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Browse Prior Art Database

A B Port Digital Machine

IP.com Disclosure Number: IPCOM000200091D
Publication Date: 2010-Sep-27
Document File: 68 page(s) / 1M

Publishing Venue

The IP.com Prior Art Database

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This is the abbreviated version, containing approximately 5% of the total text.

Page 01 of 68

Digital A/B Port Machines

What are the real incentives for A/B port digital machines? 

- Makes the interface to conventional A/B port machines (pumps or motors) 

less complex compared to digital P/T port machines

• Eliminate directional valves
• Reduce the need for throttling valves for braking; however, some means of  dissipating hydraulic energy will still be necessary. (typical engines have limited 

braking torque: 5

                        require means to dissipate dynamic braking energy and protect the engine from  excessively high rotational speeds.

- Valve flow area can all be sized for 15‐20 Bar charge

Additional cycles possible. 

Depending on the valve arrangement, multiple part pumping or part motoring strokes are possible in one piston stroke - can add performance benefits to reduce flow or torque pulsations, increase flow or torque frequencies, and reduce the  cost of a machine verses the addition of more pistons/cylinders.

7kW/Liter at maximum speed); many hydrostatic vehicles still


Page 02 of 68

Prior Art ‐ System

• Two example patents disclose the A/B port machines in several system arrangements

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The P/T port machine layout has no way to discharge 

the HP accumulator, and no way to charge the LP

In the A/B port arrangements, the high pressure  accumulator is always connected to the load through a  'resolver' valve (always connected to the high pressure  line), and would receive fault (otherwise deadheaded)  piston flow -would cause unintended actuator motion  in the case of the hydraulic cylinder or conventional  hydraulic motor circuit. The accumulator 28 could be  included only for pulsation reduction as well as for  energy storage, but in either case, whatever energy  stored will contribute to conventional hydraulic  actuators' uncontrolled movement.

Ch i it th h i it f thi t

  e c

                c rcu   or  s arrangemen   should ideally include some energy storage  (accumulator, or even hose), to reduce energy losses  during idle. 


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arge c rcu


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Page 03 of 68

Valves -key enabler

• No matter the valve choice, ...