Pump with pumping chamber created by telescoping action driven by friction

A fluid delivery device comprising;

• a housing;
• a piston configured to be controllably translated within the housing;
• a plug having a distal end thereof connected to a proximal end of the piston, the plug being configured to translate within the housing;
• wherein the proximal end of the piston is configured with a region therein that defines a telescopic fluid chamber in which the distal end of the plug can translate relative to the piston to permit fluid to flow into the fluid chamber and to discharge fluid from the fluid chamber;
• wherein the housing comprises a reservoir port through which fluid is introduced into the housing and a patient port through which fluid is discharged from the housing;
• wherein the piston is controllably translated to align the fluid chamber with the reservoir port during an intake operation of the fluid delivery device, and to align the fluid chamber with the patient port during a discharge operation of the fluid delivery device
• wherein the plug and the piston are each provided with a seal, and the respective seals are configured to confine fluid in the fluid chamber between the seals;
• and
• wherein the plug is configured with a frictional engagement relative to the housing that provides an amount of friction to cause translation of the plug to lag relative to the piston until the amount of friction is overcome by translation of the piston, and the seal on the piston is configured to contribute to the amount of friction.