Patent ID: 11925516
Assignee: J. MORITA MFG. CORP.
Field: Medical technology (Instruments)
Classification: CPC A | IPC A

Claim 0:
1. A dental treatment apparatus comprising:
a handpiece having a head to hold a cutting tool;
a drive circuitry capable of forward rotation drive in which the cutting tool held by the head of the handpiece is rotated in a cutting direction and reverse rotation drive in which the cutting tool is rotated in a non-cutting direction;
a control circuitry configured to control the drive circuitry configured to drive the cutting tool;
a load detector configured to detect a load applied to the cutting tool; and
a cumulative rotation amount calculator configured to calculate a cumulative amount of rotation which is a sum of angles of rotation of the cutting tool driven with the forward rotation drive and of angles of rotation of the cutting tool driven with the reverse rotation drive, wherein the angles of rotation in the forward rotation drive are represented by positive values and the angles of rotation in the reverse rotation drive are represented by negative valves, wherein the cumulative rotation amount calculator measures whether or not the cumulative amount of rotation is within a range not exceeding a fracture angle of the cutting tool,
the control circuitry being configured to control a switching between drive patterns of the cutting tool, wherein
in a first drive pattern, the control circuitry is configured to repeat drive of the cutting tool in the forward rotation drive by a predetermined first amount of rotation, while the load applied to the cutting tool and detected by the load detector is equal to or less than the reference load,
the control circuitry switches the cutting tool from the first drive pattern to a second drive pattern when the load applied to the cutting tool and detected by the load detector is greater than the reference load, and
in the second drive pattern, the control circuitry is configured to repeat drive of the cutting tool in the forward rotation drive by the predetermined first amount of rotation and the reverse rotation drive by a predetermined second amount of rotation that is smaller than the predetermined first amount of rotation, while the cumulative amount of rotation calculated by the cumulative rotation amount calculator is less than a reference amount of rotation, and the load applied to the cutting tool and detected by the load detector is continuously greater than the reference load,
the control circuitry switches the cutting tool from the second drive pattern to a third drive pattern when the cumulative amount of rotation calculated by the cumulative rotation amount calculator is equal to or greater than the reference amount of rotation, and the load applied to the cutting tool and detected by the load detector is continuously greater than the reference load,
in the third drive pattern, the control circuitry is configured to drive the cutting tool to eliminate twist therein by at least one of a) stopping drive of the cutting tool; b) driving the cutting tool in a direction reverse to a rotation direction in which the cumulative amount of rotation calculated by the cumulative rotation amount calculator is equal to or great than the reference amount of rotation; c) driving the cutting tool in the reverse rotation drive by a predetermined third amount of rotation and the forward rotation drive by a predetermined fourth amount or rotation that is smaller than the predetermined third amount of rotation, while the cumulative amount of rotation calculated by the cumulative rotation amount calculator is greater than the reference amount of rotation, and the load applied to the cutting tool and detected by the load detector is continuously greater than the reference load; d) driving the cutting tool in the forward rotation drive or the reverse rotation drive such that the cumulative amount of rotation calculated by the cumulative rotation amount calculator attains or is close to zero; or e) driving the cutting tool in the forward rotation drive or the reverse rotation drive such that the cumulative amount of rotation calculated by the cumulative rotation amount calculator is smaller than the reference amount of rotation.