Nozzle for laser welding

Abstract

A nozzle for use with a laser beam welding machine, wherein: a proximal end of the nozzle comprises means suitable for mounting the nozzle to a laser head of a laser beam generator for generating a laser beam directed at a weld point on a workpiece; a distal end of the nozzle comprises a distal inlet opening for allowing ambient gas to enter into the nozzle; wherein the nozzle comprises: a laser beam entry opening provided at the proximal end of the nozzle for receiving the laser beam; a laser beam exit opening provided at the distal end of the nozzle for delivering the laser beam onto the workpiece; the laser beam being configured to travel from the laser beam entry opening through the laser beam exit opening to the weld point on the workpiece along an optical path extending axially through the nozzle; an outlet port fluidly connectable to a vacuum pump for suctioning gas out of the nozzle, thereby reducing the pressure at the weld point.

Description

[0001] NOZZLE

[0002] FIELD AND BACKGROUND

[0003] The present invention relates to an improved nozzle for use with a laser beam welding machine.

[0004] Laser welding is a process that uses a high-energy laser beam to irradiate a workpiece. The laser beam is focused onto a welding portion of the workpiece and melts the portion of the workpiece irradiated by the laser. The liquid pool of molten material created by the laser is called a ‘weld pool’ and as the material in the weld pool solidifies, a weld is created. The laser beam is usually moved over the workpiece by moving the laser relative to the workpiece, allowing the laser beam to form a weld line. Laser welding is often used to join two or more plates together. The end portions of two plates are butted against each other and the laser beam is swept over the butted portion, irradiating the area. The laser melts the material at the butted portion and as the material re-solidifies, a weld joint forms between the plates, joining the plates together.

[0005] The point of impact between the laser beam and the workpiece is usually referred to as the weld point and laser welding machines often include focusing lenses to better focus the laser beam at the weld point. To ensure a stable and high quality weld, the conditions at the weld point need to be controlled. In particular, high pressure at the weld point needs to be avoided as this can lead to thinning of the material at the weld point as the weld is being created, ultimately resulting in weakness in the workpiece.

[0006] The quality of the weld produced can also be affected by a number of other factors, including the degree to which ambient air is allowed to ingress into the weld area (the area surrounding the weld point), in particular during formation of the weld pool. Gases in ambient air entering the weld area and contaminating the weld pool can affect the material properties of the molten material in a number of ways, depending on the material being welded. For example, ambient or atmospheric contaminants entering the weld area can increase the porosity of the molten material, increasing the brittleness and the risk of cracking of the resulting welded workpiece. Ambient / atmospheric contaminants entering the weld area can also cause oxidation of the weld, resulting in a weld with reduced strength. To protect the weld pool from potential ambient contaminants and to reduce oxidation of the weld, laser welding is sometimes performed in a vacuum chamber, thereby minimising the gases surrounding the weld area that can contaminate the weld. However, laser welding in a vacuum chamber limits the space available for welding to the size of the chamber.

[0007] Furthermore, there are many applications where welding in a vacuum chamber is either not possible or not practical, for example when the workpiece or the parts being welded are too large to fit inside a reasonably sized vacuum chamber.

[0008] In some laser welding applications, a protection gas is provided during laser welding to protect the laser beam and any laser generating tool from potential smoke, debris and / or splashback from the weld pool. Any protection gas introduced near the weld area can interfere with the weld area and result in increased pressures being applied at the weld point, thereby reducing the quality of the weld produced at the weld point. Therefore, any advantages achieved by the use of the protection gas are compromised by the potential increase in pressure applied at the weld point from the protection gas.The present disclosure has been devised in the light of the above considerations. In particular, an invention described herein is concerned with increasing the quality of the weld produced by laser welding and reducing the pressure applied at the weld point during the welding process.

[0009] SUMMARY

[0010] Particular aspects and embodiments are set out in the appended claims.

[0011] According to a first aspect, there is provided a nozzle for use with a laser beam welding machine, wherein:

[0012] a proximal end of the nozzle comprises means suitable for mounting the nozzle to a laser head of a laser beam generator for generating a laser beam directed at a weld point on a workpiece;

[0013] a distal end of the nozzle comprises a distal inlet opening for allowing ambient gas to enter into the nozzle;

[0014] wherein the nozzle comprises:

[0015] a laser beam entry opening provided at the proximal end of the nozzle for receiving the laser beam;

[0016] a laser beam exit opening provided at the distal end of the nozzle for delivering the laser beam onto the workpiece;

[0017] the laser beam being configured to travel from the laser beam entry opening through the laser beam exit opening to the weld point on the workpiece along an optical path extending axially through the nozzle;

[0018] an outlet port fluidly connectable to a vacuum pump for suctioning gas out of the nozzle, thereby reducing the pressure at the weld point.

[0019] By providing the nozzle with an outlet port fluidly connectable to a vacuum pump for suctioning gas out of the nozzle, the pressure within the nozzle, and therefore at the weld point, is significantly reduced, thereby resulting in a high quality weld at the weld point. The vacuum pump is configured to reduce the pressure within the nozzle, for example to the order of approximately 5-10 kPa. In effect, this creates a vacuum within the nozzle, thereby significantly reducing the pressure at the weld point. By reducing the pressure at the weld point, laser welding defects such as material thinning, porosity and cracking usually occurring when the pressure at the weld point is too high, can be prevented.

[0020] Furthermore, by suctioning gas out of the nozzle, any gas or gas molecules surrounding the weld area that may contaminate the weld pool are suctioned out of the nozzle through the outlet port, thereby eliminating or significantly reducing contamination and oxidation of the weld pool and ultimately resulting in a higher quality weld.

[0021] Any reference to ambient gas may include any gas surrounding the nozzle. This may include atmospheric gas (for example, when the nozzle is used during welding in atmospheric conditions), air or any other gas that may surround the nozzle during laser welding. This may also include specific or specialised gases used during welding, for example an inert gas. The nozzle may be used during welding in a chamber (including, for example a vacuumchamber) with specific gases being used for the welding process. In these cases, reference to ambient gas may include any specialised gases used in the welding chamber.

[0022] The nozzle may be coaxially mounted to the laser head such that the central axis (e.g. the central longitudinal axis) of the nozzle is aligned with the central axis of the laser head. In this way, the laser beam may be configured to travel from the laser beam entry opening through the laser beam exit opening and to the weld point on the workpiece along an optical path extending through the central axis (e.g. the central longitudinal axis) of the nozzle. In use, the central longitudinal axis of the nozzle may be positioned substantially perpendicularly to the workpiece such that the laser beam may be projected perpendicularly onto the workpiece.

[0023] The laser beam exit opening may be centrally aligned with the central axis (e.g. the central longitudinal axis) of the nozzle, such that the laser beam may be configured to travel through the centre of the laser beam exit opening to the weld point. In effect, the weld point may be aligned with the centre of the laser beam exit opening. For example, the laser beam exit opening may be a generally circular opening concentric with the central axis (e.g. the central longitudinal axis) of the nozzle. The distal inlet opening may be centrally aligned with the central axis (e.g. the central longitudinal axis) of the nozzle. In particular, both the laser beam exit opening and the distal inlet opening may be centrally aligned with the central axis (e.g. the central longitudinal axis) of the nozzle, the laser beam exit opening and the distal inlet opening therefore being centrally aligned with each other such that the weld point may be aligned with the centre of the distal inlet opening for allowing ambient gas into the nozzle. By aligning the optical features with the fluidic features of the nozzle, the nozzle can direct the flow of gas within the nozzle so as to control the pressure at the weld point. The distal inlet opening may be a generally circular opening concentric with the central axis (e.g. the central longitudinal axis) of the nozzle. The distal inlet opening may be concentric with the laser beam exit opening, such that the distal inlet opening may surround the laser beam exit opening.

[0024] The outlet port may be provided towards the proximal end of the nozzle. In this way, ambient gas can be suctioned into the nozzle from the distal inlet opening, travel through the nozzle and out through the outlet port.

[0025] The outlet port may be provided radially spaced from the central axis (e.g. the central longitudinal axis) of the nozzle. For example, the outlet port may be provided along a perimeter wall of the nozzle. In this way, gas may be suctioned into the nozzle from the distal inlet opening along the inner periphery walls of the nozzle. This can prevent the suctioning of gas into the nozzle along the central axis of the nozzle and therefore avoid the weld point, thereby further maintaining low pressures at the weld point.

[0026] The nozzle may comprise a plurality of outlet ports, for example 2, 3, 4 or 4+, depending on the amount (i.e. volume) of gas that may be required to be discharged from the nozzle or the size of the nozzle and the space available for the outlet ports. For example, the nozzle may comprise four outlet ports. The outlet ports may be symmetrically disposed about the central axis of the nozzle so as to better capture the spread of gas entering the nozzle. The outlet port may comprise a circular or annular cross section.In some embodiments, the proximal end of the nozzle may be sealed off to ambient gas. For example, the laser beam entry opening may comprise a clear window (e.g. a clear glass window) which seals off the laser beam entry opening to ambient gas from entering the nozzle while allowing the laser beam to pass through the opening and into the nozzle. In such embodiments, the only inlet for ambient gas into the nozzle may be the distal inlet opening.

[0027] As gas is suctioned in from the distal inlet opening and out through the outlet port(s), gas entering the distal inlet opening can result in elevated pressures at the weld point. In particular, the vacuum created within the nozzle can cause ambient gas to jet along the horizontal surface of the workpiece, radially towards the weld point and into the nozzle from the distal inlet opening. The gas jets entering from the distal inlet opening may converge at the weld point (e.g. at the centre of the nozzle) and increase the pressures at the weld point. To prevent the jets of incoming gas entering the nozzle at the distal inlet opening from converging and colliding at the weld point, the distal inlet opening may comprise a first deflector configured to deflect the incoming gas and / or gas jets axially into the nozzle before the gas reaches the weld point, thereby maintaining low pressures at the weld point.

[0028] The first deflector may comprise an axially extending deflector wall located radially spaced from the weld point and configured to deflect gas entering the distal inlet opening axially into the nozzle before it reaches the weld point. As the incoming gas travels along the horizontal surface of the workpiece and into the distal inlet opening, the incoming gas may encounter and strike the first deflector wall which deflects the gas axially into the nozzle before it can continue traveling to the weld point.

[0029] The axially extending deflector wall of the first deflector may comprise an annular wall which may encircle or surround the weld point. In particular, the first deflector may comprise an annular wall centred on the weld point. In effect, the first deflector annular wall may define the laser beam exit opening. In this way, any incoming gas travelling radially towards the centre of the distal inlet opening, and thus towards the weld point, may encounter the first deflector annular wall and be deflected axially into the nozzle before it reaches the weld point. In effect, all or the majority or at least a large proportion of the gas travelling towards the weld point may be deflected axially into the nozzle by the first deflector before the incoming gas can collide at the weld point. This ensures relatively low pressures are maintained at the weld point.

[0030] The distal inlet opening may comprise a second deflector configured to deflect gas and / or gas jets entering the distal inlet opening axially into the nozzle before the gas reaches the weld point. The second deflector may comprise an axially extending deflector wall located radially spaced from the weld point and radially spaced from the first deflector. The second deflector may be configured to deflect gas entering the distal inlet opening axially into the nozzle before it reaches the weld point. The axially extending deflector wall of the second deflector may comprise an annular wall which may encircle or surround the weld point. In particular, the second deflector may comprise an annular wall centred on the weld point and co-axial with the first deflector. The first deflector may encircle the second deflector. In effect, the second deflector annular wall may define the laser beam exit opening. In this way, any incoming gas travelling along the surface of the workpiece and radially towards the centre of the distal inlet opening, and thus towards the weld point, may encounter the first deflectorand be deflected axially into the nozzle. Any remaining gas travelling radially towards the weld point and not deflected by the first deflector may subsequently encounter the second deflector and be deflected axially into the nozzle before it reaches the weld point. Providing a first and second deflector may increase the likelihood of capturing the majority of the gas entering the distal inlet opening and deflecting it axially into the nozzle before it reaches the weld point.

[0031] The distal inlet opening may comprise an outwardly extending flange. The flange may extend radially (for example perpendicularly) from the distal inlet opening. In effect, the flange may extend perpendicularly to the central longitudinal axis of the nozzle. As described above, in use, the central longitudinal axis of the nozzle may be positioned substantially perpendicularly to the workpiece. In this way, the flange may extend substantially parallel to the surface of the workpiece when in use.

[0032] The flange may connect to the distal inlet opening with an inner curved wall. In particular, the flange may define a diverging flow path for gas entering the nozzle at the distal inlet opening. In effect, as incoming gas is suctioned up through the distal inlet opening, the gas may travel along the surface of the workpiece radially towards the centre of the distal inlet opening. In particular, the incoming gas may travel between the workpiece and the flange, these defining a relatively narrow flow path for the incoming gas. As the gas continues to travel along the workpiece, the gas travels along the flow path between the workpiece and the inner curved wall connecting the flange to the distal inlet opening, the inner curved wall defining a flow path that gradually increases in size (i.e. a diverging flow path) for the incoming gas compared to the relatively narrow flow path between the workpiece and the flange. The diverging flow path defined by the flange and the inner curved wall may cause the gas entering the nozzle at the distal inlet opening to increase in speed as it enters the distal inlet opening, thereby increasing the amount of gas that is deflected axially into the nozzle by the first and / or second deflectors before it reaches the weld point.

[0033] The first and / or second deflector may each comprise an outwardly extending lip. In particular, the lip may extend radially from the deflector wall of the first and / or second deflector. For example, the first deflector lip and / or the second deflector lip may extend perpendicularly to the central (longitudinal) axis of the nozzle. The lip may connect to the deflector wall via an inner curved wall such that the first deflector lip and / or the second deflector lip may define a diverging flow path for gas entering the distal inlet opening at the first deflector and / or at the second deflector. In effect, as incoming gas is suctioned up through the distal inlet opening, the gas travels along the surface of the workpiece radially towards the centre of the distal inlet opening. In particular, the incoming gas travels between the workpiece and the outer edge of the lip of the first deflector, these defining a relatively narrow flow path for the incoming gas. The gas may continue to travel along the flow path between the workpiece and the inner curved wall connecting the lip to the first deflector wall, the inner curved wall defining a flow path that gradually increases in size (i.e. a diverging flow path) for the incoming gas compared to the relatively narrow flow path at the outer edge of the lip. The diverging flow path defined by the lip may cause the gas entering the distal inlet opening to increase in speed. This increases the amount of gas that is suctioned through the distal inlet opening between the first deflector and the second deflector and thus deflected axially into the nozzle by the second deflector before it reaches the weld point. Any remaining gas not deflected axially into the nozzle by the second deflector may travelbetween the workpiece surface and the outer edge of the lip of the second deflector, these defining a relatively narrow flow path for the incoming gas. The gas may continue to travel along the flow path between the workpiece and the inner curved wall connecting the lip to the second deflector wall, the inner curved wall defining a flow path that gradually increases in size (i.e. a diverging flow path) for the incoming gas compared to the relatively narrow flow path at the outer edge of the lip. The diverging flow path defined by the lip may cause the gas entering the distal inlet opening to increase in speed. In particular, the gas may accelerate into the distal inlet opening at the perimeter edge of the laser beam exit opening before it reaches the weld point.

[0034] The first deflector lip may extend from the entire circumference of the first deflector wall and / or the second deflector lip may extend from the entire circumference of the second deflector wall. In effect, in embodiments where the first and / or second deflector comprise annular walls, the lip may extend from the rim (i.e. the distal rim) of the annular wall.

[0035] The first and / or second deflector lip may comprise a sharp outer edge. The sharp outer edge may be particularly effective at cutting through the incoming gas travelling along the workpiece, between the distal end of the nozzle and the workpiece surface. By cutting through the incoming gas in this way, an increased amount of gas can be deflected by the first and / or second deflectors.

[0036] In some embodiments, the nozzle may comprise a proximal inlet opening at the proximal end of the nozzle. The proximal inlet opening may be fluidly open or connected to ambient gas, thereby allowing ambient gas to enter the nozzle via the proximal inlet opening. In these embodiments, ambient gas may enter the nozzle from both the distal inlet opening (as described above) and the proximal inlet opening. The proximal inlet opening may be an opening aligned with the central axis (e.g. central longitudinal axis) of the nozzle. The proximal inlet opening may be the laser beam entry opening (excluding the glass window described above).

[0037] The nozzle may comprise a proximal end deflector that may be disposed generally towards the proximal end of the nozzle. The proximal end deflector may be configured to divert gas entering the proximal inlet opening away from the optical path of the laser beam. In particular, the proximal end deflector may be configured to divert gas away from the weld point.

[0038] The proximal end deflector may comprise a diverting member configured to divert gas entering the proximal inlet opening away from the optical path of the laser beam. The diverting member may extend radially from a longitudinal axis of the nozzle so as to divert gas away from the optical path of the laser beam. In particular, the diverting member may be configured to divert the gas radially outwards towards the walls of the nozzle.

[0039] The proximal end deflector may comprise an inner delivery conduit (e.g. a tubular conduit) extending axially within the nozzle from the proximal inlet opening. The inner delivery conduit may be co-axial with the central longitudinal axis of the nozzle. The diverting member may extend radially outward from the inner delivery conduit. In effect, the inner delivery conduit may be configured to receive gas from the proximal inlet opening and flow the received gas to the diverting member. The diverting member may extend from the circumference (e.g. theentire circumference) of the delivery conduit. This advantageously allows the diverting member to divert a larger amount of gas.

[0040] The diverting member may comprise a substantially conical concave shape. In particular, the diverting member may comprise an upwardly curved face for guiding the gas away from the distal end of the nozzle and thus the weld point. The diverting member may comprise an upwardly curved face with an upwards curve or angle of approximately 30 to 60 degrees from the vertical axis, for example an upwards curve or angle of approximately 45 degrees from the vertical axis. The diverting member may be in the form of a solid (i.e. unperforated) plate.

[0041] The delivery conduit may extend from the proximal inlet opening and may extend to approximately mid-way into the nozzle. Thus, the delivery conduit may be provided towards the proximal end of the nozzle. In this way, the diverting member may be provided towards the proximal end of the nozzle. This advantageously allows the diverting member to divert the gas away from the distal end of the nozzle before it reaches the weld point. The delivery conduit may extend to a downstream opening and may capture a large portion or the majority or all of the incoming gas from the proximal inlet opening. The inner delivery conduit may be coaxial with the optical path of the laser beam.

[0042] The proximal end deflector may comprise more than one diverting member, for example 2, 3, 4 or more diverting members extending radially so as to divert gas away from the optical path of the laser beam and the weld point. The number of diverting members may depend on the amount of gas that may be required to be diverted or the size of the nozzle. The diverting members may be axially spaced along the delivery conduit, for example, equally axially spaced along the delivery conduit.

[0043] As described above, each diverting member may comprise a substantially conical concave shape with the delivery conduit defining a top opening (for example a circular top opening) in each diverting member. The top opening of the diverting member(s), for example of the top diverting member or of each diverting member, may be horizontal (i.e. lie in line with a plane perpendicular to the longitudinal axis of the nozzle). In some embodiments, the top opening of the diverting member(s), for example of the top diverting member or of each diverting member, may be angled relative to the horizontal plane of the nozzle. By providing a top opening that is angled, the gas flowing through the conduit may tend towards one side of the top opening thereby encouraging the flow of gas to divert away from the central axis of the nozzle and thus from the optical path of the laser beam. This can further prevent the gas from being directed at the weld point. While there may be a natural propensity for the incoming gas to tend towards one side of the top opening of the diverting member(s), including angled or slanted top openings can further encourage this behaviour. In embodiments where the top opening(s) may be angled, the top opening(s) of the diverting member(s) may be elliptical rather than circular.

[0044] In some embodiments, the proximal end deflector may comprise a plurality of diverting members axially spaced along the delivery conduit. In other embodiments, the proximal end deflector may comprise a helically shaped diverting member which spirals down the delivery conduit. The proximal end deflector may comprise one or more helically shaped diverting members.The nozzle may comprise a rolling element for maintaining a predetermined distance between the distal end (i.e. the distal end face) of the nozzle and the workpiece and for allowing the nozzle (with the laser head) to roll along the workpiece during laser welding. In particular, the rolling element may be disposed at the base (i.e. at the distal end face) of the nozzle. In use, the rolling element may be brought into contact with the workpiece, bringing the distal end face of the nozzle or a nozzle tip in close proximity to the workpiece without the nozzle tip contacting the workpiece. The rolling element may be used to adjust or maintain the distance between the nozzle tip and the workpiece. The rolling element may maintain a gap of between 0.5mm-3mm between the nozzle tip and the workpiece. For example, the rolling element may maintain a gap of between 0.5mm-1.5mm between the nozzle tip and the workpiece. In some examples, the rolling element may maintain a gap of 1mm between the nozzle tip and the workpiece. The nozzle may comprise multiple rolling elements at the base of the nozzle, for example 2, 3, 4, 4+ depending on the size of the nozzle. The rolling elements may be disposed symmetrically about the central axis of the nozzle or on opposite sides of the nozzle, i.e. on diametrically opposite sides of the distal inlet opening. The rolling element(s) may comprise a roller bearing(s), a wheel(s) or any other suitable rolling element.

[0045] The nozzle may be enclosed in a housing. The nozzle may define a chamber within the housing. The rolling element(s) may be disposed in the housing.

[0046] A distal end face of the nozzle may comprise a weld bead opening comprising an elongate groove extending radially from the central longitudinal axis of the nozzle to an outer edge or perimeter of the distal inlet opening. The groove may raise a portion of the distal end face of the nozzle. In particular, the groove may raise a portion of the flange and / or a portion of the outwardly extending lips of the first and / or second deflectors. In effect, the groove may be configured to raise a portion of the distal end face of the nozzle so as to provide space for the weld bead or weld pool as the nozzle is swept over the surface of the workpiece. The groove may have a width or radial span of approximately 2mm-10mm. For example, the groove may have a width or radial span of approximately 3mm-7mm. In some examples, the groove may have a width or radial span of approximately 5mm. The groove may have an axial height of approximately 1mm-5mm, for example the groove may have an axial height of approximately 3mm.

[0047] The weld bead opening may extend radially in one direction from the central longitudinal axis of the nozzle or the central axis of the distal inlet opening to the outer edge or perimeter of the distal inlet opening. The nozzle (with the laser head) may be swept along the workpiece with the groove aligned with the direction of travel of the nozzle and faced away from the direction of travel of the nozzle. In this way, a weld line can be formed on the workpiece without the nozzle tip disturbing the newly formed weld.

[0048] The weld bead opening may extend radially in opposite directions from the central longitudinal axis of the nozzle or the central axis of the distal inlet opening to the outer edge or perimeter of the distal inlet opening. In effect, the weld bead opening may extend transversely across the distal end face of the nozzle and may extend transversely through the central axis of the nozzle or the central axis of the distal inlet opening. The nozzle (with the laser head) may be swept along the workpiece with the groove aligned with the directionof travel of the nozzle. The weld bead opening extending in opposite directions allows the groove to be faced in the same direction or away from the direction of travel of the nozzle without the nozzle tip disturbing the newly formed weld.

[0049] The distal end face of the nozzle may comprise a C-seal which may surround the distal inlet opening and configured to control the amount of gas entering the nozzle at the distal inlet opening. In particular, the C-seal may reduce or minimise the gas entering the nozzle at the distal inlet opening. The C-seal may be configured to open when not under pressure of incoming gas and may be configured to be closed when under pressure of incoming gas being suctioned into the nozzle at the distal inlet opening. By providing a C-seal to minimise and control the amount of gas entering the distal inlet opening, this provides a passive way of sealing the distal end face of the nozzle. In effect, the C-seal automatically closes as gas is being suctioned into the nozzle so as to minimise the amount of gas entering the distal inlet opening. In particular, no other external force or mechanism is required to close the C-seal when gas is being suctioned into the nozzle.

[0050] The nozzle may comprise the same material as the workpiece being welded. For example, the nozzle may comprise a metal material. The nozzle may comprise steel, aluminium, copper, titanium, brass, iron material, plastics etc.

[0051] The nozzle may be formed using any suitable manufacturing method, including for example additive manufacturing or a casting process.

[0052] According to another aspect, there is provided a laser welding system for welding a workpiece by using a laser, comprising:

[0053] a laser beam generator for generating a laser beam directed at a weld point on the workpiece,

[0054] a laser head for directing the laser beam to the weld point,

[0055] a nozzle as described above,

[0056] the nozzle being optically connectable with the laser head so as to receive the laser beam from the laser head.

[0057] The outlet port(s) of the nozzle is / are fluidly connectable to a vacuum pump for suctioning gas into the nozzle from the distal inlet opening and out from the nozzle via the outlet port(s). The laser welding system may comprise a vacuum pump connected (i.e. in fluid communication) to the outlet port(s) for suctioning gas into the nozzle from the distal inlet opening and out from the nozzle via the outlet port(s).

[0058] The laser head may comprise a focusing means for focusing the laser beam at the weld point.

[0059] The nozzle described above is able to significantly reduce the pressure within the nozzle and therefore at the weld point, thereby resulting in a high quality weld at the weld point. In effect, the nozzle allows for welding with low pressure locally around the weld point. This advantageously allows for laser welding in any given environment, including in atmospheric conditions or conditions with high environmental pressure, and for a high quality weld to be produced due to the localised low pressure provided at the weld point by the nozzle. Inparticular, the nozzle provides localised low pressure at the weld point thereby removing the need for laser welding in a vacuum chamber in order to achieve a high quality weld.

[0060] However, it will be appreciated that, while the nozzle allows for laser welding outside a vacuum chamber and still achieving a high quality weld, the nozzle may also be used for laser welding inside a vacuum chamber, where the ambient pressure may already be relatively low, and where the nozzle provides even further lowering of the pressure locally at the weld point.

[0061] Other aspect will also become apparent upon review of the present disclosure, in particular upon review of the Brief Description of the Drawings, Detailed Description and Claims sections.

[0062] BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Examples of the disclosure will now be described, by way of example only, with reference to the accompanying drawings in which:

[0064] Figure 1 shows the components of a conventional laser welding apparatus;

[0065] Figure 2 shows a perspective view of a nozzle assembled with a laser head for use with a laser beam welding machine according to an embodiment of the invention;

[0066] Figure 3 shows a cross section view of the nozzle;

[0067] Figure 4 shows a top perspective view of the nozzle;

[0068] Figure 5 shows a detailed view of a distal end of the nozzle;

[0069] Figures 6 shows a cross section detailed view of the distal end of the nozzle with arrows showing the direction of flow of gas into and within the nozzle;

[0070] Figure 7 shows a cross section detailed view of a portion of the distal end of the nozzle; Figure 8 shows a cross section view of the nozzle with arrows showing the direction of flow of gas entering and travelling through the nozzle;

[0071] Figure 9 shows a cross section view of another embodiment of nozzle according to the invention;

[0072] Figures 10 shows a top perspective view of the nozzle of Figure 9;

[0073] Figure 11 shows a cross section view of the nozzle of Figure 9 with arrows showing the direction of flow of gas into and travelling through the nozzle;

[0074] Figures 12 and 13 show other embodiments of the distal end of the nozzle;

[0075] Figures 14 and 15 show exploded views of the components of the nozzle

[0076] Figure 16 shows a cross section view of the nozzle of Figure 9;

[0077] Figure 17a and 17b show a simulation of the pressures generated inside the nozzle of Figure 9;

[0078] Figures 18a and 18b show a simulation of the pressures generated inside the nozzle of Figure 12;

[0079] Figures 19a and 19b show a simulation of the pressures generated inside the nozzle of Figure 13;

[0080] Figures 20-22 show example dimensions for the nozzle according to an embodiment; and Figures 23-25 show example dimensions for the nozzle according to an embodiment of the invention.

[0081] While the disclosure is susceptible to various modifications and alternative forms, specific example approaches are shown by way of example in the drawings and are hereindescribed in detail. It should be understood however that the drawings and detailed description attached hereto are not intended to limit the disclosure to the particular form disclosed but rather the disclosure is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the claimed invention.

[0082] As used in this specification, the words “comprises”, “comprising”, and similar words, are not to be interpreted in an exclusive or exhaustive sense. In other words, they are intended to mean “including, but not limited to”.

[0083] It will be recognised that the features of the above-described examples of the disclosure can conveniently and interchangeably be used in any suitable combination. It will also be recognised that the invention covers not only individual embodiments but also combinations of the embodiments that have been discussed herein.

[0084] DETAILED DESCRIPTION

[0085] The present invention generally relates to a nozzle for attachment to a laser welding apparatus where a high-energy laser beam is used to irradiate a workpiece to melt a portion of the workpiece. The welding process involves focusing the laser beam onto the workpiece, where the laser beam melts and / or vaporises the material at the point of impact of the laser beam on the workpiece, creating a weld pool.

[0086] Figure 1 shows the components of a conventional laser welding apparatus used in laser welding. A laser beam generator generates a laser beam 10 which passes through a laser head 12 before irradiating the workpiece 14. The laser head usually includes a laser focusing means, such as a collimator or an optical lens (not shown), for focusing the laser beam at a weld point 16 on the workpiece. The laser beam melts and vaporises the material at the weld point 16 creating the weld pool. As the weld pool cools and solidifies, a weld is created. In figure 1, the laser welding apparatus is used to join two plates A, B together. The end portions of the two plates are butted against each other and the laser beam 10 is swept over the butted portion by moving the welding apparatus relative to the plates along the butted portion. The laser melts the material at the joint between the two plates and as material solidifies, the two plates are joined together.

[0087] The conditions at the weld point 16 need to be controlled in order to achieve a high quality weld. In particular, high pressure at the weld point 16 needs to be avoided to prevent material thinning at the weld point 16 as the weld is being created. Furthermore, the amount of atmospheric and / or ambient air / gases entering the weld area (i.e. the area around the weld point) are preferably reduced so as to minimise the gases contaminating the weld pool and thus the resulting weld.

[0088] Figure 2 shows a perspective view of a nozzle 20 according to the invention, mounted to the laser head 19 for receiving the laser beam; and Figure 3 shows a cross sectional view of the nozzle 20 mounted to the laser head 19. Looking at Figure 3, the proximal end 32 of the nozzle 20 comprises means for mounting the nozzle 20 to the laser head 19 and the distal end 36 of the nozzle 20 comprises a distal inlet opening 24. The proximal end 32 of the nozzle 20 comprises a laser beam entry opening 30 for receiving the laser beam and thedistal end 36 of the nozzle comprises a laser beam exit opening 34 for delivering the laser beam onto the workpiece 25.

[0089] As shown by Figure 3, the nozzle 20 is coaxially mounted to the laser head 19 such that a central longitudinal axis 21 of the nozzle 20 is aligned with a central axis of the laser head 19. The laser beam is thus configured to travel from the laser beam entry opening 30 through the laser beam exit opening 34 and to the weld point 50 on the workpiece 25 along an optical path 38 extending through the central axis 21 of the nozzle 20. The laser beam exit opening 34 and the distal inlet opening 24 are also coaxial with the central axis 21 of the nozzle. In use, the laser head 19 and the nozzle 20 are positioned such that the central longitudinal axis 21 of the nozzle 20 is substantially perpendicular to the workpiece 25. The nozzle 20 is moved along the surface of the workpiece (together with the laser head 19) so as to form the weld on the workpiece.

[0090] The nozzle walls define a chamber 26 with the distal inlet opening 24 defining an inlet for ambient gas to enter into the chamber 26. The nozzle 20 comprises four outlet ports 54a, 54b, 54c, 54d fluidly connected to the nozzle and fluidly connectable to a vacuum pump provided downstream from the ports 54a, 54b, 54c, 54d which suctions the ambient gas out from the nozzle 20 via the ports 54a, 54b, 54c, 54d. Suction of the gas out from the nozzle significantly reduces the pressure within the nozzle to the order of 5-10 kPa, in effect creating a vacuum within the nozzle. The low pressure within the nozzle 20 and thus at the weld point 50 allows for a high quality weld to be created at the weld point 50.

[0091] Suctioning the gas out of the nozzle 20 also ensures that any gas molecules surrounding the weld area are suctioned out of the nozzle 20 through the outlet ports 54a, 54b, 54c, 54d, thereby reducing the amount of contamination of the weld pool by the gas molecules. The outlet ports 54a, 54b, 54c, 54d are provided towards the proximal end of the nozzle 20 and are angled generally upwards (i.e. towards the proximal end of the nozzle) so as to capture the majority of the gas entering the nozzle via the distal inlet opening 24 and deflected upwards into the nozzle (as described further below). In this embodiment, the outlet ports 54a, 54b, 54c, 54d are circular in cross section and are angled at approximately 45 degrees from the vertical central axis of the nozzle 20. The four outlet ports 54a, 54b, 54c, 54d are radially spaced from the central axis 21 of the nozzle 20 and disposed symmetrically about the central axis 21 of the nozzle 20 (see Figure 4) so as to better capture the spread of gas within the nozzle 20.

[0092] The laser beam entry opening 30 comprises a glass window which allows the laser beam to pass through the nozzle 20 from the laser head while sealing off the proximal end of the nozzle to the ambient gas surrounding the nozzle. By sealing the proximal end of the nozzle and only allowing ambient gas to enter from the distal inlet opening 24, a more effective vacuum within the nozzle is achieved when suctioning gas out of the nozzle.

[0093] As ambient gas enters the nozzle 20 from the distal inlet opening 24 and is suctioned out from the outlet ports 54a, 54b, 54c, 54d, the vacuum created within the nozzle 20 causes ambient gas to jet along the surface of the workpiece 25 and converge at the weld point 50 before entering the nozzle 20 at the distal inlet opening 24. This results in local elevated pressures at the weld point 50.Furthermore, as mentioned above, the vacuum pump suctioning the gas out of the nozzle 20 lowers the pressure within the nozzle 20, in some embodiments to the order of 5-10 kPa. The pressure outside the nozzle 20 will often be higher, for example it may be at ambient atmospheric pressure of approximately 100 kPa. This difference in pressure between the inside of the nozzle 20 and outside of the nozzle 20 corresponds to a pressure ratio well above a critical pressure ratio, which is 1.89 for air. This results in the flow of gas entering the nozzle 20 at the distal inlet opening 24 to reach supersonic speed. In particular, in embodiments where the pressure inside the nozzle is of the order of 5-10 kPa and the pressure outside the nozzle is approximately 100 kPa (atmospheric pressure), the pressure ratio is approximately 10, resulting in the flow of gas entering the nozzle 20 at the distal inlet opening 24 to reach supersonic speed. The supersonic jets of incoming gas travel along the surface of the workpiece 25, between the workpiece 25 and the nozzle 20, and towards the weld point 50, eventually meeting and colliding at the weld point 50.

[0094] To prevent these jets of incoming supersonic gas entering the nozzle from meeting and colliding at the weld point 50 and resulting in high pressure at the weld point 50, the distal inlet opening 24 comprises first 60 and second 62 deflectors which deflect the incoming gas axially into the nozzle 20 before the gas reaches the weld point 50, thereby keeping a low pressure at the weld point 50.

[0095] Turning to Figure 4, this shows the deflectors 60, 62 within the nozzle and Figure 5 shows a bottom perspective detailed view of the nozzle 20 illustrating the deflectors 60, 62. As shown by these figures, the first deflector 60 comprises an annular deflector wall extending axially into the nozzle and configured to deflect gas entering from the distal inlet opening 24 axially into the nozzle before it reaches the weld point 50. The second deflector 62 similarly comprises an annular deflector wall extending axially into the nozzle and configured to deflect gas entering from the distal inlet opening 24 axially into the nozzle before it reaches the weld point 50.

[0096] The first deflector 60 encircles the second deflector 62 such that the distal inlet opening 24 comprises an outer annular opening 64, defined by the nozzle walls and the first deflector 60; the outer annular opening 64 surrounding an inner annular opening 66 defined by the first deflector 60 and the second deflector 62; the inner annular opening 66 in turn surrounding the laser beam exit opening 34 (and thus the weld point 50) at the axial centre of the nozzle 20. The first 60 and second 62 deflectors are concentric with the central axis 21 of the nozzle 20. In effect, the annular walls of the second deflector 62 define the laser beam exit opening 34. The skilled person will appreciate that in embodiments comprising only the first deflector 60, the annular walls of the first deflector 60 will define the laser beam exit opening 34.

[0097] The deflector walls extend axially into the nozzle 20 such that as gas travels along the workpiece 25 towards the weld point 50, at least a portion of the incoming gas is deflected by the first deflector 60 axially into the nozzle and through the outer annular opening 64, preventing it from reaching the weld point 50. Any remaining gas travelling along the surface of the workpiece towards the weld point 50 is deflected by the second deflector 62 axially into the nozzle and through the inner annular opening 66, preventing it from reaching the weld point 50. In this way, all of the gas entering the nozzle, or at least the majority of the gas entering the nozzle 20 at the distal inlet opening 24 is axially deflected into the nozzlebefore it reaches the weld point 50 such that the amount of gas reaching and colliding at the weld point 50 is either eliminated or significantly reduced. This allows the pressures at the weld point 50 to be kept at a minimum, thereby ensuring a high quality weld.

[0098] Looking at Figure 5, the distal inlet opening 24 comprises an outwardly extending annular flange 56 that extends radially from the distal inlet opening 24 and substantially perpendicularly to the central axis 21 of the nozzle 20, such that in use the flange 56 extends generally parallel to the surface of the workpiece 25. The flange 56 connects to the distal inlet opening 24 with an inner curved wall 58 (shown in Figure 6) such that the flange 56 defines a diverging flow path for gas entering the distal inlet opening 24.

[0099] Figures 6, 7 and 8 show cross-sectional views of the nozzle 20 with arrows showing the direction of flow of the gas entering and moving through the nozzle 20. Looking in particular at Figures 6 and 7, these show detailed views of the distal end of the nozzle 20. As described above, the distal inlet opening 24 comprises an outwardly extending flange 56 that connects to the distal inlet opening 24 with an inner curved wall 58. The flange 56 connects to the nozzle walls with the inner curved wall 58 so as to define a diverging flow path for gas entering the distal inlet opening 24. In particular, a first portion of the flange 56 disposed substantially perpendicularly to the vertical central axis 21 of the nozzle 20 (and in use is disposed substantially parallel to the surface of the workpiece 25) defines a relatively narrow flow path for gas entering the nozzle between the flange and the workpiece 25. As the gas continues to travel along the workpiece 25 toward the weld point 50, the inner curved wall 58 connecting the flange 56 to the nozzle walls defines a diverging flow path for the incoming gas as it travels between the workpiece surface and inner curved wall 58. This diverging flow path causes the gas entering the nozzle to increase in speed, thereby increasing the amount of gas that is deflected axially into the nozzle by the deflectors 60, 62 before it reaches the weld point 50. In particular, once the gas enters the nozzle 20, the gas accelerates into the outer annular opening 64 and is deflected by the first deflector 60 axially into the nozzle. This maximises the amount of gas that is suctioned through the outer annular opening 64 and deflected axially into the nozzle by the first deflector 60 before it reaches the weld point 50. Any remaining air travelling along the surface of the workpiece (i.e. not deflected axially into the nozzle 20 by the first deflector 60) is diverted by the second deflector 62.

[0100] The first deflector 60 comprises an outwardly extending lip 70 that extends radially from the deflector wall and extends from the entire circumference of the first deflector wall. The lip 70 connects to the deflector wall via an inner curved wall which defines a diverging flow path for the gas travelling along the workpiece and into the distal inlet opening 24. In particular, as gas travels along the workpiece and into the distal inlet opening 24, the incoming gas will travel between the workpiece and the outer edge of the lip 70 defining a relatively narrow flow path. The flow of gas will continue travelling through the flow path defined by the workpiece and the inner curved wall connecting the lip 70 to the deflector wall of the first deflector 60. The diverging flow path defined by the lip 70 and the inner curved wall connecting the lip 70 to the deflector 60, as the gas travels from the outer edge of the lip towards the centre of the distal inlet opening 24 causes the gas travelling between the lip 70 and the workpiece surface to increase in speed and accelerate into the inner annular opening 66. This increases the amount of gas that is suctioned through the inner annular opening 66 and deflected axially into the nozzle by the second deflector 62 before it reaches the weld point. This maximises the amount of gas that is deflected by the second deflector62 before it reaches the weld point 50. Furthermore, with the flow of gas entering the nozzle 20 reaching supersonic speed, the flow of gas entering the outer annular opening 64 and the inner annular opening 66 undergoes isentropic expansion in the direction away from the distal end 36 of the nozzle 20 and towards the proximal end 32 of the nozzle 20. This flow expansion causes the flow to impinge against the deflectors 60, 62 and deflect axially into the nozzle 20 before reaching the weld point 50.

[0101] The second deflector 62 comprises an outwardly extending lip 72 that extends radially from the deflector wall and extends from the entire circumference of the second deflector wall. The lip 72 connects to the deflector wall via an inner curved wall such that the inner curved wall of the lip defines a diverging flow path for the gas travelling along the workpiece and into the distal inlet opening 24. In particular, the incoming gas travels between the workpiece and the outer edge of the lip 72 defining a relatively narrow flow path. The flow of gas continues travelling through the flow path defined by the workpiece and the inner curved wall connecting the lip 72 to the deflector wall of the second deflector 62. The diverging flow path defined by the lip 72 and the inner curved wall connecting the lip 72 to the deflector 62 causes the gas travelling between the lip 72 and the workpiece surface to increase in speed and accelerate into the distal inlet opening 24 at the perimeter edge of the laser beam exit opening 34. This increases the amount of gas that is suctioned axially into the nozzle at the perimeter edge of the laser beam exit opening 34 before it reaches the weld point 50.

[0102] The lip 70 of the first deflector 60 and / or the lip 72 of the second deflector 62 each comprise a sharp outer edge which is configured to more effectively cut through the incoming gas travelling along the workpiece surface, thereby increasing the amount of gas that is deflected by the deflectors 60, 62.

[0103] The flange 56 together with the deflector lips 70, 72 each accelerate the flow of gas entering the nozzle at the distal inlet opening 24, and help to maximise the amount of gas that is deflected by the deflectors 60, 62 before the gas reaches the weld point 50. This ensures that minimal gas is allowed to reach the weld point 50, thereby keeping the pressures at the weld point 50 low.

[0104] As shown by Figure 8, the gas entering the nozzle 20 at the distal inlet opening 24 is deflected by the deflectors 60, 62 axially into the nozzle and is suctioned out through the outlet ports by the vacuum pump. The gas entering the nozzle at the distal inlet opening 24 is deflected by the deflectors 60, 62 such that the gas travels along the periphery of the chamber 26 of the nozzle 20. As described above, the outlet ports 54a, 54b, 54c, 54d are disposed radially spaced from the central axis of the nozzle and symmetrically about the central axis 21 of the nozzle 20 so as to most effectively capture the spread of gas deflected into the nozzle 20.

[0105] Turning back to Figures 2 and 3, the nozzle 20 is encased in the housing 22. An upper portion 74 of the housing conforms to the shape of the outlet ports 54a, 54b, 54c, 54d at the proximal end 32 of the nozzle 20 and a lower portion of the housing 76 is cylindrically shaped and houses two cylindrical roller bearings 78a, 78b disposed at the base of the nozzle (i.e. the distal end face) and disposed on opposite sides (i.e. transversely across) of the nozzle 20 for adjusting or maintaining a predetermined distance or a gap between the distal end face or tip of the nozzle 20 and the workpiece 25. In use, the nozzle 20 with thenozzle housing 22 are brought into close contact with the workpiece 25 such that the roller bearings 78a, 78b contact the workpiece 25 surface, maintaining a predetermined gap between the nozzle tip and the workpiece 25 surface and enabling the nozzle to roll freely over the workpiece surface. The roller bearings 78a, 78b help to provide a minimum gap between the distal end face or tip of the nozzle 20 and the workpiece 25 so as to minimise any leakage of gas from the distal inlet opening and to achieve the most effective vacuum within the nozzle while still allowing the nozzle tip to move freely over the workpiece. As the gas is suctioned out of the nozzle by the vacuum pump, the vacuum in the nozzle pulls the nozzle towards the workpiece 25. The roller bearings 78a, 78b help to maintain a vertical separation between the end face or tip of the nozzle 20 and the workpiece 25 as gas is being suctioned out of the nozzle, enabling the nozzle to roll freely over the workpiece surface as required. In this embodiment, the roller bearings 78a, 78b maintain a gap of approximately 1mm between the nozzle tip and the workpiece 25 surface. The roller bearings 78a, 78b are disposed with their central axes running through and disposed perpendicularly to the central longitudinal axis 21 of the nozzle 20. The roller bearings 78a, 78b also ensure a low friction contact between the nozzle 20 and the housing 22 against the workpiece 25.

[0106] Turning to Figure 4, the nozzle 20 comprises a diverging-converging shape where the (transverse) cross sectional area of the nozzle 20 increases from the proximal end 32 to its widest point approximately a third of the axial length of the nozzle 20, before decreasing to its narrowest point at the distal inlet opening 24 of the nozzle 20. In particular, the nozzle chamber walls taper outwardly from the proximal end to the nozzle’s widest point immediately below (or distal) of the outlet ports 54a, 54b, 54c, 54d before tapering inwardly to the distal inlet opening 24.

[0107] As mentioned above, the embodiment of Figures 2-8 comprises a glass window 31 (best shown in Figure 8) at the laser beam entry opening 30 so as to seal off the proximal end of the nozzle to the ambient gas surrounding the nozzle 20. Thus, the only ingress point for ambient gas into the nozzle 20 in these embodiments is via the distal inlet opening 24.

[0108] Figures 9-11 show another embodiment of nozzle where the proximal end 32 of the nozzle is fluidly open to the ambient gas. This may be achieved by comprising a proximal inlet opening that is fluidly open to ambient gas, thereby allowing ambient gas to enter the nozzle via the proximal inlet opening. The proximal end 32 of the nozzle may be left fluidly open to ambient gas so as to allow any potential fumes emitted by the weld during formation of the weld pool to exit the nozzle. This helps to protect the laser aperture and / or the laser generator from potential damage by the weld fumes. In the embodiment of Figures 9-11, the proximal inlet opening is provided by the laser beam entry opening 30 being open to ambient gas by excluding the glass window (described above in relation to Figures 2-8) for sealing the laser beam entry opening 30. In this way, ambient gas can enter the nozzle via the laser beam entry opening 30 as well as the distal inlet opening 24. The skilled person will appreciate that the proximal inlet opening may be provided by any other suitable means, e.g. an opening at the proximal end of the nozzle separate from the laser beam entry opening or an aperture or opening in the window 31 of the laser beam entry opening 30.

[0109] In embodiments comprising a proximal inlet opening, where the proximal end 32 of the nozzle is fluidly open to ambient gas, gas will rush into the nozzle 20 via the proximal inletopening due to the suctioning by the vacuum pump and the vacuum created within the nozzle 20. In particular, where the laser beam entry opening 30 comprises an opening fluidly open to ambient gas, the gas will rush into the nozzle along the central longitudinal axis 21 of the nozzle 20 and towards the weld point 50. This can cause increased pressures at the weld point 50. To prevent the gas entering the proximal inlet opening from reaching the weld point 50, the nozzle 20 comprises a proximal end deflector 55 configured to deflect gas entering the proximal inlet opening away from the weld point 50.

[0110] Figure 9 shows a cross sectional view of the nozzle 20 with the proximal end deflector 55 and Figure 10 shows a top perspective view of the nozzle 20 including the internal proximal end deflector 55. As shown by Figure 9, the proximal end deflector 55 comprises a delivery conduit 40 that extends axially along the central longitudinal axis 21 of the nozzle 20 and thus in line with the stream of gas entering from the laser beam entry opening 30 at the proximal end. The delivery conduit 40 extends from the laser beam entry opening 30 to approximately mid-way into the nozzle chamber 26 to a downstream opening 39. As shown in Figure 9, the delivery conduit 40 is generally tubular so as to provide a conduit or open passage for the stream of gas entering from the laser beam entry opening 30 as well as a passage for the laser beam to pass through the nozzle 20. As described above, the optical path of the laser beam is configured to travel along the central longitudinal axis 21 of the nozzle 20. The delivery conduit 40 is co-axial or concentric with the central longitudinal axis 21 of the nozzle 20 so as to provide the open passage for the laser beam to pass through the nozzle 20 to the weld point 50.

[0111] The proximal end deflector 55 comprises a plurality of diverting members 42, 44, 46 extending radially outwards from the delivery conduit 40 so as to divert the incoming gas radially outwards from the central axis 21 of the nozzle 20. In effect, the delivery conduit 40 is configured to receive the gas from the laser beam entry opening 30 and flow the incoming received gas to the diverting members 42, 44, 46. The diverting members 42, 44, 46 extend from the entire circumference of the delivery conduit 40 and each diverting member 42, 44, 46 comprises a generally conical concave shape with an upwardly curved concave deflecting face (best shown in Figure 10) configured to direct the ambient gas away from the distal end of the nozzle 20 and thus the weld point 50. Figures 10 and 11 have the delivery conduit 40 omitted to better illustrate the diverting members 42, 44, 46.

[0112] The diverting members 42, 44, 46 comprise a radial length (from the central axis 21 of the nozzle 20 to a distal end of the diverting members 42, 44, 46) of approximately 20-25mm. In particular, the radial length of the diverting members 42, 44, 46 is less than the radius of the nozzle chamber 26 such that a gap between the diverting members 42, 44, 46 (i.e. the outer edge of the diverting members) and the chamber 26 walls is provided for allowing the gas entering from the distal inlet opening 24 to travel up to the outlet ports 54a, 54b, 54c, 54d. The nozzle 20 comprises three diverting members 42, 44, 46 extending radially outwards from the delivery conduit 40. In this embodiment, the diverting members 42, 44, 46 are equally axially spaced along the delivery conduit 40. In other embodiments, fewer than three or more than three diverting members 42, 44, 46 may be provided depending on the size of the nozzle 20 or the amount (i.e. volume) of gas required to be diverted. In some embodiments, the diverting members 42, 44, 46 may not be equally axially spaced along thedelivery conduit 40, for example they may be spaced at different axial intervals depending on the flow dynamics required by the nozzle.

[0113] The delivery conduit 40 with the diverting members 42, 44, 46 are generally provided towards the proximal end 32 of the nozzle 20 so as to capture the incoming gas from the proximal inlet opening (in this embodiment the laser beam entry opening 30) of the nozzle 20 and divert the gas away from the distal end 36 before it reaches the weld area and the weld point 50. This advantageously ensures that the majority of the gas is diverted away from the weld point 50 such that the pressure at the weld point 50 is kept to a minimum.

[0114] The distal end of the delivery conduit 40 comprises an annular splash plate 52 extending radially outwards from the delivery conduit 40 with a circular opening at the centre of the plate for allowing the laser beam to pass through the splash plate. The splash plate 52 diverts any remaining ambient gas away from the central axis 21 of the nozzle 20 and thus the optical path 38 of the laser beam. The splash plate 52 also aids in preventing any splash-back or splatter from the weld pool from hitting and potentially damaging the laser generator tool. In this embodiment, the splash plate 52 is approximately 10-15mm in diameter. For example, the splash plate is 14.5mm in diameter.

[0115] In some welding processes, a shield or protection gas can be introduced into the nozzle 20 to further aid in preventing any smoke, fumes or debris produced by the weld pool emigrating up into the laser generator tool. Such shield / protection gas is often introduced from a proximal end of the nozzle 20 towards the weld area. The proximal end deflector 55 described above can help to prevent any shield / protection gas introduced at the proximal end of the nozzle 20 from impinging onto the weld point 50 thereby keeping the pressures at the weld point 50 at a minimum.

[0116] It will be appreciated that in the embodiments of Figures 2-8 where the proximal end of the nozzle 20 is sealed off from ambient gas entering the nozzle 20, the proximal end deflector 55 may not be necessary. However, the skilled person will appreciate that a window sealing the laser beam entry opening 30 may experience some leakage where ambient gas may still enter into the nozzle from the laser beam entry opening 30 despite the presence of the window. In such circumstances, providing a nozzle with the proximal end deflector 55 may still be suitable even if the proximal end of the nozzle is not deliberately fluidly open to the ambient gas.

[0117] Figure 11 shows a cross-sectional view of the nozzle 20 comprising the proximal end deflector 55 with arrows showing the direction of flow of the gas through the nozzle 20. The arrows show the direction of flow of the gas entering the proximal inlet opening (in this embodiment the laser beam entry opening 30) and deflected by the proximal end deflector 55. The gas enters through the laser beam entry opening 30 and into the delivery conduit 40. As the gas travels down the delivery conduit 40, the delivery conduit 40 flows the gas to the diverting members 42, 44, 46. In particular, as the gas travels down the delivery conduit 40, at least a portion of the gas is diverted to each diverting member 42, 44, 46. The diverting members 42, 44, 46 divert the gas radially outwards from the central axis 21 of the nozzle 20. In effect, the diverting members 42, 44, 46 provide a guide surface which guides the incoming gas away from the central axis 21 of the nozzle 20 and towards the periphery of the nozzle 20. The upwardly curved diverting members 42, 44, 46 direct the gas away fromthe distal end 36 of the nozzle 20 and towards the outlet ports 54a, 54b, 54c, 54d. In particular, the diverting members 42, 44, 46 divert the gas away from the weld point 50 so as to minimise the pressure at the weld point 50.

[0118] The proximal end deflector 55 works in conjunction with the deflectors 60, 62 at the distal inlet opening 24 of the nozzle such that any gas entering the nozzle is deflected away from the central axis of the nozzle, in particular away from the weld point 50. The gap between the diverting members 42, 44, 46 and the nozzle chamber walls provides space for passage of the gas entering from the distal inlet opening 24.

[0119] Figure 12 shows an embodiment of nozzle 20 comprising a weld bead opening 80 at the distal end face of the nozzle 20. The weld bead opening 80 comprises a radially disposed elongate groove extending radially in one direction from the central axis 21 of the nozzle 20 to the outer perimeter of the distal inlet opening 24. In effect, the groove raises a portion of the distal end face of the nozzle 20. As shown by Figure 12, the groove raises a portion of the annular flange 56 and a portion of the distal faces of the outwardly extending lips 70, 72 of the first 60 and second 62 deflectors. In this embodiment, the weld bead opening 80 has a width or a radial span of 5mm and an axial height of 3mm. The weld bead opening 80 provides a space or gap between the distal end face of the nozzle 20 and the workpiece 25, to allow the weld to form during the welding process. Once the weld pool starts to form, the laser head 19 together with the nozzle 20 is swept along the workpiece 25 surface with the groove aligned with the direction of travel of the nozzle 20 and facing away from the direction of travel of the nozzle 20, such that the weld line can be formed on the workpiece 25 without the distal end face of the nozzle or the nozzle tip disturbing the newly formed weld.

[0120] Figure 13 shows another embodiment of nozzle 20 comprising a weld bead opening 82 at the distal end face of the nozzle 20. In this embodiment, the weld bead opening 82 comprises a radially disposed elongate groove extending radially in opposing directions from the central axis 21 of the nozzle 20 to the outer perimeter of the distal inlet opening 24. In effect, the groove extends transversely across the distal end face of the nozzle 20, through the central axis 21 of the nozzle. In this embodiment, the weld bead opening 82 has a width or radial span of 10mm and an axial height of 3mm. As described above, this (double sided) weld bead opening 82 provides the space or gap between the distal end face of the nozzle 20 and the workpiece 25 surface, to allow the weld pool to form. The laser head 19 together with the nozzle 20 is swept along the workpiece 25 with the groove aligned with the direction of travel of the nozzle 20. In this embodiment, the groove can be faced in the same direction or the opposite direction to the direction of travel of the nozzle 20, without the nozzle tip disturbing the newly formed weld. The weld bead opening 80, 82 can also be useful to allow the distal end face of the nozzle or the nozzle tip to travel over a workpiece 25 with a weld bead already present from a prior welding pass, a weld preparation line or a workpiece with an imperfect work piece edge match. The weld bead opening 80, 82 of Figures 12 or 13 may be provided in combination with any of the above described embodiments.

[0121] In some embodiments, the nozzle comprises a C-seal 83 (best shown in Figures 21 and 22). The C-seal 83 is provided at the distal end face of the nozzle and surrounding the distal inlet opening 24. In particular, the C-seal 83 is provided on the distal end face of the nozzle at the base of the flange 56. The C-seal may be provided in combination with any of the abovedescribed embodiments. In particular, the C-seal may be suitable for the embodiments of nozzle comprising the weld bead opening 80, 82 described above.

[0122] The C-seal 83 provides a seal between the distal end face of the nozzle (in particular the distal end face of the flange) and the workpiece, so as to reduce or minimise the gas entering the nozzle at the distal inlet opening 24. While the vacuum pump connected to the outlet ports and the vacuum created within the nozzle will suction ambient gas into the nozzle from the distal inlet opening 24, it is still desirable to minimise the amount of gas being suctioned into the nozzle so as to keep pressures at the weld point 50 to a minimum. By providing a C-seal 83 at the distal end face, the spring-back resilient characteristic of the C-shape construction of the seal provides a flexible seal to the distal end face of the nozzle. In particular, the seal is configured to be open when not under pressure of incoming gas. In effect, when no gas is being suctioned into the nozzle, the C-seal 83 is not required to seal the distal end face of the nozzle, thus the C-seal 83 can remain open. As gas is suctioned into the nozzle, the pressure of the incoming gas causes the C-seal 83 to close, thereby reducing or minimising the amount of gas entering the nozzle at the distal end. In effect, the built-in resilience of the C-seal 83 allows the seal to close when under pressure of incoming gas, thereby minimising the amount of gas entering the nozzle.

[0123] The C-seal 83 comprises a ring with open ends. In particular, the C-seal 83 comprises an opening across the circumference of the seal, the C-seal 83 being assembled with the nozzle such that the opening in the seal is aligned with the weld bead opening 80, 82 which provides a gap in the C-seal 83 for passage of the weld bead or the weld pool as the nozzle is being swept over the surface of the workpiece 25. In some embodiments, the C-seal opening may comprise a slit in the circumference of the seal that is pushed open by the weld bead as the slit passes over the solid weld bead. In other embodiments, the C-seal opening may be a gap in a ring-shaped C-seal. The C-seal 83 may be formed of commonly used materials for C-seals. The seal is preferably based on the same material as the material being welded so as to avoid contamination between the C-seal 83 and the workpiece 25. For example, a metal seal of the same metal as the metal material being welded may be provided. Alternative forms of seal may also be suitable for providing the seal between the distal end face of the nozzle and the workpiece 25, including, for example, inverted C-seals, O seals, E seals, II seals etc.

[0124] In the embodiments comprising the weld bead opening 80, 82, the nozzle 20 may comprise the roller bearings 78a, 78b described above. The gap provided by the roller bearings 78a, 78b between the nozzle tip and the workpiece 25 can be smaller in embodiments comprising the weld bead opening 80, 82 compared to embodiments not comprising the weld bead opening 80, 82, as the space needed to allow passage of the distal end face of the nozzle over the weld bead is provided by the weld bead opening 80, 82.

[0125] Turning back to Figures 14 and 15, these show exploded views of the various components of the nozzle 20. As shown by Figure 14, the nozzle 20 comprises a top component 90 which may provide the housing 22 described above and comprising the outlet ports 54a, 54b, 54c, 54d, the proximal end deflector 55 and the cylindrical lower portion 76 of the housing formed as a unitary structure. A roller bearing support frame 92 and the nozzle tip 94 are formed as separate components that are assembled with the top component 90. Thenozzle tip 94 is assembled into the roller bearing support frame 92 and these two components are then assembled into the top component 90. The roller bearing support frame 92 comprises an inner cylindrical wall joined to an outer cylindrical wall by an annular end wall from which the roller bearings 78a, 78b project through. The nozzle tip 94 comprises the outwardly extending flange 56 which is butted against an inside face of the annular end wall when they are assembled together. In some embodiments, a flat cylindrical shim 98 may be provided and assembled between the annular end wall and the nozzle tip flange 56 to adjust and control the gap between the nozzle tip 94 and the workpiece 25 surface.

[0126] By providing the nozzle tip 94 as a separate component, the nozzle tip 94 is advantageously readily removable from the remainder of the nozzle 20, without having to dis-assemble the remainder of the nozzle 20, for example for maintenance or exchange with another type of nozzle tip or a new nozzle tip.

[0127] In other embodiments, the outlet ports 54a, 54b, 54c, 54d, the nozzle 20 (including the proximal end deflector 55 together with the diverting members 42, 44, 46) and the nozzle tip are uniformly formed as a single piece.

[0128] Turning now to Figure 16, this shows the proximal end deflector 55 can be designed with a suitable axial length, depending on the requirements of the nozzle. In particular, the proximal end deflector 55 can be designed such that the distal end of the delivery conduit 40 can be shorter or longer (in the axial direction) by approximately + / -2mm to 5mm (for example + / -3mm to 4mm), depending for example on the size of the nozzle, the amount of gas required to be deflected by the proximal end deflector 55 or the fluid flow dynamics required by the proximal end deflector 55. For example, the proximal end deflector 55 is designed such that the distal end of the delivery conduit 40 can be an additional 3.75mm away from the workpiece 25 or an additional 3.75mm closer to the workpiece 25, as required. In some embodiments, the distal end of the delivery conduit 40 must be at least 3mm away (i.e. axially above) from the workpiece 25.

[0129] Figures 17a and 17b show a simulation of the pressures generated within the nozzle 20 according to the embodiment of Figures 9-11 with the proximal end of the nozzle fluidly open to the ambient gas at the laser beam entry opening 30. Figures 17a shows a cross-section view of the nozzle with the pressure levels of the gas flowing through the nozzle and Figure 17b shows the distal end base of the nozzle. Entry of ambient gas at the proximal end of the nozzle at the laser beam entry opening 30 is shown in Figure 17a as the high pressure at the laser beam entry opening 30 where the ambient gas enters into the nozzle. As the gas travels distally or down the delivery conduit 40, portions of the gas are diverted radially by the diverting members 42, 44, 46. As shown by Figures 17a and 17b, the pressures towards the distal end of the nozzle 20 (in particular at the distal inlet opening 24) are reduced and are minimised at the weld point 50. The pressures at the distal end of the nozzle 20 are at a maximum towards the periphery of the distal inlet opening 24. This is because of the high velocity jets of ambient gas entering the nozzle 20 at the edge of the distal inlet opening 24. Local high pressures can also be seen at the diverging flow path sections provided by the flange 56 and the deflector lips 70, 72 which accelerate the incoming gas as described above. As shown by Figure 17b, the pressures at the centre of the distal inlet opening 24 (i.e. at the weld point 50) are at a minimum as the majority of the incoming ambient gas atthe distal inlet opening 24 is deflected axially into the nozzle 20 by the first 60 and second 62 deflectors, before it converges at the weld point 50, as described above.

[0130] Figure 17a shows that the incoming ambient gas flowing from the proximal inlet opening (in this embodiment the laser beam entry opening 30) is deflected radially away from the central axis 21 of the nozzle and thus the optical path of the laser beam. This ensures that the incoming gas from the proximal end of the nozzle is not directed towards the weld point 50. There is a natural propensity for the incoming jet of gas from the proximal inlet opening to adhere or tend towards one side of the top openings of the diverting members 42, 44, 46 and this can be seen in Figure 17a as the column of gas flowing axially down the delivery conduit 40 tilting towards one side of the delivery conduit 40. In some embodiments, the top openings of the diverting members 42, 44, 46 are slanted so as to encourage this behaviour thereby further preventing the gas from being directed at the weld point 50.

[0131] Figures 18a and 18b show a simulation of the pressures generated within the nozzle 20 of the embodiment of Figure 12 and Figures 19a and 19b show a simulation of the pressures generated within the nozzle 20 of the embodiment of Figure 13. As shown by these figures, the pressures at the weld point 50 are kept at a minimum.

[0132] Figures 20-25 show example dimensions of the nozzle 20 according to embodiments of the invention.

[0133] The nozzle may be formed using any suitable manufacturing method including, for example, by using a casting process. In some embodiments, the nozzle is formed using additive manufacturing methods.

[0134] The nozzle and the laser head may be formed as separate parts, the nozzle comprising means suitable for mounting the nozzle to the laser head. In other embodiments, the nozzle and the laser head may be formed together as a unitary part, for example as a single part. In embodiments where the nozzle is formed using additive manufacturing methods, the nozzle and the laser head may be formed as a unitary single part which may be directly connectable to the laser beam generator.

[0135] The various embodiments described herein are presented only to assist in understanding and teaching the claimed features. These embodiments are provided as a representative sample of embodiments only, and are not exhaustive and / or exclusive. It is to be understood that advantages, embodiments, examples, functions, features, structures, and / or other aspects described herein are not to be considered limitations on the scope of the invention as defined by the claims or limitations on equivalents to the claims, and that other embodiments may be utilised and modifications may be made without departing from the spirit and scope of the claimed invention. Various embodiments of the invention may suitably comprise, consist of, or consist essentially of, appropriate combinations of the disclosed elements, components, features, parts, steps, means, etc., other than those specifically described herein. In addition, this disclosure may include other inventions not presently claimed, but which may be claimed in future.

Claims

1. CLAIMS1. A nozzle for use with a laser beam welding machine, wherein:a proximal end of the nozzle comprises means suitable for mounting the nozzle to a laser head of a laser beam generator for generating a laser beam directed at a weld point on a workpiece;a distal end of the nozzle comprises a distal inlet opening for allowing ambient gas to enter into the nozzle;wherein the nozzle comprises:a laser beam entry opening provided at the proximal end of the nozzle for receiving the laser beam;a laser beam exit opening provided at the distal end of the nozzle for delivering the laser beam onto the workpiece;the laser beam being configured to travel from the laser beam entry opening through the laser beam exit opening to the weld point on the workpiece along an optical path extending axially through the nozzle;an outlet port fluidly connectable to a vacuum pump for suctioning gas out of the nozzle, thereby reducing the pressure at the weld point.

2. A nozzle according to claim 1, wherein the outlet port is provided towards the proximal end of the nozzle.

3. A nozzle according to claim 1 or 2, wherein the outlet port is radially spaced from a central axis of the nozzle.

4. A nozzle according to claims 1, 2 or 3, wherein the nozzle comprises four outlet ports symmetrically disposed about a central axis of the nozzle.

5. A nozzle according to any one of the preceding claims, wherein the distal inlet opening comprises a first deflector, the first deflector comprising an axially extending deflector wall configured to deflect gas entering the distal inlet opening axially into the nozzle before it reaches the weld point.

6. A nozzle according to claim 5, wherein the distal inlet opening comprises a second deflector radially spaced from the first deflector, the second deflector comprising an axially extending deflector wall configured to deflect gas entering the distal inlet opening axially into the nozzle before it reaches the weld point.

7. A nozzle according to any one of claims 5 or 6, wherein the first deflector comprises an annular wall and / or wherein the second deflector comprises an annular wall, the first deflector encircling the second deflector.

8. A nozzle according to any one of claim 5 to 7, whereinthe first deflector comprises an outwardly extending lip, the lip extending radially from the first deflector wall and wherein the lip connects to the deflector wall via an inner curved wall, such that the first deflector lip defines a diverging flow path for gas entering the distal inlet opening;and / orwherein the second deflector comprises an outwardly extending lip, the lip extending radially from the second deflector wall and wherein the lip connects to the deflector wall via an inner curved wall, such that the second deflector lip defines a diverging flow path for gas entering the distal inlet opening.

9. A nozzle according to claim 8, wherein the first deflector lip comprises a sharp outer edge; and / or wherein the second deflector lip comprises a sharp outer edge.

10. A nozzle according to claim 8 or 9, wherein the first deflector lip extends from the entire circumference of the first deflector wall; and or wherein the second deflector lip extends from the entire circumference of the second deflector wall.

11. A nozzle according to any one of the preceding claims, wherein the distal inlet opening comprises an outwardly extending flange, wherein the flange connects to the distal inlet opening with an inner curved wall such that the flange defines a diverging flow path for gas entering the nozzle at the distal inlet opening.

12. A nozzle according to any one of the preceding claims, wherein the nozzle comprises:a proximal inlet opening at the proximal end of the nozzle for allowing ambient gas to enter into the nozzle;a proximal end deflector comprising a radially extending diverting member configured to divert gas entering the proximal inlet opening away from the optical path of the laser beam.

13. A nozzle according to claim 12, wherein the proximal end deflector comprises an inner delivery conduit extending axially from the proximal inlet opening, the diverting member extending radially outward from the inner delivery conduit, wherein the inner delivery conduit is configured to receive gas from the proximal inlet opening and flow gas to the diverting member.

14. A nozzle according to claim 13, wherein the diverting member extends from the circumference of the delivery conduit and comprises a substantially conical concave shape so as to direct the gas away from the weld point at the distal end of the nozzle.

15. A nozzle according to any one of claims 12 to 14, wherein the proximal end deflector comprises three radially extending diverting members.

16. A nozzle according to any one of the preceding claims, wherein the nozzle comprises a rolling element for maintaining a predetermined distance between the distal end of the nozzle and the workpiece.

17. A nozzle according to claim 16, wherein the rolling element maintains a distance of between approximately 0.5mm to 3mm between the distal end of the nozzle and the workpiece.

18. A nozzle according to any one of the preceding claims, wherein a distal end face of the nozzle comprises a weld bead opening, the weld bead opening comprising a radiallydisposed groove extending radially from the central longitudinal axis of the nozzle to an outer perimeter of the distal inlet opening, the weld bead opening being configured to raise a portion of the distal end face of the nozzle.

19. A nozzle according to claim 18, wherein the weld bead opening extends radially in one direction from the central longitudinal axis of the nozzle to the outer perimeter of the inlet opening.

20. A nozzle according to claim 18, wherein the weld bead opening extends radially in opposing directions from the central longitudinal axis of the nozzle to the outer perimeter of the inlet opening.

21. A nozzle according to any one of claims 18 to 20, wherein the weld bead opening comprises an axial height of approximately 1mm-5mm.

22. A nozzle according to any one of the preceding claims, wherein a distal end face of the nozzle comprises a C-seal surrounding the distal inlet opening and configured to control the amount of gas entering the nozzle at the distal inlet opening.

23. A laser welding system for welding a workpiece by using a laser, comprising:a laser beam generator for generating a laser beam directed at a weld point on the workpiece;a laser head for directing the laser beam to the weld point;a nozzle according to any one of claims 1 to 22;the nozzle being optically connectable with the laser head so as to receive the laser beam from the laser head.

24. A laser welding system according to claim 23, comprising a vacuum pump connected to the outlet port.

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