Vacuum hydrastatic jar accelerator

Claim 2

A well jar accelerator comprising: a tubular internal mandrel terminating in a sub at it lower end and having an annular piston near its upper end; a tubular external mandrel slideably enclosing said piston and internal mandrel and terminating in a sub at its lower end, said upper sub being provided for connecting the tool to a drill string, and said lower sub for connecting said tool to a fishing tool assembly including a jar, whereby said accelerator may be extended by lifting on said drill string and returned to normal contracted condition by lowering said drill string; means forming an annular vacuum cylinder chamber in said external mandrel which is closed at its upper end and in which said piston makes a sealed sliding fit to produce an approximate vacuum therein, above said piston, when said accelerator is so extended; means limiting the maximum extensibility of said accelerator, there being passage means accessible to the liquid confined within said drill string and said accelerator and communicating with said cylinder chamber beneath said annular piston whereby the hydrastatic pressure existing in said liquid may impinge upon the bottom of said piston to impart an upward thrust on said internal mandrel which is transmitted to said jar coincident with the extension of said accelerator and during the tensioning and tripping of said jar; and a seal disc means provided in said lower sub for temporarily blocking the escape of fluid downwardly from said accelerator.

Claim 3

A well jar accelerator comprising: a tubular internal mandrel terminating in a sub at its lower end and having an annular piston near its upper end; a tubular external mandrel slideably enclosing said piston and internal mandrel and terminating in a sub at its upper end, said upper sub being provided for connecting the tool to a drill string, and said lower sub for connecting said tool to a fishing tool assembly including a jar, whereby said accelerator may be extended by lifting on said drill string and returned to normal contracted condition by lowering said drill string; means forming an annular vacuum cylinder chamber in said external mandrel which is closed at its upper end and in which said piston makes a sealed sliding fit to produce an approximate vacuum therein, above said piston, when said accelerator is so extended; means limiting the maximum extensibility of said accelerator, there being passage means accessible to the liquid confined within said drill string and said accelerator and communicating with said cylinder chamber beneath said annular piston whereby the hydrastatic pressure existing in said liquid may impinge upon the bottom of said piston to impart an upward thrust on said internal mandrel which is transmitted to said jar coincident with the extension of said accelerator and during the tensioning and tripping of said jar; said cylinder chamber being closed at its upper end by a cylinder head formed by said upper sub and having a central bore provided with O-ring seal means; and a tubular sleeve provided on said piston and slideably axially extending upwardly through said cylinder head to form an expansible vacuum chamber between said head, said piston, said sleeve and said external mandrel, said internal mandrel including a smooth middle sleeve which connects said piston to said bottom sub, and wherein said bottom sub embodies a male spline sleeve to which said middle sleeve connects; said external mandrel embodying a smooth Bore middle sub having O-ring seal means which slideably receives said middle sleeve, and a female spline sleeve which slideably receives and meshes with said male spline sleeve to transmit torque between said mandrels; said passage means being provided in said smooth middle sleeve near its upper end.

Claim 4

A well jar accelerator comprising: a tubular internal mandrel terminating in a sub at its lower end and having an annular piston near its upper end; a tubular external mandrel slideably enclosing said piston and internal mandrel and terminating in a sub at its upper end, said upper sub being provided for connecting the tool to a drill string, and said lower sub for connecting said tool to a fishing tool assembly including a jar, whereby said accelerator may be extended by lifting on said drill string and returned to normal contracted condition by lowering said drill string; means forming an annular vacuum cylinder chamber in said external mandrel which is closed at its upper end and in which said piston makes a sealed sliding fit to produce an approximate vacuum therein, above said piston, when said accelerator is so extended; means limiting the maximum extensibility of said accelerator, there being passage means accessible to the liquid confined within said drill string and said accelerator and communicating with said cylinder chamber beneath said annular piston whereby the hydrastatic pressure existing in said liquid may impinge upon the bottom of said piston to impart an upward thrust on said internal mandrel which is transmitted to said jar coincident with the extension of said accelerator and during the tensioning and tripping of said jar; said cylinder chamber being closed at its upper end by a cylinder head formed by said upper sub and having a central bore provided with O-ring seal means; and a tubular sleeve provided on said piston and slideably axially extending upwardly through said cylinder head to form an expansible vacuum chamber between said head, said piston, said sleeve and said external mandrel, said internal mandrel including a smooth middle sleeve which connects said piston to said bottom sub, and wherein said bottom sub embodies a male spline sleeve to which said middle sleeve connects; said external mandrel embodying a smooth Bore middle sub having O-ring seal means which slideably receives said middle sleeve, and a female spline sleeve which slideably receives and meshes with said male spline sleeve to transmit torque between said mandrels; said passage means being provided in said smooth middle sleeve near its upper end.