Air Engraver Evolution and
by Steve Lindsay
In 1977, I entered college with a major in Tool and Die and Mechanical Engineering. While there, I
had the opportunity to create several new hand pieces for the worlds first
pneumatic engraver the gravermister invented by my father's friend John Rohner to replace
the original one. These new hand pieces were
palm-sized rather than long like the hand piece
that came with
John's original invented machine.
This was beneficial for smaller detailed engraving as well as providing
improved control. Then in 1979, my father made an electronic circuit to
oscillate and adjust the speed of a solenoid valve. Air was run through this
valve to produced blow-pulses rather than suction-pulses. My father (Frank W.
Lindsay, watchmaker / & jeweler) and I built
numerous hand pieces for this adjustable positive pulse generator, and I used
that machine for my work up to 1999. In an interview for the December, 1981 NebraskaLand magazine,
my father’s machine was mentioned and a picture of it can be seen on the back
corner of the engraving bench on page five of the article.
It is the gray box in the right back corner of the bench.
Left: Picture of three handpieces made in 1979 for my father's machine.
1. Working from the designs invented by my father in 1979,
an improved self oscillation piston principle was patented in 2000.
It can operate with very little air pressure or air volume. In fact, by simply
blowing in it or attaching it to a toy balloon, the tool will idle. Instead of a
spring for the return or impact stroke, the device uses air pressure for both
directions. As a result, the piston always stays balanced and low or high air
pressures can be used without one side overpowering the other causing the piston
to float, which can occur with the spring-pulse designs. The patented idle of
the new design prevents jumps that sometimes occur with spring-pulse designs.
The stroke length and speed adjustment is in the bore of tool. Adjustment is
made by removing the graver and adjusting the screw at the bottom of the tool
2. A multiple controller box is shown above. Since this box required a lot of work to
manufacture, it was replaced by using either a simple toggle-routing valve on the current foot controller setup, or quick disconnects. This development allows as many
hand pieces and rotaries as needed to be operated at the same time. The basic principle of the controller for the tool was patented.
3. One way to move the length-of-stroke adjustment to the outside of the hand
piece was the ring pictured above. Only one of these was made as a prototype and
it was patented when the snap on/off handle was patented. The tool worked nicely,
but it was difficult to make and assemble because of all the small internal
4. In the design shown above, stroke adjustment was still in the tool hole, but
the addition of the black rings around the body made it possible to adjust the
exhaust by turning the ring. When a stroke adjustment was made, the exhaust
could also be tuned to make them run even better.
The stroke adjustment on the tools makes one hand piece as versatile as a
variety of different-sized hand pieces.
5. I eventually discovered and patented a way to adjust the stroke by moving the nose in and out with a
ring around the body, while simultaneously adjusting (tuning) the exhaust.
Synchronizing the two made the tool run well throughout the stroke range,
without having to adjust one and then the other. The ring works in a manner
similar to focusing a lens on a camera. Because of the way the nose is held in
place, the impacts are isolated to the nose and graver shank. This leads to less
vibration to the body during impacting, and provides significantly more power
The stroke adjustment is similar to gears in a car and makes the tool perform like numerous handpieces in
one. First gear is good for shading and fifth gear is good for background. If thinking about it this way, the past blow-pulse machines similar to my father's machine has
6. The development of the PalmControl meant the
elimination of the foot pedal. I noticed that while engraving with a foot pedal,
engravers also vary the pressure used to hold the graver point in a cut.
Depending on the depth, engravers vary the amount of palm pressure. This idea
was built upon by making a handle that would automatically respond to the palm
pressure to operate the throttle. The concept for the PalmControl was: why do we
have to duplicate with a foot pedal what our hand is already doing? It was also patented. The legal enforceable claims of the patent protect a hand push pressure activated power tool used in the
hand engraving and jewelry fields.
Note: Comments were made by an owner of a competitor that the Lindsay
PalmControl is nothing new. However, the PalmControl technology had not been described or illustrated in a dated public magazine or book one year prior
(June 19, 2001) or any time prior to the priority date of the patent, that anyone or the patent and trademark office is aware of. A publication such as this is termed
proof of valid prior art. The patent issued only after thorough examination by the United States Patent Office, which courts consider the foremost experts in determining
novelty, obviousness, etc. If the engraving world had known of the abilities of this engraving technology, have no doubt that it would have been exploited long ago by a
For further reading Michael Arternis has written an
informative article titled insight into the patent system
The PalmControl patent protects a hand push pressure activated power tool used in the hand engraving and jewelry
fields as described in one of the legal claims of patent that is provided below. Infringement of the claims of this patent or any of the Lindsay patents by competitor
tool manufactures will be taken seriously.
"A hand-held power tool for use in hand working operations in the hand engraving and jewelry fields, comprising: a body having first and second ends; a tool tip holder
located at said first end for holding a tool tip; a handle made to be held in the human hand on said body; a variable power means for delivering variable power to said
tool tip; a pressure sensing means for sensing the amount of pressure exerted by a human hand between said handle and said tool tip; said variable power means will
increase in power when said pressure sensing means senses increased pressure exerted by the user of said hand-held power tool on said handle with the human hand; and
said variable power means will decrease in power when said pressure sensing means senses decreased pressure exerted by the user of said hand-held power tool on said
handle with the human hand."