US3770136A

US3770136A - Overhead cranes

Info

Publication number: US3770136A
Application number: US00193645A
Authority: US
Inventors: H Fischer
Original assignee: Clarke Chapman John Thompson Ltd
Current assignee: Clarke Chapman Group Ltd
Priority date: 1970-11-03
Filing date: 1971-10-29
Publication date: 1973-11-06
Anticipated expiration: 1990-11-06

Abstract

An overhead crane has two lifting drums rotating simultaneously to lift a load, the drive to the drums being in the form of a closed kinematic chain in which that part normally running idle includes a gear wheel mounted so that its axis is displaced when load is transmitted through it due to a failure in the other part of the chain. Said displacement operates a warning circuit whereby an indication of the failure is provided while the drive continues to be transmitted through said gear wheel.

Description

United States Patent Fischer 1 Nov. 6, 1973 15 1 OVERHEAD CRANES 3,004,445 10 1961 Mondon 74 411 x 3,086,402 4/1963 Erard [75] lnventor: Herbert Fischer, Wolverhampton, 3,175,110 3/1965 Kohlhagen England 3,244,020 4/1966 Breuer 74 411 1 1 Assignool l r p -J Thompson FOREIGN PATENTS OR APPLICATIONS Gaieshead, Cmmty 1,226,267 10/1966 Germany .1 212 21 Durham, England 281,051 12/1964 Netherlands 212/21 [22] Filed: Oct. 29, 1971 Primary Examiner-Ev0n C. Blunk [2]] Appl' 193,645 Assistant ExaminerJames L. Rowland Att0rneyErnest A. Greenside [30] Foreign Application Priority Data Nov. 3, 1970 Great Britain 52,204/70 [57] ABSTRACT Nov. 10, 1970 Great Britain 53,452 70 An overhead crane h w lifting drums rotating simultaneously to lift a load, the drive to the drums being [52] US. Cl. 212/10, 74/41 1 in the form of a closed k nem i hain in which that [51 1 Int. Cl B66x 17/00 p r normally unn ng idle includes a gear wheel [58] Field of Search 212/10, 11, 1822; mounted so ha i xi is displaced'when load is trans- 254/184; 74/41 1, 406; 192/150 mitted through it due to a failure in the other part of the chain. Said displacement operates a warning circuit [56] Referen Cit d whereby an indication of the failure is provided while UNITED STATES PATENTS the drive continues to be transmitted through said gear 1,606,106 11/1926 Shutt 212 22 wheel 2,702,995 3/1955 Biedess 74/411 X 9 Claims, 3 Drawing Figures SHEET 1 BF 2 PATENTEUNM 6 1973 OVERHEAD CRANES This invention relates to overhead cranes.

Where overhead cranes are intended for lifting heavy and potentially dangerous loads, for example, ladles containing molten steel, two basic qualities that are especially important are reliability and availability.

Reliability includes the adequacy of the design to ensure the function and performance of the crane without failure, and this is a quality which every crane is expected to'possess as a matter of'course. However, there is no absolute reliability, and failures can occur.

A crane will possess a maximum of availability if maintenance and breakdowns cause a minimum of interference in the required duty of the crane.

Commonly an overhead crane intended for lifting a heavy load, such as a hot-metal ladle, is provided with two lifting drums, or two series of lifting drums, each drum or series having one of two ropes or two series of ropes, each of the two ropes orseries of ropes being attachable to opposite sides of the load.

It is known to provide an arrangement in which the two drums or series of drums (for convenience of description, this specification will refer to two drums, one for each lifting rope), the driving motor or motors (there may be one motor driving both drums, or each drum may have its own driving motor) and the gears form a closed kinematic chain or circuit. This includes two intermediate spur gear wheels, or a multiplicity of pairs of such wheels, between the drum spur wheels, and although these intermediate spur wheels are in loose mesh, one with another, they are unloaded during normal operation of the crane.

The failure of any part of this chain or circuit (other than the spur gear wheels on the drum) still maintains the connection between the motor or motors and the rope drums, since the intermediate spur wheels become loaded and their teeth move into bearing contact, so that the two drums can continue to operate, both drums being driven through one and the same path round the kinematic chain or circuit, which path does not include the failed part. When two driving motors are used, one for each drum, both drums can be driven by one motor if the other motor fails. Thus, there is provided a safety means which will prevent the load falling in the event of any such failure.

However, hitherto it sometimes has been difficult for the crane operator to know that a failure in the said circuit has occurred, because the crane continues to operate the load, apparently normally. The object of this invention is to provide means for indicating to the operator that such a failure has occurred.

According to this invention, in a drive means for at least one pair of rope drums of a crane, said drive means being in the form of a kinematic chain and comprising intermediate gear wheels forming a part of said chain between gear wheels rotatably secured to said pair of drums, one of said intermediate gear wheels is arranged to mesh with respective gear wheels at substantially diametrically opposite regions of said one gear wheel and is mounted so as to be displaceable substantially perpendicularly to the diametrical plane between said opposite regions, means being provided to operate a warning device when the application of a torque load to said intermediate gear wheel displaces it in said direction.

Thereby, in the event of a failure in the drive to one of the said rope drums, the load, or part of the load, will be transmitted through the intermediate gear wheels, and the axis of said one intermediate spur gear wheel will be displaced towards one or the other of its end positions and cause the said warning device to be operated.

The invention will be more particularly described with reference to the accompanying drawings FIG. 1 is a diagrammatic plan view of an overhead crane showing the drive arrangement to a pair of rope drums of the crane; and

FIGS. 2 and 3 are similar diagrammatic elevations of the crane of FIG. 1, showing the assembly of rope drum spur gear wheels and intermediate spur gear wheels, and incorporating alternative forms of the invention.

In FIG. 1 there can be seen trolley 2 of the crane having wheels 3 mounted on a gantry structure 4 of the crane along which the trolley performs cross-transverse motions under the action of respective drive means 6. The structure 4 is itself able to transport the trolley in longitudinal traverse motions but the drive means for this purpose is not illustrated as the manner of traverse drive of gantry cranes is well known in the art and does not form any part of the novelty of the present invention.

On the trolley 2 are mounted two rope drums 11 and 12 on

respective shafts

13 and 14 and the shafts have

respective gear wheels

15 and 16 secured to them. The gear wheel 15 is driven by a motor 17 through reduction and other gearing 18, a shaft 19 and a pinion 20, the pinion 20 meshing with the gear wheel 15. Similarly, the gear wheel 16 is driven by a motor 21 through reduction and other gearing 22, a shaft 23 and a pinion 24, the pinion 24 meshing with the gear wheel 16.

The two

motors

17 and 21 are interconnected by a shaft 25.

Between the two

drum wheels

15 and 16 there is a pair of

spur gear wheels

26 and 27 which are in mesh with each other and with the

gear wheels

15 and 16, respectively.

Braking devices

28, 29, 30 and 31 are provided at required positions in the drive transmission.

This arrangement provides a closed kinematic chain or circuit. In the event of the failure of any part of the circuit, other than the two

drum gear wheels

15 and 16, the two. drums can still be driven by one or both of the

motors

17, 21, the drive transmission path being clockwise or counterclockwise in the circuit, depending upon the position of the failed part. In such an event, the two intermediate

spur gear wheels

26 and 27 will become loaded.

In FIG. 2 there is shown the assembly of the

gear wheels

15, 26, 27 and 16, and

pinions

20 and 24, the

gear wheels

26 and 27 being in loose meshing engagement, or normal tooth-contact meshing engagement with each other and with the

gear wheels

15 and 16. Between the bearing 32 of the journal of the gear wheel 27 and the support in the frame 10 for the bearing, there is provided a slot 33 which is perpendicular to the diameter of the wheel 27 joining the positions of meshing of the wheel 27 with the two

wheels

26 and 16; in this illustrated example said perpendicular attitude is vertical.

Thus, in the event of the load, or part of the load being transmitted through the

wheels

26 and 27, the load on the wheel 27 will move it bodily up or down, depending on which direction the load passes, in the vertical path indicated by the

arrows

34, 35, and the bearing 32 will move to the top or bottom end of the slot 33 where a limit switch 35, or other switching device, will be located and will close an electric circuit containing an audible or a visual warning device 36. The movement is limited in extent so that the wheel 27 is not displaced out of mesh with the wheels l6 and 26 as it transmits the drive between the

adjacent wheels

16 and 26.

FIG. 3 shows an alternative arrangement to that in FIG. 2. In this example, the bearing 32 mounted in an elastic collar or bush 37 so that when the load or part of the load is transmitted through the

wheels

26 and 27, as hereinbefore described, the collar or bush will be compressed to allow the wheel 27 to move up or down.

What I claim and desire to secure by Letters Patent IS l. in a crane having at least one pair of rope drums in turn having gear wheels linked by a kinematic gear chain including a series of cooperating elements, the improvements consisting in that said kinematic gear chain is a closed circuit kinematic chain drive having two series of components on opposite sides of and interconnected by a coupling shaft, each series of components, beginning at a point most distant from said coupling shaft and in a direction toward said coupling shaft, including first gear means, motor means for driving said gear means, and brake means for braking the drive in the event of motor failure; and second gear means comprising at least in part said gear wheels of said rope drums and including standby means intermediate said gear wheels, said second gear means being operatively coupled to said first gear means of each said series of components for driving connection therewith, said standby means of said second gear means being mounted in relation to said gear wheels to actively drive said gear wheels and to support the torque load only upon failure within said closed circuit kinematic chain drive of at least one of said series of components of each of said series, said standby means comprising for this purpose intermediate gear wheel means having a displaceable mounting providing for rotation of said first intermediate gear wheel means about a first axis during normal operation of said closed circuit kinematic chain, said mounting being automatically displaced, upon failure of one of said series of components, in a direction transverse to the direction of meshing extent of said intermediate gear wheel means to orient said mounting for rotation of said intermediate gear wheel means about a second axis which is displaced and different from the first.

2. In a crane having at least one pair of rope drums in turn having gear wheels linked by a kinematic gear chain including a series of cooperating elements, the improvements consisting in that said kinematic gear chain is a closed circuit kinematic chain drive having two series of components on opposite sides of and interconnected by a coupling shaft, each series of components, beginning at a point most distant from said coupling shaft and in a direction toward said coupling shaft, including first gear means, motor means for driving said gear means, and brake means for braking the drive in the event of motor failure; and second gear means comprising at least in part said gear wheels of said rope drums and including standby means intermediate said gear wheels, said second gear means being operatively coupled to said first gear means of each said series of components for driving connection therewith, said standby means of said second gear means being mounted in relation to said gear wheels to ac tively drive said gear wheels and to support the torque load only upon failure within said closed circuit kinematic chain drive of at least one of said series of components of each of said series, said standby means comprising for this purpose a pair of intermediate gear wheels, at least one of which has a displaceable mounting providing for rotation of said one of said intermediate gear wheels about a first axis during normal operation of said closed circuit kinematic chain, said mounting being automatically displaced, upon failure of one of said series of components, in a direction transverse to the direction of meshing extent of said intermediate gear wheels to orient said mounting for rotation of said one intermediate gear wheel about a second axis which is displaced and different from the first.

3. A crane according to claim 2, wherein means are provided in the region of said mounting for actuating a warning device when said displacement occurs.

4. A crane according to claim 3, wherein said displaceable mounting comprises bearing means associated with said one intermediate gear wheel, said bearing means being received in slot means formed in a frame of the crane, said bearing means being constrained in its movement by said slot means.

5. A crane according to claim 2, wherein said slot means defines a vertically extending slot.

6. A crane according to claim 3, wherein said displaceable mounting comprises bearing means associated with said one intermediate gear wheel, said bearing means being mounted in resilient collar means carried by the crane frame, displacement of the axis about which said one intermediate gear wheel rotates being accommodated by deformation of said resilient collar means.

7. A crane according to claim 2, wherein said intermediate gear wheels in said closed kinematic gear chain normally idle and are free of working load, said one of said intermediate gear wheels being displaced on asynchronous rotation of components of said kinematic chain, said one intermediate gear wheel when displaced being effective to transfer working load torque as part of said kinematic chain.

8. A crane according to claim 7 wherein said displacement of said one intermediate gear wheel is a limited displacement between a first position in which it normally idles to a second position constituting a posigagement with adjacent parts of said kinematic chain. i i i

Claims

1. In a crane having at least one pair of rope drums in turn having gear wheels linked by a kinematic gear chain including a series of cooperating elements, the improvements consisting in that said kinematic gear chain is a closed circuit kinematic chain drive having two series of components on opposite sides of and interconnected by a coupling shaft, each series of components, beginning at a point most distant from said coupling shaft and in a direction toward said coupling shaft, including first gear means, motor means for driving said gear means, and brake means for braking the drive in the event of motor failure; and second gear means comprising at least in part said gear wheels of said rope drums and including standby means intermediate said gear wheels, said second gear means being operatively coupled to said first gear means of each said series of components for driving connection therewith, said standby means of said second gear means being mounted in relation to said gear wheels to actively drive said gear wheels and to support the torque load only upon failure within said closed circuit kinematic chain drive of at least one of said series of components of each of said series, said standby means comprising for this purpose intermediate gear wheel means having a displaceable mounting providing for rotation of said first intermediate gear wheel means about a first axis during normal operation of said closed circuit kinematic chain, said mounting being automatically displaced, upon failure of one of said series of components, in a direction transverse to the direction of meshing extent of said intermediate gear wheel means to orient said mounting for rotation of said intermediate gear wheel means about a second axis which is displaced and different from the first.

2. In a crane having at least one pair of rope drums in turn having gear wheels linked by a kinematic gear chain including a series of cooperating elements, the improvements consisting in that said kinematic gear chain is a closed circuit kinematic chain drive having two series of components on opposite sides of and interconnected by a coupling shaft, each series of components, beginning at a point most distant from said coupling shaft and in a direction toward said coupling shaft, including first gear means, motor means for driving said gear means, and brake means for braking the drive in the event of motor failure; and second gear means comprising at least in part said gear wheels of said rope drums and including standby means intermediate said gear wheels, said second gear means being operatively coupled to said first gear means of each said series of components for driving connection therewith, said standby means of said second gear means being mounted in relation to said gear wheels to actively drive said gear wheels and to support the torque load only upon failure within said closed circuit kinematic chain drive of at least one of said series of components of each of said series, said standby means comprising for this purpose a pair of intermediate gear wheels, at least one of which has a displaceable mounting providing for rotation of said one of said intermediate gear wheels about a first axis during normal operation of said closed Circuit kinematic chain, said mounting being automatically displaced, upon failure of one of said series of components, in a direction transverse to the direction of meshing extent of said intermediate gear wheels to orient said mounting for rotation of said one intermediate gear wheel about a second axis which is displaced and different from the first.

8. A crane according to claim 7 wherein said displacement of said one intermediate gear wheel is a limited displacement between a first position in which it normally idles to a second position constituting a position on either of opposite sides of said first position, the side of said first position to which said one gear means is moved depending on the angular sense of said asynchronous rotation, said one intermediate gear wheel transferring working load torque in either of said second positions as part of said kinematic chain, and warning means responsive to said displacement in either said sense.

9. A crance according to claim 8, wherein said intermediate gear wheels are normally in loose meshing engagement with adjacent parts of said kinematic chain.