Line transfer system with a contour machining head

Details Line transfer system with a contour machining head Line transfer system with a contour machining head

2002-07-22

2003-11-04

Vidovich, Gregory (Department: 3726)

Metal working

Method of mechanical manufacture

With testing or indicating

C029S888440, C408S0010BD, C408S082000, C408S083500, C408S143000, C409S141000, C074S573110

Reexamination Certificate

active

06640410

ABSTRACT:

FIELD OF THE INVENTION
The invention is directed generally to machinery, and more particularly to a line transfer system with a contour machining head.
BACKGROUND OF THE INVENTION
Machining of materials to create openings or recesses of different shapes is used in the manufacture and repair of a wide range of objects. In applications where the dimensional tolerances, roundness and smoothness of the machined surface are important, special tools are often required, especially when the material to be machined is very hard or otherwise difficult to machine. For example, transfer machines within an automated manufacturing line often require multiple machining heads with a variety of different cutting bits to form rounded openings of the desired profiles. The more different machining heads required in a transfer machine, the more complex the machine becomes, and the more floor space it requires. As an alternative to multiple machining heads, a single cutting machine can be adapted to receive a variety of different cutting bits. However, when the cutting bit needs to be changed, the processing line must be paused or shut down, resulting in reduced throughput.
In an exemplary application, such cutting tools are used in the repair of the cylinders heads of internal combustion engines to re-establish the high quality seal required for efficient engine performance and fuel consumption. It is well known among vehicle mechanics that valve seats can be machined to remove the outer surface of the seat to expose a smooth and uniform contact surface by a technique commonly referred to as “lapping”. This lapping technique is accomplished by removing the cylinder head from the engine and machining the valve seats with a cutting blade. Typically, a valve seat has a profile with three different angles: a throat angle, a valve seat angle, and a top angle. In order to simultaneously cut the different angles, a “three-angle” cutting blade or bit is used. Each cutting edge of the three-angle cutting bit corresponds to one of the valve seat angles to be machined. Three-angle cutting bits vary in size and shape depending on the type of cylinder head valve seat being machined. These three-angle cutting bits are currently used by valve seat and guide manufacturers.
A disadvantage of the lapping technique is the risk of damage to the surface finish from vibration, chattering, or undulation generated by flexion of the cutting bits. This problem develops because certain cylinder head valve seat shapes require a three-angle cutting bit with a long cutting edge. Rotation of this long cutting edge when the edge is in contact with the work surface can create flexions in the cutting bit, especially when the material is difficult to machine, i.e., a very hard material. These flexions generate vibrations, chattering, or undulations which can disrupt contact between the cutting edge and the surface being cut. The skipping blade can damage the surface finish of the valve seat resulting in a machined valve seat that is not acceptable by Original Equipment Manufacturer (OEM) standards.
Another disadvantage of the lapping technique is a decentering phenomena. As stated above, cutting efforts with a long cutting edge/surface create flexions. These flexions create an unbalanced radial cutting effort which decenters the three-angle cutting blade, also resulting in unacceptable quality.
Still another disadvantage of the lapping technique is the large number of three-angle cutting blades needed to machine different types of valve seats. Each type of engine has a different valve seat profile. Thus, one or more unique three-angle cutting blades may be needed for each type of engine.
Finally, many conventional cutting machines operate at high rotational speeds with numerous moving parts. Numerous moving parts rotating at high speeds can cause weight imbalances within a conventional cutting machine, adversely affecting the stability of the cutting machine and potentially affecting the precision cutting operations of the cutting machine. Thus, there is a need for a precision cutting machine that can operate at high rotational speeds while compensating for the weight of its numerous moving parts.
Furthermore, conventional cutting machines lack the capability to perform a variety and wide range of cutting operations needed to simultaneously form complex lines and shapes in one or more workpieces in a relatively efficient manner. Thus, there is a need for a precision cutting machine that can be adjusted to perform a variety and wide range of cutting operations needed to simultaneously form complex lines and shapes in one or more workpieces in a relatively efficient manner.
Moreover, in a conventional cutting machine, a pilot may be used to guide or center a cutting blade or tip with respect to the workpiece. For example, a pilot can be inserted into a valve guide in order to align the bit tool with the valve seat to be machined. When needed, the pilot may be changed by an operator according to the size or configuration of the workpiece to be machined. In some instances, a pilot is secured to the cutting machine by a deformable hydraulic sleeve system. A screw actuated by an operator pushes a piston which, in turn, compresses oil trapped in a chamber. The chamber includes a membrane sleeve that surrounds and wraps around the pilot shank. As the oil pressure increases in the membrane sleeve, the pressure applies inward compression on the pilot shank from all directions, firmly holding the pilot shank in place. To change the pilot, the screw must be manually loosened to relieve the pressure in the membrane sleeve, and then the pilot can be removed. However, replacing the pilot in a conventional cutting machine can be rather difficult and time consuming since the screw must be manually adjusted by an operator to properly tension and untension the screw to secure and release the pilot. In some instances, the operator may fail to properly tension or untension the screw to secure or release the pilot, thus wasting time. Therefore, a need exists for a cutting machine with an apparatus that permits a pilot to be changed in an efficient manner.
Further, in a cutting operation with a conventional cutting machine, the insertion of a pilot within a valve guide or other guide bore is typically a manually performed operation. For example, usually an operator of a cutting machine visually locates a valve guide, and then manually aligns the pilot of the cutting machine with the valve guide. When the pilot and valve guide are aligned, the operator manually lowers and inserts the pilot into the valve guide prior to machining the workpiece. This manually performed operation can be time consuming and inefficient for operators if the alignment is not properly performed the first time, or if the operator lacks coordination, experience or skill in aligning a pilot with a valve guide or other guide bore.
In the case of a fully automated (numerically controlled axis), i.e. a machine with all the movements of the head controlled by motors, the automated insertion of the pilot within valve guides or other guide bores presents other difficulties. For example, in order to insert a pilot within a valve guide, the pilot must be aligned precisely with the valve guide, with a precision leveling device within a micron tolerance, both in the x and y axes. When the machining head of the cutting machine is moved manually by an operator who can visually locate the valve guide, the alignment occurs naturally, “by itself”, since the machining head is free to align itself with the pilot. However, in the case of automated movement, the system controller and motors do not know where, exactly, the valve guide is located. This problem is compounded by the fact that the positioning tolerance of a valve guide in a cylinder head is typically within 0.1 mm or less. Other valve guides or guide bores tolerances will have similar requirements.
Once the tip of the pilot has been engaged within the valve guide, it is critical to be able to continue the downward movement to insert the p

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