GB2127917A - Two speed reduction gearbox - Google Patents

Abstract

A reduction gearbox for a winch or crane hoist incorporates a two speed gear having a sliding positive clutch member 6 with teeth formed as pins on each face and includes a brake drum 21. The load on the gearbox is held by the brake when an electric driving motor 2 is not energised. At all times when the gearbox gearing is in the neutral position the motor 2 is deenergised and the brake engaged. Gear changing can be accomplished either manually or remotely by push button, a reversible electric motor 13 driving a screw 12 through chain gearing 14 to move a shift fork 15. The load is always either connected to the motor by the high or low gear or held by the brake. <IMAGE>

Description

SPECIFICATION Two speed reduction gearbox The invention is a two speed gear arrangement for use in a crane hoist gearbox or a similar application such as a winch gearbox.

The gearbox is driven by a single speed electric motor and gives two speeds at the output shaft or rope drum, whichever forms the output.

Figure 1 is a plan and part section through the gearbox. The input shaft (1) is driven by electric motor (2) through flange coupling (3).

Loose gears (4) and (5) can rotate on the input shaft (1) and are spaced on either side of a splined portion of the shaft on which slides a splined clutch bobbin (6). Both flanges of the clutch bobbin (6) has four equally spaced pins, which project with a short parallel section and terminate with a cone section. These bobbin pins engage with gears (4) and (5) by sliding into blind holes drilled into the end of gears (4) and (5), thus driving either gear as required. The number of blind holes in gears (4) and (5) are some multiple of four, equally spaced, and normally as many as the pitch diameter will allow without breaking into each other, but can be arranged with slight interference if required.

The pitch diameter coincides with the pitch diameter of the pins on the bobbin (6). The number of pins and holes can be varied to suit the individual gearbox.

Gears (4) and (5) engage with gears (8) and (9) keyed to shaft (10), and have different numbers of teeth to suit the gear ratio required. Thus by sliding bobbin (6) to the left or to the right shaft (10) is driven at different speeds.

The bobbin (6) is moved from the extreme left or extreme right positions, changing gear, by a fork which fits into the bobbin groove.

Figure 2 is a section through the bobbin shift mechanism. Fork (15) slides on rod (11) traversed by screw (12), which is driven by reversible electric motor (1 3) through chain drive (14).

The fork (15) is bevelled at each end to lift up tappets (16) and (1 7) to activate limit switches (18) and (1 9) to stop motor (13) when the bobbin has reached each extreme position, thus changing gear. Spring plungers hold the bobbin in these positions after gear change.

The speed change motor (13) is controlled by two push buttons, remotely if necessary, and interlocked electrically with the drive motor (2), so that neither motor can be energised at the same time as the other.

Shaft (10) is extended outside the gearbox to take a brake drum (20) and brake (21). The brake is applied by a weighted lever and grips the drum when the driving motor (2) is deenergised.

The two speed gear can only be changed when driving motor (2) is de-energised and the brake is on the hold position.

Gear (8) gears with gear (22) and is followed by other pairs of gears to suit the total gear reduction required.

The above arrangement is designed for the gearchange to be done remotely by electrical control. The gear change can be done manually by replacing the chain drive (14) and electric motor (1 3) by a crank handle fixed to the screw (12).

1. When the gear change is being made the load or pull on the gearbox output shaft or rope drum is held by the brake fixed to the extended second shaft. This prevents rotation of all the gearbox gearing and shafts excepting the input shaft, which is free to rotate.

The brake is held on by a weighted lever, and can only be released by energising the driving motor. The current also releases the brake, and holds the brake off when the driving motor is energised.

The driving motor and the gear change mechanism are interlocked electrically so that both cannot run at the same time. The driving motor is also interlocked electrically with the gear change so that the motor cannot be energised unless one of the gears is in the operating position.

2. The gear change is easy to execute and can be done in five seconds manually, or remotely operated by means of a press button selecting either gear.

The pointed taper pins of the clutch bobbin enter the holes in either gear, and if not central with the holes in the gear, will rotate the input shaft slightly to bring the bobbin taper pins central with the holes in either gear, thus allowing the clutch bobbin to move until the flange makes contact with either gear face. When the parallel portion of either group of clutch pins are fully into mesh with its gear, there is no tendency for the clutch bobbin to be disengaged from either gear, whichever is driven.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (2)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Two speed reduction gearbox The invention is a two speed gear arrangement for use in a crane hoist gearbox or a similar application such as a winch gearbox. The gearbox is driven by a single speed electric motor and gives two speeds at the output shaft or rope drum, whichever forms the output. Figure 1 is a plan and part section through the gearbox. The input shaft (1) is driven by electric motor (2) through flange coupling (3). Loose gears (4) and (5) can rotate on the input shaft (1) and are spaced on either side of a splined portion of the shaft on which slides a splined clutch bobbin (6). Both flanges of the clutch bobbin (6) has four equally spaced pins, which project with a short parallel section and terminate with a cone section. These bobbin pins engage with gears (4) and (5) by sliding into blind holes drilled into the end of gears (4) and (5), thus driving either gear as required. The number of blind holes in gears (4) and (5) are some multiple of four, equally spaced, and normally as many as the pitch diameter will allow without breaking into each other, but can be arranged with slight interference if required. The pitch diameter coincides with the pitch diameter of the pins on the bobbin (6). The number of pins and holes can be varied to suit the individual gearbox. Gears (4) and (5) engage with gears (8) and (9) keyed to shaft (10), and have different numbers of teeth to suit the gear ratio required. Thus by sliding bobbin (6) to the left or to the right shaft (10) is driven at different speeds. The bobbin (6) is moved from the extreme left or extreme right positions, changing gear, by a fork which fits into the bobbin groove. Figure 2 is a section through the bobbin shift mechanism. Fork (15) slides on rod (11) traversed by screw (12), which is driven by reversible electric motor (1 3) through chain drive (14). The fork (15) is bevelled at each end to lift up tappets (16) and (1 7) to activate limit switches (18) and (1 9) to stop motor (13) when the bobbin has reached each extreme position, thus changing gear. Spring plungers hold the bobbin in these positions after gear change. The speed change motor (13) is controlled by two push buttons, remotely if necessary, and interlocked electrically with the drive motor (2), so that neither motor can be energised at the same time as the other. Shaft (10) is extended outside the gearbox to take a brake drum (20) and brake (21). The brake is applied by a weighted lever and grips the drum when the driving motor (2) is deenergised. The two speed gear can only be changed when driving motor (2) is de-energised and the brake is on the hold position. Gear (8) gears with gear (22) and is followed by other pairs of gears to suit the total gear reduction required. The above arrangement is designed for the gearchange to be done remotely by electrical control. The gear change can be done manually by replacing the chain drive (14) and electric motor (1 3) by a crank handle fixed to the screw (12). CLAIMS

1. When the gear change is being made the load or pull on the gearbox output shaft or rope drum is held by the brake fixed to the extended second shaft. This prevents rotation of all the gearbox gearing and shafts excepting the input shaft, which is free to rotate.

The brake is held on by a weighted lever, and can only be released by energising the driving motor. The current also releases the brake, and holds the brake off when the driving motor is energised.

The driving motor and the gear change mechanism are interlocked electrically so that both cannot run at the same time. The driving motor is also interlocked electrically with the gear change so that the motor cannot be energised unless one of the gears is in the operating position.

2. The gear change is easy to execute and can be done in five seconds manually, or remotely operated by means of a press button selecting either gear.

The pointed taper pins of the clutch bobbin enter the holes in either gear, and if not central with the holes in the gear, will rotate the input shaft slightly to bring the bobbin taper pins central with the holes in either gear, thus allowing the clutch bobbin to move until the flange makes contact with either gear face. When the parallel portion of either group of clutch pins are fully into mesh with its gear, there is no tendency for the clutch bobbin to be disengaged from either gear, whichever is driven.