Beverage maker with pump noise attenuator

A beverage maker, such as a pump espresso machine, comprises a noise attenuator reducing pump noise. The noise attenuator has a housing with an inlet chamber receiving inlet flow from an inlet port, the inlet chamber having compliant walls permitting volumetric expansion. An outlet chamber in the noise attenuator housing has an outlet port and spheroidal walls. A flow-restrictor is disposed between the inlet and outlet chambers. An elastomeric insert in the housing forms the inlet chamber and at least part of the outlet chamber.

TECHNICAL FIELD

The present invention relates to beverage makers having pumps, and to noise attenuators for such beverage makers.

BACKGROUND OF THE INVENTION

Beverage makers, such as espresso machines, employ an electrically powered positive displacement pump for the delivery of water at relatively high pressure, for instance to a brewing chamber or for impelling flow through a boiler or heat exchanger. The pump casing has a bore in which a piston reciprocates, its stroke determining a working chamber, and typically with spring-loaded inlet and discharge valves. The piston may be driven at high frequency, as by magnetic induction. Due to its geometry, port timing, and speed, such pumps produce a flow ripple that excites pressure waves in the water. The uneven delivery of water flow is an inherent characteristic of such a pump that contributes primarily to the flow ripple. The pump excites water borne noise which is transmitted to valves, lines, boiler or heat exchanger and then to the structures to which those components are mounted. The structures then emit vibrations that create the greater part of the overall air borne noise emitted by the beverage maker. Therefore, there is need to reduce the water borne noise, as it is key to the reduction in the noise generated by the beverage maker. It is an object of the present invention to address this need or more generally to provide an improved beverage maker.

DISCLOSURE OF THE INVENTION

According to one aspect of the present invention there is provided a beverage maker comprising:

a pump;

a noise attenuator housing with an inlet port in communication with the pump, and an outlet port;

an inlet chamber in the noise attenuator housing, the inlet chamber receiving flow from the inlet port, the inlet chamber having compliant walls permitting volumetric expansion of the inlet chamber;

an outlet chamber in the noise attenuator housing, the outlet chamber having spheroidal walls, wherein flow from the outlet chamber passes to the outlet port, and

a flow-restrictor disposed between the inlet and outlet chambers such that flow conducted from the inlet chamber to the outlet chamber is restricted by the flow-restrictor.

The beverage maker may be an espresso machine, a tea or coffee maker, a machine for frothing milk, or the like. Although the noise attenuator housing is preferably separate from the pump or pump housing, it may be formed as a part of the pump or pump housing. The pump is preferably a positive-displacement pump.

Preferably a trapped volume of compressible material is provided in the inlet chamber which serves as a cushion volume. The water acts on the trapped volume of compressible material to absorb any pressure increases attributed to the flow ripple and subsequently expel such pressure increases as the system pressure attributed to the flow ripple decreases. Preferably the compliant walls of the inlet chamber are provided by an insert of resilient material, a cavity in the insert defining the inlet chamber, and wherein a void extends about the insert, between an outer surface of the insert and an inner surface of the housing to provide for expansion of the inlet chamber.

Preferably the flow-restrictor comprises at least one passage extending through the insert. To provide the flow restriction the cross-sectional area of the flow-restrictor is less than the cross-sectional area of the inlet port. The flow-restrictor is preferably a fixed flow restrictor as the differential pressure across the flow restrictor and system operating pressure are generally constant, however an adjustable flow-restrictor with an adjustable orifice that is selectably variable to control the size thereof could be used in the alternative to accommodate machines requiring pressure differentials and operating pressures.

Preferably at least part of the spheroidal walls of outlet chamber are formed by a concavity in the insert. Preferably at least part of the spheroidal walls of outlet chamber are formed by a recess in the housing.

Preferably the at least one passage extending through the insert comprises a plurality of passages extending through the insert.

Preferably an axis of each of the at least one passages extending through the insert is aligned with a concave face of the recess in the housing.

Preferably the insert has axially opposing ends, each end having a transverse face abutting the housing, and adjacent each annular transverse face a circumferential face abutting the housing. The transverse faces and circumferential faces are preferably annular, and serve to prevent axial movement of the insert, radial movement of the insert at the ends, and to seal the inlet and outlet chambers from the void.

Preferably the insert is formed from an elastomer, most preferably silicone.

Substantially reduced noise is produces by a beverage maker having a noise attenuator according to the invention. It is believed that there are two mechanisms that work to reduce such a ripple. The first is damping, whereby the resilient walls of the first chamber work as a damper to reduce the excitation of the ripple all frequencies. The second mechanism is pressure wave interference and cancellation. Besides being effective and efficient in operational use, by its modular and compact construction it can be readily used in a range of products The device may be economically constructed and has an overall simple design which minimizes manufacturing costs.

In another aspect the invention provides a noise attenuator for a fluid system comprising:

a housing with an inlet port in communication with the pump, and an outlet port;

an inlet chamber in the housing, the inlet chamber receiving flow from the inlet port, the inlet chamber having compliant walls permitting volumetric expansion of the inlet chamber;

an outlet chamber in the housing, the outlet chamber having spheroidal walls, wherein flow from the outlet chamber passes to the outlet port, and

a flow-restrictor disposed between the inlet and outlet chambers such that flow conducted from the inlet chamber to the outlet chamber is restricted by the flow-restrictor

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring toFIG. 1, a beverage maker10, such as a electrically-pumped espresso maker, comprises a water tank12from which water is drawn through a suction pipe14by a pump16, such as a reciprocating piston pump driven by magnetic induction. The pump delivers water through conduit18to the noise attenuator20, from which it then passes via conduit22to a thermoblock24(comprising a combined boiler and heat exchanger). A solenoid-operated three-way valve26determines whether the pressurised output is directed through the boiler for discharge through the nozzle28, or through the heat exchanger for discharge through an outlet30below which the porta-filter31may be fixed. The drawing is merely illustrative of one type of beverage maker to which the invention is applicable.

The general construction of the noise attenuator20is best seen inFIG. 2. A principal component of the noise attenuator20is its housing30, which as shown may be assembled from first and second shells30a,30bcoupled together by screw fasteners32and nuts34. The shells30a,30bmay be of substantially rigid moulded polymeric construction. Flanges36,38are provided with apertures for receiving the screw fasteners32and an O-ring40seals the shells30a,30btogether in a fluid-tight manner. Disposed internally in the housing30is an elastomeric insert42, most preferably made from a silicone elastomer.

An inlet port44in the noise attenuator housing30is in communication with the pump16, and an outlet port46is connected to the conduit22.

The insert42has axially opposing ends, each end having a transverse face46a,46bof annular form which abuts a complementary face of the housing30. Adjacent, and generally perpendicular to each of the transverse faces46a,46bis a respective circumferential face48a,48balso abutting a complementary face the housing. The transverse faces46a,46band circumferential faces48a,48bserve to prevent axial movement of the insert42, and radial movement at the ends of the insert42.

The insert42has a substantially cylindrical external surface50, coaxial with a substantially cylindrical internal surface52on the housing30, defining a void54between the insert42and the housing30. The engagement between the housing30and the transverse faces46a,46band circumferential faces48a,48balso seals the void54against water ingress.

A cavity in the insert42proximate the inlet port44and the walls of the housing adjacent the inlet port44together define an inlet chamber56, having walls58of a diameter substantially larger than that of the inlet port44. The resilience of the walls58and the void backing them permit volumetric expansion of the inlet chamber56.

A flow-restrictor formed on a web60extending internally in the insert42, comprises four passages62extending through the insert. The web60is planar, arranged transverse to the long axis A of the insert42, and is relatively thinner than the walls58. The cross-sectional area of the four passages62is less than the cross-sectional area of the inlet port44to provide the flow restriction. The flow-restrictor formed on a web60separates the inlet chamber56from an outlet chamber64, such that flow conducted from the inlet chamber56to the outlet chamber64is restricted by passing through the passages64.

The outlet chamber64has spheroidal walls, and flow from the outlet chamber64passes out of the noise attenuator20via the outlet port46. By appropriate selection of the size of the spheroidal outlet chamber the device and be tuned to the frequency, or frequencies excited by the pump16. In the illustrated embodiment the longitudinal axis A of the insert extends centrally through both chambers56,64. Axes of the inlet and outlet ports4,46may be generally orthogonal to provide a compact noise attenuator, readily able to be plumbed into different beverage makers. Generally half of the spheroidal walls of outlet chamber64are formed by a concavity in the insert42, and half by formed by a recess in the housing30, the joining plane between the shells30a,30bbisecting the outlet chamber64at its widest section. The axes66of the passages62through the flow restrictor are aligned with a concave face70of the second chamber64, specifically on the shell30b.