Patent Grant
10926577
The subject matter of the present application is in the field of powered impact-type engraving tools and their control systems, typically used by jewelers for fine engraving work.
Impact-type engraving tools or “gravers” are well known for use by jewelers when doing fine work on jewelry. Gravers typically have a hollow handle or grip supporting a hardened adjustable tip impacted by an internal piston. The most common type of graver is pneumatically-operated, where the tip is placed against a workpiece and air is pulsed into the handle from an exterior source, driving the piston to strike the tip (or an anvil contacting the tip) to remove material from the workpiece. One such pneumatic graver tool is shown in my U.S. Pat. No. 9,079,286.
Controlling the speed and force of the graver stroke is important for control over the engraving work. A common type of control system for driving pneumatic gravers uses a control box with valves and a controller for regulating the delivery of air to the graver from a pressure source. The control box is typically activated with a foot pedal connected to the box via an air conduit. Two such pedal-operated pneumatic graver control box systems are shown in U.S. Pat. No. 4,903,784 to Glaser and U.S. Pat. No. 7,762,347 to Glaser et al.
Precise, repeatable, controlled piston strokes with good “feel” are of critical importance to skilled jewelers and engravers. While prior pneumatic graver systems have attempted to provide better control over piston force and speed in various ways, there is significant room for improvement.
One approach has been to replace the pneumatic motive force in an engraving device with an electric one, via a solenoid electromagnetically driving the piston.
One solenoid-driven engraving device is shown in Chinese patent publication CN 2706338Y. This appears to be a basic handheld impact engraving tool, apparently for use in “eagle pecking” type carving in place of traditional chisel tools, with the stated advantages of reduced wear on the tool and a higher degree of repeatability and consistency imparted to the chisel stroke.
Another solenoid-driven engraving tool is shown in Chinese patent publication CN 204309491U, apparently designed for stone carving or surfacing, wherein an internal shock absorbing system and an adjustable cap associated with needle or tip are presumed to ensure a consistent impact on the stone's surface.
Prior solenoid-based gravers such as the above appear to be fairly simple, designed for basic engraving or carving techniques in inexpensive materials, and it is believed that they would not provide the “feel” and control desired by a jeweler for truly fine work on more expensive materials. It is also believed that these prior solenoid engravers would get too hot to handle with prolonged use, and would not be useful for fine engraving in which a curl of metal is removed from the workpiece with a push-like force imparted by the tool as a whole, versus a dot- or stippling-type action which displaces rather than removes the material.
The present invention is a handheld solenoid-driven graver, and an associated control system and method, to provide the fine feel and control over the piston stroke prized by jewelers.
The handheld graver comprises a fixed-position graver tip held in a heat-conductive forward stylus tube, and a hollow rear handle section made from a heat-insulating material like plastic or wood. A push-type solenoid unit is mounted in the hollow handle, with a “piston” or plunger (hereafter plunger) reciprocating in a solenoid tube or housing and connected to an actuator rod extending through a forward interface end of the solenoid to selectively strike an anvil or base portion of the graver tip in the stylus tube. The forward interface end of the solenoid is connected to the stylus tube with a heat sink connection, for example a threaded metal-to-metal connection, while an insulating air gap spaces the insulating wall of the handle section from the remainder of the solenoid housing rearwardly of the heat sink connection, except for a rear insulating connection between a rear portion of the insulating handle material and a rear portion of the solenoid tube or housing.
The hollow handle further includes air flow holes adjacent the forward interface end of the solenoid unit, the holes communicating with the insulating air gap between the handle and solenoid to permit ambient air to flow over the heat sink connection and to the interior of the grip around the solenoid housing.
An adjustable backstroke stop is located at the rear of the handle section, to adjust the stroke of the plunger.
The control system for the handheld graver includes a foot pedal, the pedal communicating with the handheld graver to supply electrical power to the solenoid in the graver to control the plunger stroke. The foot pedal in a preferred form includes a potentiometer or optical input sensor to the control system which dynamically supplies power in a controlled gradient to the solenoid driver, allowing smooth adjustment of plunger force and speed. The control pedal is configured with a unique pedal input range, from a physically limited neutral or no-power position inclined toward the user, through a flat mid-range position, to a physically limited maximum deflection position inclined away from the user. The pedal response is set with adjustable dead zones at minimum and maximum, i.e. where a pre-set degree of motion at either end of the pedal's range is calibrated by a controller to result in no change to the solenoid's operation.
The control system for the handheld graver includes a foot pedal. The pedal is the primary user input to the control system that maps the user input to a variety of electrically driven pulse forms which supplies electrical power to the solenoid in the graver to control the plunger stroke. The foot pedal in a preferred form includes either a potentiometer as the angle sensor or an optical sensor to provide the input signal to the control system over a wide physical range as to provide a controlled gradient to the solenoid driver, allowing smooth adjustment of plunger force and speed and increased controllability for the user. The control pedal is configured with a unique pedal input range, from a physically limited neutral or no-power position inclined toward the user, through a flat mid-range position, to a physically limited maximum deflection position inclined away from the user. The pedal response is set with adjustable dead zones at minimum and maximum, i.e. where a pre-set degree of motion at either end of the pedal's range is calibrated by a controller to result in no change to the solenoid's operation.
The control system in a further form includes a controller connected to (or incorporated in) the foot pedal for adjusting the response of the pedal; for optimizing the “duty cycle” or pulse width of the solenoid with a fixed frequency; for mapping pedal input to solenoid pulse rate, pulse train, and/or pattern; for mapping pedal input to an increasing frequency with a fixed pulse width; and for providing a soft start option in which the solenoid is activated to reciprocate in the handheld graver without striking the graver tip, providing an audible and tactile signal to the user that the graver tip is about to begin removing material from the workpiece.
In a further form, the invention includes a method of optimizing a solenoid pulse rate in a handheld graver controlled by a foot pedal, where solenoid pulse rate is mapped to pedal deflection in non-linear fashion over the pedal deflection range. In still a further form, the method of optimizing includes adjusting both pulse length and/or rate to provide “burst” and “train” patterns of pulses.
In a further form, the invention includes a method of optimizing various solenoid pulse effects in a handheld graver controlled by a foot pedal, where these effects are mapped to pedal deflection in a user selectable linear and non-linear fashion over the pedal deflection range. In still a further form, the method of optimizing includes adjusting both pulse length, pulse frequency, and combinations thereof, to provide “burst” and “train” patterns of pulses.
These and other features and advantages of the invention will become apparent from the detailed description below, in light of the accompanying drawings.
Referring first to
Stylus tube 12 supports a known type of graver tip 16 made from a material such as tungsten carbide or hardened steel, the graver tip fixed in an anvil 18 which in turn is fixed in the outer end of stylus tube 12 in known manner. A strike to the base 18b of anvil 18 accordingly exerts a forward force on graver 10 as a whole, which then shifts forward to move graver tip 16 into and through the material being engraved.
The hollow interior of handle 14 contains a solenoid unit 20 of generally known type, in the illustrated example a commercially available push-type solenoid unit having a solenoid tube or housing 22, a plunger bore 24, a plunger 26 capable of reciprocating back and forth in the plunger bore 24, an actuator or push rod 28 extending through a rod bore 24a formed in a forward end 22a of the solenoid tube 22, a magnet coil 30 encapsulated at 32 in an outer housing 34 around the solenoid tube 22, and an electrical power connector 36 for receiving electrical power to selectively energize the coil 30. A return spring 38 is located between the forward end of plunger 26 and a forward end 22a of the solenoid tube, normally urging plunger 26 rearwardly to a de-energized position in the plunger bore.
The forward end of the solenoid has a plug-like stylus connection interface portion 40, either integrally formed with the solenoid or added thereto, comprising external threads 42 screwed into matching internal threads 12a in the rear of the stylus tube in a heat conductive metal-to-metal fit. Stylus connection interface 40 also includes an array of heat sink fins 44, in the example a circular array of axially spaced fins, located behind the connection threads 42. While a threaded metal-to-metal connection is illustrated and preferred between the forward end of the solenoid and the stylus tube, other types of heat-conductive metal-to-metal connections would be possible.
The rear end of solenoid unit 20 is attached to graver 10 at a rearmost portion 114 of handle 14, which may comprise the sole or at least the primary connection between the handle and the metal solenoid unit. For example, the rear end of solenoid tube 22 is formed as an open cylinder, or has its original end closure removed, and is closed off with a length-adjustable backstroke stop 50 threaded at 51 into threads 122a formed in the rear end of the solenoid tube bore. An inner plug portion 52 of backstroke stop 50 extends partway into solenoid tube 22 to provide a backstop, limiting the rearward motion of plunger 26 in bore 24. Backstroke stop 50 can be threaded into the rear of handle 14 partway or fully, thereby adjusting the “stroke” or length of travel of solenoid plunger 26 according to the length/extent of the threaded connection between backstroke stop 50 and solenoid tube 22 or handle 14.
Backstroke stop 50 is made from a heat insulating material such as wood or plastic, similar to handle 14, in order to minimize heat transfer from the metal body of solenoid tube 22 to the handle. Thus the only metal-to-metal contact between the solenoid unit 20 and the graver is at the forward threaded stylus interface connection 42, 12a.
To further insulate the exterior of handle 14 from heat generated by the solenoid, the remainder of the handle between stylus interface connection 40 and rear backstroke stop 50 is spaced from the solenoid unit by an air gap 60 that extends around the exterior of the solenoid unit. Airflow holes 62 and 64 are formed in the forward and rearward ends of handle 14, allowing cooling air to flow through the handle around the solenoid unit. Forward air holes 62 are in close proximity to heat sink fins 44, allowing cooling air to flow in over the fins to remove heat from the fins. The air is exhausted through rear air holes 64 by convection, as the graver is often held at various angles and such that a chimney effect from one set of air holes to the other is created through the handle. Fins 44 are preferably spaced from contact with the inner surface of handle 14 for better air flow.
The solenoid plunger may be driven into contact with the anvil by either attracting or repelling the plunger forward against the return spring, depending on the preferred coil arrangement.
The frequency and duration of electrical current applied to the solenoid determines the duty cycle, which is the ratio of the solenoid ON time to the total of its ON plus OFF time for one complete cycle of operation, i.e. one strike in which the plunger moves fully forward to strike the anvil and then returns. Controlling the duty cycle and other pulse effects by controlling the electrical current intermittently delivered to the solenoid is critical for very fine control over the “feel” of the graving operation.
Referring now to
Controller 200 may comprise, for example, a known type of programmable electronic controller or discrete microprocessor circuit, with functional modules including power processing, sensor processing, microprocessor based operation, display and configuration menu, and solenoid drive stage as schematically shown in
The primary function of the controller 200 is to drive the solenoid 20 in graver 10 with variable pulse or duty cycle characteristics. This may include providing the controller with a drive stage having a cascade MOSFET driven gate stage 226 supplied by the above-described large capacitor bank 232, although a simpler, higher-amperage power supply of equivalent voltage could be used instead.
Regardless of voltage, power variations are essentially controlled by active ON time, and controller 200 can be programmed according to the invention for a pulse “train” mode in which the frequency measures the time between single regularly-spaced pulses (
The microprocessor has internal analog to digital converters to sample power levels and the primary sensor input (the pedal). Once read, the sensor voltage level, now a number in an internal register, is first scaled to incorporate a low end dead zone, linear input range, and an upper end max zone and maintained as the processed input 244. Once this is characterized, the relative input is read by mode specific routines 242 and mapped within that routine to a series of outputs based on the settings previously configured by the user. The mapping routines 246 combine the processed input 244 with numerous settings. After the mapping conversion is complete, each mode generates its own output pulse pattern 248 according to the selections for that mode as entered by the user. For example in the pulse width mode with fixed frequency pictured in
Referring now to
In the illustrated example of
The pedal input sensor may comprise various known electromechanical or electronic means for sending a signal to the controller proportional to footplate rotation. In the illustrated example, the pedal input sensor 310 is a non-contact IR (infrared) reflective element 310a of known type in either the footplate 302 or base 304, the reflective element 310a optically coupled to an IR emitter/receiver 310b of known type in the opposing pedal member which generates a signal proportional to the distance between the reflector and emitter/receiver and delivers the signal via connection 250 to the controller 200. The opto-electronic nature of this preferred pedal input sensor arrangement eliminates mechanical features that can stick, wear, or malfunction. A potentiometer can also be used, as is common in the industry.
Still referring to
Referring now to
Referring now to
Referring now to
In
Referring again to
It will finally be understood that the disclosed embodiments represent presently preferred examples of how to make and use the invention, but are intended to enable rather than limit the invention. Variations and modifications of the illustrated examples in the foregoing written specification and drawings may be possible without departing from the scope of the invention. It should further be understood that to the extent the term “invention” is used in the written specification, it is not to be construed as a limiting term as to number of claimed or disclosed inventions or discoveries or the scope of any such invention or discovery, but as a term which has long been conveniently and widely used to describe new and useful improvements in science and the useful arts. The scope of the invention supported by the above disclosure should accordingly be construed within the scope of what it teaches and suggests to those skilled in the art, and within the scope of any claims that the above disclosure supports in this application or in any other application claiming priority to this application.
This application claims the benefit of U.S. Provisional Application No. 62/557,941, filed Sep. 13, 2017 by the same inventors (DeCamillis and Johnson), the entirety of which provisional application is hereby incorporated by reference.
| Number | Name | Date | Kind |
|---|---|---|---|
| 3201670 | Myers | Aug 1965 | A |
| 4903784 | Glaser | Feb 1990 | A |
| 7762347 | Glaser et al. | Jul 2010 | B2 |
| 9079286 | DeCamillis | Jul 2015 | B1 |
| Number | Date | Country |
|---|---|---|
| 2706338 | Jun 2005 | CN |
| 204309491 | May 2015 | CN |
| Number | Date | Country | |
|---|---|---|---|
| 62557941 | Sep 2017 | US |
