Power plants – Pressure fluid source and motor – Pulsator
Patent
1998-03-05
1999-08-31
Ryznic, John E.
Power plants
Pressure fluid source and motor
Pulsator
60563, 91405, F15B 700, F15B 1522, B60T 1358
Patent
active
059438622
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention is based on a hydraulic machine tool as generically defined by the preamble to the main claim. In a known machine tool of this generic type (German Patent 43 01 983), the work stroke of the work piston is braked by causing the step of greatest diameter, namely of the work piston, that serves the purpose of the rapid traverses to strike the bottom of the corresponding pneumatic work chamber; there is a damping disk on the face of the work piston, but it accomplishes only slight damping.
Machine tools of this generic type are intrinsically high-speed, energy-saving pneumatic systems, with which a hydraulic system is integrated, by means of which latter, after a desired forward stroke in the working direction, a power stroke with very high adjusting force is attainable. Although only pneumatic connections to outside the housing of the machine tool are available, the pressure intensification is accomplished with the aid of the hydraulics. As a result, hydraulic chambers along with pneumatic chambers move in the piston stroke direction, which involves the not-inconsiderable problem of sealing the one off from the other. Air that gets into the hydraulic fluid leads to undesired compressibility of the oil; oil leaking out of the hydraulic portion can cause functional failures.
Damping the work stroke, and sometimes the return stroke as well, remains a problem in such machine tools, which use hydropneumatic pressure intensification. Especially whenever a sheet-metal connection, for instance, is to be made via a suitable tool, and upon idling the step piston, pounds into one of its terminal positions with full force, the result cannot only be considerable noise but also attendant damage. Even though this is an old, widespread problem in such machine tools, aside from the aforementioned elastic disk no damping that in particular is also adjustable to the weight or mass of the tool has yet been found.
OBJECT AND SUMMARY OF THE INVENTION
The machine tool of the invention as defined by the characteristics of the main claim has the advantage over the prior art that depending on the cross section of the choke point or throttle restriction, more or less major damping is attainable, especially toward the end of the work stroke, and this cross section at the throttle restriction can be adapted to the masses involved. For this damping, the hydraulic fluid can be used, with which the remaining hydropneumatic pressure intensifier also functions. The seals, which already have high quality, between the pneumatic chamber and the hydraulic chamber also serve to seal off the annular chamber, so that one additional expensive seal is not needed. The invention can already be achieved in a very simple way and highly effectively in such machine tools, which overcomes the prejudices of the professional field. It is admittedly known in work cylinders to damp the terminal position of the work piston hydraulically or pneumatically, but this known provision does not involve step pistons having the problems discussed above.
In an advantageous feature of the invention, the step piston positively displaces fluid out of the annular chamber through a throttle restriction at least toward the end of the return stroke and in order to brake its return stroke motion. In this way, both the forward motion and the return motion of the step piston and thus the lower dead center range and the upper dead center range of the tool are damped in the reciprocating motion; the additional piston collar, disposed on the step piston and serving to damp the work stroke, accomplishes the return stroke damping with its annular face remote from the annular face used for the work stroke.
In a further advantageous feature of the invention, the annular chamber, on at least one of its end portions, has a taper, which corresponds to the diameter of the piston collar and into which the piston collar plunges toward the end of the stroke and positively displaces the fluid volume, enclosed in this braking cavity or braking chamber,
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Greigg Edwin E.
Greigg Ronald E.
Ryznic John E.
Tox Pressotechnik GmbH
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