SUMMARY OF THE INVENTION

The invention disclosed herein is a combined accelerator and jar mechanism, contained within an integral outer housing. Telescopically connected within the outer housing is an upper tubular member, sometimes referred to as the "operating mandrel", and a lower tubular member, sometimes referred to as the "jarring mandrel". The operating mandrel is connected to a "work string" (pipe, coiled tubing or wire) which extends to the surface. The operating mandrel cooperates with the outer housing through an upper or lower accumulator spring means, such that when the operating mandrel is axially displaced, whether upward or downward relative to a neutral position of the outer housing, a respective spring stores or accumulates energy therein.

Upon axial displacement of the operating mandrel, movement of the outer housing is initially precluded by jar means contained in the lower half of the outer housing, until a selected axial force is exceeded. When said selected axial force is exceeded, the entire outer housing is released to move freely in response to force stored within said accumulator spring means, until the outer housing contacts a striker flange of the jarring mandrel. As the jarring mandrel is connected to the stuck object, a jarring impact is thereby transmitted to the stuck object.

As both the accelerator portion of the apparatus (generally corresponding adjacent to operating mandrel) and the jarring portion of the apparatus (generally corresponding to that portion adjacent to the jarring mandrel) are capable of either "up" or "down" strokes, from a medial neutral position, the combined apparatus may be operated so as to deliver any desired number and sequence of strokes, in either direction.

Also disclosed herein is an improved jar latching mechanism, which embodies the attributes of simplicity, ease of manufacture and maintenance, repeatability, durability and is also conveniently field adjustable to a desired latching force (thereby controlling the amount of impact delivered to the stuck object). The latching mechanism includes a set of riqid latch bars containing a generally V shaped lug, which is matingly engageable with a bevelled groove on the jarring mandrel. The upper and lower edges of said latch bars are tapered towards the jarring mandrel and cooperate with an axially disposed latch bar biasing spring, so as to establish the amount of radially inward force holding the latch bar lug into engagement with the bevelled groove of the jarring mandrel. The greater force which the latch bar biasing spring exerts on the tapered edges of the latch bars, the more radially inward force is exerted by the latch bars on the jarring mandrel, and therefore a greater axial force is required to unseat the latching mechanism to cause a jarring impact to be delivered to the stuck object. A threaded adjusting bushing cooperates with the outer housing and the upper end of the latch bar biasing spring, in order to provide a convenient field means for selecting a desired amount of jarring impact to be delivered to the stuck object.