Apparatus for converting motion

1. An assembly for converting motion, the assembly moveable between a retracted position and an extended position, the assembly comprising:

a first arm rotatable at a first position thereon about a first fixed pivot;

a second arm rotatable at a first position thereon about a second fixed pivot, the second fixed pivot spaced apart from the first fixed pivot, the first and second fixed pivots being joined by a line;

a third arm pivotably connected at a first position thereon to the second arm at a second position on the second arm, the second position spaced apart from the first position on the second arm;

wherein the third arm has a point thereon, the said point on the third arm moving in a substantially straight line extending perpendicular to the line joining the first and second fixed pivots;

a first connecting arm extending between the first arm and the third arm, the first connecting arm pivotably connected to a second position on the first arm spaced apart from the first position on the first arm and pivotably connected to the third arm at a second position thereon spaced apart from the first position thereon; and

a second connecting arm extending between the first arm and the second arm, the second connecting arm pivotably connected to a position on the first arm disposed between the first and second positions thereon and pivotably connected to the second position on the second arm or a third position on the second arm spaced apart from the first position and the second position on the second arm;

wherein in the extended position a pair of crossing arms is formed by a first crossing arm selected from the first arm, the second arm, the third arm, the first connecting arm and the second connecting arm and a second crossing arm selected from the first arm, the second arm, the third arm, the first connecting arm and the second connecting arm;

the assembly further comprising a locking assembly comprising a first locking member and a second locking member, the first locking member connected to the first crossing arm, the second locking member connected to the second crossing arm, the first locking member engaging with the second locking member to lock the first crossing arm to the second crossing arm in the position of the first and second crossing arms that cross one another to triangulate the assembly at a position from the retracted position to the extended position such that movement of the assembly beyond said position from the retracted position to the extended position in a direction of extension is prevented.

2. The assembly according to claim 1 , wherein a length of the first arm or the second arm is no greater than a distance between the first and second fixed pivots.

3. The assembly according to claim 1 , wherein the lengths of the first, second and third arms are substantially the same.

4. The assembly according to claim 1 , wherein the second connecting arm is connected to the second position on the second arm, such that the second connecting arm is connected to both the second and third arms.

5. The assembly according to claim 1 , further comprising a fourth arm pivotably connected at a first position thereon to the first arm at a fifth position on the first arm.

6. The assembly according to claim 5 , wherein the length of the fourth arm is the same as the length of the third arm.

7. The assembly according to claim 1 , wherein the locking assembly locks one arm of the assembly to another arm of the assembly.

8. The assembly according to claim 7 , wherein the locking assembly locks together each of a pair of arms that are crossed in the extended position.

9. The assembly according to claim 1 , further comprising a locking arm, wherein the locking arm is pivotably connected to an arm of the assembly.

10. The assembly according to claim 9 , further comprising a support arm, the support arm being pivotably connected to the locking arm.

11. The assembly according to claim 1 , further comprising a guide assembly, the guide assembly comprising a guide member and an engagement member moveably engageable with the guide member, wherein the engagement member is connected to an arm of the assembly.

12. The assembly according to claim 11 , wherein the engagement member comprises the first locking member.

13. The assembly according to claim 11 , wherein the guide member is connected to an arm of the assembly other than the arm bearing the engagement member.

14. An assembly for converting motion, the assembly moveable between a retracted position and an extended position, the assembly comprising:

a first arm rotatable at a first position thereon about a first fixed pivot;

a second arm rotatable at a first position thereon about a second fixed pivot, the second fixed pivot spaced apart from the first fixed pivot, the first and second fixed pivots being joined by a line;

a third arm pivotably connected at a first position thereon to the second arm at a second position on the second arm, the second position spaced apart from the first position on the second arm; wherein the third arm has a point thereon, the said point on the third arm moving in a substantially straight line extending perpendicular to the line joining the first and second fixed pivots;

a first connecting arm extending between the first arm and the third arm, the first connecting arm pivotably connected to a second position on the first arm spaced apart from the first position on the first arm and pivotably connected to the third arm at a second position thereon spaced apart from the first position thereon; and

a second connecting arm extending between the first arm and the second arm, the second connecting arm pivotably connected to a third position on the first arm disposed between the first and second positions thereon and pivotably connected to the second position on the second arm or a third position on the second arm spaced apart from the first position and the second position on the second arm;

the assembly further comprising a locking assembly comprising a first locking member and a second locking member, the first locking member connected to one of the first, second or third arms or one of the first or second connecting arms at a position other than a pivotable connection point between respective arms and/or connecting arms, and engaging with the second locking member at a position from the retracted position to the extended position such that movement of the assembly beyond said position from the retracted position to the extended position in a direction of extension is prevented.