Positive displacement pump for dispensing a metered quantity of liquid

Claim 2

A positive displacement pump for selectively dispensing a liquid, comprising: a cylinder having a reciprocating piston, a piston rod extending rearwardly from said piston, and sliding bearing means supporting said piston rod; a concentric cylinder resilient seal coupled between said piston and the cylinder wall so as to divide said cylinder into a forward chamber for containing a liquid to be dispensed, and a rearward chamber; means for allowing the liquid to exit from said forward chamber through an outlet port during the forward travel of said piston, and to enter said forward chamber through an inlet port during the return travel of said piston; inlet vent means for selectively admitting pressurized gas into said rearward chamber for driving said piston forward; control means operable when said piston reaches the forward limit of its travel for closing said inlet vent means; said sliding bearing means normally providing a seal with said piston rod, and said bearing means and piston rod cooperatively providing an outlet vent for exhausting driving gas from said rearward chamber when said piston closely approaches the forward limit of its travel; and drive means operable for returning said piston to its rearward position when the driving gas has been exhausted.

Claim 3

A pump as claimed in claim 1 wherein said control means is operable in response to a drop in liquid pressure at the forward end of said forward chamber which results from exhausting said driving gas from said rearward chamber through said outlet vent and releasing the liquid from said forward chamber through said outlet part.

Claim 4

A pump as in claim 1 wherein said sliding bearing means consists of an elongated cylindrical member extending rearward from the back side of said rear chamber and having a concentric center bore matching, in close fitting relationship, the piston rod outer diameter; said elongated member having an exhaust port extending radially from said center bore through said elongated member wall; said seal consisting of an O-ring seal acting between said elongated cylindrical member and said piston rod, and in sliding contact with said piston rod; said piston rod having a section of reduced diameter; and said outlet vent being provided through the cooperative action of said piston rod, bearing means, and seal, said rod reduced secTion simultaneously engaging said seal and said exhaust port as the piston closely approaches the forward limit of its travel.

Claim 5

A pump as in claim 3 wherein: said O-ring seal and said exhaust port are located at the piston rod entrance to the rear chamber thereby providing an exhaust path of minimum restriction.

Claim 6

A positive displacement pump for selectively dispensing a liquid, comprising: a cylinder having a reciprocating piston, a piston rod extending rearwardly from said piston, and sliding bearing means supporting said piston rod; a concentric cylinder resilient seal coupled between said piston and the cylinder wall which separates said cylinder into a forward chamber for containing a liguid to be dispensed, and a rear chamber; means for allowing said liquid to exit from said forward chamber through an outlet part during the forward travel of said piston and enter said forward chamber through an inlet part during the return travel of said piston; a source of pressurized gas for driving said piston forward; normally closed inlet vent means for admitting the pressurized gas from said source into said rear chamber; normally open outlet vent means for exhausting the pressurized gas from said rear chamber; manually actuable control means for selectively opening said inlet vent means and simultaneously closing said outlet vent means to drive the piston forward; separate control means operable when said piston reaches the forward limit of its travel for simultaneously closing said inlet vent means and opening said outlet vent means; said sliding bearing means normally providing a seal with said piston rod, and said bearing means and piston rod cooperatively providing an outlet vent for exhausting driving gas from said rear chamber only when said piston closely approaches the forward limit of its travel; and drive means operable for returning said piston to its rearward position when the driving gas has been exhausted.

Claim 7

A positive displacement pump for selectively dispensing a liquid, comprising: a cylinder having a reciprocating piston, a piston rod extending rearwardly from said piston, and sliding bearing means supporting said piston rod; a concentric cylinder resilient seal coupled between said piston and the cylinder wall which separates said cylinder into a forward chamber for containing a liguid to be dispensed, and a rear chamber; means for allowing said liquid to exit from said forward chamber through an outlet part during the forward travel of said piston and enter said forward chamber through an inlet part during the return travel of said piston; a source of pressurized gas for driving said piston forward; normally closed inlet vent means for admitting the pressurized gas from said source into said rear chamber; normally open outlet vent means for exhausting the pressurized gas from said rear chamber; manually actuable control means for selectively opening said inlet vent means and simultaneously closing said outlet vent means to drive the piston forward; separate control means operable when said piston reaches the forward limit of its travel for simultaneously closing said inlet vent means and opening said outlet vent means; said sliding bearing means normally providing a seal with said piston rod, and said bearing means and piston rod cooperatively providing an outlet vent for exhausting driving gas from said rear chamber only when said piston closely approaches the forward limit of its travel; and drive means operable for returning said piston to its rearward position when the driving gas has been exhausted.

Claim 8

A pump as in claim 5 wherein said separate control means is operable in response to a drop in liquid pressure at the forward end of said forward chamber, said drop in liquid pressure resulting from the combined effects of the exhausting of said driving gas from said rear chamber through said outlet vent and the release of the liquid from said forward chamber through said outlet part.

Claim 9

A pump as in claim 5 with a highly restricted bleeder hole consisting of a small diameter hole passing through the wall of said rear chamber, for slowly venting the driving gas from said rear chamber and thereby allowing said piston to return to its rearward limit.

Claim 10

A pump as in claim 1 with an adjustable sleeve for limiting the piston return thereby providing an adjustable control of the piston displacement without affecting the cooperative action of said piston rod, bearing means, and seal.

Claim 11

A pump as in claim 5 with an adjustable sleeve for limiting the piston return thereby providing an adjustable control of the piston displacement without affecting the cooperative action of said piston rod, bearing means, and seal.

Claim 12

A pump as in claim 5 wherein the said drive means operable for returning said piston consists of a spring driven piston return.

Claim 13

A pump as in claim 5 wherein said drive means operable for returning said piston is a spring driven piston return comprising: an adjustable sleeve for limiting the return travel of said piston and thereby providing displacement control, composed of a cylindrical housing having a counter-bored interior end wall; a cylindrical spring retainer disposed within the end of said housing and adapted to engage the raised circumferential portion of said housing end wall; a spring disposed within said housing and having one end received by said spring retainer; a piston rod concentric with said spring, said spring retainer having a central opening through which said piston rod slidingly passes; and a retainer member secured to tHe end of said piston rod for preventing said piston rod from being withdrawn from said spring retainer; the action being such that when the piston is returned, the piston rod is free to overtravel beyond the normal fully compressed position of the spring, temporarily extending into the recessed central portion of said housing end wall, thereby avoiding an undesired rebound of the piston rod from the housing end wall.

Claim 14

A pump as in claim 11 wherein the said adjustable sleeve has radial ribs projecting from its inside surface thereby providing guidance and stability for the said spring and piston rod.