The knife (1A) has a blade (10) i.e. dual blade, including a blade wing (101), which is narrowed at front to form a cutting edge and connected at rear of a blade back (103). An end part of a U-shaped coupling element (181) is welded at one of two side surfaces of the blade back, where the coupling element is extended in an arc. Another end part of the coupling element includes a connector i.e. threaded bore, that is connected with an energy converter to supply ultrasonic energy. The coupling element is provided at each end of the blade back. An independent claim is also included for a cutting device.
