JPH06343534A - Raising/setting type bed equipment - Google Patents

Abstract

PURPOSE:To provide the raising/setting type bed equipment by which the body is not bent more than required. CONSTITUTION:In the bed equipment 1 having a back rest part 5a which can be raised and set and an upper leg supporting part 5c, a limit switch LS3 for detecting a low position (15 degrees) between the upper limit position (80 degrees) and the lower limit position (0 degree) of the upper leg supporting part 5c is disposed in the upper leg supporting part 5c, so that in the case a switch for raising simultaneously the back rest part 5a and the upper leg supporting part 5c is turned on, the upper leg supporting part 5c is not raised up to the upper limit position, and the bed raising is stopped at the time point when the low position is detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tilting bed apparatus.

[0002]

2. Description of the Related Art In recent years, an upright bed device has been put on the market in which the backrest portion and leg support portions of a bed body can be raised to take a free posture. For example, Shokai 6
In the bed apparatus disclosed in JP-A-2-126162,
The backrest and leg support are supported simultaneously or separately so that they can be raised, and when the user presses the operation switch, the backrest or leg support rises up to the predetermined upper limit position, and the body is lifted. You can take the posture that caused

[0003]

However, in general, the optimum upper limit position of the leg support is different when both the leg support and the backrest are raised and when only the leg support is raised. In the former case, the optimum upper limit position of the leg support is lower than in the latter case. Therefore, if the upper limit of the leg support is set at a position where a comfortable posture can be obtained when both the leg support and the backrest are raised, the position of the leg support when the leg support is raised is low. , The effect of raising the leg support cannot be sufficiently obtained. On the contrary, if you set the upper limit of the leg support to a position where you can take a comfortable position when you raise only the leg support, when you raise both the leg support and the backrest,
The body becomes V-shaped between the raised leg support and the backrest, and I cannot take a comfortable posture. Particularly, in the case of a patient who is injured in a hospital or the like, the refraction between the backrest portion and the leg support portion becomes a great burden, which is not preferable.

SUMMARY OF THE INVENTION Therefore, the present invention aims to solve the above-mentioned problems and to provide a retractable bed apparatus in which the body is not bent more than necessary.

[0005]

[Constitution of the invention]

[0006]

In order to solve the above-mentioned problems, the present invention as set forth in claim 1 proposes a bed body having a backrest and a leg support which can be raised and lowered, and a backrest. First driving means for tilting, second driving means for tilting the leg support portion, and simultaneous control switch means for instructing simultaneous raising or lowering of the first raising means and the second raising means, Individual control switch means for individually instructing the rise or fall of either the first raising / lowering means or the second raising / lowering means, the first drive means and the second drive means, respectively, and the backrest. Parts and first and second upper and lower limit position setting means for detecting upper and lower limit positions of the leg support part and stopping the operation of the first driving means and the second driving means, the first driving means and the first 2 Drive means And a low position setting means for stopping the operation of the second drive means at a predetermined position between the upper and lower limit positions of the leg support portion when the simultaneous control means gives an instruction for simultaneous ascent. It is a tilting bed device.

The invention according to claim 2 further comprises a bed body having a backrest and a leg support which can be raised and lowered, a first drive means for raising and lowering the backrest, and a leg support. A second drive means, a control switch means for instructing the first raising and lowering means and the second raising and lowering means to move up and down, and the first driving means and the second driving means, respectively, and the backrest portion. And first and second upper and lower limit position setting means for detecting the upper and lower limit positions of the leg support portion and stopping the operation of the first driving means and the second driving means,
Position detection means for detecting that the backrest is not at the lower limit position and the first drive means and the second drive means are provided, and the position detection means detects that the backrest is not at the lower limit position. And a predetermined position setting means for stopping the operation of the second drive means at a predetermined position between the upper and lower limit positions of the leg support portion when an instruction to raise the leg support portion is inputted from the control switch means. The tilting bed device is characterized by being provided.

[0008]

According to the first aspect of the present invention, when the simultaneous control switch means gives an instruction to raise both the backrest portion and the leg support portion, the leg support portion is raised before reaching the upper limit position. The low position setting means deactivates the second driving means. Therefore, the leg support portion does not rise to the upper limit position but is located at a predetermined position between the upper limit position and the lower limit position, while the backrest portion rises to the upper limit position by the first upper and lower limit position setting means and stops. In this way, when both the backrest and the leg support rise, the leg support does not rise to the upper limit position, so that the body does not bend more than necessary and a comfortable posture can be taken.

According to the second aspect of the invention, the position detecting means for detecting whether or not the backrest portion is at the lower limit position is provided, and the position of the backrest portion is not at the lower limit position by this position detecting means. When is detected, the predetermined position setting means does not raise the leg support portion to the upper limit position but raises it to a predetermined position between the upper limit position and the lower limit position and stops. In this way, if the backrest rises even a little, the leg support portion stops at the predetermined position, so that the body is not bent more than necessary and the user is not burdened.

[0010]

【Example】

(1) A first embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, the tiltable bed apparatus 1 of this embodiment includes a machine frame 2 and a bed body 3.

The machine casing 2 is composed of a head board 2a, a main board 2b and a foot board 2c. The bed body 3 is composed of a mattress 4 and a frame 5 that supports the mattress 4. Frame 5 is
The backrest portion 5a, the waist support portion 5b, the upper leg support portion 5c, and the lower leg support portion 5d, which are hinged to each other so as to be bendable, are configured. The waist support portion 5b is directly fixed to the main board 2b. The backrest portion 5a, the upper leg support portion 5c, and the lower leg support portion 5d are a first drive portion 10 and a second drive portion 10, which will be described later.
The drive unit 20 supports the main board 2b so that the main board 2b can be erected. In particular, the backrest portion 5a is configured such that one end portion hinged to the waist support portion 5b is raised and the other end portion is lifted up, and the upper leg support portion 5c and the lower leg support portion 5d are connected to each other by a hinge. It is designed to lift like a letter.

Next, the first drive unit 10 for raising and lowering the backrest 5a of the frame 5 will be described. First drive unit 1
0 is disposed between the backrest portion 5a and the main frame 2b. As shown in FIG. 2, the first drive unit 10 is
A pair of arms 11 one end of which is pivotally attached to the backrest portion 5a.
And a screw shaft 12 having the other end of the arm 11 pivotally attached to the end thereof, a nut 13 into which the screw shaft 12 is screwed, and a motor M1 for rotating the nut 13 via a shaft 14. . The motor M1 can rotate in forward and reverse directions, and the shaft 1
4, rotate the nut 13, screw shaft 12
Move back and forth. By swinging the arms 11 in this manner, the backrest portion 5a is erected around the hinge portion between the backrest portion 5a and the waist support portion 5b.

Further, a limit switch LS1a (first upper limit position setting means) for detecting that the backrest 5a has risen to reach the upper limit position is provided in the vicinity of the screw shaft 12. Limit switch LS1
a is a normally closed type (hereinafter referred to as NC type).
When the backrest 5a reaches the upper limit position, the motor M1
Head 12a of the screw shaft 12 moved by
It is opened by being turned on, and the operation of the motor M1 is stopped. Further, a limit switch LS1b (first lower limit position setting means) for detecting that the backrest 5a is lying down and in a flat state is provided on the back surface of the backrest 5a. Limit switch LS
1b is also an NC type, and when the backrest 5a reaches the lower limit position in the flat state, the backrest 5a is turned on and opened between the mainframe 2b and the operation of the motor M1 is stopped. In the present embodiment, the upper limit setting angle of the backrest 5a is 80 degrees and the lower limit setting angle is 0 degrees.

Next, the second drive section 20 for raising and lowering the upper leg support section 5c of the frame 5 will be described. Second drive unit 2
0 is disposed between the upper leg support portion 5c and the main frame 2b. As shown in FIG. 2, the second drive unit 20 is
A pair of arms 21 one end of which is pivotally attached to the upper leg support portion 5c.
And a screw shaft 22 having the other end of the arm 21 pivotally attached to the end, a nut 23 into which the screw shaft 22 is screwed, and a motor M2 for rotating the nut 23 via a shaft 24. . The motor M2 can rotate in the forward and reverse directions, and the shaft 2 can be rotated depending on the rotation direction.
4, rotate the nut 23, screw shaft 22
Move back and forth. By swinging the arms 21 in this manner, the upper leg support portion 5c is erected around the hinge portion between the upper leg support portion 5c and the waist support portion 5b.
When the upper leg supporting portion 5c rises, the lower leg supporting portion 5d hinged to the upper leg supporting portion 5c is pulled up and rises, forming a square V shape. On the contrary, when the upper leg support portion 5c falls down, the lower leg support portion 5d also falls down and returns to the flat lower limit position.

Further, a limit switch LS2a (second upper limit position setting means) for detecting that the upper leg support portion 5c has risen to reach the upper limit position is provided in the vicinity of the screw shaft 22. Limit switch LS2
a is an NC type, and when the upper leg support 5c reaches the upper limit position,
The screw shaft 22 which is moved by the motor M2 is turned on to be opened, and the operation of the motor M2 is stopped. Further, on the back surface of the lower leg supporting portion 5d, an NC type limit switch LS2b (second portion) which detects that the upper leg supporting portion 5c is lying down and is in a flat state.
Lower limit position setting means) is provided. Upper leg support 5c
And when the lower leg support portion 5d reaches the lower limit position in the flat state,
The limit switch LS2b is turned on and opened between the lower leg support portion 5d and the main frame 2b to stop the operation of the motor M2. The upper limit set angle of the upper leg support portion 5c and the lower leg support portion 5d in this embodiment is 50 degrees, and the lower limit set angle thereof is 0 degree.

A spring 32 is attached to the main frame 2b.
An NC type limit switch LS3 is provided via the. The limit switch LS3 is turned on / off by an L-shaped bar 31 which is arranged on the back surface of the upper leg supporting portion 5c and moves up and down together with the upper leg supporting portion 5c.
The limit switch LS3 is turned on by the L-shaped bar 31 when the upper leg support portion 5c is raised to the position of about 15 degrees,
That is, it is opened and acts as a low position setting means which is also a feature of the present invention.

FIG. 3 shows a control circuit 40 of this embodiment.
The control circuit 40 includes a control switch unit 50 and a power supply unit 41.
And a first motor control unit 42 that controls the motor M1 and a second motor control unit 43 that controls the motor M2.

The control switch section 50 includes a back wake-up switch SW1 for instructing the wake-up of the backrest section 5a and a backrest section 5.
a back fall switch SW2 for instructing the fall of a, leg upright switch SW3 for instructing the upper leg support 5c to wake up, leg fall switch SW4 for instructing the fall of upper leg support 5c, backrest 5a and upper leg support It comprises a back leg wake-up switch SW5 for instructing simultaneous wake-up of both parts 5c, and a back leg fold-down switch SW6 for instructing simultaneous lay-down of both the backrest part 5a and the upper leg support part 5c.

The power supply unit 41 is a 100V AC current 41a.
And a transformer 41b for stepping down this alternating current.

The first motor control unit 42 has a normally open type (hereinafter referred to as NO type) relay RL1 and a relay RL2. The coil of the relay RL1 is connected to the alternating current via the contact of the switch SW1,
The movable contact of No. 1 is connected to the positive phase terminal of the first motor M1 via the NC type limit switch LS1a, and an alternating current of 100 V is applied to the common terminal of the first motor M1.
Supply to 1. The coil of the relay RL2 is the switch SW2.
Is connected to the alternating current via the contact of the first motor M1 and the movable contact of the relay RL2 is connected to the negative phase terminal of the first motor M1 via the NC type limit switch LS1b.
AC 100V is supplied to the first motor M1 with the common terminal of the first motor M1. The coil of the relay RL1 is connected to the alternating current via the switch SW5 arranged in parallel with the switch SW1, and the coil of the relay RL2 is connected to the alternating current via the switch SW6 arranged in parallel with the switch SW2. It has become.

The second motor control section 43 has an NO type relay RL3 and a relay RL4.

The coil of the relay RL3 is connected to the alternating current via the contact of the switch SW3, and the movable contact of the relay RL3 is connected to the second via the NC type limit switch LS2a.
It is connected to the positive phase terminal of the motor M2 and supplies 100 V AC to the second motor M2 between the common terminal of the second motor M2. The coil of the relay RL4 is connected to the alternating current via the contact of the switch SW4, and the movable contact of the relay RL4 is connected to the negative phase terminal of the second motor M2 via the NC type limit switch LS2b, and the second motor M2 is connected. AC 100 V is supplied to the second motor M2 with the common terminal of
The coil of the relay RL3 is connected via the switch SW5 arranged in parallel with the switch SW3, and the coil of the relay RL2 is arranged via the switch S5 arranged in parallel with the switch SW4.
It is also designed to be connected to an alternating current through W6. Further, between the relay RL3 and the switch SW5,
The limit switch LS3 is arranged in series.

Next, the operation of the first embodiment will be described.

(1-1) A case where only the backrest portion 5a is raised alone will be described. When the switch SW1 is turned on and the contacts are connected, the relay R of the first motor control unit 42
The coil of L1 is energized, the movable contact of the relay RL1 is closed, and the AC current of 100 V is applied to the positive phase terminal of the first motor M1.
Is supplied. Therefore, the first motor M1 rotates in the forward direction to rotate the shaft 14 and the nut 13. As a result, the screw shaft 12 extends, and the arms 11, 11 wake up, so that the backrest portion 5a wakes up. Then, when the backrest 5a wakes up to an angle position of 80 degrees, the limit switch LS1a is turned on to open the contact, the operation of the first motor M1 stops, and the wakeup of the backrest portion 5a stops at the angle position of 80 degrees. .

(1-2) A case where only the backrest 5a is laid down alone will be described. When the switch SW2 is turned on to connect the contacts, the relay R of the first motor control unit 42 is connected.
The coil of L2 is energized, the movable contact of the relay RL2 is closed, and an alternating current of 100 V is applied to the negative phase terminal of the first motor M1.
Is supplied. Therefore, the first motor M1 rotates in the reverse direction to rotate the shaft 14 and the nut 13 in the reverse direction. As a result, the screw shaft 12 is pulled, and the arm 1
The backrest 5a falls down due to the fall of 1 and 11. When the backrest portion 5a falls to the angular position of 0 degree, the limit switch LS1b is turned on to open the contact, the operation of the first motor M1 is stopped, and the backrest portion 5 is stopped.
The lodging of a is completed.

(1-3) A case where only the upper leg support portion 5c is woken up will be described. When the switch SW3 is turned on to connect the contacts, the relay R of the second motor control unit 43
The coil of L3 is energized, the movable contact of the relay RL3 is closed, and an alternating current of 100 V is applied to the positive phase terminal of the second motor M2.
Is supplied. Therefore, the second motor M2 rotates in the forward direction to rotate the shaft 24 and the nut 23. As a result, the screw shaft 22 extends and the arms 21, 21 wake up, so that the upper leg support portion 5c wakes up. When the upper leg support portion 5c wakes up to an angle position of 50 degrees, the limit switch LS2a is turned on to open the contact, the operation of the second motor M2 is stopped, and the upper leg support portion 5c wakes up at an angle of 50 degrees. Stop at position.

(1-4) A case where only the upper leg supporting portion 5c is laid down alone will be described. When the switch SW4 is turned on and the contacts are connected, the relay R of the second motor control unit 43
The coil of L4 is energized, the movable contact of the relay RL4 is closed, and the alternating current of 100 V is applied to the negative phase terminal of the second motor M2.
Is supplied. Therefore, the second motor M2 rotates in the reverse direction to rotate the shaft 24 and the nut 23 in the reverse direction. As a result, the screw shaft 22 is pulled, and the arm 2
The upper leg support portion 5c is laid down by the laying down of 1 and 21. Then, when the upper leg support portion 5c falls to the angular position of 0 degree, the limit switch LS2b is turned on to open the contact, the operation of the second motor M2 is stopped, and the upper leg support portion 5 is stopped.
The lodging of c is completed.

(1-5) Backrest 5a and upper leg support 5
The case where both c are awakened simultaneously will be described. When the switch SW5 is turned on to connect the contacts, the coils of the relay RL1 of the first motor control unit 42 and the relay RL3 of the second motor control unit 43 are energized, and the movable contacts of the relays RL1 and RL3 are closed. An alternating current of 100 V is supplied to the positive phase terminals of the first motor M1 and the second motor M2, and the backrest portion 5a and the upper leg support portion 5c wake up. Backrest 5
When a gets up to an angular position of 80 degrees, the limit switch LS1a operates and the power supply to the first motor M1 is stopped. On the other hand, when the upper leg support portion 5c wakes up to an angle position of 15 degrees, the limit switch LS3 is turned on to open the contact, the energization of the coil of the relay RL3 is stopped and the movable contact of the relay RL3 is opened. In this way, the power supply to the second motor M2 is stopped, and the upper leg support portion 5c stops waking up at an angle position of 15 degrees. As described above, when both the backrest portion 5a and the upper leg support portion 5c are raised at the same time, the limit switch LS3 acts so that the angle between the backrest portion 5a and the upper leg support portion 5c becomes 85 degrees or less. Don't 35 more than when each wakes up alone
It's spread out so that you don't put an undue strain on your body.

(1-6) Backrest 5a and upper leg support 5
The case where both c are laid down at the same time will be described. When the switch SW6 is turned on to connect the contacts, the coils of the relay RL2 of the first motor control unit 42 and the relay RL4 of the second motor control unit 43 are energized, and the movable contacts of the relays RL2 and RL4 are closed. An alternating current of 100 V is supplied to the negative phase terminals of the first motor M1 and the second motor M2, and the backrest portion 5a and the upper leg support portion 5c fall down. Then, when each of them falls to the angular position of 0 degree, the limit switch LS1b and the limit switch LS2b act and the first switch
The energization of the motor M1 and the second motor M2 is stopped, and the fall is completed.

Regarding the above operation, the switch S
If W1 to W6 are turned off midway, the backrest part 5a and the upper leg support part 5c stop rising and falling down midway, respectively, and can be positioned between the upper limit position and the lower limit position.

(2) Next, a second embodiment of the present invention will be described with reference to FIG. In the second embodiment, if the backrest portion 5a is awake even a little, the upper leg support portion 5c is awake only up to 15 degrees. Since the basic structure of the second embodiment is substantially the same as that of the first embodiment,
The same configurations are given the same reference numerals, and description thereof is omitted.

In the second embodiment, between the switch SW3 and the transformer 41b, an NC type limit switch is turned on, that is, opened by the L-shaped bar 31 when the upper leg support 5c is raised to a position of about 15 degrees. NC type limit switch LS1b 'for detecting that LS3' (predetermined position setting means) and the backrest 5a are lying down and in a flat state.
However, it is different from the first embodiment in that they are arranged in parallel, and other points are the same as in the first embodiment.

Next, the operation of the second embodiment will be described. In the second embodiment, only the case where the switch SW3 is turned on to wake up the upper leg support portion 5c alone will be described. Since the other points are substantially the same as those in the first embodiment, description thereof will be omitted.

(2-1) First, the case where the upper leg support portion 5c is raised when the backrest portion 5a is at a flat angular position of 0 degrees will be described. In this case, both the limit switch LS3 'and the limit switch LS1b' are closed. Here, when the switch SW3 is turned on to connect the contacts, the coil of the relay RL2 of the second motor control unit 43 is energized, and the movable contact of the relay RL3 is closed.
An alternating current of 100 V is supplied to the positive phase terminal of the motor M2. Therefore, the second motor M2 rotates normally and the upper leg support portion 5c
Get up. When the upper leg support 5c wakes up to an angle position of 15 degrees, the limit switch LS3 'opens, but the circuit remains closed because the limit switch LS1b' is closed, and the upper leg support 5c moves to the angular position of 50 degrees. The limit switch LS2a is turned on and the contacts are opened when the user gets up to, and the operation of the second motor M2 is stopped, and the upper leg support 5
The wake up of c stops at an angle position of 50 degrees.

(2-2) A case where the backrest portion 5a is awake even a little will be described. In this case, the limit switch LS1b 'has the contact open. Here, when the switch SW3 is turned on to connect the contacts, the coil of the relay RL2 of the second motor control unit 43 is energized, the movable contact of the relay RL3 is closed, and the alternating current is applied to the positive phase terminal of the second motor M2. 100V is supplied. Therefore, the second motor M
2 rotates forward and the upper leg support portion 5c wakes up. Upper leg support 5
When c gets up to the angle position of 15 degrees, the limit switch LS3 'is opened and the limit switch LS1b' is also opened, so that the contact point between the switch SW3 and the transformer 41b is cut off, and the power supply to the relay RL3 is stopped. As a result, the movable contact of the relay RL3 is opened, the power supply to the second motor M2 is stopped, and the upper leg support portion 5c is stopped at the angle position of 15 degrees.

As described above, in the second embodiment, if the backrest 5a is awake even a little, the upper leg support 5c does not wake up, so that the burden of bending the body forcibly is eliminated, and the bed is gentler to the body. It can be a device.

In both the first and second embodiments, the upper limit position of the backrest portion 5a is 80 degrees, the upper limit position of the upper leg support portion 5c is 50 degrees, and the lower setting position of the upper leg support portion 5c (predetermined setting). Position) was set to 15 degrees, but these numbers are only examples,
The present invention is not limited to this.

Further, in both the first and second embodiments, since the limit switches LS3 and LS3 'are arranged on the main frame 2b via the spring 32, the upper leg support portion 5c is positioned at an angle position of 50 degrees. Even if it goes up, the pressing force by the upper leg support portion 5c is absorbed by the spring 32, so that an unreasonable load is not applied to the limit switches LS3, LS3 '.

[0039]

According to the first aspect of the present invention, when the backrest portion and the leg support portion are simultaneously raised, the leg support portion does not rise to the upper limit position and the distance between the backrest portion and the leg support portion is increased. Since the angle formed by is large, the body does not bend more than necessary, and it does not place an unreasonable burden.

Further, according to the second aspect of the present invention, if the backrest portion is awake even a little, the leg support portion still does not rise to the upper limit position, and the angle between the backrest portion and the leg support portion is made. growing. Therefore, the excessive bending of the body is eliminated.

[Brief description of drawings]

FIG. 1 is a side view of a tilting bed device according to a first embodiment of the present invention.

FIG. 2 shows a drive mechanism of the first embodiment.

FIG. 3 shows a control circuit diagram of the first embodiment.

FIG. 4 shows a control circuit diagram of a second embodiment.

[Explanation of symbols]

3 bed body 5 frame 5a backrest portion 5c upper leg support portion 5d lower leg support portion 42 first motor control portion (first drive means) M1 first motor 43 second motor control portion (second drive means) M2 second motor SW1 Back up switch (independent control switch means) SW2 Back fall switch (independent control switch means) SW3 Leg up switch (independent control switch means) SW4 Leg fall switch (independent control switch means) SW5 Back leg up switch (simultaneous control switch means) SW6 Dorsal leg fall switch (simultaneous control switch means) LS1a Limit switch (first upper limit position setting means) LS1b Limit switch (first lower limit position setting means,
LS2a limit switch (second upper limit position setting means) LS2b limit switch (second lower limit position setting means) LS3 limit switch (low position setting means) LS1b 'limit switch (predetermined position setting means)

Claims (2)

[Claims] 1. A bed body having a backrest and a leg support that can be tilted, a first drive unit that tilts the backrest, a second drive unit that tilts the leg support, and Simultaneous control switch means for instructing simultaneous raising or lowering of the first raising / lowering means and the second raising / lowering means, and raising / lowering of either the first raising / lowering means or the second raising / lowering means independently. The independent control switch means for instructing, and the first drive means and the second drive means, respectively, are provided respectively, and detect the upper and lower limit positions of the backrest portion and the leg support portion to detect the first drive means and the second drive. First and second upper and lower limit position setting means for stopping the operation of the means, and the leg support part provided in the first drive means and the second drive means, when the simultaneous control means gives an instruction of simultaneous ascent. Between the upper and lower limit positions Causing folding type bed apparatus is characterized in that a low-position setting means for stopping the operation of the second drive means at a predetermined position. 2. A bed body having a backrest and a leg support that can be tilted, a first drive unit that tilts the backrest, a second drive unit that tilts the leg support, and 1 control means for raising and lowering the raising and lowering means and the second raising and lowering means, and upper and lower limits of the backrest portion and the leg support portion which are respectively provided in the first driving means and the second driving means First and second upper and lower limit position setting means for detecting a position and stopping the operation of the first driving means and the second driving means, and position detecting means for detecting that the backrest is not at the lower limit position Provided in the first drive means and the second drive means, the position detection means detects that the backrest portion is not at the lower limit position, and the control switch means gives an instruction to raise the leg support portion. Entering If, caused folding type bed apparatus characterized by comprising a predetermined position setting means for stopping the operation of the second drive means at a predetermined position between the lower limit position on the leg support.