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Air Engraver Evolution and History
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 to replace the one that came with an old suction pulse engraving machine. These new hand pieces were palm-sized rather than long like the hand piece that came with the 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 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 fatherís 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. NEBRASKAland.pdf  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.


Lindsay AirGravers Evolution from 2000 to present


1.  Working from the designs invented by my father in 1979, an improved self oscillation piston 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 hole.


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 parts.


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 when needed. 

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 one gear.


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 employee 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 tool manufacturer.

For further reading Michael Arternis has written an
informative article titled insight into the patent system

The PalmControl patent 6,691,798 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."

The patented Lindsay PalmControl is by far the simplest, easiest to use engraving device ever made. Barry Lee Hands                                                                            Additional Feedback

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