Training Balls with Improved Valve Stems

Abstract

A training ball includes a resilient shell having an outer surface and an inner surface defining an interior chamber therein. Weighted filler material is disposed within the chamber. A valve stem extends radially inwardly from the shell inner surface and into the interior chamber. An opening along the valve stem extending from the interior chamber to the outer surface of the shell, with a valve disposed in the opening. A transition between the valve stem and an inner surface of the outer shell is curved, tapered, or otherwise graduated to reduce stress at the transition such that a widest portion of the transition is at least twice as wide as a narrowest portion of the valve stem. The transition can be curved with a fillet radius of between about 5-15% of the outer diameter of the ball, and/or between about 4-10 mm.

Claims

1. A training ball comprising: an outer shell having an outer surface and an inner surface defining an interior chamber therein, the outer shell having a wall thickness of between about 1-5 mm; a valve stem extending radially inwardly from the shell and into the interior chamber; an opening along the valve stem; a valve disposed within the opening, wherein the training ball is inflatable from an uninflated configuration by introducing air through the valve; a weighted filler material within the chamber; and a transition between the valve stem and the inner surface of the outer shell, the transition being tapered such that a widest portion of the transition is at least twice as wide as a narrowest portion of the valve stem, the transition being curved and having a fillet radius of between about 4-10 mm in the uninflated configuration.

2. (canceled)

3. The training ball of claim 1, wherein the transition is curved and has a fillet radius that is about 5-15% of an outer diameter of the ball.

4. The training ball of claim 1, wherein the widest portion of the transition is between about 25-40 mm.

5. The training ball of claim 1, wherein the valve stem protrudes into the chamber by a length that is between about 15-35% of an outer diameter of the ball.

6. The training ball of claim 1, wherein the valve stem protrudes into the chamber by a length that is between about 10-30 mm.

7. (canceled)

8. (canceled)

9. A training ball comprising: a resilient shell having an outer surface and an inner surface defining an interior chamber therein; a valve stem extending radially inwardly from the shell inner surface and into the interior chamber; and an opening along the valve stem extending from the interior chamber to the outer surface of the shell; a valve disposed within the opening, wherein the training ball is inflatable from an uninflated configuration by introducing air through the valve; a weighted filler material within the interior chamber; and a valve stem insert comprising: a head portion embedded within the outer shell; and a neck portion extending radially inwardly from the head portion, the neck portion embedded within the valve stem; wherein, in the uninflated configuration, the head portion of the valve insert has a curved upper surface having a radius of curvature corresponding to a radius of the shell outer surface; wherein a transition between the valve stem and an inner surface of the outer shell is curved.

10. The training ball of claim 9, wherein the transition between the valve stem and the inner surface has a fillet radius that is about 5-15% of an outer diameter of the ball.

11. The training ball of claim 9, wherein the outermost edge of the transition between the valve stem and the inner surface of the outer shell defines a widest portion of the transition and wherein the widest portion is at least twice as wide as a width at a radially innermost portion of the valve stem.

12. The training ball of claim 9, wherein the valve stem protrudes into the chamber by a length that is between about 15-35% of an outer diameter of the ball.

13. The training ball of claim 9, wherein the valve stem protrudes into the chamber by a length that is between about 10-30 mm.

14. The training ball of claim 9 wherein the valve stem insert is made of a first material and the shell and valve stem are made of a second material, the first material having different material properties from the second material.

15. A valve stem insert for a training ball, comprising: a head portion configured to be embedded within an outer shell of a ball, the head portion having a curved upper surface having a radius of curvature corresponding to a radius of the outer shell of the ball in which the valve stein insert is configured to be embedded; a neck portion extending radially inwardly from the head portion; an aperture extending through the head portion and the neck portion, the aperture configured to receive a valve therein, wherein a junction between a side surface of the neck portion and a lower surface of the head portion is curved, wherein a greatest width of the head portion is at least twice as wide as a width at a lower end of the neck portion in the absence of external forces on the valve stem insert.

16. The valve stem insert of claim 15, wherein the transition between the valve stem and the inner surface has a fillet radius of between about 5-15 mm.

17. (canceled)

18. The valve stem insert of claim 15, wherein a greatest width of the head portion is between about 25-40 mm.

19. The valve stem insert of claim 15, wherein the valve stem has a length from an upper surface of the head portion to a lower end of the neck portion of between about 10-30 mm.

20. (canceled)

21. The training ball of claim 14, wherein the first material is harder than the second material.

22. The training ball of claim 14, wherein the first material is less flexible than the second material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Many aspects of the present disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale. Instead, emphasis is placed on illustrating clearly the principles of the present disclosure.

[0035] FIG. 1 is a cross-sectional view of a prior art weighted training ball.

[0036] FIGS. 2A-2C are detailed views of failed valve stems.

[0037] FIG. 3A is a cross-sectional view of a weighted training ball in accordance with aspects of the present technology.

[0038] FIG. 3B is an enlarged detail view of the valve stem of the weighted training ball shown in FIG. 3A.

[0039] FIG. 3C is a cross-sectional photograph of a portion of a weighted training ball.

[0040] FIGS. 4A-4F are top, top perspective, side, side cross-sectional, bottom, and bottom perspective views, respectively, of a valve stem insert in accordance with aspects of the present technology.

DETAILED DESCRIPTION

[0041] The present technology relates to weighted training balls with improved valve stems and associated systems and methods of manufacturing. Some embodiments of the present technology, for example, are directed to weighted training balls with valve stems having improved durability and resilience. Specific details of several embodiments of the technology are described below with reference to FIGS. 1-4F.

Overview

[0042] In several embodiments described in more detail below, weighted training balls are designed to be hit with a bat or thrown into a wall or net. The ball can be resilient, flexible, and non-burstable under normal operation (i.e., under the forces typically encountered during throwing and hitting). The ball can provide tactile feedback to athletes on how they threw or hit the balls in order to help improve throwing or hitting mechanics. In some embodiments, a variety of balls can be provided with different weights, thereby allowing an athlete to strengthen his arm by use of increasingly heavier training balls.

[0043] The ball includes an outer shell that can be made of a flexible, resilient, and sturdy material to withstand repeated impact without permanent deformation or degradation of the ball. The outer shell encloses an interior chamber that can be partially or completely filled with a weighted filler material such as sand. The amount of weighted filler material can be varied to achieve the desired total ball weight. The ball also includes a valve stem having an opening configured to receive an air valve therein. The air valve allows the ball to be inflated using a standard bicycle pump or other suitable inflation device, and also prevents pressurized air as well as the filler material from escaping the interior chamber of the ball.

[0044] As described in more detail below, the inventors have discovered that, in prior art weighted training balls, a particularly susceptible point of failure is the interior junction or transition between the valve stem and the shell of the ball. During use of the ball (either hitting, being thrown into a wall, or other such use), the repeated impact can cause the valve stem to flex and bend with respect to the outer shell. Additionally, the junction point can have a thinner profile than other portions of the ball, thereby creating a weak point in the overall ball construction. As a result, cracks, tears, and other failures can form at the junction of the valve stem and the outer shell of the ball.

[0045] To provide increased durability, certain embodiments of the present technology provide a weighted training ball having a curved, flared, or tapered valve stem. For example, rather than an acute angle at the junction between the valve stem and the inner surface of the shell, a curved transition can be provided. Additionally, the overall length of the valve stem can be decreased to reduce the overall stress at the junction. These features can decrease the stress concentration at the junction, thereby increasing durability and reducing the risk of failure identified in prior art weighted training balls.

[0046] In some embodiments, the flared valve stem is provided by including a valve stem insert having a preformed shape with some curvature or graduated transition between a head portion and a neck portion. The remainder of the ball (including the outer shell) can then be formed over the valve stem insert. In at least some embodiments, the valve stem insert can be made of a pre-cured material, such that the valve stem insert can retain its shape while the remainder of the ball is formed via liquid molding, injection molding, or other suitable technique.

Example Prior Art Training Ball

[0047] FIG. 1 is a cross-sectional view of a prior art weighted training ball 100. The ball 100 includes an outer shell 101 having an outer surface 103 and an inner surface 105 defining an interior chamber 107 therein. A weighted filler material 109 is disposed within the chamber 107. A valve stem 111 extends from the shell 101 into the interior chamber 107 of the ball 100. The valve stem 111 includes a central opening 113 configured to receive a valve 115 therein. Some prior art training balls also include a valve stem insert that at least partially surrounds the valve 115 and is disposed within the material of the valve stem 111. Such valve stem inserts are generally cylindrical members that that have a substantially uniform width along their length.

[0048] The valve stem 111 and the inner surface 105 of the shell 101 meet at a junction 117. The inventors have discovered that such training balls are prone to failure, particularly at the junction 117. After considerable analysis, the inventors determined that the valve stem 111 creates an immobile area on the surface of the ball 100, resulting in high stress concentrations in the flexible region of the shell 101 around the valve stem 111. Impact of the weighted filler material may also cause micro-tears on the inner surface 105 of the shell, decreasing durability of the ball. Additionally, upon impact, the weighted filler material 109 may strike the valve stem 111, causing it to bend or deflect with respect to the junction 117 of the valve stem 111 and the shell 101. This bending also contributes to mechanical stress at the junction 117. These concentrated stresses can lead to tearing at the junction 117, ultimately leading to separation of the valve stem 111 from the shell 101. This tearing ultimately results in loss of air pressure, release of weighted filler material, and failure of the ball 100.

[0049] The inventors analyzed a range of training balls, including new balls, balls that have been used but are still intact, and failed balls. The new balls were found to have no cracks or tears at the junction 117, while the used but still intact balls had nascent fatigue cracking at the junction 117, and the failed balls had larger tears or complete separation at the junction 117. These results suggest that the route of failure is progressive fatigue cracking of the valve stem at the junction 117. As a result, reinforcement of the junction 117 can reduce cracking from concentrated stresses over the lifetime of the ball.

[0050] FIGS. 2A-2C are detailed views of failed valve stems. The balls in these images have been cut in half and inverted to illustrate the failed valve stems. As shown, at the junction 117 of the valve stem 111 and the inner surface 105 of the shell 101, there are tears, rips, and other such mechanical failures where the valve stem 111 is beginning to separate from the shell 101. With prolonged use, these failures can lead to loss of air pressure within the ball or even complete separation of the valve stem 111 from the shell 101. The failures have been found to occur around the base of the valve stem 111.

Example Training Balls with Improved Valve Stems

[0051] In view of the failure modes identified around the junction in prior art training balls, the inventors have developed weighted training balls with improved valve stems for increased durability and resistance to fatigue cracking at the junction between the valve stem and the outer shell of the ball. As described in more detail below, rather than a sharp junction between the valve stem and the shell, the training balls disclosed herein can include a transition that is curved, tapered, flared, and/or graduated to provide for a more gradual change between the valve stem and the ball, and/or to provide an increased wall thickness at the transition. Additionally, in some embodiments the length of the valve stem can be decreased relative to prior art training balls, which also results in less stress due to deflection and bending of the valve stem with respect to the outer shell.

[0052] FIG. 3A is a cross-sectional view of a weighted training ball 300 with an improved valve stem in accordance with aspects of the present technology. FIG. 3B is an enlarged detail view of the valve stem of the weighted training ball shown in FIG. 3A. FIG. 3C is a photograph of a cross-section of a portion of a weighted training ball that includes the improved valve stem as shown in FIGS. 3A and 3B. Referring to FIGS. 3A-3C together, the weighted training ball 300 includes an outer shell 301 having an outer surface 303 and an inner surface 305 defining an interior chamber 307 therein.

[0053] The outer diameter of the ball 301 can be varied depending on the desired application. In some embodiments, the ball diameter can be between about 50-200 mm. In embodiments involving training balls for baseball, various training balls can be provided with diameters between about 70-110 mm. In specific examples, the training balls can have a diameter of around 74 mm, around 86 mm, and around 105 mm in various embodiments. In other embodiments, the ball diameter can be significantly larger, for example for yoga balls, exercise balls, Pilates balls, basketballs, volleyballs, etc. In still other embodiments, the ball diameter can be smaller than 50 mm. The shell 301 can have a thickness ranging from about 1-5 mm, for example about 2 mm in some embodiments.

[0054] A weighted filler material 309 (such as river sand, iron sand, beads, or other suitable material) is disposed within the chamber 307. The amount and composition of weighted filler material 309 can be selected to achieve the desired overall weight of the ball 300. For example, in some embodiments, training balls can be provided having a range of weights, for example between 50 g to 3000 g or more, with any specific value in between. In some embodiments, the training ball can have a weight of about 100 g, about 150 g, about 225 g, about 450 g, about 1000 g, or about 2000 g.

[0055] A valve stem 311 extends from the shell 301 into the interior chamber 307 of the ball 300. The valve stem 311 includes a central opening 313 configured to receive a valve 315 therein. The valve 315 can be a standard rubber air valve, for example suitable for use with a bicycle pump to increase air pressure within the chamber 307. In some embodiments, the opening 313 can have a diameter of about 4 mm configured to receive a standard rubber air valve. The valve stem 311 can extend radially inwardly into the chamber 307 of the ball 300 by a distance D.sub.1. In various embodiments, the distance D.sub.1 can be between about 15-35% of the outer diameter of the ball 300. In some embodiments, the distance D.sub.1 can be between about 10-30 mm, or between about 15-25 mm. As such, in some embodiments, the distance D1 can be less than about 25 mm, less than about 24 mm, less than about 23 mm, less than about 22 mm, less than about 21 mm, less than about 20 mm, less than about 19 mm, less than about 18 mm, less than about 17 mm, less than about 16 mm, less than about 15 mm, less than about 14 mm, less than about 13 mm, less than about 12 mm, less than about 11 mm, or less than about 10 mm. As noted previously, maintaining a relatively short distance D.sub.1 can increase the durability of the ball by reducing stress due to bending of the valve stem 311 when in use.

[0056] The valve stem 311 and the inner surface 305 of the shell 301 meet at a junction or transition 317. In the illustrated embodiment, the transition 317 is curved to provide a gradual or tapered transition between the valve stem 311 and the inner surface 305 of the shell 301. While the illustrated embodiment shows a uniform curve that can be characterized by a fillet radius R.sub.1, in other embodiments the transition 317 can assume other shapes or configurations. For example, the transition 317 can be a linear taper between a narrower portion of the valve stem 311 and a contact point at the inner surface 305 of the shell 301. In another example, the transition 317 can be concave rather than convex, having an outwardly curved surface extending between a narrower portion of the valve stem 311 and a contact point at the inner surface 305 of the shell 301. In another embodiment, the curved transition may not have a uniform curve such that a single radius of curvature prevails across the curve, but rather the radius of curvature may vary along the transition 317.

[0057] As noted above, in some embodiments, the transition 317 can be curved and characterized by a fillet radius R.sub.1. In various embodiments, the fillet radius R.sub.1 can be between about 5-15% of the outer diameter of the ball 300, between about 6-14%, between about 7-13%, between about 8-12%, between about 9-11%, or about 10% of the outer diameter of the ball 300. In some embodiments, the fillet radius R.sub.1 can be greater than about 5% of the outer diameter of the ball 300, greater than about 6%, greater than about 7%, greater than about 8%, greater than about 9%, greater than about 10%, greater than about 11%, greater than about 12%, greater than about 13%, greater than about 14%, or greater than about 15% of the outer diameter of the ball 300. In some embodiments, the fillet radius R.sub.1 can be less than about 15% of the outer diameter of the ball 300, less than about 14%, less than about 13%, less than about 12%, less than about 11%, less than about 10%, less than about 9%, less than about 8%, less than about 7%, less than about 6%, less than about 5%, less than about 4%, less than about 3%, less than about 2%, or less than about 1% of the outer diameter of the ball 300.

[0058] In some embodiments, the fillet radius R.sub.1 can be between about 4-10 mm, between about 6-9 mm, between about 7-8 mm. In some embodiments, the fillet radius R.sub.1 can be about 5 mm, about 6 mm, about 7 mm, about 8 mm, or about 9 mm. In some embodiments, the fillet radius R.sub.1 can be greater than about 5 mm, greater than about 6 mm, greater than about 7 mm, greater than about 8 mm, greater than about 9 mm, or greater than about 10 mm. In some embodiments, the fillet radius R.sub.1 can be less than about 10 mm, less than about 9 mm, less than about 8 mm, less than about 7 mm, less than about 6 mm, or less than about 5 mm.

[0059] The inner surface 305 of the shell 301 can meet the transition 317 at the portion at which the inner surface 305 begins to diverge inward from its spherical shape. This portion can define the radially outermost edge of the transition 317. The greatest width of the transition 317 can be measured between these opposed portions and characterized by a width D.sub.2. As the transition 317 and the valve stem 311 taper in the radially inward direction, the width of the valve stem 311 decreases. The narrowest portion of the valve stem 311 can be characterized by a width D.sub.3. In the illustrated embodiment, the with D.sub.3 at the narrowest portion is at the radially innermost end of the valve stem 311. However, in other embodiments, other portions of the valve stem 311 may the narrowest portion of the valve stem 311, for example a portion disposed mid-way along the length the valve stem 311 may be the narrowest portion of the valve stem 311.

[0060] In various embodiments, the width D.sub.2 at the widest portion of the valve stem 311 can be between about 25-40 mm, or between about 25-35 mm, or about 28 mm. In some embodiments, the width D.sub.2 can be greater than about 20 mm, greater than about 21 mm, greater than about 22 mm, greater than about 23 mm, greater than about 24 mm, greater than about 25 mm, greater than about 26 mm, greater than about 27 mm, greater than about 28 mm, greater than about 29 mm, greater than about 30 mm, greater than about 31 mm, greater than about 32 mm, greater than about 33 mm, greater than about 34 mm, greater than about 35 mm, greater than about 36 mm, greater than about 37 mm, greater than about 38 mm, greater than about 39 mm, or greater than about 49 mm. In some embodiments, the width D.sub.2 at the widest portion of the valve stem 311 can be between about 3-5 times greater than the width D.sub.3 at the narrowest portion of the valve stem 311. In some embodiments, the width D.sub.2 can be about twice as long as the width D.sub.3, about three times greater than the width D.sub.3, about four times greater, or about five times greater than the width D.sub.3. In some embodiments, the width D.sub.2 can be at least two times greater than the width D.sub.3, at least two times greater, at least three times greater, at least four times greater, or at least 5 times greater than the width D.sub.3.

[0061] The shell 301 can be made of a flexible, resilient, durable material that can withstand repeated impact such as being hit or thrown against a wall. In some embodiments, the shell 301 can be made of a polymer such as a foam flexible polyvinyl chloride (PVC) material containing one or more plasticizers, fillers, or other additives. In some embodiments, the polymer material is substantially devoid of any phthalate plasticizers. In some embodiments, the polymer material is substantially devoid of any calcite filler. Omitting calcite filler can increase the elasticity of the ball and therefore reduce the risk of failure. The particular material properties of the shell 301 can be varied depending on the intended use and desired performance. In some embodiments, the material of the shell 301 can have a Shore A Durometer hardness value of between about 40 and about 55 when newly manufactured.

[0062] As seen in FIGS. 3A and 3B, a valve stem insert 319 is enclosed within the shell 301 and the valve stem 311 of the ball 300. Additional details of the valve stem insert 319 are provided below with respect to FIGS. 4A-4F. With continued reference to FIGS. 3A and 3B, in some embodiments, the ball 300 is made of more than one material, for example a first material for the valve stem insert 319, and a second material for the shell 301 and the radially outer portion of the valve stem 311. The first and second materials can each be resilient, flexible, durable materials such as a smooth PVC polymer material. In some embodiments, the first and second materials can differ in one or more material properties, such as composition, flexibility, elasticity, hardness, melting point, etc. In some embodiments, the second material for the shell 301 and the outer portion of the valve stem 311 is made from a powder, and is present in its liquid form before manufacturing, such that after production the material quality can be described as a foam PVC. The first material for the valve stem insert 319 can be made from solid beads and is pre-cured such that the material properties can be described as a solid but soft and flexible PVC. As described in more detail below, this difference in properties allows the valve stem insert 319 to be pre-formed, and then for the remainder of the ball 300 to be formed via molding of the second material over the valve stem insert 319. This is beneficial because pre-forming the valve stem insert 319 allows for fine control of the contours of the transition 317, which, as noted above, is a point susceptible to failure due to fatigue cracking.

[0063] FIGS. 4A-4F are top, top perspective, side, side cross-sectional, bottom, and bottom perspective views, respectively, of the valve stem insert 319 described above. As noted above and as seen in FIGS. 3A and 3B, the valve stem insert 319 can be enclosed within the ball 300, for example with a portion enclosed within the shell 301 and another portion enclosed within the valve stem 311.

[0064] With respect to FIGS. 4A-4F together, the valve stem insert 319 includes an upper or head portion 321 and a lower or neck portion 323 that extends away from the head portion 321. In use, the head portion 321 is configured to be at least partially received within the shell 301 of the ball 300, while the neck portion 323 is configured to be at least partially received within the valve stem 311 of the ball 300 (as seen in FIGS. 3A and 3B).

[0065] The head portion 321 has an upper surface 325 and a lower surface 327 from which the neck portion 323 extends. The upper surface 325 can be a partially spherical shape, for example having a curved surface characterized by a radius of curvature R.sub.2. In some embodiments, the radius of curvature R.sub.2 of the head portion upper surface 325 can be configured to correspond generally to a radius of the ball 300 in which the valve stem insert 319 is to be placed. For example, the radius of curvature R.sub.2 can be between about 25-100 mm (corresponding to balls having diameters of between about 50-200 mm). In specific embodiments, R.sub.2 can have values of between about 35-55 mm, for example about 37 mm, about 43 mm, or about 52.5 mm (corresponding to balls having outer diameters of about 74 mm, about 86 mm, and about 105 mm, respectively). In some embodiments, the radius of curvature R.sub.2 may be slightly less than the radius of curvature of the outer surface of the ball 300, since the head portion upper surface 325 will be disposed slightly radially inwardly from the outer surface 303 of the shell 301 of the ball 300 (as seen in FIG. 3A).

[0066] The neck portion 323 includes a side surface 329 and a lower surface 331 disposed at a bottom end of the valve stem insert 319. The side surface 329 can assume a partially cylindrical shape surrounding the central opening 313 configured to receive the valve therein. The opening 313 extends through the entirety of the valve stem insert 319, from the head portion upper surface 325 to the neck portion lower surface 331. As noted above, the opening 313 can be configured to receive a rubber air valve or other suitable valve therein. The valve stem insert 319 can be characterized by a length D.sub.4 as measured from the head portion upper surface 325 to the neck portion lower surface 331. This length D.sub.4 in part determines the extent to which the valve stem 311 will protrude into the interior chamber 307 of the ball 300 (FIGS. 3A and 3B). In various embodiments, the length D.sub.4 can be between about 30-60% of the radius of curvature R.sub.2 of the head portion upper surface 325. In some embodiments, the length D.sub.4 can be between about 15-30 mm, or between about 20-25 mm.

[0067] The head portion 321 defines a widest portion of the valve stem insert 319 characterized as the length D.sub.5. This length D.sub.5 can define the diameter across the head portion upper surface 325. The neck portion 323 can be defined by a narrowest portion having a width D.sub.6. In various embodiments, the width D.sub.5 at the widest portion of the valve stem insert 319 can be between about 25-40 mm, or between about 25-35 mm, or about 28 mm. In some embodiments, the width D.sub.5 can be greater than about 20 mm, greater than about 21 mm, greater than about 22 mm, greater than about 23 mm, greater than about 24 mm, greater than about 25 mm, greater than about 26 mm, greater than about 27 mm, greater than about 28 mm, greater than about 29 mm, greater than about 30 mm, greater than about 31 mm, greater than about 32 mm, greater than about 33 mm, greater than about 34 mm, greater than about 35 mm, greater than about 36 mm, greater than about 37 mm, greater than about 38 mm, greater than about 39 mm, or greater than about 49 mm. In some embodiments, the width D.sub.5 at the widest portion of the valve stem insert 319 can be between about 3-5 times longer than the width D.sub.6 at the narrowest portion of the valve stem insert 319. In some embodiments, the width D.sub.5 can be about twice as wide as the width D.sub.6, about three times greater than D.sub.6, about four times greater, or about five times greater. In some embodiments, the width D.sub.5 can be at least two times greater than the width D.sub.6, at least three times greater, at least four times greater, or at least 5 times greater.

[0068] The lower surface 327 of the head portion 321 and the side surface 329 of the neck portion 323 meet at a junction or transition 333. In the illustrated embodiment, the transition 333 is curved to provide a gradual or tapered transition between the neck portion side surface 329 and the head portion lower surface 327. The illustrated embodiment shows a uniform curve that can be characterized by a fillet radius R.sub.3, in other embodiments the transition 333 can assume other shapes or configurations. For example, the transition 333 can be a linear taper between a narrower portion of the neck portion side surface 329 and a contact point at the head portion lower surface 327. In another example, the transition 333 can be concave rather than convex, having an outwardly curved surface extending between a narrower region of the neck portion side surface 329 and a contact point at the head portion lower surface 327. In another embodiment, the curved transition 333 may not have a uniform curve such that a single radius of curvature prevails across the curve, but rather the radius of curvature may vary along the transition 333.

[0069] As noted above, in some embodiments, the transition 333 can be curved and characterized by a fillet radius R.sub.3. The fillet radius R.sub.3 can be between about 10-30% of the radius of curvature R.sub.2 of the head portion upper surface 325, between about 12-28%, between about 14-26%, between about 16-24%, between about 18-22%, or about 20% of R.sub.2. In some embodiments, the fillet radius R.sub.3 can be greater than 10% of R.sub.2, greater than about 12%, greater than about 14%, greater than about 16%, greater than about 18%, greater than about 20%, greater than about 22%, greater than about 24%, greater than about 26%, greater than about 28%, or greater than about 30% of R.sub.2. In some embodiments, the fillet radius R.sub.3 can be less than about 30% of the R.sub.2, less than about 28%, less than about 26%, less than about 24%, less than about 22%, less than about 20%, less than about 18%, less than about 16%, less than about 14%, less than about 12%, less than about 10%, less than about 8%, less than about 6%, less than about 4%, or less than about 2% of R.sub.2.

[0070] In some embodiments, the fillet radius R.sub.3 can be between about 4-10 mm, between about 6-9 mm, between about 7-8 mm. In some embodiments, the fillet radius R.sub.3 can be about 5 mm, about 6 mm, about 7 mm, about 8 mm, or about 9 mm. In some embodiments, the fillet radius R.sub.3 can be greater than about 5 mm, greater than about 6 mm, greater than about 7 mm, greater than about 8 mm, greater than about 9 mm, or greater than about 10 mm. In some embodiments, the fillet radius R.sub.3 can be less than about 10 mm, less than about 9 mm, less than about 8 mm, less than about 7 mm, less than about 6 mm, or less than about 5 mm.

Example Methods of Manufacturing

[0071] The weighted training balls disclosed herein can be made using any suitable manufacturing techniques. One example described below involves molding the ball using a valve stem insert 319 as described in FIGS. 4A-4F. As noted above, in some embodiments the valve stem insert 319 can be made of a first material being softer and pre-cured. The first material can be, for example, a PVC material having plasticizers or other additives such that the material is rubbery and solid at room temperature. In one example, the first material is a phthalate plasticized PVC or an acetyl tributyl citrate plasticized PVC.

[0072] A mold in the form of two hemispherical mold halves can be provided to mold the training ball. One of the two hemispherical mold halves has a rod extending away from the inner concave surface of the mold. The rod can have a diameter corresponding to the diameter of the opening 313 in the valve stem insert 319, for example a diameter of approximately 4 mm in some embodiments. The valve stem insert 319 can be slid over the rod such that the head portion 321 of the valve stem insert 319 faces the inner concave surface of the mold and the rod extends through the opening 313.

[0073] One of the hemispherical mold halves is then filled with a liquefied material such as a second material. The second material can be, for example, a thermosetting resin such as PVC material having plasticizers or other additives and configured such that the second material is liquid at room temperature until it is baked in an oven to cure. The second material can be heated to a temperature such that it begins to harden and cure. The valve stem insert 319 is pre-cured, so it remains solid during the heating process. In one example, the second material can be tributyl citrate plasticized PVC. In some embodiments, the first and second materials can differ in one or more material properties, such as composition, flexibility, elasticity, hardness, melting point, etc. For example, the first material of the valve stem insert may be harder or softer than the second material, the first material may have a higher or lower melting point than the second material, the first material may be more flexible or less flexible than the second material, etc. In some embodiments, the first material has different plasticizers than the second material, or a different concentration of plasticizers or other constituent elements than the second material.

[0074] After one mold half is filled with the second material, the hemispherical mold halves are joined and the combined halves are placed into an oven or other heat source to cure. As the second material cures in the oven, the molds are rotated and inverted such that the second material coats the inner surface of the molds. In coating the inner surfaces of the hemispherical mold halves, the valve stem insert 319, which is made of the first material, can be partially or completely covered by the second material. After curing, the mold is removed and allowed to cool. The hemispherical mold halves are then separated, and the ball can be removed.

[0075] The resulting ball may then be filled with weighted filler material and a rubber valve can be inserted into the aperture 313 defined by the valve stem insert 319 and the rod used in the molding process. In some embodiments, additional processing can be performed on the training ball, for example additional printing, coating, sealing, or other suitable post-processing steps.

[0076] As will be appreciated by one of ordinary skill in the art, the above-described method is only one technique for manufacturing a sand-filled weighted training ball as disclosed herein, and any number of other methods can be employed.

CONCLUSION

[0077] Although many of the embodiments are described above with respect to systems, devices, and methods for providing training balls with improved durability and performance, the technology is applicable to other applications and/or other approaches, such as training balls for other sports beyond baseball or softball (e.g., basketballs, soccer balls, footballs, Pilates balls, yoga balls, exercise balls, or any other ball), or for other inflatable objects that can benefit from a reinforced valve stem. Moreover, other embodiments in addition to those described herein are within the scope of the technology. Additionally, several other embodiments of the technology can have different configurations, components, or procedures than those described herein. A person of ordinary skill in the art, therefore, will accordingly understand that the technology can have other embodiments with additional elements, or the technology can have other embodiments without several of the features shown and described above with reference to FIGS. 1-4F.

[0078] The above detailed descriptions of embodiments of the technology are not intended to be exhaustive or to limit the technology to the precise form disclosed above. Where the context permits, singular or plural terms may also include the plural or singular term, respectively. Although specific embodiments of, and examples for, the technology are described above for illustrative purposes, various equivalent modifications are possible within the scope of the technology, as those skilled in the relevant art will recognize. For example, while steps are presented in a given order, alternative embodiments may perform steps in a different order. The various embodiments described herein may also be combined to provide further embodiments.

[0079] Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, to between the upper and lower limits of that range is also specifically disclosed. Each smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in that stated range is encompassed within the disclosure. The upper and lower limits of these smaller ranges may independently be included or excluded in the range, and each range where either, neither or both limits are included in the smaller ranges is also encompassed within the disclosure, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the disclosure.

[0080] Moreover, unless the word or is expressly limited to mean only a single item exclusive from the other items in reference to a list of two or more items, then the use of or in such a list is to be interpreted as including (a) any single item in the list, (b) all of the items in the list, or (c) any combination of the items in the list. Additionally, the term comprising is used throughout to mean including at least the recited feature(s) such that any greater number of the same feature and/or additional types of other features are not precluded. It will also be appreciated that specific embodiments have been described herein for purposes of illustration, but that various modifications may be made without deviating from the technology. Further, while advantages associated with certain embodiments of the technology have been described in the context of those embodiments, other embodiments may also exhibit such advantages, and not all embodiments need necessarily exhibit such advantages to fall within the scope of the technology. Accordingly, the disclosure and associated technology can encompass other embodiments not expressly shown or described herein.