Tools – Wrench – screwdriver – or driver therefor – Responsive to torque on work
Reexamination Certificate
2000-10-23
2002-09-17
Meislin, D. S. (Department: 3723)
Tools
Wrench, screwdriver, or driver therefor
Responsive to torque on work
C081S009240
Reexamination Certificate
active
06450072
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is generally directed toward manufacturing methods and, more particularly, toward a method and device for setting a tappet screw.
2. Description of Related Art
Tappet clearance is the distance between a bottom surface of an adjustment or tappet screw and an upper surface of a valve. Different methods and devices for setting tappet clearance are known in the art. One such automatic method for setting tappet clearance involves a method of sensing valve movement and controlling a tappet screw setting in response to sensed valve position.
Methods and devices for manually adjusting tappet screws are also known in the art. When using such devices, it is a common practice for an assembler to walk along and manually adjust the tappet clearance as the engine travels on the assembly line. In accordance with one conventional method, the crankshaft/cam is put in the proper angular orientation, and feeler gauges are inserted between the camshaft and the rocker arm. Thereafter, the tappet screw is rotated or adjusted toward the valve to open the valve. This rotation of the tappet screw continues until the valve spring exhibits a biasing force of a predetermined value against the tappet screw. Accordingly, this method requires a device to turn the tappet screw, and such device must react to the biasing force or load such that further rotation of the tappet screw is prevented upon development of the predetermined valve spring force.
With reference to
FIG. 13
, a device
100
used in the aforementioned conventional method is shown to include an inner shaft
102
, an outer sleeve
104
, a bearing block
106
, and a dome-shaped handle
108
. The outer sleeve
104
includes, at a distal end
110
, a nut-receiving socket
112
and, at a proximal end
114
, a T-bar type handle
116
that extends radially in opposite directions.
The inner shaft
102
extends through outer sleeve
104
such that a distal end
118
of the inner shaft
102
has a common-type screwdriver head
120
disposed at an open base of the nut-receiving socket
112
. The opposite or proximal end
122
of the inner shaft
102
projects outwardly from the proximal end
114
of the outer sleeve
104
. Near the proximal end
122
, the inner shaft
102
includes a first radially enlarged area to which the proximal end
114
of the outer sleeve
104
is secured, and a second radially enlarged area
126
to which a handle base
128
is secured.
A detent plate
130
is secured adjacent the second radially enlarged area
126
and the inner shaft proximal end
122
. The detent plate is affixed to the inner shaft
102
and is essentially captured between the handle base
128
and the bearing block
106
. The detent plate
130
includes a series of detents or recesses
132
, which are adapted to receive spring-biased balls
134
that are secured in the bearing block
106
. The proximal end
122
of the inner shaft
102
defines a longitudinally-extending mounting portion that the bearing block
106
is secured over.
The bearing block
106
provides a center passage that accommodates first and second bearings
137
. The bearings
137
rotatably receive the mounting portion of the inner shaft proximal end
122
. The dome-shaped handle
108
is affixed over the bearing block
106
for grasping and rotation thereof by the user. The balls
134
are secured in a face or surface at a first end of the bearing block
106
.
The balls
134
are biased by springs
136
in a direction away from the bearing block
106
and toward the distal ends of the outer and inner shafts. The balls
134
are received in the detents
132
provided by the detent plate
130
. The engagement between the balls
134
and the detent plate
130
serves as the driving connection between the bearing block/handle and the inner shaft
102
. The level of spring bias is adjustable by, for example, adjustment screws
138
.
Accordingly, with the device illustrated in
FIG. 13
, and with reference to the valve actuation system illustrated in
FIG. 1
, rotation of the tappet screw is accomplished by rotating the handle
108
. The tappet screw engages the valve and forces the valve stem toward the engine cylinder against the bias of the valve spring. When the force of the valve spring reaches a predetermined desired level (i.e., the load on the inner shaft), the biasing force of the spring-loaded balls is overcome, and the balls
134
slip from the detents
132
, giving the worker tactile and aural feedback that the desired pre-load has been accomplished.
Unfortunately, rotation of the handle
108
past the point wherein the balls
134
initially slip from the detents
132
, causes the balls
134
to quickly and repeatedly seat into the detents and unseat from the detents. The repeated engagement/disengagement of the balls with the detents is believed to cause the screwdriver to be further rotated or driven, and thus over-driven. This belief is based upon the fact that use of the device illustrated in
FIG. 13
has created inconsistent and non-repeatable results.
Therefore, there exists a need in the art for a device to overcome or minimize the deficiencies in the art and properly set the tappet screw. Accordingly, there exists a need in the art for a device for manually setting tappet clearance that will have repeatable, consistent results. There also exists a need in the art for a method for manually setting tappet clearance or preload.
SUMMARY OF THE INVENTION
The present invention is directed toward removing or minimizing the above-noted problems in the art and toward providing an improved method and device for setting tappet screw clearance. The present invention is further directed toward an improved method and device for manually setting tappet clearance or preload that will have repeatable, consistent results.
In accordance with the present invention, a tappet screw adjusting device includes an outer sleeve, an inner shaft, a bearing block, a handle, and a load-responsive assembly between the bearing block and the inner shaft. The load-responsive assembly is designed such that, when the load on the inner shaft is below a predetermined level the bearing block and the said inner shaft are coupled for common rotation. Alternatively, when the load on the inner shaft is above the predetermined level, the bearing block is rotated while the inner shaft remains stationary.
In further accordance with the present invention, the load-responsive assembly includes a friction plate and a tension setting device. The tension setting device is coupled to the bearing block while the friction plate is in frictional contact with a member that rotates with the inner shaft.
In further accordance with the present invention, the friction plate serves as a frictional coupling between the inner shaft and the tension setting device. The tension setting device is threadably secured to the bearing block, and the friction plate includes a projection that is received in a groove in the tension setting device. Therefore, rotary motion of the tension adjusting device is translated into axial movement of the friction plate.
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Ciamacco Vincent
Honda of America Mfg. Inc.
McDonald Alan T.
Meislin D. S.
Rankin, Hill Porter & Clark LLP
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