TECHNICAL FIELD AND BACKGROUND ART.
The present invention relates to an automatic cocking device in a
crossbow for hunting and/or archery.
In known archery and hunting crossbows, one of the main problems is
that of their cocking because of the considerable force required to tension the
bowstring.
Crossbows are known in which cocking is facilitated by the presence
of a ring in the frontal area of the crossbows into which the shooter inserts a
foot, so that with the crossbow bearing on the ground and secured by his/her foot,
the shooter can pull the bowstring towards him/her with his/her hands until bringing
it in the position in which it catches the shooting device associated to the trigger.
However, such a solution is still not very practical and it requires
considerable effort on the shooter's part: in fact crossbows with tensioning exceeding
150-180 pounds (corresponding roughly to 68-82 kg) cannot be constructed.
Another manual cocking system, already used in medieval times, comprises
a crank to be operated by the shooter to tension the bowstring by means of reducing
mechanisms, but such a solution is operatively complex and the lesser effort required
is paid for with an excessively long cocking time.
Moreover, from US 2,520,713 a crossbow is known in which the trigger
assembly can translate along the longitudinal axis of the crossbow. In a first phase
the trigger assembly translates towards the flexing elements to catch the bowstring
and in a second phase the operator tensions the bowstring, returning the trigger
device to the rear position.
The cocking action therefore takes place manually, acting on the trigger
assembly instead of directly on the spring.
Thus, such a crossbow has the drawbacks of a manually cocked crossbow
especially as regards the efforts the operator must exert during the cocking phase.
The sole automatic system known to the Applicant is the one disclosed
in US 5,220,906 which relates to a device to draw the bowstring of a crossbow, operated
by a battery-powered electric motor and housed in a case associated in removable
fashion to the crossbow.
The device comprises a shaft which is at least partly threaded and
which translates relative to the case on a guide and support walls, actuated by
the electric motor.
The electric motor sets in rotation (clockwise or counter-clockwise
depending on the position of a switch) a drive shaft whereon is keyed a first gear
wheel which meshes onto a second gear wheel mounted on a sleeve having an inner
thread which couples with the outer thread of the threaded shaft that translates
relative to the sleeve in such a way as to transform the rotational motion of the
drive shaft into translating motion of the threaded shaft relative to the trigger
of the crossbow. End stop sensors are provided to check the run of the threaded
shaft.
However, this solution, which is the only one described in the patent,
provides for the rather bulky housing that contains the motor and the battery to
be located in the front area of the crossbow in front of the shooting area, in a
rather inconvenient position and which, in any case, requires the housing to be
removed prior to shooting, both because of the impossibility of releasing the arrow
and because the weight of the device on the tip of the crossbow would create an
imbalance which would prevent the shooter from shouldering it correctly and from
aiming properly.
The patent also mentions the possibility for the device to be positioned
in the rear area where the crossbow is shouldered, but it fails to explain in any
way how to position it, probably because the inventor did not know how to position
it to obtain an effective operation.
Indeed, if the device where actually to be located in the rear part
of the crossbow it would have to pull the bowstring (instead of pushing it) during
the cocking phase, but the element destined to interact with the bowstring (the
slots 74 of the patent) is wholly unsuitable for gripping the bowstring to pull
it, as it can only push it.
Moreover, with all traditional bulky elements of the rear part of
the crossbow, it is difficult to comprehend a possible installation position of
the device which, among other problems, would act in a manner that is not parallel
to the shooting axis (as is readily apparent also from Figure 4 of the aforesaid
document).
The lack of parallelism between the action of the automatic device
and the shooting axis of the crossbow is a further drawback of the crossbow described
in the aforesaid patent and it leads to the following consequences. If the device
is mounted anteriorly, it produces a high level of friction of the bowstring against
the frame of the crossbow and in particular against the plane whereon the arrow
slides during the thrusting phase of the bowstring towards the trigger, whilst if
the device is mounted posteriorly it cannot function because it would lift the bowstring
relative to the plane of shooting and hence the bowstring could not be properly
secured to the trigger.
Although the patent only describes the solution with the removable
cocking device (which penalises the shooter who has to mount and remove the device
every time he/she shoots), also mentions the possibility for the device to be permanently
fastened to the crossbow, but fails to explain how this would be possible and where
the device would be fastened. The reason for the many gaps in the patent should
be sought in the fact that the inventor probably had thought about some possible
variations but without finding any possible embodiment for them and hence without
putting a person versed in the art in the condition to construct and embody such
variations.
In particular, the aforesaid patent fails to teach how to fasten the
device in a permanent manner without influencing the balance of the crossbow and
consequently penalising the shooting phase.
In effect, the solution described and illustrated in the patent is
ineffective and not feasible for the many problems described above, and in fact
as far as the Applicant knows such a solution has never been applied commercially,
whilst the other solutions only partially mentioned but not illustrated or fully
described (which, a fortiori, have found no commercial application) do not
constitute, in the Applicant's opinion, prior art.
To the aforesaid drawback one should add the fact that the cocking
action is effected directly on the bowstring, thus needing an appropriate fork element
destined to interact therewith. This drawback could be overcome by applying to US
Patent 5,220,906 the teachings of US Patent 2,520,713, i.e. by having the electric
motor act directly on a movable trigger. Such a solution would retain the aforementioned
drawbacks, in particular because there would still be a lack of parallelism between
the action of the automatic device and the shooting axis of the bowstring, with
the aforementioned consequences.
A manually and operable system for cocking the bowstring of a crossbow
is disclosed by US 5,823,172, wherein a mechanically operated device for drawing
a bowstring with an uniform tension or either side of the crossbow stock is described.
However, such a device has the same drawbacks afore-mentioned about
the automatic system disclosed by US 5,220,906.
In particular the cocking device is not an electromechanical automatic
cocking device, acts on the bowstring through an inclined fork which can only push
and not pull the bowstring and so the device has to be placed on the front edge
of the crossbow and has to be removed before shooting.
DISCLOSURE OF THE INVENTION.
The aim of the present invention is to eliminate the aforesaid drawbacks
and to make available a device for automatically cocking a crossbow applicable to
the crossbow itself in a fixed manner, with no need to remove it every time one
shoots.
Another aim is to avoid frictions and jams during the crossbow cocking
phase.
A further aim is to achieve the above in a simple and reliable manner,
without increasing the length or generally the dimensions of the crossbow itself
and thus avoiding imbalances which would adversely effect the shooting phase.
Said aims are fully achieved by the device of the present invention
which is characterised by the content of the claims set out below and in particular
in that the trigger block can translate on rectilinear path parallel to the longitudinal
axis of the crossbow, in which in a first phase the trigger block advances towards
the flexing element until the means for catching and releasing the bowstring automatically
catch the bowstring, and in a second phase the trigger block moves back until reaching
a position of correct tensioning of the bowstring in which the operation of the
trigger causes the instantaneous release of the bowstring, and in that it comprises
electromechanical means so shaped as to produce on the trigger block a force substantially
parallel to the shooting axis of the crossbow to carry out said first and second
phase.
The electromechanical means for automatically tensioning the bowstring
comprise an electric motor anchored underneath the crossbow in the area between
the trigger block and the butt, and powered by a battery preferably housed at the
rear part of the crossbow frame or at a grip of the crossbow itself.
The electromechanical means preferably comprise a ball screw show
low-friction rotation causes the movement of a sleeve associated to the trigger
block by means of a draw wire sliding on pulleys.
The crossbow can also be provided with a flexing element divided into
two halves, each pivotally engaged to the crossbow with the ability to rotate relative
thereto in order to be easily made operative by tensioning the bowstring.
BEST MODE FOR CARRYING OUT THE INVENTION.
This and other features shall become more readily apparent in the
following description of a preferred embodiment illustrated, purely by way of non
limiting example, in the accompanying drawing tables, in which:
- Figure 1 shows a partially sectioned lateral view of the crossbow;
- Figure 2 shows a partially sectioned top view of the crossbow of Figure 1;
- Figure 3 shows a partially sectioned lateral view of the crossbow of Figure
1;
- Figure 4 shows a front view of the crossbow of Figure 1;
- Figure 5 shows a detail of the crossbow of Figure 3.
With reference to the figures, the number 1 globally refers to a hunting
crossbow (though it could also be an archery crossbow) which in some figures is
shown without its covering fairing, the better to highlight its internal components.
The crossbow 1 comprises a frame 2 which extends longitudinally and
ends frontally with a flexing element 3 for tensioning a bowstring 4, whilst in
the rear part it is provided with a butt 5 for the correct positioning of the crossbow
by the shooter.
The frame 2 further comprises two grips 6 and 38 which extends inferiorly
from the frame itself to allow the shooter to sustain and operate the crossbow 1.
As the figures show, the distance between the grip 6 and the butt
5 is smaller than, and in particular equal to about 0.5 - 0.8 times, the distance
between the grip 6 and the front end of the crossbow. This solution makes the crossbow
extremely compact and easy to handle.
Moreover the frame 2 comprises in the front part two longitudinal
and parallel guides 7, whereon slides a trigger block 8 provided with means for
catching and releasing the bowstring of a substantially known kind and hence not
described in detail herein.
In this way the trigger block 8 can originally translate on a rectilinear
path, parallel to the shooting axis of the crossbow, in which during a first phase
the trigger block advances towards the flexing element 3 until the means for catching
and releasing the bowstring automatically catch the bowstring 4, and in a second
phase the trigger block 8 moves back until reaching a position of correct tensioning
of the bowstring in which the operation of the trigger causes the bowstring to be
released instantaneously.
The guides 7 are obtained by means of mutually parallel tension rods
and are fastened anteriorly to a support 9, which also sustains the flexing elements,
and posteriorly to a plate 10 comprised in the frame 2 and in particular in the
portion that embodies the butt 5.
An electric motor 11 and a battery 12 are associated to the crossbow
and substantially incorporated therein. In particular the butt 5 intemally houses
the electric motor, whilst the battery 12 can advantageously be inserted in the
grip 6 of the crossbow. The battery 12 therefore is anchored in removable fashion
by means of a pushbutton 39.
The operation of the electric motor causes the rotation of a drive
shaft 13 whereon is keyed a first pulley 14 which through a transmission belt 15
sets in rotation a second pulley 16 keyed onto the end of a ball screw 17 housed
between the support 9 and the plate 10, parallel and superiorly relative to the
shooting axis or longitudinal axis of the crossbow. In particular the ball screw
is positioned centrally relative to the longitudinal axis of the crossbow, in such
a way as not to affect the stability of the crossbow, especially when shooting.
The ball screw 17 is a known device, essentially comprising a worm
screw whereon slides a cylindrical sleeve 18 internally provided with balls what
interact with the thread of the screw, allowing 95% efficiency in terms of friction.
As shown in the figure, the ball screw 17 is inserted in two bellows
19, respectively introduced between the support 9 and the sleeve 18 and between
the sleeve 18 and the plate 10, to protect moving parts.
The sleeve 18 is connected to the trigger block 8 in such a way that,
when the electric motor causes the rotation of the ball screw, the sleeve 18 translates
thereon causing a corresponding translation, of equal extent, of the trigger block
8.
The ball screw 17 also has two shock absorbing elements 20 to brake
the run of the sleeve and operate a spring clutch comprised in a spring assembly
26. Said shock absorbing elements can be embodied by helical springs or rubber elements.
The electric motor 11 with the ball screw 17 and the sleeve 18 constitute
electromechanical means for the automatic tensioning of the bowstring, originally
shaped in such a way as to produce, on the trigger block 8, a force that is substantially
parallel to the longitudinal or shooting axis of the crossbow.
For this purpose the electromechanical means further comprise a driving
element integral with the trigger block, obtained by means of two draw wires 21
actuated by the electric motor. The two draw wires 21 are positioned on the sides
of the ball screw 17 and each of them has both its ends integral with the trigger
block 8.
The draw wire 21 is integral, in its intermediate position, with the
sleeve 18 and slides on pulleys 22 mounted able to rotate on the frame 2 from opposite
sides along the run of the trigger block 8.
The presence of the draw wires 21, able to slide on the pulleys 22,
guarantees the action of a force substantially parallel to the longitudinal or shooting
axis of the crossbow, together with the action exerted by the ball screw 17, by
the sleeve 18, able to slide on the ball screw 17 and by the guides 7.
For the operation of the electric motor 11, an electronic speed control
unit, indicated with 23, is provided together with a control 24 to determine the
direction of rotation of the motor (and hence of translation of the trigger assembly).
The speed control unit 23 and the control 24 can be applied to the grip 6, as shown
in Figure 1.
The electric motor 11 is also provided with an epicyclical reduction
gear 25 and with the clutch assembly 26 interposed between the electric motor and
the first pulley 14.
The trigger block 8 is of a substantially known type (apart from the
ability to translate) and comprises an actual trigger 27 pivotally engaged on the
trigger assembly 8 by means of a bearing and operatively associated to a catch 28
to hold the bowstring 4. Associated to the trigger assembly 8 is further provided
a safety device 29, comprising a breech bolt 30 and a safety lever 31.
As shown in the figure, the flexing element can be subdivided in two
halves 3a each of which is pivotally engaged in 32 to the crossbow. Each half is
so shaped as to be able to rotate relative to the frame 2 to shift from a rest position,
in which the two halves are substantially parallel to the frame, to a working position,
in which the two halves extend transversely relative to the frame to tension the
bowstring, and vice versa.
In particular, means 33 for locking and tensioning the bowstring are
provided with the purpose of tensioning the bowstring 4. Said means comprise two
pivot pins 34 having a first end integral with the frame of the bowstring and able
to be inserted into a slot 35 obtained in each of the two halves in proximity to
the end pivotally engaged to the frame. The locking action is effected by means
of threaded elements 36 able to be operatively associated to the pivot pins, by
the interposition of an element 37, at least partially cylindrical, to facilitate
the placement of the halves in the working position.
According to an embodiment variation not shown herein, the flexing
element can be single and fastened to the crossbow. In this case, a provisional
exterior string is used, tensioning which the flexing element is bent until the
actual string can be inserted, according to a known technology.
As regards the positioning of the device, when the bowstring is to
be tensioned acting on the flexing element 3, it is necessary to insert the pivot
pins 34 in the respective slots 35 and to screw the threaded elements 36 by approaching
the two parts of the flexing element to the support 9. The presence of the element
37 reduces friction and facilitates the locking of the flexing element.
When it is necessary to cock the crossbow again after releasing an
arrow, it is sufficient to act on the pushbutton for the operation of the electric
motor to cause the trigger block to advance towards the bowstring.
Before the trigger block reaches the aforesaid end stop, the bowstring
is automatically engaged in its catching device comprises in the trigger block,
automatically engaging the safety device that prevents accidental releases of the
arrow.
By inverting the direction of motion of the motor, it is possible
to command the adjustable tensioning of the bowstring, by returning the trigger
block in position. The sleeve 18 drives the draw wire 21 which slides along the
pulleys 22 and generates the translation of the trigger block 8 until the tun of
the sleeve is limited by the shock absorbing elements 20 and arrested by the clutch
26. The presence of the two draw wires positioned symmetrically relative to the
axis of the crossbow guarantees a balanced, frictionless interaction between the
trigger block 8 and the respective guides 7 and exerts on the trigger block a force
parallel to the shooting axis of the crossbow.
The main advantages of the present device consist of the capability
to shoot several times with no effort on the operator's part and of the capability
to load far greater powers than in current systems, in the capability to uncock
the weapon without necessarily shooting the arrow (it is sufficient to operate the
electric motor as in the initial phase to move the trigger block closer to the flexing
element, thereby reducing the tension on the bowstring), in the availability of
a cocking device incorporated in the crossbow itself and in such a position that
it does not hamper or hinder the operator in shooting operations.
In particular, unlike US 5,220,906, no element is positioned in front
of the flexing elements, and this allows to obtain a perfect balancing of the crossbow.
A further feature and advantage of the present automatic cocking device
is given by the fact that it operates with a force that is parallel to that of the
arrow and therefore entails no jams or frictions during the cocking phase or modifications
on the trajectory of the arrow during the launching phase.
The present device further allows to grab the bowstring always in
the same place and centrally, avoiding asymmetries.
