Clamp assembly

A clamp assembly which includes two spaced apart jaw systems each of which has two sets of spaced apart relatively pivotal grip formations, wherein the jaw systems are relatively pivotally movable to position the four sets of grip formations at spaced apart locations on a circumference of a circle, wherein the size of the circumference is determined at least by the extent of relative pivotal movement of the jaw systems.

BACKGROUND OF THE INVENTION

This invention relates to a clamp assembly.

The invention is concerned particularly with a clamp assembly which is suitable for use with an elongate cylindrical component such as a pipe or tube which may form part of a drill string which is used in a drilling operation. The invention is described with reference to this application but this is exemplary only and non-limiting.

During drilling operations and thereafter, e.g. when lining a borehole, elongate lengths of drill rods or casings which are axially aligned must be screwed together, or unscrewed so that they can be separated. Drilling conditions can be arduous and it is important to be able to secure a pipe or casing with ease so that the requisite forces can be applied for coupling or uncoupling operations, as may be required.

A further factor is that drill rods, for example, come in a range of standard sizes and a clamping system suited for a drill rod of one size may not work satisfactorily with a drill rod of a different size.

An object of the present invention is to address, at least to some extent, the aforementioned requirements.

SUMMARY OF THE INVENTION

In a broad sense the invention provides a clamp assembly which includes two spaced apart jaw systems each of which has two sets of spaced apart relatively pivotal grip formations, wherein the jaw systems are relatively pivotal to position the four sets of grip formations at spaced apart locations on a circumference of a circle wherein the size of the circumference is determined at least by the extent of relative pivotal movement of the jaw systems.

More particularly the invention provides a clamp assembly which includes:

support structure with a reference plane;

first and second jaw systems;

wherein the first jaw system and the second jaw system are substantially identical to each other and each jaw system respectively includes:

a support member which is mounted to the support structure for limited relative rotation about a first pivot axis;

a first grip member which is mounted to the support member for limited relative rotation about a second pivot axis;

first grip formations on the first grip member;

a guide lever which is mounted, at one end, to the support structure for limited relative rotation about a third pivot axis and, at an opposing end, to the first grip member for limited relative rotation about a fourth pivot axis;

an actuator which acts between the support structure and the support member;

a second grip member which is mounted to the support member; and

second grip formations on the second grip member;

wherein the first pivot axis, the second pivot axis, the third pivot axis and the fourth pivot axis are parallel to one another and to the reference plane,

wherein the first jaw system is located on a first side of the reference plane and the second jaw system is located on a second side of the reference plane, the jaw systems are disposed in opposing orientations, whereby the first grip formations of the first jaw system are spaced from and oppose the first grip formations of the second jaw system; and
the second grip formations of the first jaw system are spaced from and oppose the second grip formations of the second jaw system; and wherein
the first jaw system and the second jaw system are interconnected so that, upon operation of at least one actuator, the support members of the first and second jaw systems are constrained to move angularly through arcs of equal size but in opposing senses of rotation.

The support structure may be of any suitable form and, in one form of the invention, is in the nature of a pedestal with opposed legs and a crosspiece between the legs.

The respective support member in each jaw system may be of any suitable kind and, for example, may be in the nature of a clevis formed by first and second spaced apart clevis plates.

In each jaw system the first grip member may be mounted between the first and second clevis plates.

The actuator may be of any appropriate kind and, for example, may comprise a piston and cylinder assembly which may be operated by means of a pressurised fluid e.g. compressed air or a hydraulic fluid.

The jaw systems may be interconnected by means of meshing gears, provided on the first and second jaw systems, which may be in the nature of spur gears.

The second grip members of the two jaw systems may be positioned so that the second grip formations are relatively close to each other.

The configuration of the clamp assembly may be such that the first grip formations of the two jaw systems are movable between first limiting positions at which there is a maximum spacing between the two first grip formations, and second limiting positions at which the first grip formations of the jaw systems are substantially adjacent each other and are substantially adjacent the second grip formations.

DESCRIPTION OF PREFERRED EMBODIMENT

FIG. 1of the accompanying drawings illustrates, in perspective, a clamp assembly10according to the invention.FIG. 2shows the clamp assembly in elevation with certain components on an outer side of the clamp assembly omitted in order to illustrate various internal constructional details of the clamp assembly.

The clamp assembly includes support structure12, a first jaw system14and a second jaw system16.

The support structure12is, in this form of the invention, in the form of a pedestal and includes opposing pairs of legs20and22respectively and a crosspiece24at an upper end of the legs.

The first and second jaw systems are for all practical purposes identical to each other. The first jaw system14is on one side of a centrally positioned reference plane30which passes through the support structure. The second jaw system16is on an opposing side of the reference plane. The jaw systems are oppositely orientated i.e. viewed from one side, one jaw system is a mirror image of the other. For this reason the construction of the first jaw system14only is described hereinafter.

The jaw system14includes a support member32which is in the nature of a clevis and which includes a first clevis plate34, a spaced apart second clevis plate36, a shaft with aligned bushes38between the plates34and36, and a brace member40(refer to the jaw system16D inFIG. 1) which securely interconnects the plates to each other.FIG. 10illustrates, more clearly, the components34,36,38and40.

The support member32is mounted to an upper part of the leg20, and an adjacent part of the crosspiece24, for movement about a first pivot axis44which is parallel to the reference plane30.

An actuator50, in the form of a cylinder52and a piston54which has a protruding piston rod56(seeFIG. 4), is mounted at one end to a shaft60which forms a lower pivot axis62and, at an upper end of the piston rod, to the shaft and bushes38of the support member which define a pivot axis60which is parallel to the axis44.

Two parallel guide levers64(refer to the jaw system16inFIG. 1) which are spaced apart from each other are pivotally mounted to the support structure12for movement about a pivot axis68which is parallel to the pivot axis44. The levers64are connected at an upper pivot axis70to a grip member72which extends between the upper ends of the levers. The axis70is parallel to the axis44. The grip member72is located partly between the clevis plates34and36and is pivotally connected thereto by means of a shaft76which lies on a pivot axis78which is parallel to the axis44. A profiled retainer member80is engaged with an upper end of the grip member. The retainer member80carries an array of serrated grip formations84. The retainer member is designed to allow limited rotational movement of the grip formations84relative to the grip member72.

A second grip member86, is positioned between and secured to the clevis plates34and36, and is aligned on the pivot axis44. The grip member86is rotatable together with the clevis plates34and36about the axis44. A profiled retainer member88, which is fixed to the second grip member86, carries an array of second serrated grip formations90.

Each jaw system14,16carries a respective spur gear94which is fixed to an outer side of the respective clevis plates36and which is centred on the respective pivot axis44.FIGS. 1 and 2show that the two spur gears94are meshed with each other.

The various rotational surfaces, shafts and the like are mounted in bushings or bearings according to good engineering practice and are provided with grease and lubrication points as may be necessary.

The actuator50, in each respective jaw system, is hydraulically operable. If hydraulic fluid is introduced under pressure into a lower port98then the piston rod56is extended from the cylinder52. If pressurised hydraulic fluid is introduced into an upper port100then the piston rod56is retracted into the cylinder52.

FIG. 2illustrates, in outline, three elongate elements, solid or tubular, e.g. pipes or casings106,108and110respectively, which have different diameters. The clamp assembly of the invention is designed to deal with cylindrical elements which can have diameters lying in a large range and the elements106,108and110are exemplary only.

FIGS. 3 and 4illustrate the clamp assembly actuated to engage with a large diameter element106.FIGS. 5 and 6show the clamp assembly engaged with a medium diameter element108andFIGS. 7 and 8shows the clamp assembly engaged with a small diameter element110.

The second grip formations90of the two jaw systems are close to one another and, in the illustrations, generally face each other. These grip formations are symmetrically located on opposing sides of the reference plane30. Assume that the cylindrical element106is positioned on the gripping formations90, as shown inFIG. 3for example. An elongate axis112of the element106normally lies within the plane30. Also the axis112is generally parallel to the pivotal axis44and thus to the other axes which have been referred to.

The two actuators50are operated as far as possible in unison. Pressurised hydraulic fluid is introduced into each cylinder52to cause the corresponding piston rod56to extend from the cylinder, as is indicated by arrows114inFIG. 3. The resulting movement is fairly complex. The support member32, i.e. the clevis, can only move in a rotational sense to and fro about the pivot axis44on each side. The levers64, which are fixed to the support structure12, pivot about the pivot axis68. The pivot axis70thus moves along an arc116—seeFIG. 4. However the grip member72is mounted to the levers64and to the clevis plates34,36and can be moved along an arc118(about the axis70) which has a smaller radius than the radius of the arc116.

Additionally, when the clevis plates34,36are pivoted, the grip member86moves about the pivot axis44.

The nature of the pivotal movement of each of the various components is such that, in one sense, it can be said that levers64are moved through a fairly large arc to bring the grip formations84rapidly to oppose an outer surface of the cylindrical element106. Further extension of the piston rod then effectively causes the grip member72to pivot about the axis70and the grip formations84are brought into tight engagement with an outer surface of the cylindrical element106.

The two sets of grip formations84are spaced apart by a distance which is less than the diameter of the element106. Also, the grip formations84are located on a line which is above a diameter of the element106which is transverse to the plane30. Thus the element106is urged towards and into tight engagement with, the grip formations90.

The two jaw systems, as described, are interlinked by means of the meshing spur gears94. Thus angular movement of one jaw system in one direction or sense is matched by angular movement of the other jaw system to the same angular extent but in a different rotational direction or sense.

The aforementioned gripping process is repeated when the clamp assembly is used with cylindrical elements which have smaller diameters than the element106. For exampleFIG. 5andFIG. 6show the clamp assembly engaged with the element108. The support members/clevis plates are pivoted to a greater extent inFIG. 5(to what is shown inFIG. 3) and the grip member72is also pivoted, about the axis78, to a greater extent inFIG. 5. In this respect the extent of pivotal movement of the grip member72is determined by the degree of pivotal movement of the support member32and the degree of pivotal movement of the grip member72, relative to the support member32.

As is shown inFIG. 5the grip formations84are engaged with a surface of the element108at a location which causes the grip formations to push the element towards the second grip formations90.

In the configuration shown inFIGS. 7 and 8the clamp assembly has been actuated to another limiting position. The support members32are pivoted away from the respective actuators50to a maximum extent and the corresponding grip members72are pivoted inwardly and downwardly to a maximum extent. The grip formations84of the two jaw systems are substantially adjacent each other. These Figures represent a situation in which the clamp assembly is used with the small diameter element110.

It is apparent from the comparison ofFIGS. 3 and 4, 5 and 6 and 7 and 8that the clamp assembly is actuable to position the four sets of grip formations on the circumferences of respective circles of different diameters. Each elongate element, in cross-section, has a circular outline of a particular diameter. The relative pivotal movement of the jaw systems which, via the linkages referred to cause corresponding and controlled movement of the gripping formations, is such that the gripping formations are caused to take up positions spaced apart from one another which lie on the circumference of the particular tubular element which is engaged with the clamp assembly.

FIG. 9illustrates in perspective a kicker assembly200which is usable in conjunction with the clamp assembly10. The kicker assembly is constructed about a longitudinal axis202which in use is positioned on the plane30.

The kicker assembly has a supporting arrangement204which extends to opposed sides of the plane30and, fixed to the arrangement204, are two inwardly and downwardly inclined kicker arms206and208respectively. These arms are bent and positioned so that, in use, they underlie a lower surface of an elongate element (106,108or110, by way of example only), which is engaged with the jaw assembly10. The kicker arms are pivotally mounted at points210,212to the arrangement204and are acted on by respective hydraulic actuators216and218respectively which are fixed to the arrangement204. Additionally, links220and222pivotally connect the kicker arms to the arrangement204.

In use an elongate element with which the clamp assembly10is engaged lies in a cradle formed by the shaped kicker arms206,208. In order to lift the elongate element from the clamp assembly, the jaw systems thereof are released and, thereafter, the actuators216and218are energised and, in the process, the kicker arms206and208are pivoted about the points210and212. This lifts the elongate element from the clamp assembly and helps to unload the element from the clamp assembly. The use of the kicker assembly facilitates the way in which the clamp assembly is employed.

An advantage of the invention lies in the fact that the clamp assembly can be actuated rapidly and precisely, using suitable hydraulic control techniques. The actuators (piston and cylinder assemblies) are operated with ease and exert significant clamping forces on an elongate element e.g. pipe or casing, as the case may be, which is positioned to lie on the grip formations90. There is no need to adjust the clamp assembly beforehand so that it can work with pipes of different diameters. It is possible to use a pressure release valve or a pressure sensor which detects the maximum pressure in the actuators—this parameter determines the clamping force applied by the gripping formations. Thus, irrespective of the diameter of the element with which the clamp assembly is used, an automatic technique can be implemented to ensure that a suitable clamping force is applied to the pipe or casing and that the clamping force is not so high as to cause damage to the element.

The clevis plates34and36can if necessary be replaced with plates of different sizes to enable pipes, which lie in a different range of sizes, to be gripped. This adjustment can be done without changing the remaining components.

The retainer members80and88, which carry the grip formations, are wear items and will require replacement. The design of the clamp assembly is such that these items, when worn, can be removed and can then be replaced with new parts.

As is shown, for example inFIG. 2, the jaw systems14and16can be spread wide apart to positions which facilitate loading of a pipe into the clamp assembly from, for example, an automatic pipe feeding device. There is virtually no restriction in this regard. The clamp assembly can be used effectively with any pipe provided an included angle between the opposing sets of grip formations84, when they are brought into contact with an outer surface of the pipe, is at least 180°.