Web-tension sensing and control apparatus

Claim 1

A web tension sensing and control apparatus for sensing and controlling the tension of a web of paper, plastic resinous film, or the like, fed from a roll thereof carried by a roll-supporting shaft, comprising: a. supporting means; b. web-tension sensing means movably mounted on the said supporting means and adapted to bear upon the said web above the latter; c. pneumatically operated braking means on the said rollsupporting shaft for braking the action of said roll-supporting shaft; d. air supply means for supplying air under pressure to the said pneumatically operated braking means; e. first air valve control means for controlling the flow of air to said pneumatically operated braking means to actuate the latter; f. power means for operating the said first air valve control means; g. pneumatically controlled power transmission means for operating the said power means; h. pneumatic control means under the control of the said webtension sensing means for controlling the operation of the said pneumatically controlled power transmission means and including 1 a pneumatic sensing head having therein (a) a throat portion; 2 a sensing member operable by and responsive to movement of the said web-tension-sensing means and having a portion movable into and out of the said throat portion of the said pneumatic sensing head; and 3 second air valve control means under the control of the said pneumatic sensing head and the said throat portion thereof and the said portion of the said sensing member and responsive to the position of the said portion of the said sensing member in and relative to the said throat portion of the said pneumatic sensing head for controlling the operation of the said pneumatically controlled power transmission means.