Claims
- 1. Apparatus for transmitting electrically conductive coating material from a source to an electrostatic coating dispenser, comprising:
- a piston pump, including:
- (i) a pump wall having opposed ends which define an internal reservoir;
- (ii) a piston head movable along said pump wall within said reservoir, said piston head having opposed sides and an outer periphery carrying a pair of seals which are spaced from one another;
- (iii) means connected to said piston head and communicating exteriorly of said reservoir for introducing a liquid into said space between said seals carried by said piston head;
- first transfer means for transferring coating material from the source into said reservoir of said piston pump on one side of said piston head;
- second transfer means for transferring coating material from said reservoir of said piston pump to the electrostatic coating dispenser, said second transfer means including means for introducing operating fluid into said reservoir of said piston pump on the other side of said piston head to force the coating material from said reservoir;
- means for electrically isolating said second transfer means from the electrostatic coating dispenser while transferring coating material into said reservoir of said pump; and
- means for electrically isolating said first transfer means from the source while transferring coating material from said reservoir of said pump to said electrostatic coating dispenser.
- 2. The apparatus of claim 1 in which said means for introducing a liquid into said space between said seals of said piston head is effective to lubricate said piston head as it moves along said pump wall, and to substantially prevent drying of coating material on said pump wall.
- 3. The apparatus of claim 1 in which said means for introducing a liquid into said space between said seals of said piston head is effective to substantially remove coating material or operating fluid from said space between said seals of said piston head.
- 4. The apparatus of claim 1 in which said means for introducing a liquid into said space between said seals of said piston head is effective to relieve fluid pressure within said space between said seals of said piston head created by the passage of operating fluid or coating material into said space.
- 5. The apparatus of claim 1 in which said means for introducing a liquid into said space between said seals of said piston head comprises:
- a piston shaft formed with a bore, said piston shaft being connected to said piston head and having an end extending exteriorly of said reservoir;
- at least one passageway formed in said piston head which extends between said bore in said piston shaft and said outer periphery of said piston head between said spaced seals therein;
- means for introducing a liquid into said bore in said piston shaft, through said passageway in said piston head and into said space between said seals on said piston head.
- 6. The piston pump of claim 5 in which said means for introducing a liquid comprises a tube connected to said piston shaft in communication with said bore therein, and a vented cap mounted to said tube, said tube and said vented cap being adapted to be filled with said liquid.
Parent Case Info
This is a continuation-in-part application of Ser. No. 07/554,795, filed July 18, 1990, now U.S. Pat. No. 5,078,168 and entitled "Apparatus For Electrostatically Isolating Conductive Coating Materials", which is owned by the assignee of this invention.
US Referenced Citations (29)
Foreign Referenced Citations (1)
Number |
Date |
Country |
2853347 |
Nov 1978 |
DEX |
Continuation in Parts (1)
|
Number |
Date |
Country |
Parent |
554795 |
Jul 1990 |
|