Patent Application
20100038395
This invention relates to the field of devices used to drive fasteners into work-pieces and particularly to a device for impacting fasteners into work-pieces.
Fasteners such as nails and staples are commonly used in projects ranging from crafts to building construction. While manually driving such fasteners into a work-piece is effective, a user may quickly become fatigued when involved in projects requiring a large number of fasteners and/or large fasteners. Moreover, proper driving of larger fasteners into a work-piece frequently requires more than a single impact from a manual tool.
In response to the shortcomings of manual driving tools, power-assisted devices for driving fasteners into wood have been developed. Contractors and homeowners commonly use such devices for driving fasteners ranging from brad nails used in small projects to common nails which are used in framing and other construction projects. Compressed air has been traditionally used to provide power for the power-assisted devices. Specifically, a source of compressed air is used to actuate a cylinder which impacts a nail into the work-piece. Such systems, however, require an air compressor, increasing the cost of the system and limiting the portability of the system. Additionally, the air-lines used to connect a device to the air compressor hinder movement and can be quite cumbersome and dangerous in applications such as roofing.
Fuel cells have also been developed for use as a source of power for power-assisted devices. The fuel cell is generally provided in the form of a cylinder which is removably attached to the device. In operation, fuel from the cylinder is mixed with air and ignited. The subsequent expansion of gases is used to push the cylinder and thus impact a fastener into a work-piece. These systems are relatively complicated as both electrical systems and fuel systems are required to produce the expansion of gases. Additionally, the fuel cartridges are typically single use cartridges.
Another source of power that has been used in power assisted devices is electrical power. Traditionally, electrical devices have been mostly limited to use in impacting smaller fasteners such as staples, tacks and brad nails. In these devices, a solenoid driven by electrical power from an external source is used to impact the fastener. The force that can be achieved using a solenoid, however, is limited by the physical structure of the solenoid. Specifically, the number of ampere-turns in a solenoid governs the force that can be generated by the solenoid. As the number of turns increases, however, the resistance of the coil increases necessitating a larger operational voltage. Additionally, the force in a solenoid varies in relation to the distance of the solenoid core from the center of the windings. This limits most solenoid driven devices to short stroke and small force applications such as staplers or brad nailers.
Various approaches have been used to address the limitations of electrical devices. In some systems, multiple impacts are used. This approach requires the tool to be maintained in position for a relatively long time to drive a fastener. Another approach is the use of a spring to store energy. In this approach, the spring is cocked (or activated) through an electric motor. Once sufficient energy is stored within the spring, the energy is released from the spring into an anvil which then impacts the fastener into the substrate. The force delivery characteristics of a spring, however, are not well suited for driving fasteners. As a fastener is driven further into a work-piece, more force is needed. In contrast, as a spring approaches an unloaded condition, less force is delivered to the anvil.
Flywheels have also been used to store energy for use in impacting a fastener. The flywheels are used to launch a hammering anvil that impacts the nail. A shortcoming of such designs is the manner in which the flywheel is coupled to the driving anvil. Some designs incorporate the use of a friction clutching mechanism that is both complicated, heavy and subject to wear. Other designs use a continuously rotating flywheel coupled to a toggle link mechanism to drive a fastener. Such designs are limited by large size, heavy weight, additional complexity, and unreliability.
The foregoing advances provide increased maneuverability. Such maneuverability, however, implicates various safety issues. Specifically, as the tool becomes more portable, the tool is more likely to be transported to locations which are less safe. In such extended or precarious work sites, a substantial safety risk arises in that the natural human reflex when slipping or falling or losing balance in such precarious positions leads the operator to squeeze and grip the handle or handles of the power tool harder than usual. In many instances, operators subjected to falling or slipping actually instinctively lock onto the handle including the trigger actuator in a “death grip” type reflex action in which great force is applied to the trigger mechanism.
As a result of this tendency or reflex, an impacting device which is actuated solely by a trigger switch can be inadvertently actuated during an accident, leading to increased injuries. Additionally, mechanical switches which are typically used are subject to wear over time.
What is needed is a triggering system which can be used to control delivery of impacting force in a device which is reliable and safe and does not increase the number of mechanical switches. What is needed is a system which can be used to provide impacting force in a device using low voltage energy sources. What is further needed is a system which is reliable and does not require a continuously rotating flywheel.
In accordance with one embodiment, there is provided a device for impacting a fastener which includes a lever arm pivotable between a first position whereat a flywheel is spaced apart from a drive mechanism and a second position whereat the flywheel can contact the drive mechanism, a motor operably connected to the flywheel for storing energy in the flywheel, a trigger sensor assembly for generating a trigger signal indicative of the position of a trigger, a work contact element (WCE) sensor for generating a WCE signal indicative of the position of a WCE, a memory including program instructions, and a processor operably connected to the memory for executing the program instructions to (i) energize the motor based upon the WCE signal, and (ii) pivot the lever arm based upon the trigger signal.
In accordance with another embodiment, a method of impacting a fastener includes sensing the position of a work contact element (WCE), generating a WCE sensor signal indicative of the sensed position of the WCE, energizing a motor based upon the WCE sensor signal, transferring rotational energy from the motor to a flywheel, generating a trigger signal indicative of the position of a trigger, and pivoting the flywheel into contact with a drive mechanism based upon the trigger signal.
In accordance with a further embodiment, a device for impacting a fastener includes a lever arm solenoid configured to pivot a lever arm between a first position whereat a flywheel is spaced apart from a drive mechanism and a second position whereat the flywheel can contact the drive mechanism, a motor operably connected to the flywheel for storing energy in the flywheel, a work contact element (WCE) sensor for generating a WCE signal indicative of the position of a WCE, a memory including program instructions, and a processor operably connected to the memory for executing the program instructions to (i) energize the motor based upon the WCE signal, and (ii) energize the lever arm solenoid to pivot the lever arm to the second position based upon a trigger position.
For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and described in the following written specification. It is understood that no limitation to the scope of the invention is thereby intended. It is further understood that the present invention includes any alterations and modifications to the illustrated embodiments and includes further applications of the principles of the invention as would normally occur to one skilled in the art to which this invention pertains.
The motor 114, which is fixedly attached to the frame 112, rotatably supports a lever arm assembly 126 through a bearing 128 shown in
Continuing with
Referring to
The spring loaded switch 200 is used to provide input to a control circuit 210 shown in
Further detail and operation of the fastener impacting device 100 is described with initial reference to
As the trigger 196 presses against the spring loaded switch 200, a signal is generated and sent to the processor 212. In response to the signal, the processor 212 causes energy from the battery 214 to be provided to the motor 114 causing the output shaft 142 of the motor 114 to rotate in the direction of the arrow 230 of
The rotation of the flywheel 130 is sensed by the flywheel speed sensor 220 and a signal indicative of the rotational speed of the flywheel 130 is passed to the processor 212. The processor 212 controls the motor 114 to increase the rotational speed of the flywheel 130 until the signal from the flywheel speed sensor 220 indicates that a sufficient amount of kinetic energy has been stored in the flywheel 130.
In response to achieving a sufficient amount of kinetic energy, the processor 212 causes the supply of energy to the motor 114 to be interrupted, allowing the motor 114 to be freely rotated by energy stored in the rotating flywheel 130. The processor 212 further starts the timer 222 and controls the solenoid 124 to a powered condition whereby a pin 264 is forced outwardly from the solenoid 124 in the direction of the arrow 266 shown in
Rotation of the lever arm 126 forces the grooves 136 of the flywheel 130 into complimentary grooves 268 of the drive member 160 shown in
Movement of the drive member 160 along the drive path moves the anvil 162 into the drive channel 176 through the central bore 174 of the front bumper 168 so as to impact a fastener located adjacent to the drive section 110.
Movement of the drive member 160 continues until either a full stroke has been completed or until the timer 222 has timed out. Specifically, when a full stroke is completed as shown in
In alternative embodiments, the Hall effect sensor may be replaced with a different sensor. By way of example, an optical sensor, an inductive/proximity sensor, a limit switch sensor, or a pressure sensor may be used to provide a signal to the processor 212 that the drive member 160 has reached a full stroke. Depending upon various considerations, the location of the sensor may be modified. For example, a pressure switch may be incorporated into the front bumper 168. Likewise, the component of the drive member 160 which is sensed, such as the magnet 166, may be positioned at various locations on the drive member. Additionally, the sensor may be configured to sense different components of the drive member 160 such as the flange 164 or the anvil 162.
De-energization of the solenoid 124 allows the pin 264 to move back within the solenoid 124 as the energy stored within the springs 148 and 150 causes the springs 148 and 150 to expand thereby rotating the lever arm 126 in the direction opposite to the direction of the arrow 266 (see
The solenoid 124 and lever arm 126 are thus returned to the condition shown in
In the event that the fastener impacting device 100 is moved away from the work-piece after a fastener has been impacted and the trigger 196 has been released, the spring 188 forces the actuating mechanism 180 to return to the position shown in
In alternative embodiments, the processor 212 can accept a trigger input associated with the trigger 196 and a WCE input associated with the WCE 184. The trigger input and the WCE input may be provided by switches, sensors, or a combination of switches and sensors. In one embodiment, the WCE 184 no longer needs to interact with the trigger 196 via an actuating mechanism 180 including a pivot arm 186 and a hook portion 192. Rather, the WCE 184 interacts with a switch (not shown) that sends a signal to the processor 212 that indicates when the WCE 184 has been depressed. The WCE 184 may also be configured to be sensed rather than engaging with a switch. The sensor (not shown) may be an optical sensor, an inductive/proximity sensor, a limit switch sensor, or a pressure sensor.
In this alternative embodiment, the trigger switch can include a sensor that detects the position of the trigger such as the sensor 216 shown in
In this embodiment, the trigger sensor 216 includes a light source 256 and a photo sensor 258. The light source 256 and the photo sensor 258 are positioned such that when the stem 252 is in the position shown in
This alternative embodiment can operate in two different firing modes, which is user selectable by a mode selection switch (not shown). In a sequential operating mode, depression of the WCE 184 causes a WCE signal, based upon a switch or a sensor, to be generated. In response, the processor 212 executes program instructions causing battery power to be provided to the motor 114. The processor 212 may also energize the sensor 216 based upon the WCE signal. When the flywheel speed sensor 220 indicates a desired amount of kinetic energy has been stored in the flywheel 130, the processor 212 then controls the motor 114 to maintain the rotational speed of the flywheel 130 that corresponds to the kinetic energy desired.
If desired, an operator may be alerted to the status of the kinetic energy available. By way of example, the processor 212 may cause a red light (not shown) to be energized when the rotational speed of the flywheel 130 is lower than the desired speed and the processor 212 may cause a green light (not shown) to be energized when the rotational speed of the flywheel 130 is at or above the desired speed.
In addition to causing energy to be provided to the motor 114 upon depression of the WCE 184, the processor 212 starts a timer when battery power is applied to the motor 114. If a trigger signal is not detected before the timer times out, battery power will be removed from the motor 114 and the sequence must be restarted. The timer 222 may be used to provide a timing signal. Alternatively, a separate timer may be provided.
If the trigger 196 is manipulated, however, the processor 212 receives a trigger signal from the trigger switch or trigger sensor 216. The processor 212 then causes the supply of energy to the motor 114 to be interrupted, as long as the kinetic energy in the flywheel 130 is sufficient, allowing the motor 114 to be freely rotated by energy stored in the rotating flywheel 130. The processor 212 further starts the first timer 222 and controls the solenoid 124 to a powered condition. In response to the first of a signal from the driver block sensor 178 or timing out of the timer 222, the processor 212 is programmed to interrupt power to the solenoid 124. Both the WCE switch/sensor and the trigger switch or trigger sensor 216 must be reset before another cycle can be completed.
Alternatively, an operator may select a bump operating mode using the mode selection switch. In embodiments incorporating a trigger sensor, positioning of the selection switch in the bump mode setting causes the trigger sensor to be energized. In this mode of operation, the processor 212 will supply battery power to the motor 114 in response to either the WCE switch/sensor signal or the trigger switch/sensor signal. Upon receipt of the remaining input signal, the processor 212 verifies that the desired kinetic energy is stored in the flywheel 130 and then causes the supply of power to the motor 114 to be interrupted and the battery power is supplied to the solenoid 124. In response to the first of a signal from the driver block sensor 178 or timing out of the timer 222, the processor 212 is programmed to interrupt power to the solenoid 124.
In bump operating mode, only one of the two inputs must be reset. The processor 212 will supply battery power to the motor 114 immediately after the solenoid power is removed as long as at least one of the inputs remains activated when the other input is reset. When the reset input again provides a signal to the processor 212, the sequence described above is once again initiated.
An alternative solenoid assembly is shown in
Operation of a fastener impacting device with the solenoid assembly 280 is substantially the same as operation of the fastener impacting device 100. The main difference is that when the solenoid 282 is controlled to a powered condition, the pin 284 is pulled into the solenoid 282 thereby causing the shaft 292 to move in the direction of the arrow 308 shown in
Because the upper arm 296 of the knee hinge 290 is pivotably connected to the tongue 286 through the pin 298, and the lower arm 300 of the knee hinge 290 is pivotably connected to the frame portion 302 through the pin 304, the knee hinge 290 is forced toward an extended condition. In other words, the upper arm 296 pivots in a counter-clockwise direction about the pin 298 while the lower arm 300 pivots in a clockwise direction about the pin 304. Extension of the knee hinge 290 causes rotation of the lever arm assembly 288 about a pivot in a manner similar the rotation of the lever arm assembly 126.
An alternative solenoid mechanism is depicted in
The solenoid mechanism 310 operates in a fastener impacting device in substantially in the same manner as the solenoid mechanism 280. The main difference is that in place of a knee hinge such as the knee hinge 290, the solenoid mechanism 310 includes the sled 316. Accordingly, energization of the solenoid 312 causes the sled 316 to move across the slide 318, thereby forcing the lever arm 322 to rotate. In a further embodiment, frictional forces are reduced by providing a sled 330 with wheels 332 as shown in
While the invention has been illustrated and described in detail in the drawings and foregoing description, the same should be considered as illustrative and not restrictive in character. It is understood that only the preferred embodiments have been presented and that all changes, modifications and further applications that come within the spirit of the invention are desired to be protected.
