Metal injection molding for stethoscope chestpiece

1. A stethoscope chestpiece comprising:

a body member having a bottom surface;

an ejector mark disposed on the bottom surface;

wherein the stethoscope chestpiece has a weight of at least 50 g, and a surface roughness (R a ) no greater than 1.6 microns in an unpolished state and reflectivity (% R) of at least 60% in an unpolished state,

wherein the stethoscope chestpiece has been produced by

injection molding, extruding, or pressing a metallic thermoplastic composition into a mould forming a green molded body,

debinding a portion of binder material from green molded body to form a brown molded body without reducing the temperature by more than 80° C.;

sintering the brown molded body to form the stethoscope chestpiece.

2. The stethoscope chestpiece of claim 1 , wherein the ejector mark is recessed and comprises a side wall and at least one major surface contacting the side wall.

3. The stethoscope chestpiece of claim 1 , wherein the stethoscope chestpiece is non-symmetrical.

4. The stethoscope chestpiece of claim 1 , wherein the stethoscope chestpiece has a thick portion and a thin portion.

5. The stethoscope chestpiece of claim 1 , wherein the stethoscope chestpiece is further polished to a reflective finish.

6. The stethoscope chestpiece of claim 5 , wherein the stethoscope chestpiece comprises a thin metallic film deposited by physical vapor deposition.

7. The stethoscope chestpiece of claim 1 , wherein the metallic thermoplastic composition has a melt flow index of at least 800 g/ 10 mins as measured using ISO 1133 (190 deg. C., 21.6 kg).

8. The stethoscope chestpiece of claim 1 wherein the body member having a first generally bell-shaped recess with an inner central portion, an outer rim portion and a bore extending through the body member communicating with the central portion of the first recess;

further comprising immobilizing means situated on the body member and located within the first recess at about the central portion, the immobilizing means adapted to be contacted by a diaphragm when the diaphragm is in an inner position so that the stethoscope chestpiece will pass low frequency sounds and attenuate high frequency sounds when the diaphragm is in the outer position and between the outer and inner positions, and when the diaphragm is in the inner position an acoustical stiffness of the diaphragm will be sufficiently higher than the first acoustical stiffness so that the stethoscope chestpiece will pass high frequency sounds and attenuate low frequency sounds.

9. The stethoscope chestpiece of claim 8 , further comprising a second conical-shaped recess located within the first bell-shaped recess and emanating from a base of the first bell-shaped recess, the second recess being formed by the immobilizing means and the central portion of the body member.

10. The stethoscope chestpiece of claim 8 , wherein the ejector mark is disposed within the first generally bell-shaped recess.

11. A stethoscope comprising:

the stethoscope chestpiece of claim 1 ;

a diaphragm releasably attached to the stethoscope chestpiece.

12. The stethoscope of claim 11 , further comprising:

a headset comprising removable ear tips;

tubing, wherein the ear tips are fluidically coupled to the stethoscope chestpiece through the tubing.

13. A method of making a metal stethoscope comprising:

injection molding, extruding, or pressing a metallic thermoplastic composition into a mould forming a green molded body,

continuously debinding a portion of binder material from green molded body at a temperature in a range of 100 to 200° C. over a period from 4 to 12 hours in a nitrogen-comprising atmosphere forming a brown molded body, wherein the temperature is maintained within ±10° C. during the period;

sintering the brown molded body at a temperature in a range from 1100 to 1500° C. over a period of from 6 to 10 hours in a hydrogen or argon atmosphere to form the stethoscope chestpiece.

14. The method of claim 13 , further comprising: removing the green molded body from the mould by applying ejector pins and forming an ejector mark in the green molded body.

15. The method of claim 13 , wherein the mould comprises a negative forming:

a body member having a first generally bell-shaped recess with an inner central portion, an outer rim portion and a bore extending through the body member communicating with the central portion of the first recess;

immobilizing means situated on the body member and located within the first ecess at about the central portion, the immobilizing means adapted to be contacted by a diaphragm when the diaphragm is in an inner position so that a stethoscope chestpiece will pass low frequency sounds and attenuate high frequency sounds when the diaphragm is in the outer position and between the outer and inner positions, and when the diaphragm is in the inner position the acoustical stiffness of the diaphragm will be sufficiently higher than the first acoustical stiffness so that the stethoscope chestpiece will pass high frequency sounds and attenuate low frequency sounds.

16. The method of claim 15 , wherein the ejector mark is formed proximate to the immobilizing means.

17. The method of claim 13 , wherein the metallic thermoplastic composition is Catamold LG+.

18. The method of claim 13 , wherein the sintering and debinding occur in the same continuous process.

19. The method of claim 13 , further comprising polishing a stethoscope chestpiece to a reflective finish.

20. The method of claim 19 , further comprising depositing a thin metallic film onto one or more surfaces using physical vapor deposition.