Tennis racquet with replaceable playing surface

1. A tennis racquet with a replaceable playing surface, comprising:

a frame having a handle and an oval head attached to the handle,

wherein the frame defines at least one key-aperture,

wherein the oval head includes a lower half-oval frame-portion that defines a cartridge support groove,

wherein the oval head includes an upper half-oval frame-portion that defines a front upper half-oval bridge and a back upper half-oval bridge,

wherein the front upper half-oval bridge includes a front head-guard,

wherein the back upper half-oval bridge includes a back head-guard, and

wherein the front bridge with its head-guard and the back bridge with its head-guard define a planar passage way;

a cartridge having a rim threaded with string,

wherein the string defines a playing surface, and

wherein the cartridge is adapted for insertion into, and for removal from, the planar passage way; and

a cartridge-lock, including at least one key, wherein the at least one key is shaped for entry into the at least one key-aperture to lock the cartridge into the frame;

such that a cartridge within the frame may be removed from the frame and replaced by a replacement cartridge without the use of tools.

2. A tennis racquet according to claim 1 ,

wherein the cartridge-lock is a mid-frame cartridge-lock, each key-aperture is a mid-frame key-aperture, and each key is adapted to pass through a key-aperture of the cartridge and a corresponding key-aperture of the frame.

3. A tennis racquet according to claim 1 , wherein a lower portion of the cartridge rim includes a tongue defining at least one cartridge key-aperture.

4. A tennis racquet according to claim 3 , wherein the lower half-oval cartridge support groove includes a deep groove portion adapted to accept the tongue.

5. A tennis racquet according to claim 4 ,

wherein the tongue defines a plurality of cartridge key-apertures,

wherein the lower half-oval frame-portion defines a corresponding plurality of mid-frame key-apertures, and

wherein the cartridge-lock includes a rail, a first end of the rail is attached to the frame, and a second end of the rail defines a stop.

6. A tennis racquet according to claim 5 , wherein the tongue defines a rail-clearance slot.

7. A tennis racquet according to claim 6 ,

wherein the cartridge-lock further includes a key-assembly comprising a key-mount and an attached plurality of keys;

wherein the key-assembly is mounted to the rail for sliding movement to and fro along the rail;

wherein the cartridge-lock further includes a compression spring located on the rail between the key-mount and the stop, and

wherein each key of the key-assembly corresponds to one associated cartridge key-aperture and one associated mid-frame key-aperture.

8. A tennis racquet according to claim 7 , wherein the cartridge is shaped for snug fit with the planar passageway and the lower half-oval cartridge support groove when cartridge is inserted into the planar passageway.

9. A tennis racquet according to claim 8 , further comprising an upper pull-plate and a lower pull-plate, each pull-plate having an outer gripping surface.

10. A tennis racquet according to claim 8 , further comprising a pull-cap having an outer gripping surface.

11. A tennis racquet according to claim 1 , wherein the cartridge-lock comprises a head-guard lock and a head-guard key.

12. A tennis racquet according to claim 11 , wherein the head-guard key includes a key-release pull-tab.

13. A tennis racquet according to claim 12 , wherein the head-guard key is an elongated, substantially planar strip.

14. A tennis racquet according to claim 13 , wherein the head-guard key is further shaped to have first and second enlarged edges to fit within first and second shaped-grooves of front and back head-guards respectively.