DD286946A7 - PROCESS FOR PNEUMATIC PRODUCTION OF STOES - Google Patents

Abstract

The invention relates to a method for the pneumatic production of Stoeszen for the examination of equipment, equipment u. ae. on their mechanical strength and their operating behavior, in particular under load as a result of the action of pressure waves. The piston of a working cylinder, on the piston rod, the clamping plate is fastened for the Pruefling is driven with a back pressure p1 in the lower cylinder chamber in the starting position to the top. By opening a Schnelleinlaszventils the upper cylinder chamber, the piston with the working pressure p2p1, which was provided in an accumulator, applied, and thereby accelerated. The thereby increasing pressure in the lower cylinder chamber, in conjunction with a Auslaszventil, a collecting box and an adjustable throttle causes a slowing down of the system according to the required time function. By means of the proposed method according to the invention, it is possible to vary the impact parameters (amplitude, duration, rise time, decay time) as a result of changes in the backpressure, the volume, the working pressure and the chronological sequence of the valve circuits. pneumatic shock generation; Working cylinder; Accumulator; Stoszparameter; Valve circuit}

Description

For this 1 page drawing

Field of application of the invention

The invention relates to a method for the pneumatic generation of shocks with high accelerations and large vibration paths.

The method can be used, in particular, for testing (shock test) devices, equipment and the like. Ä. Are applied to their resistance to the effects of a seismic shock. In addition to the magnitude of the acceleration is particularly the time course, the duration and the direction of the impact of crucial importance for the analog load of the specimen.

Characteristic of the known technical solutions

Shock methods in general are indicated in LENK / REHNITZ "Schwingungsprüftechnik" (Verlag Technik, Berlin, 1974).

According to the type of energy conversion, the following processes have heretofore achieved extensive technical significance:

mechanical - mechanical conversion, electromechanical conversion, hydraulic - mechanical conversion or their combinations.

Known methods according to the principle of mechanical-mechanical conversion generally use a plate with mounted test specimen, which is guided by one or more vertical columns and falls on an anvil in free fall and whose shape is chosen according to the profile of the shock shape to be generated. The commonly used anvils may be made of a suitable elastic material, have hydraulic or pneumatic compression, or undergo plastic deformation. These methods, in particular for impact molding, have a variety of patents, e.g. DD-PS 50,355, DD-PS 70,772, DD-PS 74,653, DD-PS 75,820, DD-PS 92,140, DE-PS 1,110,916, DE-PS 2,020,396, US-PS 2,846,869, US-PS 3,100 .983, U.S. Patent 3,106,834, U.S. Patent 3,402,593, U.S. Patent 3,566,668, U.S. Patent No. 462,099, U.S. Patent No. 476,474, U.S. Patent No. 485,337, U.S. Patent No. 523,319, British Patent No. 1,085,064 , DD-PS 150.410.

However, all methods have several disadvantages, in particular they require a considerable drop height and thus a large space requirement. Because of the lateral limitation of the fall plate through the guide columns, the test piece may not have too large dimensions. As a rule, impact impacts occur when the fall plate impacts the anvil. Other disadvantages are the occurrence of shear forces when the center of gravity of the entire falling part is not in the axis, and the possibility of producing only vertical impacts.

Processes with hydraulic-mechanical conversion require extensive generator, control, power and work stages to realize the required shocks. With appropriate dimensioning, long shock durations and large vibration paths can be achieved. Disadvantages here are only achievable due to the hydraulic circuit while low to medium accelerations and the large number of required sealing points.

The use of pneumatic processes takes place primarily as a mixed system with hydraulics.

In SU-PS 783,615 - Int. Patent class G 01 M 7/00 - a shock tester is described, which has a working cylinder to achieve high accelerations and long distances, filled in the upper chamber with gas and in the lower with a liquid. As preparation, a working pressure is created in the upper chamber by filling with air. In this

Starting position is the working pressure in the lower chamber equal to that in the upper. By opening a drain valve of the lower chamber, the liquid can flow through outflow channels and a throttle, the compressed gas above relaxes and the DUT is moved in an abrupt manner.

This method has the disadvantage that in the initial position of the working pressure equal to the back pressure and the volume of the lower cylinder chamber is constant, whereby the work area is restricted. Other disadvantages are the use of different media, which requires two separate systems, and the use of a liquid as a counterpressure, resulting in a lower outflow velocity and consequently lower accelerations than gas.

An analogous method describes the BRD-OS 2.012.601 Int. Patent class G 01 M 13/00.

In SU-PS 690,351-Int. Patent class G 01 M 7/00-was a shock tester with pneumatic cylinder, hydraulic auxiliary cylinders and a solenoid for shock release proposed. After filling the lower chamber of the working cylinder with the working pressure of the magnet is actuated and moves the test piece on the piston, piston rod and plate.

The auxiliary cylinders cause by a build-up of pressure in the upper chamber during the shock process, a deceleration and the termination after the pressure equality in both chambers. To prepare a new shock, the liquid must be conveyed back within the auxiliary cylinder.

The disadvantage here are also required for 2 media supply and control devices, the need for auxiliary cylinders and the extensive sealing points.

In the FRG-OS 2.160.884- Int. Patent G 01 N 3/36-was proposed to use a test hammer with pneumatic drive, in which the clamping plate for the test specimen forms the upper end of a hollow cylinder, which is arranged in a fixed housing with two constant in size pressure chambers and the Bumping action is caused by the working pressure in the upper pressure chamber, wherein in the initial position of the working pressure is always less than the back pressure, since the pressure difference is needed to hold the DUT in the starting position.

This test impact has the disadvantage that the working pressure is always less than the back pressure and thus the impact process is essentially dependent on the design of the opening valve, which greatly limits the scope. Other disadvantages are in addition to the DUT large mass to be moved, the large number of sealing points through the use of a double cylinder and the required impact of the punch on the solid housing. By the latter undesirable vibrations or bumps are introduced into the system.

Object of the invention

The object of the invention is to provide a method for the pneumatic generation of high acceleration and long duration shocks for the testing of equipment, equipments and the like. medium to large mass in horizontal and vertical direction to create.

With little technical effort to ensure that the test shock a reproducible shock shape on amplitude, time, rising edge and cooldown is adjustable.

Explanation of the essence of the invention

The invention has for its object to provide a shock test method for generating shocks, which allows to examine specimens for their impact resistance, the impact parameters should be variable and reproducible on a large scale. In order to avoid the disadvantages of a hydraulic insert (sealing problems, return of the medium), the method on pneumatic basis with additional utilization of the compressibility of the air to create and to ensure a large number of shocks no component used, which is elastically or plastically deformed for impact molding.

According to the invention the object is achieved in that a pneumatic Einkolbenarbeitssystem is used, wherein first the piston is driven with open first cylinder chamber by filling air and generating the back pressure pi in the second cylinder chamber in the final position. This back pressure p, is chosen so that the piston with specimen is securely fixed in this position. The first cylinder chamber is now closed. Subsequently or simultaneously, a pressure accumulator with the working pressure p ₂ , which is greater than the back pressure P ₁ , filled via a filling valve.

To trigger the shock, the air present in the pressure accumulator is admitted by opening a fast intake valve in the first cylinder chamber. Due to the pressure difference between the two chambers, the piston with piston rod, table and DUT is accelerated. After the initial high acceleration because of the large pressure difference, this decreases with increase of the pressure in the second chamber and decrease of the pressure in the first chamber due to the piston movement, it is initiated by utilizing the compressibility of the air, the deceleration (generation of the I.Phase 2nd half-wave of the acceleration). The subsequent time- and / or path-dependent controlled opening of the outlet and the pressure reduction valve causes the further deceleration and the formation of the 2nd phase of the 2nd half-wave. Finally, the combination of the exhaust valve with a header and a throttle ensures a second low compression and a low outflow velocity, so that the piston now slowly touches down on the cylinder cover with negligible acceleration and no ringing occurs.

embodiment

With the following embodiment, the invention will be explained with reference to a method for the generation of vertical shocks. The attached drawing shows a schematic representation.

Through the filling valve 1, the lower cylinder chamber 2 of the working cylinder 3 is filled with the back pressure p, wherein the exhaust valve 5 is closed. For venting the upper cylinder chamber 7 while the vent valve 16 is opened, the fast intake valve 4 but closed. The back pressure pi is chosen so large that the movable part, consisting of the piston 6, the piston rod 8, the platen 9 and the DUT 10 is pressed into the upper end position and fixed there. At the same time, the pressure accumulator 11, whose volume has been previously set by means of spindle 13 and pressure accumulator piston 12, via the pressure accumulator valve 15 with the working pressure (p ₂ > Pi) filled.

By opening the quick inlet valve 4, the air flows from the accumulator 11 into the upper cylinder chamber 7. Since the pressure built there is greater than the back pressure pi, the piston 6 is accelerated with the parts attached to it down. After the lapse of a time set according to the required stroke, the exhaust valve 5 and the depressurizing valve 17 are opened. The air can escape from the upper cylinder chamber 7 and from the lower cylinder chamber 2. The arrangement of a header tank 18 and a throttle 14 cause the shock is decelerated according to the required function and finally a striking of the piston 6 is prevented on the lower cylinder cover of the working cylinder.

The impact parameters depend on the DUT mass, the working pressure, the backpressure, the volume of the accumulator, the dimensions of the working cylinder and the switching times of the valves and can be adapted to the respective test conditions.

Claims (5)

Invention claim: 1. A method for the pneumatic generation of shocks with high acceleration and long duration of impact for the testing of equipment, equipment u. Ä., Characterized in that the piston (6) of a working cylinder (3) with open vent valve (16) via the inlet valve (1) with a back pressure p _{1 (} which is smaller than the pressure in the accumulator (11) existing working pressure p ₂ , is moved into the upper end position and then between the upper cylinder chamber (7) and pressure accumulator (11) located fast intake valve (4) is opened, the piston (6) and thus the specimen (10) initially accelerated, then by compressing the air delayed in the lower cylinder chamber (2) with the inlet valve (1) closed and subsequent opening of the pressure reduction valve (17) and the outlet valve (5) with downstream collection box (18) and throttle (14) the impact process shortly before reaching the lower end position and a bounce-free impact is achieved. 2. The method according to item 1, characterized in that the impact parameters are variable by a time and / or path-dependent control of the exhaust valve (5) and the pressure reduction valve (17). 3. The method according to item 1, characterized in that the volume of the pressure accumulator (11) by arrangement of pressure accumulator piston (12) and spindle (13) is variable 4. The method according to item 1, characterized in that the function of the pressure reduction valve (17) from the vent valve (16) is taken over. 5. The method according to item 1, characterized in that by appropriate arrangement of the working cylinder (3) impact tests in any direction are feasible.