Diaphragm pump

BACKGROUND OF THE INVENTION

[0001] In chemical research laboratories, chemical reactions are carried out in 100-ml glass vessels. For reactions of this kind, the additional outlay in terms of apparatus and therefore the costs of the apparatus for a test set-up must be kept as low as possible. For a continuously, or even discontinuously, operating test installation, metering and conveying pumps are required, which are capable of metering small substance quantities within the range of less than 1 ml per minute in a very compact and reproducible manner and so as to be insensitive to blockage. In the laboratories, different reactions are carried out at short time intervals, and consequently the test conditions and also the chemicals used change, so that a large number of substances with different properties must, if possible, be metered accurately by means of one type of pump. The metering accuracy of the pumps is defined essentially by the short-term accuracy. In this case, the substances to be metered must be metered reproducibly at short time intervals (seconds or minutes) with a low degree of error.

[0002] In particular, known piston or diaphragm pumps are used for tasks of this kind. These pump types are oscillating positive-displacement pumps. These pumps operate on the positive-displacement principle and are equipped with non-return valves (i.e., “check valves”) on the pump suction and delivery sides. A change in metering quantity is carried out by a variation in the piston or diaphragm stroke, so that a changed clearance volume occurs in the pump head, depending on the set stroke. The non-return valves exert a critical influence on the pumping function and the metering accuracy of the pumps.

[0003] This leads to a reproducible metering of the smallest possible liquid quantities being dependent directly on the operating capacity of the pump valves which are in contact with the product. The opening and closing functions of the valves are dependent on the density and viscosity of the substance to be conveyed, and therefore a reproducible and substance-independent closing and opening are not ensured, and metering deviations occur, particularly within small time segments (short-term accuracy). Furthermore, the travel of the closing body in the non-return valves is non-linear, and where, for example, a spherical closing body is used, the spherical closing body executes a wobbling movement until it becomes seated in the sealing seat and shuts off the passage of substance. It is known that preferably ball-type non-return valves are used in piston and diaphragm pump heads. The change in the pumping capacity is carried out by a variation in the stroke, so that the pistons or diaphragms no longer cover the maximum stroke travel and the suction behaviour is thereby also impaired.

[0004] In particular, in the metering of liquid substances having different viscosities and/or densities, the closing time of the non-return valves is affected by the viscosity and density, thus leading to an increase in the metering error.

[0005] The known piston and diaphragm pumps are driven via gear units by means of a camshaft or eccentric shaft. The direct coupling of these pumps to drive units leads to large appliance dimensions, the form of construction of which is too large for many miniaturized test installations. The mechanical drives must be manufactured with high precision, which also increases the investment costs. Pulsating positive-displacement pumps are also equipped with magnetic drives. As a result, the structural dimensions of these pump types are slightly smaller and the pumps have a constant clearance volume in the pump head.

[0006] Microsystem pumps, by means of which very small liquid quantities can be conveyed, are known. Micropumps are what may be referred to as precision pumps, the functioning of which is no longer ensured when there is the least possible product-side contamination. The flow ducts and positive-displacement spaces within the micropump heads possess dimensions on the order of a few micrometers. Contaminated products quickly block flow ducts or jam the dynamically moved pump parts, so that a metering operation can be quickly interrupted. Small product ducts are not suitable for conveyance and metering of viscous substances, because the pressure loss is too great.

[0007] Various diaphragm-type micropumps are known, which have very small structural dimensions on account of piezoelectric or thermopneumatic drives and can thereby meter small substance quantities. The patent specification DE 4 402 119 C2 (corresponding to U.S. Pat. No. 5,725,363) describes a diaphragm-type micropump which is likewise driven thermally. These drive systems always function on the principle of a thermally initiated volume expansion on one diaphragm side, so that the conveying diaphragm of the pump generates a pumping action as a result of the deflection. Relatively high differential pressures cannot be overcome by means of these drive systems, for example in order to meter a liquid substance into a container which is under higher pressure. Moreover, these pumps are susceptible to blockage, so that operational use in chemical laboratories is not satisfactory and pumps of this kind are not used in preparatory chemical laboratories.

[0008] Microsystem pumps, which may be referred to as toothed-ring pumps, operate at high rotational speeds and generate a pressure in an annular gap. During the pressure build-up in the discharge region of the pump, a backflow into the suction region takes place, in particular because of the mechanical tolerances of the rotor and stator of the pump, so that the pump efficiency is greatly reduced. As a rule, the reproducible metering of low-viscosity substances against a high pressure is not ensured due to the low drive power of microsystem pumps.

[0009] The object on which the invention is based is, therefore, to develop a pump which is highly miniaturized, conveys small volume quantities, for example of 5 μl to 1000 μl/stroke and per unit time, and possesses high short-term metering accuracy. The pump is to have a good suction behavior and to convey counter to pressure, so that, even in the non-flooded state of the pump head, conveyance counter to pressure is possible. The metering of substances of different density is not to have any appreciable influence on the conveying accuracy and the metering behavior. The fault susceptibility to blockage by product impurities is to be substantially reduced, so that additional fine filters on the suction side of the pump are not needed. Necessary suction and delivery valves of the pump head are to open and close reproducibly, independently of density and/or viscosity, and, in particular, be leak-tight to gas pressure when closed; so that, during pumping, no backflow takes place, high efficiency is achieved and accurate pumping counter to pressure thereby becomes possible. The metering capacity of the volume flows to be conveyed must be adjustable or variable in a simple way and is to amount from 5 to 100.000 μl/stroke preferred from 10 to 10.000 μl/stroke and especially preferred from 10 to 10 00 μl/stroke. The pump is to be capable of being produced cost-effectively from various resistant materials, particularly because of different corrosion requirements in the chemical industry. In view of the occasionally rough operating conditions that the pump may be exposed to, the pump should be capable of simple and cost-effective repair and maintenance.

[0010] Furthermore, investment benefits, as compared with the prior art, are to become clearly apparent. The design of the control or drive technology is not to exert any influence on the pump-head size and on the possibility of integration into a miniaturized test installation set-up. The pump is to be constructed in a modular manner, so that the metering pump can be modified in a simple way by corresponding additions or the exchange of module parts. Is should be possible to change the metering capacity without the positive-displacement travel of the diaphragm or piston in the pump head increasing the clearance volume, so that the sucked-in liquid volume is displaced out of the pump head completely at any time.

SUMMARY OF THE INVENTION

[0011] The object is achieved, according to the invention, by means of a pneumatically driven pump head which is constructed in a modular lamella manner and which consists of at least three rigid lamellae (plates), and, in the region of the individual parting plane of the middle plate and of the respectively contiguous adjacent plates, there is at least one concave depression, and each depression is covered completely by an elastic diaphragm and the diaphragm is on one side part of the product space of the pump and at the other side part of the control space. The depressions on one side or on both sides of the diaphragm establish the maximum travel by which the elastic diaphragm can be deflected.

DETAILED DESCRIPTION

[0012] The subject of the invention is a diaphragm pump with a multi-part pump body, comprising at least three rigid plates and in each case an elastic diaphragm arranged between these plates, the plates forming at least one pumping chamber and at least two shut-off chambers, in particular in a three-dimensional form of a truncated spherical segment of a spherical zone (cap), cylinder or cone, in each case with an inlet and an outlet orifice for the conveyable material, and the pumping and shut-off chambers being connected to one another via connecting ducts, and, together with an inlet duct, the connecting ducts and an outlet duct, forming a passage duct, characterized in that the pumping and shut-off chambers are divided by the diaphragms in each case into a product space and a control space, and the control spaces have control lines which are connected to a control unit.

[0013] In the case of pneumatic activation, the control space is connected, in particular, via a duct which passes through the respective outer plate, to, for example, an electropneumatic control unit which has, for example, a vacuum generator in a secondary line, in order to enable alternating pressure or vacuum loading of the control space. It is also possible to use a hydraulic fluid for the pressure and draught loading of the control space. According to a control program which has at least four control steps proceeding in succession, each with an associated timer, for example, the diaphragms are deformed into the pumping and shut-off chambers, so that the volume of the control space or the product space is alternately increased and reduced. The diaphragm simultaneously opens or closes the inlet and outlet orifices of the chambers, said inlet and outlet orifices lying in the diaphragm region, so that, during the closing operation, at least the feed ducts which are in contact with the product are sealingly closed and, in the case of a predetermined control, at least one of the diaphragms lying in the direction of flow generates a reproducible volume displacement. The control unit is arranged decentrally, particularly, to facilitate the degree of miniaturization, and, in the case of a pneumatic control, is connected to the pump head, for example, by means of flexible hoses.

[0014] By a “control unit” is meant here a combination of electronic control and actuators, for example electropneumatic switching valves, which are mounted on a compressed-air/vacuum distributor which has a pneumatic vacuum generator located in a secondary line. The electronic control and the actuators may be mounted, for example, together in a housing. The electropneumatic valves are operated by means of a control program, in order to carry out an exact sequence of work steps for the pumping operation.

[0015] In particular, the shut-off and pumping chambers are sealed off at the edge by means of the inserted and compressed diaphragms.

[0016] In a preferred version, each shut-off and pumping chamber has an individually assigned diaphragm and the diaphragms are inserted between the plates. By, for example, the plates being screwed together, the diaphragms are clamped in, in order to close the pressure-loaded control and product spaces sealingly relative to the outside in the parting planes of the plates.

[0017] The clamping-in of the diaphragms between the plates has advantages for the user in the event of repairs, so that, if the pump head has a possible defect, only the small part-diaphragm has to be exchanged and considerable material costs are saved. Assignment of the part-diaphragm to the respective chamber allows standardized diaphragm manufacture and reduces the manufacturing costs.

[0018] A preferred embodiment of the pump has, at least in the product space of the pumping chamber, a groove which connects the vertex of the pumping chamber to the outlet orifice of the pumping chamber.

[0019] The connecting groove from the vertex to the outlet orifice of the pumping chamber increases the accuracy and reproducibility of the conveying operation, in that a complete outflow of the metering volume is ensured. The groove forms a discharging collecting duct for the meterable material and compensates for differences in deformation of the elastic diaphragm. Between the inlet of the chamber and the groove there must be a surface present, so that the diaphragm can seal off the inlet orifice of the chamber in relation to the groove. The groove may, in the simplest version, be an elongate duct, but the groove may also have a branched contour in the depression.

[0020] In a further preferred embodiment of the pump, the control pressure on the diaphragm can be set in all the control spaces at least 0.1 bar higher than the prevailing pressure at the outlet duct, preferably the control pressure is at least 0.5 bar higher and, particularly preferably, the control pressure is 1 bar higher than the pressure at the outlet duct.

[0021] The higher differential pressure between the outlet duct and the control-side pressure ensures the leak-tight closing of the respective inlet orifices in the chambers by the diaphragm.

[0022] The diaphragms consist preferably of elastic material, in particular an elastomer, silicone, Viton® fluoroelastomer, Teflon® polytetraethylene or an EPDM rubber.

[0023] A preferred version of the pump in which a plurality of shut-off chambers have a common diaphragm is particularly advantageous.

[0024] A preferred version of the diaphragm pump is characterized in that the pump consists of at least three plates and the pumping and shut-off chambers are formed by depressions in the plates.

[0025] In a particularly preferred form of construction, the pump consists of at least three plates and the pumping and shut-off chambers are formed by depressions in a middle plate.

[0026] Another particularly preferred form of the diaphragm pump is characterized in that the pump consists of at least three plates and the pumping and shut-off chambers are formed by depressions in the outer plates.

[0027] In a preferred embodiment, that wall of the control space which is located opposite the diaphragm has, at least in the pumping chamber, a compensating volume, in particular a large-area depression, into which the diaphragm fits when there is a vacuum in the control space.

[0028] In a particularly preferred embodiment of the diaphragm pump, the compensating volume is at most 100% of the respective associated product-space volume, preferably the compensating volume is at most 20% and, particularly preferably, the compensating volume is at most 10% of the product-space volume.

[0029] Typically, the product spaces of the shut-off chambers are made smaller than the product space of the pumping chamber.

[0030] The center-to-center distance between the respectively adjacent inlet and outlet of each pumping or shut-off chamber is twice to ten times the largest hydraulic diameter of the respective inlet or outlet orifice, preferably the center to center distance is twice to five times and, particularly preferably, twice to three times.

[0031] The defined center-to-center distance is an important functional dimension of the chambers. It ensures a leak-tight closing of the feeding and discharging ducts or orifices and increases the reproducible conveyance of gaseous or liquid substances and has an influence on the degree of miniaturization.

[0032] In a preferred version, the connecting ducts between the pumping chamber and the shut-off chambers are made straight and have a ratio of duct length to the respective hydraulic diameter of the ducts of at most 20, preferably at most 10, particularly preferably at most 5.

[0033] The small clearance volume between the pumping and shut-off chambers improves the suction capacity of the pneumatic pump.

[0034] The plates of the diaphragm pump are connected preferably releasably to one another for cleaning and repair purposes.

[0035] A decentral electropneumatic control unit preferably also allows a synchronous activation of a plurality of pump heads, so that, when a plurality of pumps are operating in parallel, only one control unit is necessary.

[0036] By means of the diaphragm pump according to the invention, with a decentral electropneumatic control unit, efficient use, at the same time with low investment costs, is possible in the research sector. This becomes clear particularly when changing set tasks require conveying flows of different size which cannot be covered by one type of pump head. In the case of conveying flows of different size, only the pump head has to be exchanged, whereas the control part remains unchanged. The exchange of the pump head is carried out simply by the pneumatic control lines being unclamped.

[0037] The control for conveyance by means of the diaphragm pump is preferably to be carried out in such a way that a conveying stroke consists of at least four individual successive control steps, and each individual control step is separated from the subsequent control step by means of an intermediate constant or variable timer, and the conveying or metering capacity of the pump can be varied by the variation of at least one timer.

[0038] The timers introduced between the control steps ensure that the pneumatically triggered part-steps of the pumping stroke are carried out exactly and completely and the individual steps proceed reproducibly. The synchronous variation of all the timers for regulating the conveying capacity ensures a simple operator-friendly handling of the pump.

[0039] The timers belonging to the control are T from 0.1 seconds to 100 seconds, preferably the range is T from 0.3 seconds to 30 seconds and, particularly preferably, the timer is T from 0.5 seconds to 10 seconds.

[0040] Those timers ensure that the rapid electronic control signals (signal transit time) are not discontinued prematurely before the slower pneumatic operations for deflecting the diaphragms and the even more slower hydraulic positive-displacement operations on that side of the diaphragm which is in contact with the product are not completed. In particular, when viscous substances are conveyed, the fluid-dynamic operations require more time than the electronically triggered signals of the control.

[0041] The metering cycle consists preferably of at least four control steps and has at least two different timers, of which only one timer is variable and is used for regulating the pump cycle.

[0042] To optimize the pumping cycle of a pump according to the invention, the pneumatic opening and closing operations of the diaphragms in the shut-off chambers may be provided with a non-adjustable smaller timer and a variable timer may be used for the OPEN/SHUT switching of the middle larger pumping chamber.

[0043] Two different timers are advantageous particularly when the volume of the shut-off chambers is smaller than the volume of the pumping chamber.

[0044] In a particularly preferred mode of operation, the time of each timer is greater than the required switching time of the assigned electropneumatic multi-way valves.

[0045] Preferably at least two diaphragm pumps are connected in parallel to the electronic and the electropneumatic control unit.

[0046] One electropneumatic control unit can activate a plurality of diaphragm pumps in parallel, so that the pumps, if appropriate having pump chambers of different size, can synchronously meter various substances in different quantities simultaneously.

[0047] The thickness of the elastic diaphragm is preferably greater than 0.1 mm and less than 5 mm and the height of the pumping and shut-off chamber in the region of the vertex of the chamber (greatest extent above the diaphragm) is, in particular, greater than twice the diaphragm thickness and less than 10 times the diaphragm thickness.

[0048] The concave depressions in the plates may have different geometric shapes, such as, for example, that of a cylinder, of a spherical segment or of a cone frustum. The diaphragm pump preferably has smaller depressions for the suction-side and delivery-side shut-off chamber than for the pumping chamber, and all the depressions are arranged completely on the product side of the diaphragm side in the middle plates.

[0049] A variant of the diaphragm pump consists preferably of a pneumatically controlled pumping chamber, combined with two magnetically operated valves as shut-off chambers.

[0050] The diaphragms inserted in the pump are designed preferably with a diameter at least 20% larger than the formed diameter of the chambers in the parting plane of the plates.

[0051] In a further alternatively preferred embodiment, metallic diaphragms are used as the pump diaphragm and are inserted or are connected unreleasably by welding to one of the part-plates, in particular an outer plate.

[0052] In a further preferred embodiment, a pulsation damper is mounted downstream of the delivery-side shut-off chamber in the direction of flow, in particular in the region of the outlet duct of the diaphragm pump.

[0053] In a further particular embodiment, the diaphragm pump is equipped with an integrated spring-loaded overflow valve, in order to generate an internal product circulation in the diaphragm pump. If the connected control pressure is higher than the desired pump pressure, an integrated expansion possibility from the pump delivery side to the pump suction side is provided.

[0054] In a further particularly preferred version, at least two pump units, consisting of two pumping chambers with four associated shut-off chambers, to form a double diaphragm-pump head, are arranged in the three rigid plates.

[0055] The subject of the invention is also a pump set consisting of two or more diaphragm pumps, the diaphragm pumps according to the invention having a common control unit.

[0056] A pump set in which the diaphragm pumps have common continuous plates is preferred.

[0057] By reason of the diaphragm pump according to the invention, with an activatable section and delivery valve or with a suction-side and delivery-side shut-off chamber, depending on the design size, very small volume flows of <5 μl/stroke into the ml range per minute can be conveyed reproducibly. The separate set-up between the actual pumping unit or pump head and the decentral electric or electropneumatic control unit is particularly advantageous, and the space required for a continuously operating conveying appliance in a highly miniaturized test installation for screening work is therefore very small. This pump principle operates without a mechanical gear unit, and the required components of the pump head have no dynamic function, with the exception of the deflection of the diaphragm in the region of the shut-off and pumping chamber, so that precision manufacture is not necessary even for a miniaturized version of the pump components. There are no mechanical fault influences because of the absence of mechanical parts and the manufacturing costs for this reproducibly operating diaphragm pump head are minimized considerably. The pump requires only a supply of power and compressed air in order to be capable of operating; these supplies are present in any laboratory.

[0058] It is particularly advantageous to use the diaphragm pump for the metering of very small liquid substance quantities, of which the volume per pumping stroke is substantially below the specific drop size. By the pneumatic conveying energy being applied rapidly to the control side of the positive-displacement diaphragm of the pumping chamber, the sucked-in product volume in the pumping chamber is thrown out of the product space of the chamber and the outlet duct and there are no drops formed at the discharge point of the pump. As a result, a metering of small liquid quantities into a reaction mixture is not delayed in time and synthesizing is started in synchronism with the metering.

[0059] The metering of small substance quantities counter to pressure can be carried out very effectively, since the diaphragms of the shut-off chambers and pumping chamber are elastic and close the feeding and discharging product ducts in a gas-tight manner in the SHUT position of the chambers, so that no substance is forced back onto the inlet side of the pump via the outlet side of the pump head by way of the gas phase of a connected pressure vessel and suction under normal pressure is not interrupted.

[0060] A further advantage, as compared with the prior art, can be seen in that, by virtue of the small clearance volume and the leak-tight shut-off and pumping chamber, a sensitive product to be metered is supplied to the intended location without a long dwell time and remixing.

[0061] Particularly as compared with microstructure technology, there are advantages owing to the large duct dimensions in relation to the metering volume, and the pump is only slightly sensitive to contamination. A fault which is caused by product contamination and which is manifested by an increasing metering error or may lead to the failure of the metering of the pump is greatly reduced on account of the large product ducts. Product contamination can be flushed out, during metering, due to the relatively large product ducts.

[0062] The extremely low hold-up of the pump head and the small clearance volume ensure a good suction behavior and rapid reproducible metering, particularly in applications relating to new pharmaceutical substances which are available only in small quantities in the early development stage.

[0063] The setting of small metering flows is particularly simple, because, with the positive-displacement volume being constant, the metering quantity is set by means of an intermediate timer in the control. Volume flows can consequently be varied in a very simple way without cross-checking.

[0064] The lamella construction of the diaphragm pump with integrated controllable valves, which generates a pulsating metering flow by virtue of the pumping principle, makes it possible to equalize the metering flow by a multiplication of the positive-displacement unit and of the valves, the structural dimensions of the pump in the test installation not being appreciably increased.

[0065] Further operational advantages are afforded for the user in that the wearing parts which are in contact with the product can be replaced simply and cost-effectively.

[0066] The invention is explained in more detail below, by way of example, with reference to the figures.

BRIEF DISCUSSION OF THE DRAWINGS

[0067]
FIG. 1 shows diagrammatically the set-up of a pneumatic diaphragm pump constructed in a lamella manner, with an associated electropneumatic control unit and a programmable electronic control and also the connecting lines.

[0068]
FIG. 2 shows, by way of example, a diaphragm pump, in which depressions are worked in the middle plate and form the pumping and shutting-off chambers.

[0069]
FIG. 3 shows a pump head with separately inserted elastic diaphragms for each chamber.

[0070]
FIG. 4 shows an application in which a plurality of pumps are interconnected with a control unit.

[0071]

FIGS. 5, 5

a
show a double diaphragm pump with common plates.

[0072]
FIG. 6 shows a detail of a pumping chamber with a compensating volume in the control chamber.

[0073]

FIGS. 7, 7

a
show the arrangement and configuration of the groove or collecting duct in, for example, a pumping chamber.

[0074]
FIG. 8 shows a pump with chambers in the outer plates.

[0075]

FIGS. 9, 9

a
show versions of the diaphragm pump with chambers in the inner plate.

[0076] Referring now to the drawings, the diaphragm pump of the present invention is comprised of at least three plates, one of which is a middle plate (203) and two of which are outer plates (201, 205), the middle plate being disposed between the two outer plates, said at least three plates forming at least one pumping chamber (211), at least two shut-off chambers, said at least two shut-off chambers being a first shut-off chamber (210) and a second shut-off chamber 212), each of said pumping and shut-off chambers being in the form of a spherical segment, a spherical zone, a cylinder or a truncated cone; said middle plate being separated from each of said outer plates by two diaphragms (202, 204) which diaphragms also divide said pumping and shut-off chambers into control spaces (220, 221, 222) and product spaces (230, 231, 232), the product space (231) of the pumping chamber being connected to the product space (230) of said first shut-off chamber (210) by a first connecting duct (208) having an orifice (241) opening into said pumping chamber, and to the product space (232) of said second shut-off chamber (212) by a second connecting duct (209) having an orifice (243) opening into said second shut-off chamber, with an outlet duct (206) connected to the product space (232) of second shut-off chamber (212) through an outlet orifice (244), an inlet duct (207) connected to the product space of first shut-off chamber (210) through an inlet orifice (240); said pumping chamber (211) and shut-off chambers (210, 212), together with outlet duct (206) and inlet duct (207), first connecting duct (208) and second connecting duct (209) forming a passage duct through said pump, said control spaces (220, 221, 222) being connected to a control unit (100, 115) by control lines (119, 120, 121).

EXAMPLES

Example 1

[0077]
FIG. 1 illustrates a diaphragm pump 200 in cross section, with an associated control 100 and a control housing and also a pneumatic distributor 115. Electronic components and a freely programmable electric control are installed in the housing. A power feedline, not illustrated, serves for supplying voltage to the electronic components. The housing has a display 101, an on/off switch 102 and a plurality of function keys 103 to 109, by means of which required parameters for the pumping sequence or for the pumping operation can be entered, followed visually and stored. The electronic control 100 allows various operating variants, so that the pump can be switched to continuous operation by means of the key 103 and to discontinuous operation by means of the key 104. In particular, the discontinuous operation of the pump can be set by means of a preselectable number of pumping strokes and be stored in the control by means of the key 105. A reduction in the set parameters is provided by means of the key 106, and the key 107 is provided for increasing the variable parameters which can then likewise be stored in the control as newly selected operating parameters of the diaphragm pump by means of the key 105. In a continuous operating mode, the time constants can be varied by means of the keys 106, 107. The key 108 makes it possible to select between internal and external control of, for example, an external process management system. The pump 200 begins to operate when the key 109 is actuated, and when the key 109 is pressed repeatedly, the operation is stopped again. The electronics with the programmable control, at the start of metering, transmit via electric connecting cables 110 digital signals to the electropneumatic manifold valves 111, 112, 113, 114 which then switch into their defined open or shut position (Table 1). The electropneumatic manifold valves 111 to 114 are mounted on a pneumatic distributor block 115. Manifold valves as used in the present invention are manufactured for example at SMC Pneumatics Inc. The distributor block has two supply ducts 116, 117. The supply duct 116 is connected directly to the compressed-air supply, and the distributor duct 117 is connected to the vacuum supply by means of a vacuum line. The vacuum is generated by means of the vacuum generator 118, an injector, which is installed in the bypass and which is constantly supplied with compressed air by the valve 114 when the electric control is switched on. In a compact form of construction, the distributor block 115, together with the electropneumatic manifold valves and the vacuum generator 118, is located directly in the housing of the control 100, so that the compressed-air supply of the supply duct 116 is connected via a hose coupling 116′ and the pump head is connected via the hose couplings 119′, 120′, 121′. The freely programmable electronic components, diodes for the visual function indicator, an electric power pack and an electric circuit board are not illustrated in FIG. 1.

[0078] The freely programmable control of the pneumatically operated diaphragm pump 200 switches the electropneumatic manifold valves 111 to 114 and conducts the pneumatic pressure, prevailing in the distributor block 115, in the duct 116 (pressure duct) or the vacuum in the distributor duct 117 (vacuum duct) through the control lines (capillaries or hoses) 119, 120, 121 to the pneumatic control spaces (pneumatic spaces) 220, 221, 222 in the pump 200.

[0079] The valve 111 (V1) is connected by means of the control line 119 to the suction valve (lower shut-off chamber 210) of the diaphragm pump 200. According to the same layout, the other valve 112 (V2) (upper shut-off chamber 212) and the valve 113 (V3) are connected to the pumping chamber 211 of the pump 200. The valve 114 (V4) constantly supplies the vacuum generator with compressed air and is switched immediately as soon as the electronics are supplied with electrical voltage.

[0080] The diaphragm-pump head 200 consists of the three part-plates 201, 203, 205 and has inserted elastic diaphragms 202, 204 which are pneumatically deformable in the region of the pumping chamber 211 and shut-off chambers 210, 212. The diaphragms 202, 204 have the same area as the plates 201, 203, 205, in order to ensure good sealing-off in relation to the atmosphere. Introduced in the plates 201, 203, 205 are depressions which form the pumping and shut-off chambers 210, 211, 212. The shut-off chambers 210, 212 are worked here, for example, into the plate 201, and the pumping chamber 211 is worked with a small compensating-volume fraction in the plate 205 and with the larger volume fraction into the middle plate 203.

[0081] The shut-off chamber 210 designates, for example, the controllable suction valve of the pump head. Accordingly, the pumping chamber 211, the conveying chamber and the shut-off chamber 212 constitute the controllable delivery valve of the pump head.

[0082] The diaphragms 202, 204 divide the pumping chamber 211 and shut-off chambers 210 and 212 into control spaces 220, 221, 222 and into product spaces 230, 231, 232.

[0083] The pumping chamber 211 and shut-off chambers 210 and 212 are in the form of truncated cones. The middle plate 203 has a suction duct 207 and an outlet duct 206. The two ducts 206, 207 are in each case extended by a welded-in capillary. The ducts 209, 208 connect the product spaces 230, 231, 232 of the chambers 210, 211, 212 to one another.

[0084] The pumping chamber 211 has a groove 213 as a connecting element from the lowest geometric point of the depression in the plate to the outlet orifice or to the connecting duct 209. It also becomes clear that, between the inlet duct 208 and the start of the outlet duct 209 with the connecting groove 213, there is still a sufficient distance to make it possible for the orifices in the product space of the pumping chamber to be closed sealingly by the diaphragm 204.

[0085] The diaphragm pump 200 is shown here in the control step 4 (see Table 1). In the region of the shut-off chamber 210 (controllable suction valve), the diaphragm 202 is loaded with pressure on the control-space side 220, so that the diaphragm 202 shuts off the suction duct 207 at the inlet 240 (FIG. 2) and the connecting duct 208 at the outlet 241 (FIG. 2). In the region of the pumping chamber 211 (conveying chamber or positive-displacement unit), the associated control space 221 is loaded with a vacuum, so that the diaphragm region lifts off and opens the supplying and discharging connecting duct 208, 209. The shut-off chamber 212 is likewise loaded with a vacuum on the control side, so that the connecting duct 209 and the outlet duct 206 are opened, in order, in the following control step 5 (see Table 1), to displace the pump-stroke volume out of the pumping chamber. Necessary screws for pulling together the plates and at the same time pressing together the inserted diaphragms are not illustrated in FIG. 1.

[0086] The sequence of programmable control steps and the position of the valves 111 to 114 are illustrated below in Table 1. The digital signal “1” means that compressed air is prevailing (result: the diaphragm is pressed onto the plate 203 and closes), and the signal “0” means that a vacuum is prevailing (the diaphragm is raised in the control space and opens). As soon as the electronic control is supplied with electrical voltage and is switched on by means of the key 102, the programmed control switches the valves 111 to 114 into a defined starting or basic position. The control of a complete pump stroke consists here, for example, of five individual steps. When the pumping operation is interrupted or terminated, the control jumps into the starting or basic position.

1TABLE 1V3 (113)V1 (111)Positive-V2 (112)SuctiondisplacementDeliveryV4 (114)StepvalveunitvalveVacuumBasic position11111st step01112nd step00113rd step10114th step10015th step1101Back to step 1

[0087] In a control sequence, a variable timer is programmed (not illustrated in Table 1) after each control step 1-5, so that the individual control steps proceeding in succession do not influence one another and are executed completely. The switching times of the electropneumatic valves are longer and therefore substantially slower than the time required for transmitting the digital signals. By means of the intermediate timers, the pumping function is carried out reproducibly and completely according to the control cycle 1-5 (Table 1).

Example 2

[0088]
FIG. 2 shows a diaphragm pump similar to the pump described in FIG. 1, but the chambers or depressions 210′, 211′, 212′ are located in the middle plate 203′. The chambers 210′ to 212′ here have the shape of a spherical segment. It can be seen that the height of the vertex of the depression of the pumping chamber is greater than the thickness of the diaphragm. In this version, the center-to-center distance of the supplying and discharging ducts 207, 208 on the suction side of the pump (chamber 210′) from each other is greater than the center-to-center distance of the supplying and discharging ducts 209, 206 of the delivery valve (chamber 212′) from each other. As a result of the greater center-to-center distance at the suction valve, the sealing area of the diaphragm and the leak-tightness of the suction valve is increased and a backflow of the product during the pumping operation is prevented.

Example 3

[0089] In FIG. 3, there is a variant of the pump 200 from FIG. 2 with three separately inserted diaphragms 300, 301, 302. The depressions 210′, 211′, 212′ are all arranged on the inner plate 203′ and here form, with the diaphragms 300, 301, 302, the product spaces 230, 231, 232. With the product ducts open, the diaphragms 300, 301, 302 come to bear on the respective outer plates 201′, 205′. In the operating situation, these diaphragms are loaded via the control-space side with compressed air or a vacuum according to the control program via a bore, in order to ensure the pumping function.

[0090]
FIG. 4 reproduces, for example, the parallel operation of three diaphragm pumps 200a, 200b, 200c of the type shown in FIG. 3, in the non-activated state. These are connected in parallel to the lines of the pressure distributor 115 in a similar way to FIG. 1. The pneumatic manifold valves of the pressure distributor 115 are actuated by means of the electric control, not shown here, and bring about the actuation of the diaphragms via the control lines 119 to 121 which here are connected, branched off, to the three pump heads. When the pump heads operate in parallel with one control unit, care must be taken to ensure that the connecting lines and also the compressed-air and vacuum supply are sufficiently dimensioned.

[0091]

FIGS. 5 and 5

a
show a version of the diaphragm pump 200d in which two pump units or two pump heads have common part-plates. The part-plates are braced together by means of the screws 500. The essential contours, and also the pumping chambers and connecting ducts within the pump head, are illustrated by broken lines in FIG. 5a. The double pump head can be operated by means of one control unit, so that double the conveying quantity per stroke can be metered by means of one control stroke (corresponding to step 1-5; Table 1, FIG. 1). A further use is afforded when pumping chambers of identical or different size are introduced into the part-plates, so that two different substances are pumped synchronously by means of one control unit, or two control units for generating different substance flows are connected to the common pump head. The inner set-up of an individual pumping unit corresponds to the pump according to FIG. 5. FIG. 5a shows clearly that the projection of the outer contours of the shut-off chambers (501 and 502, 503) of the chambers overlap with various planes of the plates, in order to ensure a small clearance volume and thereby a good initial behaviour of the pump. Furthermore, a particularly compact pump-head design becomes possible.

[0092]
FIG. 6 shows, in cross section, two portions of the plates 203, 205 in the region of the pumping chamber 211 of a diaphragm pump similar to that of FIG. 1. The volume of the pumping chamber is distributed in equal proportion to both plates, so that the inserted diaphragm 301 is braced via a concentric sealing surface 214 and seals off the product space 231 and the control space 221 relative to the outside.

[0093]

FIG. 7, 7

a
shows a top view of the depression in a diaphragm pump in the form of a spherical-segment geometry of the pumping chamber 211. The groove 213 provided can be seen, which runs from the vertex of the pumping chamber as far as the connecting duct 209 and serves as a collecting duct for a complete emptying of the product space. FIG. 7a shows a further special version of a branched groove 213′ or of the collecting duct 213.

Example 5

[0094]
FIG. 8 shows the diaphragm-pump head 200 according to the invention, with a pumping chamber 211″ and two shut-off chambers 210″, 212″ and with the elastic diaphragm 202″ and 204″ inserted between the plates 201″, 203″, 205″. In this design variant, the diaphragm pump has depressions in the outer plates 201″, 205″ and the collecting duct 213″ is located in the plate 203″.

[0095] The inlet duct 207″, the connecting ducts 208″, 209″ and the outlet duct 206″ and also the collecting duct 213″ can be seen. This embodiment of the pump according to the invention requires a lower outlay in manufacturing terms.

[0096]
FIG. 9 shows a combined arrangement of the connecting ducts of the pump head. The middle plate is shown in a sectional illustration and the outer plates 201′, 205′ can be reduced due to the arrangement of the passage duct. The inlet duct 207′ and connecting duct 208′ between the pumping chamber and the suction-side shut-off chamber are introduced at right angles to the outer plate contour, so that the connecting duct 208′ is rectilinear and short. The clearance volume of the collecting duct 208′ is thereby minimized. The connecting duct to the delivery-side shut-off chamber has a greater length and a larger clearance volume. This version requires a third reduced plate 205′ for the set-up of the pump.

[0097]

FIG. 9

a
illustrates an optimized pump with a small clearance volume, the middle plate 203′ being shown in a sectional illustration. The geometric areas of the depressions of the shut-off chambers overlap partially or completely with the geometric area of the pumping-chamber depression, so that the connecting ducts from the pumping chamber to the shut-off chambers are extremely short and an optimized suction behaviour of the pump becomes possible.

[0098] In FIG. 9a, the connecting duct 209′ from the pumping chamber 211′ to the delivery-side shut-off chamber 212′ is positioned at the vertex of the pumping-chamber depression, so that the collecting duct (cf. FIG. 7) is dispensed with. The clearance volume of the pump is formed from the volume of the two connecting ducts 208′, 209′. The chamber volume of the suction-side depression of the shut-off chamber 210′ lies partially and the chamber volume 212′ completely in the shadow of the pumping-chamber depression 211′, so that, with the thickness of the middle plate 203′ being optimized at the same time, the connecting ducts 208′, 209′ are of extremely short configuration. The ratio of duct length 208′ to diameter is 3.5.

[0099] The resulting geometric areas of the depressions of the shut-off chambers on the respective planes of the plates lie partially or completely in the shadow of the formed geometric area of the pumping-chamber depression, so that the connecting ducts of the chambers and the clearance volume of the pump head are thereby reduced to an extreme extent.

Diaphragm pump

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CPC

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