Patent ID: 8575921

Claim:
An apparatus for monitoring the movement of a piston slidably disposed within in a housing comprising: (a) a pin having a first end responsive to movements of said piston in said housing, wherein said pin is disposed within a bore of an indicator body, wherein said pin has a second end which is magnetically coupled to a first ring magnet having a north and a south pole slidably disposed on a magnet carrier of said indicator body, wherein said indicator body further comprises a first threaded portion engagable with an internal thread portion of said housing, (b) a second ring magnet having a north and south pole disposed on said magnet carrier for repelling said first ring magnet and, (c) a retainer for holding said first ring magnet and said second ring magnet on said magnet carrier comprising: (i) an end cap which is secured to said magnet carrier for holding said second ring magnet, and (ii) a surface of said indicator body for holding said first ring magnet, wherein a transparent sleeve which is securable coaxially with said magnet carrier between said end cap and said surface of said indicator body and wherein said first ring magnet is observable through said transparent sleeve.