What is claimed is:
1. A magnetic recording and reproduction apparatus, comprising:
a main chassis having a rotatable head cylinder provided thereon; and
a sub chassis on which a tape cassette is mountable;
wherein:
the sub chassis is movable with respect to the main chassis between a tape cassette mountable position and a tape pull-out completion position, and the tape cassette mountable position is a position at which the tape cassette is mountable on the sub chassis and the tape pull-out completion position is a position at which information recording to, and information reproduction from, the tape which has been pulled out from the tape cassette and wound around the rotatable head cylinder can be performed;
a pivotable body is provided on the main chassis; the pivotable body has a projection provided thereon; and the projection on the pivotable body is engaged with a cam groove in the sub chassis so as to pivot the pivotable body, and thus the cam groove is restricted by the projection on the pivotable body, so that the sub chassis moves with respect to the main chassis;
the cam groove has a width which is substantially identical to the diameter of the projection on the pivotable body; and
the cam groove includes a first arc portion, a second arc portion continuous with the first arc portion, and a straight portion continuous with the second arc portion; and the first arc portion and the second arc portion have identical radii, and are projected in opposite directions to each other.
2. A magnetic recording and reproduction apparatus, according to claim 1, wherein when the sub chassis is at the tape cassette mountable position, the projection is engaged with the first arc portion; when the sub chassis is at the tape pull-out completion position, the projection is engaged with the second arc portion; and when the sub chassis is between the tape cassette mountable position and the tape pull-out completion position, the projection is engaged with one of the straight portion and the second arc portion.
3. A magnetic recording and reproduction apparatus, according to claim 1, wherein a radius of an arc passing through the center of the first arc portion in the circumferential direction thereof, a radius of an arc passing through the center of the second arc portion in the circumferential direction thereof, and a radius of an arc drawn by the center of the projection on the pivotable body when the projection on the pivotable body moves about the center of the pivotable body, are identical to each other.
4. A magnetic recording and reproduction apparatus, according to claim 1, wherein:
when the projection is at a tape cassette take-out position, the projection is engaged with the first arc portion at a first position of the first arc portion, and when the projection is at a tape cassette insertable position, the projection is engaged with the first arc portion at a second position of the first arc portion which is different from the first position of the first arc portion; and
when the projection is at a tape running position, the projection is engaged with the second arc portion at a first position of the second arc portion, and when the projection is at a stop position, the projection is engaged with the second arc portion at a second position of the second arc portion which is different from the first position of the second arc portion.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A threaded joint for steel pipes comprising a pin and a box, the pin having a male thread and a lip comprising (i) a sealing surface and (ii) a nose portion provided with a shoulder surface, the box having a female thread, a sealing surface and a shoulder surface, the male thread being interengaged with the female thread, the sealing surface of the pin being in sealing contact with the corresponding sealing surface of the box, the shoulder surface of the pin being arranged at an end face of the pin, the sealing surface of the pin being located on a pipe end side near the male thread, the nose portion existing between the sealing surface and the shoulder surface, said nose portion not contacting a portion of the box facing said the nose portion of the pin, characterized in that the shoulder surface of the pin comprises two distinct adjacent surfaces, main shoulder in the inner side and sub shoulder in the outer side, and in that the corresponding shoulder surface of the box facing the shoulder surfaces of the pin comprises two distinct adjacent surfaces, main shoulder in the inner side and sub shoulder in the outer side, said main shoulder surfaces of the pin and box being disposed such as to prevent a radially inward deformation of the lip end, said sub shoulder surfaces of pin and box being disposed such as to limit a radially outward deformation of the lip end, said main shoulder of the pin having a greater radial dimension than said sub shoulder of the pin, at least said main shoulder surface of the pin being in axial abutment with at least the corresponding main shoulder surface of the box.
2. A threaded joint according to claim 1, wherein the main shoulder surface of the pin is a reverse shoulder surface having a negative angle with respect to as plane perpendicular to the joint axis.
3. A threaded joint according to claim 1, wherein the sub shoulder surface of the pin has a positive angle with respect to a plane perpendicular to the joint axis.
4. A threaded joint according to claim 1, wherein only the main shoulder surface among the shoulder surfaces at the end of the pin is in axial abutment with the corresponding main shoulder surface of the box.
5. A threaded joint according to claim 1, wherein at least a part of the nose portion of the pin has an outside peripheral surface which is not in prolongation of the sealing surface of the pin.
6. A threaded joint according to claim 1, wherein the sub shoulder surface of the pin is designed to interfere with the sub shoulder surface of the box, the geometrical diametric interference between the sub shoulder surfaces of the pin and box being equal to or less than 1.1 times the geometrical diametric interference between the sealing portions of the pin and box.
7. A threaded joint according to claim 6, wherein the geometrical diametric interference between the sub shoulder surfaces of the pin and box is substantially equal to the geometrical diametric interference between the sealing portions of the pin and box.
8. A threaded joint according to claim 2, wherein the angle of the reverse shoulder with respect to a plane perpendicular to the joint axis is between 5 and 25 degrees.
9. A threaded joint according to claim 1, wherein the shoulder surfaces are substantially frusto-conical.
10. A threaded joint according to claim 1, wherein the main shoulder surface and the sub shoulder surface of the pin can be supported by the corresponding main shoulder surface and the sub shoulder surface of the box when they receive compressive load.
11. A threaded joint according to claim 1, wherein the sealing surfaces of the pin and the box are sloping with regard to the axis of the threaded joint of an angle comprised between 5 and 25 degrees.
12. A threaded joint according to claim 1, wherein the sub shoulder surfaces of the pin and the box are sloping with regard to the axis of the threaded joint of an angle comprised between 5 and 30 degrees.
13. A threaded joint according to claim 1, wherein the slope of the sub shoulder surfaces is greater than the slope of the sealing surfaces.
14. A threaded joint according to claim 1, wherein a main part of the nose portion of the pin is in a clearance fit with the facing portion of the box with a minimum clearance fit value of 0.1 mm on diameters.
15. A threaded joint according to claim 1, wherein the sealing surface of the pin, the outside surface of the nose portion of the pin and sub shoulder surface of the pin are not aligned and wherein the sealing surface of the box, the inner surface of the portion of the box facing the outside surface of the nose portion of the pin and the sub shoulder surface of the box are not aligned.
16. A threaded joint according to claim 1, wherein the slope of the sealing surface of the box, the inner surface of the portion of the box facing the outside surface of the nose portion of the pin, and the sub shoulder portion of the box is monotonic.
17. A threaded joint according to claim 1, wherein the pin comprises a rounded apex between the sub shoulder surface and the main shoulder surface, with a radius lower than 1.5 mm.
18. A threaded joint according to claim 1, wherein one of the sealing surface of the pin and of the sealing surface of the box is a frusto-conical surface and the other sealing surface comprises a torical surface having a radius of curvature larger than 20 mm or the combination of the said torical surface and a frusto-conical surface.
19. A threaded joint according to claim 1, wherein both sub shoulder surfaces of pin and box are frusto-conical surfaces.
20. A threaded joint according to claim 1, wherein the radial dimension of the main shoulder is at least 1.5 times greater than the radial dimension of the sub shoulder.
21. A threaded joint according to claim 1, wherein the outside peripheral surface of the nose portion of the pin and the inner surface of the portion of the box facing said the nose portion of the pin have substantially cylindrical shape.
22. A threaded joint according to claim 1, wherein the outside peripheral surface of the nose portion of the pin and the inner surface of the portion of the box facing said the nose portion of the pin have substantially frusto-conical shape, the taper angle is less than 10 degree.
23. A threaded joint according to claim 1, wherein the shoulder surface of at least one member of the pin and box has at least one groove which extend from the space between the nose portion of the pin and the portion of the box opposing the nose portion to the interior space of the threaded joint.
24. A threaded joint according to claim 23, wherein the groove comprises a first groove portion formed on the sub shoulder and a second groove portion formed on the main shoulder which directly communicates with the first groove portion at the interface between the sub shoulder and the main shoulder.
25. A threaded joint according to claim 23, wherein the groove comprises a first groove portion formed on the sub shoulder and a second groove portion formed on the main shoulder which does not directly communicates with the first groove portion at the interface between the sub shoulder and the main shoulder, the second groove portion communicating with the first groove portion through a connecting channel.
26. A threaded joint according to claim 25, wherein the connecting channel is a concavity formed on the shoulder surface of the box.
27. A threaded joint according to claim 25, wherein the connecting channel is a concavity formed on the shoulder surface of the pin.
28. A threaded joint according to claim 26, wherein the concavity is formed by chamfering or grooving.