|Publication number||USRE43041 E1|
|Application number||US 11/955,996|
|Publication date||Dec 27, 2011|
|Priority date||Dec 22, 2000|
|Also published as||CA2432980A1, US6974061, US20020185514, US20050040206, WO2002051591A1|
|Publication number||11955996, 955996, US RE43041 E1, US RE43041E1, US-E1-RE43041, USRE43041 E1, USRE43041E1|
|Inventors||Shane Adams, Conrad Garvis, Richard Louis Leimbach|
|Original Assignee||Senco Brands, Inc.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (37), Non-Patent Citations (1), Classifications (16), Legal Events (4)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This reissue patent application of U.S. Pat. No. 6,974,061 is related to Reexamination patent application Ser. No. 90/008,833, which is directed to U.S. Pat. No. 6,974,061. A reexamination certificate issued in Reexamination patent application Ser. No. 90/008,833 on May 11, 2010. The changes shown in this reissue patent application are relative to the changes to U.S. Pat. No. 6,974,061 as shown in the issued reexamination certificate.
This application is a divisional of U.S. Non-Provisional Patent Application Ser. No. 10/027,767, filed Dec. 20, 2001, now abandoned, entitled CONTROL MODULE FOR FLYWHEL OPERATED HAND TOOL.
This application claims the priority of Provisional Patent Applicant Ser. No. 60/258,022, filed on Dec. 22, 2000 and incorporates herein, by reference, the totality of the invention disclosure therein.
This application is related to three commonly-owned, co-pending U.S. non-provisional patent applications filed on even date herewith and respectively titled, “FLYWHEEL OPERATED TOOL” to Conrad Gravis, et al; “FLYWHEEL OPERATED NAILER” to John Burke, et al; and “RETURN MECHANISM FOR A CYCLICAL TOOL” to Kevin Harper, et al. This application further relates to the commonly-owned, co-pending U.S. non-provisional patent application to Shane Adams, et al., filed on even date herewith and titled “SPEED CONTROLLER FOR FLYWHEEL OPERATED HAND TOOL”.
This invention generally relates to a hand-held electromechanical fastener driving tool, and more particularly to a fastener driving tool having an inertial member for imparting kinetic energy to drive a fastener into a work piece.
In the past, where relatively large energy impulses have been required to operate a fastener driving tool, such as an industrial nailer or stapler, it has been common practice to power such tool pneumatically. Such tools are capable of driving a 3″ or longer nail, or staple, into framing wood such as 2×4s, for example. However, pneumatic driving tools require an on-site air compressor, which is often unavailable or not desired. Also, dragging the pneumatic umbilical is often an impediment to the user.
Corded AC electrical fastener driving tools are often used instead of pneumatic power since electrical power is more often available than air compressors. In particular, much effort has been expended in the prior art in providing heavy duty, high powered, fastener driving tools employing a flywheel as a means of delivering kinetic energy sufficient to drive a heavy duty fasteners. Examples of such systems are disclosed in U.S. Pat. Nos. 4,042,036; 4,121,745; 4,204,622; 4,298,072; and 5,511,715. Use of a flywheel is an attempt to limit the large current draws to actuate a solenoid to drive a fastener. A DC motor is activated over a non-instantaneous period and then the kinetic energy thus developed in the flywheel is clutched to the driver in an “energy dump”.
While such corded electrical fastener driving tools may perform well, in many instances an AC outlet is not available. Even if an AC outlet is available, many users find dragging the electrical cord to be an impediment to use. To address these preferences, it is further known to employ a portable power source such as a battery, such as solenoid-operated fastener driving tools. These portable fastener driving tools are primarily used in light-duty applications such as in driving one inch brad nails, for example, rather than the larger 2″ to 4″ staples or nails used in framing.
One approach to an efficient portable electrically driven tool is a multiple impact tool, such as described in U.S. Pat. No. 4,625,903, wherein a linear inertial member is repeatedly raised by a cam against a compression spring and released to impact a fastener. An electrical motor and portable battery pack are operated in a more efficient manner by running the motor for a period of time rather than providing a surge of power to a device such as a solenoid. The relatively small amount of energy stored in the spring each cycle typically requires a large number of impacts to drive a staple or nail into a workpiece. During this time, the user is required to maintain an appropriate position and force on the fasten and to gauge the appropriate length of time to achieve the desired depth. However, while the multiple impact tool is efficient and effective in driving fasteners, some users prefer a single driving action comparable to pyrotechnic or compressed air systems. The multiple impact tools also can damage a wood surface due to the vibrations the tool generates while stroking.
It would be desirable to use a battery to power a flywheel operated hand tool to provide a portable fastener driver that can drive larger fasteners in a single drive. However, using a battery has been thwarted by a number of challenges. First, each specific application generally requires a fastener drive assembly and motor customized for the type of fastener. In particular, the size of flywheel, the desired rotary speed of the flywheel, and the type of electric motor to accelerate the flywheel to the desired rotary speed are generally specifically sized for the type of fastener and work piece into which the fastener is typically driven. Thus, each specific application was thought to require a custom control module, with the increased costs of design, manufacture and support.
Even assuming that various types of fasteners could then be used with a family of flywheel operated hand tools, each tool would suffer the disadvantages inherent in using battery power. The battery voltage varies as a function of the amount of charge remaining and the amount of electrical current being drawn. The rotary speed of the flywheel varies with the battery voltage, and thus the depth of drive of the fastener would unacceptably vary. The generally known controllers for corded flywheel operated hand tools are unable to accommodate these power variations.
Furthermore, even for a specific application, the desired depth of drive is affected by the type of work piece into which the fastener is driven and to user preferences. However, flywheel operated hand tools rely upon a given amount of kinetic energy imparted by the flywheel to achieve a desired depth of travel. Thus, when the work piece is more or less dense, the depth of the drive will vary. Moreover, the user may prefer in some instances to sink the fastener below the plane of the work piece or to leave the head of the fastener exposed for easy removal.
Other types of hand tools, such a pneumatic powered hand tools, generally rely on driving the fastener to a specific position in order to achieve a desired depth. For example, in U.S. Pat. Nos. 4,679,719, 5,732,870 and 5,918,788 a control module is described that advantageously determines the mode of operation for the trigger. In particular, a microprocessor provided additional capabilities by receiving two signal inputs initiated by the user and by selectively activating an electronic solenoid in response thereto. Although the increased functionality of the control module in such pneumatic tools has advantages, these control modules are not responsive to changes in operating conditions to vary the depth of drive.
Other tools employing a rotary member (e.g., drill) generally require the user to determine the proper speed of the tool. The user provides the closed loop control of the tool, monitoring the tool for binding and proper operation and depressing the trigger an appropriate amount. However, consistent operation of the tool is thus dependent upon the skill level and attentiveness of the user. Due to the speed in which a fastener must be driven into the workpiece, the user would only learn after the fact whether the rotary member (in this case a flywheel) was accelerated to an appropriate speed prior to firing.
Therefore, a significant need exists for a control module that drives medium and large fasteners into a work piece with a single driving action, yet has the increased portability of battery power. It would be further desired to have such a tool that consistently provides a depth of fastener regardless of the state of charge of the battery. It would be yet further desired to have a control module readily adapted to a family of hand tools.
These and other problems in the prior art are addressed by a control module that is responsive to a rotary speed of a rotational member of an electrically powered hand tool and is responsive to an adjustable target speed for the rotational member. Thereby, the control module more consistently controls the hand tool, avoiding human error and the inconvenience of relying upon the user to modulate the speed of the tool.
In one aspect of the invention, a control module for a hand tool includes a speed setting that is used for presetting the control module to an operating range of the intended rotational member of the hand tool. Thus, the control module is readily adjusted to the operating environment, using the speed setting as a target for comparing a sensed speed.
In another aspect of the invention, a method of controlling a fastener-driving tool enforces a user input sequence to ensure that a fastener is driven into a workpiece. In particular, a safety signal is received from a safety switch indicating a nose assembly of the tool is against a workpiece. A safety time-out value is accessed. The duration of depression of the safety signal is timed. Then, the tool is activated to drive a fastener in response to receiving a trigger signal from a trigger switch before the timed duration of the safety signal exceeds the safety time-out value. By so enforcing this sequence, a user is less likely to inadvertently drive a fastener in instances where the trigger is inadvertently squeezed and the tool contacts a surface.
In yet another aspect of the invention, an electrically powered hand tool is provided a reliable interface to a control module through use of a thin film switch interface to user controls (e.g., safety and trigger) and through use of noncontact speed sensing.
These and other objects and advantages of the present invention shall be made apparent from the accompanying drawings and the description thereof.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention, and, together with the general description of the invention given above, and the detailed description of the embodiments given below, serve to explain the principles of the present invention.
With reference to
The DC motor 24, when accelerated by the control module 18, turns a flywheel 28 to build kinetic energy in the form of rotational inertia. Thereafter, the control module 18 actuates the solenoid 26 in response to user inputs and a sensed parameter of rotational speed of the flywheel 28 to impart the kinetic energy of the flywheel 28 to a fastener, which is described in further detail below
A user input to the nailing tool 10 are depicted as a trigger 30 of the handle 20, which mechanically communicates with the control module 18 via a trigger linkage 32. Another user input is depicted as a safety device 34 of a nose assembly 36 that mechanically communicates with the control module 18 via a safety linkage 38. Yet another user input is depicted as a speed adjust knob 40.
The nailing tool 10 includes a fastener supplying magazine assembly 42, which is typically attached to the main body 14 and handle 20, as illustrated, for supplying a strip of fasteners (not shown) to the nose assembly 36. It will be appreciated that the control system 12 may be advantageously operated with different types of magazine assemblies 42 to include different numbers, types and sizes of fasteners. Moreover, the control system 12 advantageously enhances use of indexed magazine assemblies, as will be described in more detail below.
With reference to
The control module 18 further includes a thin film printed circuit 46 that provides an extremely reliable electrical interface to the mechanical user inputs of the safety device 34 and the trigger 30. Moreover, the printed circuit 46 is readily adapted to various three-dimensional orientations with the support of a molded bridge 48. Thus, a trigger switch 50 and a safety switch 52 are readily positioned to receive the respective trigger and safety mechanical linkages 32, 36. It will be appreciated that thin film switches 50, 52 provide a service life that exceed generally known trigger and safety switches and at a reduced cost.
The molded bridge 48 further supports and orients a portion of the printed circuit 46 that forms a rotary speed transducer 54. Two inductive pickups 56, 58 of the printed circuit 46 are oriented to register to respectively to alternating north and south magnetic poles on a ring magnet (not shown in
Before discussing the control system 12 in greater, the mechanical aspects of the fastener drive assembly 16 are discussed in greater detail.
Fastener Drive Assembly of the Flywheel Operated Hand Tool
The fastener drive assembly 16 is described that has features of efficiently uses DC electrical power by accelerating the flywheel 28 with the DC motor 24. A clutching technique is advantageously used that avoids the need for a manual reset. In addition, components are described below that advantageously couple to the flywheel during acceleration to increase the inertial load prior to driving the fastener and then disengage after driving the fastener. Furthermore, resetting the fastener drive assembly 16 with a vacuum return approach further conserves electrical power and avoids the generally known techniques that require a manual reset key.
Referring now to
Referring particularly to
Clutch drive assembly 64 and flywheel 28 are axially aligned upon central shaft 62 as best illustrated in
Flywheel 28 is rotatingly positioned at the end of central shaft 62, as best illustrated in
Flywheel 28 includes a conical cavity 82 for receiving therein a conical friction surface 84 of conical clutch plate 66. Clutch plate 66 and an activation plate 86, although they are separable members, are geared to a drum 88 by interlocking projections 90 and 92 respectively, whereby clutch plate 66, activation plate 86 and drum 88 rotate freely about shaft 62 as a single unitary assembly. Roller hearings 94a and 94b, positioned on the inside diameter of drum 88, are provided to assure the free rotational characteristic of activation plate 86, drum 88 and clutch plate 66 as a unitary assembly.
Adjacent activation plate 86 is a fixed plate 96. Fixed plate 96 and activation plate 86 are connected to one another by three equally spaced axially expandable ball ramps 98a, 98b, 98c, 98a′, 98b′, and 98c′ as illustrated in
Fixed plate 96 includes a circular projection 104 receiving thereon freely rotatable thrust bearing 106 positioned between fixed plate 96 and a retarder plate 108. A pair of nested, parallel acting, Belleville springs 110 are positioned, as illustrated in
Positioned upon central shaft 62, between clutch plate 66 and flywheel 28, is a compression spring assembly 114 comprising washers 116 and 118 having a coil spring 120 therebetween the function of which is described in further detail below.
Upon start of the fastener work, or driving, cycle, the control module 18 causes motor 24 to “spin up” flywheel 28, in the counter clockwise direction as indicated by arrow A in
As drum 88 rotates counter clockwise, cables 126a and 126b wrap about peripheral grooves 128 and 130 in drum 88 and clutch plate 66 respectively, thereby drawing a vacuum return piston assembly 132 downward, within a cylinder 134, in a power, or working, stroke whereby the attached fastener driver 68 is likewise driven downward, through guide block 108 and opening 135 within frame 72, thereby driving a selected fastener into a targeted workpiece.
Upon disengagement of clutch plate 66 from flywheel 28, coil spring 120 urges all elements of clutch drive assembly 64 back toward end plate 70. The resulting axial force and pressure now being applied to solenoid plate 112, by action of coil spring 120 and Belleville springs 74, cause solenoid plate 112 to close upon end plate 70. The pressure being exerted, by solenoid plate 112, upon balls 140 cause solenoid plate 112 to rotate, counterclockwise, towards its original start position whereby solenoid cable 122, being wrapped about solenoid plate 112, stops the rotation of solenoid plate 112 when solenoid plunger 124 returns to its start position as illustrated in
By constructing the clutch drive assembly 64, as taught hereinabove, clutch plate 66 disengages from flywheel 28 thereby allowing flywheel 28 to continue spinning after clutch drive assembly 64 has reached the end of its power stroke. Thus in the event it is desired to successively drive additional fasteners, the remaining kinetic energy is available for the subsequent operation thereby economizing battery power and saving the drive assembly elements and/or the frame 72 from having to absorb the impact that would otherwise occur by bringing flywheel 28 to a full stop immediately after the power stroke. This feature also permits “dry firing” of the tool.
The clutch drive system as taught herein also provides for automatic compensation for clutch wear in that the expansion between end plate 70 and solenoid plate 112 will continue until clutch plate 66 engages flywheel 28 thereby allowing solenoid plate 112 to take up the difference at the start of every power drive.
Referring now to
The inside diameter D, of cylinder 134, is flared outward to diameter D′ at the top of cylinder 134 as illustrated in
As piston assembly 132 is drawn axially into cylinder 134, during the power stroke of fastener driver 68, O-ring 146 slidingly engages the inside wall diameter D of cylinder 134 thereby forming a pneumatic seal between inside wall 153 of cylinder 134 and piston assembly 132. As piston assembly 132 progresses into cylinder 134, a vacuum is created within the top portion of cylinder 134, between advancing piston assembly 132 and the sealed end cap 154.
Upon disengagement of friction clutch plate 66 from flywheel 28, the vacuum created within the top portion of cylinder 134 draws piston assembly 132 back toward an end cap 154 thereby resetting activation plate 86, drum 88, and clutch plate 66, as an assembly, to their restart position.
As O-ring 146 passes from inside diameter D to diameter D′, on its return stroke, any air that may have by passed O-ring 146, during the power stroke, is compressed and permitted to flow past O-ring 146 through annular gap 152 and to the atmosphere through cylinder 134, thereby preventing an accumulation of entrapped air above piston assembly 132. A resilient end stop 156 is preferably positioned within end cap to absorb any impact that may occur as piston assembly 132 returns to its start position at the top of cylinder 134.
As drum 88 returns to its start position tang 157 radially extending from drum 88 engages abutment block 158 affixed to frame 72, see
It will be appreciated that the above-described fastener drive assembly 16 is illustrative and that aspects of the invention have application in other types of fastener drive assemblies.
Additional structural and operational details of the fastener drive assembly 16 is completely described within the two co-pending patent applications identified in the “Related Patent Applications” section above and are incorporated herein by reference.
A signal representative of the rotational rate (e.g., RPM) that a plurality 212 of radially arrayed pairs of magnetic poles rotate with the flywheel 202 is generated by a transducer 214 that senses each closest pair of registered magnetic poles 216, 218 of the plurality 212. In addition to flywheel speed signal, the control system 200 responds to other types of inputs. For example, the input signals 204 may include a trigger input 220, a safety input 222, a user speed adjustment input 224, a continuous flywheel mode switch input 226, a fastener type sensor input 228, and a fastener transducer input 230 for sensing the presence of a fastener positioned for driving.
A fastener indexer 232 may advantageously respond to an electrical command from the control module 206. The electric interface to a separable indexing magazine (not shown) may be readily designed and assembled with electrical interconnects. This advantageously compares to pneumatic power tools with indexing wherein more complicated pneumatic plumbing at the interface of the magazine and main body is required.
The control module 206 may respond to an enabling condition input 234. In some instances, the availability of electrical power in combination with actuation of a trigger or depression of a safety may be deemed an enabling condition for powering the nailing tool 10. Alternatively or in addition, the enabling condition input 234 may represent other input signals that enable or disable the nailing tool 10. For instance, the enabling condition input 234 may include a sensed motor overheat condition, an ON/OFF switch, a battery power voltage level, or presence of an AC electrical power input. The latter may cause the control module 206 to switch power source, or to charge a battery.
Battery input 236 may represent a source of power for the control module 206. In addition, the control module 206 may respond to the voltage level of the battery input 236 by altering time-out values when the control module expects to see acceleration and actuation performed. For example, for a given battery voltage level, the flywheel motor 208 should accelerate to a given target speed in a certain time range, whereas this time range would be expected to change in relation to the voltage level. Thus, mechanical failures would be more accurately detected by more accurately predicting the performance thereof.
The electronic control module 206 includes interfaces 240–256 for these input signals 204. A speed sensor 240 may convert the speed signal from the transducer 214 into another form. For instance, the speed sensor may convert an analog signal into a near DC signal (digital signal) suitable for digital signal processing. A thin film switch “A” 242 converts a mechanical trigger input 220 into an electrical trigger signal. A thin film switch “B” 244 converts a mechanical safety input 222 into an electrical safety signal. A preset speed range interface 246 may fully comprise a speed selection or define a flywheel speed range for user speed adjustment input 224. The present speed range interface 246 may define a range constrained by a combination of the operable range of the flywheel motor 208 and/or clutch actuator 210 and the force requirements expected for the fastener and type of workpiece. A continuous mode input 248 receives a selection for continuous or intermittent mode for the flywheel. It should be appreciated that continuous mode or intermittent mode may be used at the exclusion of the other mode. Alternatively or in addition, the selection may be determined based on another consideration such as state of charge of the battery (e.g., switching to intermittent mode to save electrical power when a battery is partially discharged). A fastener type input interface 250 senses or accepts a selection from the fastener type sensor input 228, which may advantageously adjust speed and timing considerations. A fastener sensor interface 252 responds the fastener transducer input 230 to convert the signal into a form suitable for digital processing. The control module 206 may respond to the presence or absence of a fastener ready for driving in a number of fashions. For example, dry firing may be prevented to avoid wear or a jam of a partially loaded or improper fastener; an indication of the need to load the magazine may be given, a continuous mode for the flywheel may be discontinued, etc. For applications with an indexing magazine, an index control interface 254 provides an index signal suitable for the fastener indexer 232.
The control module 206 is depicted as including a power supply 256 that responds to the enabling condition input 234 and the battery input 236. It should be appreciated that the power supply may comprise a power source for the control module 206 only, wherein power drain on the battery is prevented by shutting down the control module 206 except when commanded to drive a fastener or when in continuous mode and the tool 10 is enabled. The power supply 256 may further represent logic to select a source of electrical power and/or to charge an attached battery. In addition, the power supply 256 may represent additional safety features to prevent electrical power from inadvertently reaching actuating components.
The electronic control module 206 provides a motor control interface 260 to convert a control signal into a form suitable for the flywheel motor 208 (e.g., a logic signal to a pulse width modulated (PWM) power signal). A clutch control interface 262 converts a control signal into a form suitable for the clutch actuator 210 (e.g., a logic signal to power signal).
The control system 200 may advantageously include additional features to the user to include an aim indicator 264 that is controlled by an indicator control interface 266 in the control module 206. For example, in response to an enabling condition such as depression of the safety against a workpiece, a focused light or laser pointer may be directed at the expect point of the fastener. The illumination thereof may assist the user in seeing the workpiece more clearly in dim lighting or to better appreciate the aim of the tool.
The electronic control module 206 advantageously includes a digital controller 300 that is programmed for additional features. To that end, a processor 302 accesses instructions and data by indirect addressing through a pointer 304 of a Random Access Memory 306. The processor and/or memory access analog-to-digital (A/D) inputs 308, such as from the speed sensor 240, that are used and stored in digital form. Although not depicted, another example may be the speed adjustment input 224 and preset speed range interface 246 as being analog inputs. The memory 306 includes instructions 310; a switch timer 312 for monitoring a stuck or inadvertently held switch; interrupts code 314 for handling time sensitive signals or abnormal processing; a motor timer 316 for monitoring overlong motor operation that could result in overheating; a switch debounce buffer 318 for precluding inadvertent or spurious switch signals from being acted upon; a speed target register 320 for holding a preset or calculated value for a desired or appropriate flywheel speed; an actuation timer register 322 for holding a preset or calculated value for monitoring for abnormally long time for transfer kinetic energy to the driver by actuation; a no-operation (no op) timer 324 for timing when to deactivate; or other data structures or unused memory 326
It will be appreciated that the instructions 310 include diagnostic code to perform RAM checking, verifying that all memory locations are working properly prior to use and that the program counter 304 is indexing correctly. The diagnostic code further checks that jumps and returns from subroutine locations return back to the correct location. In addition, the diagnostic code checks that when the processor 302 tells a pin to go high or low that the line attached to the pin responds accordingly.
The control module 206 includes a watch dog timer circuit 330 that prevents a processing failure. Throughout processing, it will be appreciated that the watch dog timer circuit 330 is periodically reset by the processor 302, lest a time limit be reached that initiates resetting or disabling the control module 206.
In the illustrative embodiment, a user input, such as depression of the safety switch, begins processing (block 404) by enabling the control system (block 406). Immediately, the control module performs diagnostics to preclude failures that may cause an inadvertent activation and actuation of the tool (block 408), discussed in more detail below. It will be appreciated that certain diagnostic features continue to be performed throughout operation.
Once diagnostics are complete, with a determination is made as to whether the safety is depressed (block 410). If so, an aim indicator is activated (block 412). This feature is included to illustrate features that may be performed to give visual indications to the user about the operation or condition of the tool.
Thereafter, a determination is made as to whether the tool is in continuous mode (block 414). This determination may be preset, user selected, or automatically selected based on considerations such as battery voltage. If in continuous mode in block 414, then a further determination is made as to whether an input has been made to ready the tool for actuation, for instance a depression of the trigger (block 416). And if so, the continuous mode is initiated as described below. Otherwise, an additional determination is made as to whether a no op timer has expired (block 418). If no operations have been received within a suitable time, then the control module is disabled (block 420) to prevent battery drain and preclude inadvertent actuation. If in block 418 the no op time-out has not occurred, then processing continues to wait for a trigger command to initiate the continuous operating of the flywheel.
Returning to block 414, if continuous mode is not selected or appropriate, then the main routine 400 is in an intermittent mode that advantageously accelerates the flywheel to a target speed each time a fastener is to be driven. Thus, battery power is conserved between driving cycles. Since residual kinetic energy of the flywheel is conserved by the fastener drive assembly, the cycle time is still short even in intermittent mode. In intermittent mode, a determination is made as to whether a valid command to drive a fastener has been received (block 422), and if so, initiating intermittent acceleration of the flywheel will be discussed below, as well as the forced sequence of the safety and the trigger for a valid command. If a valid command is not received in block 422, then a further determination is made as to whether a no op time-out limit has been reached (block 424), and if so the control module is disabled (block 420) and routine 400 is complete.
Also, digital parameters are initialized and any calibrations are performed (block 504). For example, interrupt vectors are set so that any resets will be appropriately handled. Also, analog devices like oscillators are calibrated. Then the processor memory is tested by checking for any failure to toggle and to read a memory location (Z BIT) (block 505). If Z BIT fails (block 506), then safety lock-out mode is set (block 503), else any unused memory is loaded with a reset code (e.g., interrupt vector) (block 508). In addition, a check is made as to whether the program counter (pointer) is corrupt (block 510), and if so safety lockout mode is set (block 512). If the program is not corrupt in block 510, then a delay occurs to allow for the power supply to the control module to stabilize (block 514). If not stable (block 516), then safety lockout mode is set (block 518). If stable in block 516, then the trigger time-out counter is set up so that overly long trigger commands due not result in actuation (block 520). Also, switch debounce code is set up so that momentary or spurious trigger or switch signals are ignored (block 522). Thereafter, routine 500 returns to the main routine 400 of
Advantageously, the motor command begins with a Pulse Width Modulated (PWM) soft start is used. Thus, the duty cycle of the PWM command ramps up to a full command level, reducing the initial electrical current demand on the battery and surge to the motor. Thereby, power consumption is greatly reduced and the service life of the motor is extended.
With the flywheel accelerating in response to the motor command, a determination is made as to whether the safety is still held (block 604). Withdrawal of the safety from the workpiece causes the motor command to be deactivated (block 606) and the control module to be disabled (block 608).
If the command is still valid in block 604, then a further determination is made as to whether the motor time-out has expired (block 610). If so, due to a failure in the fastener drive assembly (e.g., stuck clutch, motor failure, weak battery), the safety lockout mode is set (block 612). If the motor has not timed out in block 610, then the current sensed speed is compared to the target. If the target is not reached (block 614), then processing returns to block 602, continuing with a full motor command. If the target speed is reached in block 614, then the motor command is deactivated (block 616).
A speed reduction threshold is determined for imparting or transferring kinetic energy from the flywheel to the linearly moving fastener driver. Thus, not only is a known amount of kinetic energy available in the flywheel, but a known amount is transferred to the driver and thus to the fastener for a consistent depth of drive. Moreover, since the flywheel is not completely stopped during or after transferring the kinetic energy, the remaining kinetic energy is available for a subsequent operation. The speed reduction may be based on a look-up table for the given conditions, based on a fixed ratio of a current speed, or a fixed scalar amount below the target, or other measures.
The clutch is engaged to transfer the kinetic energy to the driver (block 620). Then a determination is made as to whether the threshold is reached (block 622). If not reached, then a further determination is made as to whether the actuation time-out has been reached (block 624), and if so, safety lock-out mode is set (block 626). If in block 622 the time-out is not reached, then actuation is still in progress by returning to block 620. Returning to block 622, if the reduction threshold is reached, then the clutch is deactivated (block 628). If installed and enabled, the fastener index is actuated (block 630). Then the control module is disabled (block 632) and main routine 400 ends.
Advantageously, continuous mode allows addition safety/trigger sequences for a valid command. For instance, rather than requiring the safety signal to precede the trigger signal, (“trigger fire”), the trigger signal may precede the safety signal (“bottom fire”). Again, a trigger time-out (e.g., 3 seconds) is applicable just as is the safety time-out (e.g., 3 seconds) to minimize inadvertent actuation. Bottom fire is included as an option in continuous mode for applications wherein the user desires very short cycle time between drives or has a personal preference for this technique.
If the target is reached in block 708, then the speed is held (block 710). For example an operating range may be entered wherein the motor command is recommenced when a lower limit is reached and removed when an upper limit is reached. Then, a determination is made as to whether a valid command has been received from the user (block 712). If not, a check is made as to whether the no op time-out has occurred (block 714), and if not, the flywheel speed is continuously maintained by returning to block 710. If the no-op timer has expired in block 714, then the motor command is deactivated (716) and the control module is disabled (block 718).
Returning to block 712 wherein a valid command has been received, then the clutch is actuated in a manner similar to that described above for the intermittent mode, wherein blocks 720–734 correspond respectively to block 616–630. However, after deactuating the clutch in block 732 and actuating a fastener index in block 634, control returns to block 710 to continue holding speed in a continuous fashion awaiting the next valid command to drive a fastener.
The portion of the motor signal between times “t2” and “t3” of
A speed sensor 802 is picks up alternating north and south magnetic fields 804 on a ring magnet with an inductive transducer 806. In particular, a series pair of coils 808 have their shared node is grounded and their opposite ends connected to a differential amplifier, or comparator U1, such as model no. TA75S393F. Thus, as each pair of fields 804 of the 32 alternating poles are encountered, the push-pull arrangement or differential arrangement enhances signal integrity and noise immunity of the differential speed signal of about 10–15 mV. The comparator U1 is biased between power supply VDD and ground. The positive bias is also coupled to ground via capacitor C1 suppress high frequency noisy disturbances from the power supply.
The output node of the comparator U1 is coupled to ground via a capacitor C2 to rectify and low pass filter the differential speed output that is passed to the +T input of a monostable multivibrator (one shot) U2, such as model no. MM74HC4538 by Fairchild Semiconductor Corporation. The one shot U2 is an integrated circuit that, when triggered, produces an output pulse width that is independent of the input pulse width, and can be programmed by an external resistor-capacitor (RC) network to set the pulse width. To that end, the RC input of the one shot U2 is coupled to the common node of a series resistor R1 and capacitor C3, the series coupled between power supply VDD and ground, respectively. The inverted input CS of the one shot U2 is coupled to the common node of a series resistor R2 and capacitor C4, the series coupled between power VDD and ground, respectively. The inverted output
The pulse train at output Q of one shot U2 is connected to a node 810 via a resistor R3. The node 810 is also coupled to ground via capacitor C6. Thus, the signal at node 810 is low pass filtered, creating a near DC signal whose amplitude is related to rate of pulses. Thus, the sensed speed signal has been converted to a form suitable for digital processing.
A controller U3, such as an 8-pin RISC microprocessor performs the digital processing, model PIC12C671. The analog input GP1 of the controller U3 receives the near DC signal from node 810. This near DC signal is compared to a speed target reference signal at analog input GP0. The controller U3 changes the analog reference signal into a digital signal to be compared to the digitized speed signal with a resolution of one bit. The speed target reference signal is produced by preset speed adjust range formed by a voltage divider of trimmable resistors R4 and R5 coupled between power supply VDD and ground. Inserting an infinitely variable potentiometer 812 between resistors R4 and R5 advantageously provides a user speed adjustment. The pick off point of the potentiometer 812 is coupled to the analog input GP0 and also coupled to ground via capacitor C7 for noise suppression. It will be appreciated that the resistors R4 and R5 may be selected for a desired speed range within which the potentiometer 812 selects a target speed. The voltage thus produced at analog input GP0 may advantageously be selected for a desired voltage level corresponding to a target speed. When enabled by a safety signal at input GP2, the processor U3 awaits a trigger signal at input GP3, as described above in the timing diagrams of
The user initiates these actions by selecting a mode, either continuous or intermittent, at mode select switch 814, enabling the tool with safety switch 816, and then commanding the driving of a fastener with a trigger switch 818.
The safety signal is received in either continuous or intermediate mode, which affects the manner of operation of processor U3. Specifically, in continuous mode, switch 814 couples battery voltage VBATT to a resistor R6 whose value is selected to scale the battery voltage to the desired voltage VDD for the control system 800. The resulting power supply voltage VDD is further regulated by being coupled to ground via the parallel combination of a capacitor C8 and zener diode Z1. Thus, in continuous mode, the control system remains enabled, awaiting a safety and trigger signal to initiate the tool.
To that end, the mode switch 814 in continuous mode also couples the battery voltage to a first input of an AND gate 820, such as an SN74AHC1G08. The other input to the AND gate 820 receives battery voltage VBATT when the safety switch 816 is closed, inverted by inverter 822, such as an SN74AHC1G04. The output of the AND gate 820 controls the input GP2 via a biasing circuit 824. In particular, the output of the AND gate 820 is connected to input GP2 via resistor R7. The input GP2 is also coupled to power supply VDD via a resistor R8 and to ground via capacitor C9. When the trigger switch is closed, ground is coupled the input GP3 of the processor U3 via resistor R9. The input GP3 is connected to power supply VDD via resistor R10 and to ground via a capacitor C10.
When the mode switch 812 is in intermittent mode, the resistor R6 is connected to battery voltage VBATT when the safety switch 816 is closed. Also, the first input of the AND gate 820 is connected to ground.
The processor U3 commands a DC motor 826 with a motor signal at output GP4 that is coupled via resistor R11 to the base of a buffer, depicted as a small signal transistor Q1 such as a 2N4401. The base is also coupled to ground via resistor R12 to ensure that the transistor will be off if voltage is not applied to the base. The collector is connected to power supply VDD. The emitter is also connected to the base of a rectifier Q2, such as an IRL3803 that advantageously has a low RDS (on) characteristics minimizing energy dissipation, that is heat shielded. The emitter is also coupled to ground via resistor R13 to ensure that rectifier Q2 if off when not supplied with a signal. The turned-on rectifier Q2 thereby couples to ground a negative terminal respectively of a DC motor 826, a MOSFET configured as a diode Q3 (such as a model MTD20N03HDL) that advantageously has a high current carrying capacity in a small package. A positive terminal respectively of the diode Q3 and the DC motor 826 are coupled to battery voltage VBATT. Thus, the DC motor 826 is activated when rectifier Q2 closes.
The processor U3 commands a solenoid 828 with a solenoid signal at output GP5 that is coupled via resistor R14 to the base of a MOSFET configured as diode Q4 (such as a model MTD20N03HDL). The base is also coupled to ground via resistor R15 to ensure that the transistor will be off if voltage is not applied to the base. The rectifier Q4 has a negative terminal coupled to ground and a positive terminal coupled to a negative terminal of the solenoid 828. The positive terminal of the solenoid 828 is coupled to battery voltage VBATT, thus solenoid 828 activates when rectifier Q4 is closed by the solenoid signal. The rectifier Q4 advantageously withstands the electrical current spikes associated with inductive loads of solenoids.
In use, a user loads the magazine 42 of the nailing tool 10 with a strip of fasteners, and installs a charged battery 22. The tool is in a mode, such as Intermittent, conserving battery power by accelerating a flywheel each time that a fastener is to be dispensed or driven. As the nose assembly 36 is placed against a workpiece, closing a safety device 34, the safety mechanical linkage 38 contacts a highly reliable thin film safety switch 52, powering the control module 18. A trigger 30 is depressed, activating another highly reliable thin film trigger switch 50 via a trigger mechanical linkage 32. If the safety and trigger switches are actuated within appropriate time intervals and sequence (e.g., safety depressed and held no more than 3 seconds prior to trigger), then the processor U3 calculates a target speed for the flywheel set as appropriate for the fastener drive assembly 16 and/or an appropriate setting for the fastener and workpiece. As the flywheel accelerates, the speed signal from a noncontact speed sensor 60 is compared to the target speed. Once reached, the motor 24 is de-energized and then a solenoid actuation signal couples a clutch to the flywheel 28 to impart kinetic energy to a linearly moving fastener driver 68. The processor U3 uses a reduction threshold to determine when the flywheel 28 has imparted an appropriate amount of kinetic energy, thereafter allowing the flywheel 28 to continue spinning with any remaining energy available for the next cycle. By monitoring flywheel speed, fault conditions are detected such as a slow motor acceleration that could be due to low battery voltage, motor degradation or a stuck clutch. Similarly, by detecting an actuation time-out, the failure of the clutch drive assembly 64 to engage is detected, preventing jamming of the tool 10 if attempting to cycle again.
By virtue of the foregoing, a portable tool 10 provides a consistent drive in a single stroke, yet efficiently uses electrical power from the battery 22 without detrimental surges by using a DC motor 24 to accelerate a flywheel 28. Moreover, consistent drives are ensured across a range of battery voltages and component tolerance variations (e.g., clutch wear). The consistent rotary sensing and control of a rotary member (e.g., flywheel 28) has application more broadly to hand tools in accurately and robustly setting a desired speed.
While the present invention has been illustrated by description of several embodiments and while the illustrative embodiments have been described in considerable detail, it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications may readily appear to those skilled in the art. For example, aspects of the invention are applicable to other sources of power, such as corded power tools or pneumatic power tools. As another example, although a programmed approach is described herein, it will be appreciated that digital logic or analog controls may be used.
As a further example, although a noncontact speed sensor is disclosed, applications of the present invention may include other types of speed sensing. For instance, an optical encoding approach may be used, weigan sensor, variable reluctance sensors, Hall effect sensors, feedback from the motor such as a tachometer signal, and other techniques.
As yet a further example, the described control circuit 800 employs a battery voltage VBATT having a nominal value with resistors and a zener diode Z1 being used to step down the battery voltage to the power supply voltage VDD. However, it will be appreciated that a power supply (e.g., a switching power supply) capable of regulating the voltage to the integrated circuit components may be used while providing a battery voltage signal to a processor. Thereby the processor may adapt its command, timing, and other features to accommodate a wider range of battery voltage, thus extending service life. For instance, a processor having additional available inputs such as an 18-pin processor, model PIC16C71 may be used.
As an addition example, a speed adjustment circuit may employ other types of voltage references, such as a sized digital resistor. In addition, the processor may calculate or lookup in a table a digital reference against which the sensed speed signal is compared.
As another example, although a specific safety and trigger sequence is described, other sequences and time-out schemes may be employed. Moreover, even a single trigger scheme without a safety may be employed.
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|1||International Search Report dated May 16, 2000 for Application No. PCT/US01/49882.|
|U.S. Classification||227/2, 227/129, 227/133, 227/131|
|International Classification||B25C1/06, H02P7/29, B25C1/00, B25C5/15, H02P3/08|
|Cooperative Classification||B25C1/008, H02P3/08, B25C1/06, H02P27/047|
|European Classification||B25C1/00D, B25C1/06, H02P3/08|
|Jan 31, 2012||CC||Certificate of correction|
|Jan 2, 2013||AS||Assignment|
Owner name: BANK OF AMERICA, N.A., ILLINOIS
Free format text: SECURITY AGREEMENT;ASSIGNOR:SENCO BRANDS, INC.;REEL/FRAME:029561/0293
Effective date: 20121219
|Jun 13, 2013||FPAY||Fee payment|
Year of fee payment: 8
|Dec 30, 2013||AS||Assignment|
Owner name: LBC CREDIT PARTNERS III, L.P., AS AGENT, PENNSYLVA
Free format text: SECURITY AGREEMENT;ASSIGNOR:SENCO BRANDS, INC.;REEL/FRAME:031891/0374
Effective date: 20131226