EP1801417A1 - Diaphragm membrane pump with compensating mechanism to avoid overload of diaphragm - Google Patents

Abstract

The pump has a hydraulic control chamber disposed between a piston (8) and a diaphragm (3). A chamber leak compensating unit has a refilling duct (14) opening out into the chamber via a valve (15). The valve is driven by pressing the diaphragm against a free end (16a) of a rod (16) to control the valve. The diaphragm is subjected to a force of a suction-assistance spring (13), which co-operates with the valve to return the valve to closed position. The spring co-operates with the valve to form a moving assembly that is moved without being deformed by the diaphragm during suction over travel.

Description

The present invention relates to a hydraulically actuated diaphragm pump with membrane protection in case of hydraulic leaks in the actuating chamber.

BACKGROUND OF THE INVENTION

Overtravel suction is due to a deficit of liquid in the hydraulic chamber actuating the membrane. In reality, in certain types of pumps, this overtravel does not occur because the membrane at the end of suction is supported on a limiting surface of the stroke. It can then occur cavitations in the hydraulic chamber, and, in any case, the displacement of the pump is affected downward. In some pumps where there are no mechanical limitations to the suction stroke of the diaphragm, overtravel, in addition to the weakening of performance, can result in excessive membrane deformation and fatigue to longevity .

An overtravel to the discharge is due to an excess of liquid in the hydraulic chamber of actuation of the membrane. This situation occurs for example when the pump is in prolonged stop while a depression is installed in the working chamber. The hydraulic control chamber sees its volume increase little by little, filled by the fluid from the tank by capillary channels resulting from mechanical play of operation. At the next start, the membrane may tear.

These phenomena are well known and there are many devices to remedy them. Pumps that have a plate or a rear support grid of the membrane and a one-way valve of the calibrated feed, which opens when a vacuum threshold is reached in the hydraulic chamber. If this threshold is important, the relaxation of the chamber oil hydraulic is too important and flow stability is affected. There is also a peak vacuum at the beginning of the suction phase due to the inertia of moving elements and premature opening of the calibrated valve which leads to overcompensation harmful to the discharge.

The document FR 2,557,928 includes means for compensating leaks that are automatic given the very principle of operation of the pump. This system is also subject to overcompensation.

We will also mention the document EP 547 404 . The device described implements valves whose opening or closing is associated with a position reached by the membrane.

Thus, to suppress the overtravel of discharge, a valve interrupts the communication between two parts of the hydraulic chamber thus isolating the fluid in contact with the membrane of the fluid in contact with the piston when the membrane has reached a set position at the end of discharge. The excess operating fluid is then diverted to a tarpaulin through a relief valve.

Similarly, to remove a suction overtravel, a valve opens at the moment when the membrane reaches a set position suction end. This opening communicates the hydraulic chamber with an oil tank by a feedback line and a complementary movement of the piston causes the suction of a volume of compensation oil in the hydraulic chamber.

With regard to the diaphragm controlled or controlled compensation valve, it is necessary to change its state, that the membrane develops a force intended to overcome the opposite force of a spring which maintains the valve in its state shutter feedback line. This effort to overcome limits the suction height of the pump. In other words, in the case of operation of the pump with vacuum at the suction, it may occur a non-operation of the compensation device, a cavitation then taking place in the hydraulic actuating chamber without the opening of the valve can intervene. It is understood that there is great interest in reducing the force of the return spring of the valve on its seat to not penalize too much the operation of the pump suction. But it is hardly possible to reduce this force below a value corresponding to a pressure of 0.3 bars (3 meters of water column or 300 hectopascals).

Diaphragm pumps equipped with a membrane-controlled leak compensation system therefore have poor suction power.

OBJECT OF THE INVENTION

The present invention relates to a pump in which the compensation of leakage of the hydraulic chamber is controlled and the suction power significantly improved.

BRIEF DESCRIPTION OF THE INVENTION

The invention therefore relates to a diaphragm pump comprising, in a body, a hydraulic control chamber disposed between a reciprocating piston and the diaphragm, the pump comprising means for compensating for leaks in the hydraulic chamber with a feedthrough opening into the hydraulic chamber through a compensation shutter controlled at the opening by the membrane.

According to a main feature of the invention, the aforementioned compensation shutter is operated by pressing the membrane on a free end of a rod of its control while the membrane is subjected the force of a suction assist spring which cooperates with the aforementioned shutter to return it to its closed state by pushing the free end of the rod towards the diaphragm, this spring forming with the shutter a moving equipment moved without being deformed by the membrane during a suction overtravel.

The suction assistance spring is supported, opposite the shutter, on a shoulder located at the end of a rod integral with the membrane and extending from it in the hydraulic chamber of the pump.

This particular arrangement has the advantage of freeing the opening of the compensation shutter of any effort that is necessary to maintain it in its closed state. This increases the suction height which becomes close to ten meters of water column against seven meters usually. The shutter and the shoulder move along a direction which is that of the deflection of the membrane.

In operation, the holding force of the compensation shutter in its closed state varies according to the greater or lesser compression of the spring since there is a relative movement between the bearing shoulder of the spring and the spring. shutter compensation.

Moreover, the effect of this spring tending to return the membrane in the rear position, therefore adds a force to overcome during the discharge stroke. This addition leads to the fact that there prevails in the hydraulic control chamber an ever higher pressure than that in the working chamber, which has advantages especially in the degassing of working oil which is lower.

Two embodiments are possible for the compensation shutter, namely, a realization in the form of a drawer and a valve-shaped embodiment. Furthermore, the support shoulder of the spring secured to the membrane may serve as limiting the discharge stroke of the membrane, either in the form of a stop or in the form of an isolation valve of a part of the control chamber adjacent to the membrane of the other part of this adjacent chamber of the piston and provided with a relief valve.

Other characteristics and advantages will emerge from the description given below of exemplary embodiments of the diaphragm pump according to the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

• la figure 1 est une vue en coupe d'une pompe conforme à l'invention,
• la figure 2 illustre par une vue partielle une variante de réalisation dans laquelle la membrane est protégée contre les surcourses de refoulement,
• la figure 3 est l'illustration d'une variante de réalisation de l'obturateur de compensation.

Reference will be made to the appended drawings among which:

• FIG. 1 is a sectional view of a pump according to the invention,
• FIG. 2 illustrates, in a partial view, an alternative embodiment in which the membrane is protected against overflows of discharge,
• Figure 3 is an illustration of an alternative embodiment of the compensation shutter.

DETAILED DESCRIPTION OF THE INVENTION

In a known manner, a hydraulically operated diaphragm pump is composed of a two-part pump body 1 and 2, between which a diaphragm 3 is clamped at the periphery.

With part 1 of the body, the membrane delimits a pumping chamber 4 to which end a suction pipe 5, a discharge pipe 6 equipped unidirectional valves not shown.

With part 2 of the body, this membrane delimits a chamber 7 filled with a hydraulic fluid that can be cyclically displaced forward (to the left of the figure) or to the rear by means of a piston 8 moved with a reciprocating motion. This provides a hydraulic control of the variation of the volume of the chamber 4 pumping.

This chamber 7 is also equipped in known manner, a relief valve 9 which limits the discharge pressure to a determined safety value and which is often combined with a device for degassing the control fluid.

It is noted in Figure 1 that the chamber 7 has two parts. Part 7 has generally cylindrical side of the piston 8, and a portion 7 b tapering toward the membrane 3. The portions 7 and 7b are connected, through a septum 2a, by a connecting conduit 10.

A refilling duct 14 is formed in the body 2 (the partition 2 a) and is from an oil tank 14 a comprising a non-return valve 14b. This duct 14 opens into the chamber 7 when this outlet is discovered by a closure member 15 which normally isolates the duct 14 from this chamber 7.

The closure member 15 herein is a valve equipped with a tubular actuating rod 16, sealingly slidably mounted in the wall 2a of the part 2 of the body and whose end 16a, opposite to the valve 15 is adjacent to the membrane 3, when it reaches close to a setpoint position reached at the end of the suction stroke.

The valve 15 closes, by resting on the wall 2a, the opening of an annular channel 17 formed at least partially around the valve stem 16 and into which the end of the conduit 14 opens out. The valve stem 16 forms a sleeve in which slides a rod 12 integral with the membrane 3. This rod 12 is equipped at its free end with a shoulder 11 (here bell-shaped) to form a support for a spring 13 for assisting the suction of the membrane 3 and whose other end rests on the valve 15 tending to press against the wall 2a.

When the membrane 3 reaches its target position, a position which corresponds to the conformation at rest of the diaphragm whose stiffness is such that in the absence of any suction it tends to open the valve 15, it may already have displaced this valve 15 and open the communication between the conduit 14 and the chamber 7. This opening is made without effort to overcome because at the time of contact of the membrane with the control rod 16 of the valve 15, the force of the spring on the valve 15 is neutralized. Indeed, this force is then exerted between the shoulder 11 and the membrane 3 which form a non-deformable moving element embodying the valve 15. The opening of the compensation valve therefore requires no effort and the pressure in the chamber 7 is substantially equal, during the suction phase, the pressure of the pumping chamber 4, which allows to achieve aspirations under a large vacuum in any case less than 0.3 bar.

In the beginning of the discharge stroke, the valve 15 closes and it is necessary to overcome the force of the spring 13 before moving the membrane 3 forward. There then reigns in the chamber 7 a pressure always greater than that prevailing in the pumping chamber 4, which is rather favorable to the proper functioning of the pump (less degassing of dissolved gases for example). At the end of the discharge stroke, the shoulder 11 may limit the stroke of the membrane 3 by pressing on the valve 15 or on the wall 2a.

In the variant shown in Figure 2, the shoulder 11 is bell-shaped 11a which forms a valve capable of closing the outlet of the channel 10 in Part 7 is of the hydraulic chamber and which insulates the part 7B of the portion 7a when the membrane 3 exceeds a discharge end in set position. This part 7a is in permanent communication with the discharge valve 9, so that a further stroke of the piston 8, whereas the discharge end position is reached by the membrane 3, lead to derive excess fluid through the discharge valve 9 to a tarpaulin of oil.

In Figure 3, the shutter member 15 is constituted by a drawer 18 slidably mounted in a bore of the partition wall 2 a of the body 2 of the pump. The drawer 18 is tubular with a collar 19 at its end opposite to the membrane, on which the spring 13 applies relying otherwise under the shoulder 11 (valve 11a) and tending to press the collar 19 against the wall 2a of the body 2 which is crossed by the connecting conduit 10. the drawer 18 is stepped outer diameter so that a portion 18a of larger diameter covers the opening of the conduit 14 into the bore when the collar 19 is support on the partition 2 a . When the collar 19 remote from the partition 2a, the portion 18 b of smaller diameter of the spool 18 discovers the opening of the conduit 14 and the chamber 7 can be replenished by suction.

The drawer 18 forms a sleeve in which the rod 12 of the valve 11 a or the shoulder 11. The end 18 c opposite to the collar 19 is located near the target position reached by the membrane 3 in the end position suction.

The opening of the conduit 14 into the bore of the partition 2 a is found as soon as the membrane 3 has reached its desired position at the end of aspiration, that is to say as soon as it comes into contact with the end 18 c of the drawer 18 with the same effects as those described with regard to Figures 1 and 2.

Returning to FIG. 1, it can be seen that part 2 of the pump body constitutes the enclosure of the hydraulic chamber 7. This enclosure belongs to a general frame 20 which also forms a support for a drive motor 21 and a housing for a mechanism transmission of the motor 21 to the piston 8, which mechanism is not shown and which generally consists of a wheel and worm gear system, the wheel being equipped with an alternating drive eccentric piston.

This housing also contains a lubricating oil bath 22 of the transmission mechanism. The casing 20 communicates with the cover 14 a of the part 2 of the pump body via a filter 23. Thus, when there is a compensation request in the chamber 7, the fluid is withdrawn from the cover 14a which consequently is completed by lubricating oil drawn from the filter 23 itself from the bath 22 in the housing 20. It will be noted in this figure that the fluid of the chamber 7 derived by the relief valve 9 returns to the casing 20 in the bath 22.

This arrangement allows a simplified construction of the pump. Indeed, the pumps of the prior art implementing a diaphragm controlled compensation valve all have a separate fluid for the hydraulic control chamber, to ensure purity while a lubricating fluid is loaded. progressively particles from lubricated parts in motion. To be able to maintain an acceptable suction height, the calibrated valve must be tared to a minimum, which means that very little effort is required to obtain displacements. These forces may be less than those necessary to overcome unwanted friction forces generated by any particles that would block the valve. The means of the invention have overcome the return spring of the valve and its force for compensation: this allowed to admit a less purified fluid.

Claims (7)

Diaphragm pump (3) comprising, in a body (1, 2), a hydraulic control chamber (7) arranged between a reciprocating piston (8) and the diaphragm (3), the pump comprising means (14, 15) for compensating for leaks in the hydraulic chamber (7) comprising a feed line (14) opening into the hydraulic chamber (7) through a normally closed compensation shutter (15) controlled at the opening by the membrane (3), characterized in that the shutter (15) compensation aforesaid is operated by pressing the membrane (3) on a free end (16a) of a rod (16) of its control, the membrane (3) ) being subjected to the force of a suction assist spring (13), which cooperates with the aforementioned shutter (15) to return it to its closed state, by pushing back the free end (16a) of the control rod (16) in the direction of the diaphragm (3), this spring (13) forming with the shutter (15) a displaced moving element without being deformed by the membrane (3) during a suction overtravel. Diaphragm pump according to Claim 1, characterized in that the compensating shutter is a valve (15). Diaphragm pump according to Claim 1 or Claim 2, characterized in that the compensating shutter is a slide (18). Diaphragm pump according to one of the preceding claims, characterized in that the suction assist spring (13) is arranged between the shutter (15) and a shoulder (11) carried by the end of a rod (12) integral with the membrane and coaxial with the shutter (15). Diaphragm pump according to Claim 4, characterized in that the shoulder (11) constitutes an abutment limiting the displacement of the diaphragm (3) at the end of the discharge stroke. Diaphragm pump according to Claim 3 or Claim 5, characterized in that the hydraulic chamber (7) is in two parts, one (7a) in the vicinity of the piston and the other (7b) in the vicinity of the diaphragm, connected by a channel (10), the abutment (11) forming a shutter valve (11a) of the outlet channel (10) in the portion (7a) of the adjacent chamber of the piston. A diaphragm pump as claimed in any one of the preceding claims comprising a general frame (20) forming a support for a drive motor (21) and a housing for a motion transmission mechanism between the engine and the piston (8) of the pump and for a lubrication oil bath (22) of this mechanism, characterized in that the hydraulic chamber (7) is in permanent communication with the casing (20) via the feed duct (14) and a filter (23).

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