Patent Application
20150285582
1. Field of the Invention
The present invention relates to a crossbow, and more particularly to a crossbow with a bow string set having take-up cables higher than a let-off cable thereof.
2. Description of the Related Art
One type of compound bow is illustrated in U.S. Pat. No 3,486,495 (1969). In this bow, rotatable, variable leverage pulley members are equipped on the tips of the bow limbs. A bowstring is wound over the pulley members to provide mechanical advantage, and less force is required to hold the bowstring in a fully drawn position than to hold the bowstring at an intermediate draw position. Similar to the compound bow, a crossbow also employs the pulley members to provide similar functions.
Specifically, the let-off cable 970 has opposite end portions respectively trained about the two primary wheels 951, 961 of the eccentric pulleys 95, 96. Each of the take-up cables 971 or 972 has one end trained about one of the secondary wheels, and the other end anchored to the other secondary wheel. The two take-up. cables 971, 972 are positioned at a height substantially lower than the let-off cable 970 and intersect with each other at the stock 91. In order to avoid interrupting the launching of the projectile, a slot 910 is defined in a front of the stock 91 so as to permit the take-up cables 971, 972 to pass therethrough and keep away from a launching path of the bow.
However, this configuration has disadvantages in that the slot 910 would have to be specially formed, thus raising the cost of the bow and lessening the strength of the front of the stock 91. This would further cause a lower collimation degree of the track 910 of the stock 91 by which the launching of the projectile would be adversely affected. In addition, the front of the stock 91 would have to be thick enough for the forming of the slot 910, thus raising the weight of the bow.
Accordingly, it is an object of the present invention to provide a crossbow to solve the aforementioned problems. The crossbow includes a stock, a riser disposed at a front of the stock, a pair of limbs attached to opposite ends of the riser, first and second pulleys respectively mounted on rear tips of the limbs, and a bow string set. The stock has at its top a track for receiving a projectile and at its bottom a trigger for launching the projectile. Each of the first and second pulleys includes a primary wheel and a secondary wheel adjacent to the primary wheel. The bow string set includes a let-off cable, a first take-up cable and a second take-up cable. The let-off cable extends across the track of the stock and is located at a height above the track of the stock. Moreover, the let-off cable has opposite ends respectively trained about the primary wheels of the first and second pulleys. The first take-up cable extends across the track of the stock with one end strung about the secondary wheel of the first pulley and the other end anchored to the second pulley. Similarly, the second take-up cable extends across the track of the stock with one end strung about the secondary wheel of the second pulley and the other end anchored to the first pulley. In particular, the first and second take-up cables are both substantially positioned higher than the let-off cable.
Preferred embodiment of the invention may have the following additional characteristics, either alone or in combination:
The crossbow further comprises a retaining rod positioned in between the first take-up cable and the let-off cable to lift up the first take-up cable to the height above the track of the stock. In one embodiment, the retaining rod has one end secured to the riser and the other end extending in between the first take-up cable and the let-off cable.
Further benefits and advantages of the present invention will become apparent after a careful reading of the detailed description with appropriate reference to the accompanying drawings.
In the accompanying drawings, a crossbow 100 is illustrated which includes a stock 1, a riser 2 disposed in a front of the stock 1, a pair of limbs 3, 4 connected at their front ends in fixed relation to the riser 2, first and second pulleys 5, 6 respectively mounted on rear tips of the limbs 3, 4, a bow string set 7 connecting the two pulleys 5, 6, and a stirrup 8.
As shown in
Referring to
Preferably, a pair of parallel retaining rods 21, 22 may be employed to lift up the first and second take-up cables 71, 72 to the height above the track 10 of the stock 1, as best seen in
It is noted that although the retaining rods 21, 22 are shown in the preferred embodiment to be secured to the riser 2, the retaining rods 21, 22 may be in other embodiments secured to the stock 1 or other portions. It is also noted that, although the first and second pulleys 5, 6 shown in the preferred embodiment are both eccentric pulleys, any type of pulleys may be used as dictated by the convention. For example, one may be idle while the other be an eccentric pulley.
It is to be understood that the disclosed embodiments are illustrative in nature and the invention is not to be limited to any one or more embodiments except as set forth in the following claims.
