The present invention generally relates to archery bows. More specifically, the present invention relates to archery bows using cams.
Most compound bows attach the cams to the end of the bow limbs. With the cams at the end of the bow limbs there has an increase in bow speed, but over the past 10 years arrow speeds have not exceeded the 350 fps. There seems to be a limit based on the size of the cams and the amount of energy they can store, based on how much energy an archer can put into the draw of the bow. 80 lbs is usually the limit for bow manufacturers. Only a very small percentage of archers can pull an 80 lb bow through current cam systems on a bow. Most use hunting bows are in the 50 to 60 lb range. The advertised high speeds are only for the very few. More and more efficient cams are designed and introduced to the archery market. But because of the way the components are arranged on a bow, none have overcome the limit of 350 fps. The problem is that the size of the cam on the bow limb is limited for various reasons. The extreme acceleration and deceleration involved by placing cams on the ends of the bow limb limit the size and weight of the cam, which must survive the constant shock resulting from being mounted on the end of the bow limb when it is shot. Also adding extra weight to the end of a bow limb gets into “polar moment of inertia” issues. The more mass placed on the end of the bow limb will increase the resistance to acceleration as well as require heavier more durable mounting materials which would in turn increase the polar moment of inertia issue.
It is an object of the present invention to provide an archery bow that is easier to use.
The present invention is a riser cam bow with an independent timing cam system for archery. The present invention addresses this issue by removing the cams from the bow limb and mounting them on an appendage incorporated into the riser.
The present invention is a riser cam bow with an independent timing cam system for archery. The present invention addresses this issue by removing the cams from the bow limb 10 and mounting them on an appendage 12 incorporated into the riser 14, as show in
The cams of current compound bows consist of two parts, a large cam that the bowstring connects to and a smaller cam that connects to the bow limb. The cams use a timing system where the cam on one bow limb is connected to the opposing bow limb with a cable. Cross connecting of cables cause problems in the performance of bows. Since the cables cross directly in the path of where the arrow travels, they require a cable guard system that draws the cables out of the way of the path of the arrow. This creates a tuning issue where the angular pull on the cams located at the end of the bow limbs tends to cause cam lean and reduces the performance and accuracy of the bow. The angled timing cables in turn cause a bow to torque along its vertical axis when it is shot, reducing accuracy. The present invention reconfigures the entire cam system into a more direct and simple method. The riser cam bow includes a large bowstring cam 16 for the bowstring on each appendage 12 and two matching power cams 18 mounted on either side of the bowstring cam 16. The power cams 18 attach to the nearest bow limb 10 rather than to the opposing bow limb 10. The bowstring cam 16 and power cam 18 are mounted to an axle 20, along with a timing wheel 22 attached to one end of the axle 20. The bowstring cam 16, power cams 18, timing wheel 22 and axle 20 are mounted onto the appendage 12 of the bow using a bearing system to form a limb cam unit. The limb cam unit has all of its parts locked in unison and is mounted in a forked appendage 12 of the riser so that it rotates as a result of bearings supporting the axle 20 in the forks. The timing system of the riser cam bow uses two timing wheels 22 attached to the axle 20 of each limb cam units and linked by a timing belt 23 with teeth. The belt 23 has a single twist in it that enables the limb cam units to rotate in opposite directions. This timing system keeps the cams synchronized independently of the other bow components. Since timing system is independently synchronized, there is only a need to attach simple cables from the power cam 18 directly to the bow limb 10, with no pulleys on the bow limb 10. The timing system of the riser cam bow eliminates the need for cross cables and all the issues of cable wear and stretch and synchronization. This system allows the timing belt to be out of the path of the arrow without distorting any forces and eliminates the total cross cabling found in current compound bows and also eliminates the cable guard entirely.
The drawstring 24 on the riser cam bow is a simple bowstring like found on longbows and recurve bows. Just a string with two loops connected to the bowstring cams 16, instead of the complex cables and Y harnesses of conventional compound bows. The cables 26 that attach to the bow limbs 18 are smaller bow strings, which are just short strings with loops at each end. The drawstring 24 rotates the bowstring cam 16 when pulled, but has no influence on the timing. Even if you pull the drawstring 24 from a point that is not centered, the power cams 18 will compress the bow limbs 10 equally. Even if one bow limb 10 is disconnected from the system and the drawstring 24 is drawn, the remaining bow limb 10 is compressed, as if the disconnected limb 10 was attached. When the drawstring 24 is released, the energy from each bow limb 10 is equally applied to the drawstring 24 because of the power cams 18 being synchronized to each other by the timing belt.
With most conventional compound bows, “cam lean” is a big issue. Cam lean happens when the Y cables attached to the cam axle are not adjusted equally, allowing the bow limb to twist and result in a decrease in accuracy. The cams on riser cam bow eliminate the issue of cam lean, because of their placement on the rigid riser instead of the bow limbs. The cam system of the present invention allows for changing the performance of the bow by simply removing the two power cams from the bowstring cam and replacing them with a different size or shape power cam. Depending on performance requirements of the shooter soft, medium, or hard setting cams can simply be bolted to the large drawstring cam. Virtually any modern cam design existing in the industry could be adapted to work on this system. The riser cam bow can be maintained by most archers without any special tools or equipment, because of its simplicity. In the manufacturing process the simplicity of construction of the riser cam bow reduces manufacturing costs, as well as the simplicity of the bowstrings and cam cables reduces production costs.
Nock travel is a problem found in most modern compound bows, as a result of either improperly timed cams or stretching of cables that cause vertical nock movement when the bow is shot or lateral nock movement as a result of the timing cables being pushed off center by the cable guard which causes the bow to torque when shot. The system of the riser cam bow prevents the vertical nock movement with the timing belt and because there is no cable guard involved, lateral nock movement is prevented. This is because the components of the riser cam bow are aligned with the center axis of the riser 14 and the power cables 18 are symmetrically balanced on either side resulting in all of the forced directed along the center line on the riser cam bow. The riser cam bow includes a draw stop. The draw stop uses a pin on the large cam that comes in contact with a block on the riser appendage that holds the cam. This insures a consistent draw every time the bow is shot. The point on the timing belt where there is contact due to the twist could reduce the bow speed. Therefore, both parts of the timing belt is wrapped with a split belt tube composed of nylon, teflon, or some type of friction reducing plastic. The belt tubes are secured to the timing belt so that they do not move. The belt tubes are long enough to travel up and down against each other when the bow is drawn and released in order to prevent the rubber belt from contacting itself to reduce wear and friction.
Each cam-timing assembly includes a timing wheel 228, bowstring wheel 230, cam 232 and driveshaft 234. The driveshaft 234 mounts to between two driveshaft brackets 236 that extend from the riser 202. The two driveshaft brackets 236 act as parallel legs from the riser 202. The driveshaft 234 is mounted such that the driveshaft 234 can rotate between the driveshaft brackets 236. The cam 232, timing wheel 228 and bowstring wheel 230 are attached to the driveshaft 234, as shown in
The first timing wheel 228A and the second timing wheel 228B are interconnected to a first timing cable 246 and a second timing cable 248, as shown in
The second timing cable 248 includes a first cable loop 254 that is attached to a second cable retainer 256 on the second timing wheel 228B in a fixed retainer slot 258, where the second cable retainer 256 is shown as a loop hook, as shown in
The operation of the embodiment of the riser cam bow 200 is as follows. The bowstring wheels 230, cams 232, and timing wheel assemblies are mounted on ends of the riser 202. The timing wheels 228 on the end of each driveshaft 234 are synchronize with a crossed set of timing cables 246, 248. The placement of the timing wheels 228 on the outside of the drive shafts 234 provides clearance for launching arrows without having any timing cables that run thru a complicated series of pulleys or cam lean that is found in most compound bows using a cam to bow limb timing system. Where each timing cable 246, 248 is directly connected between the two timing wheels 228. When the bowstring 244 is drawn by the user, the bowstring wheels 230, cams and timing wheel assemblies act in unison to draw and launch an arrow with consistent dead level launches. With the cam 232 not being mounted on the bow limb 212 as in conventional compound bows, the riser cam bow 200 makes very little noise and has virtually no vibration as a result of the cams being stationary and only rotating as the bowstring 244 is drawn and fired. Virtually all compound bows connect a cam to an opposing bow limb using a bow limb cable to keep the bow limbs synchronized and provide a straight line of thrust to the arrow. The problem with this system is that the bow limb cables must be separated from the bowstring to provide clearance for arrows to pass and this leads to tuning issues and synchronization issues. In the present invention, the timing wheel 228 to timing wheel 228 using timing cables 246, 248 that have a direct path to each timing wheel 228 with no other pulleys in between and eliminates cable clearance issues by separating the timing wheels 228 out on the driveshaft 234. As the user draws the bowstring 244, the bowstring wheels 230 rotate, which rotates the cams 232 to wind the bow limb cable 238, which pulls on and compresses the bow limbs 212 in a loaded condition. The timing wheels 228 with the crossed timing cables 246, 248 keeps the two assemblies of the bowstring wheel 230 and cams 232 synchronized. As the bowstring 244 is released the energy from the bow limbs 212 unloading and pulling on the bow limb cables 238 rotates the cams 232 and hence rotates the bowstring wheels 230 to launch the arrow. Most conventional cam to bow limb synchronized bows have issues with level arrow travel, whereby when bowstrings wear and stretch, the timing is affected. The riser cam bow 200 of the present invention does not go out of synchronization. Even if the bowstring 244 stretches the riser cam bow 200 will still be synchronized due to having the timing wheels 228 and cams 232 as presented, whereby the riser cam bow 200 would simply loose speed which can be adjusted by using the bow limb adjustment. The riser cam bow 200 with the cam-timing assemblies of the timing wheel 228, bowstring wheel 230, cam 232 and driveshaft 234 can be utilized on any kind of bow for shooting arrows, including a crossbow. Also, the bow limb can come off the riser in a manner where the ends connected to the cams are outward from the riser instead of the reverse manner shown in the
While different embodiments of the invention have been described in detail herein, it will be appreciated by those skilled in the art that various modifications and alternatives to the embodiments could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements are illustrative only and are not limiting as to the scope of the invention that is to be given the full breadth of any and all equivalents thereof.
This application is a Continuation In Part of U.S. application Ser. No. 14/712,226 and claims the benefit of and incorporates by reference U.S. application Ser. No. 14/712,226 filed May 14, 2015 and U.S. Provisional Application No. 61/993,625, filed May 15, 2014.
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Number | Date | Country | |
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61993625 | May 2014 | US |
Number | Date | Country | |
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Parent | 14712226 | May 2015 | US |
Child | 15698718 | US |