The invention relates to link connections in general, but to links for mining applications in particular, such as links in a drag line system in a mine. The invention will therefor be described with regard to such applications. The connection links differ from other links in the sense that they are separable and can be used in order to connect other links in case of breakage on one or more links or in order to connect chains.

BACKGROUND OF THE INVENTION Link connectors, as defined above, are well known in off-shore appli- cations, particularly for connecting links in anchor chains. They are easily dismantled and assembled and offer excellent fatigue and strength properties.

The links to be connected in off-shore applications are normally produced of round steel bars that are forged and welded to form generally oval links. If extreme flexibility concerning twist of loaded

chain is needed, the links might be provided with studs that contribute to a more symmetrical stress-distribution in each link.

For mining applications, the requirements are somewhat different as compared to off-shore application. Firstly, abrasive wear on the links and connectors, and hence the abrasive properties thereof, plays a more vital role than in off-shore applications, in which fatigue strength is the predominant property sought for. Therefore, con- ventional link and connector design for off-shore applications is not optimal for mining applications.

Secondly, the chains in mining applications, such as drag line chains, are often subjected to forces and movements that will tend to twist the chain. For obvious reasons, such twisting should be avoided. However, the link design used for links for off-shore appli- cations, that is generally o-shaped links made out of forged round bars with a generally circular or slightly oval cross section, is not satisfactory in many mining applications, since it will make the chain too susceptible to twisting. Since a chain is not stronger than its weakest link, also the connectors should be constructed in such a way so as to avoid twisting of the chain.

As to mining industry applications, the link parts of contemporary link connectors in that technical field are often connected by welding the respective parts to each other. This is a relatively time consuming and, thereby, costly operation.

OBJECT OF THE INVENTION The object of the invention is to provide link connector with a design that promotes its resistance to abrasive wear and resistance against

twisting. It is also an object to provide a link connector that is par- ticularly suited to mining applications, such as in drag lines.

The link connector shall be easily dismantled and assembled in order to reduce to a minimum the standing times for replacement of damaged or worn out links with connectors, since such standing times are often very costly in many industrial applications, such as mining application.

The connector design shall also be such that the connector can present a dimension and strength (including fatigue and wear resistance) properties corresponding to the dimension and strength properties of any link that it might replace in a given chain.

BRIEF DESCRIPTION OF THE INVENTION The object of the invention is achieved by the initially defined link connector, characterised in that at least one of the base portions presents an inner surface that extends generally straight from the adjacent first to the adjacent second leg of the link part to which it belongs. Straight will mean that at least a part of the surface follows a straight line between the two adjacent legs.

Preferably, said inner surface is connected to the inner surfaces of the adjacent first and second leg, the inner surfaces of said legs extending in parallel to each other and generally perpendicularly to the inner surface of the base portion. In other words, at least one base portion, preferably both, and the adjacent first and second leg define a generally right-angled, U-shaped inner periphery. Thereby, provided that a link to which the connector is connected has a corresponding shape, the connection between connector and link or connector and connector will be favourable from an abrasion

resistance point of view. The connection between connector and link or connector and connector will also induce an excellent resistance to twisting if the above principle is followed.

According to a preferred embodiment the base portion defining the straight surface presents a bevel. In other words, the surface slopes in a direction perpendicular to the direction of the straight line be- tween the legs of the link part. The inner surface of the base portion is thus rounded and presents a smooth transition to the adjacent lateral parts of the base portion of the link part. Thereby, a mobile but still twist resistant connection to a link or connector having a corresponding shape is promoted. The profile of the rounded inner surface preferably corresponds to the inner curvature of a link to which it is to be connected, such that a large contact area between said inner surface and the link is obtained.

The inner surfaces of the legs are preferably plane and parallel to each other in order to provide supporting surfaces for a link or a connector that has correspondingly plane lateral surfaces.

Accordingly, the base portion of one or, preferably, each of the link parts of the inventive connector presents lateral surfaces that are plane in order to be in firm contact with said inner surfaces. Pre- ferably, the links to which the connector is connected are provided with corresponding inner leg surfaces and lateral surfaces on the base portion thereof.

The invention also relates to the use of the inventive link connector as a separable link in a chain for mining operations. It particularly relates to a connector used as a separable link in a chain, the non- separable links of which presents a generally rectangular cross- section.

Further features and advantages of the present invention are presented in the following detailed description and in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS A preferred embodiment of the invention will now be described by way of example with reference to the annexed drawings on which: Fig. 1 is a perspective view of one embodiment of the inventive connector in an assembled state, connected to an adjacent link in a chain; Fig. 2 is a front view of the connector in fig. 1 ; Fig. 3 is a side view of the connector in figs 1 and 2; Fig. 4 is a cross-sectional front view of the connector in figs 1-3; Fig. 5 is a front view of a link part of the connector in figs. 1-4; Fig. 6 is a cross-sectional view according to VI-VI in fig. 5; Fig. 7 is a cross-sectional view according to VII-VII in fig. 5; Fig. 8 is a cross-sectional view according to VIII-VIII in fig. 5; Fig. 9 is a front view of an intermediate supporting part of the connector, and; Fig. 10 is a side view of the supporting part in fig 9;

DETAILED DESCRIPTION OF THE INVENTION The link connector according to the invention preferably defines a link or a substitution for a regular link in a chain for mining operations, in particular a drag line chain for conveying drag line buckets or the like in a mine. It is preferably used as a separable link in a chain, the non-separable links of which presents a generally rectangular cross-section.

The link connector according to the invention comprises a first and a second link part 1,2. Each link part comprises a first and a second leg 3,4 and a base portion 5, forming one single homogenous body.

Each first leg 3 defines a male part and each second leg 4 defines a female part. The male and female parts have matching or corresponding designs, enabling a locking engagement between the male part of a first link part 1 and a female part of a second link part 2, and vice versa.

The connector also comprises an intermediate part 6, designed so as to be located between and supporting the legs of the opposite link parts 1,2. The intermediate part 6 is preferably a separate part but could be a part of any of the link parts 1, 2. Apart from its main task as a locking element to be inserted between the link parts 1, 2, the position and function of the intermediate part 6 corresponds to those of a conventional stud in a chain link. Here, each leg provided with a female part comprises a support surface with which the intermediate part 6 is to be in supporting contact, and at least one, here two, heel portion (s) 7 for engagement with a corresponding heel 8 on the intermediate part 6.

A respective bore is arranged in the link parts 1, 2 and the intermediate part 6, such that these bores are in alignment and coaxial with each other when the link parts 1,2 and the intermediate part 6 are in operative engagement with each other. The bores of the parts 1,2 and 6 thereby defines a bore 9 arranged for receiving a member 10, here a pin, for further securing the respective parts 1,2,6 in relation to each other. Preferably, the bore 10 presents a varying width such that the pin 10 is prevented from being pushed all the way through the connector. For the same purpose the pin 10 is preferably conical, with a conicity of, for example, 2 %.

There is provided a locking member 11, here a socket head cap screw or the like, for locking the securing member 10 in its position in the bore 9. At least one of the bores of the first and second link part 1,2 presents a threaded portion 12 at an outer end part thereof and the locking member 11 presents a correspondingly threaded part to be engaged with said threaded portion 12. Preferably, the locking member 11 is made of a heat resistant and abrasion resistant material, which, in addition to the use of the threaded joint, makes it suitable for conditions confronted in mining applications. Steel is a preferred material for the locking member 11.

With reference to figs. 1-8 in particular, the geometrical design of the link parts 1,2 will now be discussed.

A brief description of how the link parts of the connector are manufactured will help to clarify how the shape thereof has been obtained.

Preferably, the body formed by the legs 3,4 and the portion 5 is made of steel that is forged and then machined to the final shape of the respective link part 1,2. The link parts 1,2 are produced by forging

blanks of rectangular steel rod to a desired shape, and then forming the male and female parts of the legs 3,4 by machining. However, there may be alternative ways of forming the male and female parts, depending on, e. g., the material, their shape or the specific application. The plane surfaces inherent in the rectangular blank are taken advantage of for the purpose of achieving large contact areas between the connector and the links to which the latter is connected.

The link parts 1,2 of the connector are generally U-shaped, the shape preferably being obtained by subjecting the blank to a bending operation. The base portion 5 presents an inner surface 13, i. e. a surface that is directed towards the interior of the link part and that will be in abrasive contact with the inner periphery of a link connected thereto. The inner surface is bevelled or D-shaped such that it forms a rounded transition to the adjacent opposite lateral surfaces 14, 15 of the base portion 5, as is best seen in figs. 1,2 and 5-8. However, it extends along at least one straight line between the adjacent inner surfaces 16,17 of the adjacent legs 3,4. The inner surfaces 16,17 are parallel, plane, opposite surfaces that face each other and that define support surfaces for the lateral surfaces of a link or link connector connected to the connector in question. The straight line or lines along which the inner surface extends extend perpendicularly to the inner surfaces 16,17 such that, along that line or lines, a cross section of the link part 1,2 will present a generally rectangular inner periphery, apart from the open part thereof opposite the base portion 5. The rectangular shape contributes to a rigid and twist-preventing connection between connector and link.

The inner surface 13 of the base portion 5 defines at least one generally flat region in a plane generally perpendicular to the planes of the adjacent leg surfaces 16,17. The width of said region is generally the same as the width of the inner surfaces 16,17 of the

legs 3,4 where they intersect each other. This can be seen in fig. 1 and 6. The width of the flat region or regions of the inner surface 13 of the base portion 5 decreases or narrows towards the middle between the legs 3,4. The width of the flat, parallel regions of the leg surfaces 16,17 decrease in a direction towards the base portion 5.

As is shown in fig. 2, also the first and second leg 3,4 adjacent to the base portion 5 present corresponding bevels 18, smoothly going over, via an obtuse angle at the intersection thereof, into the bevel 19 of the base portion in a transition region between base portion 5 and adjacent legs 3,4.

The width of the bevel or bevels 18, 19, in the direction of the straight extension line of the inner periphery of the base portion 5, increases in a direction perpendicular to said direction towards the outer peripheral surface 20 of the base portion 5. Thereby, sharp contact edges between connector and link that would enhance abrasive wear are avoided.

It will be realised that a number of alternative embodiments of the inventive connector will be obvious for a man skilled in the art without going beyond the scope of this invention as defined in the appended claims, supported by the description and the annexed drawings.

It should be understood that the first and second link parts 1,2 are generally identical to each other, such that they can be produced by means of the same forging tool and machined in the same way. The only difference between first and second link part 1,2 being the configuration of the bore 9 in the respective parts and the existence of the threaded portion 12 being provided in one of the parts for the accommodation of the locking member 11.

Note that in fig. 1, a link 21 connected to the inventive connector is shown, and that the width and shape of the inner periphery corresponds to the width and shape of the link portion that is in direct engagement with and projects through the opening 22 of the connector, only permitting pivoting movement of the link around the base portion 5 of the connector. However, the distance between the intermediate portion 6 and the inner surface 13 or the base portion 5 is substantially larger than the thickness of the link or the thickness of the base portion 5 of connector itself, thereby permitting a translation movement of the link between the inner surface 13 and the intermediate portion 6. Also note that the length of the link connector should be the same as any link in a chain that it is to replace, in order to avoid a change in the length of the chain due to link replacement.

The distance between the lateral surfaces 14,15 of the base part correspond to the distance between the inner leg surfaces 16,17, such that a firm connection between separate link connectors can be obtained.