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John C Wickhart of Washington DC has appl ied for international and US

patents for a method and apparatus for performing alignm ent surveys on

overhead cranes .

Summary

The survey apparatus of the invention is alternately pushed or pulled by the

travelling crane. It consis ts of a wheeled carriage including s urveysightingtargets, s uch as pris ms, that are visible to survey personnel s tanding on the

ground. Using conventional s urvey instruments, data is collected for X, Y and Z

coordinates to generate, as required, a rail alignm ent profile, a rail elevation

profile, a rail span profile and a crane skew profile. These profilescan be used

to determine whether the crane confirms to alignment spe cifications. The skew

data can also be us ed to determine whether the crane itself may be misali gned.

Previous art

The apparatus of the invention is designed to work with a typical overhead crane

in which the crane spans a distance between two crane rails (Fig 1 - 1302) with

each rail s upported by girder which is, in turn, supported by a series of

columns. Thecrane contacts eachof the crane rails with an end truck with two

or morewheels (1316) at each end. The leading and trailing ends of each end

truckare terminatedwith a rail sweep (1314).

Fig 1 - Schematic si de elevation of a first exemplary rail survey carriage attached

to a crane rail sweepTypically the crane includes a trolley (Fig 4 - 1318) travelling between the two

end trucks on a pair of bridge rails, each with a bridge gi rder support. The trolley

will carry hoisting mechanis ms a nd load hooks (1324). Thus, as is usual, the

crane operator can move cargo between any two locations between the crane

rails.

Due to the large scale of typical industrial overhead cranes and heavy loads,

proper alignment of crane rails and crane wheels i s crucial to safe and efficient

operation. The invention cites ali gnment standards outlined in the Crane

Manufacturers Association of America (CMAA)'s specification 70 and AISE

technical report No 13.

Many types of conventional rail surveys involve time-consuming methods

requiring the rail to be locked out (turning off the power to the hot rail), with

survey personnel walking the length of the runway.

Fig 2 - Enlargem ent of rail s urvey carriage in Fig 1

As well as alignment other important factors include the pos itioning of the crane

end-truck wheels parallel to their respective crane rails , and/or assuring that the

drive motor output provided to the respective end-trucks is equivalent.

Imbalances i n the drive motor output can cause crane s kew even if the rail

alignment is within tolerances. Excess wear and tear on the rail and cranewheels w ill result requiring expensive repairs. Thus a s afe method for quick

and accurate collection of rail survey data, to find the root cause of

mis alignment problems , would be very beneficial.

Previous m ethods may include use of piano wi re for rail straightening, using a

tape meas ure to check the span between the rails. This method is not very

accurate and is very time consum ing. More accurate is the use of setting a

transit on the rail and s topping at various points to take readings by survey

Fig 4

Fig 1

Fig 2

Fig 3

Aligning overhead crane rails17 January 2008

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personnel, but measuring the span s till involves use of a tape measure.

Another instrum ent is required to check rail elevation.

Fig 3 - Schem atic side elevation of a second exemplary rail survey carriage

The inventor cites two earlier patents that are dedicated to the needs of

overhead cranes rather than train tracks. One US Patent (2005/011 1012 by

Steven Waisanen, publis hed May 26 2006) us es a self-levelling, remotely

operated laser s urvey device as a s tationery component, and a m obile

component with a screen and im age capture device. The laser emits a beam of

light towards the screen of the mobi le part as it travels the length of the crane

rail. The image capture device collects the data of the posi tion of the laser light

beam on the target and transmits to a remote computer. This data is used to

ass ess the alignment of the crane rail. Wickhart claims that Waisanen does not

provide details of claimed alternate embodim ents for crane rail configurations,but covers a bottom-running crane rail configuration.

US Patent Number 6,415,208 by Romauld Pojda, iss ued on July 2 2002, also

describes a sim ilar laser-bas ed device but configured to collect data for top-rail

crane configuration.

Waisanan claim s that these two patented devices suffer from s erious

deficiencies including reliance on comp lex combinations of electronics,

including mobil e operation in harsh environments likely to result in failure and

the need for specialised repairs . He also claim s that these devices are not

capable of providing sufficient information quickly and accurately to identify the

cause of mis alignment problems (on rail alignment information only in these

cases , with nothing on span alignment and elevation), and are incapable of

giving timely information on crane skew to identify and correct imbalances in the

drive m otors.

Total station

A typical total station (ET/EDM) (Fig 8 -1200) is used in conjun ction with the rail

survey carriage. It is moun ted on a tripod wi th a calculator attached including a

keypad and dis play, and is us ed to determine angles and dis tances to the

points being s urveyed, thus allowing the coordinates of these posi tions to be

calculated by trigonometry. This data can be downloaded to a computer and

application software used to generate a map of the surveyed area. The total

station may als o have a GPS interface.

Fig 4 - Ground view schem atic perspective of an overhead crane equipped with

rail s urvey carriage and electronic transit (ET)/electronic distance m easuring

(EDM) device or 'total station' positioned at dock level

The total station generates angle resul ts as digi tal read-outs, being more

accurate and less prone to errors due to interpolating between scale marks and

any misrecording. Readouts are also continuous s o angles can be reviewed at

any time. The use of reflecting prism s al so im proves accuracy in the laser EDM.

If a data recorder is used for downloading m easureme nt data and target

location codes it can als o reduce the potential for error.

When first switched on the total station may set itself to zero degrees (north), but

a control knob will allow this s iting to be reoriented by rotating the whole

instrument. Thus in this way the total station, or ET/EDM, can be us ed in

conjunction with the rail survey carriage to perform surveys of the crane.

Rail survey carriage

In Fig 1 a form of rail s urvey carriage (100) is s hown in s ide elevation attached

to a crane rail sweep. Included is an end rail bum per (1310) acting as a

collision damping mechanism in case the crane exceeds its designed

operating zone along the crane rails. This bumper can als o be used as s upport

for a carriage safety harness (1311) to prevent the rail survey carriage from

falling down.

Fig 2 shows an enlargement of Fig 1 s howing the rail s urvey carriage with a

body (102) that rides on the crane rail via survey carriage wheels (104). The

carriage is connected to the rail sweep via a swivel arm (106), or drive arm,

allowing the survey carriage to be moved selectively along the rail. The swivel

am is connected to the survey carriage body via a pivot post (108) extending

from a s urvey carriage hinge (110) and connected to the body by a hinge pin

(111). A force applied from the crane rail sweep to the survey carriage pivot post

is dampened by a survey carriage hinge s pring (112). At the other end the

swivel arm is attached to the rail sweep via a bracket (120) above the crane rail.

The rail survey carriage includes a pris m arm (126), extending in a direction

generally perpendicular to the crane rail, towards the oppos ite crane rail. At

least one pris m (122) is attached via a bracket (124) to the of the prism arm.

Additional prism s can be attached to facil itate sighting of at leas t one of the


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prism s by the total station.

The prism arm m ay also include pris m arm counterweights on the opposite

end of the prism arm to where the prism s are m ounted. Connections m ay be

bolted. The counterweights are selected to counterbalance the combined

weight of the prisms and prism arm . The combined weight of the assembly is

therefore centred over the centreline of the survey carriage body extending in a

direction parallel to the length of the crane rail.

The sighting target on the prism arm is mounted at a known offset relative to the

centreline of the survey carriage body.

The patent includes a detailed des cription of the components of the first

example of a rail s urvey carriage and an e xploded diagram of these

components. Com ponent features include outer circumferential flanges (105)

on the survey carriage wheels. The wheels may be tapered to aid centring ofeach survey carriage wheel pair, and hence the carriage body, on the crane rail.

Fig 3 shows a second example of a rail survey carriage in schematic side

elevation with s everal m odifications. These include s ingle s urvey carriage

wheels positioned at each end of the carriage body attached by a single axle.

The wheel rides directly on top of the crane rail. To ens ure that the carriage

remains aligned with the centreline of the crane rail, the survey carriage

includes carriage stabilising side-arms each with a stabilising wheel.

Suggested wheel material is polyurethane with a Shore Scale 9OA. The

stabilis ing wheels make tight contact with the side faces of the crane rail to

ensure centring. Each rotates about an axis to reduce friction and wear.

Another modifica tion is the con struction of the survey carriage s wivel arm or

drive arm. It includes s everal rigid m embers connected together at one of more

adjustable joints allowing adjus tment of the angles at the time of installation, for

example sections 206A, B and C in the diagram. The adjustable joints are

formed about a central hole (243) with several circumferential holes (245) in

one mem ber being connected and circumferential sl ots (247) formed in the

rigid plates of the other member being connected. With bolt connection this

allows the members to be rotated relative to each other to achieve the desired

angle.

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