NO347786B1

NO347786B1 - A ski pole

Info

Publication number: NO347786B1
Application number: NO20191211A
Authority: NO
Inventors: Christian Gløgård; Ola Stuveseth; Jon Holmestad; Svein Pedersen
Original assignee: Brav Norway As
Priority date: 2019-10-11
Filing date: 2019-10-11
Publication date: 2024-03-25
Also published as: WO2021069563A1; EP4041420A1; CN114728196A; US20230218977A1; NO20191211A1

Description

The present invention concerns a ski pole. More specifically, the invention is directed to a favorable ski pole comprising a longitudinal shaft which has high breaking strength, stiff (low span) and with aerodynamically properties without increasing the weight of the shaft.

BACKGROUND

Hand held ski poles have been used together with skies for centuries, primarily for helping the skier maintain balance when skiing, but also to help the skier get traction for movement in a forward direction. When modern skiing was in its infancy almost 200 years ago, a single pole was often used. However, in modern skiing two ski poles are used both for downhill and cross-country skiing.

As modern skiing is constantly developing, focus is put on the development of new and improved skiing equipment to further advance the sport. Ski poles have been transformed fundamentally from the single pole of the 19 <th >century to the light weight versions of today, when the skier carries one ski pole in each hand.

Traditionally, the typical cross-country ski pole, and also the downhill versions of the poles, has a shaft made from resin-bound fiber layers which provide the walls surrounding the continuous cavity of the shaft.

In racing ski poles, the fibers primarily comprise carbon fibers while the generalpurpose ski poles usually employ glass fiber or a combination of carbon and glass fibers. The binder resin comprises e. g. an epoxy resin or a polyester resin. It is prior known to make a cross-sectionally circular pole shaft downward tapered so as to place its center of gravity higher up, i.e. to provide a lightweight lower end and a low air resistance for the lower end.

The traditional ski pole comprises a circular hollow shaft fitted with a handle, a disc or a snow guard for keeping the pole from sinking too far into the snow, and a spike in the bottom end to ensure traction.

The circular-and/or elliptic shaped cross-section of the shaft, produce a drag and/or a lift when the skier push them forward into a pendulum movement. This drag/lift causes the ski pole to wander off to either left or right. This drag force deviation from a strict pendulum movement has the disadvantage that the skier must use unnecessary force to correct the trajectory of the ski pole into a strictly forward directed motion. This drag effect is small and may barely be noticeable to an exerciser. But to a professional athlete, every second, even tenths and hundreds counts, since very often competitions are decided by very small margins.

The publication US 5611571 A discloses a pole shaft for a cross-country ski pole having a circular cross-section that changes progressively downwards into a droplet shape and, below the mid-way point of the shaft, the length of the droplet shape in relation to its width increases while the cross-sectional area diminishes. By virtue of the droplet shape, the ski pole can be given more rigidity in skiing direction, whereby the bottom end of the pole can be made lighter while improving the aerodynamics of the pole. The droplet shape of the cross-section may provide better aerodynamics, but it simultaneously provides a ski pole with increased weight and unstable in use.

The publication EP 2308 569 A1 discloses a ski pole having a triangular crosssection. The substantially triangular cross-sectional shape is stiff (low span), has high breaking strength and reduces some of the drag forces compared to circular cross-section. The ski pole is arranged with one of the three sides of the triangular shape of the pole facing directly forward into the direction of movement of the skier holding the ski pole. Furthermore, the substantially triangular cross-sectional shape of the ski pole requires less material to be used to produce the pole as compared to a ski pole with a circular cross-section and are therefore considerably lighter in weight.

The publication US 2007/0108756 Al relates to a collapsible pole system. One embodiment is directed at a collapsible ski pole with an improved locking system that minimizes operational failures. The collapsible ski pole includes at least two pole segments and a non-twisting locking mechanism disposed between each of the corresponding pole segments. The pole segments are cross-sectionally shaped to prevent rotation with respect to one another. Therefore, the non-twisting locking mechanisms cannot be misaligned or impeded as a result of the inadvertent twisting of the corresponding pole segments.

However, as the sport of skiing is constantly developing, there is a constant search and demand for improved solutions to provide new ski poles which are better suited to the sport of skiing and which may give the athlete benefits of hundreds, tenths or seconds during a race.

A pole shaft is required to have a certain strength especially against buckling, which constrains possibilities for the reduction of weight and diameter.

Thus, the object of the invention is to provide a pole shaft for a ski pole that is stiffer (lower span) than the prior arts pole shaft, with higher breaking strength (pull to limit) than the prior art pole shaft and with aerodynamic properties without compromising very much or at least within certain defined perimeters, in weight and diameter.

SUMMARY OF THE INVENTION

The present invention is directed to a ski pole comprising a longitudinal shaft. The shaft includes a cross-section that comprises:

-a first part including a curved first portion arranged symmetric about a crosssectional centerline (CL) of the shaft, wherein the curved first portion is a circular arc defined by an angle θ and forms part of a circumference of a circle with radius (R) and

-a second part including a second portion arranged symmetric about the cross -sectional centerline (CL).

The first part is connected to the second part by side parts including side portions, each side part comprises a first end connected to an end of the first part and a second end connected to an end of the second part, each connection between the side parts and the first and second parts forms a corner, such that there are total four corners in the cross-section of the shaft, and

wherein the length of the second portion is equal to or less than the radius (R) of the curved first portion.

The first part may include a straight or another secondary curved portion connected to the curved portion such that they together constitute the first part. The first part may constitute only the curved portion.

The same applies to the second part, which may constitute a secondary curved and/or straight portion connected to the second portion such that they together constitute the second part. The second part may constitute only the second portion, where the second portion is a straight potion or a curved portion.

The side parts may constitute a straight portion and/or a curved portion or a combination thereof.

Each connection between the side parts and the first and second parts forms a corner, wherein the corner may be rounded such that there are no sharp edges for better aerodynamic properties.

In terms of strength and aerodynamics, the optimum solution for a ski pole is achieved according to the invention in a manner such that the cross-section comprises a first part having a curved portion, a second part having a second portion and wherein the first and second parts are connected by side parts providing four corners at the connections between the different parts.

The longitudinal shaft of the ski pole may gradually change in diameter and/or shape towards the lower section of the shaft.

The first part, the second part and the side part may be arranged symmetric about the cross-sectional centerline parallel to the moving (forward) direction of the skier. The entire cross-section of the shaft may be symmetric about the centerline (CL).

The first curved portion is an arc.

The first curved portion is a circular arc. A circular arc may be defined as a segment of a circle.

The length of an arc of a circle with radius (R, r) and subtending an angle θ (measured in radians) with the circle center, i.e., the central angle, is:

L = θ*R ;;This is because: ;;The curved first portion is defined by the angle θ and forms part of a circumference of a circle with radius (R). Thus, this means that all points of an outer perimeter of the cross-sectional shape of the shaft, lies at or within a circumference of circle with radius (R). ;;The curved first portion may be the arc of a semi-circle, or an arc which is less than the semi-circle or and arch which is greater than the semi-circle. ;;In an embodiment of the invention, the angle θ may be less than 180 degrees. ;;In another embodiment, the angle may be: 180° ˃ θ ˃ 160°. ;;The length of the second part is equal or less than the radius (R) of the curved first portion. This means that the cross-sectional shape gradually narrows in from the curved first portion to the second part. ;Furthermore, the two times radius (R) of the curved first portion may be equal to the greatest width of the cross-section of the shaft. This means the curved front portion defines a circular arc with radius (R), and that the greatest width of the crosssection of the shaft does not exceed the 2x radius (diameter) of the circle. ;;The curved first portion (circular arc) and each of the four corners may all be located on, at or coincide with, an outer circumference of the circle with the radius (R). Hence, each of the four corners are points located on a circumference of a circle. ;;The side parts and the back part may be straight, curved lines or a combination thereof. In an embodiment, the back and side portions are slightly curved lines (curved outwards). Each point of the slightly curved lines lies within the circumference of the circle with radius (R). ;;The curved first portion may be the front part of the ski pole, meaning that it is headed forward in the skiing direction. Thus, the second part is the back part of the ski pole. ;;The second part may be the front part of the ski pole, meaning that it is headed forward in the skiing direction. Thus, the curved first part is the back part of the ski pole. ;;Test results shows that the above mentioned four corners cross-sectional shape of a shaft, has surprisingly increased strength compared to existing cross-sectional shapes, such as circular (round) or triangular shape. The test was performed by measuring the deformation (span) for different cross-sectional shapes of shafts. The testing shafts where applied a predefined load N in order to measure their individual span resulting from the load (force) N applied. Their individual span was later compared. Low value of span means that the shaft is stiff and more resistant to deformation. ;;Also “pull to limit tests” was performed where the individual shafts where tested by applying an increasing load N, until the shaft breaks. The higher load (max load) means higher breaking strength. ;;When studying the test results from the above-mentioned testes, the shaft with the four corners cross-sectional shape of the present invention has remarkable and surprisingly lower span (meaning; stiffer) compared to other cross-sectional shapes tested. In addition, the shaft of the present invention also has the higher breaking strength. ;To measure the aerodynamics, which is also very important for a skier, a test in a wind tunnel was performed for indicating the drag coefficient of different crosssectional shaped shafts. The drag coefficient is a dimensionless quantity that is used to quantify the drag or resistance of an object in a fluid environment, such as air or water. It is used in the drag equation in which a lower drag coefficient indicates the object will have less aerodynamic or hydrodynamic drag. The drag coefficient is always associated with a particular surface area. ;;The shaft was tested at 30, 45, 75, 90 and 105 km/h. Relevant speed during skiing are up to 50 km/h, higher speed is mostly during downhill skiing where the poles are held in a backward direction and are therefore not very relevant. In addition, different angles of the poles have been measured such as 0, 45, 90 and 180 degrees. Where the angles 0 and 45 are the most relevant angles of the wind in relation to the shaft. The test result shows that the curved first portion with a slightly rounded geometry of the side parts and second portion, has better aerodynamic properties than the triangular shape at relevant speed and angles. The four corners crosssection has consistently better aerodynamically properties compared to the circular cross-sectional shape. ;;Thus, the improved aerodynamics at relevant wind speed, may probably provide better pendulum characteristics, which skiers considers very important for a ski pole. ;;Hence, the shaft for a ski pole of the present invention shows a remarkable and surprisingly combination of increased rigidity, breaking strength and improved aerodynamics without increasing the weight of the shaft. ;;The invention is directed to a ski pole comprising a longitudinal pole shaft, in which the cross-section of said pole shaft in one end (top) has four corners, and in which the cross-section of said pole shaft in the opposite end (bottom) is circular; the cross-section of said pole gradually adopting a four corner shape to circular crosssection moving along the ski pole from one end to the opposite end. The circular shape may be provided at the lower part of the ski pole. ;;A pole shaft may be hollow and made from e. g. of longitudinal and transverse fiber layers. The walls surrounding the shaft cavity can be of equal thickness or the wall thickness may fluctuate over various sections of the shaft length. ;;It may be preferred that adjacent to the lower end of a shaft the four corner shape changes over a short transition zone into a shaft having a substantially circular cross-section. Thus, the sleeve of a snow ring need not be subjected to any modifications as compared to the currently available solutions. ;The longitudinal pole shaft may comprise a top end and a bottom end, wherein the radius (R) of the pole shaft is gradually decreasing from the top end towards the bottom end. ;;The ski pole may comprise a hand grip mounted to the top end of the longitudinal pole shaft. ;;At a distance from the bottom end of the pole shaft, the pole shaft may be provided with a section with a slightly distorted diameter compared to the section immediately preceding and following said distorted diameter section of the pole shaft. ;;This diameter distorted section may function as a friction increasing feature to enhance fixation of a replaceable means for limiting the sinking of the ski pole into ground surfaces, such as a disc structure or a snow guard, when the ski pole is used for skiing or walking. ;;In one embodiment, the diameter distorted section may have a length along the ski pole of about 5-40 mm, more preferably about 10-30 mm, and most preferably about 15-25 mm. The diameter distorted section may be placed about 10-40 mm from one end of the ski pole of the invention, more preferably about 20-30 mm from one end, and most preferably about 22-28 mm from one end of the ski pole of the invention. ;A snow ring and a pole grip may be attached to the pole shaft such that the front part of the cross-section is directed forward in skiing direction. ;;FIGURES ;;The description above, as well as further objects, features and advantages of the present invention will be more fully appreciated by reference to the following detailed description of the preferred embodiment which should be read in conjunction with the accompanying drawings in which: ;;Fig. 1 shows a cross-section of the shaft of a ski pole having four corners. ;Fig. 2 shows the cross-section of the shaft of a ski pole in relation to a circle with radius R. ;;Fig. 3 shows different views of the shaft for a ski pole and the crosssectional views at different sections of the shaft. ;Fig. 4 shows a table of stiffness (span) and breaking strength test results in relation to a version of the triangular shaped cross-section. ;;Fig. 5 shows a table of stiffness (span) and breaking strength test results in relation to another version of the triangular shaped cross-section. ;Fig 6 shows a table of stiffness (span) and breaking strength test results in relation to a cross-sectional shape of the present invention. ;;Fig. 7 shows a summarized table with the average test values for triangular shape versus the four corners shape of the present invention. ;;Fig. 8 shows test results from wind tunnel with different cross-sectional shapes at different speed. ;;Figs 9 a-d shows graphically the test results of fig 8. ;;DETAILED DESCRIPTION OF THE FIGURES ;;Figure 1 shows a cross-section 2 of a longitudinal shaft 1 for a ski pole. The shaft 1 includes a cross-section 2 that comprises a first part 3 with a curved first portion arranged symmetric about a cross-sectional centerline (CL) of the shaft 1, and a second part 4 with a second portion 4 arranged symmetric about the cross-sectional centerline (CL). ;;The first part 3 is connected to the second part 4 by side parts 5 with side portions, each side part 5 comprises a first end 5’ connected to an end of the first part 3 and a second end 5’’ connected to an end of the second part 4, each connection between the side parts 5 and the first and second parts 3, 4 forms a corner 6, such that there are total four corners 6 in the cross-section 2 of the shaft 1. ;;As shown in figure 1 the corners 6 may be rounded such that there are no sharp edges for better aerodynamic properties. Rounded edges may also be easier to manufacture using layers of carbon fibers. ;;In terms of strength and aerodynamics, the optimum solution for a ski pole is achieved according to the invention in a manner such that the cross-section of the shaft comprises four corners 6. ;The curved first portion and/or the second portion may be symmetric about the centerline (CL). The first portion, the second portion and the side portions may all be symmetric about the centerline (CL). ;;The curved first portion may be a circular arc having length L and defined by an angle θ and forms part of a circumference of a circle with radius (R). Thus, this means that all points of an outer perimeter of the cross-sectional shape lies at or within a circumference of circle with radius (R). ;;Figure 2 shows that the curved first portion is a circular arc with radius (R). The circle is drawn in dotted lines and enclosing the entire cross-sectional shape 2 of the shaft 1. ;;The curved first portion may be the arc of a semi-circle. Figure 2 shows that the curved first portion may be circular arc which constitutes less than a semi-circle. Thus, the angle θ is less than 80 degrees. ;;The length of the second part 4 may be equal or less than the radius (R) of the curved first portion. This means that the cross-sectional shape gradually narrows in from the curved first portion to the second part 4. ;;Furthermore, the two times radius (R) of the curved first portion may be equal to the greatest width of the cross-section of the shaft. This means the curved front portion defines an of a circle with radius (R), and that the greatest width of the crosssection of the shaft does not exceed the 2x radius (diameter) of the circle. ;;Fig 2 also shows that the curved first portion and each of the four corners may all be located on or at an outer circumference of the circle with the radius (R). Hence, each of the four corners 6 are points located on or at a circumference of a circle. ;The side parts and the second part may be straight, curved portions or a combination thereof. In an embodiment, the back and side portions are slightly curved portions as shown in figure 1 and 2. ;;The curved first portion (first part 3) may be the front part of the ski pole, meaning that it is headed forward in the skiing direction. Thus, the second part 4 is the back part of the ski pole. ;;The second part 4 may be the front part of the ski pole, meaning that it is headed forward in the skiing direction. Thus, the curved first part is the back part 4 of the ski pole. ;Figure 3 shows different views of a shaft 1 for a ski pole and the cross-sectional 2 views at different sections of the shaft 1. ;;The longitudinal shaft 1 may comprise a top end and a bottom end, wherein the radius (R) or cross-sectional width of the shaft 1 is gradually decreasing from the top end towards the bottom end. ;;Section B-B shows a cross-section 2 of the top end of the shaft viewed downwards towards the bottom end. ;;Section C-C shows a section closer towards the bottom end of the shaft where the cross-section of the shaft still has a significant four corners shape. ;;Wherein in the section D-D the cross-section of the shaft is gradually adopting a circular cross-section. ;;Thus, the top end of the shaft of the present invention, may comprise a cross-section having four corners 6, and wherein the bottom end is provided with a circular crosssection. The cross-sectional shape of the top end of the shaft may gradually change towards the cross-sectional shape of the bottom end. ;;At a distance from the bottom end of the pole shaft, the pole shaft may be provided with a section with a slightly distorted diameter compared to the section immediately preceding and following said distorted diameter section 9 of the pole shaft. The section is shown in detail A, in figure 3. ;;This diameter distorted section 9 may function as a friction increasing feature to enhance fixation of a replaceable means for limiting the sinking of the ski pole into ground surfaces, such as a disc structure or a snow guard, when the ski pole is used for skiing or walking. ;;The ski pole may further be configured with features for securing attachment and correct positioning of an unsymmetrical replaceable means for limiting the sinking of the ski pole into ground surfaces, such as a disc structure or a snow guard, in a desired direction relative to the shape of the ski pole. ;;In one embodiment, the diameter distorted section 9 may have a length along the ski pole of about 5-40 mm, more preferably about 10-30 mm, and most preferably about 15-25 mm. The diameter distorted section 9 may be placed about 10-40 mm from one end of the ski pole of the invention, more preferably about 20-30 mm from one end, and most preferably about 22-28 mm from one end of the ski pole of the invention. ;;A snow ring and a pole grip may be attached to the pole shaft such that the front part of the cross-section is directed forward in skiing direction. ;;The diameter distorted section of the above embodiments is primarily a feature which is designed to enhance friction when a stopper means is used to firmly fix a replaceable means for limiting the sinking of the ski pole into ground surfaces, such as a disc structure or a snow guard. The stopper, which is designed to be compatible with the replaceable means for limiting the sinking of the ski pole into ground surfaces, is aided in its stopper function by the enhanced friction of the diameter distorted section. Preferably, the diameter distorted section 9 may have a crosssectional diameter less than the cross-sectional diameters of the sections immediately preceding and following said diameter distorted section. However, the diameter distorted section 9 may have a cross-sectional diameter which is greater than the cross-sectional diameters of the sections immediately preceding and following said diameter distorted section. ;;The feature for securing attachment may in a desired direction of such unsymmetrical means may be a slot placed diametrically across the circular crosssectional end of the ski pole as shown in detail A, in figure 3. ;;This slot may also be place slightly off center, or it may be placed off center to such a degree that the slot is a recess. The slot may preferably be about 1-10 mm deep, more preferably 2-8 mm deep, and most preferably 3-6 mm deep. However, it is contemplated that the slot of this embodiment may be replaced with other features for achieving the same result, such as one or more lips on the ski pole in the same area as the slot, or along the side of the ski pole in this area. It is also possible to achieve the same result with two or more slots. ;;In another embodiment of the ski pole of the invention, the ski pole may have incorporated means for enhancing the grip of the pole onto ground surfaces. This may be achieved by fitting the ski pole with a spike structure (not shown) in the end of the ski pole facing the ground when it is used for skiing or walking. The spike structure may be formed from any material which provides the material strength necessary for providing a grip on the desired surface. ;;Figure 4 shows a table of the deformation test with a version of the triangular crosssectional shaped shaft. Previous tests have shown that the triangular cross-sectional shape shaft has less span (less deformation) and higher breaking strength than a circular cross-section shape shaft. ;Therefore, the test results shown in figure 4 and 5 was performed on tr iangular cross-sectional shapes to compare it with the new four corners 6 cross-sectional shape (figure 6) according to the present invention. ;;In the following tests, the four corners cross-sectional shape of the present invention is also referred to as “Aero” or “Triac Aero” as a working title. ;;The test was performed by mounting a shaft between to supports with a distance of 800 mm between each other. The deformation test was performed using a pressure of 10-300 N at a center location on the shaft between the two supports. The deflection or span was measured for the tip and butt and entered into the table. Tests was performed on a front side, back side and side portions. One additional side test was performed to the Aero shape since it has four corners 6. ;;A summarized comparison table is shown in figure 7 where the triangular shape is named as: 2.5 v2 and 2.5 v4. ;;From the summarized table in figure 7, it is clear that the Aero shape has surprisingly less span both for the tip and for the butt for all sides. A column for the average measurement (for 3 sides) is also shown in the table, stating that the Aero shape has increased stiffness (i.e. less pan) than the comparable triangular crosssectional shapes. ;;In the last columns in figure 7, the shafts where tested with a maximum load N for testing the braking strength in the transverse axis (perpendicular to the longitudinal direction) of the shafts. The test is also referred to as the “pull to limit” test. ;Side 1 is here referred to the front side and side 3 referring to the back side. The results show that all sides of the four corner 6 shape (Aero) of the present invention, has increased breaking strength compared to the triangular cross-sectional shape. ;It may therefore, with great probability, be concluded that the Aero shape crosssectional shaft has less span and increased breaking strength compared to both the triangular cross-sectional shape and the circular (round) cross-sectional shape. In addition, as shown in the table of figure 7, the Aero shaped shaft has slightly lower weight than the triangular shape (we already know that the triangular shaped shaft is lighter in weight than the circular shaped). The weight is 55,39 g per meter, which is slightly lower than the weight of the triangular shape of: 55,99 g per meter and 56,66 per meter. ;;A test of Aerodynamics where also performed in a wind tunnel. Aerodynamics is a study of motion of air, particularly as interaction with the cross-sectional shape of the shaft. To measure the aerodynamics, a drag coefficient is often used. The drag coefficient is a dimensionless quantity that is used to quantify the drag or resistance of an object in a fluid environment, such as air or water. It is used in the drag equation in which a lower drag coefficient indicates the object will have less aerodynamic or hydrodynamic drag. The drag coefficient is always associated with a particular surface area. ;;Figure 8 shows the test results by measuring the “coefficient of drag” x area (Dd * A). The test was performed to different shafts having different cross-sectional shapes such as: rounded, triangular, Aero new straight, Aero new curved.

Aero new straight shape was tested with the curved first portion in the forward direction (into the wind) and where both the second part and side parts are straight portions (“new straight”).

Aero new curved shape was tested with the curved first portion in the forward direction (into the wind) and where both the second part and side parts are slightly curved portions (“new curved”).

The shaft was tested at 30, 45, 75, 90 and 105 km/h. Relevant speed during skiing are up to 50 km/h, since higher speed is mostly during downhill skiing where the poles are held in a backward direction and are therefore not very relevant.

In addition, different angles of the shaft (angle of the wind in relation to the shaft) have been measured such as 0, 45, 90 and 180 degrees. Where the angles 0 and 45 are the most relevant angles since it is in the main moving direction of the skier (the 45 is directly from the side and 180 are directly from back).

The test results show that the curved first portion (circular arc) with a slightly rounded geometry of the second part and side portions, has better aerodynamic properties than the triangular shape at relevant speed and angles. The four corners 6 cross-section shape has consistently better aerodynamically properties compared to the circular cross-sectional shape.

The graphs in figure 9 a) show that for a wind of 0 degrees (wind directly from in front), and at speed of 30 km/h – 50 km/h, the “new curved” cross-sectional shape (dotted lines) has the lowest drag.

The same result is shown in the graphs in figure 9 b), at wind angle of 45 degrees, where the “new curved” cross-sectional shape (dotted lines) has the lowest drag at the lower windspeed around 30 km/h.

Thus, one may conclude that the improved aerodynamics of the ski pole of the present invention, may most probably provide better pendulum characteristics for a skier during skiing.

To summarize, the shaft 1 for a ski pole of the present invention shows a remarkable and surprisingly combination of increased stiffness, rigidity and improved aerodynamics without increasing the weight of the shaft 1.

Claims

1. A ski pole comprising a longitudinal shaft (1), the shaft (1) includes a crosssection (2) that comprises:

-a first part (3) including a curved first portion arranged symmetric about a cross-sectional centerline (CL) of the shaft (1), wherein the curved first portion is a circular arc defined by an angle θ and forms part of a circumference of a circle with radius (R) and

-a second part (4) including a second portion arranged symmetric about the cross-sectional centerline (CL),

wherein the first part (3) is connected to the second part (4) by side parts (5) including side portions, each side part (5) comprises a first end (5’) connected to an end of the first part (3) and a second end (5’) connected to an end of the second part (4), each connection between the side parts (5) and the first and second parts (3, 4) forms a corner (6), such that there are total four corners (6) in the cross-section (2) of the shaft (1), and characterized in that a length (L1) of the second portion is equal to or less than the radius (R) of the curved first portion.

2. The ski pole according to claim 1,

wherein the angle θ is less than 180 degrees.

3. The ski pole according to any one of claims 1-2,

wherein the two times radius (R) of the curved first portion is equal to the greatest width of the cross-section of the shaft (1).

4. The ski pole according to any one of claims 1-3,

wherein the curved first portion and each of the four corners (6) are located on or at an outer circumference of the circle with the radius (R).

5. The ski pole according to any one of the preceding claims,

wherein the second part (4) and each of the side parts (5) are slightly curved portions.

6. The ski pole according to any one of claims 1-5,

wherein the shaft (1) comprises a top end and a bottom end, wherein the radius (R) is gradually decreasing from the top end towards the bottom end.

7. The ski pole according to claim 6,

wherein the top end of the shaft (1) comprises a cross-section according to any one of claims 1-4, and the bottom end is provided with a circular cross section.

8. The ski pole according to claim 7,

wherein the cross-sectional shape of the top end of the shaft (1) gradually changes towards the cross-sectional shape of the bottom while moving towards the bottom end.

9. The ski pole according to claim 8,

wherein at a distance from the bottom end of the shaft (1), the shaft (1) is provided with a section (9) with a slightly distorted diameter compared to the section immediately preceding and following said distorted diameter section (9) of the shaft (1).