# US 10,371,145 B2 · Piston rod having cap recess > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,371,145 B2 - Document ID: US10371145B2 - Status: Granted - Kind: B2 - Application number: 15/404,728 - Filed: 2017-01-12 - Published: 2017-07-13 - Granted: 2019-08-06 - Earliest claimed: 2016-01-12 - Assignees: Graco Minnesota Inc. - Applicants: Graco Minnesota Inc. - Inventors: Justin G. Johnston; Andrew J. Kopel; Brian M. Mulgrew; Steve J. Wrobel - Web page: https://patentgrep.com/patent/US10371145B2 ## CPC - F04B 53/144: {Adaptation of piston-rods} - B05B 9/0413: {with reciprocating pumps, e.g. membrane pump, piston pump, bellow pump (B05B9/0409 takes precedence)} - F04B 1/0413: Cams - F04B 1/0426: Arrangements for pressing the pistons against the actuated cam; Arrangements for connecting the pistons to the actuated cam - F04B 1/0531: with cam-actuated distribution members - F04B 9/042: {the means being cams} - F04B 15/02: the fluids being viscous or non-homogeneous - F04B 17/06: Mobile combinations - F04B 53/02: Packing the free space between cylinders and pistons - F04B 53/14: Pistons, piston-rods or piston-rod connections - F04B 53/146: {Piston-rod guiding arrangements} - F04B 53/147: {Mounting or detaching of piston rod} - F04B: POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS (machines for liquids, or pumps, of rotary-piston or oscillating-piston type F04C; non-positive-displacement pumps F04D; pumping of fluid by direct contact of another fluid or by using inertia of fluid to be pumped F04F) - B05B: SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES (spray-mixers with nozzles B01F25/72; processes for applying liquids or other fluent materials to surfaces by spraying B05D) ## Abstract A piston rod for pumping paint includes an elongated cylindrical stem and a piston rod cap connected to the cylindrical stem. The cylindrical stem is formed from metal and has an outer diameter that is uniform along most or all of a length of the cylindrical stem. The piston rod cap is cylindrical and formed from metal. The piston rod cap includes an annular top portion that has an outer diameter that is larger than the outer diameter of the cylindrical stem, an annular bottom portion that has an outer diameter that is larger than the outer diameter of the cylindrical stem, and an exterior recess located between the annular top and bottom portions. The recess has an outer diameter that is smaller than the outer diameters of the annular top and bottom portions. ## Claims ### Claim 1 A piston rod for pumping paint, the piston rod comprising: an elongated cylindrical stem, the cylindrical stem being formed from metal and having an outer diameter that is uniform along most or all of a length of the cylindrical stem; and a piston rod cap connected to the cylindrical stem, the piston rod cap being cylindrical and formed from metal, the piston rod cap comprising: an annular top portion having an outer diameter that is larger than the outer diameter of the cylindrical stem; an annular bottom portion having an outer diameter that is larger than the outer diameter of the cylindrical stem; and an exterior recess located between the annular top and bottom portions, the recess having an outer diameter that is smaller than the outer diameters of the annular top and bottom portions; wherein the recess has a depth in the range of 0.010 to 0.125 inches, and the recess has a height in the range of 0.030 to 0.375 inches. ### Claim 2 (depends on 1) The piston rod of claim 1, wherein the outer diameters of the annular top and bottom portions are equal. ### Claim 3 (depends on 1) The piston rod of claim 1, wherein the recess is a groove that extends entirely around a circumference of the piston rod cap. ### Claim 4 (depends on 1) The piston rod of claim 1, wherein a bottom of the cylindrical stem is configured to contact paint and pump the paint by reciprocation of the cylindrical stem. ### Claim 5 (depends on 1) The piston rod of claim 1, wherein the cylindrical stem is formed from a separate piece of metal than the piston rod cap. ### Claim 6 (depends on 1) The piston rod of claim 1, wherein the piston rod cap comprises a cavity that receives the cylindrical stem. ### Claim 7 (depends on 1) The piston rod of claim 1, wherein the piston rod cap is press fit on a top of the cylindrical stem to fix the piston rod cap to the cylindrical stem. ### Claim 8 (depends on 1) The piston rod of claim 1, wherein the outer diameter of the cylindrical stem is uniform along the entire length of the cylindrical stem. ### Claim 9 (depends on 1) The piston rod of claim 1, wherein the piston rod consists only of the cylindrical stem and the piston rod cap. ### Claim 10 (depends on 1) The piston rod of claim 1, wherein the recess has a rounded concave-shaped cross-sectional profile. ### Claim 11 (depends on 1) The piston rod of claim 1, wherein the recess has a cross-sectional profile selected from the group consisting of: a V-shaped cross-section, a saw-tooth-shaped cross-section, and a square-shaped cross-section. ### Claim 12 (depends on 1) The piston rod of claim 1, wherein the annular top portion of the piston rod cap comprises a top surface that is flat. ### Claim 13 (depends on 1) The piston rod of claim 1, wherein the annular bottom portion of the piston rod cap comprises an annular bottom surface that is flat. ### Claim 14 (depends on 1) The piston rod of claim 1, wherein the recess is configured to trap contaminants. ### Claim 15 (depends on 1) A piston rod assembly comprising: a piston rod according to claim 1; and a packing retainer that surrounds a portion of the cylindrical stem such that the cylindrical stem extends out of opposite sides of the packing retainer and the piston rod cap is outside of the packing retainer, the packing retainer holding one or more packing seal rings around and in contact with the cylindrical stem. ### Claim 16 (depends on 1) A piston pump assembly comprising: a piston rod according to claim 1; and a yoke having a pocket, the pocket having a bottom portion that is narrower than a top portion of the pocket, and the piston rod being insertable into the pocket of the yoke such that the yoke cradles the piston rod cap to linearly move the piston rod as the yoke moves. ### Claim 17 (depends on 16) The piston pump assembly of claim 16, wherein the pocket further comprises one or more inward projections that extend into the recess of the piston rod cap as the piston rod cap is cradled by the yoke. ### Claim 18 A piston rod for pumping paint comprising: an elongated cylindrical stem formed from a first piece of metal, the cylindrical stem having an outer diameter that is uniform along most or all of a length of the cylindrical stem; and a piston rod cap connected to the cylindrical stem and formed from a second piece of metal that is separate from the first piece of metal, the piston rod cap comprising: an annular top portion having an outer diameter that is larger than the outer diameter of the cylindrical stem, the annular top portion having a top surface that is flat; an annular bottom portion having an outer diameter that is larger than the outer diameter of the cylindrical stem; an exterior recess located between the annular top and bottom portions and having an outer diameter that is smaller than the outer diameters of the annular top and bottom portions, the recess comprising an annular groove that extends around an entire circumference of the piston rod cap; and a cavity that receives a top portion of the cylindrical stem; wherein the recess has a depth in the range of 0.010 to 0.125 inches, and the recess has a height in the range of 0.030 to 0.375 inches. ### Claim 19 A piston pump assembly for pumping paint comprising: a piston rod comprising: an elongated cylindrical stem formed from a first piece of metal, the cylindrical stem having an outer diameter that is uniform along most or all of a length of the cylindrical stem; and a piston rod cap connected to the cylindrical stem, the piston rod cap comprising: an annular top portion having an outer diameter that is larger than the outer diameter of the cylindrical stem, the annular top portion having a top surface that is flat; an annular bottom portion having an outer diameter that is larger than the outer diameter of the cylindrical stem, the annular bottom portion having an annular bottom surface that is flat; a recess located between the annular top and bottom portions and smaller in outer diameter than the annular top and bottom portions, the recess comprising an annular groove that extends around an entire circumference of the piston rod cap, wherein the recess has a depth in the range of 0.010 to 0.125 inches, and the recess has a height in the range of 0.030 to 0.375 inches; and a cavity that receives a top portion of the cylindrical stem to connect the piston rod cap to the cylindrical stem; and a packing retainer that surrounds a portion of the cylindrical stem such that the cylindrical stem extends out of opposite sides of the packing retainer and the piston rod cap is outside of the packing retainer, the packing retainer holding one or more packing seal rings around and in contact with the cylindrical stem. ### Claim 20 A piston rod for pumping paint, the piston rod comprising: an elongated cylindrical stem, the cylindrical stem being formed from metal and having an outer diameter that is uniform along most or all of a length of the cylindrical stem; and a piston rod cap connected to the cylindrical stem, the piston rod cap being cylindrical and formed from metal, the piston rod cap comprising: an annular top portion having an outer diameter that is larger than the outer diameter of the cylindrical stem; an annular bottom portion having an outer diameter that is larger than the outer diameter of the cylindrical stem; and an exterior recess located between the annular top and bottom portions, the recess having an outer diameter that is smaller than the outer diameters of the annular top and bottom portions; wherein the piston rod cap is press fit on a top of the cylindrical stem to fix the piston rod cap to the cylindrical stem; wherein the recess has a depth in the range of 0.010 to 0.125 inches, and the recess has a height in the range of 0.030 to 0.375 inches. ### Claim 21 (depends on 20) The piston rod of claim 20, wherein the outer diameters of the annular top and bottom portions are equal. ### Claim 22 (depends on 20) The piston rod of claim 20, wherein the outer diameter of the cylindrical stem is uniform along the entire length of the cylindrical stem. ### Claim 23 (depends on 20) The piston rod of claim 20, wherein the piston rod consists only of the cylindrical stem and the piston rod cap. ### Claim 24 (depends on 20) The piston rod of claim 20, wherein the annular top portion of the piston rod cap comprises a top surface that is flat. ### Claim 25 A piston rod for pumping paint, the piston rod comprising: an elongated cylindrical stem, the cylindrical stem being formed from metal and having an outer diameter that is uniform along most or all of a length of the cylindrical stem; and a piston rod cap connected to the cylindrical stem, the piston rod cap being cylindrical and formed from metal, the piston rod cap comprising: an annular top portion having an outer diameter that is larger than the outer diameter of the cylindrical stem; an annular bottom portion having an outer diameter that is larger than the outer diameter of the cylindrical stem; and an exterior recess located between the annular top and bottom portions, the recess having an outer diameter that is smaller than the outer diameters of the annular top and bottom portions; wherein the recess is configured to trap contaminants. ### Claim 26 (depends on 25) The piston rod of claim 25, wherein the outer diameters of the annular top and bottom portions are equal. ### Claim 27 (depends on 25) The piston rod of claim 25, wherein the recess is a groove that extends entirely around a circumference of the piston rod cap. ### Claim 28 (depends on 25) The piston rod of claim 25, wherein the cylindrical stem is formed from a separate piece of metal than the piston rod cap. ### Claim 29 (depends on 25) The piston rod of claim 25, wherein the piston rod cap comprises a cavity that receives the cylindrical stem. ### Claim 30 (depends on 25) The piston rod of claim 25, wherein the piston rod cap is press fit on a top of the cylindrical stem to fix the piston rod cap to the cylindrical stem. ### Claim 31 (depends on 25) The piston rod of claim 25, wherein the outer diameter of the cylindrical stem is uniform along the entire length of the cylindrical stem. ### Claim 32 (depends on 25) The piston rod of claim 25, wherein the piston rod consists only of the cylindrical stem and the piston rod cap. ### Claim 33 (depends on 25) The piston rod of claim 25, wherein the annular top portion of the piston rod cap comprises a top surface that is flat. ### Claim 34 (depends on 25) The piston rod of claim 25, wherein the annular bottom portion of the piston rod cap comprises an annular bottom surface that is flat. ### Claim 35 (depends on 25) A piston rod assembly comprising: a piston rod according to claim 25; and a packing retainer that surrounds a portion of the cylindrical stem such that the cylindrical stem extends out of opposite sides of the packing retainer and the piston rod cap is outside of the packing retainer, the packing retainer holding one or more packing seal rings around and in contact with the cylindrical stem. ### Claim 36 A piston rod for pumping paint, the piston rod comprising: an elongated cylindrical stem, the cylindrical stem being formed from metal and having an outer diameter that is uniform along most or all of a length of the cylindrical stem; and a piston rod cap connected to the cylindrical stem, the piston rod cap being cylindrical and formed from metal, the piston rod cap comprising: an annular top portion having an outer diameter that is larger than the outer diameter of the cylindrical stem; an annular bottom portion having an outer diameter that is larger than the outer diameter of the cylindrical stem; and an exterior recess located between the annular top and bottom portions, the recess having an outer diameter that is smaller than the outer diameters of the annular top and bottom portions; wherein the recess has a rounded concave-shaped cross-sectional profile. ### Claim 37 A piston rod for pumping paint, the piston rod comprising: an elongated cylindrical stem, the cylindrical stem being formed from metal and having an outer diameter that is uniform along an entire length of the cylindrical stem; and a piston rod cap connected to the cylindrical stem, the piston rod cap being cylindrical and formed from metal, the piston rod cap comprising: an annular top portion having an outer diameter that is larger than the outer diameter of the cylindrical stem; an annular bottom portion having an outer diameter that is larger than the outer diameter of the cylindrical stem; and an exterior recess located between the annular top and bottom portions, the recess having an outer diameter that is smaller than the outer diameters of the annular top and bottom portions; wherein the piston rod consists only of the cylindrical stem and the piston rod cap; wherein the recess has a depth in the range of 0.010 to 0.125 inches, and the recess has a height in the range of 0.030 to 0.375 inches.