Patent Grant
7413027
1. Field of the Invention
The present invention relates generally to impact power tools. More specifically, the present invention concerns an impact power tool, such as a pneumatically powered, rotary valve controlled tool, for use in delicate hand working operations, such as detailed, precise, and fine engraving, carving, and stone setting work.
2. Discussion of Prior Art
Delicate hand working operations, such as detailed, precise, and fine engraving, carving, and cutting on metals, woods, stones, and the like, as well as stone setting work require an impact tool that delivers a low impact energy level for each stroke of the tool and that is capable of delivering such low impact strokes at a rapid rate. These problems have previously been identified in U.S. Pat. No. 4,694,912, assigned of record to the assignee of the present invention, issued Sep. 22, 1987 and entitled CONTROLLED IMPACT POWER TOOL (“Glaser '912 patent”) and hereby incorporated by reference herein.
The impact power tool disclosed in the Glaser '912 patent was an advance in the field and solved many of the problems identified in the art at the time. However, it has been determined that engravers and jewelry craftsmen increasingly are desiring to utilize larger hand piece attachments in their impact power tools, such as those capable of advanced carving applications on virtually any type of material, as well as desiring to utilize a wider range of hand pieces on the same impact power tool system for various and wide ranging applications. These desires are not being adequately met with the prior art impact power tools. In fact, craftsman desiring to perform multiple crafting applications that each require a different, wide range of power output must currently utilize multiple impact power tool systems to accomplish their tasks and even then, the combination of systems does not adequately address their desired ranges of power. Current impact power tool systems, particularly the use of multiple systems, undesirably consume valuable and limited inventory space on a craftsman's work bench.
Prior art impact power tools are also subject to other problems and limitations. For example, craftsman desire a crisp, quick, and immediate impact control adjustment. Such response time is simply lacking in prior art impact power tools. This problem is further frustrated by the craftsman's frequent “over-driving” of the tool—for example, when the craftsman is searching for the desired stroke speed or impact energy that is outside of the limits of the prior art tools. Accordingly, there is a need for an improved impact power tool.
The present invention provides an improved impact power tool that does not suffer from the problems and limitations of the prior art impact power tools detailed above. The impact power tool of the present invention provides several advancements, each having advantages over the prior art tools, including an improved housing design and an improved precision controlled drive system that enables greater stroke speeds of a work tool over a wider power range while also improving the crispness and speed of the impact reaction time over the entire range.
A first aspect of the present invention concerns a drive assembly comprising a rotary pulse valve. A central rotor of the valve has an elongated slot that communicates with an elongated slot of a bushing of the valve. When the elongated slots are aligned during rotation of the valve, a faster and more powerful stroke of the work tool is obtained.
A second aspect of the present invention concerns an air storage tank housed within a housing of the impact power tool and operable to store approximately fifty times greater pressurized, regulated air than prior art impact power tools. Quick retrieval of regulated air from the storage tank allows for a constant supply of air to the work tool, improving both low speed impact and high speed response.
A third aspect of the present invention concerns an improved housing of the impact power tool. The housing comprises a plastic, dielectric base plate on which electrical terminals can be connected. Additionally, a cover of the housing comprises a plurality of flat, metal plates and a plurality of beveled rails having channels formed therein. The plates are secured to the beveled rails through use of hex nuts and washers for ease of manufacturing and replacement should threads become stripped.
An embodiment of the impact power tool comprises an air delivery system operable to communicate with a pressurized air source; a drive assembly operable to receive air from the pressurized air source via the air delivery system; a hand held device in driven communication with the drive assembly; and a housing for storage of the air delivery system and drive assembly.
Other aspects and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments and the accompanying drawing figures.
Embodiments of the invention are described in detail below with reference to the attached drawing figures, wherein:
The drawing figures do not limit the present invention to the specific embodiments disclosed and described herein. The drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the preferred embodiment.
The preferred forms of the invention described above are to be used as illustration only and should not be utilized in a limiting sense in interpreting the scope of the present invention. Obvious modifications to the exemplary embodiments, as hereinabove set forth, could be readily made by those skilled in the art without departing from the spirit of the present invention.
The present invention is an impact power tool 10 for use in delicate hand working operations, such as detailed, precise, and fine engraving, carving, and stone setting work. An embodiment of the impact power tool comprises an air delivery system 12 operable to communicate with a pressurized air source (not shown); a drive assembly 16 operable to receive air from the pressurized air source via the air delivery system 12; a hand held device 18 in driven communication with the drive assembly 16 and for performing the delicate hand working operations; and a housing 20 for storage of the air delivery system 12 and drive assembly 16 and defining an interior space 22 and comprising a base plate 24 and cover 26, wherein the cover 26 comprises left and right side panels 28,30, a back panel 32, a front panel 34, and a top panel 36 (see
The air delivery system 12 comprises an air filter 38, an air pressure regulator 40, and an air storage tank 42 in communication with the air regulator 40. The air delivery system 12 is in communication with the pressurized air source (not shown), such as an air compressor operable to provide approximately 45-120 psi of air pressure. As known in the art, a motive fluid may also be used instead of the pressurized air source.
The air filter 38 is any air filter well known in the art and operable to filter air incoming from the pressurized air source. A suitable air filter is sold by SMC Corporation of America of Indianapolis, Ind. under product code AF20-N01-CZ. The air from the pressurized air source is transmitted to the air filter 38 via a source supply line 44, as illustrated in
The air filter 38 is conveniently removably mounted on the right side panel 30 of the housing 20 (see
Once air exits the air filter 38 and is guided through the filter supply line 46, the pressurized air enters the air pressure regulator 40, which regulates the air to a desired pressure. Unregulated pressurized air is usually approximately 35-100 psi and must be scaled down to a smaller pressure for operation with the impact power tool 10. The desired pressure to be achieved by the air pressure regulator 40 will be dependent on the hand held device 18 and the pressure desired for operating it; however, typical operating air pressures range from 8-25 psi. The air pressure may be selectively regulated via an air regulator dial 14 mounted on the front panel 34 of the housing 20. Although the air pressure regulator 40 is operable to regulate the pressure as discussed above, any suitable air pressure regulator may be used, such as the air pressure regulator provided by SMC Corporation of America under product code IR1010-N01, and smaller or larger ranges of air pressure are contemplated by the present invention.
Air exiting the air pressure regulator 40 is moved through a regulator supply line 50 to the air storage tank 42 via a tank inlet 52, as best illustrated in
The air storage tank 42 serves as a storage tank for pressurized, regulated air to allow for faster withdrawal of the air. As pressurized, regulated air is required for operation of the hand held device 18, air is transmitted from the tank outlet 54 and through a tank supply line 76, as best illustrated in
As best illustrated in
The motor 78 is preferably mounted on the base plate 24 via a motor suspension system 92, as illustrated in
The mounting plate 96 is mounted on the plurality of springs 94, which are secured to the base plate 24 and are preferably compressions springs. As can be appreciated, operation of the motor 78 creates a significant amount of vibration. Because the motor 78 is mounted on the mounting plate 96, which is mounted on the springs 94, vibration of the motor 78 results in the springs 94 contracting and extending. As the springs 94 extend, the joined mounting plate 96 and foot plate 104 and are allowed to rise a vertical height that is limited by the plurality of shift stops 102, such that the shift stops 102 act as the maximum vertical limit for the combined plates 96,104. In limiting the vertical height the plates 96, 104 can travel, the movement of the motor 78 is consequently limited, which prevents or lessens normal wear and tear on the motor 78 and lessens the possibility that supply lines and electrical lines will become loose. Thus, the above-described motor suspension system 92 limits the negative effects of a substantial amount of the vibration cause by operation of the motor 78, including limiting wear and tear on the motor and surrounding structure and noise caused by the vibration.
During transport of the impact power tool 10, movement of the motor 78 is not desired, even if limited by the motor suspension system 92 and shift stops 102. Therefore, a locking wing screw and washer combination 109, hereinafter referred to as a shift lock, is provided that can be secured prior to transport and that lock the motor 78 and mounting plate 96 securely to the base plate 24, preventing movement during transport. The shift lock, as illustrated in
As illustrated in
The rotary valve 82 comprises a valve body 122 and a valve bushing 124. As illustrated in
It is expressly noted that although a mechanical rotary valve is described herein, the present invention contemplates use of an electrical or electromechanical valve, such as an electronically fired solenoid valve, that would include the same or similar pulsing features described below. However, use of an electromechanical valve would not require use of the motor 78. Additionally, the pulse cycles described below in the discussion of the rotary valve 82 would still occur, except that the drive assembly would be a linear drive assembly. Thus, the electromechanical valve would still be operable to produce alternating intake and exhaust cycles.
The valve body 122 is hollowed, and the valve bushing 124 is fixedly secured within. The valve bushing 124 is also preferably hollowed and is further preferably made of a carbon/graphite composite material. As best illustrated in
The output port 140 is composed of a generally circumferentially oriented slot through the wall of bushing 124, such that the output port 140 utilizes approximately 90° of a circumference of the bushing 124. The output port 140 is constructed by left and right aperture segments 141,143 joined into one continuous circumferentially oriented slot by a horizontal aperture 145. Each aperture segment 141,143 of the output port 140 is shaped to approximate the same shape as the diametrically opposed port. Thus, in
Operation of the rotary valve 82 will be described in more detail below.
To mount the rotary valve 82 on the motor 78, the valve body 122 with the hollowed bushing 124 fixedly secured therein is slid over the central rotor 80, such that the elongated slot 116 of the central rotor 80 is aligned with the matching elongated slot 142 of the bushing 124. Alignment of the elongated slots 116,142 occurs when pressurized air can pass through both slots 116,142. A washer and screw combination 144 (see
As noted above, the valve body 122 includes threaded apertures 132 for receipt of fittings 134 to connect supply lines. As best illustrated in FIGS. 6 and 9-13, the apertures 132 are aligned with the exhaust, intake, and output ports 136,138,140 of the valve bushing 124. Reference numerals for the various ports in
The hand held device 18 is any pressurized air impact work tool 152 for carving, engraving, or other delicate operation that includes a chisel or hammer tool 154 for impacting an article. Fluid actuated hand held devices are also known in the art and contemplated by the present invention. The work tool 152 of the hand held device 18 preferably includes an internal, hollowed chamber (not shown) and a spring-loaded, air actuated piston (not shown) housed therein and operable to move forward and backward along a stroke length upon injection of pressurized air into the chamber, as is well known in the art. Pressurized air transported through the valve output supply line 146 exits to the work tool 152 of the hand held device 18 to operate the piston, resulting in impact by the chisel or hammer tool 154 of the work tool 152. The hand held device 18 of the present invention is fully described in the '912 Glaser patent and is hereby incorporated by reference.
The hand held 18 device further includes a work tool selector 156 accessible on the front panel 34 of the housing 20, as illustrated in
As noted above, air exiting the exhaust port 136 of the rotary valve 82 is guided through either the throttle supply line 148 to the throttle 84 or through the fine adjust supply line 50 to the throttle bias valve 86. The throttle 84 and throttle bias valve 86 operatively cooperate to allow selective bleeding of air to the atmosphere during operation. The throttle 84 includes a foot pedal 162 (see
The throttle 84 operates to actuate the work tool 152 of the hand held device 18 by depressing the foot pedal 162. When the foot pedal 162 is in its rest state and not depressed, and the throttle bias valve 86 is closed or mainly closed, it is not possible for sufficient exhaust to flow out of either of the throttle supply line 148 or the fine adjust supply line 150 to allow the piston of the work tool 152 to retract. Consequently, as the central rotor 80 rotates to the next pressure intake position, the piston cannot move forward because it did not retract during the exhaust portion of the valve cycle. In contrast, when the foot pedal 162 is depressed and/or the throttle bias valve 86 is open sufficiently, as the rotor 80 is rotated, and the elongated slot 116 comes into alignment with the exhaust and intake ports 136,138, and therefore also the diametrically opposite output port 140, there will be alternating periods of exhaust and intake, respectively, sufficient to actuate the piston of the work tool 152, thus creating controlled impact. The impact cycle, i.e., when the elongated slot 116 is aligned with the exhaust and intake ports 136,138, repeats every 180° rotation of the rotor 80, as long as sufficient exhaust is allowed to exit by either depressing the foot pedal 162 and/or opening the throttle bias valve 86. Further description of the operational features of the rotary valve 82 is described below.
As can be appreciated, in order to begin operation of the work tool 152 using the foot pedal 162 of the throttle 84, the foot pedal 162 must be depressed enough to allow sufficient air to escape from the chamber of work tool 152 so that the following intake air pressure pulse can move the internal piston of work tool 152 to create the desired impact. This depression of the foot pedal 162 the initial amount is herein referred to as “pretravel.” As the air is released from the chamber of work tool 152, the spring can move the piston into a retracted rest position. From this retracted rest position, the addition of pressurized intake air will force the piston forward, creating an impact that is transferred to the chisel or hammer tool 154. If the foot pedal 162 is not depressed and/or the throttle bias valve 86 is not open, the loading of the chamber of the work tool 152 with pressurized air will prohibit the piston from stroking back and forth. Because the air regulator 40 using dial 14 allows the user to control the pressure of intake air, it is possible to control the amount of air pressure that loads into the chamber of work tool 152. At elevated air pressure loads, it can be appreciated that the foot pedal 162 must be depressed considerably further to allow sufficient air to exhaust in order that the piston can move into a retracted position. This variable air pressure loading creates inconsistent foot pedal behavior. By opening the throttle bias valve 86, the user can allows a desired amount of exhaust air to escape, such that any movement of the foot pedal 162 will cause immediate piston retraction. Therefore, the addition of the throttle bias valve 86 aids greatly in the control of the work tool 152 and allows the user to make use of a much wider range of air pressures to operate the work tool 152 without the resulting pretravel of foot pedal 162.
As illustrated in
In some work situations, the user may desire more impact force from the work tool 152 than is obtained using normal operating air pressure. The user may seek to increase the impact delivered by correspondingly increasing the air pressure. However, any increase in air pressure beyond what is necessary to maintain proper spring compression in work tool 152 can result in compromised operation of work tool 152 and even a reduction in impact power instead of the desired increase. This is largely due to the fact that the increased air from the intake cycle cannot be sufficiently released during the exhaust cycle, which reduces piston stroke travel and hence impact power. However, with the addition of the throttle bias valve 86, it is possible to increase the exhaust of air to allow efficient operation at significantly higher air pressures. This operation at increased air pressures can be referred to as overdrive operation or overdriving.
The pressure gauge 88, as best illustrated in
The pressure gauge 88 preferably includes an outward facing register face 170 that includes a needle 172 and markings (not shown) for reflecting the magnitude of pressurized air incoming in pounds per square inch (psi), and preferable, the markings register at least 60 psi. A suitable pressure gauge is manufactured by Ashcroft Inc. of Stratford, Conn.
As illustrated in
The impact power tool 10 also includes an auxiliary air supply 188 for use with other pressurized air power tools 190. The auxiliary air supply 188 includes an auxiliary supply line 192 extending from the air storage tank 42 and to an auxiliary air port 194 located on the front panel 34 of the housing 20, as best illustrated in
As briefly discussed above, the housing of the impact power tool 10 stores the air delivery system 12 and the drive assembly 16. The housing is vertically oriented, as opposed to horizontally oriented, to conserve space on the user's crowded work bench. The base plate 24 is non-metallic, and in preferred forms, the base plate 24 is a thick plastic. Use of a plastic base plate 24 allows for connecting of the electrical wires on the base plate 24 and other electrical isolation. Additionally, use of the plastic base plate 24 reduces noise and vibration in conjunction with the above-described motor suspension system 92. The base plate 24 further includes a condensation drain path (not shown) for drainage of condensation resulting from the pressurized air.
The multi-panel construction of the cover 26 of the housing 20 allows for simplified removal of any one panel for access to the interior space 22 of the housing 20. Additionally, because any one panel can be easily removed, future expansion modules may be added to the existing housing 20 without constructing a completely new housing. Further, because the panels are flat metal, the housing 20 is free of any bends in sheet metal, further simplifying manufacture and construction.
The housing 20 further includes left and right extruded, beveled rails 196. As best illustrated in
In operation, the port geometry described above for the rotor port 114 of the central rotor 80 and the exhaust port 136 of the valve bushing 124 addresses several operational issues, including low speed impact performance, high speed piston response, and throttle control sensitivity. In particular, the elongated slot design of the rotor port 114 and exhaust port 136 allows for quicker opening and closing of air flow and an increase in open cross sectional port area, which results in additional impact performance for the hand held device 18. As described above, when pressurized air enters the rotary valve 82, air will not flow to the hand held device 18 unless the elongated slot 116 of the central rotor 80 is in alignment with the intake port 138 of the valve bushing 124. This alignment occurs every 180° rotation of the central rotor 80. Therefore, every 180° rotation, a “pulse” of pressurized air is received by the hand held device 18, which results in one strike of the hammer or chisel tool 154 of the work tool 152 against an article. When the elongated slot 116 of the central rotor 80 is aligned with the exhaust port 136, air enters the exhaust port 136 and either of the throttle supply line 148 or fine adjust supply line 150, as described above.
The elongated port design of the present invention provides a distinct advantage over other prior art designs. In preferable form and as illustrated in
Similarly and as also illustrated in
Having this ratio of major dimension to minor dimension for the elongated slots 116,142 allows for the quicker opening and closing of the air flow. As can be appreciated, as the elongated slot 116 of the central rotor 80 begins to come in alignment with the elongated slot 142 of the valve bushing 124, air begins to enter the right aperture 143 of the output port 140. Because of the elongated major dimensions of the ports, air enters at a faster rate than with, for example, a circular port. For comparison, with a circular port, air enters/exits at a slower rate because the amount of cross sectional area available in the port is less at the beginning and ending stages of alignment. With the elongated slots 116,142 of the present invention, air enters/exits at a much faster rate because of the increased cross section of the slots 116,142, which results is the quicker opening and closing of the air flow.
The elongated port design also allows for more air to enter than a circular port geometry. When a circular port geometry is implemented, the only way to increase air flow is to increase the diameter of the port. However, the diameter of a circular port is restricted to approximately ⅛th or 12.5% of the circumference of the central rotor 80. In contrast, the present invention's rotor port 114 geometry, as shown by slot 116, has a port width less than approximately 8% of the circumference of the rotor shaft. However, because the overall cross sectional areas of the present invention's ports are larger than the circular port geometry, more air is allowed to enter the output port 140. This results in increased impact performance by the hand held device 18.
The elongated port geometry of the present invention also results in a larger variation in cycle time between the pressure pulse described above and the bleed pulse. The graph of
In marked contrast, the present invention illustrates a much faster increase in aligned area of the slots 116,142 of the central rotor 80 and valve bushing 124, as discernable by the larger positive slope as compared to the prior art. Additionally, the present invention provides a significantly larger amount of aligned area than the prior art, which allows more increased air flow. A further advantage of the present invention is that the bleed time or pulse, represented as the negative area in
The air storage tank 42 of the present invention also facilitates in meeting the demands of the impact power tool 10. In particular, due to the demands of the high speed, pulsed air system of the impact power tool 10, pressurized air from the pressurized air source must be regulated extremely quickly. Even modern, high precision air regulators, or high speed precision air regulators, which normally have more than adequate response time, cannot meet the demands of the impact power tool 10 in increasing or decreasing airflow quickly enough to maintain the desired air pressure within reasonable tolerances. The air storage tank 42, however, provides a source of regulated air that is easily accessible by the rotary valve 82. As a numerical example, the air storage tank 42 of the present invention in a preferred embodiment stores approximately 4 to 50 times the internal air volume of the supply lines, which of course hold a certain amount of air volume when in operation; in a more preferred embodiment stores approximately 8-30 times the internal air volume of the supply lines; and in a most preferred embodiment, stores approximately 10-20 times the internal air volume of the supply lines. Thus, even if the regulator 40 experiences a time lag in adequately regulating the incoming pressurized air, enough regulated air is stored in the air storage tank 42 that both low speed impact and high speed response of the hand held device 18 are improved.
The air storage tank 42 capacity can also be compared to the volume of the elongated slot 116 of the central rotor 80. It has been determined that a preferred storage volume of air for the air storage tank 42 is approximately 200 to 3000 times greater than the volume of elongated slot 116 of the central rotor 80. A more preferred range of storage of volume of air for the air storage tank 42 is approximately 500-2000 times greater than the volume of slot 116 of the central rotor 80, and a most preferred range of storage volume is approximately 800-1200 times greater.
The inventors hereby state their intent to rely on the Doctrine of Equivalents to determine and assess the reasonably fair scope of the present invention as pertains to any apparatus not materially departing from but outside the literal scope of the invention as set forth in the following claims.
This application claims the benefit of U.S. Provisional Application No. 60/595,764, filed Aug. 3, 2005, and entitled IMPACT POWER TOOL WITH PRECISION CONTROLLED DRIVE SYSTEM, which is hereby incorporated by reference herein.
| Number | Name | Date | Kind |
|---|---|---|---|
| 3393755 | Glaser et al. | Jul 1968 | A |
| 4694912 | Glaser | Sep 1987 | A |
| 4903784 | Glaser | Feb 1990 | A |
| 5203417 | Glaser | Apr 1993 | A |
| 5857485 | Perkins et al. | Jan 1999 | A |
| 6488102 | Lindsay | Dec 2002 | B2 |
| 6691798 | Lindsay | Feb 2004 | B1 |
| 7048073 | Hezeltine | May 2006 | B2 |
| Number | Date | Country | |
|---|---|---|---|
| 20070034395 A1 | Feb 2007 | US |
| Number | Date | Country | |
|---|---|---|---|
| 60595764 | Aug 2005 | US |
