Piston pump esp. for low temperature appliances - has fluid chamber around cylinder jacket, and overflow valve on cylinder end

摘要

The cylinder jacket (1) in the pump is enclosed by a fluid chamber (28), at least in the charging chamber (19) area. At least one overflow valve (29) is located stationary on the end side of the cylinder, and projects into the fluid chamber (28). The valve is spring loaded (30). A guide sleeve (31) is located between cylinder jacket and piston rod (9). The sleeve has a relief groove (32) near its outer end, which is connected via a connection bore (33) to the fluid chamber, pref. in the area of the overflow valve. The guide sleeve consists of the same material as the guide rings (25) of the piston (8), esp. of a sinter material bronze/Teflon, or Teflon/carbon.