GB2050282A

GB2050282A - Improvements in or relating to chain tensioners

Info

Publication number: GB2050282A
Application number: GB7918343A
Authority: GB
Original assignee: Coal Industry Patents Ltd
Current assignee: Coal Industry Patents Ltd
Priority date: 1979-05-25
Filing date: 1979-05-25
Publication date: 1981-01-07

Abstract

A chain tensioner for a coal face installation incorporates a sprocket 24 over which the haulage chain 10 is passed and then anchored at 30. The sprocket 24 is mounted on a slide arrangement which is attached through a chain 44 to a ram 32 operable to move the sprocket 24 and thus tension the chain 10. <IMAGE>

Description

SPECIFICATION Improvements in or relating to chain tensioners This invention concerns improvements in and relating to chain tensioners and has particular, but not exclusive reference to such tensioners for use on a mineral face.

In modern coal mining, mineral mining machines are employed to traverse the face winning coal removed from the face by rotary cutters mounted on the body of the machine. A conveyor is located along the face and serves to transport the won coal and to guide the machine which can be moved along the face in a number of ways. At present and for many years past, the conventional method of effecting machine movement is to locate along the face a tensioned chain with which a drive mechanism on the machine engages. The mechanism is generally in the form of a sprocket array which meshes with the chain to enable the machine to climb along the chain.

During use, the chain extends and thus it is necessary to provide resilient anchorages or tensioners to compensate for the slack generated in the chain. If such anchorages were not provided slack chain would tend to bunch in the vicinity of the sprocket array which can cause excessive wear resulting in a reduction of the cross-sectional area of the haulage chain. With high tensile loading, such a weakening of the chain will ultimately result in chain failure. It is not uncommon for the haulage chain to be pre-tensioned to 59.78 N x 103 and thus when the stored energy of the chain is released considerable injury or damage can be inflicted on personnel and equipment.

The resilient anchorages used hitherto can cater for a chain extension less than required in practice.

For example, one type of tensioner can accommodate only .76 m whereas a chain extension of 2m can be experienced.

An object of the present invention is therefore to provide an improved chain tensioner capable of accommodating a chain extension in excess of that handled by conventional tensioners.

According to the invention, a chain tensioner includes a fixed anchorage to which a chain is attachable, a rotary member over which the chain deflectable prior to attachment, in use, to the fixed anchorage, the rotary member being slidably mounted and being linearly movable with respect to the fixed anchorage by tensioning means.

The rotary member is preferably a chain engageable sprocket which may conveniently be rotatably mounted in a slidable support housing.

The tensioning means may advantageously be in the form of at least one fluid operable ram securely fixed in a casing, the ram being connected to the support housing through the agency of a connecting member.

The connecting member is conveniently flexible and may be in the form of a chain.

There are preferably two rams advantageously arranged substantially horizontally one above the other having their lines of action substantially para Ilel with the orientation of the connecting member.

The cylinders of the rams are fixed to the casing while their piston rods carry an entrapment for the connecting member.

A power source for the tensioning means is conveniently provided.

By way of example only, one form of chain tensioner according to the invention is described below with reference to the accompanying drawings in which: Figure lisa diagrammatic plan view of a mining installation incorporating the chain tensioner of the present invention; and Figure 2 is a more detailed side elevation of the right hand end of the installation of Figure 1.

Referring to the drawings, a mining installation is referenced generally at 1 and is of the type employed at a coal face. The installation includes an armoured face conveyor 2 which feeds at the right hand end as viewed in Figure 1 onto a stage loader conveyor 4. A mining machine 6 is mounted on the face side of the conveyor 2 and is of the double-ended ranging drum shearer type which travels in the seam when the cutting drums 8 are winning coal therefrom. A haulage chain 10 extends for the most part along the face side of the conveyor 2 and passes through a re-router arrangement 12 near each end of the conveyor, the arrangement 12 turning the chain through 180 and guiding the ends of the chain 10 onto the goaf side of the conveyor 2 where the ends of the chain 10 enter chain tensioners 20.

Each chain tensioner 20 comprises a plate 12 provided with a suitable aperture (not shown) through which the chain 10 can extend. A sprocket 24 is rotatably mounted in a slidable support housing 26 which runs within an outer casing 28. The chain 10 in use is deflected round the sprocket 24 through 1800 and is passed through the housing 26 and casing 28 to be anchored at 30.

Tensioning means in the form of two hydraulically actuable rams 32 are horizontally disposed in a fixed casing 34, the rams being orientated one above the other. The cylinder 36 of the rams 32 are fixed to the casing 34 whilst their piston rods 38 carry a chain plate 40 which engages a connecting member in the form of a chain 44. The chain 44 extends from the plate 40 and terminates and is fixed to the slidable support housing 26.

In operation, when the machine 6 is cutting towards the main gate end, that is the right hand end as viewed in the drawings, in the chain tensioner at the main gate end the chain 10 pulls the sprocket 24 and housing 26 to the right until the housing abuts an end stop 40. The slack in the chain 10 is taken up by the rams 32 of the tensioner at the tailgate end, that is the left hand side of the drawing of Figure 1, of the installation 1.

In one example, the rams 32 are supplied with pressure fluid from a pump (not shown) at a pressure of at least 1200 1 bflin2 (82700 x 103 N/m2) which will give a tension of 13.5 tonf (134.5 x 103N) in the chain 44, and thus 6.75 tonf (67.25 x 103N) in the chain 10. In this example, a flow rate of 12 gall/min (90.9 x 10-5 m3/s) is required to ensure efficient response in the action of the rams 32 to take up the chain when the machine 6 changes direction.

Thus, when the machine 6 has completed its traverse to the maingate nd, the reversal in direction is effected and the chain tensioners at each end reverse their roles.

As the rams 32 have a stroke of 3'6" (1.065 m) the tensioners are capable of absorbing twice their length in chain extension by virtue of the sprocket arrangement.

Since the fluid pressure applied to the rams 32 is constant, the tension in the chain 10 can be maintaind constant over the full stroke of the rams. This is in contradistinction to conventional chain tensioners which usually comprise a spring and are therefore limited to the characteristics of the spring: as the stroke increases, the pretension applied to the haulage chain decreases. Furthermore, the anchor plate 30 can be used easily to adjust the length of the haulage chain 10.

It is also possible to provide a load cell 50 as shown in Figure 2 whereby the load in the chain 10 can be read off directly.

The present invention thus provides a relatively simple and effective chain tensioner possessing advantages over conventional tensioners.

Claims

1. A chain tensioner including two fixed anchorages to which a length of chain is attachable at each of the ends thereof, two rotary members over which the chain is deflectable prior to attachment, in use, to the fixed anchorages, the rotary members being slidably mounted and linearly movable with respect to the fixed anchorages by tensioning means.

2. A chain tensioner according to claim 1 in which each rotary member is a sprocket rotatably mounted in a slidable support housing.

3. A chain tensioner according to claim 2 in which each tensioning means comprise at least one fluid operable ram fixed to a casing, the movable portion of the ram being connected to the support housing through the agency of a connecting member.

4. A chain tensioner according to claim 3 in which the connecting member is flexible.

5. A chain tensioner according to claim 4 in which the connecting member is a chain.

6. A chain tensioner according to any one of the claims 3 to 5 in which the or each ram is horizontally disposed with its line of action parallel with the orientation of the connecting member.

7. Achain tensioner according to any one of the preceding claims in which each fixed anchorage is a plate provided with an aperture for the extension therethrough of the chain.

8. A chain tensioner according to claim 7 in which a load cell is provided adjacent each plate and is adapted to measure the load in the chain.

9. A chain tensioner substantially as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawings.

New claims or amendments to claims filed on 2/4/80 Superseded claims 1 to 9 New or amended claims:- 1 to 9 CLAIMS

1. A chain tensioner including a fixed anchorage to which a chain is attachable, a rotary member over which the chain is deflectable priorto attachment, in use, to the fixed anchorage, the rotary member being slidably mounted and linearly movable with respect to the fixed anchorage by tensioning means.

2. A chain tensioner according to claim 1 in which the rotary member is a sprocket rotatably mounted in a slidable support housing.

3. A chain tensioner according to claim 2 in which the tensioning means comprise at least one fluid operable ram fixed in a casing, the movable portion of the ram being connected to the support housing through the agency of a connecting member.

7. A chain tensioner according to any one of the preceding claims in which the fixed anchorage is a plate provided with an aperture for the extension therethrough of the chain.

8. A chain tensioner according to claim 7 in which a load cell is provided adjacent the plate and is adapted measure the load in the chain.