PISTON DIAPHRAGM PUMP

Abstract

A diaphragm piston pump with a leakage control has a control unit in the area of the diaphragm, which can be activated by the pressure of the diaphragm during the suction stroke, wherein the control unit is hydraulically connected to a leakage replenishing valve, via which the sealing liquid can be discharged into the piston chamber of the diaphragm piston pump. The position of the diaphragm is not transmitted mechanically via a control rod and a rocker arm, but hydraulically. This makes it possible to achieve efficient leakage control without the spatial and mechanical restrictions of the prior art.

Description

The invention relates to a diaphragm piston pump with a leakage control.

One of the basic requirements for the secure operation of diaphragm piston pumps is the presence of a defined amount of sealing liquid between the piston and the diaphragm/hose diaphragm. If the amount of sealing liquid is too low, there is a risk that the diaphragm will be pulled into the pump housing, overstretched and ultimately perforated. If the amount of sealing liquid is too high, there is a risk that the diaphragm will block the delivery chamber.

During the operation of a diaphragm piston pump, there are a number of operating states that can vary the amount of sealing liquid. Piston or plunger seals have certain residual leakages due to their design, which also change during the period of use. In order to achieve optimum efficiency, diaphragm pumps require continuous venting. Here too, a quantity of sealing liquid is vented into the oil container with each stroke. Diaphragm pumps have pressure relief valves to ensure that the design pressure is not exceeded. If the pressure in the system exceeds the desired value, which is usually preset by a spring, the valve opens and allows the sealing liquid to flow into the oil container, which also changes the defined quantity of sealing liquid.

Conventional diaphragm piston pumps are equipped with a combined diaphragm stroke limiter and support plate, which is combined with a position control based on a vacuum leakage flow replenishing valve.

The vacuum leakage flow replenishing valve is used to compensate for leakage losses of hydraulic fluid in the event of negative pressure. One disadvantage of purely vacuum-controlled diaphragm system control using vacuum leakage flow replenishing valves with exclusively vacuum-controlled leakage flow replenishing valves is that the leakage flow is compensated in an uncontrolled manner. In addition, the diaphragm moves so far forward that it ruptures if the vacuum on the fluid side exceeds the opening pressure of the vacuum leakage flow replenishing valve, for example due to a blocked suction line and/or a closed suction slide valve.

DE 203 21 039 U1 discloses a reliable leakage compensating control for diaphragm piston pumps that is insensitive to vacuum and ensures that the sealing liquid is only compensated after the diaphragm has come into contact with the control disc and a non-return valve has first opened mechanically.

During the suction stroke, the hose diaphragm inevitably moves in the direction of the piston hydraulic chamber. If the volume of hydraulic oil drops due to leakage in the hydraulic chamber, the diaphragm presses on the control disc, which in turn opens the refill valve via a lever. The leakage flow replenishing valve is actuated in a controlled manner by the hose diaphragm movement, i.e. the leakage valve (non-return valve) is opened mechanically first. Only then does the vacuum-controlled replenishing valve become active. As the piston continues to retract, a vacuum is created in the sealing chamber as the diaphragm cannot move any further. If this vacuum exceeds the setting range of the refill valve (replenishing valve), the replenishing valve opens and the sealing liquid expelled into the reserve chamber during the pressure stroke is retrieved by the stationary vacuum during the further piston suction stroke. In this way, the missing volume of hydraulic fluid in the hydraulic chamber is replenished. As the vacuum-activated refill valve can only open when it is mechanically actuated by the hose diaphragm via a lever, it is ensured that the hose diaphragms are not overstretched due to overfilling, even in the event of a vacuum.

This leakage control with separate leakage and replenishing valve is still considered the benchmark today.

DE 40 36 696 A1 discloses a diaphragm pump with a leakage replenishing valve that is mechanically actuated by a diaphragm.

However, as the range of applications increases, the rocker arm becomes a regulating component. The rocker arm mechanically connects the control unit with the combined leakage and replenishing valve. The design-related opening required to install the rocker arm in the pump housing represents a limit in the structural-mechanical dimensioning, so that pressures >1,000 bar can only be achieved with great effort. The system also restricts the maximum number of pump strokes that can be realized due to its inertia.

The object of the invention is to create an improved leakage control.

According to the invention, this object is achieved in that a control unit is provided in the area of the diaphragm, which can be activated by the pressure of the diaphragm during the suction stroke, wherein the control unit is hydraulically connected to a leakage replenishing valve, via which the sealing liquid can be discharged into the piston chamber of the diaphragm piston pump.

According to the invention, the position of the diaphragm is not transmitted mechanically via a control rod and a rocker arm, but hydraulically. This means that the position of the replenishing valve is no longer directly linked to the axis of the control rod or to the tilting direction of a rocker arm. This makes it possible to achieve efficient leakage control without the spatial and mechanical restrictions of the prior art.

A further development of the invention is that the control unit is arranged between the piston of the diaphragm piston pump and the secondary hose diaphragm, wherein a control disc, which can be acted upon by the secondary hose diaphragm, is guided by means of a control rod so as to be displaceable in the longitudinal direction against a restoring force, wherein the control rod has an activating piston for the hydraulic connection with the leakage valve.

The control disc is acted upon by the diaphragm during the suction stroke and moves away from the diaphragm together with the control rod against the restoring force of a spring, for example, as a result of which the activating piston presses hydraulic fluid into an activation channel of the hydraulic connection between the control unit and the leakage valve. If the pump has only one diaphragm, this is to be equated with the secondary diaphragm.

This results in hydraulic activation of the leakage valve.

According to the invention, it is provided that the leakage valve comprises a control piston, on the pressurization of which the leakage vale opens, so that the applied pressure in the hydraulic connection acts via a connecting channel on an replenishing valve in order to open it against a restoring force when a pressure lower than the opening pressure of the replenishing valve is applied.

The sealing liquid is replenished through the opening replenishing valve. It is also possible to provide the control piston as a separate component on the valve.

In the following, an exemplary embodiment of the invention is explained in greater detail with reference to drawings.

The Figures show in:

FIG. 1 a sectional view of the device according to the invention,

FIG. 2 a detailed illustration of the control unit,

FIG. 3 a detailed illustration of the leakage and replenishing valve.

FIGS. 1 to 3 show a double diaphragm peristaltic pump which has a control unit (1) according to the invention and a leakage replenishing valve (2) according to the invention. The double diaphragm peristaltic pump has a delivery valve (3) on the pressure side and a delivery valve (4) on the suction side, an intermediate pressure flange (5), an intermediate ring (6), a hose housing (7), a primary hose diaphragm (8) and a secondary hose diaphragm (9), wherein a coupling fluid (15) is arranged between the primary hose diaphragm (8) and the secondary hose diaphragm (9) and a hose diaphragm status monitor (HDG) (13) is provided.

The secondary hose diaphragm (9) is pressurized via a piston (plunger) (10) sealed by means of piston seals (18), which applies pressure on a sealing liquid (15), whereby the delivery chamber (17) is compressed so that the fluid to be pumped is delivered from the delivery chamber (17) through the pressure-side delivery valve (3) on the discharge side of the pump. When the piston (10) is retracted, the pressure on the sealing liquid (15) is reduced, the double hose diaphragm (8, 9) moves back and fluid is pumped into the delivery chamber via the suction-side delivery valve (4).

In the device according to the invention, the position of the double hose diaphragm (8, 9) is not transmitted by means of a control rod and rocker arm as in the prior art, but hydraulically. To achieve this, a control disc (20) is provided—as shown in FIG. 2—which is connected to a control rod (23) which has an activating piston (26). The control rod (23) with the control disc (20) can be displaced in the longitudinal direction against the restoring force of a return spring (24).

During the suction stroke, the double hose diaphragm (8, 9) moves in the direction of the wall of the hose housing (7). As a result, the double hose diaphragm (8, 9) presses the control disc (20) in the direction of the control housing (21) so that the activating piston (26) displaces the sealing liquid (15) into the activation channel (25). As a result, there is an increase in pressure inside the activation channel (25).

FIG. 3 shows the combined leakage and replenishing valve (2). The increased pressure in the activation channel (25) acts on the control piston (34), which opens the leakage valve (30) against the force of the spring (32). The applied system pressure now acts via the connecting channel (36) on the replenishing valve (31), which is pressed against its seat by the spring (33). If the pressure applied here is less than the opening pressure of the replenishing valve (31), the replenishing valve (31) opens and replenishes a predefined amount of sealing liquid (15) from the oil reservoir (11) into the pump chamber via the connecting channel (36). If the applied pressure is greater than the opening pressure of the replenishing valve (31), the replenishing valve (31) remains closed. The oil reservoir (11) has a pressure relief valve (12).

Claims

1. A diaphragm piston pump comprising a leakage control, wherein a control unit (1) is provided in the region of the diaphragm, which can be activated by the pressure of the diaphragm (8, 9) during the suction stroke, wherein the control unit (1) is hydraulically connected to a leakage replenishing valve (2), via which the sealing liquid (15) can be discharged into the piston chamber of the diaphragm piston pump, wherein the supplementary leakage valve (2) is only effective when a leakage valve (30) is activated, wherein the leakage valve (30) can be activated hydraulically.

2. The diaphragm piston pump according to claim 1, wherein the control unit (1) is arranged between the piston (10) of the diaphragm piston pump and the secondary hose diaphragm (9), wherein a control disc (20) which can be acted upon by the secondary hose diaphragm (9) is guided by a control rod (23) so as to be displaceable in the longitudinal direction against a restoring force, wherein the control rod (23) comprises an activating piston (26) for the hydraulic connection with the leakage valve (30).

3. The diaphragm piston pump according to claim 1, wherein the leakage valve (30) comprises a control piston (34), on the pressurization of which the leakage valve (30) opens, so that the applied pressure in the hydraulic connection acts on an replenishing valve (31) via a connecting channel (36) in order to open said valve against a restoring force when a pressure lower than the opening pressure of the replenishing valve (31) is applied.

4. The diaphragm piston pump according to claim 2, wherein the leakage valve (30) comprises a control piston (34), on the pressurization of which the leakage valve (30) opens, so that the applied pressure in the hydraulic connection acts on an replenishing valve (31) via a connecting channel (36) in order to open said valve against a restoring force when a pressure lower than the opening pressure of the replenishing valve (31) is applied.