BACKGROUND
The present subject matter is directed to apparatuses and methods regarding crossbows. More specifically the present subject matter is directed to apparatuses and methods for cams for a crossbow.
Crossbows have been used for many years as a weapon for hunting and fishing, and for target shooting. Crossbows typically comprise a bowstring engaged through a set of pulleys or cams to a set of limbs and to a set of power cords. Engagement of the set of power cords is of interest. It is of interest to make the engagement of the set of power cords reliable, light, inexpensive, low maintenance, efficient, safe, and adjustable.
One known issue affecting or relevant to reliability, weight, cost, maintenance, efficiency, and safety is “cam lean”. Cam lean is the operation of one or more cams out of alignment with a design operational plane due to force imbalances or other factors.
It remains desirable to improve engagement of the set of power cords to reduce, minimize, or eliminate cam lean.
SUMMARY
Provided is a crossbow comprising a bow having: a riser having a first riser side and a second riser side; a first cam set having a first shaft, a first power cord cam of the first cam set, a bowstring cam, and a second power cord cam of the first cam set; a second cam set having a second shaft, a first power cord cam of the second cam set, a bowstring cam, and a second power cord cam of the second cam set; a first power cord engaged with the first power cord cam of the first cam set and the first riser side; a second power cord engaged with the first power cord cam of the second cam set and the second riser side; and a third power cord engaged between the second power cord cams
BRIEF DESCRIPTION OF THE DRAWINGS
The present subject matter may take physical form in certain parts and arrangement of parts, embodiments of which will be described in detail in this specification and illustrated in the accompanying drawings which form a part hereof and wherein:
FIG. 1 is a view of one non-limiting embodiment of a conventional crossbow.
FIG. 2a is another view of a first non-limiting embodiment of a set of power cords and a set of cams.
FIG. 2b is another view of a second non-limiting embodiment of a set of power cords and a set of cams.
FIG. 3 is view of one non-limiting embodiment of crossbow cams.
FIG. 4 is a schematic diagram showing one non-limiting embodiment of a crossbow.
DEFINITIONS
The following definitions are controlling for the disclosed subject matter:
“Arrow” means a projectile that is shot with (or launched by) a bow assembly.
“Bow” means a bent, curved, or arched object.
“Bow Assembly” means a weapon comprising a bow and a bowstring that shoots or propels arrows powered by the elasticity of the bow and the drawn bowstring.
“Bowstring” means a string or cable attached to a bow.
“Compound Bow” means a crossbow that has wheels, pulleys or cams at each end of the bow through which the bowstring passes.
“Crossbow” means a weapon comprising a bow assembly and a trigger mechanism both mounted to a main beam.
“Draw Weight” means the amount of force required to draw or pull the bowstring on a crossbow into a cocked condition.
“Main Beam” means the longitudinal structural member of a weapon used to support the trigger mechanism and often other components as well. For crossbows, the main beam also supports the bow assembly. The main beam often comprises a stock member, held by the person using the weapon, and a barrel, used to guide the projectile being shot or fired by the weapon.
“Power Stroke” means the linear distance that the bowstring is moved between the uncocked condition and the cocked condition.
“Trigger Mechanism” means the portion of a weapon that shoots, fires or releases the projectile of a weapon. As applied to crossbows, trigger mechanism means any device that holds the bowstring of a crossbow in the drawn or cocked condition and which can thereafter be operated to release the bowstring out of the drawn condition to shoot an arrow.
“Weapon” means any device that can be used in fighting or hunting that shoots or fires a projectile including bow assemblies and crossbows.
DETAILED DESCRIPTION
Referring now to the drawings wherein the showings are for purposes of illustrating embodiments of the present subject matter only and not for purposes of limiting the same, and wherein like reference numerals are understood to refer to like components, provided are a crossbow cam and a method of using a crossbow cam.
FIG. 1 shows a crossbow 10. While the crossbow 10 shown uses a compound bow, it should be understood that this invention will work well with any type of crossbow chosen with sound judgment by a person of ordinary skill in the art.
The crossbow 10 has a main beam 12 which may include a stock member 14, and a barrel 16. The main beam 12 may be made by assembling the stock member 14 and the barrel 16 together as separate components or, in another embodiment, the main beam 12 may be made as one piece. A handgrip 18 may be mounted to the main beam 12 in any conventional manner chosen with sound judgment by a person of ordinary skill in the art. A trigger mechanism suitable for shooting an arrow is mounted to the main beam 12 in any suitable manner. It should be noted that the crossbow 10 may comprise any trigger mechanism chosen with sound judgment by a person of ordinary skill in the art. The crossbow 10 also includes a bow assembly 30 adapted to propel an associated arrow and having a bow 32 and a bowstring 34. The bow 32 may include a set of limbs 36, 36 that receive the bowstring 34 in any conventional manner chosen with sound judgment by a person of ordinary skill in the art. For the embodiment shown, a pair of wheels, pulleys, or cams 38, 38 mounted to the limbs 36, 36 receive the bowstring 34 in an operational manner. In each of the non-limiting embodiments, the set of limbs has a first limb set 36a and a second limb set 36b opposite the first limb set 36a with first limb set 36a being operationally engaged with a first cam 38 and second limb set 36b being operationally engaged with a second cam 38. The bow may also include a riser 40. The riser 40 may comprise a set of limb pockets 42, 42 adapted to receive the limbs 36, 36, as shown in FIG. 1 with the first limb set 36a engaged to a first riser side 40a and the second limb set 36b engaged to a second riser side 40b. The first limb set 36a may define a first limb axis 492 about which a cam 38 or cam set 240 may be rotatably engaged. The second limb set 36b may define a second limb axis 494 about which a cam 38 or cam set 240 may be rotatably engaged. In the non limiting embodiments shown in FIG. 4 the second limb axis 494 is parallel to the first limb axis 492.
Without limitations, other crossbow components may be optionally used with a crossbow as provided herein. Without limitation, in some non-limiting embodiments, a crossbow 10 shown may include a scope 50 attached to a scope mount 52 that is supported on the main beam 12. Other optional components shown include a cocking unit 56, and arrow holder 58. In certain non-limiting embodiments, the riser 40 may have an opening 72 formed therein defining a foot stirrup 74 adapted for holding and balancing the crossbow by foot.
A crossbow 10 may have a power stroke distance PD. The distance between the pivot axes of the wheels, pulleys, or cams 38, 38 may be some distance WD.
With reference to the non-limiting configurations of cams 38 shown in FIG. 3, a cam 38 may be a planar cam 38a comprising a first cam axis 422, a first cam plane 432 normal to the first cam axis 422, a first cam plate 434. The first cam plate 434 may have a first top surface 436, a first bottom surface 437 opposite the first top surface 436, and a first perimeter surface 438. A first perimeter surface 438 may extend between the first top surface 436 and the first bottom surface 437, the first perimeter surface 438 may define a first concave channel 439 extending around the first cam axis 422 along a first plane curve 412 within the first cam plane 432. The concave channel 439 may be a bowstring channel or a power cord channel. The first plane curve 412 may vary in distance from the first cam axis 422 or may be a constant radial distance from the first cam axis 422. In those embodiments in which the first plane curve is a constant radius distance from the first cam axis 422, the planar cam 38a is round wheel, or section of a round wheel, with the first cam axis 422 coincident with the wheel center. In those embodiments in which the first plane curve 412 varies in distance from the first cam axis 422, the planar cam 38a is a variable radius planar cam 38a. In some non-limiting embodiments, a cam 38 may optionally have an internal securement feature 431 adapted to anchor one end of an engaged bowstring 34 or power cord 252, 262, 272.
With continuing reference to the non-limiting configurations of cams 38 shown in FIG. 3, a cam 38 may be a helical cam 38b comprising a first cam axis 456 about which a first helix curve 454 is defined. The first helix curve 454 may be a cylindrical helix curve or a spiral helix curve. The helix curve 456 may establish a path which a top channel 452 follows. The first helix curve may extend between two end planes 458, 459. In the non-limiting configuration shown in FIG. 3 end plane 458 coincides with first top surface 436. In some non-limiting embodiments, a cam 38 may optionally have an external securement feature 468 adapted to anchor one end of an engaged bowstring 34 or power cord 252, 262, 272.
In some non-limiting embodiments, a cam 38 may be arranged in a cam set 204 with one or more other cams 38 with the surface 436, 437 or end plane 458, 459 of a first cam 38 in contact with the surface 436, 437 or end plane 458, 459 of a second cam 38. In the non-limiting embodiment shown in FIG. 3 a first cam 38 is stacked with a second cam 38 so that the surface 436 is in contact with the end plane 458 of the second cam. While the embodiment shown in FIG. 3 is of one planar cam 38a and one helical cam 38b, other arrangements are acceptable. A cam set 204 can include multiple planar cams 38a, multiple helical cams 38b, or a plurality of both planar cams 38a and helical cams 38b. It is also contemplated that cams 38 may be arranged in a cam set where they are arranged coaxially, such that their axes 422, 456 coincide, but are offset by some margin such that they are not in contact with one another.
As shown in FIG. 2A. In some non-limiting embodiments, a first cam may be engaged with one or more other cams 38 to form a cam set 204. In some non-limiting embodiments, all cams 38 in a cam set 204 are adapted to rotate synchronously about a common axis as shown in FIG. 2A and 2B. In some embodiments in which all cams 38 in a cam set 204 are adapted to rotate synchronously about a common axis all of the cams are fixed with respect to a shaft 137 defining and rotatable about a first cam axis 212. It may be acceptable in some non-limiting embodiments for one or more cams in a cam set to rotate asynchronously with respect to one or more other cams in a cam set 204. The cams in a cam set 204 may be adapted to rotate asynchronously by operationally engaging the cams to one another through a shaft or other element that is adapted to twist sufficiently to be operatively important during operational loading. The cams 38 in a cam set 204 may be adapted to rotate asynchronously by operationally engaging the cams to one another through an epicyclic gearing.
Referring now to FIG. 2A, in a first non-limiting embodiment, a crossbow comprises two cam sets 204, a first cam set 206 and a second cam set 208, wherein each cam set 204 comprises a shaft 137, and three cams 38, including a first power cord cam 222, a bowstring cam 232, and a second power cord cam 242. The first power cord cam 222 in the first cam set 206 may be operationally engaged to a frame 282. The frame 282 may be riser 40, barrel 16, or other component chosen with good engineering judgment. The frame 282 is identical to, or is substantially fixed with respect to, the riser 40. As shown in first non-limiting embodiment depicted in FIG. 2A, power cord 252 is an elongated cord with a first end 254 operationally engaged with the frame 282 and a second end 256 opposite the first end 254 and operationally engaged with the first power cord cam 222 in the first cam set 206. The first power cord cam 222 in the second cam set 208 may be operationally engaged to the frame 282. As shown in first non-limiting embodiment depicted in FIG. 2A, power cord 262 is an elongated cord with a first end 264 operationally engaged with the frame 282 and a second end 266 opposite the first end 264 and operationally engaged with the first power cord cam 222 in the second cam set 208. The second power cord cam 242 in the first cam set 206 may be operationally engaged to the second power cord cam 242 in the second cam set 208 by a power cord 272. As shown in first non-limiting embodiment depicted in FIG. 2A, power cord 272 is an elongated cord with a first end 274 operationally engaged with the second power cord cam 242 in the first cam set 206 and a second end 276 opposite the first end 274 and operationally engaged with the second power cord cam 242 in the second cam set 208. A bowstring 34 is an elongated cord having a first end 34a operationally engaged with the bowstring cam 232 of the first cam set 206 and a second end 34b opposite the first end 34a and operationally engaged with the bowstring cam 232 of the second cam set 208.
In operation, each cam 204 is operationally engaged with a crossbow 10 such that when the bowstring 34 is being cocked, moved from the uncocked position shown in FIG. 1, by being pulled backwards along barrel 16, the applied cocking work causes the bowstring cam 232 at each end 34a, 34b of the bowstring 34 to rotate and for the cam sets 204 to move and flex each engaged limbs 36. All of the cams 38 in any given cam set 204 each rotate synchronously with each other cam 38 in the same given cam set 204. Accordingly, as the cocking operation causes the bowstring cam 232 in the first cam set 206 to rotate, the rotation is imparted synchronously to the first power cord cam 222 and the second power cord cam 242 of the first cam set 206. Similarly, as the cocking operation causes the bowstring cam 232 in the second cam set 208 to rotate, the rotation is imparted synchronously to the first power cord cam 222 and the second power cord cam 242 of the first cam set 208. As the second power cam 242 of the first cam set 206 rotates during cocking, it spools in power cord 272 from its first end 274; as the second power cam 242 of the second set 208 rotates during cocking, it spools in power cord 272 from its second end 276; because power cord 272 is being spooled in at each end 274, 276, the cams 242 pull each other along the power cord 272 and thereby each put a deflecting load on the engaged bow limb 36 in a direction along power cord 272 and toward the opposite cam 242. As the first power cord cam 222 of the first cam set 206 rotates during cocking, it spools in power cord 252 from its first end 256; because power cord 252 is being spooled in at end 256 and is fixed at end 254, the first power cord cam 222 of the first cam set 206 is pulled along the power cord 252 and thereby puts a deflecting load on the engaged bow limb 36 in a direction along power cord 252 and toward the frame 282. As the first power cord cam 222 of the second cam set 208 rotates during cocking, it spools in power cord 262 from its first end 266; because power cord 262 is being spooled in at end 266 and is fixed at end 264, the first power cord cam 222 of the first cam set 206 is pulled along the power cord 262 and thereby puts a deflecting load on the engaged bow limb 36 in a direction along power cord 262 and toward the frame 282.
In some non-limiting embodiments, in the cam set 206, the first power cord cam 222 is a planar cam 38a, the bowstring cam 232 is a planar cam 38a, and the second power cord is a helical cam 38b. In some non-limiting embodiments, in the cam set 208, the first power cord cam 222 is a planar cam 38a, the bowstring cam 232 is a planar cam 38a, and the second power cord is a helical cam 38b.
With reference now to the non-limiting schematic diagram shown in FIG. 4, shown is a schematic of components of a crossbow 10 comprising main beam 12, cam set 206, cam set 208, cams 232, cam 222, cams 242, power cord 272, power cord 252, power cord 262, and bowstring 34. In the non-limiting embodiment shown power cords 252 is connected to frame 282 in such a manner that a plan view of the power cords shows power cord 252 at an angle .Theta 1. with respect to power cord 272. In the non-limiting embodiment shown power cords 262 is connected to frame 282 in such a manner that a plan view of the power cords shows power cord 262 at an angle .Theta 2. with respect to power cord 272. In the non-limiting embodiment shown .Theta 1. is equal to .Theta 2. In other acceptable non-limiting embodiments shown .Theta 1. is not equal to .Theta 2. In some non-limiting embodiments .Theta 1. is adjustable by adjusting the point at which power cord 252 connects to frame 282. In some non-limiting embodiments .Theta 2. is adjustable by adjusting the point at which power cord 262 connects to frame 282.
With reference now to FIG. 2B, in some embodiments, a cam set 204 may comprise a plurality of cams with one or more of the cams 38 offset from one another by one or more margins 292, 294. As shown in FIG. 2B, cam 222 is offset from cam 232 by margin 292, and cam 232 is offset from cam 242 by margin 294. In some non-limiting embodiments, as shown in FIG. 2B, a power cord 295 can be engaged with the cam set 204. In the embodiment shown, the power cord 295 has a first end 297 engaged with an internal securement feature 431 on cam 222, the power cord extends to and loops over a pully 296 engaged with a frame 282 and extends back the cam 223 where a second end 298 of the power cord 295 engages axis 212 or some other feature adapted to secure second end 298 within the margin 292.
Numerous embodiments have been described, hereinabove. It will be apparent to those skilled in the art that the above methods and apparatuses may incorporate changes and modifications without departing from the general scope of the present subject matter. It is intended to include all such modifications and alterations in so far as they come within the scope of the appended claims or the equivalents thereof.
Patent Application
20190162500
