Machine tool and method for operating a machine tool

Abstract

A machine tool and method for tightening a screw, the machine tool including a motor and a trigger, and supplying a current to the motor upon pulling of the trigger, a pattern in which the trigger is pulled is identified, and the motor can be controlled to operate in a first operating mode when the trigger is pulled according to a first pattern, or in a second operating mode when the trigger is pulled according to a second pattern.

Description

[Technical field]

[0001] A machine tool and a method for operating the machine tool to drive a screw are described herein. Also described is a hand-held power tool for enabling a screw drive operation. Generally, such hand-held tools are widely used in the construction industry. Exemplary hand-held tools within the scope of the present invention include, but are not limited to, automatic screwdrivers for driving fasteners, such as screws, into a workpiece, such as a steel or metal frame, thereby driving the fasteners, such as screws, into the workpiece. [Background technology]

[0002] Handheld power tools are known to enable screw driving operations. The tool comprises at least one machine tool housing including at least one motor that provides at least a rotational motion to a rotating shaft upon pulling of a trigger. The rotating shaft then ultimately transmits a certain torque at a certain rotational speed to a workpiece fastening element, such as a fastener, e.g. a screw. The tool may also comprise a controller for controlling the motor and continuously determining the output torque and rotational speed of the rotating shaft when the tool is in use.

[0003] Different applications may require different operating modes of the motor, such as different rotational speeds or different torques, etc. The tool may be provided with a mode switch that allows the user to switch between such different operating modes. Summary of the Invention [Means for solving the problem]

[0004] According to one aspect of the present invention, a method for operating a machine tool to fasten a screw to a workpiece along a setting axis, the machine tool includes a motor configured to provide rotational energy to the screw and a trigger configured to be pulled by a user of the machine tool, the method including: supplying current to the motor to operate the motor at a rotational speed and torque when the trigger is pulled; identifying or electronically identifying a pattern in which the trigger is pulled; controlling the motor to operate in a first operating mode when the trigger is pulled according to a first pattern; and controlling the motor to operate in a second operating mode when the trigger is pulled according to a second pattern. In some cases, the motor operates in a third operating mode when the trigger is pulled according to a third pattern. The machine tool may thereby be switched between two or more operating modes by an easily learnable operation using only one hand. Also, the cost and weight of a separate switch or additional gear stages may be avoided.

[0005] According to one aspect, the second mode of operation differs from the first mode of operation with respect to at least one of a voltage of the current supplied to the motor, a maximum amperage of the current supplied to the motor, a maximum rotational speed of the motor, and combinations thereof.

[0006] According to another aspect, the second pattern differs from the first pattern with respect to at least one of a distance traveled by the pull operation, a speed of the pull operation, a duration of the pull operation, a number of pull operations within a predetermined time interval, a time interval between two pull operations, a frequency of the pull operations, and combinations thereof.

[0007] According to another aspect, the method further comprises storing in which operating mode the motor is controlled to operate and defining such mode as a first operating mode for a subsequent execution of the method. According to a preferred aspect, the stored operating mode of a previous execution of the method is used as the first operating mode and the operating mode immediately following the stored operating mode within a predefined cyclic sequence of operating modes is used as the second operating mode.

[0008] According to another aspect, a machine tool for fastening a screw into a workpiece along an installation axis includes a motor configured to provide rotational energy to the screw; a trigger configured to be pulled by a user of the machine tool; and a controller that supplies current to the motor such that pulling the trigger causes the motor to operate at a rotational speed and torque, identifies a pattern in which the trigger is pulled, and controls the motor to operate in a first operating mode when the trigger is pulled according to the first pattern and to operate in a second operating mode when the trigger is pulled according to the second pattern.

[0009] According to one aspect, the controller is further configured to do one or more of: electronically determine a pattern in which the trigger is pulled; control the motor to operate in a third operating mode if the trigger is pulled according to a third pattern; store which operating mode the motor is controlled to operate in and define such mode as a first operating mode for subsequent executions of the method; and use the stored operating mode as the first operating mode and the operating mode immediately following the stored operating mode in a predetermined cyclical order of the operating modes as the second operating mode.

[0010] According to one aspect, the machine tool includes a push switch arranged to generate a push signal when a force is applied to the shaft along the installation axis towards the machine tool, The controller may be arranged to receive the push signal and to start the motor upon receipt of the push signal.

[0011] Further aspects and advantages of the machine tool, associated components and its method of use will become apparent from the following description, given by way of example only and with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 shows a machine tool of the present invention. [Diagram 2]FIG. 13 is an exemplary diagram illustrating the profile of the distance a trigger travels over time. [Diagram 3] FIG. 4 is a diagram illustrating an example of the characteristics of the rotation speed of a motor over time. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] FIG. 1 shows a machine tool 100 for fastening a screw into a workpiece (not shown). In the embodiment shown, the machine tool 100 is a hand-held power tool such as an automatic screwdriver. The machine tool 100 comprises a housing 105, a motor 110 with a shaft 120 enclosed by the housing 105, a trigger 130, a controller 140 formed as a microcomputer and also with a data storage 145, which is a computer memory, a battery 150, and a communication unit 155, which is a radio transmitter. The controller 140 supplies a current from the battery 150 to the motor 110 to drive the shaft 120 in rotation. The machine tool 100 further comprises a gear 160 and a spindle 170 with a screwdriver 175, such as a hexagonal driver, which is driven by the shaft 120 via the gear 160. The length of the spindle 170 provides the mounting axis along which a screw is fastened into a workpiece.

[0014] Furthermore, the machine tool 100 comprises a rotation speed sensor 180 for detecting the rotation speed of the motor 110 and an amperage / voltage sensor 190 for detecting the amperage and / or voltage of the current supplied to the motor 110. The amperage of the motor 110 can be used as a parameter representative of the torque transmitted to the screw. Furthermore, the machine tool 100 comprises lines 195 connecting the controller 140 with the motor 110, the switch 130 and the sensors 180, 190 for transmitting current to the motor 110 and / or collecting electrical signals from the trigger 130 and / or the sensors 180, 190. Additionally or alternatively, the controller 140 may use information already present from controlling the rotational movement of the motor 110, e.g. the number of electrical commutations over time versus the rotation speed, to obtain data regarding the rotation speed, amperage or voltage of the motor 110.

[0015] The housing 105 includes a grip section 106 for manually gripping the machine tool 100 by a user such that a trigger 130 can be pressed by the user's index finger. The trigger 130 can signal its switch position via line 195 to the controller 140, which electronically uses the switch position of the trigger 130 to electronically determine the pattern in which the trigger 130 is pulled. When the trigger 130 is pulled by the user, the motor 110 is supplied with current according to the pattern determined by the controller 140.

[0016] 2 shows a schematic diagram of a profile 200 of the distance 205 that a trigger, such as the trigger 130 shown in FIG. 1, travels over time during a fastening process. While being pulled by a user in a first pull, the trigger moves from a start position 210, where the trigger is not pulled at all, to an end position 220, which corresponds to a stop limit where the trigger is fully pulled. The trigger may be spring-loaded to its start position 210. After some time, e.g., a few hundred milliseconds, the user releases the trigger, and the trigger moves back towards its start position 210. Just before the trigger reaches its start position 210, the user pulls the trigger to its end position 220 in a second pull. The trigger is then always held in its end position, e.g., to drive a screw into a workpiece.

[0017] The trigger pull pattern may be characterized in several ways: pull distance traveled, such as a percentage of the distance between a start position and an end position; pull speed, such as the slope of the distance 205 over time as shown in FIG. 2; pull duration, such as along the horizontal axis of FIG. 2; number of pulls within a given time interval (two pulls are shown in FIG. 2); time interval between two pulls, such as along the horizontal axis of FIG. 2; frequency of pulls, such as along the horizontal axis of FIG. 2; or combinations thereof. Such trigger pull patterns are determined by a controller, such as controller 140 shown in FIG. 1. The patterns may be determined physically, i.e., by using one or more sensors, or electronically, i.e., by executing a software algorithm.

[0018] FIG. 3 shows a schematic diagram of a characteristic 300 of a parameter 305 of an operating motor, such as the motor 110 shown in FIG. 1, over time during a fastening process. The parameter 305 may be the voltage of the current supplied to the motor, the maximum amperage of the current supplied to the motor, the maximum rotational speed of the motor, or a combination thereof. A controller, such as the controller 140 shown in FIG. 1, changes the value of the parameter 305 with changes in the position 205 of the trigger, as shown in FIG. 2. In the illustrated embodiment, the parameter 305 rises from 0 to a first maximum value 310 (first operating mode) upon a first pull. At this time, the controller recognizes only one pull (first pattern). When the trigger is released, the parameter 305 decreases toward 0. Upon a second pull within a certain time interval, the controller recognizes two pulls (second pattern) within a given time interval and switches to a second operating mode in which the parameter rises to a second maximum value 320 that is less than the first maximum value 310. Additionally, the controller may switch to a third mode of operation in which upon a third pull within the same time interval, the parameter 305 increases to a third maximum value.

[0019] In some embodiments, the controller is further configured to store in which operating mode the motor is controlled to operate and define such mode as a first operating mode for a subsequent execution of the method. The controller may further be configured to use the stored operating mode as the first operating mode and to use an operating mode immediately following the stored operating mode in a predetermined cyclical order of the operating modes as a second operating mode.

[0020] Throughout this application, "current supplied to the motor" is meant to include the current measured in a power supply, such as a battery, if the hand held power tool is a battery operated tool.

[0021] The foregoing description of the embodiments of the present invention has been presented for purposes of illustration and description. This description is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the present invention. The described functionality may be distributed among modules differing in the number and distribution of functionality from that described herein. In addition, the order of performing the functions may vary depending on the embodiment. The embodiments were selected and described as practical applications of the present invention in order to explain the principles of the invention and to enable those skilled in the art to utilize the invention in various forms and with various modifications as may be suitable for the particular use intended. The scope of the present invention is defined by the claims appended hereto and their equivalents.

Claims

1. 1. A method for operating a machine tool to fasten a screw to a workpiece along a setting axis, the machine tool including a motor configured to provide rotational energy to the screw and a trigger configured to be pulled by a user of the machine tool, the method comprising: - pulling the trigger supplies current to the motor to operate it at a certain rotational speed and torque; - Identifying a pattern in which the trigger is pulled; - controlling the motor to operate in a first operating mode when the trigger is pulled according to a first pattern; and - controlling the motor to operate in a second operating mode when the trigger is pulled according to a second pattern; Includes method.

2. 2. The method of claim 1, wherein the second mode of operation differs from the first mode of operation with respect to at least one of a voltage of the current supplied to the motor, a maximum amperage of the current supplied to the motor, a maximum rotational speed of the motor, and combinations thereof.

3. 3. The method of claim 1 or 2, wherein the second pattern differs from the first pattern with respect to at least one of a distance traveled by a pull operation, a speed of a pull operation, a duration of a pull operation, a number of pull operations within a predetermined time interval, a time interval between two pull operations, a frequency of pull operations, and combinations thereof.

4. The method of any one of claims 1 to 3, wherein the pattern in which the trigger is pulled is specified electronically.

5. The method of any one of claims 1 to 4, further comprising controlling the motor to operate in a third operating mode when the trigger is pulled according to a third pattern.

6. 6. The method of claim 1, further comprising storing in which operating mode the motor is controlled to operate and defining such mode as the first operating mode for subsequent executions of the method.

7. 7. The method of claim 6, wherein a stored operating mode of a previous execution of the method is used as the first operating mode and an operating mode immediately following the stored operating mode in a predetermined cyclical ordering of operating modes is used as the second operating mode.

8. 1. A machine tool for fastening a screw along an installation axis into a workpiece, comprising: a motor configured to provide rotational energy to said screw; a trigger adapted to be pulled by a user of the machine tool; a controller configured to supply current to the motor to cause it to operate at a rotational speed and torque upon pulling of the trigger, to identify a pattern in which the trigger is pulled, and to control the motor to operate in a first operating mode if the trigger is pulled according to a first pattern and to control the motor to operate in a second operating mode if the trigger is pulled according to a second pattern; Equipped with Machine tools.

9. The controller further comprises: - electronically determining the pattern in which the trigger is pulled; - controlling the motor to operate in a third operating mode if the trigger is pulled according to a third pattern; - storing in which operating mode the motor is controlled to operate and defining said mode as said first operating mode for subsequent executions of the method; and - using a stored operating mode as said first operating mode and using as said second operating mode the operating mode immediately following said stored operating mode within a predefined cyclic sequence of operating modes; The machine tool of claim 8 configured to perform one or more of the following:

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