Method and apparatus for noise suppression in a fluid line

An expansion hose construction for reducing pressure pulsations in a hydraulic circuit, said expansion hose construction comprising:

• an outer hose having a first hose chamber on an inlet side with an inlet end adapted to receive the pressure pulsations from the hydraulic circuit and a second hose chamber on an outlet side with an outlet end;
• a throttle element between the first and second chambers;
• and
• an inner hose connected to one end of the outer hose inlet end and having a portion extending through the first hose chamber and the throttle element and a portion extending through the second chamber, the portions of the inner hose within the first and second hose chambers each having at least one radial throttle passage.

A fluid pressure wave motion attenuating device for transmitting a fluid under pressure between a pair of oppositely disposed fluid ducts comprising:

• a pair of couplings,
• a fluid conduit adapted to be fixed at its opposite end portions to said ducts through said pair of couplings with each of said couplings fixed to one of said end portions of said fluid conduit by means of a crimp hose-fitting,
• a flexible inner tube coaxially mounted in said fluid conduit and sized relative thereto to form a main conduit internally of said inner tube and to form an annular space between said fluid conduit and said inner tube,
• said inner tube being fixed at its opposite end portions to said pair of couplings,
• a restrictor in said annular space subdividing the same longitudinally into annular sub-spaces, and
• aperture means through said flexible inner tube each providing fluid communication between said main conduit and said annular sub-spaces between said fluid conduit and said inner tube on each side of said restrictor, whereby each of said annular sub-spaces serves as a fluid pulsation-absorption side-branch of said device.

An improved apparatus for reduction of fluid borne noise in a hydraulic system, said apparatus forming a passage and comprising:

• a first, a second and a third conduit member, said first, second and third conduit members having circumferential walls of predetermined internal bore diameters, said walls being formed of either a compliant material permitting volumetrical expansion of portions of said passage comprised therein in response to an increase in system fluid pressure therein or of a non-compliant material preventing such expansion;
• first and second radially perforate tuner flow members disposed internally respectively in said second and third conduit members and each having a bore and a pair of ends, one of said pair of ends of said first flow member being connected to a downstream end of said first conduit member and another end of said first flow member being connected to an upstream end of said third conduit member, one of said pair of ends of said second flow member being connected to a downstream end of said second conduit member and another end of said second flow member being connected to a downstream end of said third conduit member, said flow members having outside diameters smaller than said predetermined bore diameters of said first, second and third conduit members to define annular chambers respectively therebetween and to restrict flow of said fluid from said first conduit member to said second conduit member and from said second conduit member to said first conduit member, said flow members being perforate to allow fluid flow radially therefrom into surrounding space of said annular chambers defined between said conduit and flow members;
• first and second flow restrictor means disposed in said passage radially between said flow member and said conduit members and axially respectively at the downstream ends of said first and second conduit members;
• an input member connected to an upstream end of said first conduit member to permit introduction of a flow of fluid into said passage;
• and
• an output member connected to a downstream end of said third conduit member to permit delivery of said flow of fluid from said second tuner flow member to remaining portions of said hydraulic system.

In a method for reducing fluid borne noise signal components in hydraulic systems that includes the known steps of passing a flow of fluid through a first fluid conduit member to bypass alternating fluid flow components of a hydraulic signal, passing fluid from said first conduit member through a flow barrier via a reduced diameter flow member to impede further transmission of remaining alternating fluid flow components beyond said first conduit member, and passing said fluid flow from said flow member into a second fluid conduit member to remove further remaining alternating fluid flow components,

• the improvement comprising the further steps of:
• hydraulically coupling an output port of a pump to said first fluid conduit member to admit thereto a majority of alternating fluid flow components of a hydraulic signal issuing therefrom, said first member being constructed and arranged to be operable as a broadband filter for dampening by absorption a majority of the signal components;
• and
• subdividing such members by design and construction of tuning flow member means in said fluid conduit members in a predetermined manner such that the flow of fluid from said pump within said fluid conduit members substantially attenuates at least the first and second harmonic components of a pre-selected narrow band of frequencies of the alternating fluid flow components of said signal.