Piston rod having cap recess

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.

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.

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.

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.

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.

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.