GB2342421A

GB2342421A - A drive transmission unit

Info

Publication number: GB2342421A
Application number: GB9821844A
Authority: GB
Inventors: Richard Barber
Original assignee: MMD Design and Consultancy Ltd
Current assignee: MMD Design and Consultancy Ltd
Priority date: 1998-10-08
Filing date: 1998-10-08
Publication date: 2000-04-12
Anticipated expiration: 2018-10-08
Also published as: GB9821844D0; GB2342421B

Abstract

A drive transmission unit 20 comprising an input drive shaft 51, a pair of branch power trains 80, 81 arranged to be drivingly connected to a common driven shaft 56 at axially spaced locations 84, 85 along the driven shaft 56, and a load balancing drive transmission means 96 drivingly connecting the input shaft 51 to both of said branch power trains 80, 81. The drive transmission means 59 being arranged to deliver a predetermined amount of torque to each branch power train in response to the load required to drive each branch power train.

Description

A DRIVE TRANSMISSION UNIT The present invention relates to a drive transmission unit, in particular but not exclusively a drive transmission unit suitable for use in driving a conveyor.

In certain circumstances it is desirable to drive, from a common single drive source, a driven shaft at two locations spaced along the axis of the shaft. For example in situations of restricted space it is desirable to split the power train from a main drive shaft to create two separate branch power trains which transmit power to the two axially spaced locations on the driven shaft.

With such an arrangement, although the two branch power trains may be identical it cannot be guaranteed that an equal amount of power will be transmitted through each branch train due, for example, to different amounts of play within each branch train arising from manufacturing tolerances and/or wear.

A general aim of the present invention is to provide a drive transmission unit which overcomes or substantially reduces this problem.

According to a first aspect of the present invention there is provided a drive transmission unit comprising an input drive shaft, a pair of branch power trains arranged to be drivingly connected to a common driven shaft at axially spaced locations along the driven shaft, and a load balancing drive transmission means drivingly connecting the input shaft to both of said branch power trains, the drive transmission means being arranged to deliver a predetermined amount of torque to each branch power train in response to the load required to drive each branch power train.

Preferably the drive transmission means is arranged to deliver the same amount of torque to each branch power train such that the same amount of torque is applied at each of said axially spaced locations on the driven shaft.

Preferably the load balancing drive transmission means comprises a first helical gear drivingly connected to a first of said branch power trains, a second helical gear drivingly connected to a second of said branch power trains, the first and second helical gears being co-axially aligned, and an axially movable transmission gear assembly including third and fourth helical gears drivingly engaged with said first and second helical gears respectively, the third and fourth gears being rotatably fixed so as to rotate in unison, the first, second, third and fourth helical gears being arranged such that loads applied by the first helical gear on the third helical gear urges the transmission gear assembly in an axial direction toward the second helical gear and that loads applied by the second helical gear on the fourth helical gear urges the transmission gear assembly in the opposite axial direction.

Preferably the transmission gear assembly includes a pinion gear, preferably located inbetween the third and fourth helical gears, said pinion gear being drivingly connected to the input drive shaft.

According to another aspect of the present invention there is provided a conveyor having endless conveying means driven by a drive unit as defined above.

Preferably the conveying means comprises a plurality of side by side flights interconnected by a pair of endless chains, each chain being driven by a respective output drive means.

Various aspects of the present invention are hereinafter described with reference to the accompanying drawings, in which: Figure 1 is a part side view of a conveyor including a drive transmission unit according to one embodiment of the present invention ; Figure 2 is a plan view of the conveyor shown in Figure 1; Figure 3 is an enlarged side view of the drive transmission unit shown in Figure 1; Figure 4 is a sectional view taken along line IV-IV in Figure 3; and Figure 5 is a schematic diagram illustrating the principle of operation of the preferred embodiment of the invention.

Referring initially to Figure 5 there is illustrated a transmission unit 20 which is a diagrammatic representation of the transmission unit 20 illustrated in Figure 3.

The unit 20 includes a main draft shaft 51, a driven shaft 56 and a pair of branch power trains 80,81 which are drivingly connected to the driven shaft 56 at two axially spaced locations 84,85 respectively. The branch power trains 80,81 are drivingly connected to the main drive shaft 51 via a load balancing transmission means 59. In the preferred embodiment, the load balancing transmission means 59 functions to deliver the same amount of power to both power trains 80,81.

To achieve this function, in the preferred embodiment, the transmission means 59 comprises a first and second helical gear 90,91 which are in driving engagement with power trains 80,81 respectively; and a transmission gear assembly 60 which is drivingly connected to the first and second helical gears 90,91 and the drive shaft 51.

The transmission gear assembly 60 includes a pair of helical gears 92,93 fixedly mounted on a shaft 94. The shaft 94 is rotatably mounted and is also axially movable.

Helical gears 92,93 mesh with the first and second helical gears 90,91 respectively. Accordingly gears 90,91 are co-axially aligned with one another and located adjacent to the shaft 94.

The helices of teeth on gear 90 extends in the opposite sense to the helices of teeth on gear 91 and similarly the helices of teeth on gear 92 extend in the opposite sense to the helices of teeth on gear 93.

The sense of the helices on gears 90,91 is such that loads applied by gear 90 onto gear 92 causes the gear assembly 60 to move axially toward gear 91 and such that loads applied by gear 91 onto gear 93 causes the gear assembly to move axially toward gear 90. This is illustrated diagrammatically by arrow BL in Figure 5.

As illustrated by broken arrow L gears 90,91 are in effect drivingly connected by power trains 80,81 and shaft 56. If there is more play due to manufacturing tolerances and/or wear in power train 81, the majority of power from shaft 51 will attempt to flow through power train 80. This will cause power train 80 to impose a greater load on the gear assembly 60 than power train 81. This will cause gears 90,92 to interact to move the gear assembly 60 toward gear 91 and so reduce play in the gear train 81.

Gear assembly 60 will thus float axially until the same amount of load is applied by both power trains 80,81.

The helix angle determines the amount of axial load applied upon shaft 94 for moving the gear assembly 60 axially.

Preferably the angle of the helix of teeth on gears 90 to 93 is about 30 .

However, it is appreciated that a helix angle greater or less than 30 may be adopted in order to achieve this function. For example a helix angle up to about 45 would be acceptable.

A more detailed explanation of the preferred embodiment will now be described with reference to Figures 1 to 4.

Referring initially to Figures 1 and 2 there is shown a conveyor 10 having an endless conveying means in the form of a plurality of side by side flights 11 connected together by a pair of drive chains 12.

As seen in Figure 2, the chains are located inboard of the flights 11 close to the centre line of the conveying means. This is preferred as it enables the framework of the conveyor to flex (i. e. snake) slightly along its length without impeding the movement of the flights during operation of the conveyor.

The conveyor is driven by a drive transmission unit 20 and motor 21; the transmission unit serving to transmit drive from the motor 21 to a pair of sprocket wheels 23,24 (Figure 4) which in turn are in driving engagement with chains 12.

As seen in Figures 1 and 2, the drive transmission unit 20 and motor 21 are located directly inbetween the upper run 26 and lower run 27 of the conveying means and are contained entirely within the width boundaries of the conveyor framework.

This is extremely advantageous for conveyors intended to be operated in environments of restricted space such as roadways in deep mines.

This contrasts with known systems which have a single drive shaft on which both sprocket wheels are fixedly mounted; the shaft being driven by a gearbox and motor located outside the width boundaries of the conveyor framework and thereby increasing the width dimensions of the conveyor assembly.

The transmission unit 20 illustrated in Figures 3 and 4 includes a casing 50 which rotatably supports the drive shaft 51 extending longitudinally relative to the conveyor.

In addition the casing 50 rotatably supports the driven shaft 56. The driven shaft 56 comprises two separate shaft portions 56a, 56b which are rotatably secured to one another by a drive coupling 57. The drive coupling 57 ensures that shaft portions 56a, 56b are rotatably fixed relative to one another so as to rotate in unison and so as to transmit rotary loads between one another.

Sprocket wheel 23 is mounted on shaft portion 56a and sprocket wheel 24 is mounted on shaft portion 56b via splines 58.

Preferably the drive coupling 57 is constructed so as to be capable of disassembly such that it can be completely removed from the transmission unit 20.

In this respect the drive coupling 57 includes a pair of externally toothed drive collars 150,151 secured on the splines 58 of respective shaft portions 56a, 56b. A removable end plate 153 is mounted on the terminal end of each shaft portion 56a, 56b in order to axially fix both the collar 150,151 and associated sprocket wheel 23,24 on the respective shaft portion. The drive collars 150,151 are located within an annular transmission sleeve 155 which serves to rotatably connect collars 150,151 to one another.

The transmission sleeve 155 includes a pair of annular internally toothed collars 156,157 which mesh with collars 150,151 respectively. Located inbetween collars 156, 157 is an annular spacing member 159. Collars 156,157 are detachably secured to the spacing member 159 by removable bolts 160.

An annular cover sleeve 161 is detachably secured to spacing member 159 by removable bolts 162. The cover sleeve 161 overlies bolts 160 to protect them from damage. The cover sleeve 161 is split about its circumference such that on removal of bolts 162, the split portions of sleeve 161 may be removed in a radial direction away from the spacing member 159.

Once sleeve 161 has been removed, bolts 160 are accessible and can be removed. On removal of bolts 160, the collars 156,157 may be moved axially apart to enable the sleeve 161 to be removed in the radial direction passing through the gap 165 inbetween the opposed ends of the shaft portions 56a, 56b.

After removal of sleeve 161, bolts 168 which secure end plates 153 become accessible and can be removed. This enables one or other of the collars 150,151 and sprocket wheels 23,24 to be axially withdrawn and removed through gap 165. To enable this to happen, it will be appreciated that the axial dimension of collars 150,151 and sprocket wheels 23,24 is chosen to be less than that of gap 165.

Accordingly with the preferred arrangement described above it is possible to remove one or both sprocket wheels 23,24 for repair/maintenance without the need to disassemble the remainder of the transmission unit.

It is to be appreciated that, if desired, the shaft 56 may extend continuously to define a unitary shaft upon which both sprocket wheels 23, 24 are mounted.

In the unit 20 illustrated in Figure 4, it will be seen that the gear assembly 60 includes a pinion gear 96 fixedly mounted on the shaft 94 inbetween helical gears 92,93. As seen, gears 90,91 are of a different axial extent to gears 92,93. This enables the gears 90,92 and gears 91,93 to maintain full meshing engagement whilst the transmission assembly 60 floats axially.

The pinion gear 96 is driven by a pinion gear 97 and, similarly, these gears are of a different axial extent in order to maintain full meshing engagement during axial displacement of gear assembly 60.

Pinion gear 97 is drivingly connected to the input shaft 51 via pinion gears 99,100,101,102, crown gear 103 and bevel gear 104.

The branch power trains 80,81 each comprise identical pinion gears 106, 107 and 108.

Claims

CLAIMS 1. A drive transmission unit comprising an input drive shaft, a pair of branch power trains arranged to be drivingly connected to a common driven shaft at axially spaced locations along the driven shaft, and a load balancing drive transmission means drivingly connecting the input shaft to both of said branch power trains, the drive transmission means being arranged to deliver a predetermined amount of torque to each branch power train in response to the load required to drive each branch power train.
2. A drive transmission unit according to Claim 1 wherein the drive transmission means is arranged to deliver the same amount of torque to each branch power train such that the same amount of torque is applied at each of said axially spaced locations on the driven shaft.
3. A drive transmission unit according to Claim 1 or 2 wherein the drive transmission means comprises a first helical gear drivingly connected to a first of said branch power trains, a second helical gear drivingly connected to a second of said branch power trains, the first and second helical gears being co-axially aligned, and an axially movable transmission gear assembly including third and fourth helical gears drivingly engaged with said first and second helical gears respectively, the third and fourth gears being rotatably fixed so as to rotate in unison, the first, second, third and fourth helical gears being arranged such that loads applied by the first helical gear on the third helical gear urges the transmission gear assembly in an axial direction toward the second helical gear and that loads applied by the second helical gear on the fourth helical gear urges the transmission gear assembly in the opposite axial direction.
4. A drive transmission unit according to Claim 3 wherein the transmission gear assembly includes a pinion gear, preferably located inbetween the third and fourth helical gears, said pinion gear being drivingly connected to the input drive shaft.
5. A drive transmission unit substantially as herein described with reference to and as illustrated in the accompanying drawings.
6. A conveyor having endless conveying means driven by a drive unit according to any preceding claim.