Cartridge shaped barrel insert

A cartridge shaped barrel insert is described that can be used as the barrel of a pistol and as a rimfire cartridge insert for a large bore weapon. The cartridge insert includes an internal secondary firing pin that can be actuated to fire a rimfire cartridge by a hammer on the pistol frame or by the usual hammer and center fire mechanism of a large bore weapon. A resilient pad within the insert yieldably urges the secondary firing pin away from the breech end of the barrel. A cap can be placed over the bullet of the rimfire cartridge to match the bore of a large bore center-fire weapon. When the cartridge is fired, the rimfire bullet and cap will be driven by expanding gases along the weapon barrel, with the barrel bore guiding the cap and bullet in the same manner as a conventional large bore bullet.

TECHNICAL FIELD 
The present invention relates to "subcaliber" cartridge firing inserts for 
large bore, center-fire weapons. 
BACKGROUND OF THE INVENTION 
A need exists, with increased interest in backpacking, fishing and hunting, 
for a compact, versatile, safe and reasonably priced pistol for rimfire 
cartridges. There is also a need for an effective adaptor or insert for 
large bore center fire weapons that will allow rimfire cartridges to be 
fired from the larger bore weapons. An ideal solution to these related 
problems is found in the present invention. 
A pistol and a small bore insert for large bore weapons may both be 
provided through the present invention. 
The pistol configuration is adapted to use the small bore insert as a 
barrel. The insert can be selectively removed from the pistol body and 
loaded into the firing chamber of a larger bore weapon, thereby enabling 
the large bore weapon to fire a small bore cartridge. 
Inserts or adaptors have been developed that allow firing of small bore, 
"rimfire" cartridges from larger bore "center-fire" weapons. They are 
generally made of soft metal (such as aluminum) since the expansive forces 
of cartridges fired within the insert are accommodated by the firing 
chamber of the larger bore weapon. Without the strength of the heavy, 
large bore firing chamber, the small bore inserts would at best have a 
rather short life and conceivably could explode. 
Prior forms of inserts are also unsafe to carry in a "loaded" condition 
with the small bore cartridge in place. Prior inserts typically include 
their own firing pin that may be struck by a center fire firing pin and, 
in turn, strikes the "rim" of the small bore cartridge. The insert firing 
pin is typically mounted with its rimfire end in direct abutment with the 
small bore cartridge rim. It takes much less striking force to fire a 
rimfire cartridge than it does a larger bore center-fire cartridge. 
Therefore, there is always potential danger that a loaded insert could 
fire if dropped or otherwise handled carelessly. Other inserts that allow 
for axial travel of the insert firing pin are just as dangerous because 
there is no provision to yieldably hold the firing pin back away from the 
small bore cartridge rim. 
U.S. Pat. No. 3,050,894 illustrates in FIGS. 13 through 16, a barrel insert 
that allows a center fire weapon to fire a rimfire cartridge. The insert 
includes a firing pin mechanism that slides freely in the cartridge to 
engage the rim of a rimfire cartridge. Another U.S. Pat. No. 3,598,053 
shows a similar arrangement, only with the rimfire end of the firing pin 
having two pin branches, both for striking a rimfire cartridge.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
The present invention is embodied in a cartridge shaped barrel insert 11 
for a firearm such as the pistol shown at 10. The pistol body receives the 
insert 11 for the purpose of firing a standard rimfire cartridge 12. The 
insert can be used with the piston 10, or it can also be used in a 
center-fire weapon 76 (FIG. 8), replacing the usual center fire cartridge. 
The present pistol 10 may be provided in two basic configurations. It may 
be provided with the cartridge shaped barrel insert 11 as shown in FIG. 1, 
or without the insert as shown in FIG. 4 wherein the basic pistol body is 
illustrated. 
The pistol body is comprised of a general rigid frame 14, having a handgrip 
or handle 15. The frame 14 also defines a hammer and trigger housing 16. A 
hammer mechanism 17 is mounted to the frame and spring loaded within the 
housing 16. A trigger mechanism 18 is also provided within the housing and 
is mechanically interconnected with the hammer mechanism 17 by an 
appropriate form of well known trigger and hammer release mechanism (not 
shown). 
The hammer mechanism 17 is used to strike a primary firing pin 19. The 
firing pin 19 is slidably mounted within the frame 14, having a striking 
surface 21 at one end and a projection 20 at the opposite end. The 
projection 20 is shaped similarly to a standard center fire firing pin. 
The firing pin and projection are centered on a bore axis of the insert 11 
within a breech recess 23 in the frame 14. 
Forward of the primary firing pin 19 and recess 23 is a long depression 22 
(FIG. 4) along the frame that is adapted to receive the cartridge shaped 
barrel insert 11. The firing pin 19 and breach recess 23 are at one end of 
the depression 22. The opposite end of the depression 22 is defined by a 
muzzle nose piece 24. The muzzle nose piece 24 is mounted to the frame 14 
for selective axial movement thereon. It includes a muzzle end recess 25 
to releasably receive a forward end of the barrel insert 11. The recesses 
23 and 25 are axially aligned when the insert is in place as shown in FIG. 
5. 
A biasing means 28 is illustrated in FIG. 4 for continuously urging the 
nose piece 24 inwardly, toward the primary firing pin 19. The biasing 
means 28 operates along a rod 29 that is affixed to the nose piece 24 and 
slidably journalled in the frame 14. The rod 29 is held by the frame 14 
along an axis that is parallel to the bore axis of the insert. A shoulder 
30 at a remote end of the rod mounts one end of a compression spring 31. 
The opposite end of the compression spring rests against an integral 
shoulder 32 formed within the frame. The spring 31 therefore resists axial 
motion of the nose piece toward the dotted line position as shown in FIG. 
4. The spring and rod both allow for turning motion of the nose piece 
about the axis of the rod as indicated by the dashed line position shown 
in FIG. 3. 
The muzzle nose piece 24 is allowed to move axially to the FIG. 4 dashed 
line position in order to allow insertion and removal of the cartridge 
barrel insert 11. Pivotal motion of the nose piece is also permitted to 
facilitate insertion and removal of the barrel insert, as will be 
discussed in greater detail below. The nose piece 24 has serrations 33 on 
opposite sides thereof to facilitate gripping between the thumb and 
forefinger so the nose piece can be pulled outwardly and turned about the 
axis of the rod 29. 
A sight rod 35 is mounted between the nose piece 24 and frame 14. 
Preferably, the sight rod 35 is affixed to the nose piece 24 and is 
releasably received within a recess 38 of the frame 14. It is preferred 
that the sight rod 35 be situated over the recess 22 in order to present a 
straight axial reference for sighting purposes and to brace the muzzle 
nose piece 24 in its operative position. The sight rod 35, when used in 
sighting or aiming the pistol, will be used in combination with integral 
sights 39 (FIGS. 2 and 3) situated in the frame 14 and nose piece 24. 
The cartridge shaped barrel insert 11 is shown in substantial detail in 
FIGS. 5 through 7 and in another form in FIGS. 8-10. Generally, the insert 
11 is shaped similarly to the external configuration of a center-fire 
cartridge. However, the insert includes mechanisms that allow a smaller 
bore rimfire cartridge 12 to be fired from it. The insert is preferably 
constructed of steel commonly used for barrel construction in rifles and 
pistols. 
The insert includes basically two independent sections. The barrel section 
50 is provided to receive a cartridge 12. The barrel section 50 extends 
between a breach end 42 and a muzzle end 43. A central bore 45 extends 
between the ends 42 and 43. A shoulder 46 is formed within the breech end 
42 of the barrel section to abut the corresponding rim 47 of a rimfire 
cartridge 12. This relationship is best illustrated in FIGS. 5 and 8. 
The bore 45 shown in FIG. 5 includes standard rifling 48 along its length. 
The rifling 48 is provided to guide and spin the bullet when it is fired. 
This is a particularly useful feature when the insert is used with the 
pistol frame. 
A breech block section 51 is releasably attached to the barrel section 50 
at the breech end 42. The breech block 51 includes mechanisms for firing 
the enclosed cartridge 12 and can be actuated by the primary firing pin 19 
of the pistol, or a standard center-fire firing pin 75 of an appropriate 
large bore weapon 76. 
The breech block 51 extends from a forward end 52 to a back end 53. The 
forward end 52 includes means 54, preferably threads, for releasably 
attaching the breech block to the barrel section. The mating threads 
between the breech block 51 and barrel section 50 are positioned so the 
forward end of the breech block 51 overlaps the shoulder 46 of the bore 
45. This allows easy access to the cartridge 12 both for loading and 
unloading purposes. 
A secondary firing pin is provided at 56 within the breech block 51. The 
back end 57 of the secondary firing pin appears very similar to the primer 
cap of an ordinary center-fire cartridge, presenting a striking surface 
58. The body 59 of the firing pin extends forwardly from the striking 
surface 58 to a pair of pin projections 60 at a pin front end 61. The pin 
projections 60 are diametrically opposed in relation to the central bore 
axis. They are also spaced apart to simultaneously engage the circular rim 
of a rimfire cartridge held within the bore 45. Because there are two pin 
projections 60, it is logical that it will require approximately twice the 
impact produced through the firing pin in order to compress the rim 47 
sufficiently to ignite the enclosed primer material. The dual projections 
60 also assure firing of the small bore cartridge since two areas of the 
rim are struck instead of the usual one. 
A resilient means 62 is provided within the breech block 51 in order to 
yieldably resist motion of the secondary firing pin toward the rim of the 
cartridge 12. Thus, the pin projections 60 are normally urged axially away 
from the cartridge rim 47. This is an extremely important safety feature 
for the present invention. 
The resilient means 62 may be provided in the form of a resilient pad 63 
situated within a bore 67 in the body of the pin 56. The pad 63 is loosely 
mounted between a roll pin 64 and a closed end 66 of the bore 67 in which 
it is received. A compression spring may be substituted for the pad 63 but 
it has been found that a synthetic material, such as a resilient urethane, 
may be used. The roll pin 64 prevents the secondary firing pins 60 and pad 
63 from dropping out of the breech block 51 through the forward end 
thereof. 
Interfitting shoulders 68 between the pin and breech block 51 prevent the 
pin from sliding rearwardly from the breech block. The pad 63 and pin 64 
control the forward motion of the pin toward the center-fire cartridge rim 
47. The yieldable resistance offered by the pad 63 is preselected to 
accommodate the relatively high spring forces applied through the firing 
pins of center fire weapons. Center fire "primer caps" require a stronger 
firing pin impact than do typical rimfire cartridges. The pad 63 absorbs a 
part of the additional impact energy of the weapon firing pin while 
transmitting just enough of such force through the secondary firing pin 
projection 60 to impact and fire the cartridge 12. The pad 63 therefore 
reduces the high impact force of the weapon firing pin to the reduced 
force required for firing a rimfire cartridge with the pin projections 60. 
Normally, the firing pins of the various center fire weapons strike the 
soft brass caps of center fire ammunition and the sharpness or bluntness, 
(within broad limits) is not critical. The shape, hardness, and material 
of firing pins are therefore not standardized with firearms manufacturers. 
This non-standardness becomes a serious problem when using inserts with 
firing pins made of harder material than soft brass since the brittle 
firing pin will readily break unless protected. A conical recess 65 on the 
striking surface 58 of my secondary firing pin 56 allows it to receive the 
various size and shaped large bore firing pins 75 and assures that there 
is 360.degree. contact regardless of the shape. No known prior inserts 
address this problem. 
The conical recess 65 is centered on the striking surface 58. The recess 65 
receives the rounded shoulder of a standard large bore firing pin 75 (FIG. 
8) or the projection 20 of the primary firing pin 19 (FIG. 5) for the 
pistol 10. The conical recess 65 is provided to substantially center the 
axial forces imparted by a firing pin or by the primary pistol firing pin 
19 and to evenly distribute the impact forces between the projection 20 or 
large bore firing pin 75 and the secondary firing pin. The inclined 
surfaces of the recess 65 will engage a considerable surface area of the 
projection or firing pin, and evenly distribute axial force to the 
secondary firing pin 56. The secondary firing pin 56 can therefore be 
constructed of relatively rigid materials that could otherwise damage or 
break standard firing pin ends. 
FIGS. 8, 9 and 10 indicate a version of the present insert specially 
adapted for use in firing from large bore center-fire weapons 76. 
Physically, the insert structure is very similar to that described earlier 
and illustrated in particular in FIG. 5. However, the secondary firing pin 
56 has been extended, along with the axial length of breech block 51. The 
barrel section 50 has been correspondingly shortened. The axial length of 
the barrel section and its included bore 45 is such that a cartridge 12 
will fit within the bore and its bullet or slug 77 will project outwardly 
from the open forward barrel section end. It is preferred that this 
distance be such that an edge 78 of the cartridge 12 is positioned within 
the plane of the open barrel section end 43. The remainder of the inner 
workings for the present insert remain substantially identical to those 
already described. 
A bullet guiding plastic cap 80 is provided to fit over the bullet or slug 
27 projecting from the open barrel end 43. The cap 80 is sized to match 
the caliber or bore size of the weapon in which the cartridge 12 is to be 
fired. The cap 80 can be constructed, as can the remainder of the insert, 
to duplicate virtually any caliber size larger than that of the rimfire 
cartridge. Since rimfire cartridges are typically 0.22 caliber or 0.223 
inch diameter, any caliber larger than 0.223 is suitable for operation 
with an insert and cap of a corresponding size. 
The cap 80 includes an open rearwardly facing cap recess 79 that is 
complementary to the bullet or slug 77 of the rimfire cartridge 12. The 
recess is precisely centered on the longitudinal central axis of the cap 
80. It extends into the cap 80 a distance substantially equal to the 
longitudinal distance in which the bullet or slug 77 protrudes from the 
open insert barrel end 43. The cap can therefore be press fitted by hand 
over the exposed bullet or slug 77 until the rearward end 81 comes into 
abutment with the barrel section end 43 as shown in FIG. 8. The dimensions 
of the recess and physical properties of the cap are such that the cap 
will stay firmly in place once pressed onto the slug. 
It is preferred that the cap 80 be formed of a plastic material such as 
styrene, polyamide, fluorocarbon or other plastic material having a 
relatively low coefficient of friction and high heat resistance. 
An annular wedge groove 82 (FIGS. 9 and 10) is provided at the rearward cap 
end 81. The groove 82 is coaxial with the central longitudinal axis of the 
cap. It forms a peripheral apron 83 adjacent the exterior surface 84 of 
the cap. The peripheral apron 83 is provided to expand against the bore 90 
of the center fire weapon 76, promoting a seal across the weapon bore in 
response to expanding gases from ignition of the powder within cartridge 
12. The apron 83 will expand due to the wedge shaped nature of the groove 
82 and the resilient or flexible nature of the material forming the cap 
80. This feature is best illustrated in FIG. 10 in which expanding gases 
are illustrated behind a slug 77 in the present cap 80. The expanding 
gases operate against the exposed surfaces of the slug 77 and the rearward 
end 81 of the plastic cap. The expanding gases operate against the 
resilient material of the cap to expand the wedge shaped groove 82 and 
thereby press the apron 82 radially outward against the surface of the 
weapon bore 90. The plastic apron slidably engages the barrel and allows 
the barrel to guide the cap 80 and slug 77 through the entire length of 
the weapon bore 90. 
The cap 80, with the annular groove 82 and apron 83 can be formed at a 
slightly smaller diameter than the bore 90. The actual dimension depends 
upon the resilient properties of the plastic material used and the ability 
of the peripheral apron 83 to expand against the bore. This assures 
minimal frictional contact between the exterior cap surface 84 and the 
bore 90 to minimize frictional resistance against movement of the cap 80 
and slug 77 along the bore. However, it is noted that the plastic cap 80 
will have an inherently lower coefficient of friction than the typical 
metal to metal surface contact between a standard slug and weapon bore. 
Optimum obtainable velocity of the cap and slug can therefore be expected. 
A rimfire cartridge 12 is loaded into the insert 10 by unscrewing the 
breech block 51 from the barrel section. A rimfire cartridge is then 
inserted into the bore 45 with the rim 47 engaging the shoulder 46 (FIG. 
5). The breech block 51 is then screwed back onto the barrel section. It 
is noted that the threads and the overlapping arrangement of the breech 
block and barrel section serve to strengthen the entire insert unit. The 
threads also serve to gauge the effective distance between the firing pin 
projections 60 and the cartridge rim 47. It is also noted that the 
resilient means 62 holds the firing pin in a retracted position at all 
times so the cartridge rim is not touched by the firing pin projections 
until sufficient force is applied either through the pistol firing pin 19 
or the firing pin 75 of an appropriate large bore weapon 76. 
The resilient means 62 will also absorb some of the large bore weapon's 
firing pin spring pressure upon firing, which is greater than the average 
rimfire weapon. The purpose of the dual firing pin projections 60 is also 
to further absorb some of the large bore firing pin spring pressure to 
make it more near that of the standard rimfire weapon and to doubly insure 
that the rimfire cartridge fires. 
It sometimes occurs that in manufacture of rimfire cartridges that the 
"paste powder" which is meant to fully fill the inside circumference of 
the shell rim does not occur. Therefore, when the small single point 
firing pin strikes that void area, the result is a "misfire". This is not 
uncommon in rimfire ammunition. The dual projections of the present firing 
pin, however, will nearly completely eliminate misfiring. 
The loaded insert 11, if it is to be fired from a large bore weapon, can be 
carried with other inserts in a pocket or pack until such time that it is 
needed. An example is when a hunter encounters small game that he or she 
may wish to take with a small caliber bullet or bird shot. A "flare load" 
could also be carried in the insert in case of emergencies. 
The present insert may be easily made to be distinguishable from ordinary 
brass cartridges. A primary distinguishing characteristic of the FIG. 5 
version is that it does not have a bullet projecting from the breech end. 
The present insert is also preferably constructed of "blued" steel that is 
easily distinguishable from the bright brass color of ordinary cartridges. 
The insert of FIG. 8 is also easily discernible by the small rimfire 
bullet projecting from the insert panel end 43 or the plastic cap which 
will be provided in a distinctive color. 
The insert is loaded into the barrel of a large bore weapon in the same 
manner as an ordinary cartridge is loaded into the barrel. The weapon is 
aimed and fired in the same manner as it is usually aimed and fired. 
However, the firing pin will strike the secondary firing pin 56 within the 
conical recess 65, moving it forwardly against resistance of the resilient 
means 62 to move the firing pin projections 60 into engagement with the 
cartridge rim 47. The force of engagement between the projections 60 and 
the cartridge rim 47 is sufficient to ignite the "primer" within the rim 
and the adjacent powder within the cartridge case. The expanding gases 
force the bullet from the cartridge end and through the bore 45 where, in 
the FIG. 5 version, the rifling 48 guides the bullet and causes it to spin 
on its axis. The bullet will leave the muzzle end of the insert and will 
move through the barrel of the large bore weapon without touching the 
walls of the bore thereof. The bullet will take the same path (through a 
shorter range) that the standard large bore center fire bullet would if 
fired from the same weapon. 
The insert version shown in FIG. 8 will load into the firearm in much the 
same manner as the FIG. 5 version. However, prior to the loading step, a 
plastic cap 80 is pressed over the exposed bullet or "slug" 77 of the 
rimfire cartridge 12. The cap 80 is simply pressed over the slug 77 until 
the rearward cap end 81 comes into abutment with the insert barrel end 43. 
With the exception of the texture and color 80, the insert now assumes the 
same shape a corresponding large bore cartridge. 
The capped insert will fire in the same manner as described above for the 
FIG. 5 insert version. Travel of the rimfire slug 77, however, is 
influenced by frictional engagement between the cap 80 and bore 90 of the 
firearm, rather than by the rifled insert bore of the FIG. 5 form. The 
slug 77 and expanding gases from burning powder will push the cap 80 
through the weapon bore. As the slug leaves the cartridge case 78, 
expanded gases will press against the wedge groove 82 and cause the 
peripheral apron 83 to expand radially against the firearm bore 90. The 
deformed plastic material of cap 80 will conform to the bore and rifling 
and will be guided as such down the length of the barrel. The expanding 
gases are thus trapped behind the cap and slug, to force the cap 80 and 
slug 77 out the barrel with the barrel influencing or guiding the flight 
in the same manner as it would with a conventional large bore slug. 
The cap 80 will continue along with the slug 77 through its trajectory and 
impact the target. This distinguishes the cap from other known bore 
reducing plastic "sabots" that fit behind the slug and drop from the 
slug's trajectory shortly following departure from the muzzle of the 
firing weapon. The cap 80 increases the weight of the slug 77 and its 
overall size to that of the firing weapon's bore. Flight characteristics 
will change from that normally produced by the rimfire cartridge. Greater 
striking impact and more penetration are realized; both being desirable 
characteristics when the target is small game. 
When the insert has been fired, it is removed from the large bore weapon in 
the same manner that an ordinary cartridge would be removed. The breach 
block 51 is then removed and the spent casing of the rimfire cartridge can 
be removed from the barrel section. This is done either by using a short 
length of rod similar to the sight rod 35 for the pistol, or by simply 
using an available twig or branch of sufficient diameter and length. The 
rod or twig is inserted through the muzzle end 43 along the bore to engage 
the closed end of the cartridge and push it outwardly beyond the shoulder 
46 where it can be pulled free of the barrel section. The barrel can then 
be reloaded and reattached to the breech block for further use. 
The insert 11 of the FIG. 5 form is also as easily utilized by the present 
pistol body. 
To load the insert into the pistol body, the muzzle nose piece 24 is first 
gripped and pulled outwardly to disengage the sight rod 35 from the frame 
recess. The nose piece is also rotated approximately 90.degree. about the 
axis of the rod 29 to the position shown by dashed lines in FIG. 3. This 
moves the sight rod 35 clear of the depression 22. It is noted that when 
the nose piece is pulled out, the compression spring 31 is placed under 
higher compression than when it is released. 
The insert may then be placed in the depression 22 with the breech block 
back end 53 being received within the breech recess 23 and adjacent the 
primary firing pin 19. The nose piece 24 is then gripped again and pulled 
outwardly to move the inner facing surface of the nose piece outwardly 
clear of the muzzle end 43 of the insert. The nose piece is then rotated 
back to the operative position and released so the muzzle end 43 is 
received in the nose piece recess 25 and so the sight rod 35 is received 
in its complementary recess 38 along the frame. The pistol is then loaded 
and ready to fire. 
Firing the pistol involves the simple process of cocking the hammer 17, 
aiming the pistol by using the appropriate sights 39 and sight rod 35, and 
firing by pulling the trigger 18. When the trigger is pulled, the hammer 
strikes the primary firing pin 19, driving it forward against the 
secondary firing pin 56 of the insert. The firing pin projection 20 will 
fit within the conical recess 65 of the secondary firing pin. 
The forward force of the primary firing pin causes axial forward movement 
of the secondary firing pin 56, against the resistance of the resilient 
means 62. This resistance is overcome by the force in the forward 
direction, and the firing pin proceeds on forwardly to bring the two pin 
projections 60 forceably into contact with the rim 47 of the cartridge. 
The cartridge then fires and the bullet leaves the insert through the 
muzzle end 43 of the barrel section. 
Unloading the pistol is accomplished by pulling the muzzle nose piece 24 
outwardly until the sight rod end clears the frame and the nose piece 
recess moves clear of the insert muzzle end 43. The nose piece is then 
rotated to one side and released. The insert can then be removed from the 
frame recess and disassembled to allow access to the spent cartridge 
casing. 
The sight rod 35 is used in this situation to drive the spent casing 
outwardly of the barrel section. This is done simply by inserting the now 
exposed sight rod end into the muzzle end of the bore 45 and moving it 
rearwardly to engage and push the spent cartridge casing from the barrel 
section. After this is done, a fresh cartridge can be inserted into the 
bore 45 and the breech block 51 threaded onto the barrel section. The now 
loaded insert can then be repositioned in the pistol for subsequent 
firing. 
For convenience of having various loads ready to fire, several of the 
loaded inserts 11 may be carried. 
It is noted that with a simple shim (not shown), a single pistol body can 
be made to accommodate barrel inserts 11 that are adapted to be received 
in different large bore weapons. For example, such a shim could be made to 
accommodate cartridge shaped inserts of a standard 30-06 or 0.270 caliber 
rifle cartridges. The "shim" would be held in place in the nose piece by a 
simple set screw (also not shown). The shim would give the 0.270 and, say, 
the 25.06, the same overall length and shoulder/neck measurements as the 
30.06 cartridge case. 
It is also pointed out that the nose piece and pistol frame can be quite 
easily designed to accommodate more than a single cartridge shaped barrel 
insert 11. In fact, it is contemplated that two or more inserts may be 
provided that could simply be shifted into alignment with the firing pin 
19 by simply pulling the nose piece outwardly and rotating it to bring the 
successive insert into firing position. 
In compliance with the statute, the invention has been described in 
language more or less specific as to structural features. It is to be 
understood, however, that the invention is not limited to the specific 
features shown, since the means and construction herein disclosed comprise 
a preferred form of putting the invention into effect. The invention is, 
therefore, claimed in any of its forms or modifications within the proper 
scope of the appended claims, appropriately interpreted in accordance with 
the doctrine of equivalents.