical seats limits the effectiveness of the gripping action.
U.S. Pat. No. 2,691,799 illustrates a different approach. In this patent, a collet-type locking ring is used to grip a tiebar.
U.S. Pat. No. 3,183,555 to Siegel illustrates an approach using a hydraulic pressure to deflect the walls of a sleeve to grip a tiebar.
U.S. Pat. No. 4,565,517 to Brinkmann illustrates an approach using oil pressure to act on a piston having a conical seat that causes ring segments to grip a tiebar.
German Patent No. 31 44 359 illustrates an approach using a hydraulic piston to push against wedge shaped segments to grip a rod of a piston.
Despite these systems, there still remains a need for a clamping mechanism with stronger gripping action which works faster to minimize the problems with wear and which can be built at a substantial cost saving.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an improved mechanism for applying a clamping force to a columnar member such as a tiebar.
It is a further object of the present invention to provide an improved mechanism for applying a clamping force which has utility in presses, molding machines, and injection molding machines.
It is yet a further object of the present invention to provide an improved mechanism for applying a clamping force which can be built at a substantial cost saving as compared to other mechanical locking techniques.
It is still a further object of the present invention to provide an improved method for applying a clamping force to a columnar member such as a tiebar.
The foregoing objects are attained by the clamping mechanism and method of the present invention.
In accordance with the present invention, a mechanism for applying a clamping force to a columnar member, such as a tiebar, comprises a compressible member surrounding the columnar member for gripping the columnar member and transmitting a clamping force thereto, which compressible member is slidable along the columnar member. The mechanism further comprises a first means for applying a clamping force, which first means has a bore with an engaging surface for receiving and frictionally engaging the compressible member. The frictional engagement between the compressible member and the engaging surface prevents any relative sliding movement between the compressible member and the first means. The mechanism still further comprises a second means for applying a clamping force and for causing the compressible member to slide along the columnar member from an initial position to a preload position where the compressible member is compressed by contact with the engaging surface as the compressible member moves between the positions. Compression of the compressible member causes it to grip the columnar member and apply an initial clamping force. The main clamping force is applied to the compressible member and hence to the tiebar by moving the first means to a clamping position. The force applied to the clamp piston during clamp up further increases the hinging effect on the sleeve and thus increases the radial deflection of the sleeve and the gripping action.
The clamping mechanism of the present invention has wide utility. It may be used on many different types of presses and molding machines. It has particular utility with injection molding machines for forming plastic articles.
In one aspect of the present invention, the clamping mechanism of the present invention may be used to applying a clamping force to a mold formed by a first mold half mounted to a first platen and a second mold half mounted to a second platen and having one or more tiebars extending between the first and second platens. The method for applying the clamping force to the mold comprises the steps of: closing the mold, providing a compressible member having a central bore with a diameter about each tiebar, a sliding piston for causing a respective compressible member to move between an initial position and a preload position, and a clamping piston for applying a main clamping force or a breaking force to the mold via the compressible member; activating the sliding piston to cause the respective compressible member with which it cooperates to slide along a tiebar between the initial position and the preload position without the compressible member sliding relative to the clamping piston, whereby the compressible member becomes compressed and grips the tiebar along which it slides; and activating the clamping piston by moving it to a clamping position to cause the compressible member to transmit a main clamping force to the mold via the tiebar.
Other details of the clamping mechanism and clamping method of the present invention, as well as other objects and advantages attendant thereto, are set forth in the following detailed description and the accompanying drawings, wherein like reference numerals depict like elements.
REFERENCES:
patent: 2691799 (1954-10-01), Moeller
patent: 3183555 (1965-05-01), Siegel
patent: 3449795 (1969-06-01), Fischbach
patent: 4372738 (1983-02-01), Black et al.
patent: 4565517 (1986-01-01), Brinkmann et al.
patent: 5133655 (1992-07-01), Schad et al.
patent: 5620718 (1997-04-01), Bohm
patent: 3144359 (1983-05-01), None
patent: 2425321 (1979-07-01), None
patent: 2411694 (1979-08-01), None
patent: 1322012 (1973-07-01), None
patent: WO 96/41711 (1996-12-01), None
Bachman & LaPointe P.C.
Husky Injection Molding Systems Ltd.
Mackey James P.
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