See Application Data Sheet.
Not applicable.
Not applicable.
Not applicable.
Not applicable.
1. Field of the Invention
The present invention relates to compound archery bows, such as bows and crossbows, in particular, to cams for the compound archery bows.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98.
Various designs of cams for compound archery bows are known in the art. Thus, U.S. Pat. No. 3,990,425 describes a bow with a cam comprising two limbs, each limb having a loose end, while the other ends of the limbs are connected with a handle. There are end members installed on the loose ends each of which includes a pulley for a bowstring and attachments for two cables. In the area of the loose end, each limb is divided into two portions with the pulley for the bowstring and the attachments located therebetween. Since the cables and the bowstring form a single continuous string such that the cables are crossed, friction appears between the cables when using the bow causing energy losses of an arrow and rapid wear-out of the cable.
U.S. Pat. No. 5,368,006 discloses a cam for an archery bow with cables and a bowstring being individual members. In the area of a loose end, each limb of the cam is divided into two portions with a pulley for the bowstring and attachments for the cables located therebetween. The cables are located on both sides of the bowstring and close to each other, since the pulley for the bowstring and the attachments, in fact, form a single member. Close positioning of the cables to the bowstring causes the cables to interfere with an arrow during a shot, thus requiring additional means to be used to retract the cables from the bowstring. Furthermore, like in the above case, the cables are crossed, resulting in friction energy losses and wear-out of the cable.
In a cam disclosed in U.S. Pat. No. 7,441,555, a bowstring is also located between two cables. However, in order to minimize the disadvantages of the cam of the U.S. Pat. No. 5,368,006, a portion of a limb is located between a pulley for the bowstring and each of attachments for the cables. This design suffers from an inconvenient way to set an arrow which is to be placed into the area confined by the cables going in parallel to the bowstring and on both sides thereof when the cam is in a free condition.
The closest prior art to the claimed invention is a cam for a compound archery bow according to patent application US20100206284. The application combines the advantages of the above bows and cams, namely, teaches cables to be located on the one side of a bowstring and being individual members. This is achieved by making such an end member which attachments for the cables are separated from a pulley for the bowstring and located on the one side of the pulley for the bowstring. However, this cam has a significant disadvantage that the cams according to U.S. Pat. No. 7,441,555 and U.S. Pat. No. 5,368,006 lack. Since in the US20100206284 the pulley for the bowstring is located not between the attachments for the cables but aside of them, and when pulling, a travel of the bowstring slightly exceeds a travel of the cables, lateral load appears acting on an axis supporting the pulley for the bowstring and the attachments for the cables. When the bowstring is strained, said axis tends to misalign thus causing increased wear of areas where end members are attached to loose ends and a stricter requirement to manufacturing quality of the axis, the pulley for the bowstring, the attachments for the cables and portions of limbs.
The invention is aimed at designing a cam for compound archery bows that eliminates the disadvantages of the cams known in the art including those described above.
The invention provides convenient operation of the compound archery bow, increased initial speed of an arrow when shooting, and increased strength and reliability of the cam.
This is achieved in a cam for a compound archery bow that includes a first limb, a second limb, a first end member and a second end member installed on loose ends of the first limb and the second limb, respectively, and connected by a bowstring and a first cable and a second cable. In the area between the loose ends of the first limb and the second limb, the first cable and the second cable are located on the same side of the bowstring. The first end member and the second end member include a first pulley and a second pulley for the bowstring, respectively, and a first attachment and a second attachment for the first cable and the second cable, respectively. The bowstring is partially located on peripheral surfaces of the first pulley and the second pulley. The first limb and second limb each consists of at least two portions. At least one of the portions of the first limb is located between the first pulley and at least one of the first attachment for the first cable and the first attachment for the second cable. At least one of the portions of the second limb is located between the second pulley and at least one of the second attachment for the first cable and the second attachment for the second cable.
The cam addresses several issues faced by developers in the art, namely, increasing shooting comfort by locating both the cables on the same side of the bowstring, eliminating any contact between the cables, and substantially decreasing lateral loads on axes supporting the first end member and the second end member.
Further improvements of the claimed cam for compound archery bows are possible.
In particular, all attachments for the cables or only some of them can be made as a pulley having a peripheral surface where the respective cable is partially located, or said attachments can be made in the form of a fixing means.
Preferably, the first attachment and the second attachment for the first cable are located closer to the first pulley and the second pulley for the bowstring, respectively, than the first attachment and the second attachment for the second cable.
To further compensate forces acting on the axes due to different strain of the bowstring and the cables, it is preferable when at least two portions of said at least two portions of the first limb have various resilience properties. In a similar way, it is preferable when at least two portions of said at least two portions of the second limb have various resilience properties. In a particular case, resilience properties of the first limb and the second limb being an extension of each other are the same.
In a particular embodiment, the first pulley and the second pulley are separated from the respective first attachment and the second attachment with one portion of each of the first limb and the second limb, and there are no limbs between the first attachment and the second attachment. Either two portions of the first limb and the second limb surrounding the first pulley and the second pulley or the first attachment and the second attachment can be used, or rather three portions of the first limb and the second limb can be used, located above (in front of) the pulleys for the bowstring, between the pulleys for the bowstring and the first attachment and the second attachment, as well as beneath (under, or behind) the first attachment and the second attachment.
In another embodiment, the first attachment and the second attachment of the first cable are separated from the first attachment and the second attachment of the second cable, respectively, with at least one portion of the first limb and the second limb, respectively. There can also be another pair of portions each installed above the first pulley and the second pulley.
In yet another embodiment, the first pulley and the second pulley for the bowstring are separated from the respective attachments with at least two portions of each of the first limb and the second limb.
There are also other embodiments possible as discussed in detail below.
The claimed cam for compound archery bows can be used both in a bow and in a crossbow, since a design of the cam is suitable for both said arrow throwing devices.
The invention is further explained with references made to the figures that represent some possible embodiments.
The proposed cam can be used in an arrow throwing device, in particular, in a bow (
According to some embodiments of the invention, the limb 3 and the limb 4 comprise two portions—portions 3a, 3b and portions 4a, 4b, respectively. For the limb 3, this is schematically shown in
The portions 3a, 3b, 3c and the portions 4a, 4b, 4c may extend to the entire length of the limbs 3, 4, which, for instance, corresponds to the embodiments of the bow 1 and the cross-bow 2 as shown in
In the area between the loose ends of the first limb 3 and the second limb 4, the first cable 12a and the second cable 12b are located on the same side of the bowstring 11. It means that projections of the first cable 12a and the second cable 12b onto a first plane, the first plane going through the bowstring 11 and being perpendicular to a second plane where the limbs 3, 4 lie, are located on the same side of a projection of the bowstring 11 onto said first plane.
The limbs 3, 4 can be made such that at least two of the portions 3a, 3b (if there are two portions) or of the portions 3a, 3b, 3c (if there are three portions) and of the portions 4a, 4b (if there are two portions) or of the portions 4a, 4b, 4c (if there are three portions), respectively, have different resilience. For example, the portions 3a and 3b have different resilience, or the portions 3a and 3b have similar resilience but different from that of the portion 3c. The portions of the limbs 3, 4 which represent an extension of each other, such as the portions 3a and 4a, or the portions 3b and 4b etc., may preferably have similar resilience.
Referring to the portions 3a, 3b of the limb 3 having different resilience, in this invention the terms “different resilience” or “different resilience properties” mean that the portion 3a and the portion 3b bend to different angles when exposed to the same loading applied to each of the portions 3a and 3b.
Different resilience of the portions 3a, 3b of the limb 3 can be ensured by various designs of the portions 3a, 3b. For example, the portions 3a, 3b can be made of materials having different mechanical properties responsible for their flexibility, resilience, rigidity etc. It is also possible that the portions 3a, 3b are made of the same material but have cross-sections of different shapes, for example, at least in the area of the first loose end of the limb 3 the portion 3a is narrower or wider than the portion 3b.
The attachments 9, 10 for the cables 12a, 12b may be made in the form of pulleys or fixing means. For example,
As known to the one skilled in the art, the pulleys 7, 8 for the bowstring 11 and the pulleys used as the attachments 9, 10 for the cables 12a, 12b can be of round, elongated or complex shape. Said pulleys can be installed on the axis 13a and/or the axis 13b in centers thereof (a geometric center, or a mass center of the pulley), or shifted, i.e., installed eccentrically. Designs of the pulleys and installation options thereof are disclosed in the above cited prior art documents.
Usually, pulleys installed on the same axis are rotated simultaneously. When armed, a bowstring is strained and the pulleys for the bowstring start unwinding, releasing the bowstring partially located on peripheral surfaces of the pulleys. A torque appeared is transmitted to the pulleys for cables (if attachments for the cables are made in the form of a pulley), and each cable starts winding on the pulley for the cable.
The pulley for the bowstring and the pulleys for the cables are rigidly coupled. All the pulleys can be rigidly attached to the axis and rotate together therewith, or all the pulleys can be made as an integrated unit installed on the axis and rotating irrespectively of the axis, e.g. as shown in FIG. 5 of the U.S. Pat. No. 7,441,555. If the pulleys rotate around the axis, the axis itself needs not necessarily rotate along with the pulleys. Both ends of the cable are wound only when the pulleys are used as the attachments on both loose ends.
Unlike the pulleys, fixing means allow the ends of the cable to roll on the axis even if the pulleys for the bowstring are rigidly secured to the axis. When the fixing means is used as the attachment on one end of the cable, this one end will not be wound when the axis rotates. In general, the fixing means may be avoided at all by simply fastening the end of the cable to the axis, so in this application the fixing means shall be understood in a broad sense: as a means for attaching the end of the cable to the axis, or as a method for such attaching, for example, by knotting the end of the cable or securing the end of the cable with a clamp or the like.
Furthermore, like in the cams known in the art, this invention allows locating the attachments made as the fixing means spaced from the axes. For example, the end of the cable can be secured directly to a limb or to a portion of the limb.
According to the present invention, there is at least one portion of the limb 3 located between the pulley 7 and at least one of the attachments 9a and 9b. Similarly, there is at least one portion of the limb 4 located between the pulley 8 and at least one of the attachments 10a and 10b. There are various designs possible that are given in
As
Since the distance between the pulley 7 and the attachment 9b is rather high, different straining forces of the bowstring 11 and the cable 12b will result in appearance of a torque moment acting on the axis 13a tending to turn the axis 13a clockwise or counterclockwise in the drawing's plane in
As preliminary tests of the claimed cam have shown, when using the pulley 7 and the attachments 9a, 9b spaced from each other and when the cables 12a and 12b are located on the same side of the bowstring 11, this is the limb 3 consisting of the two portions 3a and 3b or more and designed such that there is at least one of the portions 3a, 3b (the portion 3a in this embodiment) located between the pulley 7 and at least one of the attachments (the attachment 9b in this embodiment) that allows significantly reducing said undesirable effect.
To further reduce the above undesirable effect it is not strictly necessary but preferably for the portions of the limbs to have different resilience (or resilience properties). According to the above example, the portion 3a and the portion 3b of the limb 3 may have different resilience. The one skilled in the art will understand that specific values of resilience for the portions 3a, 3b will depend on performances of the bowstring 11 and the cables 12a, 12b, lengths of the portions 3a, 3b, straining force of the bowstring 11, using the pulleys or the fixing means as the attachments, etc.
Also, the one skilled in the art will understand that it is practicable, though not strictly necessary, to choose the same resilience of the portions 3a and 4a that extend each other, and the same resilience for the portions 3b and 4b. Nevertheless, it is permitted to use the portions 3a and 4a and/or the portions 3b and 4b having different resilience.
The above conditions concerning location and resilience of the portions 3a, 4a and the portions 3b, 4b of the respective limbs 3, 4 are applicable to all other embodiments according to
An alternative to the embodiment given in
Yet another alternative to the embodiments given in
The embodiment given in
According to
The embodiment given in
When using the portions 3a, 3b, 3c at least two of which have different resilience, the embodiments according to
Another embodiment of the cam according to this invention that differs from the described above is given in
It is understood that the embodiment according to
It should be noted that the embodiments in which the attachments 9a and 9b as well as the attachments 10a and 10b are not separated with any portions of the limbs 3, 4, which corresponds to
For the one skilled in the art it will be clear that in the embodiments shown in
Thus, the present invention provides for a solution for several problems at the same time that are encountered by those who develop cams for compound archery bows, namely:
Number | Name | Date | Kind |
---|---|---|---|
3990425 | Ketchum | Nov 1976 | A |
5368006 | McPherson | Nov 1994 | A |
6474324 | Despart | Nov 2002 | B1 |
7441555 | Larsen | Oct 2008 | B1 |
8281775 | Larson | Oct 2012 | B1 |
8443791 | Miller | May 2013 | B2 |
20060011190 | Andrews | Jan 2006 | A1 |
20100206284 | Popov et al. | Aug 2010 | A1 |