US 3348795 A
Description (OCR text may contain errors)
Oct 4, 1967 c. G. SCHILLING 3,348,795
MACHINE BASE Filed Dec. 15, 1965 INVENTOR. CHARLES 6. SCH/LL/NG A f rorney United States Patent Oflice 3,348,795 Patented Oct. 24, 1967 3,348,795 MACHINE BASE Charles G. Schilling, Franklin Township, Westmoreland County, Pa., assignor to United States Steel Corporation, a corporation of Delaware Filed Dec. 15, 1965, Ser. No. 513,987 3 Claims. (Cl. 248-19) ABSTRACT OF THE DISCLOSURE A machine base formed of welded steel plates which define compartments. Sand is packed tightly in the compartments to prevent chattering of a machine mounted on the base.
This invention relates to an improved machine base.
Various machines, such as those used for milling, drilling, or grinding, are subject to chattering as they operate. Chatter is a form of vibration which reduces the life of a cutting tool and has a detrimental efiect on machine accuracy. Elimination of chatter is a major consideration in the design of various machines. To eliminate chatter, the machine base must have adequate damping and stiffness characteristics. Adequate damping can be achieved by using a sufiicient volume of a material, such as cast iron, which has a high internal damping coeflicient. Certain other materials, such as welded steel, are cheaper than cast iron and have more stiffness, but they do not have adequate damping characteristics.
An object of the present invention is to provide an improved machine base which is constructed largely of welded steel plates, yet offers excellent damping characa teristics, as Well as stiffness.
A further object is to provide a machine base which is constructed of steel plates for stiffness, but has compartments filled with sand to give adequate damping characteristics.
In the drawing:
FIGURE 1 is an isometric view of my improved machine base with parts broken away; and
FIGURE 2 is a vertical section through the central portion of the base.
In the form illustrated, my machine base includes a top member 10, a pair of longitudinal bottom members 12, a
pair of transverse bottom members 13, a pair of end members 14, and a pair of side plates 15, all of steel plates and bars rigidly welded together. The longitudinal bottom members 12 carry cleats 16 for attaching the base to a suitable substructure (not shown). A conventional machine, such as a milling, drilling, or grinding machine (not shown), is fixed to the top member 10. The size and configuration of the base of course vary with different types of machines.
In accordance with my invention, the base has two compartments 17 which I fill with coarse dry sand or equivalent. Although the configuration of these compartments is not critical, I find it convenient to make them of inverted triangular shape. The compartments illustrated have vertical walls 18 spaced from the ends of the base and sloping walls 19 which extend downwardly from the transverse center line of the top member 10. The side plates 15 and top member 10 form the remaining walls of these compartments. The two sloping walls 19 have access openings which contain plugs 20 for filling the compartments. The sand should be packed tightly in each compartment 17. Optionally I may place the sand under an initial compressive load to assure that it is packed properly. Walls 18 and 19 are relatively thin, and I can pass bolts 21 through these walls and through the compartments to draw the walls together and thus compress the sand.
Any movement of the machine base in bending or torsion distorts the sand compartments and produces frictional forces between the sand particles themselves and between the walls and the sand particles. The friction dissipates energy and results in damping, whereby chatter is eliminated.
From the foregoing description, it is seen that my invention affords an extremely simple construction for preventing chatter in a machine base, yet obtaining the advantages of a welded steel base. The sand-filled compartments are inexpensive to produce and simple to maintain.
While I have shown and described only a single embodiment of my invention, it is apparent that modifications may arise. Therefore, I do not wish to be limited to the disclosure set forth but only by the scope of the appended claims.
1. A machine base comprising a welded steel structure having walls which define compartments, and masses of sand tightly packed in said compartments and fully enclosed by said walls, said walls being relatively movable in bending or torsion to distort the compartments and produce frictional forces between the sand particles themselves and between the walls and sand particles, said friction-al forces dissipating energy and eliminating chatter of a machine mounted on said base.
2. A base as defined in claim 1 in which there are two compartments formed of side plates, vertical walls between said side plates, and sloping walls extending downwardly from the transverse center line of the structure, said sloping walls having access openings for filling the compartments with sand.
3. A base as defined in claim 2 in which said vertical and sloping walls are relatively thin and further comprising bolts extending through the relatively thin walls and through the sand in the compartments to apply an initial compressive load to the sand.
References Cited FOREIGN PATENTS 51,691 12/1941 Netherlands.
ROY D. FRAZIER, Primary Examiner.
F. DOMOTOR, Assistant Examiner.