Patent Application
20120094810
1. Field Of The Invention
This invention relates to barbells.
2. Background Art
A barbell is a piece of exercise equipment used in weight training, weightlifting and power lifting. Barbells typically have a generally longitudinally-extending bar that is between 4 feet (1.2 m) and 7 feet (2.1 m) long, with a diameter of approximately one inch (2.54 cm). The bar is often engraved in its central region with a knurled pattern where it is to be gripped by the user.
There are two fundamental types of barbells: the “fixed weight” type, wherein the weight plates are permanently secured on the ends of a bar, and the “adjustable” type, wherein weight plates at each end region are secured on the bar between a inner affixed collar and an outer removable collar to permit the user to add or remove individual weight plates to the bar. This invention pertains to adjustable barbells.
Adjustable barbells comprise a generally longitudinally-extending bar. Weights plates are slid onto the longitudinally outer end regions of the bar to obtain the desired total weight to be lifted, and are secured between a longitudinally inner collar affixed to each end region of the barbell and a removable longitudinally outer collar that is removable by the user when the addition or removal of weight plates is desired. The collars prevent the weight plates from sliding off of, or along, the bar and from wobbling during the exercise movement. In addition to preventing injury and/or property damage from a falling weight plate, the collars are intended to prevent the destabilizing effects on the barbell of sliding, falling and wobbling weight plates, which can cause muscular and skeletal injuries.
One type of adjustable barbell is the Olympic barbell, and is used by “serious” weightlifters. While conventional fixed barbells are typically limited to about 250 lbs of weight, Olympic barbells can accommodate 600 lbs or more and are frequently used to lift poundage well in excess of 350 lbs to as much as 1000 lbs. The Olympic bar used by men has defined standard dimensions. It is a metal bar that is 2.2 m (7.22 ft) long. The outer ends are 50 mm (1.9685 inches) in diameter. The central grip section of the bar is 28 mm (1.1024 inches) in diameter. The spacing between the inner collars is 1.34 meters (52.675 inches). The Olympic bar used by women is shorter (2.05 m) with a thinner grip section (25 mm).
Olympic barbells typically include a tubular sleeve coupled to the bar at each end region onto which the weight plates are mounted. The sleeve is mounted on bushings or bearings about the bar for rotation, permitting the weight plates to rotate about the longitudinal axis of the bar during the exercise movement. This reduces destabilizing torque that the plates can transmit to the bar owing to the rotationally-directed inertia of the weight plate that opposes plate acceleration and deceleration during the exercise movement. Given the tremendous forces created by the huge poundage being lifted, there is great concern about (and attention paid to) the injurious effects of the consequential and substantial destabilizing forces that are generated during the exercise movements.
To reduce the destabilizing forces generated on the bar by the weight plates, the inner collar associated with the barbell is increased in weight. Because the inner collar is relatively close to the user's hand during the movement, the moment arm associated with the weight is substantially less than the moment arm that would be associated with an equal weight at a relatively longitudinally-outer position. The decreased moment arm reduces the destabilizing force attributable to that weight, resulting in a more controllable barbell at a given poundage.
I believe that the destabilizing forces are reduced because of the lesser moment of inertia (“MOI”) attributable to the resulting configuration. MOI is the resistance of the weight plate mass to changes in velocity. These changes occur, for example, when the barbell is first lifted, causing the weight plates to accelerate from a zero velocity. During the movement, slight changes in velocity occur owing to the characteristics of the lifter's muscular-skeletal construction, which results in uneven acceleration of the barbell over the course of movement, together with a generally arcuate path of motion of the plates (which can be thought of as concurrent changes in velocity in the horizontal and vertical directions). The bar experiences a bending downward as the plates are accelerated at the commencement of the movement. As the barbell reaches the end of the movement, the barbell approaches zero velocity, but the inertia of the weight plates causes them to resist deceleration, resulting in a bending of the bar upward. In addition, the lifter likely has a dominant side—be it left or right—that results in uneven forces being applied to the left and right sides of the barbell. All of this creates a complex combination of destabilizing forces that can make the bar difficult to control.
The MOI associated with a given mass increases with the square of its distance from the axis of rotation. Thus, a weight plate at the end of the bar has significantly more MOI than the same weight plate near the mass' center of rotation during the lifting movement. The stress imposed on the bar by a weight plate increases linearly with its distance from the fulcrum. Accordingly, destabilizing forces and bar stresses are reduced when the inner collars associated with the barbell are increased in weight in lieu of the same weight being positioned at the longitudinally-outmost positions.
Preferably, the weight of the innermost collar is increased beyond conventional collars sufficiently so that the bar and inner collars weigh a total of approximately 80 lbs or more.
These and further details of the invention will be apparent to those of ordinary skill in the art from reading a description of the preferred embodiment of the invention described below, of which the drawing forms a part.
Referring to
A pair of cylindrical sleeves 26, 28 are mounted at the longitudinally outer end regions 18, 20 respectively for rotation about the axis 11, and are sized to accommodate the generally central through-holes of weight plates mounted about the sleeves. Bearings or bushings are utilized between the sleeves and bar to permit the rotation, and many exemplary configurations of bushings and bearings are known in the art.
Those skilled in the art will recognize that the sleeves may be mounted for rotation about a longitudinal axis that is not coaxial with the longitudinal axis that passes through the major portion of the bar that lies between the collars. This configuration permits the plates' centers of mass to be positioned below that portion of the bar's axis that passes through the region where the user grips the bar. Accordingly, the invention herein is not limited to the axis of the bar and the axis of the sleeves being wholly coaxial.
The inner collars 14, 16 weigh at least 20 lbs each, preferably at least 40 lbs each, and are affixed to the bar 10. Preferably, the collars are interference-fit onto the bar and are welded in place.
Because the preferred collars 14, 16 can be increased to any desired weight above 40 lbs each, the barbell can accommodate virtually any anticipated liftable poundage while minimizing destabilizing forces associated with the weight plates' moments of inertia and also permitting heavy poundage to be lifted without a need to employ longer bars. It may be noted, in this regard, that the moments of inertia associated with weight plates positioned near the ends of a bar in excess of the seven foot standard length are greatly increased because the MOI increases with the square of the plates' distances from the axis of rotation. Accordingly, the ability to retain a 7 foot length is significant when destabilizing forces are of concern.
In addition to the foregoing improvements, a barbell constructed in accordance with the invention subjects the bar to less stress for a given liftable poundage. When weight plates are loaded onto a bar, and supported above ground level by the bar, the outer ends regions of the bar tend to bow downward below the bar's center region. The degree of bowing caused by a given weight plate increases as its distance from the center of the bar increases because the force acting on the bar is a product of the weight and its distance from the bar's center (i.e., the fulcrum of the resulting lever). The bowing of the bar arising from the poundages lifted by serious weight lifters adds another degree of instability to the lifting movement as the bar flexes up and down owing to the intertia of the weight plates and their respective moment arms. Those of ordinary skill in the art recognize that this instability results in a further lack of controlled lifting, with a consequential risk of injury and/or property damage. Moreover, flexing can, over time, cause metal fatigue in the bar, leading to additional risk of injury and/or damage.
A barbell constructed in accordance with the invention reduces the degree of bowing for a given poundage by reducing the moment arm over which the weigh plates act, while providing a barbell that conforms to the bar dimensions and collar separation imposed by the Olympic bar standards.
One example of a barbell constructed in accordance with the invention comprises a pair of 50 lb. steel collars 14, 16 having a 10 inch diameter and a 2.375 inch thickness. The end portion 18, 20 of the bar (and its overlying rotatable sleeve 26, 28) are approximately 15.375 inches in length, the sleeve diameter being approximately 1.97 inches. Another example of a barbell constructed in accordance with the invention comprises a pair of 100 lb. steel collars 14, 16 having a 14 inch diameter, while a third example comprises a pair of 150 lb. steel collars 14, 16 having a 17 inch diameter, the remaining dimensions of the barbell preferably remaining the same as the first example in both cases.
Those skilled in the art having the benefit of this disclosure will recognize that the various dimensions, materials and weights of the collars can be utilized to achieve the described improvement; all such modifications are within the spirit and scope of the invention. Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as will be defined by appended claims.
