DE19823086C2 - Valve control for fluid-powered, flywheel-less reciprocating machine - Google Patents

Description

They are air driven, flywheelless pumps for Airless paint sprayers are known to help achieve a uniform delivery pressure with a piston rod the double-acting, back and forth in the axial direction have driven pump piston connected pump piston. Around a process with only short and as few interruptions as possible To achieve, a quick reversal of stroke direction as well The aim is to utilize the entire displacement.

Controls are known from DE-OS 19 56 322 and DE 24 13 531 B2 mutual application of pressure to the drive piston known when a certain pressure is reached in the work area (When used as intended on a mechanical Stop fixed end of the piston travel) the reversal of stroke initiate. This is higher than that corresponding to the moving load Pressure and can not reduce the lifting or installation space or are used to move a correspondingly larger load, whereby only a low efficiency is achieved. Farther the reversal of the stroke direction is extended by the one to reach this higher pressure time.

A better efficiency can be achieved by using controls achieved with fixed, pressure-independent reversal of stroke direction become. From US 2745386 and US 4870891 are symmetrical built controls of this type are known, but their parts due to the symmetry at least at a standstill by external Influences (vibrations, etc.) are brought into a (middle) position in which a restart is impossible. By a Increase in the number of moving control parts (US 4870891) can with a correspondingly increased manufacturing effort Probability of trouble-free start-up is increased; Prerequisite for a reliable start with any one However, the position of the control elements is asymmetrical. In the past, this was used for steam-operated pumps (e.g. on steam locomotives). Are from this area  Various controls are known, the controls of which are mechanical or operated by (steam) pressure.

For controls with mechanically operated parts, there is often a Disadvantage in that some parts sometimes only by friction in be kept in their position and just as symmetrical built controls can be placed in a position in which restarting is impossible. Furthermore, the Reversal process only occurs on the control parts poorly dampened, increasing the life of these parts is shortened. The arrangement is due to the mechanical actuation the controls on the drive largely fixed and can not or be poorly adapted to existing space. Both mechanical and pressure actuated controls are often designed so that multiple opening and closing processes must run at the same time if possible. This results in high Precise compliance with certain dimensions of the controlling edges over the entire life of the drive. The chronological sequence and possibly the order of the resulting Pressure changes also depend heavily on the Movement speed of the respective control member and from to moving amount of fluid and the throttling that occurs. In operation, these influences can be avoided by using the Mass inertia of the control parts or the expansion of the under Pressurized fluids (gas) are largely suppressed; at the However, the tax authorities can start if the location is appropriate Malfunctions due to insufficient pressure build-up due to strong Throttling in connection with leakage or decrease in volume, e.g. B. by condensation.

Controls that avoid the disadvantages mentioned must also be used the piston and the main control element via at least one other moving part to ensure a safe start in everyone to ensure the possible location of the moving parts. In the case exactly one other (auxiliary) tax body changes this in the When changing the stroke direction, rule its state (position) shortly before or after reversing the one that determines the working cylinder pressure Main control member and prevents this after the pressure change in the Working cylinders on a premature change of direction.

The production of such an auxiliary control member usually requires a similar effort to that of the main tax body. The object of the invention is, in particular to carry out a very small and suitable for the use of condensing fluids Reciprocating drive using only one expensive to produce slider to avoid the disadvantages mentioned. This object is achieved by those listed in the claims Features resolved.

The basic structure of the control is shown in Fig. 1.

Depending on its position, the one-piece slide 3 connects the two cylinder spaces above and below the piston 1 via the lines 30 and 31 to the inlet 5 or outlet 6 or 7 . For this purpose, it is designed in the middle area so that in its upper end position the piston is only pressurized from above, in the lower position of the slide from below and in the middle position of the slide from both sides.

At both ends of the slide there are two oppositely directed pressure surfaces 10 , 11 and 12 , 13 , only the larger two oppositely directed surfaces 10 and 13 being of the same size. Regardless of the position of the slide, each of the four pressure surfaces 10 , 11 , 12 , 13 is assigned a bore 20 , 21 , 24 , 25 in the slide housing 4 .

The piston 1 is fixedly connected to the piston rod and has, at a short distance from its two end faces, a circumferential groove 14 and 15 , which is connected via one or more check valves 17 , 18 to the adjacent end face in such a way that the working fluid flows from this end face to Groove can get.

The cylinder 2 is connected at both ends by lines 30 and 31 to the bores 22 and 23 in the valve housing, which are connected to the inlet or outlet depending on the position of the slide. There are also two larger bores 26 and 27 on the circumference of the cylinder running surface and a small bore 16 .

The two larger bores 26 and 27 are arranged so that one of them communicates with the two grooves 14 and 15 in the piston when it is in its upper and lower end positions.

The small bore 16 is arranged at the level of the upper large bore 26 so that it is covered by the lateral surface located between its grooves during the upward stroke of the piston before the lower groove 15 reaches the larger bore 26 . The small bore 16 remains covered during the reversal of the stroke direction.

The bores of the cylinder are connected to the bores of the slide housing via lines so that when the piston is in the middle position, the two opposite large pressure surfaces 10 and 13 of the slide keep them in their upper and lower end positions due to the pressure prevailing there, while the small ones Pressure areas 11 and 12 are pressurized in the opposite direction.

If the piston moves into an end position, then the non-return valves 17 , 18 and grooves 14 , 15 in the piston in connection with the large bores 26 and 27 and the lines 28 and 33 equalize the pressure on the large pressure surfaces 10 and 13 the slider on; due to the pressures acting on the small pressure surfaces 11 and 12 , the slide is moved away from its end position and the reversal of the stroke direction is initiated.

The steps in reversing the stroke direction are in following for the upper and lower end positions of the piston individually explained.

The slide is in its upper end position and the piston in the middle position, the inlet pressure acting over the line 30 to the upper piston surface and via the lines 29 and 33 to the upper small vane pressure surface 11 and the lower large slide pressure surface. 13 The lower piston surface is connected to an outlet via line 31 , as is the lower small slide pressure surface 12 . The upper large slide pressure surface 10 is also connected to an outlet via lines 28 and 31 . Due to the pressure conditions on the large pressure surfaces of the slide, it is held in its upper end position. The piston moves down.

After the lower piston outer surface has reached the lower edge of the bore 27 and has thus separated it from the lower cylinder space, the outer surface located between the grooves exposes the upper part of the bore 27 and thus connects the upper cylinder space to this bore via the upper check valve 17 . The lower groove 15 is also still connected to this bore; however, the lower check valve 18 closes due to the pressure from the upper cylinder space.

Like the lower large pressure surface 13 of the slide (via line 33 ), the upper large pressure surface 10 is now also pressurized via line 28 , so that the movement of the slide is now only from those on the small pressure surfaces 11 and 12 acting pressures is determined.

The inlet pressure prevailing over the piston acts on the upper small pressure surface via line 29 . The slider moves down.

When it has reached its central position, the lower piston surface and line 32 also apply pressure to the lower small slide pressure surface 12 via line 31 , so that the same pressure now prevails on both piston surfaces and on all four slide pressure surfaces. However, since the lower small pressure area 12 is smaller than the upper small pressure area 11 , the slide moves further downward and finally connects the upper piston area to the outlet 6 via the line 30 . This also reduces the pressure on the upper, small slide pressure surface 11 (via line 29 ) and on the lower, large slide pressure surface 13 (via line 33 ).

Via the check valve 18 located in the lower groove 15 of the piston and the line 28 , the upper large slide pressure area 10 is still connected to the inlet pressure prevailing under the piston; the upper check valve 17 is closed. The slide is now held in its lower end position due to the pressure conditions on the large pressure surfaces. The piston moves up. After the upper piston jacket surface has reached the upper edge of the bore 26 and the piston jacket surface located between the grooves has closed the small bore 16 , this middle jacket surface exposes the lower part of the bore 26 and thus connects the lower cylinder chamber to this bore via the lower check valve 18 .

The upper groove 14 is also still connected to this bore; however, the upper check valve 17 closes due to the pressure from the lower cylinder chamber.

Just as the upper large pressure surface 10 of the slide (via line 28 ), the lower large pressure surface 13 is now also pressurized via line 33 , so that the movement of the slide now only from that on the small pressure surfaces 11 and 12 acting pressures is determined. The inlet pressure prevailing under the piston acts on the lower small pressure surface 12 via the line 32 . The line 29 and the upper small pressure surface 11 are depressurized.

The slider moves up.

In order to keep the upper small pressure area 11 depressurized in the event of any leaks (e.g. in the area of the upper large pressure area 10 ), the area of the upper small pressure area is via a bore 8 that is very small compared to the other bores (Throttle) connected to the outlet 6 .

When the slide has reached its central position, pressure is also applied to the upper piston surface via line 30 , so that the same pressure now prevails on both piston surfaces and on all slide pressure surfaces with the exception of the upper small pressure surface 11 .

Since the upper small pressure surface is still depressurized, the slide moves further upward and finally connects the lower piston surface to the outlet 7 via the line 31 . The pressure on the lower small slide pressure surface 12 (via line 32 ) and on the upper large slide pressure surface 10 (via line 28 ) also decreases.

Via the check valve 17 located in the upper groove 14 of the piston and the line 33 , the lower large slide pressure area 13 is still connected to the inlet pressure prevailing over the piston; the lower check valve 18 is closed.

The slide is now due to the pressure conditions on the large Pressure areas recorded in its upper end position. The piston moves down.

The entire process is then repeated as described.

Fig. 2 shows another embodiment of the invention.

The slide differs from the design described in Fig. 1 by the arrangement of the smallest pressure surface 12 , which is in direct connection with the inlet 5 and is therefore constantly pressurized (claim 5), thereby reducing the overall height of the slide in the lower region is and the bore 24 in the valve housing is omitted.

In addition, in the lower position of the slide, the connection of the upper cylinder space to the outlet via holes 9 in the slide takes place, whereby the overall height of the slide is also reduced in the upper region.

The one-piece double-acting check valve 19 is moved from the pressure prevailing on the opposite side to the side with the lower pressure.

The mode of operation corresponds to that of the drive shown in FIG. 1. Since the slide shown there is never free from forces resulting from pressures during operation, the function is not adversely affected by the now uninterrupted application of pressure to the smallest pressure surface 12 .

To avoid unintentional slide movements when Reversal of stroke direction is a corresponding ratio of Flow resistances in the inlet or outlet and in the connections to strive between valve body and cylinder.

Claims (5)

1.Valve control for fluid-powered, flywheel-free reciprocating piston machines with exclusively pressure-actuated control elements and fixed reversal points of the working piston ( 1 ) which can be reciprocated in a cylinder ( 2 ), with a slide ( 3 ), which in its end positions has one side and in the middle position both sides of the working piston ( 1 ) is pressurized and is acted upon via lines ( 28 to 33 ) itself with the pressures prevailing in the cylinder ( 2 ) in such a way that the slide ( 3 ), when the working piston ( 1 ) is in the central position, is opposed by the pressure conditions Larger pressure surfaces ( 10 , 13 ) is held in position, while the smaller force resulting from the opposing smaller pressure surfaces ( 11 , 12 ) acts in the opposite direction, characterized by check valves ( 17 , 18 ) arranged in the working piston ( 1 ) ) which when reversing the stroke direction Connect the introduction of the larger pressure surface ( 10 , 13 ) of the slide ( 3 ), which is pressurized, via bores ( 26 , 27 ) in the cylinder ( 2 ) at least as long as the greater of the pressures prevailing in the cylinder ( 2 ) until the reversal of the stroke direction is complete . 2. Valve control according to claim 1, characterized by a bore ( 16 ) in the cylinder ( 2 ) which is connected to the control chamber associated with a smaller pressure surface ( 11 ) of the slide ( 3 ) and is closed by the working piston ( 1 ) during the reversal of the direction of travel. 3. Valve control according to claims 1 or 2, characterized by a slide ( 3 ) with two differently smaller pressure areas ( 11 , 12 ). 4. Valve control according to claims 2 or 3, characterized by a throttle ( 8 ) which is arranged between the control chamber associated with a smaller pressure surface ( 11 ) of the slide ( 3 ) and the outlet ( 6 ). 5. Valve control according to one of claims 2 to 4, characterized in that the smallest pressure surface ( 12 ) of the slide ( 3 ) is constantly pressurized.