Solid material comminution or disintegration – Apparatus – Comminuting surface provided with openings to permit...
Reexamination Certificate
1999-08-06
2001-11-20
Rosenbaum, Mark (Department: 3725)
Solid material comminution or disintegration
Apparatus
Comminuting surface provided with openings to permit...
C241S293000
Reexamination Certificate
active
06318651
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a mill, in particular for milling of bone, comprising a housing provided with at least one opening, for supply of material to be milled an removal of machined chips, and a drum, provided with cutting members, which is rotably located inside the housing. With milling is meant the whole of manufacturing methods of which chips can be made, such as machining, cutting, chipping, morselizing, breaking, chopping. With chips all kind of small particles are meant like e.g. splinters, flakes, pieces, slices. With cutting members all kind of tools, such as for example knives, chisels and teeth are meant, which can be used to mill a material.
The milling of bone is a known method in the medical field, where bone chips are used for the filling of defects in bones, which are created by the removal of a tumor or cyst, or are used for filling a gap between a prosthetic stem or cup and the surrounding bone of a patient in case of a revision operation, where inevitably part of the original bone stock has been lost. Further more bone chips are used among others for the correction of deviant bony structures, so called bone plastics, for the correction of fracture defects and for fusion of joints and vertebrae. Bone chips are not rejected by the human body and they integrate with the natural existing bone.
BACKGROUND OF THE INVENTION
A mill of the type mentioned at the beginning is disclosed in the Swedish patent number 9402781-0. The bone mill described inhere has a drum provided with a number of axially elongated grooves, in which cutting blocks are seated which are removably attached to the drum and all grooves are extended in one straight line parallel to the axially direction. The separate manufacturing of the drum and the cutting blocks is an expensive method of manufacturing. Because the cutting blocks are located in one straight line and because all cutting edges of one cutting block are located in one straight line, all cutting members of one cutting block come simultaneously into contact with the bone to be milled. This results in a jerkily action and an inefficient milling process.
A similar prementioned mill is also generally known, at least in the medical field, as a mill with a drum provided with round openings which are formed by bending parts of the wall of the drum outwards and grinding cutting edges on them. Due to the shape of the cutting edges, a larger force to produce the desired large size of chips is needed than with the aforementioned known bone mill. For these reasons the milling process takes more time and effort than with the aforementioned known bone mill.
SUMMARY OF THE INVENTION
An object of the invention is to provide a mill which is less expensive to manufacture than the known bone mills. Therefore the mill of the present invention is characterized in that the drum and the cutting members are made from one piece and the cutting members are formed by local thickenings of the wall of the drum. By manufacturing the drum and the number of manufacturing steps can be reduced by simultaneous manufacturing of the drum and the cutting members.
A preferred embodiment of the mill according to this invention is characterized in that the cutting members are provided with a cutting edge which with one point protrudes in the circumferential direction of the drum, such that during operation the cutting members will contact with this point first the material to be milled. As the cutting members do not contact the bone at their full width less force is needed and the force increases more gradually which makes the mill work more efficiently than the known bone mill.
This design feature can also be applied seperately without that the drum and cutting members are made from one piece and the cutting members are formed by local thickenings of the wall of the drum. For example by attaching seperate cutting members to the drum.
In order to operate at a large axial length a further embodiment is characterized in that at least part of the cutting members are mutually displaced in the axial direction of the drum.
One embodiment which can be efficiently manufactured is characterized in that at least part of the cutting members are located along an imaginary spiralled line around the drum. Such a configuration can relativily easily be realized on a lathe.
To achieve a still greater efficiency and a smoother action of the cutting members on the bone a further embodiment is characterized in that at least part of the cutting members are mutually displaced in the circumferential direction of the drum. Because of this, only one or a few cutting members contact the bone at the same moment. It is noted that also this design feature can be applied seperately without that the drum and cutting members are made from one piece and the cutting members are formed by local thickenings of the wall of the drum and also without that the cutting members protrude with one point in the circumferential direction.
A practical advantageous embodiment is characterized in that at least part of the cutting members are located along a number of imaginary oblique lines which run at an angle with the axial direction of the drum.
A practical embodiment at which both aforementioned configurations can be manufactured efficiently is characterized in that at least part of the cutting members are located at the intersections of the imaginary oblique lines and the imaginary spiralled line. In order to remove the chips a further embodiment is characterized in that aside the imaginary oblique lines, in front of the cutting members as viewed in the direction of rotation elongated slots are present.
A preferred embodiment of the mill according to the invention which can practically advantageous be manufactured is characterized in that the drum with the cutting members is formed by machining the outer surface of a thick-walled drum, such that on the outer surface of that drum a spiralshaped rim remains which is removed at a number of places and at the remaining parts cutting edges and clearance surfaces are machined.
The invention also relates to a drum provided with cutting members applicable in the mill according to the invention. Drums with cutting members can also be marketed seperately and are of course exchangeable. Therefore various drums with different numbers and sizes of cutting members can go with one housing to produce bone chips of various sizes.
REFERENCES:
patent: 2228025 (1941-01-01), Apfelbeck
patent: 4061280 (1977-12-01), Box
patent: 1094782 (1955-05-01), None
patent: 9402781-0 (1999-02-01), None
Milde Hoffberg & Macklin, LLP
Rosenbaum Mark
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