Elastic projectile propulsion systems and methods

Abstract

An elastic projectile propulsion system deploys a plurality of springs that bias a common launching cord via a plurality of block and tackle pulleys. Each sheave of the pulley is coupled to the moveable end of a spring such that the force of each spring contributes to the energy imparted to a projectile by the launching cord without adding significant friction or inertial resistance.

What is claimed is: 
     
         1 . A propulsion device, comprising:
 a forward spring member having a forward spring member proximal end and a forward spring member distal end, wherein the distal end of the forward spring member connects to a first brace and the proximal end of the forward spring member connects to a distal moveable pulley block,   a rearward spring member having a rearward spring member proximal end and a rearward spring member distal end, wherein the distal end of the rearward spring member connects to a proximal moveable pulley block and the proximal end of the rearward spring member connects to a second brace,   at least one forward pulley coupled to the forward spring member proximal end and at least one rearward pulley connected to the rearward spring member distal end, and   a launching cord engaging the forward pulley and the rearward pulley.   
     
     
         2 . The propulsion system of  claim 1 , wherein the at least one forward pulley and the at least one rearward pulley comprise a counteracting block and tackle pulley assembly which couples an elastic energy stored in the forward spring member and the rearward spring member when the launch cord is drawn rearward. 
     
     
         3 . The propulsion device of  claim 1 , further comprising a rail with a distal fixed brace at a distal end thereof and a proximal fixed brace at a proximal end thereof, the distal fixed brace supporting the first moveable brace and the proximal fixed brace supporting the second moveable brace. 
     
     
         4 . The propulsion device of  claim 3 , wherein the rail is configurable to vertically move while remaining stationary horizontally. 
     
     
         5 . The propulsion device of  claim 1 , further comprising a cocking mechanism. 
     
     
         6 . The propulsion device of  claim 1 , wherein the propulsion device has a width of 12 inches or less. 
     
     
         7 . The propulsion device of  claim 1 , further comprising a trigger assembly. 
     
     
         8 . The propulsion device of  claim 1 , wherein the at least one forward pulley comprises a first forward pulley, the device further comprising a second forward pulley. 
     
     
         9 . The propulsion device of  claim 1 , wherein the forward spring member comprises a first forward spring member and the rearward spring member comprises a first rearward spring member, the device further comprising:
 a second forward spring member; and   a second rearward spring member.   
     
     
         10 . The propulsion device of  claim 9 , wherein the first and second forward spring members and the first and second rearward spring members are combined in parallel banks, wherein a first one of the parallel banks engages the first moveable pulley block and a second one of the parallel banks engages the second movable pulley block. 
     
     
         11 . A propulsion device for propelling a projectile therefrom, comprising:
 an elongated member having a proximal fixed base and a distal fixed base;   a forward spring member attached at a distal end thereof to the distal fixed base;   a distal moveable pulley block attached to a proximal end of the forward spring member;   at least a first and second distal pulley spaced apart and disposed on the distal moveable pulley block;   a rearward spring member attached at a proximal end thereof to the proximal fixed base;   a proximal moveable pulley block attached to a distal end of the rearward spring member;   at least one proximal pulley disposed on the proximal moveable pulley block; and   a launching cord spanning between the at least one proximal pulley and the first and second distal pulleys.   
     
     
         12 . The propulsion device of  claim 11 , wherein the launching cord is attached at a first end to the proximal moveable pulley block and extends about the first distal pulley, returns to the at least one proximal pulley, extends back to the first distal pulley, continues to the second distal pulley, extends to the at least one proximal pulley, back to the second distal pulley, and terminates at a second end attached to the proximal moveable pulley block. 
     
     
         13 . The propulsion device of  claim 12 , wherein at least one of the first end and the second end of the launching cord is attached to an adjustment mechanism to adjust a length of the launching cord. 
     
     
         14 . The propulsion device of  claim 11 , wherein a launch cord center is disposed between the first and second distal pulleys, wherein the launch cord center is configured to receive a portion of one end of the projectile, wherein the launch cord center is moved proximally to achieve a cocked configuration. 
     
     
         15 . The propulsion device of  claim 11 , further comprising a passive safety mechanism configured to prevent unintentional discharge of the projectile when the propulsion system is in a cocked configuration. 
     
     
         16 . The propulsion device of  claim 11 , further comprising:
 a distal moveable brace interconnecting a distal end of the forward spring with the distal fixed brace, the distal moveable brace permitting movement between the distal end of the forward spring and the distal fixed brace; and   a proximal moveable brace interconnecting a proximal end of the rearward spring with the proximal fixed brace, the proximal moveable brace permitting movement between the proximal end of the rearward spring and the proximal fixed brace.   
     
     
         17 . The propulsion device of  claim 11 , further comprising an adjustable over-molded center rail configured to support the projectile, the adjustable over-molded center rail running along a length of the rail and being adjustable to adjust the position of the projectile relative to the rail. 
     
     
         18 . The propulsion device of  claim 11 , further comprising a launching cord catch operable to secure the launching cord in a cocked configuration when the projectile is absent, thereby preventing dry-firing of the propulsion system. 
     
     
         19 . The propulsion device of  claim 11 , further comprising a foot claw resiliently extendable from the distal end of the rail. 
     
     
         20 . A propulsion device, comprising:
 a rail comprising a proximal fixed base and a distal fixed base;   a forward spring member attached at a distal end thereof to the distal fixed base;   a distal moveable pulley block attached to a proximal end of the forward spring member;   at least a first and second distal pulley spaced apart and disposed on the distal moveable pulley block;   at rearward spring member attached at a proximal end thereof to the proximal fixed base;   a proximal moveable pulley block attached to a distal end of the rearward spring member;   at least one proximal pulley disposed on the proximal moveable pulley block; and   a launching cord spanning between the at least one proximal pulley and the first and second distal pulleys, wherein   when the launching cord is pulled proximally from a launching cord center region formed between the first and second distal pulleys, a first force is exerted on the distal moveable pulley block by the forward spring member and a second force is exerted on the proximal moveable pulley block by the rearward spring member; and   a quantity of the proximal pulleys, a quantity of the distal pulleys, a configuration of the launching cord, and a spring constant of the rearward and forward spring members are chosen to substantially balance the first force and the second force.   
     
     
         21 . The propulsion device of  claim 20 , wherein the launching cord is attached at the first end to the proximal moveable pulley block and extends about the first distal pulley, returns to the at least one proximal pulley, extends back to the first distal pulley, continues to the second distal pulley, extends to the at least one proximal pulley, back to the second distal pulley, and terminates at the second end attached to the proximal moveable pulley block. 
     
     
         22 . The propulsion device of  claim 20 , wherein:
 the forward spring includes at least one set of forward springs, the at least one set including a first forward spring and a second forward spring, the first and second forward springs being disposed on opposite sides of the rail; and   the rearward spring includes at least one set of rearward springs, the at least one set including a first rearward spring and a second rearward spring, the first and second rearward springs being disposed on opposite sides of the rail.