US 4,392,390 AGranted

Shielding apparatus for linear actuator

AssigneeDuff-Norton Company, Inc.

InventorJames C. Johnson

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Abstract

A shielding bladder for the venting arrangement of a linear actuator having a housing, a reciprocable member disposed therein for linear reciprocable movement therethrough, and a venting arrangement in the housing for communicative flow of ambient air into and out of the housing during operation. The bladder is a sleeve sealably affixed exteriorly to the housing enclosing the venting arrangement and defining a chamber between the sleeve and housing that contains a volume of air for contractionally expelling the air into the housing in response to increases in its volumetric capacity resulting upon outward reciprocation of the reciprocating member and expansionally receiving air from the housing in response to decreases in its volumetric capacity upon inward reciprocation of the reciprocating member. Thus, a controlled volume of clean air free of excess moisture is contained in equilibrium between the bladder and the housing to permit normal actuator operation while preventing entrance of debris and excess moisture thereinto through its vent arrangement. A cylindrical cover protects the bladder from degradation by the ambient atmosphere and environment.

Claims7

Dependent claims

In a linear actuator of the type having a housing and a reciprocable member disposed in and projecting from said housing for reciprocating linear movement relative thereto, said housing having vent means for admitting to and exhausting from said housing ambient air responsive to fluctuations in the volumetric capacity of said housing resulting from the relative reciprocal movement of said reciprocable member respectively out of and into said housing, the improvement comprising means for shielding said vent means to prevent entrance of airborne debris and excess moisture into said housing while permitting unrestricted operational airflow through said vent means, said shielding means including bladder means sealably affixed externally to said housing surrounding said vent means for expansionally receiving and containing air exhausted through said vent means from said housing upon decreases in the volumetric capacity of said housing resulting from reciprocal movement of said reciprocable member into said housing and for contractionally expelling contained air through said vent means into said housing upon increases in the volumetric capacity of said housing resulting from reciprocal movement of said reciprocable member out of said housing, whereby a controlled predetermined volume of air may be constantly contained within and maintained in equilibrium between said housing and said bladder means to facilitate unrestricted operation of said linear actuator while preventing entrance thereinto of external airborne debris and excess moisture.

Dependencies are inferred from the claim text.