Advanced proof-of-rotation switch
US5222888A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 21, 1991 |
| Grant date | Jun 29, 1993 |
| Priority date | — |
| Expiry date | Aug 21, 2011 |
Classification
- Technology area (CPC F)Mechanical Engineering; Lighting; Heating
- CPC primaryF23N2235/14
- WIPO fieldThermal processes and apparatus
- WIPO sectorMechanical engineering
Abstract
A HVAC system (10) employs a gas valve (20) to supply gas for combustion within a heating portion (12) of the system. An exhaust (22) removes combustion products using a motor (28) driven exhaust fan (24). An apparatus (34) controls combustion and uses a sensor (36) for sensing the rotational speed of a motor shaft (26). A switch (T1) is responsive to sensed motor speed to open and close the valve, the valve being opened only if the motor is operating within a predetermined speed range. A first speed discriminator (48A) enables of the switch to open the valve when the motor speed exceeds a first predetermined value. A second speed discriminator (48B) disables the switch to close the valve when motor speed exceeds a second and higher predetermined speed which is indicative of a blocked exhaust, or a fan blade is loose. This latter action insures that a build-up of potentially dangerous exhaust gases cannot occur.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.