US 12,258,955 B2
Piston assembly for an unloader valve of an air compressor
Joerg Mellar, Ebersberg (DE); Jean-Baptiste Marescot, Manerbe (FR); Bertrand Chirot, Auberville (FR); Arnaud Chazelles, Saint Sebastian sur Loire (FR); and Jean-Louis Mezza, Marolles (FR)
Assigned to KNORR-BREMSE Systeme fuer Nutzfahrzeuge GmbH, Munich (DE)
Appl. No. 17/594,121
Filed by KNORR-BREMSE Systeme fuer Nutzfahrzeuge GmbH, Munich (DE)
PCT Filed Apr. 2, 2020, PCT No. PCT/EP2020/059414
§ 371(c)(1), (2) Date Oct. 4, 2021,
PCT Pub. No. WO2020/201429, PCT Pub. Date Oct. 8, 2020.
Claims priority of application No. 19167506 (EP), filed on Apr. 5, 2019.
Prior Publication US 2022/0154713 A1, May 19, 2022
Int. Cl. F04B 49/03 (2006.01); B60T 17/02 (2006.01); F04B 39/06 (2006.01); F04B 53/10 (2006.01)
CPC F04B 49/03 (2013.01) [B60T 17/02 (2013.01); F04B 39/06 (2013.01); F04B 53/10 (2013.01)] 14 Claims
OG exemplary drawing
 
1. A piston assembly for an unloader valve of an air compressor, the piston assembly comprising:
an unloader piston having an end portion with a first bore of a first bore diameter, an intermediate portion with a second bore of a second bore diameter and an opposite end portion with a third bore of a third bore diameter, wherein the first bore diameter is larger than the second bore diameter which, in turn, is larger than the third bore diameter;
a coil spring having a central opening, one end portion disposed in the second bore of the unloader piston and an opposite end portion extending into the first bore of the unloader piston; and
a balance piston including a head portion having a diameter to be disposed in the first bore of the unloader piston, and a stem portion extending from the head portion into the central opening of the coil spring and having a diameter smaller than the diameter of the head portion;
wherein the diameter of the stem portion at an end portion of the stem portion facing away from the head portion substantially corresponds to an inner diameter of the central opening of the coil spring; and
wherein the balance piston includes a heat protection element, wherein the heat protection element comprises a section between an end portion extending from the head portion and the end portion facing away from the head portion, the section being grooved, and a heat shield formed by the end portion facing away from the head portion, the grooved section having a reduced diameter that reduces the heat transfer through the stem portion towards the head portion of the balance piston.