diaphragm piston pump

Description

[0001] The invention relates to a diaphragm piston pump with a leakage control.

[0002] One of the basic requirements for safe operation of diaphragm piston pumps is the presence of a defined amount of pre-filled fluid between the piston and the diaphragm / diaphragm tube. If the amount of pre-filled fluid is too low, there is a risk that the diaphragm will be drawn into the pump housing, overstretched, and ultimately perforated. If the amount of pre-filled fluid is too high, there is a risk that the diaphragm will block the pumping chamber.

[0003] During operation of a diaphragm piston pump, there are a variety of operating conditions that can vary the amount of feed fluid. Due to their design, piston or plunger seals have a certain amount of residual leakage, which also changes over time. To achieve optimal efficiency, diaphragm pumps require continuous venting. Here, too, a quantity of feed fluid is vented into the oil reservoir with each stroke. To ensure that the design pressure is not exceeded, diaphragm pumps are equipped with pressure relief valves. If the pressure in the system rises above the desired value, usually preset by a spring, the valve opens and allows the feed fluid to flow into the oil reservoir, which also changes the defined amount of feed fluid.

[0004] 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 compensation valve. The vacuum leakage compensation valve serves to compensate for hydraulic fluid leakage losses under negative pressure. A disadvantage of the purely vacuum-controlled diaphragm position control by vacuum leakage compensation valves with exclusively vacuum-controlled leakage compensation valves is that the leakage flow is supplemented in an uncontrolled manner. In addition, the diaphragm moves so far forward that it ruptures if the vacuum on the medium side exceeds the opening pressure of the vacuum leakage compensation valve, for example, due to a blocked suction line and / or a closed suction slide.

[0005] From DE 203 21 039 U1, a reliable, vacuum-insensitive leakage supplementary control for diaphragm piston pumps is known, which ensures that supply liquid is only replenished after the diaphragm has contacted the control plate and a check valve has first opened mechanically.

[0006] During the suction stroke, the hose diaphragm is forced towards the piston hydraulic chamber. If the volume of hydraulic oil drops due to leakage in the hydraulic chamber, the diaphragm presses on the control plate, which in turn opens the refill valve via a lever. The leakage flow supplementary valve is actuated in a controlled manner by the hose diaphragm movement, i.e. first the leakage valve (check valve) is opened mechanically. Only then does the vacuum-controlled supplementary valve become active. As the piston moves back further, a vacuum is created in the reserve chamber because the diaphragm cannot move any further. If this vacuum exceeds the adjustment range of the refill valve (supplementary valve), the supplementary valve opens and the reserve fluid discharged into the reserve chamber during the pressure stroke is drawn back in 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. Since the vacuum-activated refill valve can only open when mechanically actuated by the hose diaphragm via a lever, this ensures that the hose diaphragms are not overstretched due to overfilling, even under vacuum.

[0007] This leakage control with separate leakage and supplementary valves is still considered the standard today.

[0008] From DE 40 36 696 A1 a diaphragm pump with a leakage compensation valve mechanically controlled by a diaphragm is known.

[0009] However, as the application areas expand, the rocker arm becomes a regulatory component. The rocker arm mechanically connects the control unit to the combined leakage and supplementary valve. The opening required for installing the rocker arm in the pump housing, which is a design constraint, represents a limitation in structural design, making pressures > 1,000 bar very difficult to achieve. Furthermore, the system's inertia limits the pump's maximum stroke rate.

[0010] DE 41 41 670 A1 relates to a hydraulically driven diaphragm pump. The diaphragm pump has a diaphragm position-controlled leakage compensation device, which includes a control valve with a control slide slidably guided in the area of ​​the connecting channel between the diaphragm working chamber and the piston working chamber. This control slide opens a connection from a reservoir to the piston working chamber when the diaphragm is in the suction stroke position.

[0011] DE 27 54 318 A1 discloses a feed control system for a diaphragm pump. Oil refilling is achieved via a combination of a slide valve attached to the diaphragm and a regulating valve. A negative pressure in the pressure oil chamber only opens the regulating valve when the diaphragm assumes its suction stroke position and the slide valve opens the channel to the regulating valve.

[0012] EP 0 175 105 A1 describes a diaphragm pump. The hydraulic working chamber features a pressure relief valve.

[0013] The object of the invention is to provide an improved leakage control.

[0014] This object is achieved according to the invention in that a control unit is provided in the region of the diaphragm, which control unit can be activated by the pressure of the diaphragm during the suction stroke, wherein the control unit is hydraulically connected to a leakage compensation valve, via which pre-filled fluid can be released into the piston chamber of the diaphragm piston pump, wherein the leakage compensation valve is only effective upon activation of a leakage valve, wherein the leakage valve is hydraulically activated.

[0015] According to the invention, the position of the diaphragm is transmitted hydraulically rather than mechanically via a control rod and rocker arm. Thus, the position of the supplementary valve is no longer directly tied to the axis of the control rod or the tilting direction of a rocker arm. This enables efficient leakage control without the spatial and mechanical limitations of the prior art.

[0016] A further development of the invention consists in that the control unit is arranged between the piston of the diaphragm piston pump and the secondary hose membrane, wherein a control plate which can be acted upon by the secondary hose membrane is guided by a control rod so as to be displaceable in the longitudinal direction against a restoring force, wherein the control rod has an activation piston for the hydraulic connection to the leakage valve.

[0017] The control plate is acted upon by the diaphragm during the suction stroke and, together with the control rod, moves away from the diaphragm against the restoring force of, for example, a spring. The activation piston forces 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 considered the secondary diaphragm.

[0018] This results in hydraulic activation of the leakage valve.

[0019] According to the invention, the leakage valve has a control piston, upon pressure being applied to which the leakage valve opens, so that the pressure applied in the hydraulic connection acts via a connecting channel on a supplementary valve in order to open the latter against a restoring force when a pressure smaller than the opening pressure of the supplementary valve is applied.

[0020] The opening supplementary valve replenishes the pre-filled fluid. It is also possible to install the control piston as a separate component on the valve.

[0021] An embodiment of the invention is explained in more detail below with reference to drawings.

[0022] It shows Figure 1 shows a sectional view of the device according to the invention, Figure 2 shows a detailed view of the control unit, Figure 3 shows a detailed view of the leakage and supplementary valve.

[0023] The Figures 1 to 3show a double-diaphragm hose pump having a control unit (1) according to the invention and a leakage compensation valve (2) according to the invention. The double-diaphragm hose pump has a pressure-side discharge valve (3) and a suction-side discharge valve (4), an intermediate pressure flange (5), an intermediate ring (6), a hose housing (7), a primary hose diaphragm (8), and a secondary hose diaphragm (9). A coupling fluid (15) is arranged between the primary hose diaphragm (8) and the secondary hose diaphragm (9), and a hose diaphragm condition monitor (HDG) (13) is provided.

[0024] A piston (plunger) (10) sealed by piston seals (18) exerts pressure on a reservoir fluid (15). This compresses the delivery chamber (17) so that the fluid to be pumped is discharged from the delivery chamber (17) through the pressure-side discharge valve (3) out of the pump. When the piston (10) is retracted, the pressure on the reservoir fluid (15) is reduced, the double hose diaphragm (8, 9) moves back, and fluid is discharged into the delivery chamber via the suction-side discharge valve (4).

[0025] In the device according to the invention, the position of the double hose membrane (8, 9) is not transmitted by means of a control rod and rocker arm as in the prior art, but hydraulically. To achieve this, as in Figure 2As shown, a control plate (20) is provided, which is connected to a control rod (23) having an activation piston (26). The control rod (23) with the control plate (20) is displaceable in the longitudinal direction against the restoring force of a return spring (24).

[0026] During the suction stroke, the double hose diaphragm (8, 9) moves toward the wall of the hose housing (7). The double hose diaphragm (8, 9) consequently pushes the control plate (20) toward the control housing (21), causing the activation piston (26) to displace the pre-filled fluid (15) into the activation channel (25). This results in a pressure increase within the activation channel (25).

[0027] The combined leakage and supplementary valve (2) is in Figure 3shown. 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 supplementary valve (31), which is pressed against its seat by the spring (33). If the pressure here is less than the opening pressure of the supplementary valve (31), the supplementary valve (31) opens and, via the connecting channel (36), adds a predefined amount of supply fluid (15) from the oil reservoir (11) to the pump chamber. If the applied pressure is greater than the opening pressure of the supplementary valve (31), the supplementary valve (31) remains closed. The oil reservoir (11) has a pressure relief valve (12).

Claims

1. Diaphragm piston pump comprising a leakage control, characterized in that 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. Diaphragm piston pump according to claim 1, characterized in that 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. Diaphragm piston pump according to claim 1 or claim 2, characterized in that 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.