US2586229A - Replaceable firing pin for mortars - Google Patents

Description

Feb. 19, 1952 c. N. HICKMAN REPLACEABLE FIRING PIN FOR MORTARS.

Filed Nov. 29, 1944 avwe/wtp'b CLARENCE N. HICKMAN 954 Fwd dyad Patented F eb. 19, 1952 REPLACEABLE FIRING PIN FOR MORTARS Clarence N. Hickman, Jackson Heights, N. Y., assignor to the United States of America as represented by the Secretary of War Application November 29, 1944, Serial No. 565,644

3 Claims. 1

The invention described herein may be manufactured and used by or for the Government, for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to ordnance and more particularly to rifled muzzle loading ordnance of the mortar classification.

More specifically this invention consists of a new and improved method for obtaining adjustments in the range of projectiles fired from mortars. It is well known that the angle of elevation of mortars can be varied only slightly to produce small changes in range. To acquire larger changes in range it has been customary to provide the projectile with the maximum propellent charge necessary to acquire the maximum range, and to remove portions of this charge, at or about the time of loading, as changes in range require. The prior art is replete with various methods and means for fastening these propellent charges to the projectile to facilitate easy removal of portions of the charge. When stabilizing fins are employed, the charge is preferably supported between the fins to permit easy removal of a portion of the charge to provide for range adjustments. Notwithstanding these improvements this method of range adjustment remains awkward and fails to provide the degree of precision desired.

By virtue of this invention precise adjustments in range may be easilly attained by changing the density of loading for any number of firings without the necessity of making adjustments on each projectile.

The mortar and projectile assembly of this invention consist mainly of a projectile containing a payload and a propellent charge which may be considered as including an ignition cartridge inserted into a container formed at the base of the projectile and the propellant proper which is formed of a plurality of thin plates of ballistite, or other suitable powder, which fits over the cartridge container. The projectile is muzzle-loaded into the barrel of the mortar and is fired when the ignition cartride engages a fixed firing pin in the breech end of the barrel.

As a result of my researches on the 4.2 chemical mortar which were conducted in an efifort to determine experimentally the optimum web thickness and density of loading for the mortar it occurred to me that adjustments of the initial volume of the combustion chamber to acquire adjustments of the density of loading might oifer a solution to the problem of range control for the mortar. By density of loading is meant the ratio between the weight of the propellent charge and the weight of the volume of water which would fill the chamber in which the charge is loaded. Actually a change in the amount of propellant results in a change in the density of loading; however, changes in propellant weight require that the propellant on" each projectile be modified and to avoid this I prefer to maintain a constant maximum charge and obtain changes in the densityof loading by producing changes in the volume of the powder chamber. of loading decreases the velocity of the projectile and the maximum pressure within the chamber but increases the length of travel of the projectile to the point of maximum pressure.

Various methods for acquiring changes in the volume of the combustion chamber logically include varying the length of the cartridgeholder or the spacing between the various bundles of propellant. However, any of these methods necessitate manipulations or adjustments on each projectile and would also involve mechanical difiiculties. I consider that these methods have little to offer over the prior art method of removing a portion of the powder charge. It occurred to me that I could acquire the necessary change in volume for the propellant by changing-the length of the firing pin within the barrel of the mortar. This method appeared so attractive initially that I immediately conducted tests to determine that sufiicient variations in range could be obtained by changing the length of the firing pin. I found that a change in range of about 200 yds. could be obtained for each one inch increase in length of firing pin.

Obviously it is impractical to dismantle the mortar to insert different length firing pins every time a change in range is desired, and tests indicate the change in length of firing pin required to produce the desired change in range is larger than can be accommodated for by adjustments on the mortar barrel. It occurred to me that by making the firing pin tubular in form so that it may be slidable over the fixed pin, adjustments in pin length could be easily acquired by inserting different length tubular members into the muzzle. I prefer to provide at each end of the tubular firing pin at least three radially divergent spider vanes for centering the tube withinthe barrel of the mortar.

In the appended drawings forming a part of this specification, there is disclosed a preferred embodiment of the invention, wherein,

In general, a decrease in density.

Fig. 1 is an elevational view partly in longitudinal section showing the replaceable firing pin in detail;

Fig. 2 is an elevational end view of Fig. 1; and

Fig. 3 is an elevational view in section showing the replaceable firing pin in assembled position within the mortar barrel.

Referring now to thedrawing and particularly to Fig. l there'is shown a tubular member 106i the replaceable firing pin fitted over the fixed firing pin 9 which projects from the breech end 8 of the mortar barrel 1, as illustrated in Fig. 3. The tubular member ID is shown provided with four fixed centering fins l2 and is threaded internally at its upper end so asto receive the front end M of the replaceable firing pin which has a generally pointed head ll3..adaptedxtolimpact against the percussion cartridge on a projectile. The front end 14 is also provided with four fixed fins IE to center the pin. This front end isadjustablein length by 'virtue of its threaded engagement with the lower portion of the pin. The openings H are provided for inserting a rod or other tool which may beneeded'to adjust the members in the event the threads become eroded by the products of combustion. These openings also permit equal pressure distribution on the inner" and outer surfaces of the-replaceable pin.

Fig. '3 shows the removable pin in place within the barrel of the mortar. To provide quick removal of these firing pins for substituting a pin of" different length, a hooked member may be inserted into the muzzle end of the'barrel for engagement with anyone of the projecting fins.

It should'be understood that I have disclosed only a preferred embodiment of my invention and that I do-not propose to be limited precisely to the structure illustrated or otherwise than within the scope of the appended claims.

I claim:

'1. A replaceable, adjustable firing pin for a mortar having a firing pin secured to its breech end, said replaceable firing pin including a tubular member and a second member having a pointed head and being adjustably and mo'vably secured to said tubular member and metallic radially extending means projecting from each of said members for centering said members within the mortar barrel.

'2. In combination, a mortar barrel having a fixed firing pin and a replaceable firing pin adapted to be slidably inserted in the muzzle of the barrel and-around said fixed firing pin; said replaceable firing pin including a tubular member and a front end, each of which are provided with a'pluralit'y'of radially extending flanges of equal length for centering said pin in said barrel;

saidtubular memberhaving an internal bore of greater diameter than the diameter of said fixed firing pin; said front end being pointed at one of its end portions and having its opposite end portion reduced in cross-section and of adiameter smaller than the diameter of said bore and adapted for insertion in'said tubular member.

3. The combination of claim 2 in which the tubular member and the front end of the replaceable firing pin are each threadably adapted for operative connection to each other.

CLARENCE N. HICKMAN.

REFERENCES CITED The following references are of record in the file of this patent:

FOREIGN PATENTS Number Country Date 521,747 France Mar. "14, 1921 348,052 Germany Jan. 30, 1922 299,088 Germany Aug. 17, 1922 585,216 France Dec. 4, 1924 352,916 Italy Sept. 25, 1937

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