Power tool for orthopedic surgery

Abstract

An orthopedic surgical power tool is provided, which can be coupled with an attachment to which one or more first magnets are attached, and which comprises a power tool body with a power tool housing, an attachment mounting area connected to one end of the power tool body, a motor power transmission area projecting towards the attachment mounting area and transmitting power to the attachment, a motor driving the motor power transmission area, a first magnet sensor area including a first magnet sensor capable of detecting the magnetic field strength and the number of the first magnet(s), a control area controlling the motor to operate below a predetermined maximum speed and maximum torque value according to the magnetic field strength or number detected by the first magnet sensor, and a power supply.which supplies power to the motor and the control area, wherein the attachment mounting area includes a receiving area for receiving the attachment, the first magnetic sensor area is arranged between an outer wall of the receiving area and the power tool housing, and the receiving area includes a non-magnetic area formed in a sensing direction of the first magnetic sensor, wherein the attachment comprises an attachment body which is received in the receiving area; and a power transmission mounting area which is arranged within the attachment body and rotatable relative to the attachment body while interlocking with the motor power transmission area, and wherein the one or more first magnets are provided on the attachment body in a circumferential direction and are arranged such that they face the first magnetic sensor,while the non-magnetic area of ​​the recording area is positioned between itself and the first magnetic sensor.

Description

CROSS REFERENCE TO RELATED APPLICATIONSThis application claims priority to and the benefit of Korean Patent Application No. 10-2021-0028656, filed in the Korean Intellectual Property Office on Mar. 4, 2021, the disclosure of which is incorporated herein by reference in its entirety.BACKGROUNDTechnical FieldThe present invention relates to an orthopedic surgical power tool, and more particularly to an orthopedic surgical power tool that can be coupled to various attachments and identify the attachments coupled thereto to control a maximum speed and torque value of a motor.Prior ArtFor drilling, trimming, cutting, implanting screws for bone fusion or the like, attachments suitable for each function are attached to a surgical power tool and used, and generally, for drilling a bone, a rotation speed of 1,000 to 12,000 U / min of the power tool and a torque of 15 N cm are required, for trimming a bone, a rotation speed of 300-350 U / min and a torque of 100 N cm are required, and for cutting a bone, 10,000 to 20,000 U / min are required. Moreover, the implantation of a screw for bone fusion requires a rotation speed of 100 U / min or less and a torque of 25 to 45 N cm depending on the diameter of the screw.However, the corresponding power tool for orthopedic surgery has a fixed maximum speed and torque, and the attachment has a fixed gear ratio, and with this fixed gear ratio, there is generally a limitation on the gear ratio that can be set for each function required for each operation, because the attachments use the same transmission module.For example, when the rotational speed of the orthopedic surgical power tool is 3,600 U / min and the first-stage speed ratio of the reduction gear of the attachment is 1:3, the first speed drill attachment is set to 1,200 U / min, the second speed trim attachment is set to 400 U / min, and the third speed screw implant attachment is set to 133 U / min. In this case, the rotational speed generally exceeds the rotational speed required for each operation, and the torque is increased stepwise.In this case, there is a problem that risks and inconveniences such as bone necrosis due to the large heat due to the high rotation speed during the operation, such as drilling, trimming, cutting, implanting and the like, damage to the screw due to the high torque during the screw implantation, and the like, may occur.For example, DE 10 2011 113 126 B4 describes a medical handheld device having a power unit, wherein the power unit has a one-part or multi-part means for identifying, with which at least one feature of the medical handheld device is identified.SUMMARYThe present invention has been made to solve the above problems, and it is an object of the present invention to provide an orthopedic surgical power tool that can be coupled to a cap for each function and identifies the cap coupled thereto to control a motor to remain within a preset maximum rotational speed and a maximum torque, thereby improving related problems that may occur during orthopedic surgery.In order to achieve the above-described object, according to the present invention, an orthopedic surgical power tool is coupled to a mount to which one or more first magnets are attached, and a power tool body including a power tool housing, a mount attachment portion connected to one end of the power tool body, a motor power transmission portion protruding toward the mount attachment portion and transmitting power to the mount, a motor that drives the motor power transmission portion, a first magnetic sensor portion including a first magnetic sensor capable of detecting a magnetic field strength or number of the one or more first magnets, a control portion that controls the motor to run at a preset maximum rotational speed and a maximum torque according to the magnetic field strength or number detected by the first magnetic sensor, and a power supply, which supply the motor and the control section with current.According to the present invention, the attachment mounting portion includes a receiving portion for receiving the attachment; the first magnetic sensor portion is disposed between an outer wall of the receiving portion and the power tool housing; and the receiving portion includes a non-magnetic portion formed in a detection direction of the first magnetic sensor.Moreover, according to the invention, the attachment includes an attachment body accommodated in the accommodation portion and a power transmission fixing portion that is disposed inside the attachment body and rotatable relative to the attachment body while being interlocked with the motor power transmission portion, and the one or more first magnets are provided on the attachment body in a circumferential direction and are disposed so as to face the first magnetic sensor while the non-magnetic portion of the accommodation portion is disposed between itself and the first magnetic sensor.Moreover, the first magnetic sensor portion may be electrically connected to the control portion.Moreover, the cap attachment portion may include a sliding portion slidable relative to the receiving portion, the sliding portion may include a distal end of the sliding portion and a proximal end of the sliding portion having an inner diameter smaller than the distal end of the sliding portion, and the receiving portion may include an inner member receiving the cap therein, and a distal end of the inner member and a proximal end of the inner member having an outer diameter smaller than the distal end of the inner member, an outer member forming an annular groove in cooperation with the proximal end of the inner member, a first elastic member disposed in the annular groove in a compressed state, one end being disposed in contact with the sliding portion, and a plurality of attachment balls, which are respectively disposed in a plurality of through holes in a wall thickness direction of the inner member and movable in the wall thickness direction of the inner member.Moreover, the attachment body may have a plurality of fixing ball grooves at positions corresponding to the positions of the plurality of fixing balls, and when the attachment body is fully accommodated in the inner member such that the power transmission fixing portion is coupled to the motor power transmission portion, a portion of the fixing ball may be inserted into the fixing ball groove such that the attachment body may be fixed to the inner member, and when the sliding portion is slid from the distal end of the inner member to the proximal end of the inner member while overcoming a restoring force of the first elastic member, the fixing balls may be separated from the fixing ball grooves while moving to the distal end of the sliding portion such that the attachment body may be released from the attachment to the inner member.Moreover, when a first magnet is attached to the attachment, the control portion may control the motor to run below the preset maximum rotational speed and the maximum torque according to a magnetic field strength detected by the first magnetic sensor, and when two or more first magnets are attached to the attachment, the control portion may control the motor to run below the preset maximum rotational speed and the maximum torque according to the number of first magnets detected by the first magnetic sensor.Moreover, the power tool for orthopedic surgery may also include an operation trigger for operating or not operating the power tool.In addition, the operation trigger may include a forward rotation trigger and a reverse rotation trigger, respectively, the forward rotation trigger and the reverse rotation trigger may each include a second magnet, and when the second magnet of the forward rotation trigger is detected by a second magnetic sensor portion, the control portion may cause the motor to rotate in a forward direction, and when the second magnet of the reverse rotation trigger is detected, the control portion may cause the motor to rotate in a reverse direction.Further, the power tool body may include a forward rotation trigger groove and a reverse rotation trigger groove to receive the forward rotation trigger and the reverse rotation trigger, respectively, to be inserted therein, a forward rotation trigger spring inserted into the forward rotation trigger groove in a compressed state with one end in contact with the forward rotation trigger, and a reverse rotation trigger spring inserted into the reverse rotation trigger groove in a compressed state with one end in contact with the reverse rotation trigger.The power tool for orthopedic surgery having the above-described configuration according to the embodiments has the following effects.The power tool for orthopedic surgery can be coupled to individual attachments required for surgical surgery and also identify the coupled attachments and correspondingly control the maximum rotational speed and the maximum torque of the motor, so that it is possible to improve related problems such as the interruption of the operation due to an improper rotational speed or an improper torque.Moreover, the accommodating portion includes the non-magnetic portion formed in the detection direction of the first magnetic sensor, so that the first magnetic sensor detects the magnet of the attachment without being disturbed and accurately identifies the individual attachments.Meanwhile, although not explicitly described, the present invention also includes other effects that can be expected from the above-described configuration.BRIEF DESCRIPTION OF THE DRAWINGSThe above and other objects, features and advantages of the present invention will become more apparent to those skilled in the art from the detailed description of exemplary embodiments with reference to the accompanying drawings, in which FIG. 1 is a perspective view of an electric tool for orthopedic surgery according to an embodiment; FIG. 2 is an exploded view of a main configuration of the electric tool of FIG. 1 ; FIG. 3 is a cross-sectional view of the power tool of FIG. 1 ; FIG. 4 is a perspective cross-sectional view of the main configuration of the electric tool of FIG. 1 ; FIG. 5 shows the attachment according to an embodiment mounted to the power tool of FIG. 1 ; FIG. 6 shows that the attachment of FIG. 5 is separate from the power tool of FIG. 1 ; FIGS. 7A and 7B show a rear perspective view and a front perspective view of the attachment of FIG. 5 ; FIG. 8 is a cross-sectional view of the cap of FIG. 5 ; FIG. 9 is a cross-sectional view of the attachment and the power tool of FIG. 5 coupled together; FIG. 10 is an enlarged cross-sectional view of the main portion of FIG. 9 ; FIG. 11 shows attachments for various applications according to an embodiment; FIG. 12 shows a rearward slide portion for coupling the attachment of FIG. 5 to the power tool of FIG. 1 ; and FIG. 13 shows the attachment inserted into the electric tool of FIG. 1 in the state of FIG. 12.DETAILED DESCRIPTIONHereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings, which will be readily apparent to those skilled in the art of the present invention. The description provided herein, however, is merely an advantageous example for purposes of illustration and is not intended to limit the scope of the invention, so that it is to be understood that other equivalents and modifications are possible without departing from the scope of the invention.An orthopedic surgical power tool 100 according to an embodiment is the orthopedic surgical power tool 100 that is couplable to a cap 500 (see FIG. 7 ) to which one or more first magnets 501 are attached.As illustrated in FIG. 11, for the cap 500, a cap for trimming a bone and implanting a screw for bone fusion (FIG. 11A ), a cap for cutting a bone (FIG. 11B ), a cap for perforating a bone (FIG. 11C ), a cap for implanting wire pins (FIG. 11D ), and the like can be used. Since the above-described attachments 500 have the same main configuration as described below to be coupled to the orthopedic surgical power tool 100, an embodiment in which the bone perforating attachment (FIG. 11C ) is attached to the orthopedic surgical power tool 100 will be described as an example in this embodiment for convenience of description.As illustrated in FIGS. 1, 2, 3 to 4, the power tool 100 for orthopedic surgery includes, as main components, a power tool body 1, a cap attachment portion 2, a motor power transmission portion 3, a motor 4, a first magnetic sensor portion 5, a control portion 6, and a power supply.The power tool body 1 includes a power tool housing 11.The cap attachment portion 2 is connected to one end (the front portion, on the left side based on FIG. 3 ) of the power tool body 1. In addition, the attachment attachment region 2 includes a receiving region 21 for receiving the attachment 500.In addition, the attachment portion 2 includes a slide portion 22 that is slidable relative to the receiving portion 21.The sliding portion 22 has a substantially cylindrical shape, and includes a distal end of the sliding portion 221 and a proximal end of the sliding portion 222 having an inner diameter smaller than that of the distal end of the sliding portion 221 (see FIG. 4 ).As illustrated in FIG. 4, the accommodation portion 21 includes a non-magnetic portion 216 formed in a detection direction A of a first magnetic sensor 51 described later. As is well known, the magnetic sensor is a sensor that can measure the magnitude of a magnetic field or the magnitude and direction of a magnetic field line, the magnetic field being a vectorial physical quantity having one direction. Accordingly, the non-magnetic region 216 formed of a non-magnetic material instead of a magnetic material is provided in the detection direction A of the first magnetic sensor 51, so that the first magnetic sensor 51 can detect the magnets 501 of the attachment 500 without being disturbed.Moreover, the accommodation portion 21 includes an inner member 211, an outer member 212, a first elastic member 213, and a plurality of fixing balls 214 (see FIG. 4 ).Specifically, the inner member 211 receives the cap 500 therein, and includes a distal end of the inner member 2111 and a proximal end of the inner member 2112 having an outer diameter smaller than the distal end of the inner member 2111.The outer member 212 forms an annular groove 215 by cooperation with the proximal end of the inner member 2112.The first elastic member 213 is disposed in a compressed state in the annular groove 215 with one end in contact with the sliding portion 22.The plurality of fixing balls 214 are arranged in a circumferential direction of the inner member 211, are respectively arranged in the plurality of through holes 2113 in the wall thickness direction of the inner member 211, and are moved in a wall thickness direction of the inner member 211.The motor power transmission portion 3 protrudes from the inside of the accommodation portion 21 toward the attachment mounting portion 2 and transmits the power received from the motor 4 to the attachment 500.The motor 4 drives (rotates) the motor power transmission portion 3.The first magnetic sensor portion 5 includes the first magnetic sensor 51 that can detect the magnetic field strength or the number of the one or more first magnets 501 mounted on the attachment 500. As illustrated in FIG. 2, the first magnetic sensor region 5 includes a plurality of first magnetic sensors 51 arranged on an annular ring region 52 at predetermined intervals in the circumferential direction. In this embodiment, the first magnetic sensor region 5 includes, for example, eight first magnetic sensors 51.Meanwhile, for the first magnets 501 of the attachment 500, at least one first magnet is disposed on the attachment 500 at a position corresponding to the position of the first magnetic sensor 51.Referring to FIG. 11, by way of example, a first magnet is disposed on the bone trimming attachment and implanting a bone fusion screw (FIG. 11A ), three first magnets are disposed on the bone cutting attachment (FIG. 11B ), two first magnets are disposed on the bone perforating attachment (FIG. 11C ), and four first magnets are disposed on the wire pin implanting attachment (FIG. 11D ).Moreover, the first magnetic sensor portion 5 is electrically connected to the control portion 6.As illustrated in FIG. 4, the first magnetic sensor portion 5 is further disposed between the outer wall of the accommodation portion 21 and the inner wall of the power tool housing 11.The control section 6 controls the motor 4 below a preset maximum rotational speed (U / min) and a maximum torque (N cm) according to the strength or number of magnetic fields detected by the first magnetic sensor 51.A power supply (not illustrated) may be mounted on a power connection unit 12 located at a lower end of the power tool body 1, and may supply the required power to the motor 4 and the control portion 6 (see FIG. 12 ). The power supply may be, for example, a portable and replaceable battery.Meanwhile, as illustrated in FIGS. 7 and 8, the attachment 500 includes an attachment body 502 and a power transmission fixing portion 503 as main components. For illustration, in this embodiment, with respect to the attachment 500, the main configuration for attachment with the present power tool will be described, and the description of the already known configuration, e.g., the reduction gear attached to the power transmission attachment portion 503, and the like, irrelevant to the gist of the present invention will be omitted.As shown in FIGS. 8, 9 to 10, the attachment body 502 is accommodated in the accommodation region 21.The power transmission fixing portion 503 is disposed inside the attachment body 502 and coupled to the motor power transmission portion 3 of the electric tool 100 so as to be rotatable relative to the attachment body 502 while being interlocked with the motor power transmission portion 3. For this purpose, a bearing 505 may be disposed between the cap body 502 and the power transmission fixing portion 503.Meanwhile, the one or more first magnets 501 are provided on the attachment body 502 in the circumferential direction and arranged to face the first magnetic sensor 51 while the non-magnetic portion 216 of the accommodation portion 21 is interposed between itself and the first magnetic sensor 51.Moreover, a cap body 500 includes a plurality of fixing ball grooves 504 at positions corresponding to the positions of the plurality of fixing balls 214.When the attachment body 500 is completely accommodated in the inner member 211 of the power tool 100 such that the power transmission fixing portion 503 is coupled to the motor power transmission portion 3 of the power tool 100, a portion of the fixing ball 214 of the power tool 100 is inserted into the fixing ball groove 504, and the attachment body 500 is fixed to the inner member 211.In addition, when the sliding portion 22 slides from the distal end of the inner member 2111 to the proximal end of the inner member 2112 while overcoming the restoring force of the first elastic member 213, the fixing ball 214 can be separated from the fixing ball groove 504 while moving to the distal end of the sliding portion 221, and the cap body 500 can be relatively moved while being released from the fixing to the inner member 211.When a first magnet 501 is attached to the attachment 500, the control section 6 recognizes which type of attachment 500 is attached according to the strength of the magnetic field detected by the first magnetic sensor 51, and controls the motor 4 so as not to exceed a preset maximum rotational speed and a maximum torque. That is, when a first magnet 501 is attached to the attachment 500, the first magnets having different magnetic field strengths are used for each of the attachments 500.When two or more first magnets 501 are attached to the attachment 500, the control section 6 controls the motor 4 according to the number of the first magnets 501 detected by the first magnetic sensor 51 so that the preset maximum rotational speed and the maximum torque are not exceeded. In this case, the first magnets having the same magnetic field strength are used.In other words, when a first magnet is attached, the strength of the magnetic field may be detected, and when a plurality of first magnets are attached, the number of magnets may be detected to detect which attachments are attached and control the voltage and current values of the motor so that the motor remains below the preset value for the maximum rotational speed and the maximum torque. Since the maximum rotational speed and the maximum torque suitable for a particular surgical operation can be mechanically ensured in a simple manner, it is possible to improve the problems associated therewith, caused by relying on the experience of the user.As illustrated in FIG. 9, the orthopedic surgical power tool 100 may further include an operation trigger 8 for operating or not operating the motor 4.Specifically, the operation trigger 8 includes a forward rotation trigger 81 and a reverse rotation trigger 82, respectively. Moreover, the forward rotation trigger 81 and the reverse rotation trigger 82 include second magnets 83 and 84, respectively.When the second magnet 83 of the forward rotation trigger 81 is detected by the second magnetic sensor portion (not shown), the control portion 6 causes the motor 4 to rotate in the forward direction, and when the second magnet 84 of the reverse rotation trigger 82 is detected, the control portion 6 causes the motor 4 to rotate in the reverse direction. For example, it is possible to adjust the rotational speed and the torque of the motor by adjusting the strength of the magnetic field detected by the second magnetic sensor region according to the distance between the second magnet and the second magnetic sensor region.Meanwhile, the power tool housing 1 includes a forward rotation trigger groove 12 and a reverse rotation trigger groove 13 for accommodating the forward rotation trigger 81 and the reverse rotation trigger 82, respectively, inserted therein, a forward rotation trigger spring 811 inserted in a compressed state into the forward rotation trigger groove 12 with one end in contact with the forward rotation trigger 81, and a reverse rotation trigger spring 821 inserted in a compressed state into the reverse rotation trigger groove 13 with one end in contact with the reverse rotation trigger 82.Next, with reference to FIGS. 9, 12, and 13, the operation of the power tool for orthopedic surgery having the above-described configuration according to an embodiment will be described.The user selects the attachment 500 required for a particular surgical task. In this embodiment, the bone perforating jig 500 will be described as an example.As illustrated in FIG. 12, in order to couple the attachment 500 to the power tool 100, the slide portion 22 is moved rearward relative to the receiving portion 21. At this time, the fixing ball 214 is moved toward the distal end of the slide portion 221 having a relatively larger inner diameter to avoid interference when the cap 500 is inserted into the receiving portion 21.Next, the attachment 500 is inserted into the accommodating portion 21 so that the power transmission fixing portion 503 of the attachment 500 is coupled to the motor power transmission portion 3 of the power tool 100 (see FIG. 13 ).Next, as illustrated in FIG. 9, when the force applied to the sliding portion 22 is canceled, the sliding portion 22 is moved forward relative to the receiving portion 21 by the restoring force of the first elastic member 213. At this time, when the fixing ball 214 is brought into contact with the proximal end of the slide portion 222 with its portion protruding inside the receiving portion 21, the fixing ball 214 is coupled to the fixing ball groove 504 of the cap 500. Accordingly, the attachment 500 is fixed and limited in its movement relative to the power tool 100.At this time, the first magnetic sensor portion 5 of the power tool 100 recognizes that the number of the first magnets 501 is two, and transmits the information to the control portion 6. Then, the first magnetic sensor portion 5 can also recognize the type of the mounted attachment based on the strength of the measured magnetic field.Then, since the user is able to perform an operation while the control portion 6 controls the detected attachment 500 to run below the preset maximum rotational speed and the maximum torque, it is possible to avoid problems such as bone necrosis and the like caused by large heat due to an excessively high rotational speed that may occur when using a corresponding power tool for surgery.The present invention has been described in detail. It is to be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the scope of the invention will become apparent to those skilled in the art from this detailed description.

Claims

An orthopedic surgical power tool couplable to a mount to which one or more first magnets are attached, the power tool comprising: a power tool body having a power tool housing; a mount attachment portion connected to an end of the power tool body; a motor power transmission portion protruding toward the mount attachment portion and transmitting power to the mount; a motor that drives the motor power transmission portion; a first magnetic sensor portion including a first magnetic sensor capable of detecting a magnetic field strength or number of the one or more first magnets; a control portion that controls the motor to run at a preset maximum rotational speed and a maximum torque according to the magnetic field strength or number detected by the first magnetic sensor; and a power supply that supplies power to the motor and the control portion, wherein the attachment mounting portion includes a receiving portion for receiving the attachment, the first magnetic sensor portion is disposed between an outer wall of the receiving portion and the power tool housing, and the receiving portion includes a non-magnetic portion formed in a detection direction of the first magnetic sensor, characterized in that the attachment includes an attachment body received in the receiving portion; a power transmission fixing portion disposed within the attachment body and rotatable relative to the attachment body while being interlocked with the motor power transmission portion, and wherein the one or more first magnets are provided on the attachment body in a circumferential direction and are disposed to face the first magnetic sensor, while the non-magnetic portion of the accommodation portion is disposed between itself and the first magnetic sensor.The orthopedic surgical power tool of claim 1, wherein the first magnetic sensor portion is electrically connected to the control portion.The power tool for orthopedic surgery according to claim 1, wherein the attachment portion further has a sliding portion that is slidable relative to the receiving portion, the sliding portion includes a distal end of the sliding portion and a proximal end of the sliding portion that has a smaller inner diameter than the distal end of the sliding portion, and the receiving portion includes: an inner member that receives the cap therein and includes a distal end of the inner member and a proximal end of the inner member that has a smaller outer diameter than the distal end of the inner member; an outer member that forms an annular groove by cooperation with the proximal end of the inner member; a first elastic member that is disposed in the annular groove in a compressed state, one end being disposed in contact with the sliding portion; and a plurality of fixing balls each disposed in a plurality of through holes in a wall thickness direction of the inner member and movable in the wall thickness direction of the inner member.The power tool for orthopedic surgery according to claim 3, wherein the cap body has a plurality of fixing ball grooves at positions corresponding to the positions of the plurality of fixing balls, and when the cap body is completely accommodated in the inner member such that the power transmission fixing portion is coupled to the motor power transmission portion, a portion of the fixing ball is inserted into the fixing ball groove such that the cap body is fixed to the inner member, and when the sliding portion slides from the distal end of the inner member to the proximal end of the inner member while overcoming a restoring force of the first elastic member, the fixing balls are separated from the fixing ball grooves while moving to the distal end of the sliding portion such that the cap body can be released from the attachment to the inner member.The power tool for orthopedic surgery according to claim 1, wherein when a first magnet is attached to the attachment, the control portion controls the motor to run below the preset maximum rotational speed and the maximum torque according to a magnetic field strength detected by the first magnetic sensor, and when two or more first magnets are attached to the attachment, the control portion controls the motor to run below the preset maximum rotational speed and the maximum torque according to the number of the first magnets detected by the first magnetic sensor.The orthopedic surgical power tool of claim 5, wherein the orthopedic surgical power tool further includes an operation trigger for operating or not operating the motor.The power tool for orthopedic surgery according to claim 6, wherein the operation trigger comprises a forward rotation trigger and a reverse rotation trigger, respectively, and the forward rotation trigger and the reverse rotation trigger each have a second magnet, wherein when the second magnet of the forward rotation trigger is detected by a second magnetic sensor portion, the control portion causes the motor to rotate in a forward direction, and when the second magnet of the reverse rotation trigger is detected, the control portion causes the motor to rotate in a reverse direction.The power tool for orthopedic surgery according to claim 7, wherein the power tool body includes: a forward rotation trigger groove and a reverse rotation trigger groove for receiving the forward rotation trigger and the reverse rotation trigger, respectively, inserted therein; a forward rotation trigger spring inserted into the forward rotation trigger groove in a compressed state, one end being in contact with the forward rotation trigger; and a reverse rotation trigger spring inserted into the reverse rotation trigger groove in a compressed state, one end being in contact with the reverse rotation trigger.

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