Pressure switch

• US 5,519,179 A
• Filed: 12/20/1994
• Issued: 05/21/1996
• Est. Priority Date: 01/20/1994
• Status: Expired due to Term

• Current Assignee: Yazaki Corporation
• Original Assignee: Yazaki Corporation
• Inventors: Sato, Kenichi
• Primary Examiner(s): Tolin, Gerald P.
• Application Number:
  US08/359,428
• Time in Patent Office: 518 Days
• Field of Search: 92/98 R, 340/611, 340/626, 307/118, 73/717, 73/723, 200/83 R, 200/83 A, 200/83 J, 200/83 N, 200/83 W, 200/51 R, 200/306
• US Class Current: 200/83.00N
• CPC Class Codes: H01H 35/24 Switches operated by change of fluid pressure, by fluid pressure waves, or by change of fluid flow wherein the change of pressure is caused by change of temperature H01H37/36

Abstract

This invention provides a pressure switch and a method of manufacture thereof, which allow the air vent hole to be formed very small in diameter so that the engine oil can be reliably prevented from flowing out through this air vent hole.

The reduced diameter portion of the air vent hole 13 is formed in the following steps during the process of resin-molding the insulating cap 3 of the pressure switch 1. After the air vent hole 13 having the outwardly projecting portion 14 is formed, the recessed portion 16 of the jig 17 is placed in contact with the circumferential surface of the projecting portion 14 of the air vent hole 13. The jig 17 is pressed against the projecting portion 14 of the air vent hole 13 with a specified pressure to deform the projecting portion 14 and thereby reduce the inner diameter of the air vent hole 13 at the end.

Claims

1. A pressure switch comprising:

an electrically conductive body;

an insulating cap;

a diaphragm clamped between the electrically conductive body and the insulating cap to form an open air chamber between the insulating cap and the diaphragm and a pressure chamber between the electrically conductive body and the diaphragm;

a stationary contact provided on the electrically conductive body adjacent one side of said diaphragm;

a movable contact provided on the diaphragm on the side thereof adjacent said stationary contact, the movable contact coming into or out of contact with the stationary contact when a pressure in the pressure chamber reaches a predetermined value, thus detecting the pressure;

an air vent hole formed in a wall of the insulating cap to communicate the open air chamber with the exterior of the switch; and

an outwardly projecting portion formed at an outer end of the air vent hole;

said air vent hole within said projecting portion having a cross sectional flow area which is locally reduced to a diameter that limits the passage of pressurized oil but not the passage of air, wherein said air vent hold through said wall of said insulating cap has a substantially constant diameter length which extends axially into said outwardly projecting portion, and said air vent hole in said outwardly projecting portion contains a radial constriction smaller than said diameter defining said locally reduced diameter.

2. A pressure switch according to claim 1, wherein the locally reduced cross-sectional portion of the air vent hole has an inner diameter of less than 0.8 mm.