Metal working – Means to assemble or disassemble – With means to test work or product
Reexamination Certificate
2002-12-10
2004-06-29
Bryant, David P. (Department: 3726)
Metal working
Means to assemble or disassemble
With means to test work or product
C029S709000, C029S714000, C029S718000, C029S407050, C029S407100, C073S865800
Reexamination Certificate
active
06754948
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to systems for verifying quality control, and more particularly, to a system that ensures that a part or assembly is pressed to depth within a predetermined tolerance and measurement accuracy, and that determines the quality of the interference fit.
2. Description of the Related Art
In current pressing applications it is difficult or impossible to determine whether a pressed-in part has been pressed to a fully seated condition when the operation is complete. Current systems endeavor to ensure that a pressed-in part is fully seated by monitoring the press force and continuing the operation until a predetermined amount of force is applied. This predetermined amount of force is assumed to insure that the pressed part is driven to a full seating position, and that the force applied is representative of the quality of the interference fit. These assumptions, however, are not always correct. The force required to overcome the interference fit in the pressing operation oftentimes exceeds the preset force limit of this known approach. Sometimes, a particle of dirt or metal will become lodged behind the part that is being pressed, causing a false reading on the press force. Thus, the application of the full measure of the predetermined force will not always result in complete inward displacement and seating of the part desired to be pressed into place.
A second current method of verifying press quality is to measure the depth of press at the press ram head. Unfortunately due to part and casting variations this simple single-measurement system is inadequate, as it will not identify the quality of a precision pressing operation.
In the case of a valve seat in an engine head, or a bearing cup in an assembly, the normal working forces, vibration, and heat of the product will finally seat the incorrectly assembled part during the engine or component's normal working life. This form of seating action, however, will generally cause changes in the running clearances of the assembly that are critical to the product's over all life or performance
In addition to the foregoing, valve seats in particular are subjected to tremendous amounts of heat from exhaust gasses. Often times, the temperature of the exhaust gas approaches the melting point of some metals. It is essential that proper seating of the valve seat within the receiving pocket be effected to promote transference of the heat to the cylinder head casting, which contains the cooling water jackets.
There is a need, therefore, for a quality monitoring system that overcomes the foregoing problems.
It is, therefore, an object of this invention to provide a system for pressing-in a press-fit part, such as a valve seat or bearing cup, into a receiving pocket in a receiving assembly, such as a cylinder head, that achieves seating of the part to a predetermined depth reliably.
It is another object of this invention to provide a system for pressing-in a press-fit part to achieve seating within predetermined tolerances without applying excessive continuous insertion force.
It is also an object of this invention to provide a self-aligning press fit ram.
It is a further object of this invention to provide a system for pressing-in a press-fit part to achieve verified seating within predetermined tolerances.
It is additionally an object of this invention to provide a system for pressing-in a press-fit part, such as a valve seat or bearing cup, into a receiving pocket in a receiving assembly, such as a cylinder head, that achieves seating of the part to a predetermined depth reliably, notwithstanding variations in dimensions of the press-fit part
It is yet a further object of this invention to provide a system for pressing-in a press-fit part, such as a valve seat or bearing cup, into a receiving pocket in a receiving assembly, such as a cylinder head, that achieves seating of the part to a predetermined depth reliably, notwithstanding variations in depth of the receiving pocket.
It is also another object of this invention to provide a system for pressing-in a press-fit part into a receiving pocket in a receiving assembly wherein the insertion force is monitored.
SUMMARY OF THE INVENTION
The invention will be shown in one embodiment to be applied to pressing valve seats for an engine head. Bearing cups or any other precision pressing operation could use the same technology.
The foregoing and other objects are achieved by this invention which provides, in accordance with a first method aspect thereof, a method of verifying the quality of a pressing operation of a press-fit part onto a receiving portion of a receiving assembly. The method includes the steps of:
first measuring a predetermined dimension of the press-fit part to establish a first measurement value,
directing a first measuring probe to the receiving portion of the receiving assembly onto which the press-fit part is to be pressed;
second measuring the receiving portion of the receiving assembly onto which the press-fit part is to be pressed, to establish a second measurement value,
urging the press-fit part onto the receiving portion of the receiving assembly;
third measuring a portion of the receiving portion of the receiving assembly that extends beyond a predetermined surface of the press-fit part to establish a third measurement value,
first comparing the third measurement value against the difference between the first and second measurement values to form a first comparison value; and
second comparing the first comparison value against a predetermined comparison value to determine the quality of the pressing operation.
In one embodiment of this method aspect of the invention, the receiving portion of the receiving assembly onto which the press-fit part is to be pressed is a pocket of the receiving assembly. The pocket has a depth that is defined by the distance between outer and inner surfaces thereof. Moreover, the step of directing a first measuring probe to a receiving portion of the receiving assembly onto which the press-fit part is to be pressed includes the step of causing the first measuring probe to travel toward and communicate with the inner surface. In a further embodiment, there is further provided the step of second directing a second measuring probe to the outer surface of the pocket of the receiving assembly. The step of second measuring incorporates the step of differential measuring a difference in the respective distances traveled by the first and second measuring probes during the respective steps of first and second directing. Such differential measuring provides an indication of the depth of the pocket of the receiving assembly. In other embodiments, however, where a press-fit part is installed on a shaft, the receiving portion of the shaft is measured, in either case, the step of differential measuring incorporates the step of monitoring an electrical signal characteristic provided by a linear variable differential transformer (LVDT), or other measuring device, such as a laser.
In a further embodiment of this first method aspect of the invention, the step of urging the press-fit part into the pocket of the receiving assembly incorporates the further step of translating a ram element in communication with the press-fit part toward the pocket of the receiving assembly. Also, the step of translating a press rain element includes the further step of permitting an angular displacement of the press-fit part with respect to the pocket of the receiving assembly. In this manner, a plane of the press-fit part is made substantially parallel to a plane of the predetermined inner surface of the pocket of the receiving assembly.
In a still further embodiment of this first method aspect of the invention, the step of urging the press-fit part into the pocket of the receiving assembly includes the further step of measuring an insertion force of the press-fit part into the pocket of the receiving assembly to establish an insertion force value over a predetermined insertion distance. Thi
Juranitch James C.
Olschefski Robert D.
Bryant David P.
Cozart Jermie E.
Rohm & Monsanto, PLC
Veri-Tek International Corp.
LandOfFree
Press operation verification system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Press operation verification system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Press operation verification system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3324064