Field howitzers

Details Field howitzers Field howitzers

1995-06-07

2001-01-30

Johnson, Stephen M. (Department: 3641)

Ordnance

Mounts

Counterbalances

C089S037070, C089S037130, C089S040040, C089S040090, C089S043010, C089S042020

Reexamination Certificate

active

06178866

ABSTRACT:

This invention relates to field howitzers and is concerned with the application, to field howitzers, of design techniques and philosophies not normally associated with the design of field artillery in order to produce such weapons having an absolute minimum of weight, yet still retaining all the other features required by such equipment, e.g range, reliability, accuracy, rate of fire, stability, robustness of construction etc.
The existence of rapid deployment forces is well known and it is desirable that the range of equipment available to these forces is as wide as reasonably possible. There is a need for the equipment available for these forces to include field artillery.
Newton's Third Law of Motion states that for every action, there is an equal and opposite reaction. Thus for field howitzers which can fire a heavy projectile over a great range, the recoil presents a particular problem. One means to minimise the recoil problem is to have heavy ordnance. However, a main purpose of the present invention is to minimise weight and it is an object of the invention to dissipate the recoil forces on light ordnance by the combination of:
i) optimised recoil buffer efficiency,
ii) optimised muzzle brake efficiency, and
iii) a new design concept that takes the resultant recoil forces directly to spades via a damped, energy-absorbing means.
For a conventional field howitzer, which is intended to be air liftable, air dropable and moved around a battle field with comparative ease, a relatively light (though still robust) chassis is required. To increase stability and spread the recoil forces, one method is to deploy a pair of trail legs with ‘spades’ at their further ends; the purpose of the spades is to dig into the ground and so absorb the recoil force. Despite their construction, such conventional field howitzers are far too heavy to be carried by the small or medium lift helicopters used near the actual battle zone.
NATO is in the process of standardising ordnance and ammunition systems into a single calibre. There is thus a need for an ultra lightweight version of the standard 155 mm field howitzer which can be transported as a single unit by a battlefield helicopter.
According to a first aspect of the present invention, there is provided a field howitzer which comprises:
i) a howitzer barrel,
ii) a cradle supporting the barrel and having a rearward end,
iii) a chassis, and
iv) a trunnion support structure secured to the chassis and including a trunnion bearing about which the rearward end of the cradle is pivotally mounted, said trunnion bearing lying on the axis of the barrel and being positioned beyond the limit of maximum recoil of the barrel.
The trunnion bearing should be placed as low as possible consistent with the other requirements of a field howitzer (e.g training, towing, loading etc.) and the location of the trunnion bearing beyond the point of maximum recoil so that the barrel does not recoil through the trunnion bearing enables this to be achieved and also ensures that the howitzer exhibits a high degree of out-of-balance.
In order to enable the field howitzer to be as light in weight as possible, the chassis should be a lightweight chassis and weight saving design principles should be used in the construction of the other components of the howitzer.
This aspect of the invention combines features of both a field howitzer and a mortar and the minimum trunnion height greatly facilitates the transfer of the recoil forces to the ground. The weight saving design principles employed include the use of lightweight strong alloys, integral construction, etc. The single lightweight chassis should rest on the ground, as opposed to the conventional chassis which rests on a sole plate which is in contact with the ground. This feature is a radical change from previous design practice.
The position of the trunnion support structure on the chassis is basically the same as for other field howitzers. However, relative to conventional designs, the barrel is moved forward so that the whole of it, including the whole of the supporting cradle, whether in the ready-to-fire position, or the maximum recoil position, is always forward of the trunnion bearing. This leads to a intermediate and high degree of out-of-balance which acts to oppose the recoil moment, particularly when the gun is fired at low angles of elevation e.g., from −2.5 °to 70°.
In a preferred embodiment, spades are secured directly to the chassis and the howitzer includes front stabilisers and rear trail support legs operable to spread the load over a large area of ground when not being fired, the latter also assisting to absorb recoil energy whilst resisting overturning and lateral forces.
Such spades, stabilisers and support legs may be incorporated in howitzers other than those of the type having a trunnion bearing lying on the barrel axis beyond the maximum recoil limit in accordance with the first aspect of the invention.
Accordingly, a second aspect of the present invention provides a field howitzer comprising:
i) a chassis,
ii) spades rigidly secured to the howitzer chassis;
iii) front stabilisers operable to spread the load of the howitzer over a large area of ground when not being fired; and
iv) rear trail support legs operable to spread the load of the howitzer over a large area of ground and to assist with the absorbing of recoil energy while providing overturning and lateral stability.
Preferably the spades are of the ‘self-digging’ type so that they will be fully effective as the first round is discharged. The attachment of the spades directly to the rear of the chassis in conjunction with a low trunnion bearing height provides an essentially rigid means of restraining the gun during recoil. Front stabilisers and trail legs generally improve stability and hence the aiming of the gun, but also play a part in the absorption of recoil energy. The term ‘trail legs’ is a generally accepted term in this type of howitzer. Although it is not intended that the howitzer of the invention be towed by ‘trail legs’, the term is retained for descriptive consistency.
The spades may be secured directly to the chassis or they may be secured to the ends of the rear trail support legs provided that they are relatively short and inflexible
Preferably the spades are removable when the howitzer is in the mode for being towed/transported.
In a preferred embodiment, the rear trail support legs are hingedly mounted on the chassis and hydraulic dampers are provided at, or near, the attachment points of the rear trail legs to the chassis to assist with the absorbing of recoil energy. These dampers for the rear trail legs can automatically compensate for uneven ground and give protection against excessive recoil forces.
In a further embodiment, the howitzer barrel is mounted on the chassis so as to be displaceable from a first to a second position with respect to the chassis, as a consequence of recoil on firing and the howitzer includes a recoil buffer system to absorb the energy of recoil as the barrel is displaced on firing, and also a recuperator system to return the displaced barrel from the second position to the first position, said recoil buffer system and said recuperator system being combined and utilising a single hydraulic accumulator arrangement.
Such a combined recoil buffer/recuperator system can be utilised with howitzers which are other than of the type defined in accordance with the first and second aspects of the invention.
Accordingly, a third aspect of the present invention provides a field howitzer comprising:
i) a chassis,
ii) a howitzer barrel mounted on the chassis so as to be displaceable from a first to a second position with respect to the chassis, as a consequence of recoil on firing,
iii) a recoil buffer system to absorb the energy of recoil as the barrel is displaced on firing, and
iv) a recuperator system to return the displaced barrel from the second position to the first position, said recoil buffer system and said recuperator system being combined and utilising a single hydraulic accumulator

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