GB2074286A

GB2074286A - Torque-responsive Mounting of Gears in a Gearbox

Info

Publication number: GB2074286A
Application number: GB8110487A
Authority: GB
Original assignee: Pitcraft Summit Ltd
Current assignee: Pitcraft Summit Ltd
Priority date: 1980-04-18
Filing date: 1981-04-03
Publication date: 1981-10-28
Also published as: GB2074286B

Abstract

A gearbox 1 comprises a housing 2 containing a reduction stage 18 comprising a first gear 19 rotatable about a axis 20 and in mesh with a second gear 21 rotatable about parallel axis 22, the first gear 19 being mounted in a carrier 23 pivotable about the axis 22 of the second gear 21 and constrained by a torque sensing device 26 connected between the carrier 23 and the housing 2. When a predetermined torque level is exceeded, the device 26 is triggered to switch off an electric motor driving the input shaft 3 of the gearbox. Output shaft 10 of a two-speed, constant-mesh stage of the gearbox is connected to the gear 19 by a flexible gear type coupling 16, 17. <IMAGE>

Description

SPECIFICATION Gearbox This invention relates to a gearbox, of the single speed or change speed type.

Gearboxes are often employed in service conditions where loading is erratic and on occasion in excess of design limits, e.g. when driving an underground mineral carrying conveyor. Furthmore, if such a conveyor is of the scraper chain type and located along a mineral, e.g. coal face, it is not uncommon for the conveyor to jam for one reason or another, possibly resulting in damage to the gearbox and/or any intermediate transmission between the gearbox and the conveyor.

According to a first aspect of the present invention, a gearbox comprises a housing containing a reduction stage comprising a first gear rotatable about an axis, and in mesh with a second gear rotatable about a parallel axis, the first gear being mounted in a carrier pivotable about the axis of the second gear and constrained by a torque sensing device connected between the carrier and the housing.

When drive is applied to the gearbox and one of the clutches is engaged so as to transmit the drive through the gearbox, the reaction torque on the carrier is continuously monitored by the torque sensing device, which provides for overload protection, e.g. by activating a switch controlling current to the electric motor, and hence obviating damage to the gearbox etc., upon a predetermined torque being exceeded.

The gearbox may comprise basically a preliminary reduction stage preceding the first mentioned reduction stage. In detail, the gearbox may comprise an input shaft connectable to a prime mover and carrying a gear constantly in mesh with a gear mounted in bearings on a lay shaft, a clutch to drivably connect or disconnect the gear to the lay shaft, the latter being rotatable about an axis spaced from, and parallel to, the axis of the input shaft, terminating in a flexible gear type coupling to the first mentioned reduction stage. In a change speed form, the gearbox may be provided with a connecting gear fixed to the lay shaft and permanently in mesh with a gear mounted in bearings on the input shaft, with a further clutch to drivably interconnect or disconnect the connecting gear to the input shaft.

Preferably, the carrier also carries the second gear as well as the first gear of the first mentioned reduction stage. The input shaft may incorporate an internally splined or geared socket to receive a male, externally splined spigot of the prime mover.

If still further speed reduction is required, the output shaft of the first mentioned reduction stage may be connected to the input shaft of a further reduction stage. The requirements for particular speed reductions will of course depend on whether the gearbox is intended for transmitting power to a conveyor, where further speed reduction would be required.

In detail, the torque sensing device may be connected electrically to an electric motor constituting the prime mover, to switch off the motor upon a predetermined torque being exceeded.

The invention will now be described in greater detail, by way of example, with reference to the accompanying drawings, in which: Figure 1 is an axial sectional view through a speed change gearbox in accordance with the invention; Figure 2 is a section on the line Il-Il of Figure 1.

In the drawings, the gearbox, indicated at 1, comprises a housing 2 rotatably supporting an input shaft 3 rotatable about an axis 4, and having a female, internally splined socket 5 to receive a male, externally splined spigot 6 from an electric motor (not shown) to which the gearbox 1 is bolted. The input shaft 3 has external teeth 7 constantly in mesh with a gear 8 mounted in bearings 9 on a lay shaft 10 rotatable about an axis 11 spaced from, and parallel to, the axis 4.

The gear 8 is connected by bolts 12 to first elements 13 of a hydraulically operable clutch 14 with second elements 1 5 carried by the lay shaft 10, the latter terminating in a flexible gear type coupling comprising a female, internally splined socket 1 6 to receive a male, externally splined spigot 1 7 of a final reduction stage 18.

The final reduction stage 18 comprises a first gear 1 9 drivable by the spigot 1 7 about an axis 20, and in mesh with a second gear 21 rotatable about a parallel axis 22, both gears being mounted within a pivotable carrier 23. The carrier 23 is pivotable about the axis 22 by being mounted for pivotal movement about bearing faces 24 and shoulders 25 of the housing 2.

However, pivotal movement of the carrier 23 is constrained by a torque sensing device 26 connected between the carrier 23 and the housing 2, with the torque sensing device electrically connected to the electric motor. Thus, pivotal movement of the carrier 23 about axis 22 is constrained by the torque sensing device 26 and hence the torque sensing device 26 can be pre-set to allow a predetermined strain to occur and hence a predetermined torque level to be attained which level, when exceeded, e.g. by an unusual load being imposed on the conveyor or by the conveyor becoming jammed, triggers the torque sensing device 26 to switch off the electric motor to avoid unnecessary damage to the electric motor, the gearbox 1, and the subsequent transmission to the conveyor.

The input shaft 3 also carries first elements 27 of a further hydraulically operable clutch 28, with second elements 29 bolted to a gear 30, mounted in bearings 31 on the input shaft 3. The gear 30 is constantly in mesh with a connecting gear 32 fixed to the lay shaft 10. Thus, selective operation of a clutch 14 or 28 drives the lay shaft 10 respectively either through the gear 8, as a preliminary reduction stage, or through the gear 32, as an alternative preliminary reduction stage, while oil for the clutches is provided by a pump 33 driven by a gear 34 permanently in mesh with the teeth 7 of the input shaft 3.

Claims

1. A gearbox comprising a housing containing a reduction stage comprising a first gear rotatable about an axis, and in mesh with a second gear rotatable about a parallel axis, the first gear being mounted in a carrier pivotable about the axis of the second gear and constrained by a torque sensing device connected between the carrier and the housing.

2. A gearbox as claimed in Claim 1, comprising a preliminary reduction stage preceding the first mentioned reduction stage.

3. A gearbox as claimed in Claim 2, comprising an input shaft connectable to a prime mover and carrying a gear constantly in mesh with a gear mounted in bearings on a lay shaft, a clutch to drivably connect or disconnect the gear to the lay shaft, the latter being rotatable about an axis spaced from, and parallel to, the axis of the input shaft, terminating in a flexible gear type coupling to the first mentioned reduction stage.

4. A gearbox as claimed-in Claim 3, in a speed change form provided with a connecting gear fixed to the lay shaft and permanently in mesh with a gear mounted in bearings on the input shaft, with a further clutch to drivably interconnect or disconnect the connecting gear to the input shaft.

5. A gearbox as claimed in any preceding Claim, wherein the carrier also carries the second gear as well as the first gear of the first mentioned reduction stage.

6. A gearbox as claimed in any one of Claims 3 to 5, wherein the input shaft incorporates an internally splined or geared socket to receive a male, externally splined spigot of the prime mover.

7. A gearbox as claimed in any preceding Claim, wherein the output shaft of the first mentioned reduction stage is connected to the input shaft of a further reduction stage.

8. A gearbox as claimed in any one of Claims 3 to 7, wherein the clutches are hydraulically operable.

9. A gearbox as claimed in Claim 8, wherein the hydraulic fluid for the clutches is provided by a pump driven by a gear permanently in mesh with the gear of the input shaft.

10. A gearbox substantially as hereinbefore described with reference to the accompanying drawings.