Extendable pivot shaft mechanism, and an extendable pivot shaft mechanism of a camera for pivoting a rotatable grip on a camera body

1. An extendable pivot shaft mechanism of a camera for pivoting a rotatable grip on a camera body to allow said rotatable grip both to rotate about a rotational axis and to move along said rotational axis relative to said camera body,

wherein said extendable pivot shaft mechanism comprises an inner shaft, a middle cylinder and an outer cylinder which are concentrically arranged about said rotational axis,

wherein said inner shaft and said outer cylinder are fixed to one and the other of said grip and said camera body, respectively,

wherein one of said inner shaft and said outer cylinder serves as a rotatable shaft element which is rotatable about said rotational axis relative to said middle cylinder,

wherein the other of said inner shaft and said outer cylinder serves as a linearly movable shaft element which is linearly movable along said rotational axis relative to said middle cylinder; and

a click-stop mechanism, provided between said middle cylinder and said linearly movable shaft element, for stopping said linearly movable shaft element moving along said rotational axis relative to said middle cylinder with a click action when said middle cylinder and said linearly movable shaft element relatively move along said rotational axis;

wherein said click-stop mechanism comprises:

at least one click recess formed on one of an outer peripheral surface of said middle cylinder and an inner peripheral surface of said outer cylinder;

at least one ball accommodation hole formed on the other of an outer peripheral surface of said middle cylinder and in inner peripheral surface of said outer cylinder extending in a radial direction, said ball accommodation hole facing said click recess when the axial positions of said ball accommodation hole and said click recess are aligned;

at least one click ball accommodated in said ball accommodation hole to be movable therein in said radial direction; and

at least one spring accommodated in said ball accommodation hole for biasing said click ball toward a direction to engage said click recess.

2. The extendable pivot shaft mechanism according to claim 1 , wherein one end of said rotatable shaft element is fixed to a pivot support member installed in said one of said grip and said camera body, another end of said rotatable shaft element comprises a radial projection, and

wherein said middle cylinder is sandwiched between said radial projection and said pivot support member in a direction of said rotational axis to be prevented from moving in said rotational axis direction relative to said pivot support member.

3. The extendable pivot shaft mechanism according to claim 2 , wherein said radial projection is integral with said rotatable shaft element.

4. The extendable pivot shaft mechanism according to claim 3 , wherein said radial projection is formed as an outer flange formed integral with said rotatable shaft element.

5. The extendable pivot shaft mechanism according to claim 2 , wherein said radial projection is provided as a radial member independent of said rotatable shaft element, said radial member being fixed to said rotatable shaft element during an assembling operation of said extendable pivot shaft mechanism.

6. The extendable pivot shaft mechanism according to claim 5 , wherein said radial projection is formed as a ring member.

7. The extendable pivot shaft mechanism according to claim 2 , wherein said linearly movable shaft element comprises at least one linear guide groove formed on a peripheral surface of said linearly movable shaft element which faces said middle cylinder to extend parallel to said rotational axis, and

wherein said middle cylinder includes at least one radial projection which is slidably engaged in said linear guide groove.

8. The extendable pivot shaft mechanism according to claim 1 , further comprising a click-stop mechanism, provided between said middle cylinder and said rotatable shaft element, for stopping said rotatable shaft element rotating about said rotational axis relative to said middle cylinder with a click action when said middle cylinder and said rotatable shaft element relatively rotate about said rotational axis.

9. The extendable pivot shaft mechanism according to claim 1 , wherein said outer cylinder serves as said linearly movable shaft element:

wherein said extendable pivot shaft mechanism includes an external cylindrical cover which is positioned around an outer peripheral surface of said outer cylinder to cover said outer opening of said ball accommodation hole, and

wherein one end of said spring accommodated in said ball accommodation hole is in contact with an inner peripheral surface of said external cylindrical cover, and the other end of said spring is in contact with said click ball.

10. The extendable pivot shaft mechanism according to claim 1 , wherein said inner shaft and said outer cylinder are fixed to said grip and said camera body, respectively.

11. The extendable pivot shaft mechanism according to claim 1 , wherein said rotatable shaft element is fixed to said grip, and

wherein said linearly movable shaft element is fixed to said camera body.

12. The extendable pivot shaft mechanism according to claim 1 , further comprising a grip-angle holding device installed between said rotatable shaft element and said middle cylinder to apply a frictional resistance to said rotatable shaft element and said middle cylinder therebetween in a rotational direction.

13. The extendable pivot shaft mechanism according to claim 12 , wherein said grip-angle holding device comprises a leaf spring.

14. The extendable pivot shaft mechanism according to claim 1 , wherein said inner shaft is formed as a cylindrical member having a through-hole which extends in a direction of said rotational axis, at least one electrical connecting element, for electrically connecting said grip and said camera body with each other, extending between said grip and said camera body via said through-hole.

15. The extendable pivot shaft mechanism according to claim 14 , wherein said electrical connecting element comprises a bundle of lead wires.

16. The extendable pivot shaft mechanism according to claim 1 , wherein said rotational axis extends in a direction orthogonal to an optical axis of a photographing optical system of said camera which is provided in said camera body.

17. The extendable pivot shaft mechanism according to claim 1 , wherein said rotatable grip comprises a shutter release button.