Geometrical instruments – Gauge – Circular size
Reexamination Certificate
2000-03-24
2001-10-09
Gibson, Randy W. (Department: 2859)
Geometrical instruments
Gauge
Circular size
C033S555300
Reexamination Certificate
active
06298571
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an apparatus for checking the diameter of crankpins rotating with an orbital motion about a geometrical axis, in the course of the machining in a numerical control grinding machine including a worktable, defining said geometrical axis, and a grinding-wheel slide with a reference device for cooperating with the crankpin to be checked, a measuring device, movable with the reference device, and a support device for supporting the reference device and the measuring device, the support device having a support element, a first coupling element coupled to the support element so as to rotate about a first axis of rotation parallel to said geometrical axis, and a second coupling element carrying the reference device and coupled, in a movable way, to the first coupling element.
BACKGROUND ART
U.S. Pat. No. 4,637,144 discloses an apparatus for checking the diameter of crankpins orbiting about a geometrical axis, in the course of the machining in a grinding machine. The apparatus is supported by a support fixed to the worktable of the grinding machine, or by a support affixed to the bed of the grinding machine, or by a longitudital slide arranged on the worktable.
The apparatus comprises a reference device, Vee-shaped or of another type, for cooperating with the crankpin to be checked, a measuring head fixed to the reference device and provided with two movable arms carrying feelers for contacting diametrically opposite points of the crankpin, a cylinder and piston device, and a coupling device between the cylinder and the support of the apparatus. The reference device is supported by the piston rod and thus is movable along the geometric axis of the cylinder. Moreover, the reference device can rotate, with the cylinder, about an axis of rotation defined by the coupling device and parallel to the geometric axis whereabout the crankpin rotates. The cylinder and piston device comprises a spring, that acts on the piston so as to urge the reference device towards the crankpin to be checked, and a hydraulic or pneumatically actuated device for displacing the piston towards a rest position, in opposition to the force of the spring. In the course of the checking operation, the apparatus is located, with respect to the workpiece, substantially at the opposite side with respect to the one where the grinding wheel is located.
The apparatus and its applications in a grinding machine, described in the formerly mentioned patent, are subject to some inconveniences like considerable layout dimensions, in particular in a transversal direction, high forces of inertia, the impossibility of displacing in an automatic way the reference device from the rest position to the measuring position while the piece (crankshaft) is rotating. These inconveniences are due to both the structure of the apparatus and its application in the machine. All the applications described in the patent involve, in the course of the measurement taking, that the reference device describes a trajectory basically corresponding to the orbital motion of the crankpin.
U.S. Pat. No. 4,351,115 discloses a machine for the dimensional checking of a crankshaft, comprising devices for checking the crankpins in the course of their orbital motion about the main geometrical axis of the crankshaft. Each of these checking devices comprises a guide and reference device, supported by the machine frame, by means of two arms, rotating reciprocally and with respect to the frame, about two axes of rotation parallel to the geometrical axis of the orbital motion. This machine and its associated checking devices are not suitable for checking during the machining operation, among other things owing to the fact that the guide and reference devices describe trajectories that essentially correspond to the orbital motion of the associated crankpin, the speed of the orbital motion is considerably lower with respect to that occurring in the course of the machining in a crankpin grinding machine and the displacement of the checking devices from a rest position to an operating condition occurs when the crankshaft is not rotating.
U.S. Pat. No. 3,386,178 discloses an apparatus, for checking the diameter of cylindrical workpieces, rotating about their geometrical axis, in the course of the machining in a grinding machine. The apparatus comprises two arms, rotating reciprocally and with respect to the grinding-wheel slide. One of the arms supports two reference elements or fixed (with respect to the arm) feelers for contacting the surface of the rotating workpiece and a movable stem, with a feeler for contacting the workpiece and an opposite end for cooperating with the movable element of a clock comparator. The apparatus is manually displaced from a rest position to a measuring condition, and vice versa. The grinding machine cannot machine workpieces rotating with an orbital motion, nor is the measuring apparatus suitable for a similar type of application.
DISCLOSURE OF THE INVENTION
Object of the present invention is to provide an apparatus for the metrological checking of crankpins rotating with an orbital motion, in the course of a grinding operation, or in a similar one, that can provide good metrological performance, high reliability and small forces of inertia. This problem is solved by a measuring apparatus of the hereinbefore mentioned type, wherein the second coupling element is coupled to the first coupling element in such a way as to rotate with respect to it about a second axis of rotation parallel to said geometrical axis, the support element is fixed to the grinding-wheel slide and there are foreseen a guide device, associated with the reference device, for guiding the arrangement of the reference device on the crankpin in the course of the orbital motion and a control device for enabling the apparatus to displace in an automatic way from a rest position to a checking condition, and vice versa.
Preferably, in the rest position, the reference device is arranged substantially above those positions that, in the grinding machine, are assumed by the geometrical axis of the crankpin to be checked and in the course of the displacement towards the operating condition it enters into engagement with the crankpin, guided by the guide device, describing a trajectory with a prevailing vertical component.
Preferably, the reference device is substantially a Vee-shaped device.
Preferably, the guide device defines a shaped guiding surface that is aligned with a surface of the reference device.
According to another characteristic, the control device can be advantageously achieved by means of a double-acting cylinder, for example of the hydraulic type.
According to a further characteristic, the apparatus is made so that, in the operating condition, the reference device rests on the crankpin substantially owing to the forces of gravity, the values of which are appropriately predetermined by a suitable arrangement and entity of the weights of the component parts.
Still further aspects of the invention regard, among other things, manufacturing features for enabling the checking of the diameter of the crankpins while avoiding any interferences with the lubrication holes present in the crankpins and for checking crankshafts with even considerably different nominal dimensions, and safety devices for preventing any collisions or unwanted and/or dangerous motions.
The characteristics of the apparatus and of its application in the grinding machine enable to combine remarkable functionality with relatively low costs and to obtain an arrangement of the apparatus that facilitates the loading and the unloading of the crankshafts and limits the layout dimensions in the areas surrounding the more critical elements of the grinding machine and the accessory devices, like the workpiece loading/unloading devices.
REFERENCES:
patent: 1425283 (1922-08-01), Pratt
patent: 1941456 (1934-01-01), Arnold et al.
patent: 2603043 (1952-07-01), Bontemps
patent: 3157971 (1964-11-01), Snyder
patent: 3274693 (1966-09-01), Witzke
patent: 3321869 (1967-05-01)
Cipriani Riccardo
Dall'Aglio Carlo
Dickstein , Shapiro, Morin & Oshinsky, LLP
Gibson Randy W.
Marpos Societa' per Azioni
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