Abstract: An apparatus and method for the direct measurement of corrosive sulfur and other corrosive compounds is provided. The method and apparatus of the current invention provides a rapid, reliable and cost effective method to directly measure the content of corrosive compounds in various fluids, and in particular liquid petroleum and liquid petroleum products such as gasoline. The apparatus can be retrofit to existing analyzers where they exist, or easily installed in locations that require such analysis.

Abstract: An apparatus for collecting and transporting chip-contaminated coolant, including a trough-shaped channel arranged underneath or between machine tools and a filter apparatus or a recirculating pump station, with at least one opening being provided in a lower region of the channel. Above this opening is at least one fluid outlet, which is configured such that coolant or another fluid streaming through this opening and the fluid outlet accelerates the transport of liquid and/or solid materials in the channel.

Abstract: The present invention provides a membrane filtration system (1) including: a filtering membrane portion (3) for removing impurities in feed water; a drain line (16) for draining a part of concentrate from the filtering membrane portion (3) to an exterior of a system; a concentrate return line (17) for returning a remainder of the concentrate from the filtering membrane portion (3) to an upstream side of the filtering membrane portion (3); a return flow rate adjusting portion (28) for concentrate provided in the concentrate return line (17); and a control portion (30) controlling the return flow rate adjusting portion (28) based on a drain flow rate of the concentrate or a flow rate of product water from the filtering membrane portion (3). With this construction, it is possible to suppress wasteful power consumption in a feed pump (7) for feeding water to the filtering membrane portion (3) and to prevent clogging in the filtering membrane in the filtering membrane portion (3).

Abstract: A disposable mass transfer system includes a source of dialysis fluid, a waste fluid reservoir, at least one semi-permeable tubular membrane residing in at least one fluid flow channel carrying a flow of a dialysis fluid, and a configurable pump and tubing. The pump and tubing may be configured to pump fresh dialysis fluid into the fluid flow channel, or may be configured to re-circulate partially spent dialysis fluid through the fluid flow channel. The fluid flow channel may be the interior of a flexible sealed reservoir, or may be a semi-rigid or rigid tubular enclosure.

Abstract: Embodiments of a filtration device, kit and method related to filtration in storm water systems are disclosed. A filtering device generally includes a mat adapted to filter water flowing through an inlet. The mat may have a top with a mesh cover, a main filtering portion and a bottom. The main filtering portion is formed of randomly-aligned fibers and a binding agent which impart a porosity that allows water to flow through generally unimpeded while sediment is filtered by the mat. A filtration kit is provided which could include the mat or other filtering device, a plurality of attachment members and a plurality of disks which allow for securing of the attachment members. Filtration device and kit are generally easy to install and clean, durable, less expensive than competing systems, and reusable.

Abstract: To provide particles for water disinfection which are hard to be suspended and are hard to be diffused in water which is suitable for use of disinfecting water and which are capable of developing disinfection effect fully and method of producing the same. Particles for water disinfection in which silver is coated on a garnet surface or a particle surface whose main ingredient is garnet are used. When said particles are used, preferable embodiment of silver is that the granular lumps of silver are carried continuously and discontinuously forming a group on a garnet surface as shown in SEM photographs of FIG. 4. Effective production method of such particles can be conducted by the electroless plating method in which garnet particles are immersed in a mixed solution composed of reducing solution in which at least any one of potassium sodium tartarate, glucose, or acetardehyde as a reducing agent is dissolved in water, silver nitrate solution, and ammonium solution.

Abstract: An aquarium which includes a tank having a pump and an under gravel filter disposed in the tank below the pump and a sediment removal system for collecting and removing sediment which passes through the under gravel filter. The under gravel filter includes a hollow bubble dispersing base plate having a perforated top surface and an overlying substrate. An air conduit is provided for introducing air into the pump. The pump is connected to the plate such as to pump water and air into the interior of the plate to thereby cause oxygenated water and bubbles to exit upwardly through the perforated top surface of the plate and into and through the substrate. The pump includes a free floating magnetic impeller. A rotational torque generating unit is provided to rotate the impeller. The rotational torque generating unit includes a magnetic drive disk and a motor for rotating the magnetic drive disk.

Abstract: The invention relates to a method of preparing spheroid polymer particles having a narrow size distribution by dispersion polymerization. This method comprises the steps of: providing a two-phase system in the form of a dispersion comprising an organic phase of droplets dispersed in an aqueous medium, mixing said organic phase in said aqueous medium under agitation without using a dispersion stabilizing agent to stabilize the dispersion, wherein the organic phase comprises at least a crosslinkable monomer, a polymerization initiator and an organic solvent for said monomer, and allowing the crosslinkable monomers to polymerize, while the two-phase system is agitated.

Abstract: A filter comprises at least one filtration unit with a filtration passage having an inlet and an outlet, wherein the filtration unit includes at least one groove formed in an inlet side surface of the filtration unit, said at least one groove extending to the inlet and dimensioned to hold back substances which may clog the filtration passage, by means of upper edges of said at least one groove. According to the present invention, by forming at least one groove in an inlet side surface of the filtration unit, the filtration passages of the filter can be effectively prevented from being clogged.

Abstract: The object of the invention is to provide a water-circulating sterilizer that uses no chlorine-base bactericidal agents, has no effect on the human body with no change of water quality, with no running cost and completely free from maintenance while effective sterilization is possible within shorter time. The invention provides a water-circulating sterilizer disposed in a pipeline of circulating water for sterilizing Legionella pneumophila surviving in circulating water, wherein plural sets of a first, second and third alloy plates are sequentially disposed from a water inflow port, the first alloy plate comprises an alloy containing at least copper and tin, the second alloy plate comprises an alloy containing at least silicon and titanium, and the third alloy plate comprises an alloy containing at least iron, molybdenum and manganese.

Abstract: An adjustable barrel-neck connector (10) for use in a filter press, comprising multiple interconnecting components (12,14,16) and operable to connect feed holes in first and second layers of filter media (20,22) through a feed passage in a filter plate (24), wherein the length of the connector (10) is adjustable to accommodate filter plates of different thicknesses. More specifically, first and second flanged end components (12,16) each include a plurality of inclined teeth (32), and a tubular connecting component (14) includes first and second pluralities of teeth (44,46) inclined in opposite directions. When each end component (12,16) is pushed onto a respective end of the connecting component (14), the plurality of teeth (32) of the end component (12,16) engage a respective one of the pluralities of teeth (44,46) of the connecting component (14) such that the relative inclinations of the engaged teeth (32,44; 32,46) prevent inadvertent separation.

Abstract: A filter and methods of manufacturing the same. In one embodiment, the filter includes a first scrim made from at least one thermoplastic material; a second scrim made from at least one thermoplastic material; and a middle layer positioned between the first and second scrims. The middle layer includes a dry-laid web of cellulose and opened, individuated staple bicomponent fiber. At least some of the bicomponent fiber in the middle layer is thermally bonded to at least some of the cellulose in the middle layer, and the first and second scrims are thermally bonded to the middle layer.

Abstract: A method for transferring and collecting waste material, especially food waste, in which method the waste material is transferred in a pipe system (7) portion-like from a feed station (1) to a collecting tank (9) and possibly onwards to further processing. Waste material is transferred in the pipe system with a pump device (8) which is arranged to the pipe system (7) between the feed station and the collecting tank, in which case the waste material passes through the pump (8).

Abstract: A method of treating wastewater, and more particularly stormwater runoff or domestic waste, wherein the wastewater is directed through a high carbon ash particulate. Contaminants such as phosphorus, nitrogen, BOD and COD can be removed. In addition, treatment of the stormwater runoff or domestic waste with ash will raise the pH of the wastewater, generally to above 10, killing bacteria contained in the wastewater.

Abstract: A method is provided for degassing a liquid. One step of the method includes providing a rotating packed bed (RPB) reactor. The RPB reactor includes a rotatable permeable element disposed within a chamber defining an interior region, at least one liquid inlet for infusing the liquid into the interior region, at least one gas outlet for removing a gas from the interior region, and at least one liquid outlet for removing a liquid from the interior region. The rotatable permeable element within the RPB reactor is caused to spin at a tangential velocity, and the liquid is then infused into the at least one liquid inlet at an inlet flow rate. Next, a vacuum is applied to the interior region of the RPB reactor via the at least one gas outlet to generate a liquid substantially free of the gas.

Abstract: A frit (44) includes a porous support structure having a plurality of void spaces, where a plurality of secondary particles (46) are filled in the void spaces, the secondary particles (46) being dimensioned with respect to the void spaces such that the frit (44) retains packing materials with diameters of less than about 2.5 microns. Preferably one or more frits (44) are received in a high pressure liquid chromatography (HPLC) chromatographic column, where the column includes fittings and filter assemblies for receiving frits (44) at its inlet and outlet. The frit (44) can be constructed from a porous support structure with void spaces or pores that are filled with secondary particles (46) smaller those used to manufacture the support. The particles (46) contained in the void spaces are large enough to be retained by the support, but small enough to create a finer network of interconnected channels within the support's void spaces that are capable of retaining sub-2.5 micrometer particles.

Abstract: A focusing unit for a fluidic system adapted for processing a mobile phase containing a fluidic sample, the fluidic system having a first processing element and a second processing element each for interacting with the mobile phase, wherein the mobile phase is to be conducted through the first and second processing elements, wherein the focusing unit is adapted for being coupled to an inlet of the second processing element and is adapted for modifying an elution strength of the mobile phase in order to spatially focus at least a portion of the fluidic sample in a region close to the inlet of the second processing element.

Abstract: An appliance using water including an incoming water valve is provided. The appliance also includes a sensor disposed in-line to an incoming flow of water received from the incoming water valve and is configured to sense a degree of hardness in the incoming flow of water. The sensor includes a substrate and a sensing element disposed on the substrate. The sensing element includes a sensing matrix, an indicator for one or more chemical species in a flow of water, and a selectivity component that reacts reversibly with the one or more chemical species in the water. The sensor also includes a light source configured to direct light through the substrate and the sensing matrix. The sensor further includes a light detector configured to receive transmitted light from the substrate and the sensing matrix and to generate a signal representative of selective wavelengths of the light indicative of the one or more chemical species in the flow of water.

Abstract: An ammonium removal system includes an ion-exchange medium, a brine source, and an electrophysical separation system. The ion-exchange medium may be used to remove ammonium from a waste stream. A brine may be flushed through the ion-exchange medium to remove the ammonium from the ion-exchange medium. The ammonium containing brine may be treated using an electrophysical separation system.

Abstract: Water filters systems for providing potable water including a combination of ceramic with anti-microbial embedded therewithin, and granular activated charcoal.

Abstract: A procedure and apparatus for the concentration of hydrophilic materials through flotation which consists of two devices operating in series. The first device performs the function of feeding the gas and the pulp, generate bubbles and produce contact with the hydrophobic particles to be concentrated. The second device performs the functions of separating and evacuating the froth carrying the hydrophobic materials and the evacuation of the aqueous pulp with the materials with water affinity. The gas-pulp mixing device contains inside it solid mixing means, preferably bead shaped and of a density lower than that of the pulp to be processed. The generation of bubbles and their contact with hydrophobic materials happen when the gas and the pulp transit through the interstices between the mixing media which have discrete freedom to move in the interior.

Abstract: This invention provides a method of removing toxic substances such as fluorine, boron, copper, lead, arsenic, hexavalent chromium, and cadmium from strongly acid wastewater safely and without fail. The method comprises the steps of (i) adding hydroxyapatite 11 to strongly acid wastewater 1A to precipitate its toxic substances as solid constituents, (ii) adding an alkaline substance 12 to the wastewater 1A to neutralize it, (iii) adding a coagulant 13 to the wastewater 1A to coagulate the precipitated solid constituents, and (iv) removing the coagulated solid constituents from the wastewater 1A. According to this method, toxic substances in the strongly acid wastewater 1A can be fixed, or immobilized, effectively and removed safely. Besides, because the strongly acid wastewater 1A can be treated at normal temperature without heating it in any step, the wastewater 1A can be treated safely.

Abstract: The disclosure is directed to methods of making and using a water treatment composition for improved water infiltration during irrigation of agriculture. These methods include combining additives with an aqueous fluid to create a treated irrigation water, wherein the additives comprise a preselected amount of a surfactant and a preselected amount of a displacement ion. The improved infiltration is obtained through a constant, or substantially constant, application of the treated irrigation water to the soil during the irrigation.

Abstract: A fluid is treated by coil assembly close to the fluid. An AC power is provided to the coil assembly. Current is conducted from the AC source in a first loop including a first switch during at least a portion of a first half-cycle of the AC power source. The first switch is opened during a second half-cycle and a subroutine of producing a first ringing pulse in the coil assembly and a second and subsequent ringing pulse is performed. The second pulse may be produced after or before the preceding pulse substantially decays. An apparatus for the method includes a controller configured to close the first switch and open the second switch during the first half-cycle and to perform the subroutine of closing and then opening the second switch during the second half-cycle to produce at least one ringing pulse of current in the coil assembly.

Abstract: A circulation system for bodies of water. In one set of embodiments for larger bodies of water, modified horizontal plate designs are provided at the entrance of the draft hose. The plate designs have sections that pivot downwardly as the flotation platform and depending draft hose are rapidly raised in high wave conditions to let the water escape downwardly out of the hose. Adaptations to the floats for the elongated arms of the platform are also made to essentially eliminate the creation of any damaging torques on them from high waves. Another set of embodiments are particularly adapted for smaller systems in municipal water tanks for thorough mixing of the water and treatment to kill undesirable ammonia oxidizing bacteria and prevent or at least inhibit their return.

Abstract: The invention relates to a desalination method and system that uses freeze crystallization technology that incorporates the use of compressed air energy as the source for freezing temperatures. When compressed air is released by a turbo expander, chilled air is produced as a by-product, wherein the chilled air is introduced into a crystallization chamber. Also injected into the chamber is a spray cloud of seawater droplets, which has been pre-chilled by heat exchange with the cold chamber walls, and which is then circulated and exposed to the chilled air in the chamber. The sizes of the droplets can vary, but are preferably predetermined, along with the relative temperatures, flows and speeds of the spray and chilled air, such that when the droplets are circulated within the chilled air, and settle at the bottom of the chamber, they are deposited at slightly above the eutectic temperature.

Abstract: A filtration system is provided with hollow membrane filter elements operable to remove solids, particulate and colloidal matter from a process fluid. Acoustic, vibration and ultrasonic energy may be used to clean exterior portions of the hollow membrane filter elements to allow substantially continuous filtration of process fluids. The filtration system may be satisfactorily used with process fluids having a relatively high concentrations of solids, particulate and colloidal matter.

Abstract: The present invention is an article for storing and supporting pots and pans that is simple to manufacture and assemble where the article is assembled without the use of tools or hardware, having at least two identical vertical members, and at least two identical horizontal shelves.

Abstract: The present invention discloses a display structure, comprising two vertical bars, two cross bars, a plurality of partition bars, and a plurality of partition parts to form a unit body. The short sides of the assembly panels on both ends of the partition bar are positioned into the gaps between the two wing panels in the vertical bar and then the partition bar is rotated to engage with the two clip grooves and the two wing panels, and a clip tenon is sandwiched by the two wing panels so as to form a plate-shape unit body. Further, the top of the partition part is snapped into the slide groove with the bottom of the partition bar protruding a partition panel such that the space between the partition parts is partitioned into accommodating spaces.

Abstract: A method for stably and easily exhibiting a flat plate-like article such as a flat exhibited article so as to be easily observed and less turned over and the flat plate-like article stably and simply exhibitable so as to be easily observed and less turned over and manufacturable at low cost. The flat plate-like article comprises two or more flat plate-like members and one or more connection parts.

Abstract: A shelf device for a cooler has a base member for a bottle to roll along by gravity feed. A guide member on the base member shifts the center of gravity of the bottle towards the base of the bottle to urge contact with a side panel so that the bottle maintains contact with the side panel and thereby roll in a straight path.

Abstract: A multi-function supporting rack includes a rack unit, a holding unit and a coupling unit. The rack unit has a fastening member at the top end and a hollow housing portion at the bottom end thereof. The holding unit is located on the fastening member to hold an article. The coupling unit has a latch member located in the housing portion and a connection member to couple the latch member and an equipment together. Such a design forms a greater supporting contact area between the latch member and the housing portion to provide an improved supporting effect. Moreover, once the latch member and the connection member are fastened to the equipment, the housing portion is coupled on the latch member. The finished assembly of the invention takes less space and installation is easier.

Abstract: A system for storing cylindrical containers includes multiple container guides positioned parallel to each other. In one embodiment, each container guide includes upper and lower track rails including left and right bearing surfaces and a track separator. The track rails guide containers placed on either side of the rails from a receiving area on the upper track to a dispensing area on the lower track. The lower track may include a concave depression proximate to the dispensing area that retains a first container at a lower relative position, thus enabling the first container to act as a stopping mechanism to subsequent containers placed in the system. The system may also include a frame that receives and supports the container guides and thereby provides one or more storage shelves capable of storing containers such as cans on a first-in first-out basis in a compact manner.

Abstract: A display rack having a support frame and at least one tray for holding and displaying product. Each tray attaches at its rear to the support frame by way of at least one moveable suspension arm and at least two possible tray-to-frame buttress points (or stops) for every suspension arm. The at least two tray-to-frame buttress points act together as a dual-position stop, which dual-position stop is capable of maintaining the tray in two different orientations with respect to the support frame. In a preferred embodiment, each tray has two L-shaped, pivoting suspension arms, where a portion of each suspension arm is horizontal and passes through a receiving channel in the support frame.

Abstract: The present invention is directed to a pallet storage system including a cart that rides on rails between an open or access position and a closed or storage position.

Abstract: The present invention is for an article for storing and supporting pots and pans that is simple to manufacture and assemble where the article is assembled without the use of tools or hardware, having a more than two identical vertical members, and more than two identical horizontal members.

Abstract: An object is to prevent cracking of a radiant heat preventing film which occurs near an opening area. A heat insulated container 10 produced by coating an external surface of a glass internal container 12 with a radiant heat preventing film 24, disposing the internal container 12 inside an external container 16 with a gap 14 interposed therebetween, heating an opening area so as to melt the same to thereby unite the internal container 12 with the external container 16, and evacuating the gap 14 to a vacuum, is characterized in that a region 26 not coated with the radiant heat preventing film 24 is provided in the vicinity of the opening area of the external surface. As a result, cracking does not occur in the radiant heat preventing film 24 at the time of heating and melting the opening area 18.

Abstract: A collapsible apparatus for supporting a container at an adjustable angle of incline to drain its contents includes a base, a shoulder support attached to the base for supporting a shoulder of the container, and a body support for supporting the container body above the shoulder. The shoulder support includes a pair of legs hingedly attached to the base at spaced apart hinge ends and joined at its opposite ends supported by a strut hingedly connected to the base, and spaced apart crosspieces between the legs to act as a shoulder stop. The body support includes a pair of arms hingedly attached to the base at spaced apart arm hinge ends and slidably attached to a body support member which is removably attachable at its ends to the shoulder support. The angle of incline is adjusted by slidably adjusting the distance between the arms.

Abstract: The invention includes optical signal conduits having rare earth elements incorporated therein. The optical signal conduits can, for example, contain rare earth elements incorporated within a dielectric material matrix. For instance, erbium or cerium can be within silicon nanocrystals dispersed throughout dielectric material of optical signal conduits. The dielectric material can define a path for the optical signal, and can be wrapped in a sheath which aids in keeping the optical signal along the path. The sheath can include any suitable barrier material, and can, for example, contain one or more metallic materials. The invention also includes methods of forming optical signal conduits, with some of such methods being methods in which the optical signal conduits are formed to be part of semiconductor constructions.

Abstract: A method of manufacturing an ink jet head which discharges ink, comprising: a step of preparing a silicon substrate; a step of forming a membrane having a layer in which a plurality of holes are disposed to constitute a filter mask, and a layer with which a first surface is coated in such a manner that the first surface is not exposed from the plurality of holes on the first surface of the substrate; a step of forming a close contact enhancing layer on the membrane formed on the substrate; a step of forming a channel constituting member on the close contact enhancing layer to constitute a plurality of discharge ports and a plurality of ink channels communicating with the plurality of discharge ports; a step of forming an ink supply port communicating with the plurality of ink channels in the silicon substrate by anisotropic etching from a second surface facing the first surface of the substrate; and a step of forming a filter in a portion of the close contact enhancing layer positioned in an opening of the in

Abstract: A fabricating method and apparatus of a thin film pattern improves the reliability of forming the thin film pattern by a resist printing method. The apparatus includes a print roller device of a roll shape around which a blanket is wound; a spray device located around the print roller device for spraying an etch resist solution to the blanket; and a print plate of an engraved shape where a groove of a desired thin film shape and a projected part except the groove are formed, and the etch resist solution has a surfactant inclusive of an ethylene oxide fluorinated polymer material.

Abstract: Laser-markable molding compositions, molding produced therewith and method of marking the same, wherein the molding compositions comprise: (a) at least one semicrystalline thermoplastic; and (b) at least one particulate additive selected from the group consisting of (i) light-sensitive salt compounds, (ii) inorganic oxides having an average particle diameter of less than 250 nm, and combinations thereof; wherein the light-sensitive salt compounds comprise compounds having two or more cations, wherein at least one of the two or more cations is selected from the group consisting of Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ag, Sn, Sb, La, Pr, Ta, W. and Ce; and wherein at least another of the two or more cations is selected from the group consisting of elements of periods 3-6 of main groups II and III, elements of periods 5-6 of main group IV, elements of periods 4-5 of transition groups III-VIII, and the lanthanoids.

Abstract: A method of plasma etching transition metal oxide thin films using carbon monoxide as the primary source gas. This permits carbonyl chemistries to be used at ambient temperature, without heating.

Abstract: A vacuum recloser including a first connection section adapted to connect to a first electrical conductor; a second connection section mechanically connected to the first connection section; and an arm connected between the first and second connection sections. The second connection section is adapted to connect to a second electrical conductor. The arm includes a vacuum bottle section with contacts that are movable into and out of contact with each other for respectively electrically connecting and disconnecting the first and second connection sections with each other. The arm is movable to electrically disconnect the vacuum bottle section from one of the connection sections.

Abstract: Liquid-filled high voltage switching units and electrical components including a primary tank and a secondary tank that do not communicate with one another in normal operation.

Abstract: An electrical switching apparatus is disclosed with a moveable insulating nozzle for blowing an arc. According to the invention, the insulating nozzle is connected in an interlocking and force-fitting manner to at least one moveable component part of the switching apparatus by means of a clamping device and without a screw connection. Exemplary embodiments relate, inter alia, to: a clamping hold of the insulating nozzle on the moving buffer cylinder and/or at the opposite end on a part to be moved, in particular a moveable shielding electrode or an auxiliary gear mechanism for a contact system, which is driven on both sides. Advantages include: simple fitting of the insulating nozzle, small physical volume of the clamping device; precise coaxial fixing of the insulating nozzle in relation to the switch axis.

Abstract: The gas-tight, high or medium voltage electric switch device (1), containing an insulating gas under pressure, comprises switch contacts (2) capable of occupying an open position and a closed position and disposed inside a composite insulator formed by a rigid tube (3) surrounded by an elastomer casing (4) whose outside surface defines a succession of annular fins. The rigid tube and the elastomer casing are arranged so as to define an observation window (7) that is at least translucent, and through which the open or closed position of the switch contacts is visible.

Abstract: An EDM wire having an outer coating of epsilon phase brass and a process for manufacturing the EDM wire is provided. The process includes coating a copper bearing metallic core with zinc. The zinc coating is then converted to epsilon phase brass by heat treating the wire at a temperature low enough to minimize or eliminate any resulting changes in the mechanical properties of the wire. The coated core wire may be drawn to a finish size prior to heat treatment which will result in a wire with a substantially continuous epsilon phase coating.

Abstract: A sintered electrode for electric discharge machining comprises a continuous phase consisting of a conductive region (3), and a dispersed phase consisting of microscopic polycrystalline diamond (2) dispersed in the continuous phase. The conductive region (3) is cobalt, nickel, cobalt nickel alloy or cemented carbide and imparts conductivity to the electrode (1). The microscopic polycrystalline diamond (2) imparts excellent mechanical strength and thermal diffusion to the electrode (1). The electrode (1) and the workpiece (5) are connected to a power supply (V1) in reverse polarity and a current pulse having ON-time of 60 ? seconds or less and 1 ? second or more and peak of 15 A or less and 1 A or more is supplied to the electrode (1) from the power supply (V1).

Abstract: The invention relates to a compensation cylinder unit that acts as a drive for the electrode arms of a welding device. The unit comprises a cylinder and at least two pressure chambers, which are sub-divided by a piston assembly and which can be alternately supplied with a pressurized medium by means of a valve assembly for controlling the drive displacement. According to the invention, the valve assembly comprises a proportional valve which can be controlled by a control unit, first in accordance with harmonized path signals that represent the position of the piston assembly and then by pressure signals that respectively represent the pressure in the pressure chambers, in such a way that the difference between the pressures that prevail in the pressure chambers in a predeterminable position of the piston assembly assumes a constant value that represents the weight compensation force of at least one electrode arm.