This invention relates generally to a pumping or liquid flow system, and more particularly to such a system including at least one heat generating control component for a motor-pump unit and apparatus for cooling the control component, and to apparatus for sensing the pressure of the liquid.
Pumping systems including electric motor-pump units are well known and in common use. Examples include residential water supply systems and gasoline dispensing systems in service stations. A typical water supply system includes a motor-pump unit in a well, a water pipe connected to the unit and extending out of the well to a pressure tank, and a control that senses the water pressure in the tank and controls the unit to maintain the pressure in a selected pressure range.
Traditionally mechanical pressure gauges are used to monitor the flow pressure through such a system. Normally these pressure gauges are mounted on flow pipes whose pressures are to be monitored, using pipe stands or stubs. One popular method of mounting is to provide a bored hole in the pipe, the hole is then threaded, and then a small pipe stand or stub having male threads at one end and a pressure gauge on the opposite end is screwed into the hole. Flow pressure is transmitted to the pressure gauge through the pipe stub to the pressure gauge.
There are numerous commercially available pressure sensors for use with pipe stubs. Most of these pressure sensors incorporate a chamber having a diaphragm with an inlet on one side of the diaphragm and an outlet on the other side of the diaphragm. The pressure sensing inlet normally has female threads for receiving male threads of the pipe stub and a narrow passage filled with a liquid, such as oil, is on the other side of the diaphragm. Water pressure in the pipe causes movement of the diaphragm which, in turn, moves the liquid in the stub on the other side of the diaphragm. Movement of this liquid in the narrow passage causes movement of an indicator to monitor pressure in the pipe.
In the foregoing arrangement the small measuring passage located above the diaphragm often must be filled with oil. This presents a manufacturing problem because such a narrow passage is very difficult to fill with oil or any other liquid without leaving an air bubble therein. In order to properly fill such a gauge with the liquid needed for its functioning, it is therefore necessary first to apply a vacuum to the passage. It is an advantage of this invention that a pressure sensing mechanism is provided for a motor-pump system which can be easily mounted and filled but yet does not require the use of a filling oil and the need for pulling a vacuum.
Some pressure sensor installations require on-site opening of a pipe wall on which the pressure gauge is installed. For example, some require holes in the walls of the pipes and some require protrusions in the walls of the pipes. Such operations are expensive and difficult to incorporate. Another advantage of this invention is that a pressure sensing mechanism is provided which when installed becomes in-line with the pipe line and is relatively inexpensive to manufacture and install.
One prior art device for pipe pressure sensing comprises a part that defines a hollow chamber which is fastened onto a pipe to clamp a diaphragm between the pipe and a portion of the chamber unit surrounding a pressure inlet opening into the chamber. The diaphragm has a round, sensing protrusion with a sensing tip on an outer end thereof, which extends outwardly from one side of the diaphragm and extends through a round hole in the pipe so as to communicate the pressure in the pipe to the chamber. Although this design presents some improvement over the others, it also utilizes a mechanical interface among liquid, diaphragm, and liquid again to convey the pressure in the pipe to the gauge. It is another advantage of the present invention that it includes a mechanical-electrical transducer which more accurately measures the pressure in a motor-pump system.
Various types of pipe pressure sensors can only be used with specific types of pipe, but it is an advantage of this invention that a pipe pressure sensor is provided which can be used with various types of pipe including both plastic and metal pipes.
Control units for pump-motor units including electronics are typically cooled by air cooling through a metallic radiating panel used as a heat sink or a cooling plate. Various types of stock heat sinks are commercially available. Due to the low convective ability of air cooling, the size of such heat dissipating devices is relatively large compared with the overall size of the control package itself. The broad concept of cooling electrical devices by means of a flowing medium was introduced some time ago. In one particular design a closed recirculation cooling system was developed to cool electrodes at different electrical potentials. An advantage of the present invention is that the size of packaging is reduced by using a liquid cooling medium in lieu of the well known air cooling method.
In another prior art design, a printed circuit board package for high density packaging includes electronic circuit components cooled by a liquid cooled cold plate or heat sink. A circulating coolant is also included. A compliant interface including a heat conductive and electrically insulative paste between the cold plate and the circuit components is provided. The paste, which flows like a highly viscous liquid, is used in conjunction with a deformable thin film to compensate for any variations or irregularities so as to conform with the surfaces of the individual circuit packages. An objective of the present invention is to utilize a flow medium of the motor-pump system as a coolant to remove the heat generated by the electrical components, by incorporating a heat sink in the motor-pump system that is cooled directly by the liquid medium in the system, and to avoid the use of any deformable fill or heat conductive paste for mounting the electrical components.
It is a further general object of the present invention to provide a compact system including a pressure sensor and a heat sink in one integral module, thus making the module easy to install in a motor-pump system using only ordinary plumbing tools.