Apparatus for indicating pressure

1. An apparatus for indicating pressure of melt conveyed through a passage of injection molding equipment in excess of a predetermined limit comprising a fitting having a fitting body with a fitting bore therethrough, the fitting body being installed in the equipment with the fitting bore open to the interior of the passage, an indicating member received within the fitting bore and being bonded thereto, the indicating member being maintained in a normal position by the bond and being displaced therefrom by force from melt applied to the indicating member sufficient to cause the bond to fail, the indicating member being displaced to an indicating position determined by abutting contact of a surface of the indicating member with an opposing surface of the fitting body, a portion of a stem of the indicating member being exposed with the indicating member in the indicating position.

2. The apparatus according to claim 1 wherein the indicating member comprises a piston end having an exposed face proximate the end of the fitting bore open to the passage and the fitting bore defines an annular gap between the piston end and the fitting body, the indicating member being bonded to the fitting body by a bond spanning the annular gap.

3. The apparatus according to claim 2 wherein the indicating member and fitting body are metal and the indicating member is bonded to the fitting body by brazing.

4. The apparatus according to claim 3 wherein the indicating member and the fitting body are steel and the braze is a nickel alloy.

5. The apparatus according to claim 2 wherein the abutting contact of the indicating member and sealing body seals the fitting bore to prevent melt bypassing the piston end from passing out of the fitting body.

6. The apparatus according to claim 5 wherein the indicating member comprises a taper between the piston end and the stem and the fitting bore comprises a transition and the taper makes abutting contact with the transition.

7. The apparatus according to claim 5 wherein the indicating member comprises a stepped reduction from the piston end to the stem and the stepped reduction makes abutting contact with a stepped recess of the fitting bore.

8. The apparatus according to claim 2 further comprising a sealing member for forming a seal between the indicating member and the fitting body to prevent melt bypassing the piston end from passing out of the fitting body.

9. The apparatus according to claim 2 wherein the area of the exposed face is selected so that melt pressure acting thereon in excess of a predetermined value produces a force sufficient to cause failure of the bond and after failure of the bond, normal melt pressure acting thereon produces a force sufficient to displace the indicating member to the indicating position.

10. The apparatus according to claim 1 wherein the indicating member is retained in the indicating position by a press fit between the indicating member and the fitting body.

11. An Injection molding manifold comprising a passage for conveying melt from an injection unit to mold cavities, a pressure indicating fitting received in a manifold bore, the fitting comprising a fitting body with a fitting bore therethrough, the fitting body being installed in the manifold with the fitting bore open to the interior of the passage, an indicating member received within the fitting bore and being bonded thereto, the indicating member being maintained in a normal position by the bond and being displaced therefrom by force from melt applied to the indicating member sufficient to cause the bond to fail, the indicating member being displaced to an indicating position determined by abutting contact of a surface of the indicating member with an opposing surface of the fitting body, a portion of a stem of the indicating member being exposed with the indicating member in the indicating position.

12. The manifold according to claim 11 wherein the indicating member comprises a piston end having an exposed face proximate the end of the fitting bore open to the passage and the fitting bore defines an annular gap between the piston end and the fitting body, the indicating member being bonded to the fitting body by a bond spanning the annular gap.

13. The manifold according to claim 12 wherein the indicating member and fitting body are metal and the indicating member is bonded to the fitting body by brazing.

14. The manifold according to claim 12 wherein the abutting contact of the indicating member and sealing body seals the fitting bore to prevent melt bypassing the piston end from passing out of the fitting body.

15. The manifold according to claim 14 wherein the indicating member comprises a taper between the piston end and the stem and the fitting bore comprises a transition and the taper makes abutting contact with the transition.

16. The manifold according to claim 14 wherein the indicating member comprises a stepped reduction from the piston end to the stem and the stepped reduction makes abutting contact with a stepped recess of the fitting bore.

17. The manifold according to claim 12 further comprising a sealing member for forming a seal between the indicating member and the fitting body to prevent melt bypassing the piston end from passing out of the fitting body.

18. The manifold according to claim 12 wherein the area of the exposed face is selected so that melt pressure acting thereon in excess of a predetermined value produces a force sufficient to cause failure of the bond and after failure of the bond, normal melt pressure acting thereon produces a force sufficient to displace the indicating member to the indicating position.

19. The manifold according to claim 11 wherein the indicating member is retained in the indicating position by a press fit between the indicating member and the fitting body.