U.S. patent number 3,867,778 [Application Number 05/356,436] was granted by the patent office on 1975-02-25 for automatic choke for hunting rifles.
Invention is credited to Romolo Marchi, Giuliano Preda.
United States Patent |
3,867,778 |
Preda , et al. |
February 25, 1975 |
AUTOMATIC CHOKE FOR HUNTING RIFLES
Abstract
An automatic choke for buckshot rifles, comprises a tubular
element that can be screwed to the extremity of the rifle barrel,
said element being equipped with longitudinal slots spaced
equidistant from one another, its median part having a longitudinal
truncated cone cross-section, thus permitting, as a result of a
back-sliding of an external sleeve, caused by the thrust of a coil
spring, a reduction of the diameter of said tubular element; the
degree of back-sliding of the external sleeve being determined by a
system of notches accommodated in the terminal part of the external
sleeve, operated by a release tooth fastened to the tubular
internal element, said release taking place on account of the
recoil of the barrel at each discharge. It is also possible to use
instead of the recoil forces the counter forces generated at the
moment when the movable barrel reaches the end of its stroke.
Inventors: |
Preda; Giuliano (Bologna,
IT), Marchi; Romolo (Bologna, IT) |
Family
ID: |
26325381 |
Appl.
No.: |
05/356,436 |
Filed: |
May 2, 1973 |
Foreign Application Priority Data
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May 4, 1972 [IT] |
|
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3413/72 |
Dec 7, 1972 [IT] |
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3609/72 |
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Current U.S.
Class: |
42/79 |
Current CPC
Class: |
F41A
21/40 (20130101) |
Current International
Class: |
F41A
21/00 (20060101); F41A 21/40 (20060101); F41c
021/00 () |
Field of
Search: |
;42/79 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Feinberg; Samuel
Assistant Examiner: Jordan; C. T.
Attorney, Agent or Firm: Richards & Geier
Claims
What is claimed is:
1. A progressive automatic choke for a buckshot rifle having a
rifle barrel, said choke comprising a tubular element screwed to
the extremity of the rifle barrel and having longitudinal slots
spaced at equal distances from one another and also having a median
part with a longitudinal truncated cross section, a release tooth
carried by said tubular element, a slidable external sleeve having
a plurality of notches in its terminal part, said release tooth
engaging said notches to determine the extent of back sliding of
said sleeve, and a coil spring engaging said sleeve and causing the
back sliding of said sleeve, said back sliding causing a reduction
of the diameter of said tubular element, said release tooth
operating by the recoil of the barrel at each discharge.
2. An automatic choke according to claim 1, comprising a tubular
element which can be screwed to the barrel, whose inside diameter
is identical to that of the barrel itself and whose longitudinal
part has a truncated cone configuration in its median portion, a
plurality of slots extending longitudinally in the median portion
of the same element which render said portion elastic by leaving
undeformable and therefore cylindrical, the extreme part of said
tubular element.
3. An automatic choke according to claim 2 wherein the tube screwed
to the barrel of the gun has an external thread in its lower zone
with a long pitch and with a wide and flat turn.
4. An automatic choke according to claim 3 wherein the tube screwed
to the rifle barrel comprises a projecting blocking tooth fastened
on said thread turn.
5. An automatic choke according to claim 4, wherein the tube
screwed to the barrel of the rifle has a thread in its
median-to-lower external portion and a spring-clamp ring
screw-mounted upon the last-mentioned thread.
6. An automatic choke according to claim 4 wherein the tube screwed
into the barrel of the rifle comprises a spring-clamp ring screwed
into its median to lower portion and which has in a neck that runs
to the median upper part of the tube a plurality of receptacles,
corresponding to a plurality of seats for one extremity of the coil
spring.
7. An automatic choke according to claim 6, comprising a coil
spring to be wound around the tube, which, fastened with one of its
extremities in a seat of the spring clamp ring screwed to the tube,
and therefore to the fixed part of the device, penetrates with its
other extremity and releases its force into the terminal part of
the movable part of the sleeve, thereby imparting an axial thrust
and a torque which permits a semi-screwing down of the sleeve on
the tube, and therefore its recoiling, with a resultant narrowing
of the tube on its elastic part through a growing pressure onto its
external truncated cone surface.
8. An automatic choke according to claim 7, comprising a bushing
which, screw-mounted to the sleeve, becomes integral with same,
said bushing having an axially located hole on its upper
circumference suitable to house one extremity of said spring; one
oblique slot provided with saw-tooth notches suitable for gradually
effectuating the movement of the entire mobile part whenever the
release tooth fixed to the tube on account of the recoil of the
firearm proceeds from notch to notch, while the bushing is
half-screwing itself in during its backward motion.
9. An automatic choke according to claim 8, comprising a bushing
provided with a wide and flat internal thread that screw-mounts the
bushing itself to the terminal part of the tube, leaving a certain
clearance between the screw and the female screw of the thread.
10. An automatic choke according to claim 9 comprising a bushing
forming a receptacle having on the inside the same pitch as the
last-mentioned thread, which, starting out from zero, proceeds
until it is aligned with the first notch, and is suitable for
permitting the insertion of the release tooth in the coupling of
the bushing to the tube.
11. An automatic choke according to claim 8 comprising an external
sleeve which carries internally at its base a thread suitable for
screwing it to said bushing, said sleeve having a portion of its
internal part which conforms to the truncated-cone part of the
tube, producing with every back-sliding a relative narrowing of the
elastic tube.
12. An automatic choke according to claim 4, wherein its operation
is determined by the recoiling force of the rifle to which there is
applied a force that permits the disengagement of said tooth from
each notch, and as a result of the half-screwing of the sleeve
accommodating the saw tooth notches, and therefore of the entire
external part, said tooth enters the successive notch with every
discharge, thus selecting every choking ratio in view of the fact
that, to each individual notch, there corresponds a given pressure
of the mobile sleeve on the elastic portion of the tube.
13. An automatic choke according to claim 1, wherein the
progressive choke is caused by counter-forces generated when the
slidable sleeve reaches the end of its stroke.
14. An automatic choke according to claim 13, wherein the release
system is appropriately reversed in its rest position and the
notch-tooth contact occurs in the lower part of said notch, the
release taking place by a sliding upward motion of the tooth with
respect to the notch.
15. An automatic choke according to claim 14, comprising two
springs with separate torsion and compression functions.
16. An automatic choke according to claim 15, wherein the
compression spring rests upon a washer.
17. An automatic choke according to claim 16, wherein a central
collar separates the two springs.
Description
This invention relates to special types of automatic converters of
the nozzel of the barrel of automatic hunting rifles making use of
buckshot amnunition.
In the art there has already been recognized the importance of a
similar device which, applied to the barrel muzzle of the automatic
rifle, would eliminate its traditional drawback, i.e., the fact
that only one barrel, and therefore a single choke action, is
available for a considerable firing power in rapid succession
(four, five, or more rounds).
The present invention provides a new and exclusive design system of
a nozzle at every discharge which, by taking advantage of the
energy provided by the recoil, causes a progressive choking
action.
Such a system, of easy realization on account of its extreme
simplicity, consists of three main parts:
A fixed internal part, applied by screwing it to the appropriately
threaded barrel of the rifle;
A MOVABLE EXTERNAL PART AXIALLY SLIDING AS A SLEEVE OVER SAID
INTERNAL PART; AND
A MEDIAN PART, I.E., A SPRING CAUSING THE MOVEMENT OF THE MOVABLE
EXTERNAL PART.
However, the present invention also includes a different
construction wherein instead of the recoil forces the counter
forces are used which are generated at the moment when the movable
barrel reaches the end of its stroke. In this version, upon
recoiling of the barrel due to the explosion recoil, the entire
choking device slides back at the same time. Thus, the pivot
inserted into the notches in the rest phase finds itself compressed
by the spring in the position opposite to that of the notch with
respect to the one it occupies in the device provided for
fixed-barrel rifles, and it will be able to leave this position
only by moving upward, which is impossible during the recoiling
phase of the barrel. Therefore, the release phase of the spring
will not take place with the help of the recoil forces but with
counter-forces, i.e., the moment the mobile barrel returns to its
normal position. The latter forces applied to the tube carrying the
release element will be greater than those applied to the external
sleeve in any event on account of the different mass of the two
bodies provided with the same acceleration and therefore, by the
forward movement of the sleeve, the pivot, integral with the tube,
will leave its own seat, thus allowing the previously loaded spring
system to slide back the sleeve by choking the tube constituting
the terminal element of the rifle barrel.
Consequently this construction of the present invention includes
one spring mounted between the ring and the base of the sleeve (the
external bushing with notches) exclusively torsion-loaded, a washer
onto which there rests a second spring that is exclusively
compression-loaded, and the upper sleeve that will be screw-mounted
at its lower base provided with notches serving as a guide to the
release tooth integral with the tube on which there is furthermore
provided a wide-pitch thread that assists the tooth to withstand
the recoil shock.
The invention will appear more clearly from the following detailed
description when taken in connection with the accompanying drawings
showing by way of example only, preferred embodiments of the
inventive idea.
In the drawings:
FIG. 1 is a section through a device of the present invention.
FIG. 2 is a side view.
FIG. 3 shows the spring-clamp ring.
FIG. 4 shows the spring.
FIG. 5 shows the tube with the clamp ring applied.
FIG. 6 shows the outer bushing with notches (or terminal portion of
the sleeve).
FIG. 7 shows the tube with spring-clamp ring, spring, and bushing
applied.
FIG. 8 shows the complete sleeve device screwed to the bushing.
FIG. 9 is a perspective view of the separate parts of the device
constituting another embodiment of the present invention.
FIG. 10 is a perspective view of the bushing of the device of FIG.
9.
The embodiment of the present invention shown in FIGS. 1 to 8
includes an inside element consisting of a tube having an inside
diameter identical to that of the barrel 1 to which it is to be
applied by screwing it externally so as to form a natural
prolongation of the barrel itself.
This tube is deformable since it is rendered elastic by means of a
suitable series of longitudinal slots 2 cut in its medial part.
This system for varying the diameter of this terminal part of the
barrel makes it possible to achieve the so-called classic "choke
effect," which requires, behind the narrowing of the section, a
subsequent cylindrical portion; this being a universally preferred
effect adopted in the standard nozzle of the barrel on account of
the ballistic advantages inherent with regard to the so-called
"conical type" where the cylindrical part is missing.
The variation of the inside diameter of the tube according to the
present invention is obtained by the moving of the mobile part 3
toward its base, in other words, the external sleeve 3 moves as a
result of the thrust of spring 4. It exactly matches with its
internal surface the external surface of the tube which will have a
truncated cone shape in its median part 5. At every recoiling, the
friction between the two surfaces will force the elastic surface to
shrink, thereby causing a reduction in its inside diameter.
Internal parts of this device include the following elements:
An internal threading in the part joined to the muzzle of the
barrel;
an external threading along its lower portion, consisting of a wide
thread having a long pitch 6. (In practice, the desired result can
be obtained with a thread of a width of about 3 mm and a pitch of
14);
a small cylindrical stop tooth 7 fixed at a suitable point of the
thread;
a thread at its lower median portion 8 onto which it is to be
screwed; and
a spring clamp ring 9.
The middle portion of the device consists, as stated above, of a
coil spring 4 designed to slide into the tube and whose upper
extremity is to be fastened into the suitable seat of the spring
clamp ring 10, integral with the tube and therefore with the fixed
part of the device, while its lower portion is to be fixed to the
terminal zone of the sliding, external bushing 11 and therefore
into the mobile portion of the device. Once the spring has been
loaded, it will tend to stretch, finding its bearing point in the
fixed part of the device, and will therefore move the sleeve which,
as stated above, will determine the desired narrowing of the
tube.
For manufacturing considerations and easy handling, a mobile
external portion of the device consists of two elements which,
screwed into one another, become, as an assembled part, a single
whole. The first one of these two parts is the sleeve itself,
namely, the part which, slid over the tube, will conform with its
inner surface to the respective truncated cone shaped external
surface of the tube and, by back-sliding, will determine its
constriction 12.
The second part or bushing 13, displacing itself along with the
sleeve itself, serves to smoothen the recoil of the entire part at
every discharge.
The spring is the element that will generate the force of such a
recoil by imparting at the same time a pressure in axial direction
and a torque that will develop itself through the long-pitch
external thread 6 of the tube.
To that end, the busing is designed in such a way that its internal
surface forms the female thread 14 of the large terminal thread of
the tube and will be screwed to the tube. Between the pitches of
the thread of the screw and the female screw there is to be left a
certain clearance in order to permit the disengagement of the tooth
from its various and successive seats (notches).
In the bushing there is provided a narrow oblique slot 15 slanted
to conform to the pitch of the internal thread of the bushing and
which is to be milled between one pitch and the other one of the
thread and to be provided with a set of saw-tooth notches in which,
benefiting from the torque imparted by the spring to the sleeve,
the release tooth 7 will engage at every discharge. In order to be
able to screw the bushing to the tube and cause the release tooth
to enter the dead end notched sloth, said tooth being already fixed
in the tube, a suitable guide is provided inside the bushing,
making it possible to cause the tooth (of suitable dimension) to
pass therein as in a receptacle 16.
The device is operated as follows:
Having manually inserted the release tooth, e.g., into the first
notch, at the moment of firing, due to the recoil of the barrel,
the tooth will leave the notch without however coming in contact
with the blocking notch because it would break, due to the force of
the recoiling action. This is made possible through the provision
of the internal thread 14 of the bushing, which, in cooperation
with the external thread of the tube 6, forms a powerful
buttressing and stop ledge of the movement. At the same time, due
to the existence of a certain clearance between the screw and the
female screw, the tooth is allowed to leave the notch 17 and to
enter the subsequent one without slamming against the blocking
notch 18, in view of the presence of the aforementioned
thread-edge, and will slide on the slanted surface of the blocking
notch before entering the following notch 19. Since the latter is
higher than the former (it ought to be emphasized that the slot
with the notches follows the same pitch of the thread of the
bushing, and, therefore, is oblique), the result is that the entire
sleeve will recoil toward the base of the device to such an extent
as to allow an initial narrowing of the tube. And the action
proceeds in this manner until reaching the last notch, which will
correspond to the maximum recoiling point of the sleeve, and
therefore to the maximum narrowing of the elastic part of the tube,
hence to the maximum choking ratio, i.e., 10/10.
It is apparent that numerous changes may be made in the described
embodiment within the scope of the appended claims.
For example:
The tube can be designed without the cylindrical and rigid terminal
portion and can have instead open-ended longitudinal segments
basically producing likewise a kind of "conical type" choke.
The saw-tooth notches of the bushing can have a different alignment
and can be spaced from one another so as to avoid the gradual loss
of force of the spring in its torque.
The entire system can be reversed, thereby obtaining a narrowing of
the tube by means of an inverse motion of the external sleeve, in
other words, a wider distance, rather than proximity, of the latter
from the base of the device. It is obvious that, in that case, the
slant of the toothed slot will be reversed and the truncated cone
accommodated in the tube will likewise be reversed, just as the
spring will have to extend in opposite direction.
It is also possible to vary solely the slant of the notched slot in
opposite direction, with the result that, as the device is
actuated, by increasing the choke ration, the spring, instead of
extending, will gradually compress itslef, acting in this manner as
a simple shock-absorber of the recoil of the firearm.
In the embodiment of the present invention shown in FIGS. 9 and 10
the numeral 1' represents the rifle barrel, 2' is the external
thread milled onto samed, 3' is the tube, 4' is the wide-pitch
thread, 5' is the release tooth, 6' is the truncated cone profile
of the choke, 7' are the slots arranged to improve the elasticity
of the tube, 8' is the lower part of the sleeve, 9' are the sliding
notches of the tooth 5', 10' is the torsion spring, 11' is the
spring-clamp ring, 12' is a washer, 13' is a compression spring,
14' is the upper part of the sleeve.
FIG. 10 shows the outline of the notches and the distance to be
covered by the release tooth to release the spring and to permit
the sliding back of the sleeve over the tube with a resultant
choking of the latter. Numeral 15' represents the rest position of
the tooth 5' corresponding to the still undeformed barrel. It is to
be noted that said position, wherein the tooth touches the lower
portion of the notch is, in the same contact condition where it was
situated in the upper portion. 16' is the position of the tooth in
its first choking phase followed by a resultant recoiling of the
sleeve. 17' is the position of the tooth in the second choking
phase with a subsequent recoiling of the sleeve with respect to the
tube, and 18' is the position of the tooth in the maximum choking
phase with the sleeve being at the same level of the tube, the said
situation referring of course to a three-step choking
operation.
It is apparent that numerous changes can be also made in this
construction within the scope of the appended claims.
* * * * *