Metal deforming – With use of control means energized in response to activator... – Sensing tool or tool-linked part
Reexamination Certificate
2001-04-13
2003-09-02
Crane, Daniel C. (Department: 3725)
Metal deforming
With use of control means energized in response to activator...
Sensing tool or tool-linked part
C072S014800, C072S295000, C072S307000, C072S311000, C072S342960, C433S003000
Reexamination Certificate
active
06612143
ABSTRACT:
BACKGROUND OF THE INVENTION
A. Field of the Invention
This invention relates to a robot and method for automatically bending orthodontic archwires, retainers, or other orthodontic or medical devices into a particular shape.
B. Description of Related Art
In orthodontics, a patient suffering from a malocclusion is treated by affixing brackets to the surface of the teeth and installing an archwire in the slots of the brackets. The archwire and brackets are designed to generated a customized force system that applies forces to teeth, by which individual teeth are moved relative to surrounding anatomical structures into a desired occlusion. There are two approaches to designing an appropriate force system for a patient. One is based on a flat archwire and customized brackets, e.g., Andreiko et al., U.S. Pat. No. 5,447,432. The other is based on off-the shelf brackets and designing a customized archwire that has complex bends designed to move or rotate the teeth in the desired direction. Traditionally, the latter approach has required manual bending of the archwire by the orthodontist.
Machines for bending orthodontic archwires have been proposed in the prior art. Andreiko et al. describes an apparatus that takes a straight archwire and imparts a simple planar arcuate curvature to the wire. The wire is customized in the sense that the shape of the arc is designed for a particular patient, but the wire bending apparatus described in Andreiko et al. is limited to a customized bracket approach to orthodontics. In particular, the Andreiko et al. wire bending apparatus cannot produce any complex and twists bends in the wire, e.g., bends requiring a combination of translation and rotational motion.
The patent to Orthuber et al., U.S. Pat. No. 4,656,860 describes a bending robot for bending archwires. A robot as described in the '860 patent was developed by the predecessor of the assignee of the present invention and used experimentally for several years, but never widely commercialized. The robot consisted of two characteristic design features: a bending cone that could move forwards and backwards to bend the wire, and a rotating cone that could twist the wire. As such, it could only apply torque or bends over the two main axes of a cross section of a rectangular shaped wire. Since the portion of the wire extending beyond the cone is free and unconstrained, the robot had no control as to the effective deformation of the wire. Additionally, a series of three twists and two bends were typically required by a robot in accordance with the '860 patent to shape an archwire so that it would fit in the slots of two adjacent brackets. This series of twists and bends required as much as 5 mm of wire length between adjacent brackets. This length of wire is greater than that available for closely spaced teeth, such as the lower front teeth. To avoid this situation, the robot bent a twisted portion of the wire, which provoked-uncontrolled rotational motion in the wire.
The design of the '860 patent also has other shortcomings: it provides no means for measuring forces imparted by the wire since one end of the wire is free and the wire is gripped immediately below the bending point. The robot had no effective feedback mechanism for detecting how the wire in fact was bent after a particular bending or twisting operation was performed. As the free end of the wire is not constrained or held in any manner, there is no ready way to heat the wire as it is being bent in order to fix the shape of the bend in a wire made from a shape memory material. Consequently, shape memory alloy wires made with the '860 patent were subject to a separate heating treatment in a separate thermal device.
The present invention presents a substantial improvement to the robot of the '860 patent. The invention also provides for much greater flexibility in the design and manufacture of archwires than that disclosed by the Andreiko et al. patent. In particular, the present invention enables the manufacture of custom, highly accurate orthodontic archwires. Such wires are ideally suited to an archwire-based orthodontic treatment regime based on standard, off-the-shelf brackets. The invention is also readily adaptable to bending other medical devices, including implants such bone fixation plates, prostheses, orthotic devices, and even surgical tools.
SUMMARY OF THE INVENTION
In a first aspect, a bending apparatus or machine is provided for bending an orthodontic appliance, such as a retainer or archwire, into a desired configuration. While the orthodontic device is described as being an archwire in the illustrated embodiment, other types of medical devices are contemplated as the type of article capable of being bent by the robot. Examples of such medical devices are prostheses, orthotic devices, implants, fixation plates, spectacle frames, and surgical devices such as a reamer for root canals.
The bending apparatus or machine may take the form of a robot mounted to a base or table support surface. A first gripper tool is provided. This tool can either be fixed with respect to the base or may be incorporated into a moveable arm. The first gripping tool has a first gripping structure for holding the archwire or other medical device. The bending apparatus includes a moveable arm having a proximal portion mounted to the base a distance away from the first gripper tool and a free distal end portion. The moveable arm is constructed such that the free distal portion of the moveable arm is capable of independent movement relative to the first gripper tool along at least one translation axis and about at least one rotation axis. In an illustrated embodiment, the moveable arm has a set of joints which allows the distal end of the arm to move in 6 degrees of freedom—orthogonal translational axes and 3 orthogonal rotational axes. However, depending on the nature of the medical device and the required bends to form in the device, a lesser number of degrees of freedom may be appropriate, reducing the cost and complexity of the bending apparatus.
A second gripping tool is mounted to the distal portion of the moveable arm. The second gripping tool has a gripping structure for gripping the archwire. Thus, the archwire is gripped by the first and second gripping tools, with the second, moveable gripping tool capable of motion relative to the first gripping tool along at least one translational axis and at least one rotational axis.
The robot further includes a control system operative of the moveable arm and the first and second gripping tools so as to cause the first and second gripping tools to grip the archwire while the gripping tools are separated from each other and to cause the second gripping tool to move about at least one of the rotational axis and translation axis to thereby bend the archwire a desired amount. Preferably, the control system reads an input file containing information as to the shape of the archwire (or location of bending points along the wire) and responsively operates the moveable arm and first and second gripping tools to form a series of bends and/or twists in the archwire.
The nature of the bends in the archwire will be dictated by the orthodontic prescription and the type of force system that the orthodontist has chosen for the patient. Complex bends involving a combination of bends and twists are possible with the robot. For such complex bends, it has been found that a six-axis robot, in which the second gripping tool is capable of movement relative to the first gripping tool about three translation axes and three rotation axes, is a preferred embodiment.
Orthodontic archwires and other medical devices may have elastic properties such that when a certain amount of force is applied to the workpiece, it returns to its original configuration at least to some degree. What this means is that when a certain bend is formed in the wire, say a 10 degree bend, the wire may take a shape of an 8 degree bend due to this elastic property. Hence, some overbending of the archwire may be needed to account for t
Butscher Werner
Riemeier Friedrich
Rubbert Rüdger
Weise Thomas
Crane Daniel C.
McDonnell & Boehnen Hulbert & Berghoff
OraMetrix Inc.
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