US3863406A

US3863406A - Drive mechanism for jib cranes

Info

Publication number: US3863406A
Application number: US404550A
Authority: US
Inventors: Donald J Quick
Original assignee: International Harverster Corp
Current assignee: Navistar International Corp
Priority date: 1972-10-09
Filing date: 1973-10-09
Publication date: 1975-02-04
Anticipated expiration: 1992-02-04
Also published as: DE2350398B2; FR2202025B1; FR2202025A1; CA986060A; GB1437526A; DE2350398A1

Abstract

An extensible jib for a crane comprising two jib sections arranged in telescopic relation with a pair of driven rollers engaging the inner section and operable to extend or retract the jib. Brake means are provided to hold the jib sections in any selected position, the brake means being operable in response to operation of the driven roller to release the brake when the rollers are driven and apply the brake when the rollers are not driven.

Description

United States Patent 1191 Quick 14 1 Feb. 4, 1975 DRIVE MECHANISM FOR JIB CRANES [75] Inventor: Donald J. Quick, West Bundaberg,

Queensland, Australia [73] Assignee: International Harvester Company,

Chicago, Ill.

[22] Filed; Oct. 9, 1973 [21] Appl. No.2 404,550

[30] Foreign Application Priority Data Oct. 9, 1972 Australia 748/72 [52] U.S.Cl ..52/1l5,52/118,52/121, 212/144 [51] Int. Cl. B66c 23/64 [58] Field of Search 52/111, 114, 117, 115, 52/118, 116, 121; 212/55, 144; 214/141, 761, 762

[56] References Cited UNITED STATES PATENTS 1,611,326 12/1926 Abbe 212/55 2,703,634 3/1955 Lee 52/115 2,992,710 7/1961 Thompson 52/114 3,055,459 9/1962 Eitel 52/115 3,236,393 2/1966 Girardi 212/55' 3,319,803 5/1967 Northcott 212/55 3,346,281 10/1967 Thompson..... 52/115 x 3,465,904 9/1969 Pensa 214/141 x 3,480,109 11/1969 Eillel 212/55 3,670,465 6/1972 Cheze 52/115 3,800,965 4/1974 Barron 212/55 x FOREIGN PATENTS OR APPLICATIONS 970,879 9/1964 Great Britain 52/111 Primary ExaminerErnest R. Purser Assistant Examiner-Leslie A. Braun Attorney, Agent, or Firm-Raymond E. Parks; Floyd B. Harman [57] ABSTRACT An extensible jib for a crane comprising two jib sections arranged in telescopic relation with a pair of driven rollers engaging the inner section and operable to extend or retract the jib. Brake means are provided to hold the jib sections in any selected position, the brake means being operable in response to operation of the driven roller to release the brake when the rollers are driven and apply the brake when the rollers are not driven.

3 Claims, 4 Drawing Figures 1 DRIVE MECHANISM FOR JIB CRANES This invention relates to an extension drive for a crane jib.

Many cranes are provided with an extendable jib, usually of a telescopic construction with rollers or slides provided at the front end of the main jib to support the extension portion. Hydraulic cylinders are usually mounted in line with, and behind the jib extension to effect extension and retraction thereof, and this restricts the practical length of the jib extension.

It is an object of the present invention to provide a means for effecting the movement of a jib extension which allows a maximum length of extension to be used.

Thus according to the present invention there is provided a drive mechanism for an extensible crane jib having a main jib section and an extension jib section arranged in a telescopic relation, said drive mechanism comprising at least two spaced rollers engaging opposite faces of the extension jib section, drive means coupled to at least one roller to effecting movement of the extension jib section relative to the main jib section to extend or retract the extension jib section, and brake means operable to lock the extension jib section relative to the main jib extension and releasable in response to energisation of the drive means.

It is preferred that the drive means includes an hydraulic motor and the brake means is adapted to be hydraulically released, the hydraulic circuits of the motor and brake means are interconnected so that the brake means is released when the motor is energised.

In the case where a hydraulic motor is used, the pressure required to operate the hydraulic motor is also fed to a piston operated brake pad. The application of pressure releasing the pad from contact with the extension. In its normal position the brake is pressed against the extension jib section by a compressed spring. Thus if the hydraulic motor is switched off or if a sudden pressure drop should occur, the brake is immediately applied.

In a practical arrangement there is provided the hydraulic motor which is operated by fluid pressure from the crane pump, and a valve is provided to control the direction of rotation of the motor. A chain and sprocket drive connects the motor with a roller disposed on the upper side of the extension jib section and two rollers disposed on the lower side thereof. The upper roller is supported on a frame pivotally supported on the main jib section and is connected to a hydraulical cylinder which is alos connected to the pressure line of the motor, so that when the motor is operating the upper roller is pressed into driving contact with the extension jib section. As an alternative arrangement, this hydraulic cylinder may be replaced by a spring load of sufficient force to maintain the required driving contact.

The jib of the crane may be raised by increasing the inclination of the jib to the horizontal. As the inclination to the horizontal is increased, the motor torque required to extend it will also increase, and the contact pressure between the rollers and the extension section would decrease. By the use of the hydraulic cylinder to apply clamping pressure to the roller, the grip on the jib extension is maintained by the hydraulic pressure in the motor circuit.

LII

It can be seen from the above that the present invention provides an extendable job drive mechanism which avoids the need for a hydraulic extension cylinder and allows for the incorporating of a longer extension section. Also the weight of the extension jib section, and hence the stability of the crane is not varied by the weight of the hydraulic fluid or the extension of the hydraulic ram as with prior art cranes.

The invention will be more readily understood from the following description of one practical arrangement of a crane jib incorporating a drive and brake mechanism in accordance with the present invention. This arrangement of the jib is depicted in the accompanying drawings wherein:

FIG. I is a diagrammatic representation of a typical extendable crane jib located in the normal horizontal position;

FIG. 2 is a view similar to FIG. 1 with the jib in an elevated position;

FIG. 3 is an enlarged view of the forward end of the jib, partly in section, showing the drive and brake mechanisms;

FIG. 4 is a sectional view along line 4-4 in FIG. 3.

Referring now to the drawings, the jib crane comprises a main jib 6 pivotally supported at 7 to the crane frame 8 with the lift cylinder 9, connected between the main jib 6 and a portion of the frame not shown, so that the main jib may be pivoted relative to the frame by extending or retracting the cylinder 9.

Slidably supported within the main jib 6 is the jib extension 12 which may be extended or retracted in a telescopic fashion to vary the effective length of the jib. The jib extension 12 is supported in the main jib l6 and guided during its movement by the stabilizing rollers 13 supported in the main jib and the

rollers

16,17 and 18 forming part of the drive mechanism 14 at the forward end of the main jib 6. The jib extension 12 rests on the

rollers

17 and 18 so that the latter engage the underface of the jib extension and the roller 16, which is substantially vertical above the roller 17, engages the top face of the jib extension.

The main jib 6 is of a generally box type construction with the jib extension 12 located therein in a telescoped relation. The two

rollers

17 and 18 engaging the underside of the jib extension 12 are supported in respective pairs of bearings 20 mounted in opposite sides of the main jib. The roller 16 is supported in bearings 29 carried in respective arms 28 located externally of the main jib 6. Each of the arms 28 are pivoted to the main jib 6 on a common axis 31, parallel to the axis of the roller 16. At the other end the arms 28 are interconnected by a cross member 32 extending through the main jib 6.

The single acting hydraulic cylinder 33 is attached to the main jib 6 with the piston rod thereof connected to the cross member 32 so that when fluid is applied to the hydraulic cylinder 33, the arms 28 pivot relative to the main jib 6 to cause pressure engagement between the roller 16 and the upper face of the jib extension 12. The reaction to the pressure applied through the roller 16 is taken by the

rollers

17 and 18 so that in effect the application of pressure to the hydraulic cylinder 33 causes pressure contact between the three rollers and the jib extension 12. The hydraulic cylinder 33 is interconnected with the hydraulic circuit of the motor 26 so that when the motor is operated fluid under pressure is delivered to the hydraulic cylinder 33 so as to establish pressure contact between the rollers and the jib extension during the driving operation.

Each roller has an axial extension at one end carrying

respective sprockets

21, 22 and 23 coupled by the chain 24 to the sprocket 25 mounted on the shaft of the hydraulic motor 26. The chain 24 is engaged by the sprocket 21 driving the roller 16 on the external side of the chain, whilst the

sprockets

22 and 23 driving the

rollers

17 and 18 engage the innerside of the chain so that

rollers

17 and 18 rotate in the opposite direction to the roller 16. As the roller 16 engages in opposite face of the jib extension, the three rollers in fact drive the jib in the same direction. The hydraulic motor 26 is reversible and is controlled by the valve 30 so that the jib extension may be extended or retracted by the operation of the hydraulic motor 26 driving the rollers l6, l7 and 18.

The brake mechanism comprises the back plate 36 carrying the friction pad 37, and the hydraulic cylinder 38 connected via the piston rod 39 to the back plate 36. The hydraulic cylinder 38 is rigidly attached to the main jib 6, and the pair of pressure springs 40 are interposed between the cylinder and the pressure plate 42 carried by the piston rod 39. The springs 40 urge the friction pad via the back plate 36 and pressure plate 42 into frictional contact with the upper face of the jib extension 12, and thus acts as a brake to hold the jib extension 12 in the desired position relative to the main jib 6. The hydraulic cylinder 38 is a single acting cylinder with hydraulic fluid being admitted to the underside of the piston as viewed in FIG. 3, to raise the piston, and hence raise the back plate and friction pad, against the action of the springs 40 to release the jib extension for extending or retracting movement relative to the main jib.

The hydraulic cylinder 38 which releases the brake mechanism 35 is connected to the hydraulic circuit of the motor 26 so that whenever the motor is operated to extend or retract the jib extension, fluid pressure is applied to the underside of the piston to raise the friction pad, and thus release the brake on the jib exten- SlOIl.

It will be appreciated that if the jib is upwardly inclined the extension would tend to retract under gravity without operation of the motor. However in order to release the brake, pressure is required in the hydraulic circuit of the motor. Accordingly the one way pressure valve 45 is provided in the return line 46 of the motor hydraulic circuit so that any rotation of the motor will develop pressure in the return line sufficient to release the brake, and cause the rollers to grip the jib extension. This arrangement ensures that retraction of the jib extension is at all times under the control of the motor.

I claim:

1. In a crane having an elongated cantilevered main jib of the box type construction, an extendable and retractable elongate extension jib of uniform rectangular cross section telescopically mounted within the main jib, hydraulic power means including means for selectively energizing the power means for telescopically extending and retracting the extension jib, and securing means for holding the extension jib in place following telescopic movement, the improvement comprising:

a U-shaped lever having the ends of the extending arms of the U hinged to the lateral sides of the main jib and the cross-member of the U passing transversely through the lateral sides of the main jib;

a first roller mounted on a first shaft passing transversely through the lateral sides of the main jib and being journalled to the arms of the U-shaped lever, the first roller sitting on top of the extension jib;

a second roller mounted on a second shaft passing transversely through and being journalled to the latteral sides of the main jib and supporting the bottom of the extension jib, the axis of the second shaft being vertically aligned with the axis of the first shaft;

a third roller spaced horizontally from and parallel with the second roller and being mounted on a third shaft passing transversely through and being journalled to the lateral sides of the main jib and supporting the bottom of the extension jib;

a pulley wheel keyed to each shaft including a continuous belt means drivingly connecting the pulley wheels to the hydraulic power means for rotating the rollers in unison and telescopically moving the extension jib upon energization of the hydraulic power means;

a brake shoe sitting on top of the extension jib in the space between the vertical planar axes of the second and third shafts;

first and second hydraulic power ram means mounted on the main jib and each having first and second piston rod means respectively and being hydraulically connected to the hydraulic power means for simultaneous energization of the piston rod means with the power means, the first piston rod means being connected to the brake shoe for lifting the brake shoe from the extension jib upon energization thereof, the second piston rod means being connected to the cross-member of the U for swinging the arms of the U upon energization thereof and squeezing the extension jib between the rotating rollers; and

spring means between the brake shoe and the first piston rod means for pressing the brake shoe against the top of the extension jib upon the simultaneous de-energization of the hydraulic power means and piston rod means for halting the movement of the extension jib.

2. In the combination, as claimed in claim 1, wherein the three rollers are of identical diameter and the pulley wheels for each shaft are of identical diameter.

3. In the combination, as claimed in claim 2, wherein the pulley wheels comprise sprocket gears of identical size and the endless belt is a chain trained about the sprocket gears, and the hydraulic power means includes a sprocket gear drivingly connected to the chain.

Claims

1. In a crane having an elongated cantilevered main jib of the box type construction, an extendable and retractable elongate extension jib of uniform rectangular cross section telescopically mounted within the main jib, hydraulic power means including means for selectively energizing the power means for telescopically extending and retracting the extension jib, and securing means for holding the extension jib in place following telescopic movement, the improvement comprising: a U-shaped lever having the ends of the extending arms of the U hinged to the lateral sides of the main jib and the crossmember of the U passing transversely through the lateral sides of the main jib; a first roller mounted on a first shaft passing transversely through the lateral sides of the main jib and being journalled to the arms of the U-shaped lever, the first roller sitting on top of the extension jib; a second roller mounted on a second shaft passing transversely through and being journalled to the latteral sides of the main jib and supporting the bottom of the extension jib, the axis of the second shaft being vertically aligned with the axis of thE first shaft; a third roller spaced horizontally from and parallel with the second roller and being mounted on a third shaft passing transversely through and being journalled to the lateral sides of the main jib and supporting the bottom of the extension jib; a pulley wheel keyed to each shaft including a continuous belt means drivingly connecting the pulley wheels to the hydraulic power means for rotating the rollers in unison and telescopically moving the extension jib upon energization of the hydraulic power means; a brake shoe sitting on top of the extension jib in the space between the vertical planar axes of the second and third shafts; first and second hydraulic power ram means mounted on the main jib and each having first and second piston rod means respectively and being hydraulically connected to the hydraulic power means for simultaneous energization of the piston rod means with the power means, the first piston rod means being connected to the brake shoe for lifting the brake shoe from the extension jib upon energization thereof, the second piston rod means being connected to the cross-member of the U for swinging the arms of the U upon energization thereof and squeezing the extension jib between the rotating rollers; and spring means between the brake shoe and the first piston rod means for pressing the brake shoe against the top of the extension jib upon the simultaneous de-energization of the hydraulic power means and piston rod means for halting the movement of the extension jib.