Patent Application
20240017334
Example embodiments generally relate to power tools for drilling operations and, in particular, relate to a positive feed drill with liftoff protection.
Power tools are commonly used across all aspects of industry and in the homes of consumers. Power tools are employed for multiple applications including, for example, drilling, tightening, sanding, and/or the like. Handheld power tools are often preferred, or even required, for jobs that require a high degree of freedom of movement or access to certain difficult to reach objects. However, other power tools, which are employed in contexts that require high degrees of accuracy, may be affixed to either the surface of a workpiece or to a fixture that attaches to the workpiece in order to ensure greater accuracy. A positive feed drill is an example of such a device.
In some specific industries, such as, but not limited to the aerospace industry, the operation and use of power tools for making precision holes in a structure may be a key part of an assembly process. Positive feed drills are often used in these contexts, and may be attached to the structure (e.g., an aluminum workpiece that forms part of the fuselage of an aircraft), or to a fixture that attaches to the structure.
To affix the positive feed drill to a structure, various attachment mechanisms may be employed. However, if the attachment mechanism fails or is improperly installed, the performance of the positive feed drill can deteriorate or certain operational limits may be exceeded. As a result, the positive feed drill may push away from the structure or may separate from a fixture. This can cause oversized holes, damage to tools, or other problems.
In an example embodiment, a power tool is provided. The power tool may include a motor powered, a controller configured to control operation of the motor, a drill assembly configured to control operation of a cutter with respect to a workpiece responsive to operation of the motor, and a liftoff protection assembly. The liftoff protection assembly may be configured to detect a trigger event associated with movement of the power tool relative to the workpiece, and initiate a protective action for the power tool responsive to the trigger event.
In another example embodiment, a method of controlling a positive feed drill is provided. The method may include arranging a positive feed drill proximate to a workpiece in a fixed location relative to the workpiece, detecting a trigger event based on a change in locational relationship between the positive feed drill and the workpiece, and, in response to the trigger event, initiating a protective action relative to operation of the positive feed drill.
Having thus described some example embodiments in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:
Some example embodiments now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all example embodiments are shown. Indeed, the examples described and pictured herein should not be construed as being limiting as to the scope, applicability or configuration of the present disclosure. Rather, these example embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like reference numerals refer to like elements throughout. Furthermore, as used herein, the term “or” is to be interpreted as a logical operator that results in true whenever one or more of its operands are true. As used herein, operable coupling should be understood to relate to direct or indirect connection that, in either case, enables functional interconnection of components that are operably coupled to each other.
As indicated above, separation of a power tool, such as a positive feed drill, from the structure (or fixture) to which it is attached can be problematic. To date, industry response to this problem has been to avoid such separation by increasing the holding power of attachment assemblies. In other words, stronger clamping mechanisms have generally been developed in order to prevent such separation. However, merely forcibly holding the drill in place can cause load limits for the tool itself to be reached. Thus, stronger clamping cannot be seen as a panacea for solving these problems. Some example embodiments may provide a way to detect when a positive feed drill has lost contact with a structure to which it is affixed, or has moved position in the fixture to which it is attached. Either of these situations may be detected as a trigger event. Responsive to detection of the trigger event, example embodiments may further implement a protective action with respect to continued operation of the positive feed drill (or other power tool). The protective action may include, for example, turning off the power tool, retracting the power tool, or returning the power tool to another safe position or condition. Accordingly, example embodiments may enable detection of situations where the power tool is losing contact with the workpiece or coming out of a fixture, and prescribe a protective action when such situations are detected.
The drill assembly 140 may include a spindle, gearing, chuck and/or the like, all of which may be configured to enable the drill assembly 140 to drive a cutter 142 relative to a workpiece 150. The power tool 100 may be operably coupled to the workpiece 150 in a manner that is intended to fix the position and location of the power tool 100 relative to the workpiece 150 and/or a hole or opening being formed in the workpiece 150 responsive to operation of the power tool 100. To accomplish this fixing, an attachment assembly 160 may be provided.
The attachment assembly 160 may, in some cases, be a fixture that is attached to the workpiece 150. The fixture may be attached to the workpiece 150 via one or more previously drilled holes in the surface of the workpiece 150, or via other means. Alternatively, the attachment assembly 160 may include any means or device (apart from the fixture mentioned above) that operably couples the power tool 100 to the workpiece 150. The attachment assembly 160 may, for example, directly couple a nose or end face of the power tool 100 (or drill assembly 140) to the workpiece 150 via attachment to a previously drilled hole, or via other fixing means.
In an example embodiment, the power tool 100 may further include a liftoff protection assembly 170 of an example embodiment. The liftoff protection assembly 170 may be configured to detect a trigger event and, responsive to detection of the trigger event, the liftoff protection assembly 170 may be configured to implement a protective action for the power tool 100. The trigger event may include detection of a loss of contact (or losing such contact) between the power tool 100 and either the workpiece 150 or the attachment assembly 160 (e.g., fixture). The protective action may include, for example, turning off the motor 120 (e.g., via the controller 130, cutting power from the power source 110, or by direct intervention with the motor 120). However, as an alternative, the protective action may include retraction of the spindle and the cutter 142. In some cases, stopping of the motor 120 may be initiated after such retraction (thereby combining the two aforementioned examples of protective actions). In another alternative, which may be combined with other actions, or initiated alone, the protective action may include shifting the controller 130 to a different mode of operation in order to place the power tool 100 in a safe condition, or stop the power tool 100 in a phased or stepped approach to bring the power tool 100 to a safe stop.
Both the sealing interface 200 and the control valve 210 may be exposed to air supply 230 associated with operation of the power tool 100. The control valve 210 may be contact or non-contact type valve that can be normally open or normally closed (depending on the architecture or system design employed). The control valve 210 may be configured to be operable responsive to a change in the sealing state at the sealing interface 200. When operated (e.g., based on a loss of the seal at the sealing interface 200), the control valve 210 may cause the controller 130 (or motor) to initiate a protective action.
In this regard, for example, if the sealing interface 200 is compromised due to movement of the power tool 100 relative to the fixture or the surface of the workpiece 220, the sealing interface 200 may be configured to lose its sealing capability, and such loss of sealing capability may be detected by the control valve 210. The detection of the loss of sealing capability of the sealing interface 200 may therefore be a trigger event that is detected at the control valve 210. The detection of the trigger event by the control valve 210 may then change a state of the control valve 210 to cause the control valve 210 to provide an input to the controller 130 (or directly to the motor 120 or cut off power from the power supply 110) to initiate the protective action for the power tool 100.
The sealing interface 200 of
When the power tool 100 is operated, the controller 130 of
If the power tool 100 moves relative to the fixture or workpiece, the template boss 320 may lose its seal. When the seal is broken or lost at the template boss 320, air may escape from the charging line 324 and pressure in the charging line 324 may be reduced. The reduction in pressure in the charging line 324 may actuate (or activate) the actuator 310 and cause the closed switch position between terminals 1 and 2 to shift to an open position, thereby connecting terminal 1 to terminal 2. The connection of terminal 1 to terminal 2 enables the motor running air to pass through the check valve 340 and trigger a protective action. Thus, the breaking of the seal of the template boss 320 is detected by the three way pneumatic control valve 300 as a trigger event, and the trigger event causes the three way pneumatic control valve 300 to initiate the protective action by taking a passageway (from terminal 1 to terminal 2) that was blocked, and opening or unblocking the passageway to allow air to flow through and initiate the protective action.
The three way pneumatic control valve 300 of this example is a normally open valve (i.e., open so that the passageway from terminal 1 to terminal 2 is not formed, or is blocked). However, as noted above, it may also be possible to implement a circuit that uses a normally closed valve. The actuation of the actuator 310 on low pressure could similarly be reversed to initiate on a high pressure. It may also be possible to implement a circuit that uses normally open or normally closed two way valves. It may also be possible to eliminate the template boss 320 and charging line 324 and allow actuator 310 to directly contact the workpiece. In such an example, the actuator itself may contact the workpiece thereby providing a mechanical system (instead of the pneumatic system described in the example of
Accordingly, example embodiments may provide the ability to detect an movement of a positive feed drill after it has been clamped or otherwise fixed in place relative to a workpiece (e.g., via a fixture). When such movement is detected, the drill may be returned to a safe and/or stopped position to avoid damage to either the workpiece or the drill itself.
A power tool (e.g., a positive feed drill) of an example embodiment may include a power source (e.g., electric or pneumatic), a motor powered from the power source, a controller configured to control operation of the motor, a drill assembly configured to control operation of a cutter with respect to a workpiece responsive to operation of the motor, and a liftoff protection assembly. The liftoff protection assembly may be configured to detect a trigger event associated with movement of the power tool relative to the workpiece, and initiate a protective action for the power tool responsive to the trigger event.
In some embodiments, additional optional features may be included or the features described above may be modified or augmented. Each of the additional features, modification or augmentations may be practiced in combination with the features above and/or in combination with each other. Thus, some, all or none of the additional features, modification or augmentations may be utilized in some embodiments. For example, in some cases, the liftoff protection assembly may include a sealing interface and a control valve. The sealing interface may be configured to form a breakable seal at a surface of the workpiece or a fixture attached to the workpiece. The seal may be broken responsive to movement of the power tool relative to the workpiece. The control valve may be configured to detect the trigger event based on a status of the sealing interface and initiate the protective action responsive to the trigger event. In an example embodiment, the sealing interface may include a template boss configured to prevent air passage when the seal is not broken and to release air responsive to breaking the seal at the surface of the workpiece or the fixture attached to the workpiece. In some cases, the control valve may include a three way pneumatic control valve. In an example embodiment, the three way pneumatic control valve may include a normally blocked air passageway and may be configured, responsive to detecting the trigger event, to unblock the passageway to define an airflow for initiating the protective action. In some cases, the three way pneumatic control valve may include an actuator operably coupled to a charging line. Actuation of the actuator may define the trigger event, and the actuator may be configured to be actuated responsive to a change in air pressure in the charging line. In some cases the charging line may be eliminated an the pneumatic control valve my directly detect the trigger event. In an example embodiment, the protective action may include stopping the motor, removing the cutter from the workpiece, removing the cutter from the workpiece and then stopping the motor, or changing an operational mode of the power tool during extraction of the cutter from the workpiece. In some cases, the liftoff assembly may include a pneumatic circuit configured to detect the trigger event as a change in pressure, and initiate the protective action by initiating control of the motor.
Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Moreover, although the foregoing descriptions and the associated drawings describe exemplary embodiments in the context of certain exemplary combinations of elements and/or functions, it should be appreciated that different combinations of elements and/or functions may be provided by alternative embodiments without departing from the scope of the appended claims. In this regard, for example, different combinations of elements and/or functions than those explicitly described above are also contemplated as may be set forth in some of the appended claims. In cases where advantages, benefits or solutions to problems are described herein, it should be appreciated that such advantages, benefits and/or solutions may be applicable to some example embodiments, but not necessarily all example embodiments. Thus, any advantages, benefits or solutions described herein should not be thought of as being critical, required or essential to all embodiments or to that which is claimed herein. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2021/054273 | 10/8/2021 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 63089852 | Oct 2020 | US |
