WO2001094870A1

WO2001094870A1 - Crossbow with adjustable limbs

Info

Publication number: WO2001094870A1
Application number: PCT/AU2001/000682
Authority: WO
Inventors: David Middleton; Bryan Walters; Mike Jennings; Ken Bloom
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-06-08
Filing date: 2001-06-08
Publication date: 2001-12-13
Anticipated expiration: 2002-12-08
Also published as: AUPQ805800A0

Abstract

A crossbow includes stock (28); resilient limbs (11, 12) and adjustment member (32). Limbs (11, 12) are pivotally connected to base (13) by way of pins (14, 15) and are further supported by pins (16, 17) located in channels (18, 19). Limbs (11, 12) are also connected to arms (20, 21). Rotation of adjustment nut (27) causes arms (20, 21) and limbs (11, 12) to move and results in pins (16, 17) sliding in channels (18, 19). Movement of limbs (11, 12) varies the distance between ends (30, 31) of limbs (11, 12) and hence varies the tension in bowstring (19) attached adjacent ends (30, 31).

Description

Crossbow with adjustable limbs

Field of the invention

The invention relates to a crossbow. More particularly, the invention relates to a crossbow having adjustable limbs.

Background of the invention

In this specification, where a document, act or item of knowledge is referred to or discussed, this reference or discussion is not an admission that the document, act or item of knowledge or any combination thereof was at the priority date: (i) part of common general knowledge; or

(ii) known to be relevant to an attempt to solve any problem with which this specification is concerned.

US Patent Number 5445139 concerns a means of increasing the tension on a crossbow after it has been cocked by use of a hydraulic or pneumatic pump to bend the arms of the bow. This is a complicated system.

US Patent Number 4388914 and US Patent Number 5619979 concern devices referred to as crossbows in which the motive energy is stored in a spring which is connected to pivoting rigid arms which carry the bow string. There is no apparent provision for adjusting the bow. US Patent Number 4545358 concerns a crossbow in which the arms may be folded for storage. However, the arms do not appear to be adjustable in use.

Object of the invention

It is an object of the present invention to provide a cross bow in which the limb positions may be adjusted. Summary of the invention

The present invention provides in one embodiment a crossbow comprising: (a) a stock; (b) a pair of opposed, resilient limbs pivotally mounted on the stock and extending laterally from the stock, the limbs being connectable at their free ends to a bowstring; and

(c) an adjustment member mounted on the stock to cause at least one of the resilient limbs to move to vary the distance between the free ends of the limbs whereby to vary the tension in the bowstring.

Preferably, the adjustment member is adapted to move the limbs substantially simultaneously to vary the distance between the free ends of the limbs whereby to vary the tension in the bowstring. The stock according to the invention may take any suitable form. The stock typically includes stock components including a barrel, a launch track, a butt and a sight as are known in the art. The end of the stock nearest to the points of attachment of the limbs is referred to as the forward end of the stock in this description.

Opposed, resilient limbs according to the invention may take any suitable form. Typically the limbs are identical in construction or form a pair of mirror images. Each limb preferably comprises an elongated arm. The arm may be solid. It may be tubular. The limbs may have a degree of flexibility, particularly in the region of the free ends of the limbs, to facilitate drawing of the bowstring. Each limb preferably tapers slightly outwardly in the region of its free end, terminating in a connection arrangement for the bowstring. The ends of the limbs mountable on the stock are in one preferred embodiment substantially at right angles to the longitudinal axis of the stock.

The manner in which the limbs are mountable on the stock may take any suitable form. The arrangement of the limbs is preferably such that they are capable of movement toward and away from one another. The limbs are pivotably mounted on the stock. In one embodiment the stock includes a support on which the limbs are pivotably mounted. The support is preferably disposed at a forward end of the stock. The support may comprise a plate. The plate may be attachable to the stock or integral with the stock. In a particularly preferred embodiment each limb is pivotably attached to the support on either side of the longitudinal axis of the stock. The limbs and the support may include a complementary guide arrangement for each limb providing a guideway for the limbs during a limb adjustment operation. The guideway may define a variety of relative angular positions for the limbs between a rest position where the limbs are in substantial parallel alignment with the longitudinal axis of the stock and an extended position where the free ends of the limbs are farthest apart from one another. The guide arrangement may take any suitable form. In one embodiment the guide arrangement comprises a two-component arrangement having as a first component a projection and as a second component a channel to receive the projection. The projection is typically movable in or relative to the channel. In this embodiment the projection may include a flange or other holding arrangement to provide a sliding surface for the projection relative to an edge of the channel and to prevent the projection from separating from the recess during a limb adjustment operation.

The channel may be curved to define a curved guideway for each limb. In one particularly preferred embodiment the channel comprises an arcuate aperture, and in particular the channel is shaped so as to conform to the locus described by the projection as the limb moves or is adjusted.

In one embodiment the first component is carried by the limb and the second component is carried by the support in the form of a plate. In one particularly preferred embodiment the support comprises a plate having opposed arcuate apertures disposed one on either side of the longitudinal axis of the stock in which a projection carried by a respective limb is receivable and movable relative thereto.

In one particularly preferred embodiment a limb according to the invention comprises an elongate arm having one of its ends substantially perpendicular to the longitudinal axis of the arm, the end of the elongate arm being provided with a projection to engage an aperture formed in the plate, and the end of that part of the arm which is substantially perpendicular to the longitudinal axis of the arm being provided with a pivotal attachment for pivotable mounting to the plate.

The adjustment member according to the invention may take any suitable form. In one embodiment the adjustment member comprises a mounting block connectable to each limb and movable so as to move the limbs relative to each other. The mounting block is preferably movable along the longitudinal axis of the stock whereby to vary the distance between the free ends of the limbs. The connection between the mounting block and the limbs is preferably by means of a pair of opposed arms connected to both the mounting block and the limbs at each end of the arms. The arms may be detachable from the limbs and/or the mounting block to enable the limbs to be brought to a rest position where the limbs are in substantial parallel alignment with the longitudinal axis of the stock.

The mounting block may be pivotably connected to the limbs to facilitate relative movement of the limbs with respect to one another. The mounting block may be mounted on a shaft and be movable relative to the shaft. The shaft preferably extends along the longitudinal axis of the stock. The shaft may be threaded. The mounting block may include a threaded insert to facilitate movement of the mounting block relative to the tlireaded shaft. The shaft may include an adjustment means for example a nut, preferably at one end thereof.

The adjustment member preferably also includes fixing means to fix the positions of the limbs following an adjustment operation. The fixing means may take any suitable form. Where the mounting block is provided with a tlireaded insert, the insert may act as a fixing means for the mounting block.

The adjustment member may be attached to the stock at a forward end of the stock or it may be integral with the stock at the forward end of the stock.

The adjustment member may include an indexing marker to indicate increments of string tension. In one embodiment the indexing marker comprises a rod having a longitudinal axis that is substantially parallel with the longitudinal axis of the shaft on which the mounting block is mounted.

The invention is considered by the Applicant to provide a crossbow with adjustable limbs whereby the power level of the crossbow can be continuously altered via a simple to construct and easy to use mechanism. Constructions and arrangements according to the present invention are thought to enable variable angling of the limbs to provide a wide range of stored energy levels.

Description of the drawings

The invention will now be further explained and illustrated by reference to the accompanying drawings in which:

Figure 1 is a bottom view of a crossbow according to the invention; and Figure 2 is a top view of the crossbow in Figure 1.

Figure 3 is a perspective view of a variant of the crossbow with the resilient limbs, stock and string removed.

In the drawings, a crossbow 10 is shown that has basically three assembly portions, the stock 28, the resilient limbs 11, 12 and the adjustment member 32.

Limbs 11, 12 are pivotally connected to a base 13 via pins 14, 15. Limbs 11, 12 are further supported by pins 16, 17 which move in channels 18, 19.

Limbs 11, 12 are connected by bolts to arms 20, 21. Arms 20, 21 are selectively connected to moving element 22. Moving element 22 is supported by rods 23, 24, and 25. Moving element 22 is movable along rods 24, 25 without interruption. Rod 23 is threaded and engages with a threaded aperture in moving element 22. There is a stopping block 26 and adjustment nut 27 at the end of rod 23. In a preferred embodiment, at least one of rods 24, 25 has index marks along its length which indicate increments of string tension.

When a person turns adjustment nut 27 causing rod 23 to rotate, moving element 22 is moved incrementally along rod 25. Movement of moving element 22 causes limbs 11, 12 to move and thereby varies the tension of a string 29 attached adjacent the ends of the limbs 30, 31.

Arms 20, 21 are selectively connected to moving element 22 in such a manner that arms 20, 21 can be disconnected and the limbs folded alongside the stock 28 of the crossbow 10 for more compact storage.

The word 'comprising' and forms of the word 'comprising' as used in this description does not limit the invention claimed to exclude any variants or additions.

Modifications and improvements to the invention will be readily apparent to those skilled in the art. Such modifications and improvements are intended to be within the scope of this invention.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A crossbow comprising:

(a) a stock;

(b) a pair of opposed, resilient limbs pivotally mounted on the stock and extending laterally from the stock, the limbs being connectable at their free ends to a bowstring; and

(c) an adjustment member mounted on the stock to cause at least one of the resilient limbs to move to vary the distance between the free ends of the limbs whereby to vary the energy stored in the limbs.

2. A crossbow as in claim 1 wherein the adjustment member is adapted to move the limbs substantially simultaneously to vary the distance between the free ends of the limbs whereby to vary the tension in the bowstring.

3. A crossbow as in claim 1 wherein the distance between the free ends of the limbs can be varied in a substantially continuous manner.

4. A crossbow as in claim 1 wherein the stock includes a support disposed at a forward end of the stock on which the limbs are pivotably mounted.

5. A crossbow as in claim 7 wherein the support comprises a plate which is attachable to the stock or integral with the stock.

6. A crossbow as in claim 7 wherein each limb is pivotably attached to the support on either side of the longitudinal axis of the stock.

7. A crossbow as in claim 7 wherein at least one of the limbs is provided with a projection, and the support is provided with a channel to receive the projection such that the channel acts as a tracking radius for the limb.

8. A crossbow as in claim 7 wherein a restraining member prevents the projection from becoming disengaged from the channel.

9. A crossbow as claim 1 wherein the adjustment member comprises a mounting block connectable to each limb and movable so as to move the limbs relative to each other.

10. A crossbow as in claim 12 wherein the mounting block is movable along the longitudinal axis of the stock whereby to vary the distance between the free ends of the limbs.

11. A crossbow as in claim 12 wherein the mounting block is connected to the limbs by means of a pair of opposed arms connected to both the mounting block and the limbs.

12. A crossbow as in claim 14 wherein the arms are pivotally connected to the limbs.

13. A crossbow as in claim 14 wherein the arms are detachable from the limbs and/or the mounting block.

14. A crossbow as in claim 12 wherein the mounting block is moveably mounted on a shaft which extends along the longitudinal axis of the stock.

15. A crossbow as in claim 17 wherein the shaft is threaded and the mounting block has a threaded insert to receive the threaded shaft.

16. A crossbow as in claim 18 wherein the shaft includes an adjustment member threaded upon the tlireaded shaft.

17. A cross bow as in claim 12 further comprising an indexing marker in the form of a rod having a longitudinal axis substantially parallel with the longitudinal axis of the shaft on which the mounting block is mounted.

18. A crossbow comprising : (a) a stock;

(c) an adjustment member mounted on the stock to move the limbs substantially simultaneously to vary the distance between the free ends of the limbs whereby to vary the energy stored in the limbs.

19. A crossbow comprising: (a) a stock; (b) a pair of opposed, resilient limbs mounted on the stock and extending laterally from the stock, the limbs being connectable at their free ends to a bowstring; and

(c) an adjustment member mounted on the stock and extending at least partly forward of the limbs to move at least one of the limbs to vary the distance between the free ends of the limbs whereby to vary the energy stored in the limbs.

20. A crossbow comprising:

(a) a stock; (b) a pair of opposed, resilient limbs mounted on the stock and extending laterally from the stock, the limbs being connectable at their free ends to a bowstring; and

(c) an adjustment member mounted on the stock and extending at least partly forward of the limbs to move the limbs substantially simultaneously to vary the distance between the free ends of the limbs whereby to vary the energy stored in the limbs.