Apparatus for machining a material web

Apparatus for machining a material web (2), with an ultrasonic unit (8) having a sonotrode (9) and with a counterstay tool (11), the material web (2) being led through a nip between the sonotrode (9) and the counterstay tool (11) and being machined by the sonotrode (9), the sonotrode (9) being clamped in a slide (4) and the slide (4) being adjustable in relation to the counterstay tool (11) via an adjusting device, said adjusting device comprising a toggle lever system including first and second toggle lever arms respectively having first end portions pivotally attached to each other at a toggle-joint first pivot with a second end portion of said first toggle lever arm being pivotally attached at a second pivot to a member that is substantially stationary to said counterstay tool and a second end portion of said second toggle lever arm being pivotally attached to said slide at a third pivot with a sensor (26) connected to a control or regulating device(28) which controls pivoting of said first and second rigid pivoting arm relative to each other about said toggle joint to thereby move said slide relative to said counterstay tool and control a clearance (A) between the sonotrode (9) and the counterstay tool (11), as a function of a signal from the sensor (26), wherein the sensor is a compression force sensor (26) arranged on one of said first and second toggle lever arms for measuring the compression force acting along said one of said first and second toggle lever arms for thereby measuring a force acting on the sonotrode (9) in the direction of the counterstay tool (11).