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Retractable ball seats having a housing, a seat, and a plug such as a ball are disclosed. The seat has a retracted position that prohibits the ball from passing through the passageway and an expanded position that permits the ball to pass through the passageway. A time delay material, such as a diss

Retractable ball seats having a housing, a seat, and a plug such as a ball are disclosed. The seat has a retracted position that prohibits the ball from passing through the passageway and an expanded position that permits the ball to pass through the passageway. A time delay material, such as a dissolvable material, maintains the seat in the retracted position. The time delay material disintegrates, degrades, or dissolves within a known period of time such that the retractable ball seat can be placed in a desired location in the wellbore and the ball will be released through the passageway within a known period of time.

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What is claimed is: 1. An apparatus for selectively closing a well conduit to enable pressure applied to the conduit to actuate a downhole tool, the apparatus comprising: a housing for connection into a conduit disposed in a well and having a bore disposed longitudinally therein; a seat disposed wi

What is claimed is: 1. An apparatus for selectively closing a well conduit to enable pressure applied to the conduit to actuate a downhole tool, the apparatus comprising: a housing for connection into a conduit disposed in a well and having a bore disposed longitudinally therein; a seat disposed within the bore, the seat having a non-dissolvable expandable member having a retracted position and an expanded position; at least one dissolvable material operatively associated with the non-dissolvable expandable member such that the at least one dissolvable material maintains the non-dissolvable expandable member in the retracted position prior to dissolution; and a plug element adapted to be disposed into the conduit, the plug element landing on the seat and blocking fluid flow through the conduit when the non-dissolvable expandable member is in the retracted position to enable fluid pressure to be applied to the conduit for actuating a well tool connected into the conduit, wherein, the movement of the non-dissolvable expandable member from the retracted position to the expanded position is facilitated by dissolution of the dissolvable material, thereby permitting the plug element to pass completely through the seat. 2. The apparatus of claim 1, wherein the at least one dissolvable material comprises a polymer. 3. The apparatus of claim 2, wherein the polymer comprises a bio-degradable polymer. 4. The apparatus of claim 2, wherein the polymer comprises a polyvinyl-alcohol based polymer. 5. The apparatus of claim 1, wherein the non-dissolvable expandable member moves axially relative to an axis of the housing when moving from the retracted to the expanded position. 6. The apparatus of claim 1, wherein the non-dissolvable expandable member comprises a collet having a tubular wall containing a plurality of slots that define fingers with free ends at the first end of the tubular wall, the fingers being flexible to define a smaller diameter at the free ends while in the refracted than when in the expanded position; and the dissolvable material is located on an exterior portion of the collet for retaining the fingers in the retracted position until dissolution. 7. The apparatus of claim 6, wherein the at least one dissolvable material is disposed within the slots. 8. The apparatus of claim 1, wherein the non-dissolvable expandable member has at least one slot and the at least one dissolvable material is disposed within the at least one slot. 9. The apparatus of claim 8, wherein the non-dissolvable expandable member is resiliently biased toward the expanded position. 10. The apparatus of claim 1, wherein the non-dissolvable expandable member comprises: a collet sleeve having a base and a plurality of resilient fingers, terminating in free ends opposite the base, the free ends defining an inner diameter that is smaller than an inner diameter of the base while in the retracted position and an inner diameter at least equal to the inner diameter of the base while in the expanded position. 11. The apparatus of claim 1, wherein the non-dissolvable expandable member comprises: a collet sleeve having a base and a plurality of resilient fingers, terminating in free ends opposite the base; and wherein the apparatus further comprises: a recess in the bore of the housing, the free ends of the fingers being above the recess while in the retracted position; and the dissolvable material prevents the collet sleeve from moving downward, until dissolved, to the expanded position wherein the free ends of the fingers spring outward into the recess. 12. An improvement in a retractable ball seat located within a string of conduit in a well, the ball seat comprising an expandable collet for releasably trapping a plug member dropped down the conduit, the improvement comprising: at least one dissolvable material disposed adjacent the expandable collet, preventing the expandable collet from expanding until the dissolvable material is dissolved. 13. The retractable ball seat of claim 12, wherein the at least one dissolvable material comprises a polymer. 14. The retractable ball seat of claim 12, wherein the polymer comprises a bio-degradable polymer. 15. The retractable ball seat of claim 12, wherein the dissolvable material surrounds at least part of the collet to prevent the collet from expanding. 16. The retractable ball seat of claim 12, wherein the collet and the plug member move axially relative to the conduit to expand, and the dissolvable material prevents the axial movement. 17. The retractable ball seat of claim 12, wherein the collet comprises a sleeve having a base and a plurality of slots, defining flexible, resilient fingers with free ends opposite the base; and the dissolvable material is located in the slots. 18. A method of actuating a downhole tool disposed in the bore of a well, the method comprising the steps of: (a) providing a seat having a retracted position and an expanded position; (b) lowering the seat and a downhole tool on a string of conduit into a bore of a well while the seat is retained in the retracted position with a dissolvable material; then (c) inserting a plug member into the conduit and landing the plug member on the seat; then (d) pumping fluid into the conduit, which is blocked by the plug member on the seat, thereby causing pressure within the conduit to increase to actuate the well tool; then (e) dissolving the dissolvable material; and then, (f) expanding the seat from the retracted position to the expanded position, and allowing the ball to move completely through the seat. 19. The method of claim 18, wherein the seat is resiliently biased to the expanded position, and dissolution of the dissolvable material allows the bias of the seat to move the seat to the expanded position. 20. The method of claim 19, wherein in step (f), the seat is moved downward relative to the conduit. 21. An apparatus for selectively closing a well conduit to enable pressure applied to the conduit to actuate a downhole tool, the apparatus comprising: a housing for connection into a conduit disposed in a well and having a bore disposed longitudinally therein; a seat disposed within the bore, the seat having a retracted position and an expanded position; at least one dissolvable material operatively connected to the seat such that the at least one dissolvable material maintains the seat in the retracted position prior to dissolution, the at least one dissolvable material comprises a bio-degradable polymer; and a plug element adapted to be disposed into the conduit, the plug element landing on the seat and blocking fluid flow through the conduit when the seat is in the retracted position to enable fluid pressure to be applied to the conduit for actuating a well tool connected into the conduit, wherein, the movement of the seat from the retracted position to the expanded position is facilitated by dissolution of the dissolvable material, thereby permitting the plug element to pass completely through the seat. 22. An apparatus for selectively closing a well conduit to enable pressure applied to the conduit to actuate a downhole tool, the apparatus comprising: a housing for connection into a conduit disposed in a well and having a bore disposed longitudinally therein; a seat disposed within the bore, the seat having a retracted position and an expanded position; at least one dissolvable material operatively connected to the seat such that the at least one dissolvable material maintains the seat in the retracted position prior to dissolution, the at least one dissolvable material comprises a polyvinyl-alcohol based polymer; and a plug element adapted to be disposed into the conduit, the plug element landing on the seat and blocking fluid flow through the conduit when the seat is in the refracted position to enable fluid pressure to be applied to the conduit for actuating a well tool connected into the conduit, wherein, the movement of the seat from the refracted position to the expanded position is facilitated by dissolution of the dissolvable material, thereby permitting the plug element to pass completely through the seat. 23. An apparatus for selectively closing a well conduit to enable pressure applied to the conduit to actuate a downhole tool, the apparatus comprising: a housing for connection into a conduit disposed in a well and having a bore disposed longitudinally therein; a seat disposed within the bore, the seat having a refracted position and an expanded position and the seat moving axially relative to an axis of the housing when moving from the refracted to the expanded position; at least one dissolvable material operatively connected to the seat such that the at least one dissolvable material maintains the seat in the refracted position prior to dissolution; and a plug element adapted to be disposed into the conduit, the plug element landing on the seat and blocking fluid flow through the conduit when the seat is in the refracted position to enable fluid pressure to be applied to the conduit for actuating a well tool connected into the conduit, wherein, the movement of the seat from the refracted position to the expanded position is facilitated by dissolution of the dissolvable material, thereby permitting the plug element to pass completely through the seat.