Flask lock

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The piston lock is a lock design that was used between about 1840 and 1880.

Basic requirements

The breech of the gun closes the barrel at the rear and must divert the forces of the recoil through the barrel into the carriage structure when a shot is fired. To do this, it has to lock reliably with the pipe. Together with the cartridge, it must seal the tube gas-tight in order to use the propellant charge as completely as possible. The breech should provide protection against accidental firing. In principle, it must be possible to open and close the lock quickly with just a few hand movements when manually operated. Low weight and small dimensions are still required in order to minimize the dead tube length, that is, the length of the tube behind the cartridge or powder chamber. This dead pipe length together with the return path of the pipe determines the maximum pipe elevation for a given carriage construction.

history

Wahrendorff's flask closure around 1840
Wahrendorff's flask closure around 1843

Muzzle loaders were the defining form of construction for artillery pieces until the middle of the 19th century. Around 1840, the Swedish manufacturer Baron Martin von Wahrendorff started an attempt to make breech-loading guns marketable. He intended to simplify the operation of the guns in the cramped spaces of the ships and casemates. In order to achieve this goal, he was then forced to develop a functional breech-loading lock. For this he chose a basic shape of the piston closure. In the first picture this closure is shown schematically. It consisted of the cast iron locking head, which filled the soul with very little room for maneuver. A clamping screw was attached to this so that the bolt head could be clamped against the flat transverse wedge using the crank. A curved steel disk (expansion disk) was attached to the breech block as a remedy, which was supposed to lie flat when the shot was fired by the action of the powder gases and thus to close the barrel gas-tight to the rear. In practical operation, however, this system has not proven itself, as the cross wedge in particular was dimensioned far too weak. In 1843, Wahrendorff presented an improved closure (Fig. 2). In this closure, the closure cylinder had a slightly larger diameter than the chamber. Only with its front part did it fit exactly into the chamber. The rear part of the locking cylinder was drilled through to the transverse hole and provided with a thread by means of which the locking cylinder could be braced against the transverse cylinder by means of a strong screw. The domed steel disc already described above was still used to alleviate this. This form of leaning was not enough, however, and so a short time later the curved steel disc was replaced by a steel ring with a triangular profile (new marked as leaning in Figure 2). In this form of ligation, the hypotenuse of the ligation ring was directed obliquely forward against the pressure of the powder gases, while one of the two cathets rested on the soul (chamber) wall and the second rested on the front surface of the locking head. In order to enlarge the enlargement, the ring was slotted.

Under the influence of the development of towed breech-loaders, Prussia also began to work intensively on the further development of the Wahrendorff piston lock between 1850 and 1860. The main effort here was to improve the suppression. In the last method described above according to Wahrendorff, powder gases could still penetrate the slot of the eyelid ring and lead to burns on the closure head or on the pipe wall. Since no improvements could be achieved by mechanical means, the Liderungsring was finally taken on itself and experiments were carried out with a wide variety of materials. A cup-shaped pressboard was ultimately found to be the best material. But even with this version, not all problems could be solved alone. It was important here that the disks had to be of constant quality and that they were just inserted into the pipe. To remedy this, the pipes in the cargo hold were drilled out slightly conically so that the panes could be manufactured with a slight oversize. The insertion of the discs has been simplified insofar as the discs in the 9 cm caliber are firmly connected to the cartridge bag and in the larger calibers the discs are provided with a central hole, which greatly simplifies the handling of the discs. The Prussian version of the butt lock was first introduced in series in the 9 cm field gun C / 61 in 1859. In the Austro-Hungarian army, the 12 cm M1861 cannon was also introduced, a breech loader with a piston lock. Because of its design-related disadvantages, the piston lock was quickly replaced by other types of locks such as the wedge lock and the screw lock .

Construction principle

Piston lock, Prussia, ca.1860
Replica of a Prussian C / 61 with the piston lock open

With a piston closure, a closure piston is inserted into the tube from behind. For locking, a transverse cylinder is pushed through corresponding bores transversely to the pipe axis through the base piece and the locking piston. Using the crank (m), which was secured on the clamping screw by two lock nuts around 1860, the locking piston was now pulled back a little and in doing so presses the locking piston onto the transverse cylinder as well as against the rear wall of the transverse cylinder bore. Through this measure, all parts of the closure were firmly connected to each other and to the pipe. Since there were no elements for leaning in this construction, corresponding additional parts had to be inserted before each shot. In the case of the Prussian guns, cup-shaped chipboard disks were inserted between the cartridge and the piston head, which widened when fired and created the gas-tight seal between the piston and the tube wall. At the end of the long development period, the lock nuts were replaced by a so-called split-pin wedge around 1865. Due to the many manual work steps, there was no automatic locking. Likewise, there was no automatic protection against unintentional firing if the bolt was not fully closed or the locking mechanism was missing. The large number of operating elements leads to complicated handling and thus long loading times. Basically, the breech was usable, but appeared unsuitable for guns with a caliber over 15 cm due to the masses to be moved.

While maintaining the basic principle - inserting the closure into the tube from behind - the screw closure was developed from the piston closure.

Individual evidence

  1. ↑ Joseph Schmoelzl: A textbook for the knowledge and study of the firearms of the modern age. 2nd Edition. Literary and artistic establishment of the IGGolla'schen Buchhandlung, Munich 1857, p. 223.
  2. ^ Military weekly paper for the German armed forces. 1st year 1860. Supplement to issue No. 20 from November 17, 1860. Eduard Zernin, Darmstadt & Leipzig. P. 79.
  3. ^ Military weekly paper 53rd year 1868. Issue 17 of February 26, 1868. Ernst Siegfried Mittler and Son, Berlin, p. 132.
  4. ^ Karl von Helldorf: Prussian field pocket book for officers of all weapons. 2nd Edition. Gustav Hempel, Berlin 1869. p. 43.

literature

Web links