Liquid flow meter construction

#This invention relates in general to the construction of devices for controlling the flow of fluids and, in particular, to a new and useful device for continuously measuring the rate of flow of a liquid flowing from a supply tank to a consuming device.

#With the increasing scarcity of mineral oil products and the high prices therefor, it becomes necessary to effect the exact monitoring of the fuel consumption in consuming devices, such as motor vehicles, heating devices and similar operating devices in order to effect an economy of consumption and the elimination of waste. For this purpose, flow meters are needed which indicate the rate of flow accurately even at very low consumption rates and which are responsive to small differences in hydraulic pressure between the inlet and outlet of such devices. The standard values to be assumed for the required measuring performance may be a rate of flow of approximately 1 liter per hour with a response pressure of about 30 cm water column, and an accuracy of measurement of at least .+-. 2%. Numerous types of flow meters are known which are based on various principles. They do not, however, comply with the requirements as to minimum pressure of response, accuracy of measurement and measurable minimum rate of flow mentioned above.

#The present invention provides a flow meter having satisfactory operating characteristics, and it includes a housing having a measuring chamber in which is movable a measuring piston. The measuring piston influences the position of a reversing control member for regulating the flow through the device and which advantageously includes means for counting the piston strokes.

#In the drawings:

#FIG. 1 is a longitudinal sectional view of a liquid flow meter constructed in accordance with the invention;

#FIG. 2 is a view similar to FIG. 1 but at a right angle to the section shown therein; and

#Referring to the drawings in particular, the invention embodied therein in FIGS. 1 and 2, comprises a flow meter which has a housing 2 forming a cylinder with a piston chamber having a measuring piston 1 slidable therein. The stroke of the piston may be controlled by an adjusting device 4. During movement of piston 1 toward each end position, it engages with a compressible coil spring 3 to pretension this coil spring and, thereafter, it engages against a stop 40. Housing 2 also includes a cylindrical portion 5 defining a control chamber in which a control slider 6 is movable. Slider 6 is provided with annular grooves so as to define control surfaces which face in respective opposite directions and which may be acted upon by the fluid which is brought in through an inlet 10 to the housing and circulated through the housing between the measuring chamber and the control chamber and flow passage control means to an outlet 25. A permanent magnet 7 is associated with each end of the control slider and it cooperates with a ferromagnetic armature plate 8 to retain the slider in each end position of its movement until a fluid pressure force acting on the control surfaces overcomes this retention force and moves it rapidly in an opposite direction. The housing portion 5 includes a tubular part 5a which accommodates a guard tube contact 9 which may be actuated during the movement of the control slider to the various reverse operating positions in order to provide a counting or other control signal associated with operating the device.

#A liquid to be measured, such as gasoline, oil or a similar material, flows from a pump, which has not been shown, through the inlet connection 10 into a bore 11 defined in the housing and, therefrom, it flows through passageways or annular grooves 12, 13 and 14 into a bore 15, as seen in FIG. 2, from where it passes through the channel 16 into the righthand chamber portion 22 of measuring cylinder 2. In consequence, piston 1 is driven to the lefthand side. The bores and passageways 11, 15, 21 and 18 are offset relative to each other by about 90.degree.. During the motion of piston 1 to the left side, the liquid to be measured flows from the left cylinder chamber 23 through passages 34, 18, 19, 33, 20 and 21, to the outlet 25. All of these passages and control grooves define flow control passage means in the housing.

#At the end of the travel of the measuring piston to the lefthand side, it will engage the left spring 3 and tension the spring and compress it until it abuts against the stop 40. This causes a back pressure in chamber 22 which increases, at first gradually, and then suddenly. The back pressure becomes effective also in channel 17 where it acts on the left end face of the control slider 6 in a direction opposite to the retaining force which is effective between the left magnet 7 and the associated armature plate 8. As soon as the back pressure exceeds the retaining force of the magnet 7, slider 6 is torn loose and moved in the direction of its opposite end position. During this travel, the control slider 6 shuts off the communication between groove 13 and channel 14, on the one hand, and outlet passages 33, 20, on the other hand.