Cutting – With means to monitor and control operation – Including means to correct the sensed operation
Patent
1987-08-17
1989-04-25
Yost, Frank T.
Cutting
With means to monitor and control operation
Including means to correct the sensed operation
83 72, 83137, 83527, 83548, 83615, 83617, 83639, 91173, 91189R, 91519, 100269B, B26D 512, F15B 1508, T15B 2102
Patent
active
048236586
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to improvements to punch presses and in particular to an improved punching head assembly for punch presses.
BACKGROUND ART
Commonly punch presses are employed to punch holes in metal sheet and plate and, for this purpose, most punch presses comprise a C-shaped frame having a punch head assembly adapted to reciprocate the punch in a vertical direction to co-operate with a die over which the sheet or plate to be punched is positioned. Many such presses employ crank drive arrangements to cause reciprocation of the punch. However in such arrangements the stroke of the punch cannot be varied easily, for example to cater for varying material thicknesses. Furthermore, the noise generated by such press arrangements during punching is relatively high.
It is also known to drive punching tools by hydraulic means, for example by reciprocating pistons. Whilst in this arrangement the stroke of the punch can be varied, noise generation still remains a problem. Additionally, hydraulic drives are not normally adapted for rapid punching of thin plate as well as for punching thicker plate.
OUTLINE OF THE INVENTION
It is an object of the present invention to overcome or alleviate at least some of the above disadvantages by providing an improved punching head assembly for a punch press which may be readily adapted for punching both thin and thicker plate.
It is another object of the present invention to provide means for controlling the operation of the punching head assembly so as to reduce generated noise levels and/r to optimise punching rate in accordance with the material being punched.
It is yet another object of the present invention to provide an improved stripper assembly to facilitate the stripping of the punch tool from the work sheet.
In one broad form the present invention provides a punching head assembly for a punch press, said punching head assembly comprising a cylinder portion having a first piston member adapted for reciprocating movement therein, said first piston member having a pair of radially inwardly stepped portions each having a radial work surface defining part of a respective one of extend and retract chambers between said piston member and said cylinder portion, said extend and retract chambers being in respective fluid communication with control means adapted to alternate the flow of pressurised fluid to said chambers to obtain reciprocating movement of the piston member; said punching head assembly further comprising a second piston member juxtaposed axially with said first piston member and having a radial work surface defining part of a second extend chamber which is in controlled fluid communication with said control means, whereby the flow of pressurised fluid to said second extend chamber can be selectively opened to drive said first and second piston members together and closed to disable said second piston.
Preferably the work surface of the first extend chamber is greater than the work surface of the second extend chamber.
In a first mode of operation, the fluid communication path between the control means and the second extend chamber is closed so that only the first piston is driven. In this mode of operation the punch can be operated at a high rate at relatively low force. In a second mode of operation, the fluid communication path between the control means and the second extend chamber is opened so that the second piston member is driven via the second extend chamber, and in turn, drives the first piston member. The first piston member is also driven via the first extend chamber at the same time. (The first and second extend chambers may share a common fluid communication path for this purpose). In this mode of operation, a significantly higher punching force is achieved, but at lower speed since a greater volume is required to be filled by hydraulic fluid during each stroke.
Typically, the control means comprises a plurality of microprocessor-controlled servo valves which control the flow of pressurised fluid to the chambers.
Adva
REFERENCES:
patent: 3157070 (1964-11-01), Heidrich
patent: 3563136 (1971-02-01), Valente
patent: 3602098 (1971-08-01), Balkee
patent: 4030391 (1977-06-01), Swanson et al.
patent: 4208935 (1980-06-01), Kollmar
Phan Hien H.
Yost Frank T.
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