Pressure and flow-regulating valve for automatic or semiautomatic-cycle lubricating system

Claim 1

A pressure and flow regulating valve for use as part of an automatic or semiautomatic cycle lubricating system of motor vehicles, machine tools and machines in general by insertion in a path which conveys lubricating oil from a pump to oil dispensing valves in the lubricating system and which is adapted to communicate, directly via an extension conduit means, with oil contained in a feed tank for the pump, the valve comprising, in combination a valve body provided with an axial bore extending therethrough, having an inlet, an upstream section, an intermediate section, a downstream section and an outlet defining a drain; an insert element positioned in said upstream section of said bore and having an axial aperture therein; a first coil spring in said upstream section of said bore and having one end thereof positioned on an upstream surface of said insert element; a ball biased by said first coil spring to close and inlet for preventing return of oil coming from the pump; an oil flow regulating piston having a piston rod with an end carrying a spherical cap and a longitudinally extending section having a cross-section, whose area is smaller than said intermediate section of said axial bore slidably inserted in said intermediate section of said bore for allowing oil to flow in spaces about the periphery of said longitudinally extending section of said piston; a feeding chamber downstream of said longitudinally extending section of said oil flow regulating piston and defined by at least a portion of said downstream section of said bore for receiving oil flowing in the space about said extending section; two openings through said body, one of them for attachment of a maximum pressure regulating device which is to allow excess feed oil in every cycle to flow into the tank, the other one for attachment of conduit means which is to convey oil from the feeding chamber into the dispensing valves; a second coil spring positioned in said feeding chamber around said piston rod with one of its ends positioned against an annular downstream surface of said piston for biasing said piston towards an annular downstream surface of said insert element so as to obstruct oil flow, said second coil spring extending downstream and having a diameter smaller than that of said longitudinally extending section of said piston, an axially adjustable plug positioned in said downstream section of said bore, said second coil spring having its second end resting against a truncated-conical narrowing downstream passage of a cylindrical chamber and formed in an upstream face of said axially adjustable plug so as to create a closure seat for an axial bore which extends through said plug, and seat being positioned to receive said spherical cap on said end of said piston rod so as to permit oil to discharge into the tank via said axial bore in said plug; whereby the axial bore in said plug is of reduced diameter by virtue of the truncated-conical narrowing passage so as to permit gradual starting up of the pump at the beginning of each feed cycle, to get desired pressure in the feed conduit means to the dispensing valves and further, during each feed stop stroke of the pump, to allow slow drain of oil from the conduit means to the dispensing valves until a zeroing of oil pressure in the conduit means to the dispensing valves is attained, while keeping these conduit means full of oil in order to avoid the presence of air bubbles therein so as to make complete filling of the dispensing valves possible in the following cycle.