Patent Application
20060019779
The present invention relates generally to ball bats. In particular, the present invention relates to a ball bat formed of conventional carbon steel, alloy steel or high strength low alloy steel wherein at least portion of such steel used to form the bat is strengthened through carburization, nitriding, or boriding.
Ball bats, such as baseball and softball bats, are well known. In recent years, metallic bats including a tubular handle portion and a tubular hitting portion have emerged providing improved performance and improved durability over crack-prone wooden bats. The most common tubular bat is the aluminum single-wall tubular bat. Such bats have the advantage of a generally good impact response, meaning that the bat effectively transfers power to a batted ball.
Generally speaking, bat performance is a function of the weight of the bat, the size, and the impact response of the bat. The durability of a bat relates, at least in part, to its ability to resist denting and depends on the strength and stiffness of the tubular bat frame. While recent innovations in bat technology have increased performance and durability, most new bat designs typically improve performance or durability at the expense of the other because of competing design factors. For example, an attempt to increase the durability of the bat often produces an adverse effect on the bat's performance.
The incorporation of these advances and the use of additional materials, such as, other aluminum alloys, titanium alloys and composite materials have resulted in a large variety of well-performing ball bats. Despite such advances in ball bat design and materials, a continuing need exists to further improve the performance, durability and feel of existing bats.
One drawback of recent ball bats formed of aluminum, titanium or composite materials is their cost. Aluminum, titanium and composite materials generally have a high material cost. For example, aluminum can cost up to ten times the price of conventional steel, and titanium is significantly more expensive than aluminum. Further, many metals, such as titanium, are difficult to work with, having very poor workability. Also, the manufacturing costs for composite materials are also relatively high. Still further, the availability of many metals, including titanium, is often variable, making obtaining a consistent supply of material at a generally consistent price difficult. For these reasons, the use of titanium is fairly limited in current bat designs. Aluminum is most commonly used in non-wooden ball bats because of its low material density (lightweight) and its high workability. However, the tensile strength aluminum is generally approximately 85 ksi, which is significantly lower than many other metals. In order to provide sufficient strength and durability, aluminum bats are often formed with a wall thickness as high as 0.110 inches.
Although conventional steel is significantly cheaper and tougher than aluminum or titanium and has relatively high workability, conventional steel is typically not used to form ball bats due to its relatively high weight or density. Further, although conventional steel, after heat treating, has a tensile strength (typically approximately 150 ksi or less), which is greater than aluminum, the wall thickness required to produce a bat formed of conventional steel that is sufficiently durable for competitive play results in a bat that is too heavy for most ball players. Use of heavy materials can negatively affect a player's bat speed and the moment of inertia (“MOI”) of the bat. High quality steels, such as maraging steels, provide a higher tensile strength. However, such high quality steels, are very expensive and difficult to work with, resulting in high material and manufacturing costs.
Thus, a continuing need exists for a ball bat that provides improved performance and high durability at a reasonable cost. It would be advantageous to provide a high performance ball bat that meets all the requirements of conventional play including weight, without excessive material costs or excessive manufacturing costs. What is needed is a ball bat that incorporates and improves on the beneficial material properties and qualities of steel while addressing potentially negative characteristics related to the use of steel, including the weight distribution and MOI of the bat.
The present invention provides a ball bat configured for impacting a ball. The bat includes a substantially tubular frame having a handle portion and a hitting portion. The handle portion is formed of a non-steel material. The hitting portion is formed separately from, and coupled to, the handle portion. The hitting portion is formed of a steel and has an inner surface and an outer surface. At least a portion of hitting portion is carburized forming a carburized layer.
According to a principal aspect of the invention, a bat has a longitudinal axis and is capable of being tested in a ring load testing device having first and second platens. The bat includes a substantially tubular frame having a handle portion and a primary hitting portion. The hitting portion is formed of a conventional carbon steel or a high strength, low alloy steel. The hitting portion has a central region with a wall thickness within the range of 0.040 to 0.065 inches. The hitting portion has a yield strength within the range of 200 and 300 ksi, when measured in the ring load testing device. A ring of a predetermined length is removed from the central region of the hitting portion and is placed between the first and second platens of the ring load testing device. The first platen applies a load to an outer circumferential surface of the ring in a direction that is substantially perpendicular to the longitudinal axis, from which load deflection data is obtained.
According to another principal aspect of the invention, a ball bat includes a substantially tubular frame having a handle portion and a primary hitting portion. The hitting portion is formed of a steel. The hitting portion has a first wall thickness, an inner surface and an outer surface. At least a portion of hitting portion includes a high performance layer. The high performance layer has a hardness within the range of 80 to 93 on a 15N Rockwell Hardness Scale. The high performance layer has a second thickness that is sized to be at least 5% of the first wall thickness.
This invention will become more fully understood from the following detailed description, taken in conjunction with the accompanying drawings described herein below, and wherein like reference numerals refer to like parts.
Referring to
Referring to
The handle portion 16 is an elongate structure extending along the axis 14. The handle portion 16 has a proximal end region 22 and a distal end region 24, which extends along, and diverges outwardly from, the axis 14 outwardly projecting from and along the axis 14 to form a substantially frusto-conical shape for connecting or coupling to the hitting portion 18. Preferably, the handle portion 16 is sized for gripping by the user and includes a grip 26 wrapped around and extending longitudinally along the handle portion 16, and a knob 28 connected to the proximal end 22 of the handle portion 16. The handle member 16 is formed of a strong, flexible, lightweight material, preferably a composite material. Alternatively, the handle portion 16 can be formed of other materials such as aluminum or wood. In other alternative embodiments, heavier materials such as other metals and steels can be used.
The hitting portion 18 of the frame 12 is “tubular,” “generally tubular,” or “substantially tubular,” each terms intended to encompass softball style bats having a substantially cylindrical impact portion (or “barrel”) as well as baseball style bats having a generally frusto-conical barrel. The hitting portion extends along the axis 14 and has a distal end region 32, a proximal end region 34, and a central region 36 disposed between the distal and proximal end regions 32 and 34. The proximal end region 34 converges toward the axis 14 in a direction toward the proximal end of the hitting portion 18 to form a frusto-conical shape that is complementary to the shape of the distal end region 24 of the handle portion 16. The hitting portion 18 can be directly connected to the handle portion. The connection can involve a portion of, or substantially all of, the distal end region 24 of the handle portion 16 and the proximal end region 34 of the hitting portion 18. Alternatively, an intermediate member can be used to separate and/or attach the handle portion 16 to the hitting portion 18. The intermediate member can space apart all or a portion of the hitting portion 16 from the handle portion 16, and it can be formed of an elastomeric material, an epoxy, an adhesive, a plastic or any conventional spacer material. The bat 10 further includes an end cap 38 attached to the distal end 32 of the hitting portion 18 to substantially enclose the distal end 32.
The tubular frame 12 can be sized to meet the needs of a specific player, a specific application, or any other related need. The frame 12 can be sized in a variety of different weights, lengths and diameters to meet such needs. For example, the weight of the frame 12 can be formed within the range of 15 ounces to 36 ounces, the length of the frame can be formed within the range of 24 to 36 inches, and the maximum diameter of the hitting portion 18 can range from 1.5 to 3.5 inches.
Unlike existing ball bats, which are typically formed of aluminum, titanium, wood, or a composite material, the present invention is directed toward the use of steel to form the hitting portion 18 of the ball bat. The steel bat of the present invention provides exceptional performance at a very reasonable price. Aluminum, titanium and composite materials all have drawbacks. Aluminum is lightweight and has good workability, but can be quite expensive, as much as ten times the cost of conventional steel, and the yield strength is lower than titanium or heat treated steel. Because the performance of a bat is directly related to the toughness and strength of the bat material, the thickness of the hitting portion 18 must be greater for aluminum than for other higher strength materials. As a result, more aluminum is required to construct a bat. Titanium has a very high yield strength and is lighter than steel, but titanium is very expensive (with a much higher cost than aluminum), and it has very low workability making it hard to swage or form into the desired shape. Composite materials are lightweight and can be formed to a desired strength, but the material and manufacturing costs can be quite high.
The hitting portions of existing ball bats are not formed of steel because (1) the density (and the corresponding weight) of steel is quite high (approximately 3 times the density of aluminum and twice the density of titanium), and (2) because untreated steels have very low yield strengths. Premium steels, such as, for example, maraging steels, high carbon content steels, and other high alloy content steels, can provide a very high yield strength, however, these materials also very expensive and provide very low workability.
The present invention overcomes these drawbacks by forming a ball bat using carburized and tempered steel. More specifically, at least a portion of the hitting portion 18 of the bat 10 is formed of a conventional carbon steel, an alloy steel or a high strength low alloy steel, which is carburized and tempered to produce a hitting portion 18 that provides exceptional performance at a very reasonable price. Conventional carbon steels, alloy steels and high strength low alloy steels (hereinafter referred to as “Conventional Steels”) are generally significantly less expensive (often less than $1 per lb.) than other materials such as aluminum (often approximately $10 per lb.), titanium, premium steels and composites. Conventional Steels also provide exceptional workability, ductility and toughness.
Untreated Conventional Steels however have a low yield strength (approximately 30 ksi compared to aluminum with a yield strength of approximately 85 ksi,), in addition to a high density as mentioned above. Higher strength materials are desirable in the construction of ball bats because a higher strength material can be formed with a thinner tubular wall thickness without denting, or plastically deforming, upon impact with a ball during play. Higher strength materials also tend to flex more, thereby providing more of a “trampoline” type effect to the bat, upon impact with a ball. The thinner walls achieved through the use of a high strength material require less material to form the bat. However, high strength cannot be achieved at the expense of ductility. A high strength material having low ductility can become brittle and prone to brittle failure or fracture modes. Such failure modes are undesirable since they can result in cracking or shattering of the ball bat raising safety issues.
Heat treating Conventional Steels increases the yield strength of Conventional Steels to approximately 150 ksi. However, due to the high density of Conventional Steels, the yield strength of heat-treated Conventional Steels is insufficient to enable the wall thickness of the hitting portion of the bat to be reduced to a viable level. The wall thickness required for a heat treated Conventional Steel bat would result in a bat that exceeds all desired weight ranges for conventional play.
The present invention overcomes these obstacles by carburizing at least a portion of the hitting portion 18 of the bat 10. The carburization of the Conventional Steel significantly increases the micro-hardness and the yield strength of the hitting portion when measured in a ring load test as described below. Carburizing Conventional Steels can increase the yield strength of the hitting portion of the bat up to as high as 300 ksi. Carburization can also be applied to Conventional Steels without significantly decreasing the ductility and toughness of the material. The high strength and high ductility achieved through carburization enables Conventional Steels to be used in ball bat applications without causing the bat to fall outside of conventional design characteristics, such as bat weight.
Carburization is a metallurgical process whereby carbon is added or impregnated into a material, such as a Conventional Steel, beginning on the surface or surfaces of the Conventional Steel that are exposed to the carbon. Carburization involves heating the bat 10, or a portion of the bat 10, in a furnace (or other conventional apparatus) and then introducing a carbon rich atmosphere into the furnace. Variables such as furnace temperature, furnace time, the atmosphere including the carbon content, control the depth of penetration and the degree or percent of carbon content in the hitting portion 18 or the bat 10. After carburization, the bat 10 and/or hitting portion is quenched and then tempered to develop an optimum combination of hardness, strength and toughness.
Carburization is preferably performed on at least a portion of a bat 10 or a hitting portion of a bat after the bat has been formed and/or swaged into the desired shape, thereby enabling the Conventional Steel to be worked and formed when it possesses a very high workability. Because carburization can be performed on only a portion of the hitting portion 18, if desired, selectively applying carburization enables the bat to be formed with exceptional yield strength characteristics in the specific desired location(s).
Referring to
In alternative preferred embodiments, a stop-off coating, or other masking tool, can be used to prevent or inhibit the addition or diffusion of carbon into a portion of the exposed surface of the bat 10. One such stop-off coating is a Water-based Carburizing Stop-Off Coating supplied by Avion Manufacturing of Brunswick, Ohio. In one particularly preferred alternative embodiment, the stop-off coating can be applied to one or more of the distal and proximal end regions 32 and 34 of the hitting portion 18 thereby allowing for only the central region 36 to be carburized.
Referring to
By varying the temperature, duration and carbon content used during the carburization process, the depth of penetration into the bat 10 or the hitting portion 18 can be varied. As shown in
The increased yield strength achieved through the carburization of Conventional Steels enables the wall thickness of the tubular hitting portion 18 to be significantly thinner than that of conventional aluminum bats. The wall thickness of the carburized Conventional Steel hitting portion 18 is preferably within 0.030 and 0.075 inch. In a particularly preferred embodiments, narrower ranges within the 0.030 and 0.075 inch range can be used. Table 1 illustrates the approximate wall thicknesses of hitting portions of single wall ball bats for conventional aluminum ball bats and carburized Conventional Steel bats for softball, youth baseball and adult baseball ball applications. The thinner walls require less Conventional Steel and result in less overall weight. Table 1 is an example only and is not intended to be a limit on the wall thickness of the carburized Conventional Steel bat.
The use of higher strength carburized Conventional Steel allows for up to a 45% reduction in the wall thickness of a hitting portion of a bat over a conventional aluminum bat. As a result a thinner wall can be used for a hitting portion formed of carburized Conventional Steel, and, therefore, less carburized Conventional Steel is required and the weight can be reduced.
The thickness of the carburized layer, or the case depth of the carburization, can range from 0.002 inches up to the entire wall thickness of the hitting portion 18. In a particularly preferred embodiment, the thickness of the carburized layer of the hitting portion 18 is within the range of 0.010 to 0.020 inches. In another alternative preferred embodiment, the thickness of the carburized layer of the hitting portion 18 is within the range of 0.008 to 0.012 inch. Other preferred thickness ranges can also be used. By carburizing only the outer regions of the tubular wall, the ductility and toughness of the Convention Steel is maintained in the non-carburized regions of the hitting portion 18.
Forming a carburized layer at the outer and/or inner surfaces of the desired location of the hitting portion 18 introduces residual compressive stresses into the case hardened or carburized layer. These residual compressive stresses counter act applied tensile stresses, which occur upon impact with a ball. Since it is these applied tensile stresses that can lead to plastic deformation and cracking of the hitting portion 18, the residual compressive stresses improve the hitting portion's ability to withstand an impact with a ball.
The yield strength of the hitting portion 18 formed of carburized Conventional Steel increases to within the range of 200 to 300 ksi, as derived from the ring load test described below. In one particularly preferred embodiment, the yield strength of the carburized hitting portion 18 of the present invention is within the range of 218 to 278 ksi, as derived from the ring load test described below. In another particularly preferred embodiment, the yield strength of the carburized hitting portion 18 of the present invention is within the range of 262 to 278 ksi, as derived from the ring load test described below.
The localized hardness of the carburized hitting portion 18 of the present invention is typically within the range of 360 to 560 on a Knoop Hardness Scale (“HK”) (wherein the applied load is >500 gf) or within the range of 78 to 86 on a Rockwell Superficial Hardness 15N Scale. In a particularly preferred embodiment, the localized hardness of the carburized hitting portion 18 is within the range of 400 to 505 on a Knoop Hardness Scale or within the range of 79 to 84 on a Rockwell Superficial Hardness 15N Scale.
The use of carburized Conventional Steel in a ball bat is further enabled by the separate handle and hitting portions 16 and 18 of
The hitting portion 118 of the bat 110 includes first and second tubular wall transition regions 136 and 138, an intermediate tubular region 140, and distal and proximal tubular regions 142 and 144. The distal and proximal tubular regions 142 and 144 positioned adjacent a distal end of the bat 110 and the intermediate portion 110 of the frame 112, respectively. The intermediate tubular region 140 is positioned between the first and second tubular wall transition regions 136 and 138. The first transition region 136 is then positioned between the intermediate tubular region 140 and the distal tubular region 142, and the second transition region 138 is positioned between the intermediate tubular region 140 and the proximal tubular region 144.
The intermediate tubular region 140 is preferably centered about the sweet spot of the bat. The intermediate tubular region 140 preferably has a generally uniform wall thickness, which varies by less than or equal to 0.003 inch. The wall thickness of the hitting portion 118 is also preferably greatest at the intermediate tubular region 140. The generally uniform wall thickness of the intermediate tubular region 140 is within the range of 0.040 to 0.065 inch. In alternative preferred embodiments, the intermediate tubular region 140 can be formed of other thicknesses. The length of the intermediate tubular region 140 is preferably within the range of 0.25 to 9.0 inches. In a particularly preferred embodiment, the length of the intermediate tubular region 140 is within the range of 1.0 to 5.0 inches. In yet another alternative preferred embodiment, the hitting region can be formed without an intermediate tubular region.
Each of the first and second tubular wall transition regions 136 and 138 has a wall thickness that varies along the longitudinal axis 14. The first transition region 136 has a wall thickness that generally increases along the axis 14 from a first position 146, closest to the distal end of the bat 110, toward the handle portion. The second transition region 138 is preferably similar to the first transition region 136, but varies in thickness in a manner that is opposite, or symmetrical to, the first transition region 136. In particular, the wall thickness of the second transition region 138 generally increases along the longitudinal axis 14 from a second position 148, closest to the handle portion, toward the distal end. In a preferred embodiment, as shown in
The length of each of the first and second tubular wall transition regions 136 and 138 is preferably within the range of 0.25 to 7.0 inches. In a preferred embodiment, the length of the first and second tubular wall transition regions 136 and 138 is within the range of 0.25 to 5.0 inches. In alternative preferred embodiments, the first and second tubular wall transition regions can have the same length or varying lengths.
The distal and proximal tubular regions 142 and 144 are preferably positioned at opposite ends of the hitting portion 118. The distal tubular region 142 is positioned at the distal end of the bat 110 and extends to the first tubular wall transition region 136, and the proximal tubular region 144 is positioned at the proximal end of the hitting portion 118 and extends to the second tubular wall transition region 138. The distal and proximal tubular regions 142 and 144 each preferably have a generally uniform wall thickness, which varies by less than or equal to 0.003 inch along its length. The generally uniform wall thickness of the distal and proximal tubular regions 142 and 144 region can be 0.030 inch or larger. In alternative preferred embodiments, other wall thicknesses can be used, and the wall thickness can vary between the distal and proximal tubular regions 142 and 144.
The length of the distal tubular region 142 is preferably within the range of 0.25 to 4.0 inches, and the length of the proximal tubular region 144 is preferably within the range of 2.0 to 6.0 inches. Other lengths, other thicknesses and combinations thereof are also contemplated under this invention.
In yet another alternative preferred embodiment, the hitting portion 118 can be formed with one or more additional tubular wall transition regions and/or one or more additional intermediate regions. In another alternative preferred embodiment, the additional wall thickness can be used at the distal end of the bat to add strength or weight to the distal end of the bat, and to provide additional support for an end cap. The wall thickness of the hitting portion 118 can be varied to compensate for the stiffness and/or softness of the end cap being used as well as for the tapered ends of the bat frame.
In a preferred embodiment the outer diameter of the hitting portion 118 is generally uniform along its length and the inner diameter of the hitting portion 118 varies along its length to accommodate the variations in wall thickness along the length of the hitting portion 118. In alternative preferred embodiments, the insert can be formed with a generally uniform inner diameter along its length and an outer diameter that varies along its length to accommodate variation in wall thickness of the insert of the present invention. In another alternative preferred embodiment, both the inner and outer diameters of the insert can be varied along their length. In another alternative preferred embodiment, the inner and/or outer diameters of the hitting portion may vary along their length to accommodate a taper formed into the shape of the bat.
This embodiment enables the wall thickness of the hitting portion 118 to be tailored or tuned to a specific application, ball-type or player. Further, the wall thickness can be matched to other factors such as the barrel length, the bat weight, and the material selected to optimize flex within the strength of the material of the bat across the entire length of the barrel (or hitting portion 118). Like the multi-wall embodiments described above, the present embodiment enables the MOI of the bat, particularly at the distal end of the bat, to be reduced thereby enabling the player to increase his or her swing speed. The present embodiment results in an enlarged sweet spot and improves the performance of the bat beyond that of conventional single-wall bats. Further, a stop-off coating can be applied to specific portions of the hitting portion 118 to allow for carburization of only specific desired locations on the hitting portion 118.
The incorporation of the variable wall thickness to the hitting portion 118 of the bat 110 further enables the use of carburized Conventional Steel by allowing for additional material and weight to be removed from various regions of the hitting portion 118. The removed material does not reduce the performance of the bat, but rather, improves the performance by reducing the MOI of the bat and optimizing the location and wall thickness of the carburized Conventional Steel. The amount of Conventional Steel needed to produce the hitting portion 118 is thereby further reduced.
Referring to
The ring segment 52 is aligned between the first and second platens 54 and 56, such that the longitudinal axis 14 (see
Table 2 below illustrates the load, deflection, stiffness, modulus of elasticity and yield strength for three carburized and tempered ring segments (Lots A-C) formed of Conventional Steel under the present invention, and a non-carburized, heat-treated Conventional Steel ring segment (Lot D). The ring segments of Lots A-D have a nominal outside diameter of 2.25 inches and a nominal wall thickness of 0.0395 inch. Lots A-C were carburized, quenched in oil, and then tempered at temperatures between 650 ad 800 degF for approximately 2 hours. Lot D is non-carburized and induction heat treated.
The yield strength of the carburized Conventional Steel ring segments (Lots A-C) is substantially higher than the yield strength of a heat-treated, non-carburized Conventional Steel ring segment (Lot D). As discussed above, the increased yield strength of the carburized Conventional Steel hitting portion enables a thinner wall thickness to be used, which allows for less material and improves the flexibility and “trampoline” effect of the hitting portion of the bat.
Table 3 below is a hardness profile graph of a carburized and tempered Conventional Steel ring segment. The wall thickness of the ring segment is 0.040 in. The ring segment was carburized at a 0.7% carbon potential for a carburized layer (or case depth) of 0.010 to 0.015 in on the inner and outer surface of the ring segment. The hardness scale used is a Knoop Hardness Scale in the range of 0 to 600.
The graph of Table 3 illustrates the increased hardness of the ring segment at the inner and outer surfaces. The inner and outer surfaces have a hardness of approximately 500 on a Knoop Hardness Scale while the center of the ring segment had a lower hardness value of approximately 400 on a Knoop Hardness Scale. The inner and outer surfaces being carburized and having residual compressive stresses that increase the hardness of the inner and outer surfaces, while the middle of the ring segment remain substantially unchanged and retains its toughness and ductility. The combination of these characteristics provide for an exceptionally performing ball bat.
Referring to
Carbon is then induced into the atmosphere of the furnace 200. Preferably a volume of carbon monoxide from a storage vessel 202 is introduced into the furnace atmosphere. The carbon content of the furnace atmosphere provides the driving force for carbon absorption (or diffusion) into the exposed surfaces of the bat 10 or hitting portion 18 of the bat 10. This atmosphere carbon content is referred to as carbon potential. Low carbon potentials significantly increase the time required for carburizing. Excessively high carbon potentials can result in carbide formation in the carburized layer (or case). Carbide formation would reduce impact toughness of the carburized or case hardened layer, and therefore is undesirable. In one preferred embodiment, a carbon potential range of 0.75% to 0.85% is used. This range strikes an appropriate balance between efficient carburizing and acceptable case impact toughness. In alternative preferred embodiments, other carbon potential ranges can be employed. Carburizing time also affects the depth of the carburized layer, or the case depth. The carburizing time is pre-selected for a desired case depth. In one preferred embodiment, the carburizing time is approximately 2 hours. In other alternative preferred embodiments, other durations can be used. The carburization method described above is a gas-type carburization. In alternative preferred embodiments, the carburization of the bat 10, the hitting portion 18 or a portion thereof can be performed through pack carburization, liquid carburization, vacuum carburization, or plasma (ion) carburization.
Following carburization, the bat 10 is moved to a quenching station 204 where the bat 10 is submerged into a quenching media, preferably an agitated oil 206. Alternatively, other oils or fluids (including air) can be used. In a particularly preferred embodiment, the quenching oil 206 is held at approximately 140 degF. Rapid quenching is desired, however, too rapid of quenching can cause cracking and distortion. Quenching that is too slow will not induce the desired hardness levels of the bat 10.
Following quenching, the bat 10 is moved to another furnace 208, where it is tempered. Tempering enables the case and core hardness and impact toughness to increase. In one preferred embodiment, the tempering temperature is set within the range of 650 to 800 degF. Alternatively, other temperatures can be used. The tempering time is also variable. In one preferred embodiment, the tempering time is approximately 2 hours. In other preferred embodiments, other durations can be used. Following tempering, the bat 10 is racked in a racking station 210 to minimize distortion.
This process can also be performed on only a portion of the bat 10 or the hitting portion 18 through use of the stop-off coating described above. In other preferred embodiments, the carburization, quenching and tempering can occur in one or more machines (furnaces or stations).
Referring to
In another alternative preferred embodiment, the bat 10 can further include a tubular insert 44 coaxially aligned with the frame 12. The hitting portion 18 is preferably configured to receive the insert 44. A distal end of the hitting portion 18 is preferably curled inward to retain the insert 44, and the end cap 38 is attached to a distal region of the hitting portion 18 to substantially enclose the distal end of the bat 10. The insert 44 is a cylindrical structure preferably sized to extend within and along a significant portion of the hitting portion 18 of the frame 12. The insert 44 has opposing distal and proximal ends 46 and 48, that preferably engage the frame 12. Such engagement inhibits axial movement of the insert 44 within the frame 12.
The insert 44 is positioned within the frame 12 such that the insert 44 is capable of moving independently with respect to the frame 12 upon impact of the bat with a ball. This independent movement enables the insert 44 and the frame 12 to function during use with the characteristics of a leaf spring.
In this alternative preferred embodiment, the frame 12 is formed of a high strength, lightweight material, such as aluminum. Alternatively, other materials can also be used such as composite materials. The insert 44 is formed of carburized and tempered Conventional Steel. The carburized Conventional Steel of the insert 44 includes the same attributes as the Conventional Steel for the hitting portion 18 described above.
Referring to
In alternative preferred embodiments, the Conventional Steel bat or hitting portion can be nitrided in lieu of being carburized. Nitriding, which involves diffusing or impregnating nitrogen into the exposed surface(s) of the Conventional Steel, can be performed using gas, pack, liquid, pressure, vacuum or plasma. Boriding, which involves diffusing boron into the exposed surface or surfaces of a Conventional Steel, is another alternative treatment for the Conventional Steel bat contemplated under the present invention. Boriding can be accomplished through gas, liquid, paste, plasma vapor deposition or chemical vapor deposition. Nitriding and boriding achieves similar advantages as described above for carburized Conventional Steel. Further nitriding and boriding are accomplished in a similar manner as described above for carburization. Thermoreactive treatment whereby carbon and nitrogen are added to the bat or hitting portion is also contemplated under the present invention.
While there have been illustrated and described preferred embodiments of the present invention, it should be appreciated that numerous changes and modifications may occur to those skilled in the art and it is intended in the appended claims to cover all of those changes and modifications which fall within the spirit and scope of the present invention.
