a stress concentrator feature on the shaft of a golf tee can be defined as an area of the tee shaft where the shaft strength has a local minimum . that is , on either side of the location of the stress concentrator feature on the shaft , the strength of the shaft is greater than the strength of the shaft at the location of the stress concentrator feature . in the preferred embodiment , the shaft strength is reduced over a relatively small section of the shaft length . the most straightforward method to reduce shaft strength is to reduce the shaft diameter . the preferred embodiment has a small section of shaft with reduced diameter , which in effect forms a notch in the shaft . the notch acts as a stress concentrator , which focuses the energy input from the club head to the location of the stress concentrator feature . in order to act reasonably as a stress concentrator , the diameter ( or thickness ) of the tee shaft at the location of the local minimum should be at least 10 % smaller than the nominal diameter of the shaft in the local region around the stress concentrator . the preferred embodiments have a local minimum in the shaft diameter that is 40 % smaller than the nominal shaft diameter . however , it should be noted that there is no limitation on the required percentage difference in shaft diameter at the local minimum compared to the nominal shaft diameter . different ratios may be desirable for different nominal tee shaft diameters or with tees made of different materials . most of the discussion here focuses on tees made of wood , which are made on high - speed lathes . this manufacturing process results in tees that have a cylindrical geometry , and are circularly symmetric . the invention is not however limited to such geometries . a stress concentrator feature could be added to a tee with a shaft that had a square or rectangular cross section , for example . such a tee could be made using a different manufacturing process , such as injection molding of a polymer material . a stress concentrator feature also does not need to extend around the entire perimeter of the tee shaft . an effective stress concentrator feature could exist on only one side of a tee shaft , or on opposite sides of the shaft ( or extend over only a portion of the circumference of a round shaft ). for example , a second operation could be added where a traditional tee is placed in a press to form notches on opposite sides of the tee shaft . drilling a small hole , either partially or completely through the tee shaft , can also create a stress concentrator feature . such a hole would weaken the shaft at the location of the hole . the invention is not limited in any way in the materials used to form the tee , the geometry of the tee shaft ( cross section shape or thickness ), or the geometry of the stress concentrator feature and the extent to which it extends around the perimeter of or through the tee shaft . all that is required is a feature that creates a local minimum in the strength of the tee shaft . a tee with a stress concentrator ( formed by a notch ) in the shaft is straightforward to manufacture . since traditional wood tees are simple turnings , changing the diameter over a section of the shaft can be accomplished by changing the geometry of the tool used to make the turning . there is no increase in manufacturing time or cost required to accomplish this . no secondary operations are needed to form the stress concentrator in the shaft . a stress concentrator feature can also easily be incorporated in the tooling for a molded tee without affecting the cost of the part . no increase in material costs or machine cycle times would be needed . fig2 a shows a cross section of the preferred embodiment of the new tee design . tee 200 is similar to prior art tee 100 shown in fig1 except for stress concentrator 40 in shaft 1 . holes or other geometries that can form stress concentrators can be accomplished without additional costs when certain manufacturing methods are used ( holes can be done easily in injection molding , for example ) or with slight cost increases using secondary operations ( such as drilling a hole in a formed tee ). tee 500 in fig5 shows hole 80 drilled through the shaft 10 of tee 500 , where hole 80 forms a local minimum in perpendicular shaft strength at the location of the hole . in use , the new golf tee 200 is inserted into the ground until the portion of shaft 10 with reduced strength ( stress concentrator feature 40 ) is approximately flush with the ground . when the club head contacts the golf ball and tee 200 , shaft 10 of tee 200 will break at the location of stress concentrator feature 40 . furthermore , by locating this point flush with the ground , the moment arm that is formed between the location where the club head impacts top 30 of tee 200 and the stress concentrator feature 40 maximizes the force applied at stress concentrator feature 40 , for a fixed energy input from the club head . when the club head applies a force to the top of tee 200 perpendicular to the axis of tee shaft 10 , tee shaft 10 will break with a much smaller applied force than would a traditional tee . the accompanying reduction in club head velocity that occurs when the tee 200 breaks will be significantly less than the reduction that occurs when a traditional tee is used . in order for tee 200 to function properly , the club head must contact tee 200 somewhere between the location of the stress concentrator 40 and the top of tee 30 . if the club head contacts tee 200 between the location of stress concentrator 40 and the ground , then tee 200 will break along shaft 10 below stress concentrator 40 , and the tee will absorb the same energy ( or momentum ) as a traditional tee . this is the reason why the preferred embodiment locates stress concentrator 40 a distance below the top of tee 30 so that stress concentrator 40 will be approximately flush with the ground when top of tee 30 is the desired height above the ground . note that it is also possible to insert tee 200 farther into the ground ( so that stress concentrator 40 is slightly below the surface of the ground ) and still have it function correctly . the amount stress concentrator 40 can be pushed past the ground surface and still have the tee function correctly depends primarily on the characteristics of the ground . the softer the ground , the farther tee 200 can be inserted and still work effectively . tee 200 retains sufficient strength to resist breaking when a force is applied to top 30 of tee 200 , parallel to the tee shaft 10 axis . this is required in order to be able to insert the tee into the ground . it has been determined that the diameter of traditional tees provides a column that can withstand much greater compression loading than is needed in order to insert a tee into the ground . reducing the diameter of a portion of the shaft as required by the current invention can therefore be done while still maintaining sufficient strength to withstand the compression loads typically encountered . the preferred embodiment locally reduces the diameter of shaft 10 of tee 200 by approximately 40 % to form the stress concentrator feature 40 . shaft 10 of tee 200 in the preferred embodiment has a nominal diameter of 0 . 19 ″, and the diameter at the location of the stress concentrator feature 40 reduces to 0 . 11 ″. note that the invention is not in any way limited to these dimensions . the invention only requires that there be a section of the shaft with a locally reduced strength compared to the rest of the shaft . stress concentrator 40 in shaft 10 of fig2 a is shown with sharp corners . sharp corners increase the stress concentration that occurs , by reducing the area over which the input force is distributed . it may be desirable to reduce the amount of stress concentration for a given shaft strength ( a given diameter or thickness ) to improve the manufacturing yields of the device . the radiuses of the edges of stress concentrator 40 determine the areas over which stress is concentrated . a very small radius results in very high levels of local stress , and could adversely impact manufacturability of the device . a slight increase in the radius can be used if desired to accomplish a reduction in stress concentration for a given reduction in shaft strength . tee 201 is shown in fig2 b with a radiused stress concentrator . joint 41 of stress concentrator 40 is the most critical to radius to reduce stress concentration if needed for manufacturability . the preferred embodiment uses a radius of 0 . 015 ″ for joint 41 of stress concentrator 40 . it should be noted that the invention is not limited to the use of any particular radius . the depth of the notch and the dimension of the radius in joint 41 can both be varied to achieve different mechanical characteristics . the invention is not limited in any way in the combination of shaft diameter and stress concentrator radius used . stress concentrator 40 in shaft 10 ( of tees 200 and 201 ) should be located a distance below top of tee 30 so that top of tee 30 is the desired height above the ground when the tee is inserted in the ground ( to the point where stress concentrator 40 is approximately flush with the ground ). the preferred embodiments locate stress concentrator 40 approximately 1 . 0 ″ below top 30 , which is a desirable distance for use with a typical driver . it should be understood however that the invention is not in any way limited to this dimension . in fact , the preferred distance between stress concentrator 40 and top 30 will be smaller for a tee shot with an iron club ( or a fairway wood ) than a tee shot with a driver . in the case of a tee shot with an iron club , stress concentrator 40 will preferably be located approximately 0 . 30 ″ below top of tee 30 . again , it should be noted that the invention is not in any way limited to locating the stress concentrator at any of the above - identified distances away from the top of the tee . the use of distances other than those identified above will still result in a tee with reduced momentum absorption compared to traditional tees . it is also possible to construct a tee with more than one section of the shaft with reduced strength ( or more than one stress concentrator feature ). the invention is not limited in the number of stress concentrators contained in the shaft . an example embodiment is shown in fig3 where tee 300 contains two stress concentrators in shaft 10 . stress concentrator 40 in shaft 10 of tee 300 is located a distance from top 30 of tee 300 selected to be optimum when a driver is used for a tee shot , and stress concentrator 50 in shaft 10 of tee 300 is located a distance from top 30 of tee 300 selected to be optimum when an iron is used for a tee shot . tee 400 in fig4 shows another alternative embodiment of the new invention . the nominal diameter of shaft 10 on either side of stress concentrator feature 40 is no longer the same , as was shown in fig2 a , 2b , and 3 . the nominal diameter of shaft section 70 , which is the section between top 30 and stress concentrator feature 40 of tee 400 is smaller than the nominal diameter of shaft section 60 , which is the section between tip 20 and stress concentrator feature 40 of tee 400 . there is still a local minimum shown in the shaft diameter that forms stress concentrator 40 . this alternative embodiment allows the stress concentrator feature to continue to function , regardless of the depth tee 400 is inserted into the ground . tee 400 can now be inserted into the ground past the point where stress concentrator 40 would be flush with the surface of the ground , yet still function as intended . only section 60 of tee shaft 10 will be held in place by the ground . since section 60 has a larger diameter than section 70 , section 70 will not be held firmly in place by the ground , even if tee 400 is inserted so that stress concentrator 40 is located a significant distance below the ground surface . input force will still be concentrated at stress concentrator 40 , and the tee will still break at this point . this design can effectively be used for a driver or an iron shot without the need for multiple tees with different distances between the top of the tee and the location of the stress concentrator , or tees with multiple stress concentrators . this design does not require the tee to be fully inserted , pulled out to a desired height and then rocked forward as required by one prior art tee . tee 400 will be held firmly in place in the ground while still providing its driving distance improvement . the preferred embodiment shown in fig4 uses a diameter for shaft section 60 of 0 . 20 ″, a diameter of 0 . 15 ″ for section 70 , and a diameter at joint 41 of stress concentrator 40 of 0 . 1 ″. stress concentrator 40 is located 1 . 0 ″ from the top of the tee ( the same as the distance identified earlier for tees 200 and 201 , for use with a driver ). it should be noted that this embodiment is not limited in any way in the diameters ( or thickness ) used for the various shaft sections , or in the location of stress concentrator 40 . the dimensions given here are representative , and have been shown to work well . they are not the only dimensions that will work , and the invention should not be construed to be in any way limited to use of only these dimensions . the key elements of this embodiment are : 1 ) use of a stress concentrator feature located at a point along the shaft of a tee , and 2 ) a first section of the tee shaft below the stress concentrator feature that has a first diameter or thickness , a second section of the tee shaft above the location of the stress concentration feature that has a second diameter or thickness , where the diameter or thickness of this second section of tee shaft is less than ( or equal to , as described in previous embodiments ) the diameter or thickness of the first section of tee shaft . other embodiments will occur to those skilled in the art and are within the following claims :
a new golf tee that increases the distance obtained on a drive is described . the tee increases driving distance by minimizing the energy absorbed by the tee when it is struck by the golf club . by absorbing less energy from the club head , the new tee minimizes the amount club head speed is reduced at impact , which translates into increased driving distance . the new tee also aids the golfer by providing a structure that allows the golfer to easily and consistently determine the amount the tee has been inserted into the ground .