hereinafter , with reference to drawings , preferred embodiments of the present invention will be described in detail . note that , in the drawings , same elements are denoted by the same reference numerals , and redundant descriptions are omitted . unless otherwise stated , the positional relations of , for example , top , bottom , left , and right are based on the positional relations shown in the drawings . furthermore , the dimensional ratios of the drawings are not limited to the ratios of the drawings . fig1 is a perspective view schematically showing an embodiment of a golf tee of the present invention , and fig2 is a cross sectional drawing of the line i - i of the golf tee shown in fig1 . as shown in fig1 , the golf tee 10 according to the present embodiment is a circular truncated cone having a hollow structure . the golf tee 10 has a top end portion 5 and a bottom end portion 6 and is used by placing the bottom end portion 6 on the ground surface and placing a golf ball on the top end portion 5 . as shown in fig1 , the circular truncated conical golf tee 10 has supporting shafts 1 extending from the bottom end portion 6 toward the top end portion 5 . as shown in fig2 , six supporting shafts 1 are disposed at approximately equal intervals . in addition , sidewall portions 2 thinner than the supporting shafts 1 are formed between the supporting shafts 1 , respectively . the sidewall portion 2 is composed of a member that is excellent in the shape restoring property and is arched between the supporting shafts 1 so that the plane of the golf tee 10 cut in the direction ( hereinafter , referred to as “ circumferential direction ”) that is perpendicular to the longitudinal direction thereof is circular . in addition , as shown in fig1 , a plurality of vent holes 3 are provided in the sidewall portions 2 . the vent holes 3 have elliptical shapes and are provided at approximately equal intervals so that the closer they get to the top end portion 5 from the bottom end portion 6 , the larger the areas of the vent holes 3 . furthermore , a plurality of the vent holes 3 are also provided in the circumferential direction of the golf tee 10 , and the vent holes 3 provided in the same circumferential direction have the same shape . in other words , the vent holes 3 provided in the same circumferential direction have the same shape ; however , the vent holes 3 provided in the same direction directed from the bottom end portion 6 to the top end portion 5 of the golf tee 10 do not have the same shape , and the areas thereof are gradually increased as they get close to the top end portion 5 . the bottom end portion 6 of the above described golf tee 10 comprises bottom end projecting portions 6 a extending in the longitudinal direction and formed by the supporting shafts 1 and notched portions 6 b formed by angularly notching the lower ends of the sidewall portions 2 . on the other hand , the top end portion 5 of the above described golf tee 10 comprises top end projecting portions 5 a extending in the longitudinal direction and formed by the supporting shafts 1 and the sidewall portions 2 between the mutually adjacent vent holes 3 and parts 5 b of the vent holes 3 . therefore , in the above described golf tee 10 , the bottom end projecting portions 6 a contact the ground surface , and the top projecting portions 5 a contact a golf ball . the weight of the golf tee 10 according to the present embodiment is reduced as a result of reducing the thickness of the sidewall portions 2 and providing the vent holes 3 , and support stability of the golf tee 10 is achieved as a result of providing the supporting shafts 1 thicker than the sidewall portions 2 . note that , since the weight of the above described golf tee 10 is reduced , the cost of the raw materials of the golf tee 10 is also reduced . the thickness of the supporting shaft 1 in this case is preferably 0 . 4 to 1 . 0 mm from the viewpoints of the support stability of a golf ball and weight reduction of the golf tee . the thickness of the sidewall portion 2 is preferably 0 . 2 to 0 . 9 mm from the viewpoints of the shape restoring property and weight reduction of the golf the above described golf tee 10 is a circular truncated cone having the hollow structure . therefore , when the golf tee of the present invention undergoes accompanying flight , the air resistance that the outer surface of the golf tee receives is large . the above described golf tee 10 has the center of gravity at a lower position compared with cylindrical ones since it is circular truncated cone . therefore , the golf tee can be prevented from being fallen down by the influence of a wind or the like . the above described golf tee 10 has the vent holes 3 in the sidewall portions 2 ; therefore , even when a wind or the like blows , it is not readily affected by the wind or the like since the wind passes through the vent holes 3 . furthermore , when the above described golf tee 10 is placed on the ground surface , winds more readily pass through at an upper part of the golf tee 10 since the areas of the upper vent holes 3 of the golf tee are large . therefore , the above described golf tee 10 is particularly excellent in the support stability . regarding the above described golf tee 10 , when the golf tee 10 is placed on the ground surface , the angle formed by the supporting shafts and sidewall portions of the golf tee and the ground surface is preferably 60 to 89 degrees . when the angle is less than 60 degrees , upon impact , a golf club readily hits the golf tee 10 before the golf ball compared with the case in which the angle is within the above described range . meanwhile , when the angle exceeds 89 degrees , it readily falls down due to the influence of winds or the like compared with the case in which the angle is within the above described range . the above described golf tee 10 has the shape restoring property . therefore , even when shock is applied to the golf tee together with the golf ball upon impact , damage of the golf tee is suppressed . the golf tee of the present invention has a light weight and is also good in resilience ; therefore , loss of impact energy due to the golf tee 10 is suppressed . moreover , since the above described golf tee 10 has the shape restoring property , for example , it can be folded and housed in a pocket or the like . at that point , it can be prevented from falling down from the pocket since it achieves a restored state . such shape restoring property can be achieved by manufacturing the golf tee 10 by a thermoplastic resin and forming the sidewall portions to be thin as described above . no particular limitation is imposed on the above described thermoplastic resin ; however , from the viewpoint of recycling , for example , polyolefins such as polyethylene and polypropylene and elastomers such as rubber and synthetic rubber are preferably used . in this case , the golf tee excellent in the shape restoring property is obtained . when the above described golf tee 10 is to be disposed of , the golf tee that is to be disposed of is melted and formed again , thereby using it as a golf tee again . in this case , a golf tee having more satisfactory flexibility and excellent in resilience can be provided . when an environmental aspect is taken into consideration , the above described thermoplastic resin is preferably a biodegradable resin manufactured from a starch ( corn starch ), cellulose , carrageenan , chitin / chitosan , etc . in the biodegradable resin , wood powder , paper fibers , etc . may be mixed . the golf tee 10 according to the present embodiment is excellent in support stability and can prevent accompanying flight of the golf tee as much as possible since it has the above described configuration . therefore , the position of tee up can be caused to be at a desired height . more specifically , when the position of tee up is desired to be low , the golf tee can be cut at the position of the golf tee 10 so that it is cut by the plane perpendicular to the longitude direction of the golf tee . in the above described golf tee 10 , the vent holes 3 are provided at approximately equal intervals in the longitudinal direction . therefore , when the golf tee 10 is to be cut , the vent holes 3 may be used as measures of the cut position in the height direction . as a result , when the heights of a plurality of golf tees 10 are desired to be adjusted , the golf tees 10 can be cut by using the position of a predetermined vent hole 3 as a measure ; therefore , variation of height among the golf tees 10 is reduced . in the above described golf tee 10 , the vent holes 3 provided in the circumferential direction have the same shape ; therefore , when the golf tee 10 is to be cut , they can be used as measures of the cut position in the lateral direction ( horizontal direction ). more specifically , when the positions of the above described vent holes 3 are used as measures to cut it , it can be readily cut by the plane perpendicular to the longitudinal direction of the golf tee . in this case , it is preferred to cut by the plane crossing the center of each of the vent holes . as a result , the vent holes of the top end portions 5 of the golf tee 10 have the same shape . more specifically , it is cut by the plane crossing the center of the vent holes 3 having an elliptical shape ; therefore , each of the parts 5 b of the vent holes 3 constituting the top end portion 5 has a u - shape . therefore , when a golf ball is to be placed on the above described golf tee 10 , the golf ball can be stabilized more . in the above described golf tee 10 , a mark for cutting the vent hole 3 is preferably provided in the periphery of the vent hole 3 . when the mark is provided , it can be readily cut by the plane perpendicular to the longitudinal direction of the golf tee by cutting it along the mark . fig3 is a perspective view schematically showing the state in which tee up is carried out by using the golf tee according to the present embodiment . as shown in fig3 , the golf tee 10 according to the present embodiment is placed on a ground surface 100 so that the bottom end portion 6 side is at the ground surface 100 , and a golf ball 50 is placed above the top end portion 5 of the golf tee 10 . in the golf tee 10 according to the present embodiment , the bottom end projecting portions 6 a are provided in the bottom end portion 6 as described above . therefore , when the golf tee 10 is placed on the ground surface 100 , the bottom end projecting portions 6 a are in contact with the ground surface 100 . consequently , space is generated between the ground surface 100 and the bottom end portion 6 of the golf tee 10 therefore , even when the ground surface 100 has irregularities , when obstacles such as pebbles are present , or when a lawn , etc . is grown , the golf tee 10 can be placed on the ground surface 100 by avoiding them . moreover , even when the golf ball 50 is placed on the top end portion 5 a , the above described golf tee 10 can maintain the shape since the golf ball 50 is supported by the supporting shafts 1 which are thicker than the sidewall portions 2 . thus , the above described golf tee 10 is excellent in the support stability . in the above described golf tee 10 , the top end projecting portions 5 a are provided in the top end portion 5 as described above . therefore , when the golf ball 50 is placed on the top end portion 5 of the golf tee 10 , the top end projecting portions 5 a are in contact with the golf ball 50 . as a result , parts of the top end portions 5 a of the golf tee 10 and the golf ball are caused to be in a floating state ; therefore , loss of impact energy upon impact can be satisfactorily suppressed . fig4 ( a ) is an explanatory drawing for explaining influence of winds against a circular truncated conical golf tee having no vent holes , and fig4 ( b ) is an explanatory drawing for explaining influence of winds against the golf tee according to the present embodiment . as shown in fig4 ( a ), when the circular truncated cone golf tee 11 having no vent holes is placed on the ground surface , and winds w are caused to blow against the golf tee 11 from a predetermined direction , the golf tee 11 readily falls down in the direction of an arrow a when particularly strong winds blow against an upper part of the golf tee 11 although the golf tee 11 has stability since it is circular truncated conical . on the other hand , as shown in fig4 ( b ), when the golf tee 10 according to the present embodiment is similarly placed on the ground surface , and the winds w are caused to blow against the golf tee 10 from a predetermined direction , the winds w pass through the vent holes 3 since the golf tee 10 has the vent holes 3 . particularly , in the above described golf tee 10 , the closer the vent holes 3 to the top , the larger the vent holes 3 ; therefore , even when particularly strong winds blow against upper part of the golf tee 10 , fall down of the golf tee 10 can be prevented . fig5 ( a ) and ( b ) are front views for explaining a method of cutting the golf tee according to the present embodiment . when the golf tee 10 according to the present embodiment is desired to have a desired height , the golf tee 10 according to the present embodiment can be cut at an arbitrary height . more specifically , when the golf tee 10 having a predetermined height l 1 is cut by , for example , a line ii - ii as shown in fig5 ( a ), a golf tee 12 having a desired height l 2 shown in fig5 ( b ) can be obtained . fig6 ( a ) and ( b ) are cross sectional drawings for explaining the shape restoring property of the golf tee according to the present embodiment . as shown in fig6 ( a ), for example when both sides of the golf tee 10 according to the present embodiment are pressed by fingers , the golf tee 10 can be readily deformed . then , when the above described golf tee 10 is released from pressing , the deformed golf tee 10 as shown in fig6 ( b ) is restored to the original state . fig7 is a front view for explaining the state in which the golf tees according to the present embodiment are superimposed . as shown in fig7 , the golf tee 10 according to the present embodiment is a circular truncated cone having a hollow structure ; therefore , the plurality of golf tees 10 can be superimposed in the longitudinal direction of the golf tees 10 . as a result , the superimposed plurality of golf tees 10 can be carried and stored at the same time . the golf tee 10 according to the present embodiment is manufactured by melting a predetermined thermoplastic resin , pouring it to a mold having the shape of the golf tee 10 , and cooling it . a preferred embodiment of the present invention has been described above ; however , the present invention is not limited to the above described embodiment . for example , in the above described embodiment , the number of the supporting shafts 1 of the golf tee 10 is six ; however , no particular limitation is imposed on the number of the supporting shafts 1 as long as it is plural . if the number of the supporting shafts is less than three , support stability is tend to be lowered compared with the case in which the number of the supporting shafts is within the above described range ; and , if the number of the supporting shafts exceeds ten , accompanying flight of the golf tee 10 cannot be satisfactorily prevented since the weight of the golf tee 10 is increased compared with the case in which the number of the supporting shafts is within the above described range . fig8 ( a ) and ( b ) are cross sectional drawings schematically showing golf tees according to other embodiments . as shown in fig8 ( a ), the golf tee 13 has four supporting shafts 1 which are disposed at approximately equal intervals . in addition , the sidewall portions 2 thinner than the supporting shafts 1 are formed between the supporting shafts 1 , respectively . on the other hand , as shown in fig8 ( b ), the golf tee 14 has eight supporting shafts 1 which are disposed at approximately equal intervals . in addition , the sidewall portions 2 thinner than the supporting shafts 1 are formed between the supporting shafts 1 , respectively . in the above described embodiments , the vent hole 3 has an elliptical shape ; however , it may have , for example , a circular or polygonal shape . the vent holes are provided so that the closer they get to the top end portion 5 from the bottom end portion 6 , the larger the areas of the vent holes 3 ; however , the areas of the vent holes 3 may be the same , and they are not required to have constant areas . the vent holes 3 provided in the same circumferential direction have the same shape ; however , they may be different . fig9 ( a ), ( b ), ( c ), ( d ), and ( e ) are front views schematically showing golf tees according to other embodiments . all of a plurality of vent holes 3 a of the golf tee 15 may be rectangular as shown in fig9 ( a ), a plurality of vent holes 3 b of the golf tee 16 may have the same area and the number of the vent holes may be increased as shown in fig9 ( b ), or the areas of vent holes 3 c of the golf tee 17 may be varied as shown in fig9 ( c ). vent holes 3 d and 3 e of the golf tees 21 and 22 may be provided respectively between mutually adjacent supporting shafts in the circumferential direction as shown in fig9 ( d ) and ( e ), the shape of the vent hole 3 d of the golf tee 21 may be oblong as shown in fig9 ( d ), and the shape of the vent holes 3 e of the golf tee 22 may be a laterally - elongated elliptical shape as shown in fig9 ( e ). note that , the golf tees of fig9 ( d ) and ( e ) are set to have lower heights than that of fig9 ( a ), ( b ), and ( c ). in the above described embodiments , the vent holes 3 are provided from the bottom end portion 6 to the top end portion 5 at approximately equal intervals ; however , no limitation is imposed on by this . note that , the same also applies to the intervals of the vent holes 3 provided in the circumferential direction . furthermore , in the above described embodiments , the vent holes 3 are arranged from the bottom end portion 6 toward the top end portion 5 , and the vent holes 3 are provided also in the circumferential direction of the golf tee 10 ; however , the vent holes 3 may be arranged merely in the direction from the bottom end portion 6 toward the top end portion 5 , or the vent holes 3 may be provided merely in the circumferential direction of the golf tee 10 . in the above described embodiments , the notched portion 6 b provided in the bottom end portion 6 of the golf tee 10 has an angular shape ; however , no limitation is imposed on it , and it may be semicircular , arched , triangular , rectangular , etc . fig1 ( a ), ( b ), and ( c ) are front views schematically showing bottom end portions of golf tees according to other embodiments . a notched portion 6 c of the bottom end portion of the golf tee 18 may be semicircular as shown in fig1 ( a ), a notched portion 6 d of the bottom end portion of the golf tee 19 may be triangular as shown in fig1 ( b ), and a notched portion 6 e of the bottom end portion of the golf tee 18 may be rectangular as shown in fig1 ( c ). in the above described embodiment , the mark is provided on the golf tee 10 ; however , it may not be provided . according to the present invention , they can be utilized as golf tees which are excellent in support stability and capable of preventing accompanying flight of the golf tees as much as possible .
a golf tee with excellent support stability is provided . the golf tee is capable of preventing itself from being driven together with a golf ball . the golf tee is a truncated conical golf tee having a hollow structure with a lower end placed on the ground surface and an upper end on which a golf ball is placed . the golf tee has shape restoration properties . the golf tee has a plurality of columns extending from the lower end toward the upper end , sidewalls thinner than the column formed between respective columns , and a plurality of vents provided in each of the sidewalls .