Brake fluid level sensing system

Claim 2

A hydraulic brake fluid level sensing system for use with a hydraulic vehicle brake system having a brake fluid reservoir, said system comprising: a cover member for enclosing the reservoir; a diaphragm positioned between the cover member and the fluid reservoir, the diaphragm and the cover member forming a chamber therebetween; means for venting the chamber to the atmosphere; and fluid level sensor means responsive to fluid level variations in the reservoir, said fluid level sensor means including a stationary guide means extending from the chamber to the reservoir through the diaphragm, the diaphragm normally sealingly engaging the periphery of the stationary guide means and sealingly engaging the reservoir to normally seal the reservoir from the chamber, the diaphragm being moved down the stationary guide means by differential pressure thereacross resulting from a decrease in brake fluid level in the reservoir, the stationary guide means having a slot therein proximate the end thereof in the reservoir, whereby movement of the diaphragm down the stationary guide by the differential pressure thereacross resulting from loss of brake fluid is limited by venting of the reservoir to atmosphere when the diaphragm is moved to a position over the slot in the stationary guide means.

Claim 3

A hydraulic brake fluid level sensing system for use with a hydraulic vehicle brake system having a brake fluid reservoir, said system comprising: a cover member for enclosing the reservoir; a diaphragm positioned between the cover member and the fluid reservoir, the diaphragm and the cover member forming a chamber therebetween; means for venting the chamber to the atmosphere; a switch housing within the chamber, the switch housing being secured to the cover member; a rod guide secured to the switch housing and having a stem portion extending vertically downward through the diaphragm and into the reservoir, the diaphragm normally sealingly engaging the periphery of the stem portion and sealingly engaging the reservoir to normally seal the reservoir from the chamber, the diaphragm being moved down the stem by differential pressure thereacross resulting from a decrease in brake fluid level in the reservoir, the rod guide having a bore extending therethrough between the switch housing and the reservoir and the stem portion having a slot therein proximate the end thereof in the reservoir; a float rod vertically slidable through the bore in the rod guide; a float secured to the end of the float rod in the reservoir for vertical movement thereof in response to brake fluid level variations in the reservoir; and switch means in the switch housing, said switch means being operated by the upper end of the float rod when the level of brake fluid in the reservoir is below a specified level, whereby movement of the diaphragm down the stem portion by the differential pressure thereacross resulting from loss of brake fluid is limited by venting of the reservoir to atmosphere when the diaphragm is moved to a position over the slot in the stem portion.

Claim 4

A hydraulic brake fluid level sensing system for use with a hydraulic vehicle brake system having a brake fluid reservoir, said system comprising: a cover member for enclosing the reservoir; a diaphragm positioned between the cover member and the fluid reservoir, the diaphragm and the cover member forming a chamber therebetween; means for venting the chamber to the atmosphere; a switch housing within the chamber, the switch housing being secured to the cover member; a rod guide secured to the switch housing and having a stem portion extending vertically downward through the diaphragm and into the reservoir, the diaphragm normally sealingly engaging the periphery of the stem portion and sealingly engaging the reservoir to normally seal the reservoir from the chamber, the diaphragm being moved down the stem by differential pressure thereacross resulting from a decrease in brake fluid level in the reservoir, the rod guide having a bore extending therethrough between the switch housing and the reservoir and the stem portion having a slot therein proximate the end thereof in the reservoir; a float rod vertically slidable through the bore in the rod guide; a float secured to the end of the float rod in the reservoir for vertical movement thereof in response to brake fluid level variations in the reservoir; and switch means in the switch housing, said switch means being operated by the upper end of the float rod when the level of brake fluid in the reservoir is below a specified level, whereby movement of the diaphragm down the stem portion by the differential pressure thereacross resulting from loss of brake fluid is limited by venting of the reservoir to atmosphere when the diaphragm is moved to a position over the slot in the stem portion.