Encoder apparatus

Abstract

An encoder apparatus comprising a scale and a readhead assembly comprising a scale signal receiver. The scale and the scale signal receiver are located within a protective housing which is configured to protect them from contamination located outside the protective housing and comprises a seal through which the scale signal receiver can be connected to a part outside the protective housing. The arrangement of the scale signal receiver inside the protective housing is independent of the scale and protective housing.

1 . A readhead for an encoder apparatus comprising at least one vibration control device configured to vibrate independently of the rest of the readhead and configured to reduce a susceptibility of the readhead to vibrations. 
     
     
         2 . A readhead as claimed in  claim 1 , in which the vibration control device is connected to only a single unitary body of the readhead. 
     
     
         3 . A readhead as claimed in  claim 1 , in which the vibration control device is configured to reduce the amplitude of vibrations of the readhead at and around the readhead's resonant frequency. 
     
     
         4 . A readhead as claimed in  claim 1 , in which the vibration control device resides within the readhead. 
     
     
         5 . A readhead as claimed in  claim 4 , in which the vibration control device resides within an outer case of the readhead. 
     
     
         6 . A readhead as claimed in  claim 4 , in which the vibration control device resides within a void defined by the readhead and is configured to vibrate within said void independently of the rest of the readhead. 
     
     
         7 . A readhead as claimed in  claim 5 , in which the vibration control device resides within a void defined by the readhead and is configured to vibrate within said void independently of the rest of the readhead. 
     
     
         8 . A readhead as claimed in  claim 1 , in which the at least one vibration control device comprises a cylindrical body with a first elastomer ring disposed on one end of the cylindrical body, and a second elastomer ring disposed on another end of the cylindrical body. 
     
     
         9 . A readhead as claimed in  claim 1 , in which the at least one vibration control device comprises at least one member which is configured with a resonant frequency independent of the readhead. 
     
     
         10 . A readhead as claimed in  claim 1 , in which the at least one vibration control device comprises one or more spring elements, one or more mass elements, and one or more damper elements. 
     
     
         11 . A readhead as claimed in  claim 10 , in which at least one of the one or more spring elements, at least one of the one or more mass elements, and at least one of the one or more damper elements are provided by a single spring mass damper element. 
     
     
         12 . A readhead as claimed in  claim 1 , in which the at least one vibration control device comprises a tuned mass damper. 
     
     
         13 . A readhead as claimed in  claim 1 , in which the readhead comprises at least one scale signal receiver part for receiving a signal from a scale, in which the scale signal receiver part comprises said vibration control device. 
     
     
         14 . A readhead as claimed in  claim 13 , in which the readhead comprises a mount part comprising mounting features for securing the readhead to a part of a machine, and in which the scale signal receiver part of the readhead is rigidly connected to the mount part. 
     
     
         15 . An encoder apparatus comprising a scale and a readhead as claimed in  claim 1 . 
     
     
         16 . An encoder apparatus as claimed in  claim 13 , in which the scale and the scale signal receiver are located within a protective housing which is configured to protect them from contamination located outside the protective housing, the scale signal receiver and the protective housing being relatively moveable with respect to each other, the protective housing comprising a seal through which the scale signal receiver can be connected to a part outside the protective housing. 
     
     
         17 . An encoder apparatus as claimed in  claim 15 , in which the scale and a scale signal receiver are located within a protective housing which is configured to protect them from contamination located outside the protective housing, the scale signal receiver and the protective housing being relatively moveable with respect to each other, the protective housing comprising a seal through which the scale signal receiver can be connected to a part outside the protective housing.