Electromechanical generator for converting mechanical vibrational energy into electrical energy

1. An electromechanical generator for converting mechanical vibrational energy into electrical energy, the electromechanical generator including a cantilever spring having a fixed end, a free end and a central portion therebetween, a mount for the cantilever spring to which the fixed end is fixed, a mass located at the free end of the cantilever spring, the mass including either a coil or at least one magnet defining a region of magnetic flux, wherein at least one of the fixed end and the free end of the cantilever spring is substantially stiffer than the central portion of the cantilever spring.

2. An electromechanical generator according to claim 1 wherein at least one of the fixed end and the free end of the cantilever spring is at least twice as stiff as the central portion of the cantilever spring.

3. An electromechanical generator according to claim 1 wherein both of the fixed end and the free end of the cantilever spring are at least twice as stiff as the central portion of the cantilever spring.

4. An electromechanical generator according to claim 1 wherein the increase in stiffness at the or each of the fixed end and the free end is achieved by modifying at least one of the cross-sectional shape and the cross-sectional dimensions of the cantilever spring.

5. An electromechanical generator according to claim 1 wherein the cantilever spring and the mount are integral, the integral mount thereby forming the fixed end of the cantilever spring.

6. An electromechanical generator according to claim 1 wherein the cantilever spring and at least a part of the mass are integral, the integral part of the mass thereby forming the free end of the cantilever spring.

7. An electromechanical generator according to claim 1 wherein at least one magnet is located at the free end of the cantilever spring, the at least one magnet defining a region of magnetic flux within a gap, and further comprising a coil received within the gap.

8. An electromechanical generator according to claim 7 wherein the mount comprises a frame of a housing for the electromechanical generator.

9. An electromechanical generator according to claim 8 wherein the frame defines a cavity within which the cantilever spring, the at least one magnet and the support member are located.

10. An electromechanical generator according to claim 9 further comprising a plate member to which the coil is fitted, and the plate member is fixed to the frame.

11. An electromechanical generator according to claim 9 further comprising a cover member fitted to the frame and covering the cavity.

12. An electromechanical generator according to claim 9 further comprising a base member fitted to the frame and covering the cavity.

13. An electromechanical generator according to claim 8 further comprising a support member for the at least one magnet at the free end of the cantilever spring, the support member being integral with the cantilever spring.

14. An electromechanical generator according to claim 13 further comprising a magnet holder for holding the at least one magnet, and wherein the magnet holder is fixed to the support member.

15. An electromechanical generator according to claim 14 wherein the magnet holder is fixed to the support member by a screw threaded connector, the screw threaded connector being adjustable thereby the vary the longitudinal position of the holder relative to the cantilever spring and thereby vary the resonant frequency of the electromechanical generator.

16. An electromechanical generator according to claim 15 wherein screw threaded connector comprises a first head part fitted to one of the holder and the support member and a second barrel part fitted to the other of the holder and the support member, the head part and the barrel part being threadably connected together.

17. An electromechanical generator according to claim 16 wherein the holder is mounted to the support member by at least one pin extending from one of the holder and the support member and slidably received in a hole in the other of the holder and the support member.

18. An electromechanical generator for converting mechanical vibrational energy into electrical energy, the electromechanical generator including a cantilever spring having a fixed end and a free end, a mount for the cantilever spring to which the fixed end is fixed, a mass located at the free end of the cantilever spring, the mass including either a coil or at least one magnet defining a region of magnetic flux, the mass further including a support member integral with or connected to the cantilever spring, a holder for holding either the coil or the at least one magnet, and a screw threaded connector which fixes the holder to the support member, the screw threaded connector being adjustable thereby to vary the longitudinal position of the holder relative to the cantilever spring and thereby vary the resonant frequency of the electromechanical generator.

19. An electromechanical generator according to claim 18 wherein screw threaded connector comprises a first head part fitted to one of the holder and the support member and a second barrel part fitted to the other of the holder and the support member, the head part and the barrel part being threadably connected together.

20. An electromechanical generator according to claim 19 wherein the holder is mounted to the support member by at least one pin extending from one of the holder and the support member and slidably received in a hole in the other of the holder and the support member.