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Industrial system with synthetically commutated variable displacement fluid working machine Disclosure Number: IPCOM000239042D
Publication Date: 2014-Oct-03
Document File: 61 page(s) / 5M

Publishing Venue

The Prior Art Database


An injection moulding system, water jet cutting machine or other industrial system has a synthetically controlled variable displacement fluid working machine which outputs hydraulic fluid to one or more fluid consumers, such as rams or hydraulic motors, through hydraulically stiff fluid retaining volumes and receives hydraulic fluid back from one or more fluid consumers through the same or other said hydraulically stiff fluid retaining volumes. Individual piston cylinder assemblies can be allocated to different outputs. There may be no valve between the machine and the consumers. A working chamber of the machine can be caused to undergo a motoring cycle to enable the machine to output more power than is received from a motor driving the machine. An accumulator can be used to provide a source of hydraulic compliance. The machine can be controlled using pressure control, flow control, feed forward control or variable power/variable power limit control.

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Industrial system with synthetically commutated variable displacement fluid working






Field of the invention


The invention relates to variable displacement fluid working machines (for example


radial piston). The invention is of especial relevance to fluid working machines for


use in hydraulically stiff industrial systems. The industrial system may be an industrial


machine to carry out industrial processes, typically understood to relate to a non-


mobile applications. Examples of such systems include injection moulding machines


(e.g. plastic), die casting, shredding systems using rotating shear, hydraulic ring


mains, drive pulley conveyors, balers, rubber moulding, sheet extruders, mud or grout


pumps, crushers, concrete block machines, compressor drives, large rotating


element power plant starting, various food processing machines, industrial presses,


forging presses, industrial rollers, industrial rolling machines/system, high pressure


water sources such as water jet cutting machines and water cleaning machines. Any


number of machines may benefit from a form of direct actuation. Industrial power


packs (also known as hydraulic power units - HPUs) may also require hydraulic


machines according to the present invention. Additionally aircraft systems, such as


using the invention for powering control surfaces, are also seen as a relevant

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application area.

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Background to the Invention


The invention relates to synthetically commutated variable displacement pumps in


which individual cylinders are electronically commutated and their displacement is

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selected by a controller. Such pumps are for example sold under the names Digital

Displacement® Pump or DDP® pump. The electronic valves (14,18,24) on each

cylinder (4) can be controlled such that, for every cycle the piston (6) reciprocates,

the volume of fluid pumped can be controlled (so called synthetic commutation /

synthetically commutated pump / and further below a synthetically commutated pump

/ motor). Each of these is an example of an electronically controlled displacement

selecting machine. Each cylinder (4) can be viewed as an independent pump and is

controlled independently. By combining the output of the cylinders in groups, a

service is created. If all cylinders in the pump are combined a single service is

created. For example, a synthetically commutated pump with 12 cylinders all

combined to a single service will have very high dynamic range of flow output and

very low output pressure pulsation. This same pump can have the output of the

cylinders arranged such that it has 4 services with 3 cylinders each, or in any other

combination. These cylinders may or may not all be on the same eccentric but would

ideally be equally spaced in terms of the mechanical angle between the cylinders.

These 4 services are completely independent even though they are packaged within

the same pump. Defining...