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This application claims the benefit of U.S. Application No. 60/668,679, filed Apr. 6, 2005, the entire teachings of which are incorporated herein by reference.
Cue sticks utilize a variety of materials in their construction. In particular, the tip of a cue stick, which is used to strike a ball during a billiards game, is typically made of a different type of material (e.g., leather or linen phenolic) than the actual shaft construction of the cue stick (e.g., wood). Therefore, the prior art has developed various methods for attaching the tip to the remainder of a cue stick
In the prior art, the tip of cue stick is often attached to a shaft using a plug made of wood or plastic. Specifically, the shaft of the cue stick, at the distal end to which the tip is attached, has a cavity into which the plug is inserted. The tip is attached to the shaft by contact, through adhesive, with the tip end of the shaft and contact of the plug with the sides of the cavity. Repeated ball strikes by the tip over the life of the cue stick tend to weaken the bonding of the tip, resulting in eventual detachment of the tip from the remainder of the cue stick. This problem is especially prominent when the tip is directly bonded to a composite shaft surface because of the incompressibility of the composite material relative to the tip material. If a plug is not used, in the case where the tip is attached to the distal end of the shaft, the unequal loading of force on the tip causes especially high wear. Even linen phenolic tips exhibit substantial compressibility under the force necessary to strike a cue ball during a break shot.
In addition, the plug tends to increase the weight of the cue stick near the tip end, accentuating a phenomenon known as cue ball deflection. When a player imparts english to a cue ball by striking the cue ball away from its center of mass, stick. As discussed in U.S. Pat. No. 6,162,128, the entire contents of which are hereby incorporated herein by reference, increased weight at the tip end of a shaft accentuates the deflection of a struck cue ball during off-center ball strikes.
A need exists to provide a more robust way of attaching a tip to the remainder of a cue stick, while decreasing the weight of the tip end of the stick. Embodiments of the present invention are directed to addressing these needs.
In an embodiment of the invention, a cue stick comprises a shaft having a cavity at a distal end; a high stiffness, lightweight tip plate attached to the distal end of the shaft; and a tip attached to the tip plate for striking a ball. The tip plate may be comprised of a lightweight material having a high stiffness, such as carbon fibers in a composite matrix or binder, Kevlar®, beryllium, titanium, boron, or magnesium. The tip plate may weigh less than about 0.4 grams and exhibit substantially no deflection under a force of less than about 1100 pounds. The shaft may comprise a composite material where the shaft directly attaches to the tip plate, or the shaft may be comprised of wood. The tip may be comprised of phenolic. The tip plate may be shaped as a disk or with an extending lip.
Other embodiments of the invention are drawn to sections of cue sticks utilizing a tip plate and a method of striking a ball utilizing a cue stick having a tip plate to decrease ball deflection.
The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention.
FIG. 1A is a side view, cross section of a cue stick in accord with an embodiment of the invention.
FIG. 1B is a closer side view, cross section of tip end of the cue stick in FIG. 1A, consistent with an embodiment of the invention.
FIG. 2 is a side view, cross section of a cue stick with a sleeve having a end projection, and a tip plate with an extension, consistent with an embodiment of the invention.
FIG. 3A is a side view, cross section of a cue stick with a tip plate having an extending lip, consistent with an embodiment of the invention.
FIG. 3B is a closer side view, cross section of the cue stick in FIG. 3A, consistent with an embodiment of the invention.
FIG. 3C is a side view of the tip plate used in FIGS. 3A and 3B attached to a section of a tip in accord with an embodiment of the invention.
FIG. 4 is a side view, cross section of the tip plate in FIGS. 3A-3C used in conjunction with an alternative shaft, in accord with an embodiment of the invention.
FIG. 5 provides a perspective view of the robotic arm used to test cue sticks in accord with an embodiment of the invention.
A description of preferred embodiments of the invention follows.
A cue stick consistent with an embodiment of the invention is shown in FIGS. 1A and 1B. A cue stick 100 includes a tip 110 used for striking a ball. The tip 110 is directly attached to a tip plate 120. The tip plate 120 is attached to the shaft 150 of the cue stick 100. The tip plate typically has a cross section of similar shape and diameter as the section of the cue stick and tip to which it is adjacent, though embodiments of the invention do not necessarily require this.
In this particular embodiment, the shaft 150 includes a bored section 140 (or cavity) with two different bored radii and a sleeve 130. Other embodiments of the invention, however, may utilize a shaft that does not include a sleeve, or utilize a shaft with different shaped bores. In a more particular embodiment of the invention, the bore may be at least 3 inches in length.
Since the tip is secured to the tip plate, and the tip plate to the shaft, the tip attachment to the cue stick is stronger and more durable. Prior art methods of attaching a tip to the shaft of a cue stick rely upon a tip attached to a plug that inserts into a cavity of a cue stick. Striking the tip with a ball results in an uneven force distribution in the tip between the portions of the tip which attach to the shaft and the portions adhering to the plug. This results in wear and damage that tends to weaken the attachment of the tip to the rest of the cue stick, eventually resulting in detachment of the tip. In contrast, embodiments of the current invention maintain a stronger and more durable attachment because the force of each ball strike is more equally distributed over the extended contact surface between the tip and tip plate. As well, the use of the tip plate may be especially advantageous when a composite shaft configuration is utilized since the ensemble of the tip plate bonded to the composite shaft is especially durable relative to bonding the tip to a wooden shaft. It is noted, however, that wooden cue sticks may also benefit from the use of a tip plate.
Furthermore, the tip plate provides a method for attaching a tip to a cue stick that tends to make the front end lighter than using a conventional cue attachment plug. In contrast to the use of a plug, typical tenon, or other prior art devices to attach the tip to the distal end of the cue stick, the tip plate's lighter weight decreases the weight present at the tip end of the cue stick, thereby decreasing the effects of cue ball deflection. The properties of the tip plate, however, allow the cavity in the shaft to maintain its integrity while supporting the tip. Testing by the applicant, as shown in the Example herein, shows that a tip plate that decreases the weight at the tip end of a cue stick relative to a wood plug tends to decrease the cue ball deflection of off center ball strikes, resulting in a more accurate cue ball trajectory. In addition, the stiffer construction afforded by the tip plate mounted to a shaft having a cavity at its distal end results in an increased speed for a ball struck by the cue.
Embodiments of the invention utilize a tip plate comprising a material that has lightweight and high-stiffness (i.e., low compressibility). In one embodiment, the tip plate material has a lower compressibility than the material comprising the tip. The stiffness of the tip plate may be operationally defined in that the tip plate typically exhibits substantially no deflection when utilized in a ball strike. In a particular embodiment, the tip plate exhibits substantially no deflection when impacted under a force of less than about 1200 pounds. In another embodiment of the invention, the tip plate exhibits substantially no deflection under a force of less than about 800 pounds (typically the maximum loads are in the range of about 800 to about 1000 pounds). The weight of the tip plate, in embodiments of the invention, is typically less than about 0.6 or about 0.5 grams. More preferably, the weight of the tip plate is less than about 0.4 grams or 0.3 grams.
As well the tip plate preferably exhibits durability through its ability to maintain integrity after cyclical loads from repeated ball strikes. For example, maple wood exhibits high stiffness and lightweight. However, the grains of the wood result in maple having poor fatigue properties; the wood breaking apart after a substantial number of loads.
Preferred materials for the tip plate include metals such as beryllium, magnesium, titanium, or alloys containing one or more such metals. Other materials for tip plate construction include Kevlar®, boron, or fiberglass. More preferably, the tip plate is constructed of a carbon based material (e.g., mixtures of carbon nanostructures residing in a resin matrix, or carbon fibers in a binder). Carbon is especially advantageous since particular forms of carbon have an especially high stiffness to weight ratio. Even more preferably the tip plate is constructed of carbon fibers in a composite matrix. In a specific embodiment, the tip plate is constructed of a combination of stacked layers of carbon fibers, each layer of fibers aligned in a particular orientation. The layers are stacked such that there is no preferred orientation of all the layers to maximize the stiffness of the tip plate; the layers are held in a resin or other type of binder. For example, each layer of carbon fibers may be about 0.005 inches thick; thus a resulting tip plate with a thickness of 0.070 inches has about 14 layers of carbon fibers.
The thickness of tip plate is typically kept as thin as possible to decrease the weight added to the tip end of the cue stick, while thick enough to maintain the strength and durability of attachment of the tip to the remainder of the cue stick. Thus, in the instance where a shaft includes a bored section, the thickness is also a function of the diameter of the bore. When carbon fibers in a matrix are used to create a tip plate, the thickness is typically between about 0.040 and 0.140 inches. More particularly, composite cues with a bore diameter of about 0.250 inches may utilize a carbon fiber plate having a thickness between about 0.050 inches and about 0.060 inches. Composite cues with a bore diameter of about 0.290 inches may utilize a carbon fiber plate having a thickness between about 0.060 inches and about 0.080 inches. Composite cues with a bore diameter of about 0.400 inches may utilize a carbon fiber plate having a thickness between about 0.070 inches and about 0.100 inches. A typical diameter of the tip plate used in the above examples ranges from about 0.45 inches to about 0.55 inches. The weight of the above described tip plates may also define particular embodiment of the weight of a tip plate since the density of the carbon fibers in a matrix is about 25 grams per cubic inch (e.g., the weight of a 0.50 inch thick tip plate of a disk shape is about 0.26 grams).
Tips of cue sticks that may be utilized with embodiments of the invention include the range of types used by those in the art. Preferably, the tip comprises a phenolic material (e.g., a linen/phenolic or linen reinforced phenolic tip). Other tip materials include leather and leather composite, the latter being a mixture of leather particulates distributed in a resin binder.
The tip plate is directly attached to the cue stick tip using any technique known to those in the art. Preferably, the tip and tip plate are attached in a manner such that the force of a ball strike is distributed along much of the surface of contact between the tip and the tip plate. For example, an epoxy or other adhesive (e.g., DP420 epoxy adhesive by the 3M Corporation) is used to directly attach the tip and the tip plate in a preferred embodiment of the invention.
The tip plate is also attached to the shaft of the cue stick by techniques known to those of skill in the art, such as an epoxy or other adhesive (e.g., DP420 epoxy adhesive by the 3M Corporation). Such attachment may be by direct bonding of the tip plate to a surface of the shaft 155, as shown in FIG. 1B. The tip plate may also be attached to other surfaces such as a portion of the sleeve 130, also shown in FIG. 1B. In an alternative embodiment of the invention, a tip plate 230 may attach to the shaft 250 indirectly as shown in FIG. 2. A sleeve 230 may be shaped with an end projection 235 that covers the tip end of shaft 250. Thus the tip plate 220 attaches to the shaft 250 through the plate 220 attachment to the sleeve 230. Such an embodiment may be advantageous since the tip plate may bond to only one type of surface for which the adhesive is particularly suited.
The tip plate is not necessarily a disk shaped object. For example, a tip plate may be shaped to increase the surface area of contact between the tip plate and an adhering surface to strengthen the bonding, while limiting any additional mass in the tip plate due to such configuration. Though particular tip plate configurations are described herein with respect to particular embodiments of the invention, it is understood that the configuration may also be used with other embodiments described within the application.
In an embodiment of the invention, the tip plate is shaped to provide extended surface area for bonding. As shown in FIG. 2, the tip plate 220 contains a small extension 225 on the side opposite the tip 210 to allow additional surface area for bonding with the sleeve 230 at the end projection 235. Such extension is typically small to minimize the additional mass of the tip plate needed to create such an extension. For example, a carbon fiber tip plate 220 in FIG. 2 may have a thickness of about 0.060 inches, where the tip plate 220 contacts the upper lip surface 236 of the sleeve 230, and a thickness of about 0.080 inches at the extension 225.
FIGS. 3A-3C provide illustrations of a cue stick and another type of tip plate consistent with an embodiment of the invention. As depicted in FIG. 3C, tip plate 320 is directly attached to a section of a cue stick tip 310. The tip plate 320 has an extending lip 325. The thickness of the tip plate 320 inside the extending lip 325 may not be the same thickness as outside the extending lip 325. As shown in FIG. 3C, the thickness of the tip plate 320 is greater inside the extending lip than outside the extending lip 325. In a particular example, a carbon fiber tip plate configured as shown in FIG. 3C may be about 0.070 inches thick inside the extending lip, and about 0.060 inches thick outside the extending lip.
The tip plate 320 is used to mount tip 310 to the shaft 350 of a cue stick 300 as shown in FIGS. 3A and 3B. The lip extension 325 of the tip plate 320 extends into a bored section 340 of the shaft 350, allowing more surface contact between the shaft 350 and the tip plate 320. The increased surface area allows for better attachment of the tip plate to the shaft. Furthermore, the extending lip utilizes less additional mass than an extension as depicted in FIG. 2, allowing one to further the advantage of using less mass in the tip end of a cue stick.
The tip plate shape depicted in FIGS. 3A-3C is also utilized in an embodiment of the invention shown in FIG. 4. The section of the cue stick 400 shown in FIG. 4 does not use a sleeve 330, as shown in FIGS. 3A and 3B. Instead, the composite shaft 450 directly attaches to the tip plate 420. In particular, carbon fibers in the composite shaft 450 are aligned in along the longitudinal axis along the lower section of the shaft 453 and the shaft wall on the side of the dotted line closer to the centerline 451 of the shaft. The section of the shaft closer to the outer wall of the shaft relative to the dotted line 452 contains fibers that are aligned circumferentially around the centerline of the shaft. The tip end of the shaft is configured such that the lip extension 425 of the tip plate 420 rests on the shaft section 451 without any overhang of the lip extension 425. This configuration, along with the tapering of the inner wall of the shaft 454, provides additional strength for the tip plate and shaft combination.
Other embodiments of the invention utilize the features of a tip plate described herein in a wide variety of cue sticks, and cue stick sections. For example, in a two-piece cue stick comprising a shaft section and a butt section that are detachably connected, the shaft section is attached to a tip plate at a distal end, covering a cavity in the shaft section. The tip is directly connected to the tip plate. In a related embodiment of the invention, the tip plate may be part of a three or greater piece cue stick, the tip plate used with the section that includes the cue stick's striking tip. Related embodiments incorporate other features of embodiments of the invention described herein.
Another embodiment of the invention is directed toward a method of reducing ball deflection when making an off center ball strike. The method includes the step of providing a cue stick with a tip plate directly attached to a tip of the cue stick. The ball is struck with the cue stick by propelling the cue stick in a line-like direction (e.g., a straight line according to a player making a ball strike) in which the line does not travel through the center of mass of the ball. The method propels the ball in a trajectory with less ball deflection that if the cue stick did not include a tip plate. Related embodiments may use any of the cue sticks or cue stick sections described herein to reduce ball deflection. Such a method is especially advantageous to players of billiards games who cannot accommodate for the accentuated ball deflection during a cue ball shot.
While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.
The following example is provided to illustrate some embodiments of the invention. The example is not intended to limit the scope of any particular embodiment utilized.
A test showing the improvement in cue ball deflection exhibited by three commercially available cue sticks modified with a carbon fiber composite tip plate was performed. Unmodified cue stick A (Mizerak Pool Cue, Model No. PO-437) is a composite cue stick utilizing a plastic plug to attach the tip to the shaft. Unmodified cue stick B (Hamson Pool Cues) is a composite cue stick utilizing a wood plug to attach the tip to the shaft. Unmodified cue stick C (Predator Pool Cue, Model 314) is a composite cue stick utilizing an isoplast cap to attach the tip to the shaft.
A robotic arm was used to stroke each pool cue with a particular force in a straight line to strike a cue ball. The robot, shown in FIG. 5, has a number of discrete bridge setting and spring settings to control the stroking of a cue stick. In the tests described in this example, a particular bridge and spring setting were used for all the ball strikes, resulting in a consistent force imparted to the struck cue balls. The cue ball was struck in a line parallel and 9 mm offset from a line through the center of mass of the cue ball. A zero deflection location is noted at a distance of 50 inches from the point at which the cue ball is struck along a line collinear with the pool cue stroke. The actual location of the ball after traveling 50 inches from impact is noted. The difference between the zero deflection location and the actual location is the cue ball deflection. For each pool cue a series of four strokes were performed, with the corresponding deflection measured. The average value of the deflection for the series of strokes was recorded.
For each pool cue, two average deflection calculations were performed. The first deflection calculation was based on a series of strokes utilizing the pool cue as purchased. The second deflection calculation was based on a series of strokes utilizing the pool cue after each cue was modified by replacing the plug or isoplast cap used to hold the tip with a carbon fiber composite tip plate. The results of the test are shown in Table 1.
|Results from Cue Ball Deflection Test|
|Deflection using||Carbon Fiber|
|Plug or Isoplast||Composite Tip||% change in|
|Cue Stick||Cap (mm)||Plate (mm)||deflection|
As recorded in the results of Table 1, the use of a tip plate in each cue stick reduced cue ball deflection relative to the originally unmodified cue stick.