Abstract: A group of full-circumferential-flow pumps has a group of motors each comprising a main shaft, a rotor mounted on the main shaft, a stator disposed around the rotor, a cylindrical outer motor frame fitted over the stator, and an outer cylinder disposed around the cylindrical outer motor frame with an annular space defined therebetween, a group of pump parts oriented in opposite directions to meet different directions in which the main shafts of the motors rotate, and a group of frequency converters for energizing the motors to rotate at high speeds.

Abstract: An evaporative cooler pump is modularized to readily receive pump impellers and pump volutes of different shapes and dimensions in order to optimize the evaporative cooler water pump performance. The flow of water through the pump is streamlined to improve the efficiency of the pump.

Abstract: A positive displacement pump comprising a housing which defines a pump inlet chamber in fluid communication with a pump inlet port and a pump outlet chamber in fluid communication with a pump outlet port. Disposed within the housing is a wobble plate which is adapted to pump fluid from the inlet chamber to the outlet chamber. Selectively insertable into and removable from within the housing is a modular pump component. The modular pump component is adapted to modify the operational characteristics of the pump when inserted into the pump housing.

Abstract: A drywall tool filling pump includes a pump head removably attached to the top end of a pump cylinder positioned inside a bucket of drywall mud. Left and right hinge members extend from the pump head. A plunger shaft extends coaxially from the pump head. A lever has a proximal end pivotally attached to the top of the plunger shaft, and is positionable on either side of the pump head. A pair of connecting rods pivotally connect an intermediate portion of the lever to either hinge member. An output port arranged on the pump head may be connected to a variety of automatic drywall tools. A L-shaped mounting bracket has a top end attached to the output port, and extends downwardly for being positioned outside the bucket. A valve cap is attached to the lower end of the pump cylinder by bolts that extend through longitudinal slots on the cylinder, so that the valve cap may be easily removed by loosening the bolts, and sliding them out the slots.

Abstract: A hand air pump includes a cylinder having a chamber defined therein, a piston slidably received in the chamber and manually operable at a first end of the cylinder, and a spindle projecting outwardly from a second end of the cylinder and having a first air passage extending therethrough along a longitudinal direction thereof and having a first end in fluid communication with the chamber. The spindle further includes at least one annular groove defined in a mediate portion of an outer periphery thereof, a push pin formed on the mediate portion of the outer periphery thereof, and a second air passage extending therethrough along a diametrical direction thereof and having two ends in fluid communication with the annular groove and a mediate portion in fluid communication with a second end of the first air passage.

Abstract: A positive displacement pump comprising a housing which defines a pump inlet chamber in fluid communication with a pump inlet port and a pump outlet chamber in fluid communication with a pump outlet port. Disposed within the housing is a wobble plate which is adapted to pump fluid from the inlet chamber to the outlet chamber. Selectively insertable into and removable from within the housing is a modular pump component. The modular pump component is adapted to modify the operational characteristics of the pump when inserted into the pump housing.

Abstract: A lateral channel compressor having an annular flywheel housing (1) with air inlet stub (3) and air outlet stub (4). Attachments such as mufflers, filters, or safety valves are connected to stubs. A compact design and a lower manufacturing cost is achieved when the attachments are made in the form of a kit preferably having equal-length elements (I,II,III,IV) connectable directly to one another in the axial direction. The elements preferably have tubular main housings (11, 12) flush with one another. The filter and safety valve attachments (II, III, IV) each have a housing stub (13) projecting laterally from main housing (12) for mounting of filter elements and valve components.

Abstract: In a conveying pump having a cylinder introducible into a reservoir and having a pump piston, whereby the conveyed medium is supplied via an ascending line to a discharge line, an ascending line formed of two sections adjustable relative to one another is provided. The ascending line can be locked at different heights to vary the length of the ascending line so that the conveying pump can be used for reservoirs of different heights without deteriorating the conveying capacity of the pump. This adaptation can be performed easily and quickly. In addition, the conveying pump can be taken apart and easily cleaned, and component parts can be easily replaced.

Abstract: This disclosure relates to a variable length pipe assembly for connection between a pump-motor unit and a manifold. The assembly is particularly useful in a gasoline dispensing system of a service or filling station. The assembly comprises an inner pair of pipes and an outer pair of pipes. The pipes of the inner pair have telescoped portions and outer ends that are connectable to the pump-motor unit and the manifold. The pipes of the outer pair also have telescoped portions and outer ends that are connectable to the pump-motor unit and the manifold. The inner pair is mounted within the outer pair, a first passage being formed within the inner pair and a second passage being formed by the annular space between the inner pair and the outer pair. A seal is provided between the telescoped portions of the inner pair and another seal is provided between the telescoped portions of the outer pair, and a clamp is provided for securing together the telescoped portions of the outer pair.

Abstract: An elongated sleeve, externally threaded, is threadedly engaged with threaded bores in transverse walls formed in a straight cylinder of a gas compressor. A nut is secured to an intermediate portion of the sleeve, by means of a setscrew, and an end of the sleeve threadedly mounts a valve. The cylinder wall has an aperture formed therein to provide access for an open-end wrench, so that the wrench can work the nut to cause rotation of the nut and the sleeve, and move the valve outwardly or inwardly of the cylinder, as the valve is wholly confined within the cylinder at the frame-end thereof, and is otherwise inaccessible for movement.

Abstract: A positive displacement pump comprising a housing which defines a pump inlet chamber in fluid communication with a pump inlet port and a pump outlet chamber in fluid communication with a pump outlet port. Disposed within the housing is a wobble plate which is adapted to pump fluid from the inlet chamber to the outlet chamber. Selectively insertable into and removable from within the housing is a modular pump component. The modular pump component is adapted to modify the operational characteristics of the pump when inserted into the pump housing.

Abstract: A pump for use in a bath of reactive molten metal such as zinc has a graphite rotor, driven at constant speed, and capable of pumping molten metal at selective rates from the bath. The pump includes an internal delivery flow path and protected drive shaft, so that the liquid metal of the bath is not turbulated by the rotating shaft, and the temperature of the metal within the pump, during semi-quiescent periods is maintained substantially constant. The pump has a robust structure and yet can handle rates as low as 10 to 15 pounds per minute, in contrast to usual types of pumps that require pumping about 80 pounds per minute, and being speed controlled, are less accurate in their delivery rates. An adjustable control for regulating flow rate during operation also is provided.

Abstract: A roller pump for heart-lung machines with a pump head, consisting of a pump stator which possesses a pump bed serving as a support for a hose piece or length, and a pump rotor which is arranged in the pump stator so as to be rotatable about its central longitudinal axis and which possesses rollers rotatably supported on a roller carrier, which during a rotation of the pump rotor travel along the hose piece which is inserted into the pump head, and including a drive unit for producing the rotational movement of the pump rotor and with a pump housing for the support of the pump head and for receiving the drive unit which is inventively configured in such a manner that the drive unit is connected with the pump head whereby the pump head is moveable relative to the pump housing.

Abstract: An air pump comprises a head; an air guiding tube fastened at one end thereof with the head and at another end thereof with a two-way air admitting piston; a first cylinder fitted over the two-way air admitting piston such that the first cylinder can be caused to move back and forth; a first one-way valve disposed in the anterior end of the first cylinder; a second piston disposed in another end of the first cylinder; a first one-way valve permitting air to enter only the first cylinder; a second cylinder fitted movably over the second piston; and a second one-way valve disposed in the second cylinder to permit air to enter only the second cylinder which is fastened with the first cylinder without being able to move in relation to the first cylinder.

Abstract: A fluid rotary apparatus includes rotors accommodated in a housing, driving shafts on which the rotors are mounted, upper and lower bearings for rotatably supporting upper and lower portions of each of the shafts, fluid suction and fluid-discharging openings formed in the housing, motors adapted for independently and synchronously driving each of the shafts, rotation-detecting devices for detecting the rotational angle and/or the number of rotations of each motor, contact-preventing gears for contacting each other before the rotors contact each other, and a positive displacement pump structure section sucking and discharging fluid by utilizing a closed space formed by the rotors and the housing and controlling the motors in synchronous rotation thereof in response to signals outputted from the device.

Abstract: A strainer attachment for the inlet fitting of a submersible pump. A threaded rod carries two retainer elements, one of which is rigidly mounted on one end of the rod and the other of which is threaded onto the rod. With the rod held in a skewed position, the stationary retainer element can be passed through the inlet passage formed in the inlet fitting. When the rod is then oriented in alignment with the pump axis, the retainer elements span the inlet opening. When the movable retainer element is threaded toward the stationary element and against the inlet plate of the inlet fitting, the two retainer elements grip the inlet plate between them to secure the rod in place. A strainer body having mesh openings for straining the liquid that is being pumped can be threaded onto the rod.

Abstract: A portable, manually-operated water filtration pump for purifying water. The pump includes an inexpensive, disposable filter cartridge which can be easily changed when the filter elements are no longer effective. The pump uses a lever to actuate a double-acting piston. The lever is collapsible to one side of the pump for compact storage. The filter cartridge is a tubular cylinder having an inner bore forming the pump cylinder. A cylindrical mechanical filter is concentric with and adjacent to the inner bore to filter out particulates larger than 0.3 microns. A fluidized granular activated charcoal filter surrounds the mechanical filter to absorb chlorine and chlorine-related compounds such as herbicides and pesticides. The pump pumps filtered water into a bottle adaptor which will fit most standard water containers. A prefilter is provided to screen out large particulates from the pump to enhance the life of the filter elements.

Abstract: A feeding reservoir for a two-cylinder pump is provided for the pressurized delivery of thick matter. The feeding reservoir includes a material supply port, a front wall having two pump-side ports therein, and a back wall opposite the front wall having two outlet-side ports therein. The pump-side ports lead to the delivery cylinders of the pump, and the outlet-side ports lead to delivery lines. The outlet-side ports are each positioned diametrically opposite to a respective pump-side port, forming two port pairs. A swing pipe is positioned in the reservoir capable of swivelling alternately between one port pair to the other port pair to place the outlet-side port of a port pair in communication with the pump-side port of the port pair. The swing pipe is a straight through-way pipe. Self-adjusting sealing and wearing rings are positioned between the ends of the swing pipe and the pump-side and outlet-side ports for being pressed against the ports under delivery pressure.

Abstract: An improved evacuation pump system with dual inlet check valves uniquely designed to evacuate both lidded rigid containers and sealable flexible containers. A vacuum cup fixed to one end of a reciprocating piston pump attaches to the lid of rigid containers for their evacuation and a flexible probe connects to the pump for flexible container evacuation. To achieve this dual function two check valves mounted in the lower end of the pump are provided for the flexible container evacuation mode. One prevents discharge flow into the flexible probe and the other maintains suction in the cup to keep the pump attached to its supporting surface.

Abstract: A centrifugal or rotary double pump has a singular circular casing surmounting two motors driving individual rotors within the casing. Above a flat side of the casing is attachable to the device serviced by the double pump and receives an insert defining the inlet and outlet apertures and within the housing, defining two pump units each in conjunction with the respective rotor.

Abstract: A convertible and variable-length groundwater device permitting conversion of one type of groundwater sampling device to another, and vice versa. Conversion between a bailer device and a gas-drive pump, or a bailer device and a bailer pump, for example, is readily accomplished by substituting particular components from an assortment of universal, unique and multi-use components adapted to mate one with another and to be assembled substantially without the use of tools. Variable-length bladder devices, gas-drive pumps and bladder pumps are also provided, each being convertible between at least a single- and double-length assembly merely by adding or removing various components.

Abstract: This invention relates to an apparatus and method for adapting an existing air pump to also include a source of vacuum emanating from the same pump. An adapter plate is secured onto the face of the pump from which an outlet protrudes and an air intake is located. The plate is provided with ports in line with the output and intake openings in the face of the pump and such openings accommodate fittings of various pre-selected sizes to provide air pressure and vacuum for use in the field of respiratory needs of a patient. The ordinarily used input of atmospheric air entering the pump through an opening in the face of the pump is thereby converted to a vacuum source in the application to a patient of an aspirator unit, and the like.

Abstract: The invention relates to a compressor having a piston and rod assembly which is segmented to allow adjustment of the compressor's output. In particular, fasteners accessible from the top surface of the piston can be removed so that shims can be added or removed from piston rod. The addition or removal of shims lengthens or shortens the piston rod so that the compression ration can be fine tuned. These adjustments, as well as replacement of the piston seal, can be accomplished without extensive disassembly of the compressor.

Abstract: A double diaphragm pump is disclosed. The pump utilizes duckbill and ball-type check valves interchangeably. The check valves are held in place by intake and exhaust manifolds that are convertable to single or dual inlet or outlet manifolds.

Abstract: An ejector (10) is provided, which has an easily replaceable nozzle unit (22). The ejector includes a steam chest (16), a suction chamber (18), a diffuser (20) and a nozzle unit, wherein the steam chest has an outside end wall (24) having an opening with a removable cap (32) for removing the nozzle unit and for replacing the nozzle unit, or a duplicate thereof, through the opening. The steam chest has an axis and has a coaxial steam chest cavity (29) with an inlet opening (34) for steam. The suction chamber connects coaxially to the steam chest and has a coaxial suction chamber cavity with an inlet opening. The diffuser is coaxial with the steam chest and the suction chamber and has an elongate coaxial passage for exhausting the suction chamber cavity. The nozzle unit interconnects the steam chest cavity and the suction chamber cavity is coaxial therewith.

Abstract: A rotary pump mechanism is disclosed which comprises a coupling section that couples an impeller and drives the coupling section and, in turn, the impeller. The coupling section incorporates most of the components of the pump that wear out and are expensive. As a result, the impeller can be disposed of without disposing of other components. The coupling section can also be changed for continuous operation of a single impeller. Although the preferred application of the invention is in the area of pumping blood and other biological fluids, the disclosed invention has utility in any application where it is desirable to turn an "impeller-like" element.

Abstract: The invention relates to a two-cylinder piston pump with a pre-compression device for concrete, slurry, and the like material. This pump has the advantage over the pumps known in the art that the pre-compression unit (3) can be flanged on at the hopper (1) in any desired angle relative to the transport cylinders (4, 4').

Abstract: A portable sprayer has a container is provided with a threaded hole for selectively mounting to either a hand pump which pressurizes the interior of the container or an electric pump, which may be operated by batteries or a rechargeable accumulator, which delivers the liquid to the sprayer without pressurizing the container. The container is provided with another threaded hole for filling purposes. This hole can be closed by a leak-tight stopper, which is equipped with a valve or a pressure gauge if the hand pump is used, or by a simpler stopper if the electric pump is used.

Abstract: A water pump used in a cooling system for an internal combustion engine includes a pump shaft fixedly connected to an impeller means and detachably connected to a driven gear. The driven gear is in meshing engagement with a drive gear which is detachably mounted on a cam shaft rotated by the engine. The two shafts are not axially aligned, but are arranged in parallel relationship with each other. Thus, the optimum rotational ratio between the shafts may be obtained by adjusting the radii of the gears.

Abstract: The present invention discloses a groundwater sampling kit which comprises a plurality of components capable of being assembled into several alternative groundwater sampling devices by hand without the use of tools, the components being securely packaged in an impact-resistant carrying case.

Abstract: The invention provides a hand-operated pump for fluids in general, which comprises a body inside which a cylindrical hollow is provided, inside which a plunger is slidingly mounted, such a plunger dividing said hollow into a first variable-volume chamber and a second variable-volume chamber, said pump comprising unidirectional valve means which control the intake of fluid from the outside into said chambers, and the delivery of fluid from said chambers to the outside, said plunger being suitable to be reciprocatingly driven by means of an outer handle according to a to-stroke during which the handle is taken away from the pump's body, during said to-stroke fluid being intaken from the outside into the second chamber, and fluid being delivered from the first chamber to the outside, and according to a fro-stroke, during which the handle is approached again to the pump's body, during said to-stroke fluid being intaken from the outside into said first chamber, and fluid being delivered from the second chamber to

Abstract: A pumping system for shipboard use is comprised of a submersible centrifugal dewatering pump driven by a high pressure hydraulic motor mounted directly on the submersible pump, a hose means being connected from the hydraulic motor to a hydraulic pump located up on deck and arranged to be driven by an engine-driven standby fire pump. Quick couple-disconnect couplings are provided so that the pumping system can be operated in a dewatering mode, a fire fighting mode or a mode in which the pumping system supplies a source of power for operating various emergency power tools in holds or under water. Another pumping system has a discharge line from a fire pump arranged to drive a water motor mounted on a submersible pump for driving the same.

Abstract: Apparatus and method of improving the performance of a pump for pumping fireproofing material and the like viscous materials is disclosed wherein the pump is the type which includes a compression chamber (44) having an inlet (48) and an outlet (50). A piston cylinder (19) is disposed in fluid communication with the compression chamber and, a piston assembly (A, D, G) is carried in the piston cylinder driven in reciprocating suction and compression strokes. The piston assembly includes an extended piston (B,E) carried on a push rod (18) having a piston face (42, 61) terminating adjacent an inlet ball limit pin (52), having a reduced pin length of 5/16 inch, at the end of the compression stroke.

Abstract: A drive shaft and coupling adapter assembly for connecting multiple rotary machines to be driven in tandem in a predetermined direction by a single source of power having a rotating power take-off, each machine having a housing with aligned shaft bearings, and further including a common machine support disposed opposite the power take-off; a coupling adapter having a bore extending therethrough and one end of the bore having female screw threads therein and the other end of the bore being shaped to couple to the power take-off; and a drive shaft for each of said rotary machines, each shaft having a first end having male threads capable of engaging another shaft or the coupling adapter, and each shaft having a second end having female threads capable of engaging the male threads of another shaft, and each shaft being mounted in a machine and the shafts of the multiple machines being disposed in axial alignment and being screwed together to form a composite shaft and being screwed to said coupling adapter, and

Abstract: A compressor cylinder head assembly for a compressor which has a crankcase and a plurality of cylinders disposed in the crankcase. Each valve plate is spaced from the cylinder head by a valve plate gasket which is selected to have a thickness to provide the proper amount of clearance between the top of the piston and the valve plate to thereby keep the cylinder clearance in a predetermined range.

Abstract: A novel air compressor utilizing a simple modification of an opposing 4 cylinder air cooled Volkswagen internal combustion engine.

Abstract: According to the invention, a canister with bottom and peripheral walls defines an accumulation space for matter picked up by the vacuum. A lid is secured to the upper edge of the canister and seals the space. The invention resides in the provision of a canister extension whose bottom edge conforms to the top edge of the canister and bears thereupon. The extension can be secured to the canister permanently or removably in any known manner, as by sonic welding or the like. The lid in turn mates with the extension in the same manner that it mates with the open canister edge. Accordingly, the canister capacity is increased. Any number of such extensions can be employed depending upon the range of capacity sought. The invention also contemplates providing a plate bounding an impeller chamber than can be inverted to selectively accommodate different capacity impellers and different capacity motors.

Abstract: An air-operated reciprocating pump is designed for use with a wide variety of materials having widely varying viscosities. The pump has a stroke which is adjustable so that the piston can operate either entirely within the cylinder or can extend out the bottom end of the cylinder at the end of the stroke for materials having an extremely high viscosity. The stroke adjustment is easily accessible in the area between the pump and the air motor.

Abstract: An integral gas compressor-prime mover utilizes the prime mover power shaft (18) to drive a crank plate (20). The plate (20) includes a plurality of securing sites (40) among which a crank pin (24) is selectably securable for changing the stroke length of the reciprocating compressor piston (56). A crosshead connector asembly (32) is provided to linearize the motion of the crank pin (24).

Abstract: A positive displacement pump for slurries has a plunger reciprocating in a receprocation direction a plunger chamber. Gravity biased inlet and outlet valves control the egress and egress of slurries to the chamber. Special fittings between the valves and the chamber allow the valves to be oriented at one of four directions separated by 90.degree. angles so that the valves may be oriented so that flow is upwardly therethrough in any attitude of the plunger chamber.

Abstract: A supporting bracket for an electromagnetic clutch and a hydraulic pump driven through the clutch from a drive shaft, belt pulley or other power input by which the various forces exerted on the pump shaft by the clutch and power input are supported by the bracket thereby eliminating excessive wear on the supporting bearing structure for the pump shaft thereby prolonging the useful life of the hydraulic pump and maintaining the clutch components in properly oriented relation for proper and long lasting operation thereof.

Abstract: A reciprocating plunger pump having variable pumping modes is disclosed. A pump housing having an enclosed pump chamber provided with a valved inlet and a valved outlet is provided. A first plunger having a piston end extending into the pump housing and an outer end extending outside of the housing is driven in a reciprocal motion to produce a pumping action in the pump chamber. A second plunger having an inner end extending into the pump chamber and an outer end located out of the pump chamber is also mounted for reciprocal motion. The second plunger is removably attached to the first plunger. When the two plungers are attached together, a high pressure and low volume pumping of a fluid is achieved. When the two plungers are not attached together, a lower pressure and higher volume pumping of the fluid is achieved. Preferably, both plungers are substantially cylindrically shaped and the piston end of the first plunger is greater in diameter than the inner end of the second plunger.

Abstract: An oscillating displacement pump particularly adapted for pumping a viscous and abrasive fluid medium or one loaded with solid particles. The pump includes a connecting space located outside of a displacement unit and directly connecting a suction valve space with a pressure valve space so that the geodetic height of pumped medium increases. The connecting space defines a suction valve side connecting channel and a pressure valve side connecting channel connected at any given time with each other through the displacement unit space independent of the position of the displacement unit. The pumped medium can thus be moved through the pump from the suction valve to the pressure valve without diversion in a separate connecting space reducing abrasive wear on the pump. A number of additional advantageous features of the pump are disclosed.

Abstract: A hand pump that is operable selectively as a large volume low pressure air ump or a smaller volume higher pressure pump has a small diameter cylinder reciprocable in a large diameter cylinder and carrying a large diameter plunger and a small diameter plunger reciprocable in the small diameter cylinder. Wire bail type latches are operable to select the mode of pump operation upon reciprocation of the pump handle.

Abstract: A helicopter transportable mud pump made into three stages, each of which is separable from one another. Each pump stage is made into a lightweight sub-assembly which can be lifted by a helicopter into inaccessible locations. The adjacent crankshaft ends of the assembled pump stages are series connected in axially aligned relationship respective to one another by a special coupling and drive means. The coupling means is comprised of two coacting coupling members, each of which have confronting faces connected together in a manner to dispose the adjacent shaft ends of the multi-stage pump 120.degree. out of phase respective to one another. The coupling halves are identical in design so that only one member must be duplicated during fabrication of the device.

Abstract: A helicopter transportable mud pump made into three stages, each of which are separable from one another. Each pump stage is a light weight sub-assembly which can be lifted by a helicopter into inaccessible locations. The adjacent crankshaft ends of the assembled pump stages are series connected in axially aligned relationship respective to one another by a special coupling means. The coupling means is comprised of two coacting coupling members, each of which have confronting faces connected together in a manner that also causes the adjacent shaft ends of the multi-stage pump to be connected 120.degree. out of phase respective to one another. The coupling halves are identical in design so that only one member must be duplicated during fabrication of the device.

Abstract: Intravenous Fluid Pumping System having a controller and a pump controlled by the controller. The controller has a sealed chamber with a flexible membrane covering a portion thereof. An incompressible fluid is disposed in the chamber. A piston member is movable in the chamber causing extension and retraction of the membrane as the piston is moved in and out relative to the chamber. A motor is provided for reciprocating the piston. The pump has a pump body with a pumping chamber therein with one portion of the pump body being covered by a flexible membrane in contact with flexible membrane carried by the sealed chamber of the controller. The pump has an inlet adapter connected to the source of fluid. The pump also has an outlet adapter connected to the patient.

Abstract: A gas compressor drivably connected to an engine operates to supply compressed gas to a tank. The compressor has a housing including a commercial air cooled internal combustion engine block and cooling air system having a single cylinder chamber accommodating a reciprocating piston. The piston moves gas through a head and valve assembly connected to an air-to-air after cooler operable to cool and carry cooled compressed gas to a tank. The head holds the valve assembly on the cylinder. The valve assembly has a first valving ring allowing one-way flow of gas into the cylinder chamber and a second valving ring allowing one-way gas flow out of the cylinder chamber. A heat exchange unit is cooled with air moved by the commercial engine air cooling system of the compressor. The driving engine is of the same make and general type as used for the components of the compressor.

Abstract: A developing machine has a battery of vessels which receive metered quantities of liquid from discrete membrane-type pumping units. The pumping units constitute part of an apparatus having a single drive for the reciprocable membrane-deforming pumping elements of all units. The components of the drive for the pumping units as well as the pumping units themselves, are discrete modules which are rapidly connectable to or detachable from a single supporting frame. The drive has a rotary eccentric which transmits motion directly to the pumping elements of all pumping units. The strokes of the pumping elements are adjustable independently of each other.

Abstract: A carburetor comprising an accelerator pump having a working chamber containing fuel and a piston displaceable in the working chamber to discharge fuel therefrom to an inlet passage of the carburetor. A sleeve is secured to the carburetor housing at one end of the working chamber and the piston is slidably guided by the sleeve for movement into and out of the chamber. A sealing ring adjoins the sleeve and includes a free sealing lip directed into the chamber and sealingly bearing against the piston. In order to vary the amount of fuel delivered to the inlet passage for a given stroke of the piston, a piston and sleeve of different diameter are employed while the linkage mechanism between the throttle valve and the piston can remain without change.