Cam firing mechanism

A multi-lobed partial free-floating cam mechanism is used to cock and sucsively fire a plurality of biased firing pins without allowing a "hang-fire" condition to exist. Initial lifting of the cam mechanism by pivot pin rollers acting on an inclined cam slot stores enough energy to drive the cam through its final rotational mode.

BACKGROUND OF THE INVENTION 
Various means have been used in the prior art to semiautomatically 
successively fire a plurality of projectiles from a launcher. One of the 
prior art means for triggering a multitube launcher utilizes a trigger 
handle assembly having a bellcrank linkage connected to a ratchet drive 
means which has an extension shaft joining the ratchet drive to a firing 
pin rotating cam mechanism. The aforementioned device used a rear cocking 
knob to precock each of the firing pins. Each pull of the trigger by an 
operator released one firing pin which then in turn fired the next round 
from the multitube launcher. 
The problem with the aforementioned prior art caming mechanism was that 
rear hand cocking of the firing pins was a safety hazard. The system often 
required placing the operator's hand behind the gun in the backblast area 
of the rocket motor and subjected the operator to possible injury in the 
event of an inadvertent rocket motor firing. An unexpected firing could 
occur when the firing pin cam follower was stuck on the cam firing lobe 
peak in a "hand-fire" condition. The problem with prior art cocking 
devices which were located in the front or side of a multitube launcher 
was that they generally require the installation of additional linkages 
which are complex to design and costly to install. 
SUMMARY OF THE INVENTION 
The present invention relates to firing pin mechanism that successfully 
cocks and fires a plurality of biased firing pins by means of a 
double-lobed free-floating cam. The initial rotation of the cam which 
lifts the cam on pivot pin rollers stores energy which is subsequently 
used to help drive the cam follower over the cam firing lobe peak thereby 
preventing the occurrence of a "hang-fire" condition. 
An object of the present invention is to provide a free-floating 
double-lobed cam firing mechanism which prevents a firing pin cam follower 
from remaining in a "hand-fire" condition on a actuating cam lobe. 
Another object of the present invention is to provide a free floating 
double-lobed cam firing mechanism for a multitube launcher which permits 
trigger cocking of the firing pin mechanism with reduction of safety 
hazards. 
A further object of the present invention is to provide a free-floating 
double-lobed cam firing mechanism which has enhanced reliability and 
safety because of reduced susceptibility to environmental contamination. 
For a better understanding of the present invention, together with other 
and further objects thereof, reference is made to the following 
descriptions taken in connection with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to FIGS. 1 and 2 a firing pin mechanism assembly 10 is used 
in a four tube rocket launcher not shown. The assembly 10 comprises four 
spring biased firing pin assemblies 12 longitudinally equally spaced at 
90.degree. intervals in housing 14 in firing pin housing bores 15. For 
simplification only one of the four firing pin assemblies 12 are shown in 
FIG. 1. Housing 14 is partially closed at its rear end 16 by disk shaped 
bumper member 18 fixedly attached thereto and a forward end 20 by a front 
cover 22 which is fixedly attached to housing 14 by means of screws 24. A 
double-lobed free-floating cam shaft assembly 26 is axially rotatable 
supported on a first end in housing central drive shaft base 27 by a rear 
bearing member 28 and supported on a second end by a front bearing member 
30 disposed in axial shaft bore 31. Rearward longitudinal movement of 
connecting shaft 32 is prevented by a thrust washer 34 which abuts a first 
pinned collar member 36. The rotational friction forces of connecting 
drive shaft 32 are reduced by an oil seal member 38 and bearings 28 and 
30. The drive shaft assembly 26 carries a second pinned collar member 40 
fixedly attached to connecting shaft 32 intermediate cam bearing sleeve 42 
and first pinned collar 36. Cam bearing sleeve 42 is fixedly positioned 
intermediate second collar 40 and front bearing member 30 and has three 
transversely radially positioned equally spaced pivot pin rollers 44 
fixedly attached to bearing sleeve rear end 46 and connecting shaft 32. A 
double-lobed free-floating cylindrically shaped cam member 48 rotatably 
and slidably fits on cam bearing sleeve 42. Cam member 48 has a forward 
cam end 50 and a rear cam end 52. Referring now to FIGS. 1, 2 and 3, cam 
front end 50 is in rolling contact with cam follower 54. Cam rear end 52 
has three equally spaced symetrically shaped lifting notches 56 therein 
having sloping back edges 58 disposed on the closed end. The pivot pin 
rollers 44 are smaller than the notch width of cam lifting notches 56. 
Each of the firing pin assemblies 12 include a biased helical spring 60 
operatively disposed on a firing pin shaft rear end 62 slidably positioned 
in housing firing pin bores 15 and a firing pin 66 on front end 67 
slidably disposed in a cover firing pin bore 68. A firing pin bore 68. A 
firing pin cover seal 70 is operatively disposed in cover annular counter 
groove 72 to protect the firing pin assembly from the environment. Cam 
follower 54 comprises a cylindrically shaped roller 55 which is rotatably 
attached to a follower pin 74 which is in turn press fitted into the side 
of firing pin shaft 63. Cam 48, as shown in flat pattern view of FIG. 3, 
has a two main lobes, a "firing lobe" 76 and a "secondary lobe" 78 spaced 
180.degree. apart therefrom. 
In operation, the firing pin mechanism 10 is actuated by an operator who 
squeezes a trigger means of the launcher, now shown, which causes 
connecting shaft 32 to rotate 90.degree. clockwise, when viewed from the 
righthand end, for each actuation of the trigger. The rotation of 
connecting shaft 32 results in a lifting of cam 48 by pivot pin roller 44 
from the deep side of notch 56 to the opposite side. This lifting occurs 
due to the resistance of the cam 48 to rotation because of frictional 
loads placed thereon by the biased firing pin assemblies 12. As the 
connecting shaft 32 continues to rotate the cam 48 rotates as driven by 
pivot pin rollers 44 causing cam follower 54a, as shown on FIG. 3, on the 
firing pin assembly 12, next to be fired to roll up the firing lobe ramp 
80. Simultaneously, the follower 54b attached to the firing pin assembly 
12, located diametrically opposite to the aforementioned firing pin 
assembly, rolls up the ramp 82 of the secondary lobe 78. At the same 
instant of time, cam follower 54c oriented 90.degree. from follower 54b 
passes over secondary lobe peak 78 causing the cam 48 to rotate 
independently of connecting shaft 32. Follower 54d which was previously on 
the firing lobe ramp 80 also advances but does not clear the peak of 
firing lobe 76 until the diametrically opposite follower 54c causes cam 
rotation as described above. The free-float rotation of the cam 48 caused 
by the passing of follower 54c over the peak secondary lobe 78 drives the 
firing lobe 78 under or past the firing pin follower 54d permitting the 
biased firing pin spring 60 to push firing pin 66 through seal 70 and to 
thereby initiate a munition, not shown, in the launcher. The firing pin 
partially cocked by the secondary lobe 78 and whose follower is numbered 
54c is not released to the firing position but is slowly moved back down 
the opposite decending secondary lobe ramp 84 to an intermediate position 
determined by cam dwell surface 86. 
The aforedescribed double-lobed, free-floating cam mechanism 10 thus 
mechanically cocks and fires a plurality of firing pins 66 in succession 
and prevents a "hang-fire" condition of a cocked firing pin on or near the 
peak of a cam firing lobe. 
While there has been described and illustrated specific embodiments of the 
invention, it will be obvious that various changes, modifications and 
additions can be made herein without departing from the field of the 
invention which should be limited only by the scope of the appended 
claims.