DE1087863B - Overpressure safety valve - Google Patents

Description

GERMAN

The invention relates to a pressure-controlled pressure relief valve that controls the pressure difference between opening and closing 'the valve keeps within determinable small limits.

Pressure relief valves are known which are controlled by the hydraulic pressure itself. this happens usually so that a special control piston, which is acted upon by hydraulic pressure and through a The spring is kept in equilibrium, moves when there is overpressure and this is the actual overpressure valve opens. As soon as the pressure has dropped again, the spring returns the control piston, and the valve opens.

Here, the closing pressure is always much lower than the opening pressure, which is due to the friction of the control piston and its guides as well as the difference between the areas of the control piston and the effective valve opening. With many devices - such as B. with hydraulic pit rams - However, the difference between the opening and closing pressure must be as small as possible.

The invention aims to keep this difference within narrow definable limits and at the same time to achieve particularly small structural dimensions. According to the invention, this is achieved by that a provided in a known manner pressurized control piston by means of a reduction acts in the opening direction on the closing body of the overflow valve. Relevant for the difference In addition to the friction between the valve parts, the relationship between the opening and closing pressure is above all the ratio the control piston force to the force that is required to open the closing body. The mathematical one The relationship is represented by the following formula, neglecting the friction:

Pö _A. tP

Overpressure safety valve

Ps

i-D *

In this formula, Pö denotes the opening pressure, Ps denotes the closing pressure, d denotes the effective diameter of the overflow valve, i denotes the reduction ratio and D denotes the effective control piston area. If you want to keep the difference between the opening and closing pressure within the limits of about 5% in pressure relief valves, in particular in pressure relief valves for hydraulic rams

The relationship

if the Rei registrants are neglected:

BWG Bergwerk- und Walzwerk-Maschinenbau GmbH,
Duisburg, Mercatorstr. 74

Oskar Noe, Mülheim / Ruhr-Speldorf,

Friedrich Kaempken, Duisburg,

and Wolfgang Reiners, chapels near Moers,

have been named as inventors

exercise at least 1:20. If one takes into account the friction that occurs, then one arrives at Kraftbzw. Area ratios from 1: 30 to 1: 40. As you can see from the formula, you could do this Generate reduction ratio in a purely hydraulic way by making the area of the control piston 30 times or 40 times larger than the effective the opening area of the overflow valve. However, you get structurally smaller dimensions if a mechanical reduction is switched on. It therefore depends essentially on the ratio of the tax force to the valve opening force.

The drawing shows an exemplary embodiment of the invention.

The drawing shows a pressure-controlled pressure relief valve, partially in section, in which the control piston acts on the closing body of the overflow valve by means of a lever reduction. It denotes 1 the valve housing, 2 the control piston and 3 a spring, the control piston 2 according to the hydraulic Keeping pressure in balance. The force of the control piston 2 is a plunger 4, a adjustable anchor screw 5, a lever 6 and a plunger 13 on the one formed by a ball 8 Transfer closing body. The ball 8 sits in a housing 7, with a guide 9 and a Spring 10 is performed. The connection to the pressure line is 11, the connection hole to the overflow valve designated by 12 and the sealing seat by 14.

If the valve or the associated device is under hydraulic pressure, the ball of the Overflow valve acted upon by hydraulic pressure and with increasing pressures more and more tightly their tight fit bridged, d. that is, the valve in contrast to simple overflow valves with increasing pressures more and more tight and the seat pressure greater will. However, this stronger seat pressure must be overcome when the valve is mechanically opened,

009 588/236

from which it follows that the forces of the control piston and the opening forces for the overflow valve in must have an appropriate relationship to one another.

The working cycle of the valve proceeds as follows: The hydraulic pressure acts on the control piston 2, which in turn compresses the spring 3 accordingly via the plunger 4. A balance is established between the piston force and the spring force. When the set pressure is exceeded, the plunger 4 actuates the lever 6, which can be pivoted about an axis 15, via the stop screw 5. The lower short end of the lever 6 then actuates the plunger 13, which lifts the ball 8 slightly from its seat. As a result, the pressure drops, the control piston 2 returns, and the plunger 13 and the ball 8 are released. The ball 8 is then immediately acted upon again by hydraulic pressure and pressed onto its seat 4.

To improve the way of working and to simplify The plunger 4 is produced in the control piston 2 by means of a centering point 17 in a centering recess 16 led. This ensures that the force of the spring 3 acts centrally is transferred to the control piston 2. The control piston 2 cannot tilt, and the friction in his leadership is low.

The pressure relief valve according to the invention can be used extremely well for hydraulic pit rams because it has only small structural dimensions and only a small difference between opening and Has closing pressure. Of course, this controlled pressure relief valve can also be used with others Aggregates, e.g. B. in hydraulic working cylinders that do not exceed a certain pressure force may be used. A particular advantage of this design results from the fact that the locking ball of the overflow valve is raised and lowered and not as is more common with overflow valves Kind of opened by the pressure and pushed back onto its seat by the spring force. This Striking work of the usual overflow valves can destroy the valve seat in a short time and / or the valve body.

Claims (5)

Patent claims: 1. Overpressure safety valve with a spring-loaded control piston, characterized in that that the closing body is opened by the control piston by means of a reduction. 2. Overpressure safety valve according to claim 1, characterized in that the ratio of Opening pressure to closing pressure Po Ps i-D * where d is the diameter at the valve seat and D is the diameter of the control piston and i is the reduction ratio and the quotient which essentially determines the pressure difference iD ² is less than 0.1, 3. Overpressure safety valve according to claim 1 and 2, characterized in that the closing body pressed onto its seat by hydraulic pressure and opened against the direction of flow will. 4. Overpressure safety valve according to Claim 1.2 and 3, characterized in that the control piston has a limited idle stroke before opening covered before its movement is transmitted to the closing body. 5. Overpressure safety valve according to one of the preceding claims, characterized in that that it is built into a hydraulic pit ram. Considered publications:
German patent specifications No. 30680, 669318,
139. 1 sheet of drawings I 009 588/236 8.60