Drum cartridge - magazine

A cartridge magazine including a spiral channel having a tangential linear xit section, a plurality of spider arms dividing the cartridges into groups of cartridges and having a plurality of indentures in their radial faces, and a drive means mounted external to the magazine for driving said arms. The spiral is a perfect Archimedian spiral and the indentures on an arm number one less than the number of cartridges in a group and are displaced radially by the diameter of a cartridge.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a mechanically operated cartridge magazine 
for use with automatic weapons. 
The history of weapon feed mechanisms include hand loading, internally and 
externally powered devices and the various combinations of round 
configurations and assembly. However, in regard to the present invention, 
i.e., a stored energy cylindrical drum feed mechanism for portable 
weapons, the availability of the devices is limited and of these limited 
devices, performance has been erratic and unreliable. F. A. Hobart on 
pages 22 and 23 of "Pictorial History of Submachine Guns" (Charles 
Scribner's Sons, New York, 1973) catalogued some of these weapons. 
Maxim determined that a flat drum feed was impractical for sustained fire; 
Carr, with a high capacity drum, encountered power consumption 
difficulties; and the Lewis gun, with a flat rather than cylindrical 
disposition of the cartridge, was eminently successful as reported on 
pages 131, 226, and 280, respectively of "The Machine Gun", Vol. 1, 
McChin, George, Superintendent of Documents, U.S. Government Printing 
Office, Washington, D.C. 
U.S. patents which generally show the state of the art of drum magazines 
having approximately spiral internal configurations are as follows: 
U.S. Pat. No. 290,622 
U.S. Pat. No. 1,347,755 
U.S. Pat. No. 1,361,402 
U.S. Pat. No. 1,596,178 
U.S. Pat. No. 2,394,606 
U.S. Pat. No. 2,596,293 
The problems with the prior art are explicitly spelled out in these 
patents, namely, the unevenness of drive pressure using a single rear-most 
arm on the cartridges, which also results in binding of the cartridges 
against the exterior guide walls, and the inability of spring mechanisms 
to exert sufficient pressure to accelerate and feed the cartridges within 
the time allowable during the excess breach block travel and the 
subsequent opening of the feeding aperture. Solutions of these problems 
have included using circular and non-spiral guide configurations, a second 
loading spring to bias the cartridge to the breach, and larger non-spring 
type of driving mechanisms. These solutions have not proved practical for 
the high speed weapons presently used. 
Thus there exists the need for a drum cartridge magazine which resolves the 
problems of parasitic power consumption due to component loading 
manifested as friction between adjacent cartridges and between the 
cartridges and container, to provide reliable and high capacity, high 
speed cartridge feed. 
2. Summary of the Invention 
The present invention is a drum or cylindrical shaped cartridge magazine 
used with high speed weapons wherein a perfect spiral channel terminates 
in a tangentially linear exit section. A plurality of spider arms 
extending radially from a hub divide the cartridges into a plurality of 
groups of cartridges. An externally mounted torsion spring drives these 
spiders through the hub so as to bias and feed the cartridges from the 
spiral to the exit section. The spiral being a perfect Archimedian spiral 
defined by the equation r=K.theta.+a for the centerline of the channels on 
each opposing face of the housing. The walls of the channels differ or 
vary from the centerline by an amount defined by the radius of the nose 
and base of the cartridge respectively, such that the axis of the 
cartridge is parallel to the axis of the hub. The radial faces of the arms 
of the spider includes a plurality of indentures for engaging and driving 
the cartridges in the linear exit section. The radial distance of the 
indentures from the center of rotation increase radially by the diameter 
of the cartridge. The number of indentures in the radial face of an arm is 
one less than the number of cartridges in a group. Thus for four 
cartridges to a group, there are three indentures in the radial face of an 
arm. The lateral faces of the arms diverge radially so as to continuously 
engage the leading and trailing cartridge as the cartridge traverses the 
spiral channel by defining a constant circumferal distance between the 
lateral faces at all radial points. 
OBJECTS OF THE INVENTION 
An object of the present invention is to provide drum cartridge magazines 
capable of operating with high speed automatic weapons. 
Another object is to provide an Archimedian spiral cartridge magazine for 
use with high speed weapons. 
A further object of the invention is to reduce parasitic power consumption 
due to component loading. 
Still another object is to provide a drum cartridge magazine which 
maintains individual control over the cartridges and provides reliable 
high capacity drum feed. 
Still even a further object of the present invention is to provide a 
smooth, accurate, high speed feed of cartridge from the magazine using a 
single source of stored energy drive through delivery. 
Other objects, advantages, and novel features of the present invention will 
become apparent from the following detailed description of the invention 
when considered in conjunction with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
As illustrated in FIGS. 1 and 2, the drum or cylindrical magazine 10 
consists of opposed end plates 11 and 12 whose interior walls are spirally 
indented to form tracks or channels 13 and 14 which act to guide the nose 
and base of cartridge 15 respectively. A weathertight cover or side wall 
16 is attached between the end plates 11 and 12 by means of suitably 
located fasteners 17 or other similar devices. Each end plate contains a 
line bearing 18 and 19 located to accommodate shaft or hub 20 on which are 
positioned the base spider arms 21 and the nose spider arms 22. The 
spiders 21, 22 are driven by spring 23 which is a commercially available 
torsion spring so wound as to produce an effectively constant resisting 
force during extension. Spring 23 is externally mounted and biased tightly 
against post 24 of the end plate 11 or 12 and is secured to shaft 20 to 
rotate the assembly of shaft 20 and spiders 21 and 22. 
The cartridges 15 are shown positioned within the drum 10 with axis 
essentially parallel to the axis of shaft 20 and constrained by the 
spiders 21 and 22. A plurality of groups of four cartridges are defined by 
the separation between the individual arms of spiders 21 and 22. 
As driven by the spiders and guided by the channels, the cartridges are 
progressively moved into channels 26 and 27 which are formed as integral 
straight or linear tangential extensions of channels 13 and 14 and end 
plates 11 and 12. The extreme extension of channels 26 and 27 position the 
cartridges for stripping off from the magazine by the bolt carrier motion. 
An alternate construction would employ a cantilever mounting of the shaft 
20 and combine one side plate 12, for instance, with a deep cylindrical 
cover for purposes of convenience and economy. 
The theoretical centerline path 28 of the spiral tracks 13 and 14 in end 
plates 11, 12 is defined as a segment of an Archimedian spiral of 
mathematical definition: 
EQU r = K.theta.+a 
where, in polar coordinates: 
r = radius from origin to any point on the centerline 
.theta. = polar angle to this point 
K = proportioning coefficient 
a = initial offset from origin. 
FIG. 3 illustrates in expanded scale the relation between the cylindrical 
cartridge 15, the spiral path of the centerline 28, and the path of the 
outer wall 29 of the channel for the base of the cartridge. This spiral 
path 29 must also take the form 
EQU r.sub.1 = K.sub.1 .theta..sub.1 +a.sub.1 
where, in polar coordinates: 
r.sub.1 = radius from origin to any point on the outer wall 
.theta..sub.1 = polar angle to this point 
K.sub.1 = proportioning coefficient 
a.sub.1 = initial offset from origin. 
The path 28 and the path 29 are related by the requirement that the tangent 
to 29 always be perpendicular to the circle representing the cartridge 
periphery whose center is always on 28. This provides a numerical solution 
to the obtuse triangle formed by r, r.sub.1, and d/2 where d/2 is the 
radius of the cartridge circle, as shown in FIG. 3. At r, .theta., the 
tangent to 28 is determined from tan .PSI.=r(d/dr) where .PSI. is the 
angle between r and the tangent line. 
EQU .PSI. = arc tan [r(d.theta./dr)] 
By definition, the perpendicular to the tangent at the point of tangency 
will be the radius of the cartridge circle which will be also 
perpendicular to the tangent line of the cartridge circle at its 
periphery; i.e., at a point where the periphery of the cartridge circle 
contains curve 29. By one of several solutions: 
EQU cos .phi. = d/2k; 
EQU sin .phi. = j/k; 
and 
EQU k = (d/2 cos .phi.); 
where .phi., j and k are defined in FIG. 3. Since 
EQU .PSI. = a = arc tan [r(d .theta./dr)] 
EQU J = (d/2r) (dr/d.theta.) 
EQU k = d/2 [1 + (1/r)(dr/d.theta.).sup.2 ].sup.1/2. 
r.sub.1.sup.2 can be calculated from r.sub.1.sup.2 = (r+k).sup.2 + j.sup.2 
- 2(r+k)j cos .alpha. whereby, with r = 0.0696.theta. + 0.250 and d = 
0.375, r.sub.1 = 0.435 in. But, r.sub.1 = k.sub.1 .theta..sub.1 +a.sub.1 
defines the outer wall. So, from FIG. 3, at .theta. = 0 
EQU .theta..sub.1 = .theta.-.beta. = -6.71.degree. 
EQU a.sub.1 = r.sub.1 - K.sub.1 .theta..sub.1 = 0.435-(0.0696) (-0.117) = 0.433 
in. 
and r.sub.1 = 0.0696.theta..sub.1 = 0.443 in. 
Guidance of the nose section by the corresponding opposite wall track will 
be guaranteed by the same reasoning but will have a definition of the wall 
of that spiral as determined by the diameter of the nose at the contact 
point. 
A second geometric relationship which is important to the present invention 
is the lateral faces 30 and 31 of the arms of the spider 21 and 22 which 
engage the leading and trailing cartridge of the four cartridge group. Any 
curve face 30, which provides a continuous surface over the span from the 
inner to the outer channel such that the point of contact with the 
cartridge is maintained will satisfy the design requirement. An infinite 
number of curves will do this and, for manufacturing simplicity, a 
bilinear development along faces 30 and 31 is elected. The tangent to the 
cartridge case, in cartesian form, for .theta.=0 is y = 0.15 in., for 1.3 
in &lt;r&lt;1.6 in., and for the outer section is y = 0.557x-0.75 in. The 
reverse face 31 of the spider forms a compartment of constant width. The 
face 30 and 31 diverge radially to provide the constant circumferal width. 
The relationship of the design of spiral channels and the lateral faces of 
the spider arms are best illustrated by the resulting forces on the 
cartridges. FIG. 4 illustrates the initial forces as statically disposed 
on the cartridge which bears on the leading contact face 30 of the spider 
arm 21. From the previous geometric discussion, it is obvious that 
adjacent cylindrical cartridges 15 will contact at their radii locating a 
point interior to the centerline of motion 28 and producing resisting 
force F.sub.1 directed radially through the cartridge center of gravity. 
Application of F from face 30 of spiders exterior to the centerline path 
28 will thus produce a resultant force which will be disposed at the inner 
wall 32 as reaction F.sub.2. Since the three remaining cartridges in this 
group will contact at their periphery and the contact point will always be 
interior to path 28, these cartridges will bear against the outer wall 29 
in the first and third quadrants. In the second and fourth quadrants the 
disposition will be reversed. F.sub.3, F.sub.4, and F.sub.5 indicate 
corresponding forces on these cartridges. 
The friction forces will oppose the direction of local motion but, due to 
the small contact area and the small unitized loading from forward 
cartridges, they will be of negligible magnitude. The accelerating forces 
never exceed three "g" along path 28 and are also negligible for strength 
determinations. 
Each four-cartridge group is impelled as a unit along the channel to the 
straight exit channel 26, 27. As the single cartridge at the top is 
stripped from the string by the forward motion of the bolt (not shown), 
the shaft 20 and spider arms 21, 22, under the torque produced by the 
spring 23 can index forward the equivalent of one cartridge rotation. The 
contact faces 30 of the spider at its outer extremity describes a circle 
which ultimately sweeps past the channel span and ceases contact with the 
cartridges. Concurrently, the return motion of the bolt--which contains a 
"pick off" lug--acts on the top cartridge to press down on the string. The 
reversal of forces and of motion is contained by the progressive steps or 
indentures 33 machined into the radial face of the spider arms. As each 
step face exceeds the cartridge contact limiting location, the one 
following is then in position to contain the cartridge string. The 
following group of four cartridges is then automatically fed into the 
string from the spiral channel as the last step face rotates out of 
contact. 
The contact faces of the separate steps are uniformly spaced across the 
spider periphery and the radial extent of each step is also uniformly 
graduated at the rate of one cartridge diameter per step. The inner edge 
of the channel determines the inclination of the radial faces; i.e., the 
radial faces should align with the inner edge of the channel upon passage. 
The number of indentures are one less than the number of cartridges in a 
group. For the illustrated embodiment, three indentures 33 are needed for 
the four cartridge group. The operation of the indentures is shown in FIG. 
5 wherein a cartridge 15 engages the last indenture 33 of spider arm 21. 
The spider arm design and configuration constitutes the central element of 
this invention. A predetermined, uniformly stepped motion is required by 
the gun operating cycle and is delivered by the self-compensating spring 
drive in combination with the individual regulation of the cartridges by 
the stepped outer controur of the spiders at the transition section in the 
movement of the cartridges from the spiral channel to the straight feed or 
exit channel. 
The preceding description of preferred embodiments is evidence that the 
objects of the invention are obtained in that a drum cartridge magazine is 
provided having a uniquely designed channel and spider arm configuration 
to produce a rapid, continuous and smooth delivery of a plurality of 
cartridges to an automatic weapon. Although the invention has been 
described and illustrated in detail, it is to be clearly understood that 
the same is by way of illustration and example only. 
We wish it to be understood that we do not desire to be limited to the 
exact details of construction shown and described, for obvious 
modifications can be made by a person skilled in the art.