JP2010131249A - Massaging chair equipped with foot massaging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable a user to keep a relaxed posture to sprawl feet out forward in using a foot massaging device in a massaging chair. <P>SOLUTION: An advancing and retreating mechanism 15 continuously connected to the foot massaging device 5 is provided below a seat part 2. When the mechanism 15 makes an advancing movement to the front, the foot massaging device 5 floats in midair from a floor surface in the front of the seat part 2 and proceeds to a using position U being a position to massage lower limbs of the user. When the mechanism 15 makes a retreating movement to the back, the foot massaging device 5 is housed in a housing position P formed below the seat part 2. The mechanism 15 includes a link 20 which retains the foot massaging device 5 to rock forward and backward and a bridging link 50 which bridges between a middle part of the link 20 and a back surface part of the foot massaging device 5, is rotatable relative to the link 20 and the back surface part of the foot massaging device 5, and is slidable along the back surface of the foot massaging device 5. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a massage chair provided with a foot massage device.

As a massage chair provided with a foot massage device, for example, there is one disclosed in Patent Document 1.
This massage chair has a backrest part at the back of the seat part and a foot massage device at the front part, and the backrest part is equipped with a massage mechanism that massages the user's back part. It has a built-in lower limb massage mechanism that massages the lower limbs of a person. Further, the backrest portion can be reclined back and forth, and the footpad device is swingably provided in front of the seat portion via a support member.

Such a massage chair is not only used for performing a massage but also often used as a mere chair. In particular, this type of massage chair often has a soft cushion built into the seat, etc., and since the backrest has a reclining function, it is suitable for use as a sofa. Yes.
However, the foot massage device of Patent Document 1 has a holding groove formed on the front surface thereof, so that even if the massage function is not used, the lower limb must be fitted into the holding groove, thereby freeing the foot. Movement was restricted and it was difficult to have a comfortable posture. It also contributed to the loss of the appearance of the chair.

Therefore, in order to avoid such inconvenience, the applicant of the present application has already developed a technique such as Patent Document 2.
This massage chair has a push-pull mechanism that can move the foot massage device between a use position and a built-in position below the seat, and the push-pull mechanism is installed on both sides of the massage chair. A guide rail, a push / pull rod that moves in and out along the guide rail, and a carriage plate coupled to the push / pull rod are connected to the foot plate by a pin.
Therefore, after the foot massage device is located at the use position, the front (massage surface) and the rear surface (foot rest surface) of the foot massage device can be freely switched.
JP 2002-238963 A JP 2007-75590 A

However, the configuration employing the guide rail requires high precision and careful processing in that a smooth bend is formed on the guide rail, and has a feature that it is difficult to reduce the manufacturing cost.
In addition, due to the occurrence of sliding resistance against the guide rail, strong driving is required, but on the other hand, it is necessary to devise measures to suppress driving noise and vibration. There was room for improvement, such as increasing the burden.
As another need, when using a foot massage device, there is a desire to take a relaxed posture (a posture with the knee extended as much as possible) such that the user throws the foot forward.

  SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a massage chair that can solve the simplification, weight reduction, and cost reduction of the structure at once. In addition, an object of the present invention is to provide a massage chair that enhances the feeling of use by allowing the user to take a relaxed posture such as throwing the foot forward when using the foot massage device. And

In order to achieve the above object, the present invention takes the following technical means.
That is, the massage chair provided with the foot massage device according to the present invention is a massage chair having a seat portion, a backrest portion provided at the rear portion of the seat portion, and a foot massage device installed at the front portion of the seat portion. When the advancing / retreating mechanism is provided below the seat portion and connected to the footrest device, and the advancing / retreating mechanism moves forward, the footgrip device floats above the floor surface in front of the seat portion and lifts the user's lower limb. When the advancing / retreating mechanism moves backward, the foot massaging device is housed in a housing position formed below the seat portion when it moves to a use position that is a massageable position.

Specifically, the foot grinder in the use position has a back surface facing the floor and a bottom surface facing forward, and the foot grinder in the storage position has a bottom surface facing forward. It is in a state where it is substantially flush with the front end of the seat and the front of the lower limb is massaged upward.
The advancing / retreating mechanism advances the rear upper portion of the foot grinder in the storage position forward from the front end of the seat, and then advances further while moving it up to bring the foot grinder to the use position. The foot kneading device is lowered by retracting the back upper part of the foot kneading device in the use position backward while lowering the front upper part of the foot kneading device below the seat part and then retreating below the seat part. The retraction operation for returning to the storage position can be performed.

  Specifically, the advancing / retreating mechanism is connected between a stationary pivot provided at the lower part of the seat and a movable pivot provided at the upper back of the foot grinder so that the movable pivot is moved forward and backward with the stationary pivot as a fulcrum. A link that is swingably held, a swing drive unit that applies a driving force for swinging back and forth with respect to the link, and a roll that is provided at the lower back end of the foot grinder so as to be movable on the floor. It is spanned between the driving wheel, the intermediate part of the link and the back part of the foot-greasing device, and is rotatable with respect to the link and the rear part of the foot-gripping device and slidable along the back surface of the foot-gear device. And when the link swings to the rear side of the swinging area of the link, the foot grinder moves to the storage position, and the link moves to the swinging area of the link. If you swing forward, the foot grinder moves to the working position. It can be configured to.

In this case, a back support frame composed of a lower slide frame and an upper slide frame that are slidable with each other is provided on the back surface portion of the foot massage device, and the foot massage device is attached to the lower slide frame, It is preferable that the erection link is pivotally connected, a moving pivot is provided at an upper end portion of the upper slide frame, and a tip end portion of the link is pivotably connected.
The link is preferably formed of a single member that connects a stationary pivot provided at the center in the left-right direction of the seat and a movable pivot provided at the center in the left-right direction of the foot massage device. is there.

Furthermore, it is preferable that the link is formed in a shape that curves in a C-shaped side view along the top from the front upper part of the foot gripping device when the foot gripping device is located at the storage position. .
The swing drive part of the advance / retreat mechanism may have an expansion / contraction mechanism driven by an electric motor.

  According to the massage chair according to the present invention, further simplification, weight reduction, and cost reduction of the structure can be solved at a stretch. In addition to the massage chair according to the present invention, when the foot massage device is used, the user can take a relaxed posture by throwing his / her foot forward to enhance the feeling of use.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1-12 has shown one Embodiment of the massage chair 1 which concerns on this invention. FIG. 12 is an overall external view, and in other drawings, a part of the structure is omitted as necessary for convenience of explanation.
The massage chair 1 has a seat portion 2 and a backrest portion 3 provided at the rear portion of the seat portion 2, and a lower limb of a user seated on the seat portion 2 is located at the front portion of the seat portion 2. A foot massaging device 5 for massaging (especially calves) is provided.

As shown in FIGS. 1 and 2, a leg frame 6 for installing the massage chair 1 on the floor surface F is provided at the lower portion of the seat 2, and the seat 2 is predetermined by the leg frame 6. Being supported by height.
Further, armrests 7 are provided so as to sandwich both sides of the seat portion 2 (see FIG. 12), and the leg frames 6 are hidden by these armrests 7 so that they cannot be seen from the outside.
In the following description, the left-right direction in FIG. 1 is referred to as the front-rear direction in the actual apparatus, and the up-down direction in FIG. 1 is referred to as the up-down direction in the actual apparatus. 1 is referred to as a horizontal direction or a width direction in an actual apparatus. These directions coincide with those seen from the user sitting on the massage chair 1.

The seat portion 2 is wide enough to support the user's buttocks from below. The lower part of the backrest part 3 is pivotally supported so that it can swing back and forth with respect to the rear part of the seat part 2 or the rear part of the leg frame 6. The backrest 3 can be reclined by a reclining mechanism (not shown) such as a linear actuator mechanism disposed in the leg frame 6.
Inside the backrest 3, a back massage mechanism (not shown) that performs massage operations such as squeezing, striking, or vibrating is provided so as to be movable up and down.
The foot massage device 5 has a substantially square shape when viewed from the front, and a box shape that exhibits a rounded triangular shape when viewed from the side. A pair of left and right holding grooves 10, 10 that allow the user's lower limbs (left and right feet) to be fitted are formed in front of the foot massage device 5.

A massage device for the lower limb that massages the lower limbs is incorporated in the inner facing surfaces of the holding grooves 10 (both sides that sandwich one of the inserted legs). This lower limb massage device is configured to itch by swinging a plate that is long in the length direction of the foot left and right, or to be squeezed with an air bag that expands and contracts by air supply and discharge. Can do.
The foot massaging device 5 floats in the air from the floor F in front of the seat 2 and can be used to massage the user's lower limbs (see FIG. 2), and the storage formed below the seat 2. It can move between positions P (see FIG. 1).

That is, an advance / retreat mechanism 15 is provided below the seat portion 2 (inside the leg frame 6), and the seat portion 2 side (leg frame 6) and the foot kneading device 5 are connected via the advance / retreat mechanism 15. It becomes the composition which is done. When the advance / retreat mechanism 15 moves forward, the foot kneading device 5 advances to the use position U, and when the advance / retreat mechanism 15 moves backward, the foot kneading device 5 is stored in the storage position P. It has become a thing.
6 shows the storage state (storage position P) of the foot massage device 5, FIG. 10 shows the use state (use position U) of the foot massage device 5, and FIGS. 7 to 9 show switching between the storage state and the use state. Is shown (halfway state). As is clear from FIGS. 6 to 10, the advance / retreat mechanism 15 includes a link 20, a swing drive unit 21, a rolling wheel 22, and an erection link 50 (extrusion link).

In addition, when moving the installation place of this massage chair 1 as a whole to the leg frame 6 which supports the seat part 2, in order to be able to move lightly, a floor surface installation part (foot massage device 5) is used. A pair of left and right moving wheels 23 are provided with respect to the rear end of the bottom surface. In addition, when the massage chair 1 is not used, such as when the massage chair 1 is not moved, the moving wheels 23 are lifted from the floor surface F, and are placed at four locations on the front, rear, left and right of the floor surface installation portion in order to maintain the installation stability. A member 24 is provided.
The flooring member 24 is preferably formed of hard rubber or the like that has both vibration absorption and resistance to slipping on the floor surface F. When the installation location of the massage chair 1 is moved, the entire chair is tilted backward (the chair front part is lifted) so that only the left and right moving wheels 23 are pressed against the floor surface F, and all the landing members 24 are thus moved. May be moved while rolling the moving wheel 23 so as to move away from the floor surface F.

On the other hand, the foot massaging device 5 is supported by the moving frame 28 in which the bottom support frame 26 and the back support frame 27 are assembled so as to exhibit an L shape in a side view so that the rigidity of the entire device is maintained.
As shown in FIG. 11, the back support frame 27 has a configuration in which a slide outer frame 65 (lower slide frame) and a slide inner frame 66 (upper slide frame) are slidably combined with each other. The bottom support frame 26 is coupled to the distal end of the slide outer frame 65, and the base end side (upper end side) of the slide inner frame 66 is connected to the link 20.
The link 20 includes a stationary pivot portion 32 provided at the lower portion of the seat portion 2 (upper side in the leg frame 6) and a movable pivot portion 33 provided at the upper rear portion of the foot massage device 5 (upper end portion of the slide inner frame 66). It is connected between.

The stationary pivot portion 32 and the movable pivot portion 33 are configured to hold the link 20 so as to be relatively rotatable around a pivot axis whose axis is directed in the left-right direction. Therefore, from the viewpoint that the foot massaging device 5 operates with respect to the seat portion 2, the link 20 is configured such that the movable pivot portion 33 is swingable in the front-rear direction with the stationary pivot portion 32 as a fulcrum. is there.
As shown in FIGS. 3 to 5, the stationary pivot part 32 is provided at the center part in the left-right direction of the seat part 2, and the movable pivot part 33 is provided at the center part in the left-right direction of the foot massage device 5. Yes. Accordingly, the link 20 that connects the stationary pivot portion 32 and the movable pivot portion 33 is formed by only one.

As is clear from FIG. 5, the link 20 is formed in a highly rigid frame shape by connecting two link-composing rods 34 in parallel in the left-right direction at a predetermined interval and connecting them together. The number of the link configuration rods 34 is not particularly limited, but a single link 20 is provided as a structure in which the entirety is assembled in a frame shape. That is, the link 20 is composed of a single bar member.
Further, the link 20 is formed in a shape that curves in a side view C-shape. That is, when the foot massaging device 5 is described as being in the storage position P below the seat portion 2 (the state of FIG. 6), the link 20 is once extended backward from the stationary pivot portion 32, and thereafter The foot kneading device 5 is U-turned downward so as to go around from the upper front to the upper rear side through the top, and further extends forward and then reaches the moving pivot 33.

As shown in FIG. 6, when considering a virtual circle D having a maximum radius R that is a straight line connected from the axial center of the stationary pivot 32 to the floor surface F, the link 20 is centered on the stationary pivot 32. The size of the imaginary circle D is such that it is entirely within the range of the virtual circle D. Therefore, even if the link 20 swings back and forth around the stationary pivot 32, the link 20 does not contact the floor surface F.
The link 20 is located behind the movable swing range when the foot massage device 5 is located at the storage position P (FIG. 6), and is movable when the foot massage device 5 is located at the use position U (FIG. 10). Swing back and forth so as to be in front of the moving range. The movable swing range refers to a region where the link 20 swings when the foot massaging device 5 moves between the storage position P and the use position U.

The erection link 50 is provided between a base pivot part 51 provided in the middle part of the link 20 and a front part pivot part 52 provided on the back part of the foot massage device 5 (specifically, on the upper side of the slide outer frame 65). It is pivotally connected.
Therefore, when the link 20 is in the process of swinging forward with the stationary pivot 32 as a fulcrum, and the movable pivot 33 exceeds the bottom dead center (FIG. 7 → FIG. 8), the installation link 50 is connected to the base pivot. The slide outer frame 65 is slid so as to be pushed out with respect to the slide inner frame 66 (in other words, the back support frame 27 is extended), with the support portion 51 as a base point, and the foot kneading device 5 is projected forward. After that, as shown in FIGS. 9 and 10, the back support frame 27 reaches the allowable extension amount and does not extend any more, and the rolling wheels 22 (in short, the entire foot grinder 5) float above the floor surface F.

At the use position U of the foot kneading device 5, the front surface of the foot kneading device 5 is in a horizontal state (including some steps) substantially flush with the upper surface of the seat portion 2, or is bent forward and downward. Yes.
The swing drive unit 21 applies a driving force for swinging back and forth with respect to the link 20. In this embodiment, the swing drive unit 21 is provided with an expansion / contraction mechanism 36 that performs an expansion / contraction operation using the electric motor 35 as a drive source. . As the expansion / contraction mechanism 36, for example, a mechanism using a screw shaft (such as a ball screw) or a combination mechanism of a rack and a pinion gear can be employed.
A bracket member 38 is provided on a pivot (rotating integrally with the link 20) that rotatably holds the rear end of the link 20 in the stationary pivot support 32 so as to rotate integrally therewith. The front end portion of the expansion / contraction mechanism 36 is connected to the bracket member 38 so as to be relatively rotatable. Further, the rear end portion of the telescopic mechanism 36 is rotatably connected to the vertical flange portion 6 a of the leg frame 6.

The rolling wheel 22 is provided at the lower end of the back surface of the foot massaging device 5, that is, at the corner portion between the bottom surface and the back surface (the connecting portion between the bottom surface support frame 26 and the back surface support frame 27 in the moving frame 28). The top is held movably.
The outer peripheral surface (tire portion) of the rolling wheel 22 is preferably formed of hard rubber or the like that has both vibration absorption and resistance to slippage with respect to the floor surface F.
Next, the operation of the advance / retreat mechanism 15 configured as described above will be described. First, as shown in FIG. 6, the foot kneading device 5 is in a storage position P below the seat 2. At this time, the bottom surface of the foot massage device 5 is directed forward, the front surface (the surface provided with the holding grooves 10 and 10 into which the user's lower limbs are fitted) is directed upward, and the bottom surface is the front end of the seat portion 2. It is almost flush with the part.

When the electric motor 35 of the swing drive unit 21 is operated, the expansion / contraction mechanism 36 starts to expand. Therefore, the pivot of the stationary support portion 32 starts to rotate at the front end portion (bracket member 38) of the expansion / contraction mechanism 36, with the vertical flange portion 6a of the leg frame 6 connected to the rear end portion of the expansion / contraction mechanism 36 as a support. become.
Accordingly, the link 20 has the movable pivot 33 swinging forward with the stationary pivot 32 as a fulcrum. As a result, as shown in FIG. To move forward. At this time, since the rolling wheels 22 roll on the floor F, the foot kneading device 5 moves smoothly.

As the link 20 swings further forward, the upper part of the back of the foot massaging device 5 starts to rise as shown in FIGS. And if the back upper part of the foot kneading device 5 protrudes forward from the lower part of the front end of the seat 2, and the foot kneading device 5 rises as a whole while protruding forward, as shown in FIG. The kneading device 5 has reached the use position U.
A series of these operations is the advance operation of the advance / retreat mechanism 15. The foot massage device 5 that has reached the use position U is in a horizontal state or a front-down direction in which the bottom surface faces the floor surface F, the bottom surface faces forward, and the front surface that massages the lower limbs is substantially flush with the upper surface of the seat 2. It is in a state of facing upwards while continuing in a bent state.

If the user operates the lower limb massage mechanism with one foot inserted into the left and right holding grooves 10, 10 with respect to the foot massage device 5, the user can comfortably receive massage. At this time, the foot massaging device 5 ascends as a whole and protrudes forward, so that the user can take a relaxed posture such as throwing the foot forward, and there is no need to bend the knee extremely. , To improve the feeling of use.
On the other hand, when the electric motor 35 of the swing drive unit 21 is reversely operated from the use position U, the expansion / contraction mechanism 36 starts to contract. Therefore, the pivot of the stationary support portion 32 rotates in the reverse direction with the front end portion (bracket member 38) of the expansion / contraction mechanism 36, with the vertical flange portion 6a of the leg frame 6 connected to the rear end portion of the expansion / contraction mechanism 36 as a support. To start.

  Along with this, the link 20 is configured such that the moving pivot 33 swings backward with the stationary pivot 32 as a fulcrum. As a result, as shown in FIGS. As a result, the part protruding forward is lowered while retreating backward, and the upper part of the front is further sunk downward. As shown in FIG. 7, when the upper back portion is lowered until the front upper portion of the foot kneading device 5 becomes lower than the lower portion of the seat portion 2, the foot kneading device 5 moves backward with the lower portion of the seat portion 2 facing backward. At this time, since the rolling wheels 22 roll on the floor F, the foot kneading device 5 moves smoothly.

Then, as shown in FIG. 6, the foot kneading device 5 is returned to the state stored in the storage position P. A series of these operations is the retreat operation of the advance / retreat mechanism 15.
When the foot massage device 5 is in the storage position P, the bottom surface thereof faces forward and does not protrude from the front end portion of the seat portion 2, so that the “user who does not receive a massage” sitting on the massage chair 1 is comfortable. The body posture can be maintained and the appearance of the massage chair 1 is simple and refreshing.
It should be noted that a sensor such as a limit switch is provided on the upper surface of the seat portion 2 or the holding groove 10 of the foot massage device 5 and the sensor detects the user, or the massage mechanism or the lower limb massage mechanism is It is preferable that the execution of the retreating operation is ignored when there is an operation for causing the advance / retreat mechanism 15 to perform the retreating operation during the operation. By adopting such a configuration, it is possible to reliably prevent an unfavorable situation such as hurting the user's lower limb.

By the way, the massage chair 1 which concerns on this invention is not limited to the said embodiment.
For example, it is assumed that the stationary pivot part 32 is provided as a pair (that is, two places) on both the left and right sides of the seat part 2, and the movable pivot part 33 is also provided as a pair (that is, two places) on both the left and right sides of the foot massage device 5. Can be. In this case, a pair of left and right (that is, two) links 20 may be used so as to connect the left stationary pivot 32 and the movable pivot 33 and the right stationary pivot 32 and the movable pivot 33, respectively. Good.

Further, the link 20 is not limited to the C-type in a side view, and can be formed as a straight line.
The swing drive unit 21 can be configured to operate a gear mechanism with an electric motor and thereby swing the link 20 back and forth.

  The present invention can be applied to a foot massage device attached to a massage chair, and can also be applied to a sofa, a vehicle seat, and the like.

It is the side view which showed one Embodiment of the massage chair which concerns on this invention in a partially internal see-through state. It is the side view shown in the state which moved the foot massage device to the use position from the state of FIG. FIG. 3 is a view as seen from an arrow A in FIG. 2 (a perspective view in a state viewed from below). It is a BB line arrow directional view of FIG. FIG. 3 is a perspective view corresponding to FIG. 2. It is the side view which showed the accommodation state of the foot massage device. It is the side view shown as a state which is operating the foot kneading device between a storage state and a use position, and close | similar to a storage state. FIG. 5 is a side view showing a state in which the foot kneading device is operated between the storage state and the use position and is just in the middle between the storage state and the use state. It is the side view shown as a state which is operating the foot kneading device between a stowed state and a use position, and is close to a use state. It is the side view which showed the use condition of the foot massage device. It is the perspective view which showed the back surface support frame of the foot massage device. It is the perspective view which showed one Embodiment of the massage chair which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Massage chair 2 Seat part 3 Back part 5 Footrest device 15 Forward / backward mechanism 20 Link 22 Rolling wheel 21 Oscillation drive part 32 Stationary pivot part 33 Moving pivot part 35 Electric motor 36 Telescopic mechanism 50 Construction link F Floor surface P Storage position U Use position

Claims (8)

In a massage chair having a seat, a backrest provided at the rear of the seat, and a foot massage device installed at the front of the seat,
An advance / retreat mechanism connected to the foot grinder is provided below the seat,
When the advance / retreat mechanism moves forward, the foot kneading device floats above the floor in front of the seat and moves to a use position where the user's lower limb can be massaged, and the advance / retreat mechanism retracts backward. Then, the massage chair provided with the foot massage device, wherein the foot massage device is stored in a storage position formed below the seat. The foot massage device in the use position is in a state where the back surface faces the floor surface and the bottom surface faces the front,
The foot massaging device in the storage position is in a state in which the bottom surface thereof faces frontward and the front surface of the seat portion is substantially flush with the front surface for massaging the lower limbs. A massage chair provided with the described foot massage device. The advance / retreat mechanism is:
An advance operation for bringing the foot grinder to the use position by further advancing while raising the back upper part of the foot grinder in the storage position forward from the front end of the seat, and
By lowering the back upper part of the foot grinder in the use position while moving backward, the front upper part of the foot grinder is lowered below the seat part and then retracted downward by the seat part. Retraction operation to return to the storage position,
The massage chair provided with the foot kneading device according to claim 1 or 2, wherein the massage chair is configured to perform. The advancing / retreating mechanism is connected between a stationary pivot provided at the lower part of the seat and a movable pivot provided at the upper back of the footgrip device so that the movable pivot can be swung back and forth around the stationary pivot. A link to be held, a swing drive unit that applies a driving force for swinging back and forth to the link, a rolling wheel that is provided at the lower back end of the foot kneading device and is held movably on the floor surface, It is spanned between the middle part of the link and the back part of the foot-climbing device, and is rotatable with respect to the link and the back part of the foot-gearing device and slidable along the back side of the foot-gearing device. An erection link, and
When the link swings to the rear side of the swinging area of the link, the foot kneading device moves to the storage position, and when the link swings to the front side of the swinging area of the link, the foot kneading device moves to the use position. The massage chair provided with the foot massage apparatus in any one of Claims 1-3 characterized by the above-mentioned. A back support frame comprising a lower slide frame and an upper slide frame that are slidable with respect to each other is provided on the back portion of the foot massage device,
The foot slide device is attached to the lower slide frame, and the erection link is rotatably connected.
5. A massage chair provided with a foot massage device according to claim 4, wherein a moving pivotal support portion is provided at an upper end portion of the upper slide frame, and a tip end portion of the link is swingably connected.   The said link is formed with the single member which connects the stationary pivot part provided in the left-right direction center part of a seat part, and the movement pivot part provided in the left-right direction center part of a foot massage apparatus. The massage chair provided with the foot massage apparatus of claim | item 4 or 5.   The said link is formed in the shape which curves in the side view C type | mold which follows a top part from the front upper part of a foot kneading device, when the said foot kneading device is located in a storage position. The massage chair provided with the foot massage apparatus in any one of -6.   The massage chair provided with the foot kneading device according to any one of claims 4 to 7, wherein the swing drive portion of the advance / retreat mechanism has an expansion / contraction mechanism driven by an electric motor.

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