Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B1/00—Multi-cylinder machines or pumps characterised by number or arrangement of cylinders
  • F04B1/12—Multi-cylinder machines or pumps characterised by number or arrangement of cylinders having cylinder axes coaxial with, or parallel or inclined to, main shaft axis
  • F04B1/26—Control
  • F04B1/30—Control of machines or pumps with rotary cylinder blocks
  • F04B1/32—Control of machines or pumps with rotary cylinder blocks by varying the relative positions of a swash plate and a cylinder block
  • F04B1/324—Control of machines or pumps with rotary cylinder blocks by varying the relative positions of a swash plate and a cylinder block by changing the inclination of the swash plate
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
  • F04B49/002—Hydraulic systems to change the pump delivery

Definitions

• Hydraulically driven Working Component such as a Hydraulic Piston-Cylinder Device or Hydraulic Motor
• the present invention relates to a loading machine which is eguipped with two pumps which function to supply hydraulic oil to at least one hydraulically operated working component, such as a hydraulic piston- cylinder device or a hydraulic motor having variable oil-pressure and oil-flow requirements, wherein the pumps can be connected one with the other for mutual coaction, when necessary.
• a hydraulically operated working component such as a hydraulic piston- cylinder device or a hydraulic motor having variable oil-pressure and oil-flow requirements
• Some loading machines of this kind are equipped with two fixed displacement pumps instead of one large pump of fixed displacement.
• Fixed displacement pumps how ⁇ ever, result in relatively large throttle losses and consequently a single variable displacement pump is used in some instances.
• a large variable displace ⁇ ment pump is required, however, the cost entailed is considerable and much higher than that entailed by two fixed displacement pumps intended for the same purpose.
• one of said pumps is able to produce a high hydraulic pressure and a small hydraulic flow, whereas the other pump is able to produce a lower hydraulic pressure and a larger hydraulic flow.
• the first pump is activated when a high fluid pressure and a relatively small fluid flow is required, and the second pump is isolated from the system, by coupling said pump to the tank.
• the second pump is also coupled to the system when a smaller hydraulic pressure but greater flow is required.
• Such requirements occur, for instance, in the case of relatively large loading ma ⁇ chines equipped with lifting jibs and a bucket or shovel, e.g. machines intended for loading gravel re o- ved from a gravel pit.
• inventive regulator device is constructed to sense a region of low flow and a region of high flow, and at the border between these regions to connect-up both pumps in the system when there is a need for greater flow, so that the two pumps together will achieve the desired greater flow of hydraulic medium in the upper flow region.
• the pump is preferably a variable displacement pump provided with a known load-sensing pump regulator.
• the pump will be provided with a load-sensing pump regula- tor equipped with a shunt valve. The losses experienced with a fixed displacement pump are reduced, by keeping the dimensions of the pump small in relation to the second, larger pump.
• Figure l illustrates a preferred embodiment comprising a variable displacement pump and a fixed displacement pump.
• Figure 2 is a more detailed illustration of the vari ⁇ able displacement pump used in the Figure 1 embodiment and the load-sensing pump regulator.
• Figure 3 is a detailed illustration of a double-acting piston-cylinder device connected in the system.
• Figure 4 illustrates the combination of a first fixed displacement pump and a second displacement pump, the pump regulator of the first pump being of a known kind and provided with a shunt valve.
• the reference numeral 10 identifies a variable dis ⁇ placement pump of, e.g., a known piston type, and the reference numeral 12 identifies a fixed displacement pump.
• the pump 10 is preferably much smaller than the pump 12.
• the pumps are driven by the engine 14 of the loading machine.
• the pump 10 is provided with a load-sensing pump regu- lator 16 of known design, as illustrated schematically in Figure 2.
• the pump conduit 18 of the pump 10 is connected to a hydraulically operated hydraulic component, such as a hydraulic piston-cylinder device 24, by means of a smoothly adjustable throttle-valve 20 and a working conduit 22.
• the working conduit 22 is connected by means of a conduit 22a to the pump regulator 16, which is set to a constant pressure difference PdP.
• Lying over the throttle valve is a pressure difference dP which is normally equal to PdP, the pump pressure P being equal to the pressure difference dP + the load pressure PL.
• this signal is utilized, in a simple manner, to activate the larger pump 12.
• the pump 12 is normally connected to the tank 26 via a smoothly adjus ⁇ table control valve 28 when said valve is in its open position.
• the other side of the valve is connected to a working conduit 22B in which the pressure PL prevails, and is also influenced on said one side by a spring F which produces a force which is slightly smaller than the force exerted by pressure dP.
• the other side of the valve is influenced by the pump pressure P in the con- duit 18, via the conduit 18a, 18b, i.e. PL + dP.
• the force PL + the spring force F will adjust the valve to its illustrated closed position.
• the pump 12 will then supply pressure oil through its pump conduit 30 and a check valve 32 to the pump conduit 18 so as to increase the flow through the throttle valve 20 to the hydraulic piston-cylinder device 24, therewith satisfying the higher flow demand of said device.
• the regulating device is a particularly simple device for achieving the desired result.
• first pump 10 is to be preferred
• the invention can also be applied in existing units which have two fixed displacement pumps, such as the unit illustrated in Figure 4 in which the first pump 34 is also a fixed displacement pump.
• the unit comprises, in a known manner, a pump regulator having a load-sensing shunt valve 36 which reacts to changes in the pressure difference dP across the smoothly adjustable throttle valve 20.
• the pump pressure P prevailing in the conduit 38, 38C acts on one side of the valve 36 and is equal to the load pressure PL prevailing in the conduit 22 plus the pressure difference PdP.
• the pressure difference PdP is set in the pump regulator with the spring F2, which acts on the other side of the valve, where the load pressure PL also acts via the conduit 22A.
• the shunt valve 36 and the trottle valve 20 form a variable-setting volume-flow regulator in a known man ⁇ ner. This arrangement, however, results in relatively large losses which can be reduced considerably in ac ⁇ cordance with the invention.
• a relatively small first pump 34 and the pump is combined with a larger fixed displacement pump 12 in the same manner as the variable displacement pump 10 of the Figure 1 embodiment is combined with the fixed displacement pump 12.
• the regulator valve 28 is switched to the illustrated closed position, similar to the Figure 1 embodiment, so as to couple both pumps to the system and reestablish the predetermined pressure difference across the valve 20, while increasing the flow to the hydraulic piston-cylinder device 24 at the same time.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Fluid-Pressure Circuits (AREA)
• Operation Control Of Excavators (AREA)

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Publications (1)

Family

ID=20376356

Family Applications (1)

Country Status (8)

Cited By (1)

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Citations (1)

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• 1989
  • 1989-06-21 SE SE8902253A patent/SE466560B/sv not_active IP Right Cessation
• 1990
  • 1990-06-19 EP EP90910156A patent/EP0478675B2/en not_active Expired - Lifetime
  • 1990-06-19 DD DD90341816A patent/DD297942A5/de not_active IP Right Cessation
  • 1990-06-19 WO PCT/SE1990/000435 patent/WO1990015931A1/en active IP Right Grant
  • 1990-06-19 DE DE69004961T patent/DE69004961T3/de not_active Expired - Fee Related
  • 1990-06-19 JP JP2509288A patent/JP2634321B2/ja not_active Expired - Fee Related
  • 1990-06-19 US US07/778,944 patent/US5165862A/en not_active Expired - Lifetime
  • 1990-06-19 ES ES90910156T patent/ES2046787T5/es not_active Expired - Lifetime

Patent Citations (1)

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