Patent US1578943 (http://l2.espacenet.com/dips/viewer?PN=US1578943&CY=gb&LG=en&DB=EPD)
,Patent US1875916 (http://l2.espacenet.com/dips/viewer?PN=US1875916&CY=gb&LG=en&DB=EPD)
&Patent US2370524 (http://l2.espacenet.com/dips/viewer?PN=US2370524&CY=gb&LG=en&DB=EPD)
:)