Adjust and lock mechanism

An adjust and lock mechanism includes a drive gear (16) rotatably mounted on a frame and adapted to engage a drive track (15) on a member (13) to allow adjustment between the frame (1) and the member by rotation of the drive gear, the drive gear being mounted on a drive spindle (17) that can move axially relative to the drive gear and which is normally spring loaded (34) into locking engagement with the frame and can be moved axially to disengage the locking engagement and allow the spindle to be rotated to operate the drive gear. A locking engagement is provided by a dog gear at one end of the spindle. A lock release button (32) and hand wheel (18) to rotate the drive gear are located adjacent one another for joint operation. A gear train connects the hand wheel to the drive gear.

This application is a National Stage Application of PCT/EP2008/065675, filed 17 Nov. 2008, which claims benefit of Serial No. 0722596.4, filed 16 Nov. 2007 in Great Britain and which applications are incorporated herein by reference. To the extent appropriate, a claim of priority is made to each of the above disclosed applications.

TECHNICAL FIELD

This invention relates to an adjust and lock mechanism suitable for adjusting a moveable member such as an adjustable member of a gantry.

DISCLOSURE OF THE INVENTION

According to one aspect, the invention comprises an adjust and lock mechanism comprising a drive gear rotatably mounted in a frame and adapted to engage a drive track in an adjustable member that is to be adjusted relative to the frame by rotation of the drive gear, the drive gear being mounted on a drive spindle that can move axially relative to the drive gear and which is normally spring loaded into locking engagement with the frame and can be moved axially to disengage the locking engagement and allow the spindle to be rotated to operate the drive gear.

In one embodiment, the locking engagement is provided by a brake, such as a dog gear, and said axial movement is provided by mounting the drive gear on a sleeve in which the spindle slides. A lock release button on one end of the spindle allows it to be operated by depression, and the brake at the opposite end of the spindle disengages to allow the drive gear to be rotated. A hand wheel mounted on the spindle adjacent to the lock release button serves to rotate the drive gear to adjust the adjustable member. The lock release button is then released to allow the brake to re-engage and lock the adjustable member in its new position. The proximity of the hand wheel and lock release button facilities joint operation. Also the spring loading of the lock release button makes it fail-safe if released accidentally.

The adjust and lock mechanism may incorporate a gear train to improve the mechanical advantage of the hand wheel in operating the drive gear. The drive track in the adjustable member may comprise a drive chain secured in place to move with the adjustable member upon rotation of the drive gear. The drive track is preferably received in a channel in the adjustable member.

In one embodiment of the invention, the adjust and lock mechanism is mounted on a frame comprising front and back plates with the drive gear located between them and the hand wheel and lock release button accessible outboard of one of the plates. The plates may serve to connect a pair of splayed legs which extend downwards therefrom to form a base frame. Wheels may be provided at the lower ends to make the base frame mobile. The adjustable member is received between the plates to extend upwards from them and may be guided by support wheels either side to resist movement laterally of the drive gear and spindle.

According to another aspect, the invention comprises an adjust and lock mechanism comprising a drive wheel mounted on a drive spindle that can move axially relative to the drive wheel and which is normally spring loaded into locking engagement with a stop and can be moved axially to disengage the locking engagement and allow the spindle to be rotated to operate the drive wheel, a manually operable lock release member mounted on the spindle to move the spindle axially when operated, and a manually rotatable adjust member mounted on the spindle adjacent the lock release member so as to facilitate operation of both jointly.

According to yet another aspect, the invention comprises an adjustment mechanism comprising a drive gear rotatably mounted on a frame and adapted to engage a drive track in the form of a chain mounted on a member so as to allow adjustment between the frame and member by rotation of the drive gear.

EMBODIMENTS OF THE INVENTION

The gantry shown inFIG. 1comprises two upright side frames1connected by a horizontal beam2supporting a beam trolley3that runs along the beam on wheels4and has a lifting eye5. The side frames1each comprise a pair of legs6joined at their top by a pair of connecting plates7which diverge downwards and are connected at their bottom by a tie bar8. A wheel9is connected to the bottom of each leg6and is provided with a brake10. The legs6are tubular with a rectangular section and their side faces abut the plates7either side.

The plates7are of a generally triangular shape to match the profile of the diverging legs6and each have a pair of upwardly projecting lugs11at their upper end to form mounting points for a pair of guide wheels12located between respective pairs of lugs11either side of a central vertical gap between the two plates. This gap is designed to receive an upright adjustable support13, the top of which is connected to one end of the horizontal beam2. The support13is a tubular member with a substantially rectangular section and has channels14formed longitudinally in opposite sides. A roller link chain15is fitted in one of these channels for engagement by a drive gear16to determine the vertical position of the support13. A second pair of wheels12is mounted between the plates7below the drive gear16to engage and support the sides of the support13.

As shown more clearly inFIGS. 3 to 5, the drive gear16is mounted on a drive spindle17between the two plates7. The spindle17rotates in plain bearings in the plates7and a hand wheel18is mounted on the spindle17outboard of the outer plate7so as to be accessible for operation by a user to drive the drive gear16. Grub screws37fasten the hand wheel18to the spindle17. However, the hand wheel18drives the gear16via a drive train mounted between the plates7on the spindle17and two lay spindles19and20. The drive train comprises an input gear21that is fixedly mounted on the spindle17and which meshes with a larger gear22of a double gear rotatably mounted on the lay spindle19. A smaller gear23of the double gear meshes with a larger gear24of a double gear rotatably mounted on the second lay spindle20, and a smaller gear25meshes with a third gear26rotatably mounted on the lay spindle19and substantially the same diameter as the gear22on the same spindle. The gear26meshes with a smaller gear27that is integral with the drive gear16as a double gear rotatably mounted on the spindle17. Thus a drive train comprises seven gears with ratios such as to generate a mechanical advantage for the hand wheel18in rotating the drive gear16so as to move the chain15and support13vertically.

As shown more clearly inFIGS. 5 and 6, the spindle17comprises a square section rod28with a cylindrical sleeve29as a close fit over it. A pin30extends laterally through the rod28and projects either end to engage a pair of longitudinal slots31in the sleeve29so as to key the rod and sleeve together for rotation but to allow the rod to move axially within the sleeve29. A disc32is connected by a screw33to one end of the rod28extending from the sleeve29, and compresses a helical spring34that is received within a counterbore35in the open end of the sleeve29around the rod28. The spring34serves to urge the rod28outwardly of the sleeve29until the pin30engages the bases of the slots31. The end of the rod28opposite the disc32also extends from the sleeve29and is fitted with a second pin36that extends laterally in alignment with the slots31(although this is optional as the pin36does not need to engage the slots31).

In use, the spindle17is installed with the disc32and grease points37outboard of the one plate7, and with the second pin36outboard of the other plate7. The outer face of this other plate7is provided with a series of projections38spaced around the end of the spindle so as to form spaces therebetween in which the projecting ends of the pin36can engage in the manner of a dog gear. Thus the spring34normally serves to urge the rod28axially so as to engage the dog gear, which serves to prevent rotation of the spindle17. The dog gear36,38therefore acts as a brake to prevent rotation of the spindle17until the disc32is depressed to disengage the dog gear36,38. Once the pin36is clear of the projections38, the spindle is free to rotate. When the brake is applied, the downwards load of the supports13and horizontal beam2and any load carried by it, is transferred via the chain15, drive gear16, and spindle17to the dog gear brake36,38. When the brake is released by depressing the disc32, the downwards load is applied through the gear train to the hand wheel18, but the mechanical advantage of the gear train reduces the torque on the hand wheel so that it can be managed by a user. The fact that the disc32to operate the brake, and the hand wheel18to adjust the height of the beam2are located together on the same spindle serves to make joint use very easy.

It will be appreciated fromFIGS. 3 to 5that a number of gear spacers43are provided on the spindles17,19,20to keep the gear train aligned. The lay spindles19,20are both fixed against rotation by a pin39that engages the ends of both. The plates7are provided with appropriate openings for the spindles, and these are duplicated in a symmetrical manner to avoid handedness of the assembly.

In order to increase lateral stability of the gantry, a strut member40is provided between the beam2and each side frame1. The strut40comprises a tubular member similar to the support13and is connected at its lower end to the lower end of the support13where it projects below the plates7. This connection44then limits the extent to which the support13and beam2can be raised vertically. The upper end of the strut40is connected to the beam2inboard of the support13via connection plates41either side. It will be appreciated that when the supports13and struts40are disconnected from the beam2, the side frames1can be readily folded into a compact assembly for transport.

The beam2preferably has a section as shown inFIG. 7with a substantially rectangular section which is used in the upright mode. The beam is a tubular extrusion and is formed with an internal lateral strengthening wall45. The side walls of the beam in the central region are of reduced thickness to reduce weight. The walls of the beam top and bottom are of increased thickness to increase strength and to accommodate channels46at the bottom, opening outwards onto both sides. These channels46are provided to accommodate equipment such as electrical harnesses or means to drive the beam trolley. For example, the channel might accommodate a chain with which a drive gear on a trolley engages in the manner of the drive gear16used for vertical adjustment inFIGS. 1 to 6. The drive gear might engage a roller chain mounted in one slot46, and a power pick-up for an electric motor drive of the drive gear might engage a power pick-up rail mounted in the opposite slot46.

In another embodiment, a beam trolley may be connected to a chain in the manner of a continuous loop and engage gears at either end of the beam, one of which is driven.

In yet another embodiment of the invention, the adjust and lock mechanism shown inFIGS. 1 to 6for vertical adjustment of the upright supports13, is used to control the position of the beam trolley3, the mechanism being incorporated into the trolley with the drive gear16in engagement with a roller link chain fitted in a channel46.

It will be appreciated that the provision of a chain to form a gear track is a simple and effective manufacturing step, which allows suitable hard wearing material to be used for the track in a member which may be composed of softer material, such as extruded aluminium.