DE2750199C2 - Relief valve for positive displacement blower driven by a three-phase electric motor - Google Patents

Description

The invention relates to a relief valve with at least one outlet opening for blowing off Compressed air in a rotary piston blower driven by a three-phase electric motor during the Motor start-up phase in the star connection, with the electric motor in the delta connection after the start-up phase switched and the relief valve is closed, with a wall part of a pressure chamber forming gas-tight, movable membrane, which is under the action of a spring and with a valve closing member is connected, the main part of which is a valve disk, the valve when it is reached a predetermined pressure are closed in that pressure space as a result of the movement of the membrane.

A relief valve of this type is already known from DE-AS 12 00 469, in context with a device for relieved start-up of an air compressor system. The starting behavior of the three-phase electric motor, where first the star connection is used and then the motor is used in the delta connection is switched, special consideration must be given. Care must be taken that the electric motor is not loaded during the start-up phase in the star connection so that it actually reaches its operating speed can reach. Otherwise the engine will suddenly accelerate to the operating speed at the transition to the delta connection. In connection with that of the three-phase electric motor driven positive displacement compressor or blower, this means that the compressed air during the start-up phase must be blown off into the open, otherwise the existing pressure is during the start-up phase so great that the operating speed is not reached.

The well-known relief valve is part of a device for the relieved start-up of a positive displacement compressor, with the one container via a line with

a check valve is to be supplied with air. The relief valve is on in an upright position connected to the pressure line piece leading from an oil separator to the container, with compressed air on the The valve stem of the valve disk passes into the pressure chamber located below the membrane, whereby the membrane is pressurized. When the compressor has almost reached its operating speed, is a pressure built up so high that the diaphragm moves by the movement generated by the diaphragm not only the valve is closed, but also the star-delta connection of the three-phase electric motor operated directly. In addition, the functionality of the known relief valve with an additional Vent valve matched, which is the line through which the container is filled with air, vented when the pressure in the container is a desired one Has reached value

Due to the venting in the line, the well-known relief valve opens, causing the star-delta switch is operated again, so that the three-phase electric motor is then back in the star connection for the next start-up phase. B, for which the invention Relief valve should be particularly suitable, but is a premature opening of the relief valve not wanted

In another known compressor arrangement according to US-PS 1690 304 is on an air compressor with a controller, a controlled switch is provided, which switches off a compressor motor when in A certain pressure has been reached in a container to be filled. The compressor arrangement also includes a Relief valve with one under the action of one Spring standing diaphragm. By this spring, the membrane is brought into such a position that the feed is in communication with the atmosphere from the compressor to the container. The compressor can thus start unloaded when the controlled switch switches on the motor.

With increasing pressure acting on the membrane, the latter is moved against the force of the spring and thereby the mentioned connection to the atmosphere is cut off. The compressor is thus started relieved and can now fill the container with air. A changeover from a star connection in the delta connection, as provided in the invention, does not take place here.

Finally, there is a compressor system with a three-phase motor and star-delta switch according to DE-AS 11 25 523 to be observed in the case of one of a check valve operated vent valve is provided. The system has a pressure switch, which the Compressor switches on and off automatically depending on the pressure in an air tank.

So if the pressure in the air tank falls below a certain minimum value, the motor will switched on by the pressure monitor, and the motor starts up in the star connection and drives the compressor. The small amount of air conveyed into the supply line to the air tank escapes through the open vent valve. If the correct speed at which the switchover can take place has been reached, the pressure is also in the mentioned supply line high enough to operate the star-delta switch, so that now the changeover takes place in the delta connection. Now the speed continues to increase and the check valve is from Pressure opened, at the same time the vent valve closes. The motor is restored via the pressure switch switched off when the pressure in the air tank is sufficient is high. The check valve returns to its seat and at the same time opens the vent valve.

The supply line to the air tank is vented, and the star-delta switch returns to its star switching position.

The arrangement for relieved start-up in this known compressor system is mechanically complex and hardly suitable for the purpose aimed at by the invention.

The invention is based on the object of designing a relief valve of the type mentioned at the outset in such a way that that for the relieved start of a three-phase electric motor driven rotary piston blower in the start-up phase a minimum of moving parts is required to achieve a low susceptibility to failure. The relief valve should largely be maintenance-free and allow a specific valve closing time to ensure safe valve closing after the start-up phase Ensure switching from star connection to delta connection.

To solve this problem, the prerequisite in the preamble of claim 1 is provided for a relief valve Art proposed according to the invention that a number of adjustable in width outlet openings is provided for the compressed air flowing through under the valve disk to prevent a pressure increase in the To enable valve feed, and the latter and the pressure chamber both when it is open and when it is closed Relief valve are in communication with one another via a throttle which is dimensioned so that the time to fill the pressure chamber after the start of the electric motor and thus to respond to the Diaphragm and to close the relief valve takes longer than the start-up phase of the electric motor in the control circuit.

After commissioning the three-phase electric motor and thus the rotary piston blower, the Modified air escape in the desired manner first through the outlet openings. At the same time it builds up within of the pressure chamber, because the latter is connected to the valve feed line via a throttle stands. From the point of view of the effect, it is

<t5 sam a timer before which the relief valve closes after a certain period of time. This period of time is chosen so long that the expiry phase of the Electric motor is already over before the relief valve then closes. Even then, however, the pressure room is in place still in connection with the valve feed line, so that the relief valve is actually also in the closed position remains.

The time to fill the pressure space and thus until the pressure rises to a specified value which causes the diaphragm to move and the relief valve to close, hangs from the throttle mentioned and from the width of the adjustable outlet openings. By reducing the The width of the outlet openings results, for example

bo a relatively large pressure gradient at the throttle and thus a short filling time of the pressure chamber. So it is easily possible to measure the time to close the relief valve to regulate so that this time lasts longer than the start-up phase of the electric motor in the

b5 star connection. However, it is important to ensure that the pressure built up by the throttling remains so low that the electric motor reaches its operating speed the star connection actually achieved. try

5 6

have shown that at a pressure of about a different design than in FIG. 4th Third of the operating pressure, the operating speed is always in F i g. 1 is a compressor unit, for example is achieved safely. If the necessary throttling for the ventilation system of a sewage treatment plant is shown, a significantly higher pressure to achieve a de- The compressed air for ventilation is achieved with the help of a rotary speaker Requires filling time, a throttle 5 piston blower 1 generated by an electric motor use with a larger opening. 2 can also be driven via a belt. The Drehkoldie Outlet openings are enlarged. Bengebläse 1 is a muffler 4 and an air filter 6

In order to achieve the effective width of the upstream and downstream silencer 8 To be able to adjust outlet openings, these are switched in. From the latter muffler 8 arrives Further development of the invention by a number of 10 compressed air in the pressure line 10, whereby for unforeseen

from fixed outlet slots in one of the valve congestions within the pressure line 10

The cylindrical valve housing part surrounding the plate and the pressure relief valve 12 and for the start-up phase of the elec-

an equal number of the stationary tromotors 2, a relief valve 14 is provided. As

equal-sized outlet slots in each valve section from the dashed line on the right-hand side

housing part rotatable surrounding ring slide formed 15 of Fig. 1 can be seen, the position of the respective

det, which overlap each other more or less, with aggregates to each other freely selectable, if they only the

A min function can be used accordingly between adjacent outlet slots. To avoid

at least about the same width uninterrupted flow of backflows through the compressor unit

The wall area of the valve housing part or the ring gate, especially during standstill, is generally

slide is present. 20 mean a non-return valve 16 in the pressure line

For safety reasons, each ventilation system has device 10 inserted, which in particular has a return flow

a pressure relief valve to prevent liquids, i.e. foreign matter, in the event of a build-up inside

half of the pipeline system with the associated should.

Pressure increase above a predetermined value in the outer In F i g. 2 is the relief valve 14 in a sectional

In the first case, the total delivery rate of the rotary piston drawing is shown in a first exemplary embodiment.

blow it off. According to a further development of the provides. Within a valve housing part 18 is a valve

Invention is housed in the pressure chamber of the relief valve tilsiiz 20, the sealing surface with a

connected to a safety valve with which is provided with rubber 22 under rubber. Opposite the valve seat

Pressurized compressed air against the force of a 20 is a valve closing element 24 with a valve disk 26 Closing spring can flow out directly into the ambient air 30, which is in the open position of the valve

can. This means that after the safety device has been opened, an opening 25 is released. The valve disk 26 is on one

valve attached as a result of the exceeded maximum pressure valve stem 28, which is inside a sleeve 30

the pressure in the pressure chamber collapses, which is axially displaceable.

on the valve body of the relief valve of the At the upper end of the valve stem 28 is a mem-

The valve seat is fastened as a result of the spring 32 acting in this direction, which with the help of membrane disks

which lifts off metal 34, 35 is supported. The membrane 32 forms the

But there is still another embodiment of the safety lower part of the wall of a pressure chamber 36, which is connected to safety valve possible, in the case of which a side of an upper part 38 of a diaphragm safety valve is attached to the pressure chamber is connected, in which the upper housing 42 is limited. One with the top 38 Pressurized compressed air via a piston valve in 40 screwed lower part 40 of the diaphragm housing 42 is the ambient air is discharged, which is opposite to that attached to the top of the valve housing part 18 Force of a spring is actuated by a piston, des- With the help of a spring 44, which is between the diaphragm effective piston area via one of the valve pusher 35 and a partition 46 above the valve line discharging control line acts with compressed air pressure plate 26, the relief valve 14 is knocked out at 45 switched! Rotary lobe blower 1 is always open

Because the relief valve will hold the flow of the. In the valve feed line 15 (see also Fig. 1) the rotary piston blower is blown off without difficulty then normal ambient pressure is present, which is also capable of the safety valve relative to the discharge within the pressure chamber 36 prevails, the diestungsventil being kept small without the risk of water there is a throttle 48 inside the hollow valve that, because of the small cross-section, a shaft 2tl with the valve feed line 15 is connected to a further increase in pressure within the line system
takes place when switching on the electric motor 2 and thus

Other advantageous developments of the invention occur when the rotary piston blower 1 is started up

are also specified in the subclaims. Part of the flow into the valve feed line 15 and

In the following, the invention is illustrated by several then through the opening 25 of the relief valve 14 and

Ren embodiments based on the drawing in more detail about adjustable outlet openings 49 into the open. In the

explained; it shows the valve housing part 18 arranged outlet slots

F i g. 1 in a schematic representation of a compressor 50 can with the help of a valve at this point

unit, housing surrounding ring slide 52 with the same

F i g. 2 is a longitudinal section through a relief valve 60 let slots 50 'narrowed by rotation, so

with the features of the invention that practically a throttle is created The ring slide,

F i g. 3A and B each show a cross section along the way in which it functions particularly well in FIG. 3A and 3B Line IH-III in FIG. 2, can be seen, is now set so that in the valve F i g. 4 shows a longitudinal section through the relief valve supply line 15, a pressure is created which is thus above the

according to Figure 2 with an additional safety valve 65 predetermined pressure gradient at the throttle 48 in the

and valve stem 28 at a filling time of the pressure chamber 36 bis

F i g. 5 shows a longitudinal section through the relief valve for the response of the diaphragm 32, which is longer appropriately F i g. 2 with an additional safety valve lasts as; the start-up phase of the positive displacement blower.

If in the first setting, which should be only a slight throttling, the filling time and thus the time to close the valve significantly exceeds the start-up phase, the throttling is increased until a Closing time of the relief valve has been reached, which is only just above the start-up phase.

When the throttling caused by the outlet openings 49 becomes so strong that when switching over from the star to the delta connection a sudden load on the electric motor 2 due to excessive Load occurs in the star connection, the throttling must be withdrawn. The thereby lengthened Closing time can then be shortened again by installing a throttle 48 with a larger opening, The fine adjustment of the shooting point is carried out by means of the ring slide 52. The final setting of the Ring slide 52 is fixed and secured with the aid of a clamping screw 53 and a lock nut.

The position of the ring slide shown in Figure 3A 52, in which all of the outlet slots 50 are separated from the wall areas between the outlet slots 50 ' are covered, does not occur in practice, but the representation is only for illustration the ring slide principle has been chosen. The in F i g. 3B position of the ring slide 52, in each of the outlet slots 50 and 50 'are congruent one above the other, is either the starting position before the setting or already the setting itself, if z. B. a particularly small relief valve 14 is used for a high-performance system in which the full opening of the outlet openings 49 is straight leads to a corresponding closing time at a sufficiently low dynamic pressure.

When the predetermined pressure is reached within the pressure chamber 36, the membrane 32 is against the Action of the spring 44 pressed down until the valve disk 26 rests on the valve seat 20 As the space is in communication with the environment below the membrane 32 via holes 55, which acts on the membrane acting force from the pressure chamber 36 always only against the spring 44. After the opening 25 is closed in the valve supply line 15 and thus within the pressure line 10, the operating pressure which is essential is higher than the closing pressure within the pressure chamber 36, so that the relief valve 14 is now automatically is kept closed with great certainty. This applies until the pressure inside the pressure line 10 drops by switching off the electric motor 2 to the ambient pressure. The relief valve opens shortly beforehand 14 as a result of the decreasing pressure within the pressure chamber 36 and then effective nascent spring 44.

In the embodiment according to FIG. 4 is on the pressure chamber 36 is connected to a safety valve 54, which according to the on the associated valve plate 56 acting pressure is opened. When exceeded of the safety pressure, the air enclosed in the pressure chamber escapes through openings 58 ins Free. The bias of the valve disk 56 is applied with the aid of a spring 60, the upper a stamp 62 acts on the valve disk and can be adjusted with the aid of an adjusting plate 63.

Through the safety valve 54 the in FIG. 1 schematically illustrated overpressure valve 12 under the Condition can be saved that the cross-sectional area of its outflow is greater than the cross-sectional area the throttle 48. Then it takes over together with the relief valve 14 the function of Overpressure valve 12. Namely at the moment in which the safety valve 54 as a result of an overpressure is pushed open, the pressure in the pressure chamber 36 breaks despite the compressed air flowing in through the throttle 48 together so that the spring 44 opens the relief valve. The safety valve 54 thus acts as a pilot valve, that only blows off a small amount of compressed air; the actual blow-off volume escapes through the outlet openings 49 with the relief valve open. (In ία Fig. 4 only all those components are given a reference number provided, which are related to the function of the safety valve 54; Furthermore it is the same construction as in Fig. 2).

5 is a safety valve 54 'of a different design connected to the pressure chamber 36. In this case, the opening of the safety valve 54 'is not influenced by the pressure determined within the pressure chamber 36, but the safety valve has its own control line 70, which is completely separated from the outflow path via the opening 58. The control line 70 is at its lower End connected to the valve supply line 15 and leads upwards into a valve housing 68 in which a piston 66 is arranged displaceably, the pressure prevailing in the valve feed line 15 then acting on this piston 66 works. When the safety pressure is reached, the piston 66 is in the housing 68 against the action of a Spring 60 'is pressed to the left, a piston slide 64 being moved via a piston rod until the opening 58 is in communication with the pressure chamber 36.

The safety valve design according to Fig. 5 has the advantage over that of Figure 4 that the Pressure for opening the safety valve 54 'is not influenced by the throttle 48. Rather, the safety valve remains 54 'according to FIG. 5 is open as long as the safety pressure within the valve feed line 15 is exceeded. In the embodiment according to FIG. 4 it can happen that after a first open of the safety valve 54 and an initial opening of the relief valve 14, the safety valve again for a short moment a corresponding amount of compressed air closes through the throttle 48 must flow. This phenomenon is basically not harmful, since the purpose of the arrangement is straightforward is achieved. The solution according to FIG. 5 is more consistent in its training, but also somewhat more elaborate. Here too, the cross-sectional area of the throttle 48 must be used for the pressure drop in the pressure chamber 36 be smaller than that of the Sicherheitsabströmweges, so it must be ensured that the opening 25 within of the valve seat 20 is large compared to the Ausiaßoftnungen 49, so not between the valve seat 20 and the valve disk 26 already acts a throttling, which leads to too low a pressure at the lower end of the hollow Valve stem 28 leads If this condition cannot be met with certainty, it is advisable to to extend the stem 28 downward beyond the valve seat 20.

The throttle shown in the exemplary embodiments 48 the desired valve closing time can be achieved by exchanging the diaphragm for one with a different opening be adjusted. As a rule, however, the choice of a single throttle is sufficient, with the The relief valve 14 is coordinated with the aid of the ring slide 52.

For this purpose 3 sheets of drawings

Claims (9)

Patent claims: 1. Relief valve with at least one outlet opening for blowing off compressed air at a s Rotary piston blower driven by a three-phase electric motor during the engine start-up phase in the star connection, whereby the electric motor switches to the delta connection after the start-up phase and the relief valve is closed, with one forming a wall part of a pressure space gastight movable membrane which is under the action of a spring and with a valve closing element is connected, the main part of which is a valve head, the valve being calibrated at En predetermined pressure in each pressure chamber is closed as a result of the movement of the membrane, characterized in that a number of outlet openings which are adjustable in their width (49) for the flowing through under the valve disk (26) Compressed air is provided to enable a pressure increase in the valve supply line (15), and that the latter and the pressure chamber (36) both when the relief valve is open and when it is closed (14) or a throttle (48) are in communication with each other, which is dimensioned so that the time to Filling of the pressure chamber (36) after the start of the electric motor (2) and thus to respond the membrane (32) and to close the relief valve (14) takes longer than the start-up phase of the electric motor (2) in the star connection. 2. Valve according to claim 1, characterized in that the adjustable outlet openings (49) by a number of fixed outlet slits (50) in a valve plate (26) surrounding j ¹ »cylindrical valve housing part (18) and an equal number of the fixed (50) equal-sized outlet slots (SO ') are formed in an annular slide (52) which rotatably surrounds that valve housing part (18) and more or less overlap each other, with an at least approximately equally wide uninterrupted wall area between adjacent outlet slots (50.50') Valve housing part (18) or the ring slide (52) is present. 3. Valve according to one of claims 1 or 2, characterized in that the through the adjustable Outlet openings (49) given passage for the compressed air is always smaller than the opening (25) of the Relief valve (14) is. 4. Valve according to one of claims 1 to 3, characterized in that the valve closing member (24) includes a longitudinally pierced valve stem (28) which is connected at one end part to the valve head (26) is and at the other end of the membrane (32) between two membrane plates (34,35) is attached to its inner edge, the connection between the pressure chamber (36) and the valve supply line (15) is made through the longitudinal bore of the valve stem (28). 5. Valve according to one of claims 1 to 4, characterized in that the throttle (48) in the form a diaphragm is arranged interchangeably in the longitudinal bore of the valve shaft (28). 6. Valve according to one of claims 1 to 5, da- b5 characterized in that the valve stem (28) in an upright arrangement of the valve in an above of the outlet openings (49) located partition (46) of the valve housing (18,38,40) mounted displaceably is that the valve seat (20) is arranged at the lower end of the outlet openings (43). the The valve plate (26) is in the full opening position in the upper area of the outlet openings and dtß nevertheless the lower opening of the longitudinal bore of the valve stem (28) as close as possible in the area of the valve seat (20) is located 7. Valve according to one of claims 1 to 6, characterized in that the on the membrane (32) acting spring (44) between the membrane (32) or a lower membrane plate (35) and the Partition wall (46) is arranged and supported 8. Valve according to one of claims 1 to 7, characterized in that the pressure chamber (36) a safety valve (54) is connected, with the pressurized compressed air against the Force of a closing spring (60) can flow out directly into the ambient air (Fig. 4). 9. Valve according to one of claims 1 to 8, characterized in that the pressure chamber (36) a safety valve (54 ') is connected, in which pressurized compressed air via a Piston valve (64) is diverted into the ambient air, counter to the force of a spring (60 ') is actuated by a piston (66), the effective piston surface of which via one of the valve feed line (15) discharging control gas line (70) is pressurized with compressed air (FIG. 5).