Field of the Invention

The invention relates to a welding helmet that has a protective shield and a head suspension system that are pivotally connected to each other for swiveling between a protective position and an upraised position. The protective position can be adjusted by means of a stop mechanism that is based on a disengagably engaged spline coupling.

Background Art

Welding helmets are typically used in the mechanical and industrial art to protect welders from harmful irradiation emitted from the welding arc and from splashes, sparks and particles that may be ejected from welding area. Welding helmets typically can be suspended on the head of a wearer, so that the wearer has both hands available for welding and handling of workpieces.

Some welding helmets are furnished with an automatic darkening filter. An automatic darkening filter commonly has a switchable filter that automatically changes from a light- state to a dark- state in response to incident light generated by the welding arc. Thus, upon ignition of the welding arc the switchable filter automatically changes to the dark- state and protects the welder’s eyes from the irradiation of the welding arc. Once the welding is interrupted or ended the switchable filter automatically changes to the light-state so that the user can see through the filter at normal light conditions.

Accordingly, there are welding helmets that stay in position on a wearer’s head independent from the actual welding actions, for example during locating of the electrode toward the workpiece to be welded or during handling. There are welding helmets that have a protective shield that is used in a lowered position and which can be lifted toward an upraised position so that the protective shield uncovers the wearer’s face. This function is provided for example to allow the wearer to communicate or to handle a workpiece or welding equipment without the need to put off the welding helmet.

Typically, such welding helmets can be fixed in the upraised position by tightening a screw, or the protective shield may be only movable at relatively high forces to avoid self-returning of the protective shield toward the lowered position.

Although existing welding helmet provide for a variety of advantages there is still a need for a welding helmet that provides for easy handling and which helps maximizing the safety in the area of welding. Summary of the Invention

The invention relates to a welding helmet that comprises a protective shield and a head suspension system. The protective shield and the head suspension system are pivotally connected to each other for swiveling the protective shield relative to the head suspension system. In particular, the protective shield and the head suspension system are pivotally connected to each other for swiveling the protective shield relative to the head suspension system about a pivot axis in opposite directions upward or downward between a protective position, in which the protective shield covers a wearer’s face, and an upraised position, in which the protective shield uncovers the wearer’s face. The welding helmet further comprises a stop mechanism that restricts downward swiveling beyond the protective position. The stop mechanism comprises a spline coupling that enables the stop mechanism to be adjusted between a low position and a high position. In the low position the protective position of the protective shield is offset downward with respect to the high position. Further in the low position the protective shield is typically closer to a wearer’s face than in the high position. The spline coupling comprises a male spline part and a female spline part that are resiliently urged for engagement with each other. Further the male spline part and the female spline part are, preferably temporarily, disengageable from each other for adjusting the stop mechanism.

The invention is advantageous in that it provides a welding helmet that has a protective shield which protective position can be easily adjusted. In particular the adjustment can be accomplished by a simple operation step, namely by pushing or turning a knob. Further the invention is advantageous in that the adjusted position is automatically maintained.

Typically, a spline coupling as referred to herein is based on two generally cylindrical structures, the male spline part and the female spline part. The male spline part and the female spline part can be typically mated with each other to establish an anti-twist engagement between the male spline part and the female spline part. Typically, one of the male spline part and the female spline part has a plurality of splines that extend along a dimension parallel to the cylinder axis. Typically, the other one of the male spline part and the female spline part has at least one spline or a plurality of splines. The splines of the male and the female spline part are preferably configured for engaging when then the male and the female spline parts are mated.

Preferably the adjustment of the stop mechanism, and thus the adjustment of the protective position of the protective shield relative to the head suspension system, is enabled only during the male spline part and the female spline part are disengaged from each other. In an embodiment the welding helmet has a center knob that is arranged in concentric relationship with the pivot axis. Further the male spline part and the female spline part can be preferably disengaged by operating the center knob. Operating the operating the center knob may comprise rotating or pushing, for example. Typically, the center knob can be easily located by a wearer during wearing the helmet by touching so that the adjustment of the protective position is facilitated.

In an embodiment the welding helmet further comprises an attachment part that is attached or attachable to the head suspension system. The head suspension system may comprise a head band and may further have one or more top bands that extend from the headband over a wearer’s head. The protective shield is preferably pivotally suspended relative to the attachment part. In particular the protective shield is preferably pivotally fixed at the attachment part. Further the attachment part may be fixed at the headband of the head suspension system.

In an embodiment the attachment part forms (or provides) the female spline part. This means that the attachment part may comprise the female spline part. The female spline part preferably forms or comprises a plurality of splines that are arranged in a full or partial circumference about the pivot axis. The splines may particularly extend along a parallel of the pivot axis and protrude radially toward the pivot axis.

In an embodiment the male spline part is arranged within the female spline part. The male spline part may be axially and radially fixed against any linear movement relative to the female part. The male spline part preferably comprises a spline formed on a pawl that is resiliently urged toward the splines of the female spline part. The pawl is preferably radially movable (or essentially radially movable). In particular the pawl may be radially (or essentially radially) elastically bendable or deformable. The male spline part is preferably rotatable about the pivot axis when the pawl is retracted from the splines of the female spline part in a direction radially (or essentially) toward the pivot axis. Further, the female spline part and the male spline part interlock when the pawl is released. When the pawl is released the pawl preferably resets from the elastic deformation.

In an embodiment the center knob has at least one protrusion. Preferably the protrusion protrudes from the center knob in a dimension parallel to the pivot axis and laterally offset from the pivot axis. The protrusion preferably cooperates with the pawl such that the protrusion urges the pawl away from the splines of the female spline part upon twisting the center knob. In particular the protrusion may be (at least with a portion of it) arranged between the female spline part and the male spline part. In a situation in which the male and the female spline part are engaged (via the splines) a rotation of the center knob causes the protrusion to move between the pawl and the splines of the female spline part so that the protrusion pushes the pawl away from the splines of the female spline part. Further, in a situation in which the male and the female spline part are disengaged a further rotation of the center knob causes the center knob to entrain the male part via the protrusion.

In an embodiment the welding helmet (in particular the stop mechanism) comprises a bushing that is attached or attachable to the attachment part. The bushing preferably forms the female spline part. Further the female spline part preferably forms at least one spline or a plurality of splines that are arranged in a full or partial circumference about the pivot axis. The splines may particularly extend along a parallel of the pivot axis and protrude radially toward the pivot axis.

In an embodiment the male spline part comprises at least one spline or a plurality of splines that are arranged in a full or partial circumference about the pivot axis. The male spline part may be displaceably (in particular linearly displaceable) arranged within the female spline part for a displacement along the pivot axis. The male spline part is preferably resiliently urged toward a position in which the splines of the female spline part and the male spline part engage. The male spline part may be resiliently urged toward the position in which the splines of the female spline part and the male spline part engage by means of a spring, preferably a helical spring.

The male spline part is preferably rotatable about the pivot axis when displaced toward a position in which the splines of the female spline part and the male spline part are disengaged. Thus, the male spline part is rotatable relative to the female spline part when disengaged from each other. The male spline part is preferably formed by the center knob. Thus, the center knob may be pushed to cause the male spline part and the female spline part to disengage and to adjust the protective position of the protective shield.

In an embodiment the male spline part comprises a first engagement structure and the protective shield comprises a second engagement structure. The first and second engagement structure upon engaging with each other restrict the downward swiveling beyond the protective position. In particular the protective shield during swiveling downwards is stopped at the protective position as soon as the first and second engagement structure engage with each other.

In an embodiment the protective shield forms (or provides) the female spline part. This means that the protective shield may comprise the female spline part. The female spline part preferably has a plurality of splines that are arranged in a circumference about the pivot axis. The male spline part may comprise at least one spline or a plurality of splines that are arranged in a circumference about the pivot axis. The splines may particularly extend along a parallel of the pivot axis and protrude radially toward the pivot axis.

Preferably the male spline part is displaceably arranged for a displacement along the pivot axis. For displacing the male spline part, the welding helmet (in particular the stop mechanism) may comprise a knob that cooperates with the male spline part. For example, the knob, if pushed, may push the male spline part and thus may cause the male spline part to displace. The male spline part is preferably resiliently urged toward a position in which the splines of the female spline part and the male spline part engage. In particular the male spline part may be urged onto the protective shield by a helical spring. The male spline part is preferably rotatable about the pivot axis when displaced toward a position in which the splines of the female spline part and the male spline part are disengaged. Further the male spline part is preferably anti-twist locked against a rotation relative to the protective shield about the pivot axis when displaced toward a position in which the splines of the female spline part and the male spline part are engaged.

In one embodiment the welding helmet further comprises a friction wheel for adjusting a friction that impedes the swiveling of the protective shield relative to the head suspension system. The friction wheel preferably allows the protective shield to retain in intermediate positions between the protective position and the upraised position. The friction wheel may form part of a friction coupling that pivotally suspends the protective shield relative to the head suspension system. Further the friction coupling may comprise a screw connection which can be tightened or loosened for clamping or unclamping the protective shield relative to the head suspension system, respectively. The friction coupling preferably allows for adjusting different levels of clamping of the protective shield relative to the head suspension system via the screw connection. In particular the different levels of clamping may be continuous (meaning without discrete steps).

In an embodiment the protective shield comprises a clear visor. The welding helmet may have a welding visor that is arranged pivotally relative to the clear visor for pivoting between a welding position in which the welding visor covers the clear visor and a non-welding position in which the welding visor uncovers the clear visor. Alternatively, the protective shield may comprise a welding visor instead of a clear visor. In this alternative no additional welding visor may be provided.

The welding visor may have an automatic darkening filter. The automatic darkening filter is preferably based on two liquid crystal cells. The liquid crystal cells are electrically switchable between a light-state and a dark-state. The two liquid crystal cells are preferably arranged optically in sequence. Each liquid crystal cell comprises two transparent substrates with a liquid crystal layer arranged between. Each substrate is provided with an alignment layer that is in contact with the liquid crystal layer. The alignment layers provide for a default uniform alignment of the liquid crystals. Further, the two liquid crystal cells preferably comprise three polarizers, one of which being arranged between the two liquid crystal cells and the other two being arranged on outer sides. The outer side polarizers may be arranged with their light polarizing orientation in the same or substantially the same direction, whereas the inner polarizer may be oriented with its light polarizing orientation 90 degrees or substantially 90 degrees relative to the outer polarizers.

In the light- state the transmittance of the automatic darkening filter may be within a range of about 1 % to about 20%, in more particular within a range of about 5% to about 10%, whereas in the dark-state the transmittance of the automatic darkening filter may be within a range of about 0.0005% to about 0.1 %.

In one embodiment the welding visor comprises a permanent optical filter (instead of an automatic darkening filter). Such an optical filter may have a permanent transmittance within a range of about 0.0005% to about 0.1 %.

In a further embodiment the welding helmet has a sensor for detecting light, as for example light emitted from the welding arc. The sensor and the automatic darkening filter are functionally interconnected so that light above a predetermined light intensity detected by the sensor causes the automatic darkening filter to switch to the dark-state and the absence or non-detection of light above the predetermined light intensity causes the automatic darkening filter to switch to the light- state.

Brief Description of the Figures

Fig. 1 is a side view of a welding helmet according to an embodiment of the invention; Fig. 2 is a further side view of the welding helmet shown in Fig. 1 ;

Fig. 3 is a side view of the welding helmet shown in Fig. 1 at a different stage of operation;

Figures 4-6 are perspective views illustrating a stop mechanism for a welding helmet according to an embodiment of the invention;

Figures 7-9 are perspective views illustrating a further stop mechanism for a welding helmet according to an embodiment of the invention; and

Figures 10-12 are perspective views illustrating yet a further stop mechanism for a welding helmet according to an embodiment of the invention. Detailed of the Invention

Fig. 1 shows a welding helmet 1 according to the invention. The welding helmet 1 has a protective shield 2 which is illustrated in a protective position that corresponds to a position in which the protective shield 2 covers a wearer’s face. The welding helmet 1 further has a head suspension system 6 for supporting the welding helmet 1 on a wearer’s head. The welding helmet 1 further has a welding visor 3. The welding visor 3 is configured to filter those portions of light of a welding arc hat would be harmful for a wearer of the welding helmet 1 observing the welding arc through the welding visor 3.

The welding visor 3 therefore comprises an automatic darkening filter 5. The automatic darkening filter 5 allows a welder to safely observe the welding arc during welding. In the example the automatic darkening filter 5 is based on two liquid crystal cells. The liquid crystal cells are electrically switchable between a light-state and a dark-state. When switched in the dark-state, the automatic darkening filter 5 blocks a significant amount of light from being transmitted therethrough. This enables a user to observe a welding arc by seeing through the automatic darkening filter 5 without risking to be exposed to harmful light radiation from the welding arc. In the light-state the automatic darkening filter 5 permits a significant amount of light to be transmitted therethrough. Thus, the automatic darkening filter 5 in the light-state allows the user to see under ambient light conditions (in the absence of the welding arc). The two (or more) liquid crystal cells are arranged optically in sequence. This provides for multiplying the darkening effect (in particular in the dark-state) and thus a sufficient eye protection from light radiation.

The protective shield 2 is pivotally suspended relative to the suspension system 6. Thus, the protective shield 2 can be swiveled relative to a wearer’s head when worn. Further, the welding visor 3 is pivotally suspended relative to the protective shield. Thus, the welding visor 3 can be swiveled relative to the protective shield 2.

The welding visor 3 is illustrated in a welding position in which the welding visor 3 covers a see- through window (indicated as number 4 in Fig. 2) provided in the protective shield 2. The welding visor 3 is however pivotable between the welding position (shown in Fig. 1) and a non-welding position (shown in Fig. 2).

Fig. 2 shows the welding helmet 1 with the welding visor 3 in the non-welding position in which the welding visor uncovers the see-through window 4. The protective shield 1 is still in the protective position. The protective shield 2 has a clear visor 5 that closes the see-through window 4 in the protective shield 2. Thus, a wearer’s face is protected by the protective shield 2 and the clear visor 5 for example from particles ejected from a workplace the wearer faces toward. Although the clear visor 5 does not provide a sufficient protection against harmful light emitted from a welding arc, the clear visor 5 allows the wearer of the welding helmet 1 to see through the clear visor 5 at ambient light conditions. Therefore, in the protective position of the protective shield 2 with the welding visor 3 being in the non-welding position the welding helmet 1 may for example be used for protecting a wearer during grinding or similar works.

As illustrated in Fig. 3 the protective shield 2 of the welding helmet 1 further can be lifted upward or swiveled to an upraised position about a pivot axis A (extending perpendicular to the plane of the Figure through the point referred to as“A”). The swiveling of the protective shield 2 is provided relative to the head suspension system 6. Accordingly, the welding helmet 1 is configured such that the welding shield 2 can be swiveled on a wearer’s head while the head suspension system remains in place. The swiveling of the protective shield 2 relative to the head suspension system is independent from the pivoting of the welding visor 3 relative to the protective shield 2. Thus, the position of the welding visor 3 relative to the protective shield 2 is not changed by changing the position of the protective shield 2 relative to the head suspension system. This allows a wearer of the welding helmet 1 to temporarily lift the protective shield 2 away from his or her face toward the upraised position and to continue using the welding helmet 1 with the protective shield 2 in the protective position after, without changing the position of the welding visor 3.

The welding helmet 1 is configured for adjusting the protective position between a low position and a high position. In the low position the protective shield is offset downward with respect to the high position and vice versa (in the high position the protective shield is offset upward with respect to the low position). This allows a wearer to adjust the welding helmet in the high position, for example, so that the protective shield does not touch the wearer’s chest during works that require the wearer to look downwards. Alternatively, the wearer may adjust the welding helmet in the low position so that the wearer’s face is protected during works in which the wearer looks upwards.

Fig. 4 shows in a partial view of the welding helmet a stop mechanism 10 that restricts downward swiveling beyond the protective position. The stop mechanism 10 has a center knob 11 by which the protective position can be adjusted. In particular turning the center knob 1 1 in one direction causes the protective position to move downwards, whereas turning the center knob 1 1 in the opposite direction causes the protective position to move upwards. Upon releasing the center knob 11 the stop mechanism 10 automatically locks the adjusted protective position.

Fig. 5 shows the stop mechanism 10 in more detail in an exploded view. The stop mechanism 10 comprises a spline coupling 12. The spline coupling 12 comprises a male spline part 13 and a female spline part 14. The male spline part 13 comprises a spline 131 formed on a pawl 132. Further, the female spline part 14 comprises a plurality of splines 141. The plurality of splines 141 in the example are arranged in a full circumference about the pivot axis A. The plurality of splines 141 of the female spline part 14 protrude in a direction inwardly of the circumference at which the splines 141 are arranged, and the spline 131 of the male spline part 13 protrudes in the opposite direction. The male spline part 13 is arranged within the female spline part 14 (shown in Fig. 6 - although in the exploded view the male spline part 13 and the female spline part 14 are illustrated apart from each other for explanation purposes only). The spline 131 of the male spline part 13 is resiliently urged toward the splines 141 of the female spline part 14 by means of the pawl 132. In the example the male spline part 13 has two pawls 132 with a spline 131 on each pawl 132. In a situation in which the spline 131 of the male spline part 13 engages between two splines 141 of the female spline part 14, the male and female spline part 13, 14 are anti-twist locked (or interlocked) with each other. However, a situation in which the spline 131 of the male spline part 13 and the splines 141 of the female spline part 14 are disengaged, the male and female spline part 13, 14 are rotatable relative to each other about the pivot axis. The male spline part 13 and the female spline part 14 can be disengaged from each other in that the pawl or pawls 132 are retracted. In the example, the pawls 132 can be resiliently retracted in a direction essentially radially toward the pivot axis. Thus, the male spline part 13 and the female spline part 14 are resiliently urged for engagement with each other and disengageable from each other for adjusting the stop mechanism.

The center knob 11 is arranged in concentric relationship with the pivot axis A. Further the center knob 1 1 is rotatable about the pivot axis A. The center knob 1 1 has a protrusion 1 11. The protrusion 11 1 engages with the pawl 132. In a situation in which the center knob 11 1 is not operated (released) the pawl 132 is released too (and thus enables engagement of the spline 131 of the male spline part 13 with a spline or splines 141 of the female spline part 14). However, in a situation in which the center knob 11 is turned the protrusion 1 11 urges the pawl 132 radially inwardly (and thus causes the spline 131 of the male spline part 13 to disengage from the splines 141 of the female spline part 14). Once the spline 131 of the male spline part 13 is disengaged from the splines 141 of the female spline part 14 further turning the center knob 1 1 causes the stop mechanism 10 to adjust a new protective position. Upon releasing the center knob 11 the pawls 132 (because they are resiliently deformed) reset, thereby allow the male and female spline part 13, 14 to engage and further the pawls 132 push the center knob back in an initial position.

The male spline part 13 comprises a first engagement structure 133. Further the protective shield 2 comprises a second engagement structure 233. The first and second engagement structure 133, 233 in combination form a stop that restricts downward swiveling of the protective shield 2 beyond the protective position. In particular upon engaging with each other the first and second engagement structure 133, 233 restrict the downward swiveling beyond the protective position. However, the first and second engagement structure 133, 233 allow the protective shield 2 to be swiveled toward the upraised position.

The stop mechanism 10 suspends the protective shield 2 and the welding visor 3 for swiveling about the pivot axis A. In particular the female spline part 14 is formed by an attachment part 15 for attachment with the head suspension system (not illustrated in this view). In the example the attachment part 15 has a clamping fixture 151 for displaceably fixing the attachment part 15 to the head suspension system, in particular to a headband of the head suspension system. The attachment part 15 further has a release button 152 for unclamping and clamping the attachment part to or from the head suspension system.

Fig. 7 shows in a partial view of the welding helmet a further embodiment of a stop mechanism 10. The stop mechanism 10 restricts downward swiveling beyond the protective position. Again, the stop mechanism 10 has a center knob 11 that enables the protective position to be adjusted. In this embodiment pushing the center knob 1 1 enables that the protective position can be adjusted, whereas releasing the center knob causes the adjusted protective position to lock in place. The protective position can be changed by urging the protective shield 2 against the upraised position or the protective position. If the protective shield 2 is urged against the upraised position the protective position changes toward the high position. If the protective shield 2 is urged against the protective position the protective position changes toward the low position.

Fig. 8 shows the stop mechanism 10 shown in Fig 7 in more detail in an exploded view. The stop mechanism 10 again comprises a spline coupling 12 that is formed by a male spline part 13 and a female spline part 14. The male spline part 14 is formed by the center knob 11. Further the female spline part 14 is in the form of a bushing and is attached to an attachment part 15. The male spline part 13 comprises a plurality of splines 131 that are arranged in a circumference about the pivot axis A. The female spline part 14 comprises a plurality of splines 141. The plurality of splines 141 in the example are arranged in a partial circumference about the pivot axis A. The plurality of splines 141 of the female spline part 14 protrude in a direction inwardly of the circumference at which the splines 141 are arranged, and the splines 131 of the male spline part 13 protrude in the opposite direction.

The male spline part 13 is arranged within the female spline part 14 (shown in Fig. 9 - although in the exploded view the male spline part 13 and the female spline part 14 are illustrated apart from each other for explanation purposes only). The male spline part 13 is particularly displaceably arranged within the female spline part 14 for a displacement along the pivot axis A. The male spline part 13 is resiliently urged toward a position in which the splines 131 , 141 of the female spline part 14 and the male spline part 13 engage. Further the male spline part 13 is rotatable about the pivot axis in a situation in which the center knob 11 (and thus the male spline part 13) is displaced toward a position in which the splines 131 , 141 of the female spline part 14 and the male spline part 13 are disengaged. The male spline part 14 can be displaced toward a position in which the splines 131 , 141 of the female spline part 14 and the male spline part 13 are disengaged by pushing the center knob 11. Further the male spline part 13 resets toward the position in which the splines 131 , 141 of the female spline part 14 and the male spline part 13 are engaged by means of a spring 16.

The male spline part 13 comprises a first engagement structure 133. Further the protective shield 2 comprises a second engagement structure 233. The first and second engagement structure 133, 233 in combination form a stop that restricts downward swiveling of the protective shield 2 beyond the protective position. Further the first and second engagement structure 133, 233 in combination form a stop that restricts also upward swiveling of the protective shield 2 beyond the upraised position. In particular upon engaging with each other at the protective position the first and second engagement structure 133, 233 restrict the downward swiveling beyond the protective position. And upon engaging with each other at the upraised position the first and second engagement structure 133, 233 restrict the upward swiveling beyond the upraised position. However, the first and second engagement structure 133, 233 allow the protective shield 2 to be swiveled between the upraised position and the protective position.

The center knob 1 1 is arranged in concentric relationship with the pivot axis A. Once the splines 131 of the male spline part 13 are disengaged from the splines 141 of the female spline part 14 the male spine part 13 can be rotated relative to the female spline part 14 by positioning the protective shield 2 to either the upraised or the protective position. In the upraised and the protective position, the first and second engagement structure 133, 233 engage. Accordingly urging the protective shield 2 from the upraised position further upward causes the second engagement structure 233 to entrain the male spline part 13 via the first engagement structure so that male spine part 13 rotates in one direction with the protective shield. And urging the protective shield 2 from the protective position further downward causes the second engagement structure 233 to entrain the male spline part 13 via the first engagement structure so that male spine part 13 rotates in the opposite direction with the protective shield. Thereby the protective position can be adjusted. Upon releasing the center knob 1 1 the male spline part 13 resets and thereby allows the male and female spline part 13, 14 to engage.

The stop mechanism 10 suspends the protective shield 2 and the welding visor 3 for swiveling about the pivot axis A. The attachment part 15 can be attached with the head suspension system (not illustrated in this view). The attachment part 15 has a clamping fixture 151 for displaceably fixing the attachment part 15 to the head suspension system (as described above).

Fig. 10 shows in an exploded view a further embodiment of a stop mechanism 10. The same embodiment is shown in an alternative exploded view from a different perspective in Fig. 11. Further a cross-sectional assembly view of the embodiment of Fig. 10 is provided in Fig. 12.

The stop mechanism 10 comprises a spline coupling 12 that allows for adjusting the protective position. The spline coupling 12 comprises a male spline part 13 that is received between a first female spline part 14a and a second female spline part 14b. The first female spline part 14a corresponds to the“female spline part” of the invention, whereas the second spline part 14b is a further female spline part. The first female spline part 14a is formed by the protective shield 2 (visible in Fig. 11), whereas the second female spline part 14b is formed by an attachment part 15 for attachment with the head suspension system (not illustrated in this view).

The male spline part 13 comprises a plurality of splines 131 that are arranged on an outer circumference of the male spline part 13. The plurality of splines 141 in are particularly arranged in a full circumference about the pivot axis A. The plurality of splines 131 are uniformly distributed around the circumference of the male spline part 13.

The first female spline part 14a comprises a plurality of splines 141a that protrude from the protective shield 2. The plurality of splines 141a are circumferentially arranged and uniformly distributed around the pivot axis A. Further, the plurality of splines 141 a of the first female spline part 14a and the plurality of splines 131 of the male spline part are arranged and distributed for engaging or meshing with each other. This means that the male spline part 13 can engage with the protective shield 2 via the splines 131 of the male spline part 13 and the splines 141 a of the first female spline part 14a, respectively. When engaged the male spline part 13 and the first female spline part 14a are anti-twist locked with each other against a rotation about the pivot axis A. This means that the male spline part 13 and the protective shield 2 cannot rotate relative to each other about the pivot axis A when the male spline part 13 and the first female spline part 14a are engaged. The male spline part 13 comprises a first engagement structure 133. In the example the first engagement structure 133 is a pin that protrudes from the male spline part 13. Further the second female spline part 14b comprises a second engagement structure 233. In the example the second engagement structure 233 is provided by means of an arcuate groove about the pivot axis A formed within (or through) the second female spline part 14b. As shown in Fig. 12 the first engagement structure 133 is arranged within the groove and thus limited for a movement only within the groove. The second engagement structure 233 is particularly formed by one end of the groove. Therefore, the first and second engagement structure 133, 233 in combination form a stop that restricts downward swiveling of the protective shield 2 beyond the protective position. In particular upon engaging with each other the first and second engagement structure 133, 233 restrict the downward swiveling beyond the protective position. However, the first and second engagement structure 133, 233 allow the protective shield 2 to be swiveled toward the upraised position.

The second female spline part 14b comprises a plurality of splines 141 b that protrude from the attachment part 15. The plurality of splines 141 b are circumferentially arranged and uniformly distributed around the pivot axis A. Further, the plurality of splines 141 b of the second female spline part 14b and the plurality of splines 131 of the male spline part are arranged and distributed for engaging or meshing with each other. This means that the male spline part 13 can engage with the attachment part 15 via the splines 131 of the male spline part 12 and the splines 141 b of the second female spline part 14a, respectively. When engaged the male spline part 13 and the second female spline part 14b are anti-twist locked with each other against a rotation about the pivot axis A. This means that the male spline part 13 and the attachment part 15 cannot rotate relative to each other about the pivot axis A when the male spline part 13 and the second female spline part 14a are engaged. This prevents that the male spline part 13 inadvertentlyjointly rotates with the protective shell during adjusting the protective shield.

The male spline part 13 is displaceable along the pivot axis A (Fig. 12). In particular, the male spline part 13 is displaceably arranged within the first female spline part 14a for a displacement along the pivot axis A. The male spline part 13, by means of a helical spring 16, is resiliently urged toward a position in which the splines 131 , 141a of the first female spline part 14a and the male spline 13 part engage. However, the male spline part 13 is rotatable about the pivot axis A when displaced toward a position in which the splines 131 , 141a of the female spline part and the male spline part are disengaged. Further for disengaging, the male spline part 13 is displaced from the first female spline part 14a toward the second female spline part 14b. During displacing the male spline part 13 from the first female spline part 14a toward the second female spline part 14b, the splines 131 , 141 b of the male spline part 13 and the second female spline part 14b engage before the splines 131 , 141 a of the male spline part 13 and the first female spline part 141 a disengage. Therefore, the male spline part 13 is engaged with at least one of the first and second female spline part 14a, 14b while displaced from the first female spline part 14a toward the second female spline part 14b. Thereby the male spline part 13 is locked in place relative to the head suspension system while the protective shield can be rotated relative to the male spline part 13 for adjusting the protective position.

The stop mechanism 10 further has a knob 1 1 that is displaceable along the pivot axis A. The knob 1 1 cooperates with the male spline part 13 such that a displacement of the knob 11 also causes the male spline part 13 to displace. In particular by pushing the knob 1 1 against the male spline part 13 the male spline part 13 displaces against spring force of the spring 16. And upon releasing the knob 1 1 the spring 16 resets the male spline part 13 and the male spline part 13 resets the knob 11.

The stop mechanism 10 further comprises a friction wheel 17. The friction wheel 17 serves for adjusting a friction that impedes pivoting of the protective shield 2 relative to the attachment part 15. In particular the friction wheel 17 extends through the protective shield 2 and the welding visor 3. A screw connection is formed between a fixation plate 171 and the friction wheel 17. By turning the friction wheel 17 the screw connection is tightened or loosened and accordingly at least the protective shield 2 is more or less clamped, respectively. By more or less clamping the protective shield 2 the pivoting is more or less impeded by friction, respectively. This allows for retaining the protective shield 2 at various positions between the protective position and the upraised position.

The screw connection between the friction wheel 17 and the fixation plate is arranged coaxially with the pivot axis A. Further the knob 11 is arranged coaxially with the pivot axis A within the friction wheel 17. The knob 11 has fingers 1 11 that extend through holes within the friction wheel 17 for cooperating with the male spine part 13.

The stop mechanism 10 suspends the protective shield 2 and the welding visor 3 for swiveling about the pivot axis A. The attachment part 15 has a clamping fixture 151 for fixing the attachment part 15 to the head suspension system, in particular to a headband of the head suspension system.