JP2000177996A - Power jack with drive safety function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reliably prevent a forced load from being applied to a power source, a power transmission mechanism or the like with a compact structure having good installation stability by forcibly stopping the drive of the power source with a power source drive control means based on the output of a position detecting means when the vertical position of a jack reaches a limit position. SOLUTION: When a screw shaft 5 is rotated by an electric motor M via a gear box G, the position of a load table 7, i.e., the vertical position of a jack, is changed by the screwing relation between the screw shaft 5 and a nut block 8. A normally closed microswitch MS is fitted to the inside of an upper arm 2 as a means for detecting the vertical limit position of the jack, and an upper limit contact piece C1 is fitted to the inside of an upper arm 1 facing the upper arm 2. The contact piece C1 is brought into contact with the microswitch MS at the highest position of the jack to open the microswitch MS, and the drive of the electric motor M is forcibly stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power jack having a drive safety function, and more particularly to a jack having a mechanism for preventing runaway of the power jack.

[0002]

2. Description of the Related Art In general, a jack provided in an automobile is a pantograph-type jack or a y-type jack, which is operated by manually turning a handle to drive a screw shaft to perform an ascending / descending operation. A motor driven by a motor with a motor attached has also been proposed. Among these trends, the applicant has previously described, `` In a pantograph-type jack, the power source is arranged adjacent to a guide block disposed at the joint portion of the upper arm and the lower arm, so that the power source is located within the pantograph area. While fixed to the jack body, so that the rotation output shaft of the power source is coupled to the screw shaft via a power transmission mechanism,
Powered jack characterized in that only the load accompanying the power is applied to the power source. And filed a patent application as Japanese Patent Application No. 10-299193. The present invention provides a power jack having a simple structure, good stability during use, and a compact form when stored. Although it was possible to realize a jack that does not apply a load, it is driven by a power source instead of manually, so it is easy for people with physical disabilities such as the elderly and disabled Although it becomes possible to perform operations such as replacement, there is a new problem that the power source may run out of control unexpectedly. In particular, it is difficult for a person with a handicapped person, such as an elderly person or a physically handicapped person, to respond swiftly to the operation of the controller.Also, even a healthy person is mistaken or inadvertently mistakenly performs the operation. It is possible. In such a case, the driving force will continue to be applied even if the jack goes up and down the stroke range, and excessive force will be applied to the driving force transmission mechanism, which will not only accelerate the wear of gears etc. but also cause damage. Is also assumed. In addition, an excessive load is applied to the power source, and when an electric motor is used, it causes an overcurrent. In order to prevent runaway contrary to the intention of the electric motor, Japanese Utility Model Laid-Open Publication No. 6-6385 discloses a method in which a lever is attached to a lower arm, and a limit switch that contacts the lever at upper and lower positions of a jack is provided. The operation of stopping the driving of the electric motor by the above operation is shown. In the basic problem, the present invention is to make the gauge the same as the present invention.However, this invention involves mounting a lever or mounting the motor on the extension of the screw shaft outside the pantograph with a positioning plate interposed, so it is bulky at the time of storage. In addition, the installation stability during use was poor.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to solve these new problems. That is, the present invention has a compact structure with good installation stability. An object of the present invention is to provide a safe and easy-to-use powered jack that does not apply an unreasonable load to a power transmission mechanism or a power source.

[0004]

An electric motor, which is a power source, is fixed to a jack body so as to be adjacent to a guide block disposed at a joint portion between an upper arm and a lower arm and to be substantially contained in a pantograph area. Equipped with means to detect the jack's elevation position, when the limit position is reached, the power source is forcibly stopped. It is characterized by being prevented.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the present invention, an electric motor, which is a power source, is fixed to a jack body adjacent to a guide block disposed at a joint between an upper arm and a lower arm so as to be substantially contained within a pantograph area. By this, while stabilizing the installation during use and compactness during storage, equipped with means to detect the lifting position of the jack,
This jack is characterized by forcibly stopping the power source when it reaches the limit position, and also cuts the male screw of the screw shaft by the length corresponding to the lifting range of the jack, and when it reaches the limit position The jack is characterized in that the screw engagement with the nut block is released so that the jack spins and the lifting operation of the jack stops.

The present invention relates to a means for detecting an ascending / descending position of a jack, such as installing an encoder in a rotary drive portion to constantly grasp an ascending / descending position, or arranging a limit switch to operate at a limit position. A jack comprising: a power source drive control unit; and when the limit position is reached, the power source drive by the power source drive control unit is forcibly stopped by an output of the position detection unit,
The power source is forcibly stopped when the machine itself reaches the limit position by grasping the elevating state of the jack. The means for detecting the position of the jack is not limited to the above example, and the relationship between the position of the jack and the amount of displacement of the member using an appropriate detector that can detect the displacement of the member that is linked to the elevation of the jack. Various means for determining the limit position of the jack can be employed.

Further, the present invention provides a simple safety mechanism which does not require the provision of a means for detecting the position of the jack, which is expensive in view of the cost. The jack is moved up and down by the joints on both sides of the upper arm and the lower arm approaching and separating from each other due to the rotation of the screw shaft. That is, in this operation, the female screw drilled in the nut block disposed in one joint portion and the male screw of the screw shaft are in a screwing relationship, and the rotation amount of the screw shaft changes the distance between the joints. The length of the male screw of this screw shaft is cut by an amount corresponding to the range of the vertical stroke of the jack. By doing so, when the jack reaches both limit positions, the screwing relationship between the male screw of the screw shaft and the female screw of the nut block is released, and the screw shaft idles. Therefore, the distance between the two joints will not change any more.

[0008]

Embodiment 1 FIG. 1 shows an embodiment of the present invention. In this jack, upper arms 1 and 2 and lower arms 3 and 4 form a joint on both sides in such a manner that a nut block 8 and a guide block 9 are sandwiched. , And constitutes a pantograph by being pivotally connected to the load table 7. An externally threaded screw shaft 5 is passed between the guide block 9 and the nut block 8, and the external thread is screwed with an internal thread drilled in the nut block 8, and the screw shaft 5 is rotated. Then, the distance between the left and right joints changes due to the screwing relationship with the nut block 8, and the base stand 6
And the distance between the load table 7 is changed in reverse. By this operation, the position of the load table 7, that is, the lifting position of the jack is changed. In this embodiment, the torque of the screw shaft 5 is provided by an electric motor M, which is fixed to the guide block 9 via a gear box G containing a reduction mechanism.

The feature of this embodiment is that a microswitch MS is mounted inside the upper arm 2 as a means for detecting the jack's up / down limit position. A contact piece C1 is provided at an inner position of the upper arm 1 facing the switch MS, and the contact piece C1 comes into contact with the operating pin of the switch MS at the highest position of the jack. When the operating pin is pressed by the contact, a normally closed switch MS is opened to stop driving the electric motor M as a power source. A contact piece C2 is provided at an inner position of the lower arm 4 facing the switch MS.
The contact piece C2 is located at the lowest position of the jack.
Comes into contact with the operating pin of the switch MS, and when the operating pin is pressed by the abutment, the normally closed switch MS is opened to stop driving the electric motor M as a power source. ing. Ie micro switch
The MS and the contact pieces C1 and C2 constitute a limit switch,
At the upper and lower limit positions, a normally closed switch is opened to function as a safety device for forcibly stopping the driving of the power source. In this example, the microswitch MS is mounted inside the upper arm 2. However, it is natural that the same function can be achieved even if it is installed in another upper arm or a lower arm.

[0010]

Second Embodiment Next, as means for detecting the vertical position of the jack, the amount of rotation of the motor, which is the power source, is monitored by an encoder (rotary position detector), and a signal is issued when the vertical position is reached. In this example, a normally closed switch is opened to forcibly stop driving the power source. The lifting position of the jack is determined in accordance with the pitch of the screw cut into the screw shaft and the rotation amount of the screw shaft, and since the screw pitch is constant, if the rotation amount of the screw shaft is known, the lifting position is determined. Can be indexed. Since the screw shaft is driven by a motor via a reduction gear, the amount of rotation corresponds to the amount of rotation of the motor. Therefore, if the forward / reverse integrated rotation amount of the motor is detected by using an appropriate encoder, the jack elevating position can be determined from the detected value.

The motor shown in FIG. 2 detects the amount of rotation of the motor as a pulse signal, and detects it as an up-down counter C.
Therefore, the vertical position of the jack is calculated by integrating. The rotating disk R is interlocked with the rotation of the motor and has a magnet around its circumference.
The rotation amount of the rotating disk R is detected by a pulse signal p by a proximity switch PS having a rotation direction discriminating function disposed near the outer periphery of the rotating disk R and embedded with Mg. This pulse signal is sent to the up / down counter C together with the direction discrimination signal d, and the addition / subtraction is switched by the direction discrimination signal, and a count value corresponding to the ascending / descending position of the jack is obtained. The rotating disk R may be directly mounted on the motor shaft, may be mounted coaxially with one gear in the reduction gear train, or may serve as one gear. However, since the number of rotations becomes lower every time the gear train as a reduction mechanism passes, it is advantageous to install the motor at the highest rotation speed in order to detect a position with good sensitivity. A relay circuit is provided which emits a signal when the count value corresponding to the jack elevating limit position set by the limit value setting means L is reached, opens a normally closed switch, and forcibly stops driving the power source. . With this operation, the electric motor M stops.

Further, as a modification of this method, the entire stroke between the upper and lower limit positions of the jack is 36 degrees on the rotating disk.
It is also possible to decelerate until the rotation angle falls within 0 degree, and to determine the position of the jack by the angle detection. In such a case, a contact piece or the like may be provided at each of the upper and lower limit positions on the rotating disk, and when the angle is reached, the limit switch may be responsive and the same operation as in the first embodiment may be performed.

[0013]

[Embodiment 3] Next, an embodiment of a powered jack having a simple driving safety function without a means for detecting a jack up / down limit position and a power source drive control means will be described. FIGS. 3A and 3B are views showing the configuration of this embodiment, in which A is a front view showing the entire configuration, and B is an enlarged view of a main part. FIG. 4 is a diagram for explaining the operation of this embodiment. As can be seen from FIG. 3A, the screw shaft 5 has a screw portion 5b having a male thread cut in a central portion by a length corresponding to the lifting and lowering stroke of the jack, and a screw having a thickness smaller than the diameter of the thread root portion on both sides thereof. The round bar portions 5a and 5c which are not cut are formed. One end is attached to a guide block 9 containing an electric motor so as to be rotatable and non-slidable in the axial direction, the other end penetrates a female screw hole formed in the nut block 8, and the tip is a washer-like spring. The receiving piece SS is fixed by bolts B. The round bar portion 5c on this side of the screw shaft 5 penetrates and holds the helical spring S between the nut block 8 and the spring receiving piece SS. FIG. 3B is an enlarged view of the boundary between the round bar portion 5a and the male screw portion 5b of the screw shaft 5 on the guide block side and the female screw hole portion of the nut block 8. As is clear from this figure, a clearance is formed between the female screw hole and the outer portion of the round bar portion 5a, and the screwing relationship between the screw shaft 5 and the nut block 8 is released at this portion.

The operation of this embodiment will be described with reference to FIG. First, the operation at the time of raising the jack is as follows. When the screw shaft is rotated in the direction of the arrow in the state shown in FIG.
The nut block 8 is drawn toward the guide block 9 to reduce the distance between them, and conversely, the distance between the load table 7 and the base stand 6 becomes wider, and the load table 7 is raised. When the screw shaft 5b reaches the ascending limit position through the state shown in (b), the screw portion 5b of the screw shaft is disengaged from the female screw hole of the nut block 8, and the round bar portion passes through the hole, as shown in (c). In this state, even if the screw shaft continues to rotate, the screwing relationship is already released, so that the nut block 8 is idled and the nut block 8 is not drawn further toward the guide block 9 side. Further, when the screw shaft is rotated in the direction of the arrow in the state shown in FIG. 4B (d) at the time of lowering, the nut block 8 and the guide block 9 are pulled apart due to the screwing relationship with the nut block 8, and the distance between the two is increased. Is spread, and conversely, the distance between the load table 7 and the base stand 6 is reduced, and the load table 7 is lowered. When the spring S is compressed and reaches the lower limit position as shown in (e), the screw portion 5b of the screw shaft is disengaged from the female screw hole of the nut block 8 and the round bar portion 5c passes through the hole (f). ). In this state, even if the screw shaft continues to rotate, the screwing relationship is released, so that the nut block 8 is idle and the nut block 8 is not further separated from the guide block 9. Although the pantograph may be crushed by the load when the screwing relationship is released,
As shown in (f), at the limit position where the screw is released, the jack is located below the hook point of the car, and there is no excessive load on the jack. May be. Next, in the case where the operation is switched from this state to the ascending operation, the end of the screw portion 5b of the screw shaft is always
Since it is drawn to the nut block 8, the screwing relationship is smoothly restored as shown in (g), and the ascending operation can be started. On the other hand, at the upper limit position, the weight of the pantograph is applied,
In particular, even if no spring is provided, the screw shaft 5 is reversely rotated to smoothly recover the screw engagement. As described above, in this embodiment, when the jack reaches the lifting limit position, the screwing relationship is released, and the idle rotation operation is performed, so that no excessive force is applied to the drive unit. , Safety can be ensured.

[0015]

Embodiment 4 The above embodiment employs a configuration in which the end of the screw portion 5b of the screw shaft is always drawn to the nut block 8 by its resilient force by using a helix spring S. Fig. 5 shows an example using LS.
Shown in FIG. 5 is a view showing a main part in a broken manner, A is an overall perspective view, B is a view showing a state of a leaf spring during a jack elevating operation, and C is a view showing a state of a leaf spring at a lower limit position. is there. In this example, as is apparent from the figure, a leaf spring LS having a mounting hole in the base is mounted on the inner rear surface of the upper arm 1 with a rivet RV. The tip of the leaf spring LS is curved downward, and as shown in FIG. 5C, when the jack reaches the lower limit position, the curved portion comes into contact with the side end of the lower arm 3 and presses it. At this time, the screwing between the screw shaft 5 and the nut block 8 is released, and the boundary between the male screw portion 5b and the round bar portion 5c of the screw shaft contacts the inner end of the nut block 8. It is maintained by the action of the leaf spring LS. Even if the screw shaft 5 is further rotated, it will run idle at that position, and when the driving is reversed, the screwing is smoothly recovered and the ascending operation starts. 5B, when the screw shaft 5 and the nut block 8 are in a screwed state, the curved portion of the leaf spring LS is
Apart from the side edges, the spring force of the spring does not act on the lower arm.

[0016]

According to the present invention, since the driving force of the jack is obtained from the power source, not only a person who is not confident in the physical strength can use the jack easily, but also can set the jack up and down position. A power source drive control means for detecting the power source drive control means forcibly stopping the power source drive by the output of the position detection means when a limit position is reached. As a result, runaway of the power source can be prevented, and no unreasonable load is applied to the power transmission mechanism or the power source, so that its consumption and destruction can be reliably prevented, and no overcurrent flows to the motor. Even when the operator is inadvertent, even a handicapped person, such as an elderly person or a handicapped person, who has difficulty in agile operation, the safety function works reliably, and operations such as wheel replacement can be performed safely.

In another embodiment, the screw shaft is provided with a male screw thread at the center portion corresponding to the length of the ascending and descending strokes of the jack, and a thread having a diameter smaller than the diameter of the screw root portion on both sides thereof. By forming an unthreaded round bar portion, when the jack reaches the lifting limit position, the screwing relationship between the screw shaft and the nut block is released, and the idle rotation operation is performed at the limiting position. With this configuration, even if the power source is driven, no excessive force is applied to the power transmission unit and the power source, and safety can be ensured. Moreover, in this embodiment, there is no need to prepare special members such as a means for detecting the elevation position of the jack and a power source drive control means, which is simple and advantageous in cost.

[Brief description of the drawings]

FIG. 1 is a perspective view showing the overall configuration of an embodiment of the present invention.

FIG. 2 is a block diagram showing a main part configuration of another embodiment of the present invention.

FIG. 3 is a view showing an embodiment of a different embodiment of the present invention, wherein A is a front view showing an entire configuration, and B is a partially enlarged view of a main part.

FIG. 4 is a diagram illustrating the operation of a third embodiment of the present invention.

FIG. 5 is a view showing a further embodiment of the present invention, wherein A is a perspective view showing the overall configuration, B is a view showing the state of the leaf spring during the jack elevating operation, and C is a state of the leaf spring at the lower limit position. FIG.

[Explanation of symbols]

1, 2 Upper arm M Electric motor 3, 4 Lower arm MS Micro switch 5 Screw shaft C1 Upper contact piece 5a, 5c Round bar C2 Lower contact piece 5c Male thread R Rotating disk 6 Base stand PS proximity switch 7 Load table L Limit value setting means 8 Nut block C Up / down counter 9 Guide block S Spring B Bolt SS Spring receiving piece LS Leaf spring RV Rivet

Claims (4)

[Claims] 1. A jack in which an electric motor serving as a power source is fixed to a jack body so as to be adjacent to a guide block disposed at a joint portion of an upper arm and a lower arm and substantially fit within a pantograph area. A position detection unit and a power source drive control unit, and when the vehicle reaches a limit position, the power source drive control unit receiving the output of the position detection unit forcibly stops the power source drive. Jack. 2. The position detecting means is a limit switch constituted by a contact piece provided on an upper arm and a lower arm opposed to a micro switch provided on the upper arm or the lower arm, and the power source drive control means is provided with a power switch. The jack according to claim 1, which is a power switch of a motor. 3. The power source drive control means is a power switch of the electric motor, wherein the position detection means is an encoder for determining an ascending / descending position from the rotation amount of a power transmission mechanism between the power source and the screw shaft. Jack. 4. A jack in which a rotary output shaft of a power source is connected to a screw shaft via a power transmission mechanism, wherein a male screw of the screw shaft is cut by a length corresponding to a lifting range of the jack, and a limit position is set. The jack is characterized in that when it reaches, the screw with the female screw drilled in the nut block is disengaged, causing the jack to idle and stop the vertical movement of the jack.