Safety device for obsolete cylinder firearms

In a typical XIX Century revolver of the type comprising a hammer and a cylinder supported for rotation about a shaft having a predetermined axial position in said frame, a cylinder shaft rearwardly projecting out through said frame and towards said hammer, said shaft and said hammer having an extension and respectively a recess not symmetrical relatively to the revolver symmetry plane, whereby when said shaft is rotated in a first rotational position the said extension abuts on a not recessed part of the hammer, the said hammer is prevented from reaching the firing position, and when the shaft is rotated in another rotational position wherein said extension freely enters in said recess the revolver can be fired.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention is concerned with old type firearms, in particular with 
obsolete revolvers as devised and largedly manufactured in the second half 
of the XIX Century, such as "Frontier" and "Old Far West" revolvers, 
Colts, Smith & Wesson and so on, either restored or of new manufacture to 
accurately reproduce the original firearm, for actual firing of same. 
2. Prior Art of the Invention 
The interest and the historical value of such obsolete firearms is well 
known. Said revolvers form an important element of the history and legends 
of western countries. Such small arms are widely appreciated by collectors 
and also newly manufactured reproductions are in demand. Collectors and 
amateurs of said historical arms desire also to fire their arms and target 
competitions are being organized. 
The ingenuity of structure and of mechanisms of such more than one century 
old revolvers is admirable, but such arms must be considered as rather 
unsafe, according to current modern standards. 
A safety mechanism adapted for complementing the original safety system of 
such obsolete firearm has been described in my prior U.S. Pat. No. 
3,748,771, issued on July, 31, 1973. Such improved safety machanism is 
arranged for preventing the firing pin, seated into the hammer, from 
reaching the position wherein it can strike on the cartridge primer, when 
the revolver is set at its half-cocked position. 
There has been proposed also another safety device, described in the U.S. 
Pat. No. 3,803,741, issued on Apr. 16, 1974, comprising an axially and 
selectably movable cylinder shaft which, when positioned at a rearward 
hammer engaging axial position, presents the full forward motion of same 
hammer, as required for firing. 
The above referred known mechanisms operate upon the concept of making use 
of arrangements so as to prevent the firing pin or the complete hammer 
from reaching its primer striking position. This concept is sound. On the 
other part, this concept is generally applied by providing means for 
selectively securing a lengthwise movable element in a position on which 
it blocks the full forward motion of the firing pin or of the hammer. It 
is evident that if such movable element is subjected to follow the motion 
of the hammer (the inertia of which is relevant, in particular of a bulky 
hammer of an obsolete firearm) upon failing of the means provided for 
preventing the forward motion of some components, the wanted safety 
requirement will not be satisfied and the revolver will be unduly fired. 
It is therefore an object of this invention to provide a firearm, namely an 
old type revolver of the character referred to above, with an improved 
safety mechanism which does not affect the external appearance of the arm 
and its firing ability, and which is not subject to the above and other 
objections, but is capable of providing the most complete and efficient 
safety and protection against accidental or undue firing even under most 
violent shocks and unaccurate handling of the revolver. 
SUMMARY OF THE INVENTION 
Referring now to the invention, the cylinder revolver comprises a cylinder 
conventionally mounted for rotation about the central portion of a shaft 
which has fore and rear portions mounted into the frame of the firearm. 
The terms "fore" and "rear" define, in this specification and in the 
appended claims, the portion nearer to the barrel and respectively to the 
hammer. Also conventionally, the hammer is in part external to the rear 
portion of the frame and it is adjacent to said frame portion when the 
firing pin strikes the primer of the cartridge co-axial with the barrel. 
Still also conventionally, the various essential components of the firearm 
are arranged symmetrically to the firearm plane of symmetry wherein the 
axes of the barrel and of the cylinder lie. 
According to the invention, the rear portion of the cylinder shaft has an 
extension jutting out from the rear portion of the frame, said extension 
being asymmetrical i.e., off-axis relatively to the axis of the cylinder 
shaft, and extending in such amount that a not modified hammer will abut 
on said extension, when moving towards the firing position, well before 
reaching such firing position; at its turn, the hammer is modified by 
providing it with a recess facing the revolver frame and so positioned 
that, upon rotationally positioning the cylinder axis in one given 
rotational position, the said extension will freely penetrate in said 
recess so that the hammer can perform its entire firing stroke, except if 
said shaft is rotated in another position, different from said given 
position, so that the shaft extension will abut on a not recessed part of 
the hammer, preventing said hammer from completing its stroke. 
A critical feature of the invention consists in the fact that the cylinder 
shaft is arranged and rigidly secured in the revolver frame in one 
predetermined axial position, additionally in said given rotational 
position, whereby no risk of unduly accidental or unduly axial 
displacement of the cylinder shaft can occur (and consequent firing) even 
under the most violent shocks and most unaccurate handling of the 
revolver. 
These and other features and advantages of the invention will be now made 
apparent from the following detailed description of a preferred embodiment 
of same invention, reference being made to the accompanying drawing, 
wherein only the parts, components and arrangement of interest for the 
invention have been illustrated and evidenced. While the revolver has been 
fragmentarily and diagrammatically shown, it is well known. A complete 
diagram is not necessary to show the characteristics of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to the drawings, wherein like reference numerals refer to 
like parts throughout the several FIGURES; in FIGS. 3 to 6 numeral 36 
indicates a critical component of the invention, as positioned in the 
"FIRE" position of the firearm, and 36a indicates (in phantom lines) the 
same component, but positioned for setting the firearm at "SAFE". 
In the embodiment shown, the new device is associated with a typical 
revolver as constructed in the second half of the XIX Century (or with 
modern but exact replica thereof). The revolver includes a conventional 
cylinder 14 rotatably supported in a revolver frame 10, having a rear 
breech forming portion 30. A tapered opening is bored in said breech 
portion 30 for passage of the pointed fore part of the firing pin 28 which 
is associated with the hammer, generally indicated at 18 (and which will 
be described in detail below) for striking on the primer (not shown) of 
the cartridge which, in the cylinder 14, is actually aligned with the 
barrel 12 of the firearm. 
The revolver comprises further a trigger 24, pivotally supported in the 
revolver frame, and having a nearly pointed upper end portion 26, designed 
to engage any of various notches or steps provided ebout the lower and 
approximately rounded portion of the hammer 18. 
The operation of this mechanism is well known and will therefore not be 
described in detail. It is however to be noted that the actual firing of 
the revolver requires that the hammer 18, upon action on the trigger 26, 
will complete its full stroke under the force provided by the hammer 
spring 22, by rotating clockwise (in the position shown in FIG. 1) until 
the firing pin will strike the cartridge primer. The safety device is 
designed for positively preventing the hammer from completing its rotation 
about the axis of the hammer pin. 
The cylinder 14 is supported within the frame 10 by a shaft 16 having a 
fore and a rear portion seated into a bore provided in the frame fore 
portion and respectively frame rear portion. The shaft 16 is secured in 
one predetermined axial position by a pin latch 32 engaging a notch 32a 
(the notches 32a and 32b will be described below). A fore extension 34 of 
the shaft 16, forwardly jutting out from the frame 10, is conventionally 
provided for complete removal of the shaft 16, when the removal of 
cylinder 14 is desired. In the device of the invention, the same extension 
34 is made use of for manually rotating the shaft for setting the revolver 
at either of its "SAFE" or "FIRE" positions and conditions. 
The same shaft 16 has a rear extension 36 rearwardly jutting out from the 
rear portion, of breech 30 of the frame. As shown in FIGS. 3 and 4 this 
extension is not co-axial with the shaft but sharply off-axis thereto. The 
hammer body 18 (which, when the revolver is fired, is conventionally well 
adjacent to the breech 30) has a recess 38 formed thereinto in such 
position that the extension 36 can enter in such recess only if said shaft 
is being rotated in one given rotational position. 
In the specific structure shown in FIGS. 4 and 6, the recess 38 is 
asymmetrical relatively to the hammer (and entire firearm) plane of 
symmetry, containing the axes of the shaft 16 and of the barrel 12. 
This combination of off-axis extension 36 and of recess 38 leads to the 
fact that when the shaft is correctly positioned in its predetermined 
rotational "FIRE" position (FIGS. 3 and 4) relatively to the hammer, and 
the preliminarily cocked hammer is conventionally triggered, the revolver 
will fire because the extension 36 does not prevent the full stroke of the 
hammer (to the position of FIG. 1), the said extension freely seating into 
the recess. 
On the contrary, if the shaft is rotationally positioned in a different 
position, the extension 36 will abut on the hammer body and prevent such 
hammer from rotating clockwise more than the abutment position, such as 
the position shown in FIG. 5. Such rotational position sets the revolver 
at "SAFE". 
The safety is improved upon rotating the shaft 180.degree. from the 
described "FIRE" position, such as in the position indicated at 36a and 
shown in phantom lines in FIGS. 3 and 4, for abutment on a positively not 
recessed part of the hammer, and by providing means for allowing the shaft 
to be set only in either of said "SAFE" or "FIRE" positions. Such means 
can consists of the said latch pin 32 and said notches 32a and 32b . 
Both said notches are made by tangentially machining the shaft at opposite 
locations of its cylindrical surface. In other words, said notches form 
recesses which are geometrically secant, in the same transversal plane, of 
the cylinder defined by same shaft 16. Therefore, the engagement of the 
latch pin 32 in either of the notches 32a or 32b provides (i) the securing 
of the shaft in one single predetermined axial position relatively to the 
revolver frame and hammer and one respective given rotational position 
wherefrom the shaft cannot be rotated, except upon exertion of a wanted 
positive action on the latch pin, or other suitable latching device 
adapted for firmly securing the shaft 16 in the selected both axial and 
rotational positions, principally for preventing such shaft from being 
axially displaced under the most violent shock exerted by and/or on the 
hammer. 
The said notches 32a and 32b and the said extension 36 of the shaft are 
arranged, relatively to the recess 38 formed in the hammer, so that when 
the pin 32 is firmly engagement in the notch 32a, the extension 36 will 
face the recess 38, whereby the hammer will not be blocked in its full 
stroke and will reach its striking position of FIG. 1, for firing the 
revolver which, consequently is at its "FIRE" condition. When the shaft 
has been rotated by the gunman 180.degree. and the latch pin firmly 
engages into the notch 32b, the shaft 16 will be axially and rotatively so 
locked in such position that the extension occupies the position indicated 
at 36a facing a not recessed part of the hammer. The shaft and the hammer 
cannot therefore be moved towards a position further than that shown in 
FIG. 6. The revolver is consequently set at "SAFE", ensuring the most 
complete safety.