Accommodating piston seat for differential-stroke cycle engines

1. A piston seat apparatus for a differential-stroke cycle combustion engine, the combustion engine including one or more two-part pistons, each two-part piston having a first piston part and a second piston part that moves separately from the first piston part during exhaust and intake strokes of the engine, the apparatus comprising:

a piston seat cover operatively associated with the first piston part, the piston seat cover being adapted for abutting engagement with the second piston part,

wherein, upon abutting engagement, the piston seat cover is adapted to move relative to the first piston part thereby at least partially absorbing impact forces applied between the first piston part and the second piston part;

a piston seat cup coupled to the first piston part, wherein the piston seat cover is adapted to sealably slidingly engage the piston seat cup, thereby to define a sealed piston seat cavity;

a fluid ingress aperture in alignment with a cooperating piston rod passage and piston pin inlet for a portion of a combustion cycle of the engine, thereby allowing fluid to enter the piston seat cavity; and

a fluid egress aperture in alignment with a cooperating piston pin passage and piston rod outlet for a portion of the combustion cycle of the engine, thereby allowing fluid to exit the piston seat cavity,

wherein during a first predetermined period of operation of the combustion engine, fluid flow into the piston seat cavity is interrupted by misaligning the piston rod passage and piston pin inlet and closing the fluid ingress aperture; and

wherein during a second predetermined period of operation, fluid out of the piston is interrupted by misaligning the piston pin passage and piston rod outlet and closing the egress aperture; thereby preserving a predetermined amount of fluid within the piston seat cavity volume, until fluid flow recommences.

2. The apparatus according to claim 1 , wherein:

the first piston part and the second piston part move co-axially; and the piston seat cover is adapted to move in an axial direction with respect to the first piston part.

3. The apparatus according to claim 1 , wherein:

the piston seat cup is integrally formed with the first piston part.

4. The apparatus according to claim 1 , wherein:

relative movement between the piston seat cover and the piston seat cup enables the piston seat cavity to have a variable volume.

5. The apparatus according to claim 1 , wherein:

the piston seat cavity is fillable with engine oil during operation of the combustion engine.

6. The apparatus according to claim 1 , further comprising a piston seat spring disposed within the piston seat cavity configured to bias the piston seat cover in a first direction.

7. The apparatus according to claim 6 , wherein during a third predetermined period of operation, the second piston part abuts the piston seat cover and moves the piston seat cover toward the first piston part, thereby compressing the piston seat spring and reducing the piston seat cavity volume.

8. The apparatus according to claim 7 , wherein during a fourth predetermined period of operation, fluid flow is interrupted as both the ingress and egress apertures are closed thereby maintaining a piston seat cavity volume unchanged until fluid flow through either the ingress or egress aperture recommences.

9. A piston seat apparatus for a differential-stroke cycle combustion engine, the combustion engine including one or more two-part pistons, each two-part piston having a first piston part and a second piston part operated by a piston stem which is slidably coupled to the first piston part, the apparatus comprising:

a piston seat cover operatively associated with the first piston part, the piston seat cover being adapted for abutting engagement with the second piston part, wherein, upon abutting engagement, the piston seat cover is adapted to move relative to the first piston part thereby at least partially absorbing impact forces applied between the first piston part and the second piston part;

a piston seat cup coupled to the first piston part, wherein the piston seat cover is adapted to sealably slidingly engage the piston seat cup, thereby to define a sealed piston seat cavity;

a fluid ingress aperture in alignment with a cooperating piston rod passage and piston pin inlet for a portion of a combustion cycle of the engine, thereby allowing fluid to enter the piston seat cavity; and

a fluid egress aperture in alignment with a cooperating piston pin passage and piston rod outlet for a portion of the combustion cycle of the engine, thereby allowing fluid to exit the piston seat cavity.

10. The apparatus according to claim 9 , wherein:

the first piston part and the second piston part move co-axially and the piston seat cover is adapted to move in an axial direction with respect to the first piston part.

11. The apparatus according to claim 9 , wherein:

the piston seat cup is integrally formed with the first piston part.

12. The apparatus according to claim 9 , wherein:

relative movement between the piston seat cover and the piston seat cup enables the piston seat cavity to have a variable volume.

13. The apparatus according to claim 9 , wherein:

during a first predetermined period of operation of the combustion engine, fluid flow into the piston seat cavity is interrupted by misaligning the piston rod passage and piston pin inlet and closing the fluid ingress aperture; and

during a second predetermined period of operation, fluid out of the piston is interrupted by misaligning the piston pin passage and piston rod out let and closing the egress aperture; thereby preserving a predetermined amount of fluid within the piston seat cavity volume, until fluid flow recommences.

14. The apparatus according to claim 9 , further comprising a piston seat spring disposed within the piston seat cavity configured to bias the piston seat cover in a first direction.

15. The apparatus according to claim 9 , wherein during a third predetermined period of operation, the second piston part abuts the piston seat cover and moves the piston seat cover toward the first piston part, thereby compressing the piston seat spring and reducing the piston seat cavity volume.

16. The apparatus according to claim 15 , wherein during a fourth predetermined period of operation, fluid flow is interrupted as both the ingress and egress apertures are closed thereby maintaining a piston seat cavity volume unchanged until fluid flow through either the ingress or egress aperture recommences.

17. The apparatus according to claim 9 , wherein preserving the predetermined amount of fluid within the piston seat cavity volume determines a piston seat cover height relative to the first piston part.