GB2501826A

GB2501826A - Clamp for use with a drill

Info

Publication number: GB2501826A
Application number: GB201307696A
Authority: GB
Inventors: Damian Ghoddusi
Original assignee: BAE Systems PLC
Current assignee: BAE Systems PLC
Priority date: 2012-05-03
Filing date: 2013-04-29
Publication date: 2013-11-06
Anticipated expiration: 2033-04-29
Also published as: GB201307696D0; GB201207753D0; GB2501826B

Abstract

The clamp 20 includes clamp arms 24, 26 with the first clamp arm including a bore 28 through which a cutting tool of a drill may move. The second clamp arm includes a cavity 34 into which the cutting tool of the drill may move. The longitudinal axis of the bore 28 and the cavity 34 are aligned. If an object is clamped and the cutting tool is moved through the bore 28 to contact the object, a portion of the object that is in contact with the first clamp arm 24 surrounds the point on the object contacted by the cutting tool. If an object is clamped and the cutting tool is moved through the bore 28, through the object, and into the cavity 34, a portion of the object that is in contact with the second clamp arm 26 surrounds a point on the surface of the object at which the cutting tool exits the object and enters the cavity 34. The first clamp arm 24 may include a threaded bore to receive a removable drill bush (8, Figure 3).

Description

CLAMP

FIELD OF THE INVENTION

The present invention relates to clamps.

BACKGROUND

During drilling operations, a C -clamp (also known as a G-clamp) may be used to clamp together an object to be drilled, a block, and a drill bush.

Figure 1 is a schematic illustration (not to scale) of a C-clamp 2 clamping together an object to be drilled 4, a block 6, and a drill bush 8.

The block 6 and the drill bush 8 each comprise an axial bore through their structure. The block 6 and the drill bush 8 are clamped together such that these axial bores are aligned to form a bore 10 (that is indicated in Figure 1 by dotted lines). During drilling of the object 4, a cutting tool of a drill is passed through the bore 10, in the direction the arrow 12 shown in Figure 1, to contact with, and cut (or drill) into the surface of the object 4.

When the object 4 is drilled, the drill tends to exert a force on the object 4 in the direction of the arrow 12. The portion of the object 4 that is being drilled (i.e. the portion of the object 4 upon which the force is exerted by the drill) is laterally spaced from the portion of the object 4 that is clamped by the C-clamp 2. Thus, during drilling, the object 4 may move, or pivot, around the point at which it is clamped by the C-clamp 2.

Furthermore, when drilling through objects made of certain materials (e.g. carbon fibre composite material), as the cutting tool of the drill exits the object, delamination, or debonding, of the object may occur. This tends to adversely affect the integrity of the object. Repairs of a delaminated object tend to be expensive, difficult, or even impossible.

SUMMARY OF THE INVENTION

In a first aspect, the present invention provides a clamp comprising a first clamp arm and a second clamp arm, wherein the first and second clamp arms are moveable relative to one another such that an object may be clamped between the first and second clamp arms, the first clamp arm comprises an bore through which a cutting tool of a drill may be moved, the second clamp arm comprises a cavity in to which the cutting tool of the drill may be moved, a longitudinal axis of the bore is substantially aligned with a longitudinal axis of the cavity, and the first and second clamp arms are configured such that: if an object is clamped between the first and second clamp arms and the cutting tool of the drill is moved through the bore of the first clamp arm such that it comes into contact with the object, a portion of the surface of the object that is in contact with the first clamp arm substantially surrounds a point of the surface of the object that is in contact with the cutting tool of the drill, and if an object is clamped between the first and second clamp arms and the cutting tool of the drill is moved through the bore of the first clamp arm, through the object, and into the cavity, a portion of the surface of the object that is in contact with the second clamp arm substantially surrounds a point on the surface of the object at which the cutting tool exits the object and enters the cavity.

The second clamp arm may comprise an elongate threaded member, the rotation of which moves a portion of the second clamp arm in towards or away from the first clamp arm.

The portion may have a hexagonal cross section.

The first clamp arm may be adapted to securely attach to a drill bush such that the bore of the first arm is aligned with a bore of the drill bush.

The cavity may be filled with a replaceable material.

The clamp may be substantially C-shaped In a further aspect, the present invention provides a method of drilling an object, the method comprising: providing a clamp according to the above aspect, clamping the object between the clamp arms of the clamp, and moving a cutting tool through the bore and into the object to some extent.

The cutting tool may be moved completely through the object and into the cavity.

A first drill bush may be attached to the first clamp arm and a first drilling operation on the object may be formed. Subsequently, the first drill bush may be replaced by a second drill bush (e.g. having a different diameter), whilst retaining the object between the clamp arms and a second drilling operation may be performed on the object.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic illustration (not to scale) of a C-clamp clamping together an object to be drilled, a block, and a drill bush.

Figure 2 is a schematic illustration (not to scale) of a perspective view of an embodiment of a clamp; and Figure 3 is a schematic illustration (not to scale) of the clamp in use.

DETAILED DESCRIPTION

In the following description, like reference numerals refer to like elements. The following description is based on embodiments of the invention and should not be taken as limiting the invention with regard to alternative embodiments that are not explicitly described herein.

The terminology "drilling" is used herein to refer to any process in which a cutting tool is used to cut in a surface of an object, for example, countersinking, reaming, centring, counterboring, tapping, thread cutting etc. Figure 2 is a schematic illustration (not to scale) of a perspective view of an embodiment of a clamp 20.

The clamp 20 comprises a C-shaped member 22. The C-shaped member 22 may equivalently be thought of as a U-shaped member. A first end 24 of the C-shaped member 20 is opposite to a second end 26 of the C-shaped member 22.

The first end 24 of the C-shaped member 22 comprises an axial bore 28 through the structure of the first end 24. The axial bore 28 will be described in more detail later below.

The second end 26 of the C-shaped member 22 comprises a hexagonal prism shaped member 30. The hexagonal prism shaped member 30 is fixedly attached to one end of an elongate threaded member 32. The other end of the elongate threaded member 32 (i.e. the end of the elongate threaded member 32 that is opposite to the end that is attached to the hexagonal prism shaped member 30) is screwed into the C-shaped member 22.

The hexagonal prism shaped member 30 may be moved towards the first end 24 of the C-shaped member 22 (i.e. away from the second end 26 of the C-shaped member 22) by unscrewing the elongate threaded member 32 from the second end 26 of the C-shaped member 22. This may be performed, for example, by rotating the hexagonal prism shaped member 30. The hexagonal cross section of the hexagonal prism shaped member 30 advantageously tends to facilitate gripping of the hexagonal prism shaped member 30 (e.g. by a spanner etc) to facilitate such rotation. Similarly, the hexagonal prism shaped member 30 may be moved towards the second end 26 of the C-shaped member 22 (i.e. away from the first end 24 of the C-shaped member 22) by screwing the elongate threaded member 32 into the second end 26 of the C-shaped member 22.

The hexagonal prism shaped member 30 comprises a substantially cylindrical shaped cavity 34. A longitudinal axis of the cavity 34 is substantially parallel to a longitudinal axis of the hexagonal prism shaped member 30. An opening of the cavity 34 is at an end of the hexagonal prism shaped member 30 that is opposite the end of the hexagonal prism shaped member 30 that is attached to the elongate threaded member 32.

In other words, the hexagonal prism shaped member 30 is a tube-like member having an open end and a closed end. The closed end of the hexagonal prism shaped member 30 is attached to the elongate threaded member 32. The open end of the hexagonal prism shaped member 30 is a free end.

The axis of the axial bore 28 through the first end 24 is aligned with the longitudinal axis of the cavity in the hexagonal prism shaped member 30. The axial bore 28 provides a guide tube that, in use, may guide a cutting tool moving through the axial bore 28 into the cavity 34.

Figure 3 is a schematic illustration (not to scale) of the clamp 20 in use.

In Figure 3 the object to be drilled 4 is clamped by the clamp 20. In this embodiment, the object 4 is made of a carbon fibre composite material.

To clamp the object 4, the object 4 is placed between the first end 24 and the second end 26. The object 4 may be placed such that it is in contact with the first end 24 of the C-shaped member 22. The hexagonal prism shaped member 30 is the moved towards the object 4 (i.e. towards the first end 24 and away from the second end 26) until it contacts with the object 4 and the object 4 is gripped tightly between the first end 24 and the hexagonal prism shaped member 30.

The portion of the first end 24 of the C-shaped member 22 that contacts the object 4 when the object 4 is held by the clamp 20 is hereinafter referred to as the "first clamp face". In this embodiment, the axis of the axial bore 28 is substantially perpendicular to the first clamp face. However, in other embodiments, the angle between the first clamp face and the axis of the axial bore 28 is a different angle.

The portion of the second end 26 of the C-shaped member 22 that contacts the object 4 when the object 4 is held by the clamp 20 is hereinafter referred to as the "second clamp face". In this embodiment, the axis of the cavity 34 is substantially perpendicular to the second clamp face. However, in other embodiments, the angle between the second clamp face and the axis of the cavity 34 is a different angle.

In this embodiment, a drill bush 8 is attached to the first end 24 of the C-shaped member 22. The drill bush 8 is attached to the first end 24 such that the axial bore through the drill bush 8 is aligned with the axial bore 28. Also, the drill bush 8 is attached to the side of the first end 24 that is opposite to the side that is in contact with the object 4. The drill bush 8 may be attached to the clamp 20 is any appropriate way, for example, the axial bore 28 may be threaded to allow the drill bush 8 to be screwed onto the first end 24. In this embodiment, the axial bore through the drill bush 8 provides a guide tube for a cutting tool of a drill, as described in more detail later below. In other embodiments, a drill bush 8 is not used. In embodiments in which a drill bush is not used, the axial bore 28 through the first end 24 may be used to as a guide for the cutting tool of a drill.

When the object 4 is clamped between the first end 24 and the hexagonal prism shaped member 30, the axial bore through the drill bush 8, the axial bore 28 through the first end 24, and the cavity 34 in the hexagonal prism shaped member 30 are all aligned, i.e. the longitudinal axes of the axial bore through the drill bush 8, the axial bore 28 through the first end 24, and the cavity 34 are aligned.

Drilling through the object 4 is performed by moving a cutting tool of a drill along the arrow 36 shown in Figure 3. In other words, the object 4 may have a hole drilled through it by moving the cutting tool of a drill firstly through the axial bore in the drill bush 8, secondly through the axial bore 28 through the is first end 24, thirdly through the object 4, and fourthly into the cavity 34.

The diameter of the cutting tool is less than, or substantially equal to, the diameter of each of the axial bore through the drill bush 8, the axial bore 28 through the first end 24, and the cavity 34.

The axial bore in the drill bush 8 and the axial bore 28 through the first end 24 advantageously tend to guide the cutting tool of the drill so that it moves in a direction that is substantially parallel to the longitudinal axes of the axial bore through the drill bush 8, the axial bore 28 through the first end 24, and the cavity 34.

When forming holes in the object 4 which are subject to particularly high tolerances (e.g. in size or finish), the holes are formed by performing a number of drilling operations. The diameter of the hole increases with each operation until a final sized ream cut is performed. The clamp 20 facilitates such a cumulative drilling approach with enhanced accuracy as the clamping mechanism can remain secure (thus preventing or minimising relative movement between the object and the clamp), whilst drilling bushes (8) of different (increasing) diameters can be sequentially removed and replaced, thus maintaining registration, or alignment, of the hole being formed or finished.

The portion of the object 4 that is gripped by the clamp 20 is proximate (and in this embodiment at least, surrounds) to the portion of the object 4 upon which, during a drilling operation, a force is exerted by the cutting tool. In particular, the portion of the object 4 that is gripped by the clamp 20 surrounds S the point on the front surface of the object 4 that is drilled into (and also the point on the rear surface of the object where the cutting tool exits the object).

This advantageously tends to reduce or eliminate bending of the object 4 due to application of the drilling force.

In other words, in contrast to conventional clamping methods, the portion of the object 4 that is being cut into is not laterally spaced from the portion of the object 4 that is gripped by the clamp 20. Thus, there tend to be no pivot points about which the object 4 may bend. Thus, bending of the object 4 during drilling is advantageously opposed.

Furthermore, as the rear surface of the object 4 (i.e. the surface of the object from which the cutting tool exits the object 4 as the object 4 is drilled through, i.e. the surface of the object 4 that is in contact with the hexagonal prism shaped member 30) is supported by the hexagonal prism shaped member 30 at the point where the cutting tool exits the object 4, the chances of delamination, or debonding, of the object occurring tend to be reduced or eliminated. The cavity 34 may be filled with a material (e.g. wood, or putty) which would tend to provide further support to the rear surface of the object and, thereby, further decrease the likelihood of delamination occurring. The material may be replaced after it has been drilled into. The reduction in occurrences of delamination tends to mean that fewer objects require repairing or are wasted. Thus, costs tend to be reduced.

The presence of cavity 34 allows space around the exit of the hole being formed, into which swarf or waste from the formation of the hole can pass. The absence of such a cavity can lead to build up of swarf between the clamping surface and the object leading to scratching of the surface of the object, distortion of the object and reduction in clamping efficacy.

In the above embodiments, the clamp comprises a C-shaped member.

However, in other embodiments, this member may be a different appropriate shape, e.g. a V-shaped member.

In the above embodiments, the second end of the C-shaped member comprises a cavity into which, during drilling of an object, a cutting tool of a drill may move into after having passed through the object. However, in other embodiments, this cavity may be a through-hole, i.e. an axial bore that passes through the structure of the second end of the C-shaped member.

In the above embodiments, an object is clamped by placing the object between the ends of the C-shaped member and, in effect, moving the ends closer together to grip the object (which, in the above embodiments, is effected by moving the hexagonal prism shaped member towards the first end of the C-shaped member by unscrewing the elongate threaded member from the second end of the C-shaped member). However, in other embodiments, the ends of the C-shaped member (i.e. the clamp jaws) may be moved relative to one another in a different way. For example, the jaws of the clamp may be moved about a hinge or pivot point, or using a hydraulic clamping system.

The components of the clamp may be made from any appropriate material, for example, steel.

Claims

CLAIMS1. A clamp (20) comprising: a first clamp arm (24); and a second clamp arm (26); wherein s the first and second clamp arms (24, 26) are moveable relative to one another such that an object may be clamped between the first and second clamp arms (24, 26); the first clamp arm (24) comprises a bore (28) through which a cutting tool of a drill may be moved; the second clamp arm (26) comprises a cavity (34) in to which the cutting tool of the drill may be moved; a longitudinal axis of the bore (28) is substantially aligned with a longitudinal axis of the cavity (34); and the first and second clamp arms (24, 26) are configured such that: if an object is clamped between the first and second clamp arms (24, 26) and the cutting tool of the drill is moved through the bore (28) of the first clamp arm (24) such that it comes into contact with the object, a portion of the surface of the object that is in contact with the first clamp arm (24) substantially surrounds a point on the surface of the object that is in contact with the cutting tool of the drill; and if an object is clamped between the first and second clamp arms (24, 26) and the cutting tool of the drill is moved through the bore (28) of the first clamp arm (24), through the object, and into the cavity (34), a portion of the surface of the object that is in contact with the second clamp arm (26) substantially surrounds a point on the surface of the object at which the cutting tool exits the object and enters the cavity (34).
2. A clamp (20) according to claim 1, wherein the second clamp arm (26) comprises an elongate threaded member (32), the rotation of which moves a portion (30) of the second clamp arm (26) towards or away from the first clamp arm (24).
3. A clamp (20) according to claim 2, wherein the portion (30) has a hexagonal cross section.
4. A clamp (20) according to any of claims 1 to 3, wherein the first clamp arm (24) is adapted to securely attach to a removable drill bush such that the bore (28) of the first arm (24) is aligned with a bore of the drill bush.
5. A clamp (20) according to Claim 4, wherein the first clamp arm (24) comprises a threaded bore configured to receive a threaded portion of a removable drill bush.
6. A clamp (20) according to any of claims 1 to 5, wherein the cavity (34) is filled with a replaceable material.
7. A clamp (20) according to any of claims ito 6, wherein the clamp (20) is substantially C-shaped.
8. A method of drilling an object, the method comprising: providing a clamp (20) according to any of claims 1 to 7; clamping the object between the clamp arms (24, 26) of the clamp (20); and moving a cutting tool through the bore (28) and into the object to some extent.
9. A method according to claim 8, wherein the cutting tool is moved completely through the object and into the cavity (28).
10. A method according to Claim 8 or 9, when dependent on Claim 4, comprising the steps of: attaching a first drill bush to the first clamp arm (24); performing a first drilling operation on the object; replacing the first drill bush by a second drill bush, whilst retaining the object between the clamp arms; and performing a second drilling operation on the object.