JPH0331560B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a relief valve for a hydraulic-pneumatic restrictor pad in a single-acting or double-acting press.

Conventional pad pressure control methods include single-acting overpressure relief valves with a compressed air control device and a hydraulic damping device, which have a high starting pressure peak and a strong tendency to self-oscillation. In this structure, the valve body is pressed against its valve seat by the force generated by the braking air. Sudden pressure increases beyond the desired degree in the blocked space are not dissipated by the reaction inertia of the valve. As a result, the reaction force at the aperture pad increases excessively. The oil flowing out during the downward stroke of the throttle pad causes the valve body of the overpressure valve to swing. Such oscillations can in many cases only be compensated for by a consuming damping device, such as in accordance with Japanese Patent Application No. 46-20239. In such methods, oil is forced out of the cylinder of the throttle pad by the piston of the throttle pad. In this case, the valve body of the valve arranged below the cylinder opens against the pressurized air chamber that cooperates with this valve body. The oil flows into the oil tank, and a constant pressure is thereby created in the oil chamber of the cylinder of the throttle pad, corresponding to the pressure acting in the compressed air chamber. Since the valve body has a tendency to self-excited rocking, a hydraulic damping device is used. The respective control air pressure in the pressurized air chamber and the associated closing speed and closing force are taken into account. This is because the control chamber pressure influences the throttle strength in the reverse stroke throttle valve via the conduit. Since the valve body produces a highly unstable flow pattern, large expenditures in complex damping systems and fastening techniques are required to prevent rocking. This valve is unsuitable for high pad starting speeds. The starting pressure peak exceeds 150%, which leads to overloading of the structure.

According to East German Economic Patent No. 73020, a control valve with a mechanically controlled front opening is also known in order to avoid starting pressure peaks. This valve requires high mechanical outlays, and in press operations the valve structure is very susceptible to disturbance and requires maintenance.

Similarly, Japanese Patent Application No. 14542, No. 47-
No. 7194, No. 47-10153 and No. 47-10154 disclose methods using electrically controlled auxiliary valves. This absorbs the opening pressure peak. This method is also expensive, susceptible to disturbance, and cannot reliably control rapid strokes because of its opening and closing delays.

All known processes give unsatisfactory results in industrial practice, and in particular these processes are unsuitable for high working speeds.

The invention aims to provide a control valve for a hydraulic-pneumatic restrictor pad in an economically advantageous manner that guarantees a constant stress with low control costs over the entire operating range of the restrictor pad. purpose.

The object of the invention is that, by means of a multistage control of the control piston and by arranging channels and spaces that allow the pressure medium to flow easily, it is possible to avoid starting pressure or opening pressure peaks at high operating speeds, and therefore to reduce the throttling. The purpose of the present invention is to provide a control valve for a hydraulic-pneumatic throttle pad that is structured so that stress peaks do not occur in the throttle pad and that no wobbling occurs during process-conditioned outflow of pressure medium.

According to the present invention, the member into which the valve is inserted consists of a sealing valve body and a main control piston guided by the sealing valve body, which is guided inside the valve body through a constriction member on the sealing valve body. A pressurizing plunger is arranged,
The main control piston also slides along the piston rod of the auxiliary control piston, and the sealing valve body is in fixed operative connection with the auxiliary control piston, and the oil chamber and the sealing valve body and the mating surface of the main control piston are in contact with each other. This goal is achieved by arranging a control channel as a connecting element between the two.

In the starting position, a gap or front opening exists between the valve body and the valve seat of the sealing valve body. Therefore, all spaces and channels in front and behind the valve seat are filled with low pressure oil. The main control piston is actuated by control pressure air, but the auxiliary control piston is not actuated. At the moment of depression of the throttle pad plate, the oil pressure in the space above the sealing valve body or pressure plunger increases in response to the throttle action of the front opening gear. At the same time, the same pressure is generated in the space between the sealing valve body and the main control piston via the control channel.
Since the sealing valve body cannot close against the pressure acting from above, the main control piston moves downwards. When approaching the bottom dead center of the pad stroke and the oil flow weakens, the sealing valve body closes more and more, thereby keeping the working pressure of the oil above the valve constant. At the moment when the motion comes to rest and the return stroke begins, the oil pressure is no longer present, so that the auxiliary control piston is acted upon by air, which prevents the opening of the sealing valve body.

In the following, the invention will be explained in more detail with reference to its embodiments. The attached figure shows a cross section of a relief valve according to the invention.

A sealing valve body 8 is movably arranged in a hole in the valve housing 2 which communicates with a channel and a space for the pressure medium, in particular the pressure oil. A separately guided pressure plunger 10 is seated thereon via the constriction member 1 . Further, the valve body 8 is arranged in the control guide groove 3 in the axial direction.
It is equipped with Further, the sealing valve body 8 is fixed to one end of the piston rod 9. piston rod 9
At the other end an auxiliary control piston 7 is seated, which auxiliary control piston 7 slides in an auxiliary control cylinder. A main control piston 5 is movably arranged on the piston rod 9, which main piston 5 slides in a main control cylinder 6. Between the sealing valve body 8 and the main control piston 5, depending on the positions of these two,
A gap or space 4 is present.

The function is explained below in connection with the operating cycle of the aperture pad. In the starting position, a gap or front opening exists between the valve housing 2 and the valve seat of the sealing valve body 8. Therefore, the space before and after the valve seat of the sealing valve body 8 and the guide groove 3 are filled with low pressure oil. The main control cylinder 6 is subjected to control air pressure. The auxiliary control piston 7 is not activated. Depending on the oil pressure, the sealing valve body 8 seats on the main control piston 5 without a gap (space 4). At the moment of depression of the throttle pad plate, the oil pressure increases in the space above the sealing valve body 8 or the pressure plunger 10 due to the restraining action of the throttle pad. At the same time, via the control guide groove 3,
An equivalent pressure is created in the space 4 between the sealing valve body 8 and the main control piston 5. Since the sealing valve body 8 cannot close against the pressure acting from above, the main control piston 5 moves downwards. An area proportional equilibrium state is established between the working pressure of the pressure oil and the control pressure air. Sealing valve body 8 and pressurizing plunger 10
The spatial separation of the control surface and the sealing surface of the valve body in the form of , results in stable pressure and stress values. Therefore, quiet, vibration-free running of the throttle pad is achieved. When the bottom dead center of the pad stroke is approached and the oil flow weakens, the sealing valve body 8 gradually closes, thereby keeping the oil pressure acting on the valve constant. At the moment when the motion comes to rest and the return stroke begins, the oil pressure is no longer present, so that the auxiliary control piston 7 is acted upon by air, which prevents the opening of the sealing valve body 8. In this way, an interruption of the upward movement of the diaphragm pad is achieved.

[Brief explanation of drawings]

The drawing is a sectional view of a relief valve according to the invention. DESCRIPTION OF SYMBOLS 1... Narrowing member, 2... Valve box, 3... Control guide groove, 4... Gap, 5... Main control piston, 6
... Control cylinder, 7 ... Auxiliary control piston, 8
... Sealing valve body, 9 ... Piston rod, 10 ...
Pressure plunger.

Claims (1)

[Claims] 1. A valve nesting member disposed between the cylinder chamber of the throttle pad and the oil tank and movably arranged in the valve housing, the valve nesting member being connected to the pneumatic auxiliary control piston, The nesting member consists of a sealing valve body 8 and a main control piston 5 guided by the sealing valve body 8, on which pressurization is guided through the valve body 2 through a constriction member 1. A plunger 10 is arranged and the main control piston 5
slides along the piston rod 9 of the auxiliary control piston 7, the sealing valve body 8 is fixed to the auxiliary control piston 7, and the connection between the oil chamber and the sealing valve body 8 and the mating surface of the main control piston 5 A relief valve for a hydraulic-pneumatic throttle pad, characterized in that a control guide groove 3 is formed in a sealing valve body 8 as an element.