GB2185730A - Power unit for excavator - Google Patents

Abstract

A power unit for an excavator, the excavator including a hydraulic power source thereon, a boom (6) and a dipper arm (8), comprises a housing (14) releasably mounted on the free end of the dipper arm (8) and containing a hydraulic motor powered from said source on the excavator and an electric generator driven by said hydraulic motor to provide an electrical output for powering an electrically-operated attachment such as an electromagnet (26) suspended from the free end of the dipper arm (8). <IMAGE>

Description

SPECIFICATION Power unit for excavator This invention relatestoa powerunitforan excavator, and more particularly to such a unit providing an electrical outputforpowering ancilliary equipment mounted on the excavator.

It is now well-established practice in the demolition industry to use excavators provided with various attachments, such as static ripper claws, hydraulic demolition poles, articulated hydraulic shears, concrete crushers, clamshell grabs and the like, for effecting the demolition process.

More particularly these attachments are commonly mounted in place of the conventional bucket on the end of the dipper arm which is itself articulated to the beam of the excavator, and are hydraulically operated from the control cab of the vehicle.

Thus the specialist equipment available for purchase by demolition contractors is quite extensive and such contractors invariably own excavators to which said ancilliary equipment can be attached.

There is also a need for demolition contractors to be able to handle the scrap, in particularthe metallic scrap, resulting from demolition processes.

However standard excavators are entirely hydraulic in their operation and have no inbuilt system capable of powering an electromagnet.

It is known to install this property in conventional excavators by providing a mechanical 'powertake off' in the form of a shaft driven buy a diesel motor and driving an electrical generator mounted on the vehicle chassis,the electrical supplysoprovided being fed to the control cab ofthe vehicle and thence to an electromagnet suspended from the dipper arm of the excavator.

However such an installation isa difficult and time-consumingtask, particularly in view of the limited space available in the engine compartment of the vehicle, and it will be appreciated that the cost of installing this capability into a contractor's fleet of excavators would run into several thousands of pounds.

Itwould be desirableto be ableto provide a power unit for an excavator which enabled the excavatorto be more readily adapted for scrap handling purposes than heretofore.

According to one aspect of the present invention there is provided a power unit for an excavator, the excavator including a hydraulic power source thereon, a boom and a dipper arm pivotally mounted on said boom,the powerunitcomprising a housing adapted to be releasably mounted on, at or adjacent the free end of, the dipper arm of the excavator, said housing containing a hydraulic motor adapted for connection to, to be powered by, the source of hydraulic power on the excavator, and an electric generator driven by said hydraulic motor to provide an electrical output therefrom.

It will be appreciated that such an arrangement utilises the available hydraulic source of the excavatorto produce a source of electrical power at the free end of the dipper arm without the necessity for additional costly and bulky equipment being installed on the chassis or cab of the vehicle and withoutthe necessity for electrical cables to be fed from the body of the vehicle along the boom and dipper arm thereof.

The power unit can be removably attached to the dipper arm in place of the conventional bucket orthe like, and can be readily linked into the existing hydraulic fluid circuit of the excavator to enable an electromagnet or other electrically-operated accessory mounted on the dipper arm to be powered from an accessible, adjacent source of electrical power.

Preferably the power unit includes one or more adjustable brackets mounted on the housing to enable attachment of the unit at or adjacent the free end of booms of different configurations.

According to a further aspect of the present invention there is provided an excavator comprising a wheeled or traced chassis, a control cab, a source of hydraulic power, a boom, a dipper arm, and a power unit releasably mounted on, at or adjacent the free end ofthe dipper arm, the power unit including a housing containing a hydraulic motor powered by said source of hydraulic power and an electrical generator driven by said hydraulic motor to produce an electrical outputtherefrom whereby an electrically-operated attachment mounted on the dipper arm can be powered by said unit.

In one embodiment of the invention, the excavator includes a hydraulic crowd ram mounted on the dipper arm and supplied with hydraulicfluid under pressure from said source, the hydraulic fluid supply to said crowd ram being diverted to, to drive, the hydraulic motorofsaid power unit.

Alternatively said hydraulic motor may be driven by hydraulic fluid fed thereto directly from said source.

The excavator includes means for controlling the supply of hydraulicfluid to the hydraulic motor ofthe power unit and for controlling the electrical output from the generator, said control means being such that, on switching off the supply of hydraulic fluid to the hydraulic motor, the electrical supply from the generator to the associated ancillary equipment is simultaneously switched off or reversed in polarity.

Preferably said control means include a pressure sensitive switch adapted to sense the pressure of the hydraulic supply to the hydraulic motor such that, on a reduction in said pressure associated with switching off of the supply to the hydraulic motor, said switch servesto switch off or reverse the polarity ofthe electrical supply from the generatorto the associated ancilliaryequipment.

Byway of example only, an embodiment of the invention will now be described in greater detail with referenceto the accompanying drawingsofwhich: Figures 1 shows part of an excavator to which is mounted a power unit in accordance with the invention, and Figure2 shows a power unit according to the invention in more detail, with the housing thereof partly cut-away.

Referring to the drawings there is shown part of a relatively conventional back-hoe excavator including a body part 2 mounted on a wheeled or traced chassis (not shown) and housing a diesel engine and a source of hydraulicfluid under pressure.

The body part 2 of the excavator carries a control cab 4 and has an elongate boom 6 mounted thereon for pivotal movement relative thereto, a dipper arm 8 being mounted on the free end ofthe boom 6 for pivotal movement relative to said boom. Hydraulic rams powered from the aforementioned source of hydraulic fluid and underthe control of control meanswithin the cab 4 react between the various components ofthe excavator in conventional manner, these rams including a crowd ram 10 the dipper arm 8which normally controls an excavator bucket pivotally mounted on thefree end of said dipper arm 8.

An excavator according to the invention further includes a power unit indicated generally at 12 and including a cylindrical housing 14 (part of which is cut away in Figure 2) provided with adjustable external brackets 16 permitting releasable attachment ofthe unit 12 to the free end of the dipper arm 8 in the manners illustrated in the drawings and in place ofthe more conventional bucket.

Conveniently the power unit 12 is further supported by the crowd ram 10 which is preferably fully retracted and therefore locked to effect said desired support.

Contained within the housing 14 are a hydraulic motor 18 and an electrical generator 20. A pair of divertervalves (not shown) are installed in the existing hydraulic supply flow and return lines to and from the crowd ram 10 whereby hydraulic fluid under pressure can be supplied to the motor 18 by way of input line 22 and returned to the source by way of outlet line 24.

Thus a controlled supply of hydraulicfluid can be fed to the motor 18 using the existing servo controls in the cab 4 which formerly operated the crowd ram 10.

The mechanical output from the motor 18 is linked to, to drive, the electrical generator 20 whereby an electrical output is provided from the generator in accordance with driving thereof by the hydraulic motor 18.

Thus it will be appreciated thatthis electrical power can befed to, for example, a traditional electromagnet 26 suspended from thefree end ofthe dipper arm 8 to energiseand de-energisesaid electromagnet 22 as required to pick up and drop ferrous scrap.

In orderto ensure that the electrical outputfrom the generator 20 is switched off or over as soon as the hydraulic motor 18 is de-energised, a pressure sensing device 28 is provided in the fluid input line 22 to detect a reduction in pressure associated with switching off of the motor 1 8through the servo controls in the cab 4.

This pressure sensing device 28 is linked with an eletrical control panel 30 connected to the generator 20, the arrangement being such that, when the device 28, which is normally in an 'off' condition, detects a fall in the pressure of fluid supply to the motor 18, a signal is transmitted thereby to the control panel 30 which, in turn, disconnects the generator output from the electromagnet 26 or reverses the polarity of the electrical supply to the electromagnet as required.

Thus itwill be appreciated that the compact unit so described can readily be attached to any conventional back-hoe excavator, and can easily be hydraulically connected into the existing hydraulic circuitry. The described unit can be interchanged by a contractor between any one of a number of different base machines, particularly in view of the adjustable nature of the brackets 16, according to the desired operating parameters.

Itis proposed that the divertorvalves and associated hydraulic lines 22,24, once mounted on an excavator, would remain thereon to enable the machine to be changed from the digging mode with bucket to the scrap handling mode very quickly.

The power unit 12 and control means therefor are such that the unit never operates outside predetermined safe working parameters, the unit being compatible with various electromagnets by being capable of providing a variable electrical output from a given hydraulicinputorfrom a varaible hydraulic input. The output from the generator may be alternating current or direct current.

Although described as utilising the hydraulicfluid available at the crowd ram 10, the motor 18 may be supplied with fluid from elsewhere on the vehicle, for example directly from the hydraulic source in the body part 2.

As well as, or instead of, powering on electromagnet, the described power unit can be used to power other electrically-operated equipment attached to or suspended from the dipper arm, such as drills and the like.

Other modifications and variations from the described arrangements will be apparent to those skilled in the art.

Claims (9)

1. A power unit for an excavator, the excavator including a hydraulic power source thereon, a boom and a dipper arm pivotally mounted on said boom, the power unit comprising a housing adapted to be releasably mounted on, at or adjacent the free end of, the dipper arm ofthe excavator, said housing containing a hydraulic motor adapted for connection to, to be powered by,the source of hydraulic power on the excavator, and an electric generator driven by said hydraulic motor to provide an electrical output therefrom.

2. A power unit as claimed in claim 1 and including one or more adjustable brackets mounted on the housing to enable attachmentofthe unit at or adjacent the free end of booms of different configurations.

3. An excavator comprising a wheeled ortracked chassis, a control cab on said chassis, a source of hydraulic power, a boom, a dipper arm pivotally mounted on said boom, and a power unit releasably mounted on, at or adjacent the free end of, the dipper arm,thepowerunitincluding a housing containing a hydraulic motor powered by said source of hydraulic power and an electrical generator driven by said hydraulic motor to produce an electrical output therefrom whereby an electrically-operated attachment mounted on the dipper arm can be powered by said unit.

4. An excavator as claimed in claim 3 and including a hydraulic crowd ram mounted on the dipper arm and supplied with hydraulicfluid under pressure from said source, the hydraulicfluid supply to said crowd ram being diverted to, to drive, the hydraulic motor of said power unit.

5. An excavator as claimed in claim 3 in which the hydraulic motor of the power unit is driven by hydraulicfluid fed thereto directly from said source.

6. An excavator as claimed in any one of claims 3 to 5 and including meansforcontrolling the supply of hydraulic fluid to the hydraulic motor ofthe power unit and for controlling the electrical output from the generator, said control means being such that, on switching off the supply of hydraulic fluid to the hydraulic motor, the electrical supply from the generatorto the associated ancilliary equipment is simultaneously switched offor reversed in polarity.

7. An excavator as claimed in claim 6 in which the control means includes a pressure sensitive switch adapted to sense the pressure of the hydraulic su pply to the hydrau lic motor such that, on a reduction in said pressure associated with switching off of the supply to the hydraulic motor, said switch serves to switch off or reverse the polarity of the electrical supply from the generator to the associated ancilliary equipment.

8. A power unit for an excavator substantialiy as described with reference to and as illustrated bythe accompanying drawings.

9. An excavatorsubstantially as described with reference to and as illustrated by the accompanying drawings.