PNEUMATIC DIAPHRAGM VALVE PULSATOR

Abstract: The pulsator comprises a housing (10, 11) with a diaphragm (12) clamped therein, which engages at one side thereof a seat (15) between an inlet compartment (16) and an outlet compartment (18) for pressurized gas. At the other side of the diaphragm there is a back pressure compartment (20) in the housing. The back pressure compartment has a choked connection with the inlet compartment (connection 21; 33, 34) as well as the outlet compartment (connection 22, 24, 25). In said latter connection (23) a shut-off valve (23) is provided.

Description: PNEUMATIC DIAPHRAGM VALVE PULSATOR The invention relates to a pneumatic diaphragm valve pulsator comprising a housing and a diaphragm clamped therein, which engages at one side thereof an annular seat between an inlet compartment and an outlet compartment for pressurized gas, said compart¬ ments being defined in the housing at said one side of the diaphragm while a back pressure compartment is defined in the housing at the other side of the diaphragm. The invention has been particularly devised for such diaphragm valve pulsators which are used for activating dust and pulverulent material by means of powerful high-speed pulses in the frequency range from 0 to 50 Hz. Frequencies within this range in the infrasound range (from 0 to 20 Hz) as well as the audible range (from 20 to 50 Hz) are used e.g. in fiuidizing pulverulent material and in cleaning steam boilers, hot-water boilers, electro-f lters, etc. It is known to provide in pneumatic diaphragm valve pulsators of the type referred to above an aperture in the diaphragm between the back pressure compartment and the outlet compartment, the frequency of the pulsator being dependent on the size of the aperture. The greater the aperture, the higher the pulsator frequency. A drawback of such an aperture is that so-called critical flow can arise through the aperture and that the operation of the pulsator can be jeopardized as a consequence thereof. It is also previously known to provide in diaphragm valve sirenes with a resonance horn a connection between the back pressure compartment and the inlet compartment either as an aperture in the diaphragm or as a connection passage, possibly adjust- OMPI . WIPO , able, in the housing. This connection in that case is used not for controlling the frequency of the sirene, which is determined by the resonance oscillation in the resonance horn, but is provided for adjusting the gas pressure in the back pressure compartment to such a value lower than the gas pressure in the inlet compartment that the diaphragm oscillates stably with a suitable amplitude in pace with the resonance oscillation in the resonance horn. Finally, for controlling diaphragm sirenes at signalling it is also previously known to provide a valve for relieving the pressure in the back pressure compartment by connecting said compartment to the sur¬ roundings via this valve; this provides the advantage that the control valve can have small dimensions. The purpose of the. invention is to make possible a stepless frequency control in a diaphragm valve pulsator of the type referred to above while maintain¬ ing a stable pulsation and a reliable operation within the entire frequency range of the pulsator. For this purpose the pulsator according to the invention has obtained the characteristics appearing from claim 1. By this arrangement the connection between the inlet compartment and the back pressure compartment provides balance in the back pressure compartment particularly at high-speed pulses. Thereby the pulsator provides a more stable pulsation than known pulsators of the type referred to above and at the same time the frequency can be adjusted continuously by controlling the connection between the outlet compartment and the back pressure compartment without the influence by external means. Two embodiments of the invention will be described in more detail below, reference being made to the accompanying drawings in which FIG. 1 is an axial cross-sectional view, partly a side view, of a pneumatic diaphragm valve pulsator according to one embodiment of the invent on, FIG. 2 is a view corresponding to that in FIG. 1 , which illustrates the functional condition when the pulsator is shut-off, FIG. 3 is a view corresponding to that in FIG. 1 illustrating the functional condition when the pulsator is operating, and FIG. 4 is a view corresponding to that in FIG. 1 of another embodiment of the diaphragm valve pulsator according to the invention. The diaphragm valve pulsator according to FIG. 1 comprises a housing which consists of a cylindrical cup-shaped bottom part 10 and a cover 11. Between the parts 10 and 11 a diaphragm 12 located in the housing is clamped at the periphery thereof between 0-rings 13 received by annular grooves in the bottom part 10 and the cover 11, respectively. Thus, the diaphragm is elastically clamped. Centrally in the bottom part 10 there is provided an annular seat 15 which is normally sealingly engaged by the diaphragm 12, and inside this annular seat the bottom part 10 forms an inlet compartment 15 having an inlet 17 to be connected to a conduit for the supply of pressurized gas, while the bottom part forms around the seat 15 an annular outlet compartment 18 having an outlet opening 19 to be connected to a conduit for supplying pulses from the pulsator. At the other side of the diaphragm, which is opposite to the annular seat 15, a back pressure com¬ partment 20 is provided between the diaphragm and the cover 11, said back pressure compartment permanently communicating with the inlet compartment 16 through a small aperture 21 which is formed centrally in the diaphragm 12. The back pressure compartment 20 is also connected to the outlet compartment 18 but through a valve-controlled connection. This valve-controlled connection comprises a passage 22 in ' the cover 11, which is connected to a solenoid valve 23 mounted on top of the cover, a passage 24 also formed in the cover 11 and connected to the solenoid valve 23, and a passage 25 formed in the bottom part 10 as an extension of the passage 24. The passage 25 communicates with the outlet compart¬ ment 18. The valve member 26 of the solenoid valve 23 keeps the connection between the passages 22 and 24 closed when the solenoid valve is de-energized, such connection consequently being open when the solenoid valve is energized. « While the solenoid valve 23 thus keeps the connection between the back pressure compartment 20 and the outlet compartment 18 open or closed depending on the solenoid valve 23 being energized or de-energ zed, there is a control valve for adjusting the magnitude of the flow which can pass through the connection 22, 24, 25 when the solenoid valve 23 is energized and thus is in open position. This valve comprises a socket 27 connected by welding to the bottom part 10, and a con¬ trol screw 28 having a control tip 29 is screwed there¬ into, a sealing packing box 30 being provided around the screw 28. By screwing the screw 28 more or less into the passage 25 the flow through the connection between the back pressure compartment 20 and the out¬ let compartment 18 can be choked more or less. The functional condition of the diaphragm valve pulsator when the pulsator is out of operation and accordingly no pulses are supplied from the pulsator, ■^ gυ E OMP A WIP is illustrated in FIG. 2. In this functional con¬ dition the solenoid valve 23 is de-energized and accordingly the valve member 26 thereof keeps the connection ' between the back pressure compartment 20 and the outlet compartment 18 closed. A conduit 31 for pressurized gas, usually pressurized air, is connected to the inlet 17 such that not only the inlet compartment 16 but also the back pressure compartment 20 is pressurized, because there is a connection between these two compartments through the aperture 21. Since the pressure area of the diaphragm 12 in the back pressure compartment 20 is larger than the pressure area of the diaphragm in the inlet compartment 16 the diaphragm is held pressed against the annular seat 15 and the outlet compartment 18 thus is. separated from the inlet com¬ partment 16 by means of the diaphragm. Now, if the solenoid valve is energized, the functional condition in FIG. 3 will be obtained. In this case the valve member 26 keeps the connection between the back pressure compartment 20 and the outlet compartment 18 open through the passages 22, 24, 25 via the choke valve 29, which means that the pressure in the back pressure compartment 20 will be relieved by pressurized gas escaping from this compart¬ ment to the outlet compartment 18. As a consequence thereof the diaphragm 12 will be lifted from the seat 15 by the pressure at the lower side of the diaphragm such that pressurized gas can flow from the inlet compartment 16 to the outlet compartment 18 and to the outside therefrom through a conduit 32 connected to the outlet 19. When the pressure in the back pressure compart¬ ment 20 has increased again sufficiently due to the connection through the aperture 21 in order that the diaphragm 12 shall again be pressed against the seat 15 thereof, the connection between the inlet compart¬ ment 16 and the.outlet compartment 18 will again be closed to be opened again later when the pressure in the back pressure compartment has been relieved through the connection 22, 24, 25. Thus, the diaphragm 12 will open and close the connection between the inlet compart¬ ment 16 and the outlet compartment 18 at a predetermined frequency for the supply of pressurized gas pulses at that frequency through the conduit 32 as long as the solenoid valve 23 is energized and the valve member 26 is maintained in the open position. The function of the inlet compartment 16 is to store the pressurized gas as close as possible to the outlet 19, pressure drop over the seat 15 when a pulse is supplied being eliminated thereby, while the function of the outlet compartment 18 is to provide a flow of the pressurized gas which is as free and pressure-reducing as possible. The choke valve 29 forms a member for stepless control of the frequency at which the diaphragm 12 opens and closes the connection between the inlet compartment 16 and the outlet compartment 18, and thus the frequency at which pressurized gas pulses are supplied from the pulsator. The more open the choke valve 29 is, the higher will the frequency be. However, the pressurized gas in the back pressure compartment 20 is also matched to the desired pulse frequency and some replenishment with pressurized gas to the back pressure compartment through the passages 22, 24, 25 is obtained until the pressure required in order that the diaphragm shall close against the seat 15, has been obtained. Thus, it should be observed that the aperture 21 in the pneumatic diaphragm valve pulsator according to the invention is not used for controlling the frequency of the pulsator. This aperture is used to provide balance in the back pressure compartment 20 particularly at high-speed pulses, which means that a more stable pulsation is obtained in the pulsator as compared with conventional pneumatic diaphragm valve pulsators. Since the solenoid valve 23 which is used to start and stop the pulsator, does not necessarily operate with the total drive gas flow of the pulsator but only with the negligible flow between the back pressure compartment 20 and the outlet compartment 18, this valve can be of a relatively tiny embodiment, which involves an important advantage as to economy. By means of the solenoid valve 23 the pulsator is started and stopped quickly and distinctly. In the embodiment according to FIG. 4 the aperture 21 in the diaphragm 12 is replaced by a valve-controlled connection between the inlet 17 (inlet compartment 16) and the back pressure compart¬ ment 20. This connection comprises a passage 33 in the bottom part 10 and a passage 34 in the cover 11, commun cating therewith. The choke valve is of the same embodiment as the valve provided for controlling the flow through the connection 22, 24, 25 and has been designated generally with 35. In this embodiment of the pneumatic diaphragm valve pulsator there are greater poss bilities of stabilizing the operation of the pulsator within -the frequency range thereof. For high-speed pulses the choke valve 35 is adjusted to' a slightly open position such that the pressure in the back pressure compartment 20 is maintained continuously by the supply of pressurized gas from the inlet com¬ partment 16. However, the frequency is adjusted in the same manner as described earlier by adjustment of the O PI valve 29. For low-speed pulses the connection 33, 34 is choked by means of the valve 35, the connection 22, 24, 25 at the same time being choked in order to adjust the pulsator to a lower frequency, and as a consequence thereof the pressurized gas in the back pressure compartment 20 will be replenished very slowly.

Claims: CLAIMS 1. Pneumatic diaphragm valve pulsator comprising a housing (10, 11) and a diaphragm (12) clamped there¬ in, which engages at one side thereof an annular seat (15) between an inlet compartment (16) and an outlet compartment (18) for pressurized gas, said compart¬ ments being defined in the housing at said one side of the diaphragm while a back pressure compartment (20) is defined in the housing at the other side of the diaphragm, c h a r a c t e i z e d by a con¬ tinuously open choked connection (21; 33, 34) between the back pressure compartment (20) and the inlet com¬ partment (16), and by a choked connection (22, 24, 25) open during operation of the pulsator, preferably via a shut-off valve (23), between the back pressure com¬ partment (20) and the outlet compartment (18). 2. Pneumatic diaphragm valve pulsator according to claim 1, c h a r a c t e r i z e d in that the choked connection between the back pressure compart- ment (20) and the inlet compartment (16) comprises an aperture (21) in the diaphragm (12). 3. Pneumatic diaphragm valve pulsator according to claim 1, c h a r a c t e r i z e d in that the choked connection between the back pressure compart- ment (20) and the inlet compartment (16) comprises, a passage (33, 34) in the housing (10, 11). 4. Pneumatic diaphragm valve pulsator according to cla m 3, c h a r a c t e r i z e d in that the passage (33, 34) is provided with an adjustable choke valve (35). 5. Pneumatic diaphragm valve pulsator according to any of claims 1 to 4, c h a r a c t e r ! " z e d in that the choked connection between the back pressure compartment (20) and the outlet compartment (18) comprises a passage (22, 24, 25) in the housing. 6. Pneumatic diaphragm valve pulsator according to claim 5, c h a a c e i z e d in that the passage (22, 24, 25) between the back pressure compart¬ ment (20) and the outlet compartment (18) is provided with an adjustable choke valve (29). 7. Pneumatic diaphragm valve pulsator according to any of claims 1 to 6, c h a r a c t e r i z e d in that the shut-off valve comprises a solenoid valve (23). 8. Pneumatic diaphragm valve pulsator according to any of claims 1 to 7, c h a r a c t e r i z e d in that the inlet compartment (16) is arranged centrally inside the seat (15), the outlet compartment (18) being arranged annularly around the seat.

Inventors: NILSSON C
Applicants: KOCKUMATION AB, NILSSON C
Application year: 1980
Main classification: B06B1
IPC codes: B06B1, F15B21, F16K31, G10K9