JPH04366050A - Screw advanced mechanism - Google Patents

Abstract

PURPOSE:To enlarge the stroke of a screw advanced mechanism. CONSTITUTION:A screw advanced mechanism 4 is composed of a screw shaft 41, screw pipe 42 and nut member 43. The screw shaft 41 is formed on the outer peripheral surface with a screw 41a and rotatably supported on the lower end by a frame 1 by a bearing 44. The screw pipe 42 is formed on the inner peripheral surface with a screw 42a screwed on the screw 41a of the screw shaft 41 and formed on the outer peripheral surface with a screw 42b. A cap 45 is fitted on the upper end to be rotatably supported by a bearing 46 provided on a cross plate 35. The nut member 43 is formed with a screw 43a screwed in the screw 42b formed on the outer peripheral surface of the screw pipe 42.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a screw mechanism in which the rotation of one member screwed together is regulated while the other member is rotated to cause these members to move linearly relative to each other. Regarding.

0002

[Prior Art] A nut member is screwed onto a screw shaft, the nut member is connected to another member, and by rotating the screw shaft, the other member connected to the nut member is moved up and down or back and forth. A screw mechanism has been known for a long time.

0003

[Problem to be solved by the invention] In the conventional screw mechanism, the maximum stroke of the screwing member is the range in which the nut member can move, in other words, the range from the base end to the tip of the threaded part carved on the screw shaft. There was a limit as a spiral mechanism.

0004

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a screw shaft having a threaded portion formed on the outer circumferential surface and a screw shaft having threaded portions formed on the inner circumferential surface and the outer circumferential surface. a screw pipe having a threaded portion formed on the outer circumferential surface of the screw shaft, and a nut member threaded onto the threaded portion formed on the outer circumferential surface of the screw shaft; The lead angle of the inner threaded part consisting of the threaded part formed on the outer peripheral surface of the screw pipe and the threaded part formed on the inner peripheral surface of the screw pipe,
The lead angles of the outer threaded portion formed by the threaded portion formed on the outer circumferential surface of the screw pipe and the threaded portion formed on the nut member were made different.

[0005]

[Operation] Since the lead angle of the inner threaded part and the lead angle of the outer threaded part are different, for example, the screw pipe rotates together with the screw shaft, the nut member is threaded first, and then the nut member is threaded. After the screw stops, the rotation of the screw pipe stops and the screw pipe starts spiraling.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the accompanying drawings. Here, FIG. 1 is a side view of a forklift to which the screw mechanism according to the present invention is applied, FIG. 2 is a sectional view of the mast of the forklift seen from the front, and FIG. 3 is an enlarged view of the screw mechanism according to the present invention. The sectional view and FIG. 4 are enlarged perspective views of essential parts of the screw mechanism according to the present invention.

[0007] A forklift has a frame 1 and an engine 2.
In addition, two masts 3 are installed on the front end of the frame 1, on the left and right (in the direction perpendicular to the paper in Figure 1).
A screw mechanism 4 according to the present invention is disposed inside the screw mechanism 4.
A holder 5 is moved up and down along the mast 3, and a fork 6 is foldably attached to the holder 5.

Further, a leg portion 7 extends forward from the lower end of the frame 1. The foot 7 has a front wheel 8 at its tip, a base end rotatably supported by a shaft 9, and an auxiliary wheel 10 at the base end that contacts the floor when the foot 7 is folded upward. is installed.

Further, a drive wheel 11 rotated by an engine 2 is provided at the rear of the frame 1.
1 is steered by a handle 12, and furthermore, as shown in FIG.
As shown in the figure, a hydraulic motor 13 rotated by an engine 2 is attached to the center of the frame 1.
3 is distributed to left and right drive shafts 15, 15 via a helical gear 14, and the rotation of this drive shaft 15 is transmitted to the screw mechanism 4 via a helical gear 16.

By the way, as shown in FIGS. 3 and 4, the mast 3 consists of an outer support 31 and an inner support 32.
A part of the inner column 32 is held in the outer column 31 via a bearing 33 so as to be able to rise and fall freely, and the other part serves as a guide rail 34. A cross plate 35 is provided between the upper ends of the left and right inner columns 32. has been erected.

On the other hand, the screw mechanism 4 has a screw shaft 4.
1. Consists of a screw pipe 42 and a nut member 43. The screw shaft 41 has a threaded portion 41 on the outer peripheral surface.
a is formed, and its lower end is rotatably supported by the frame 1 by a bearing 44.

[0012] The screw pipe 42 has a threaded portion 42a on its inner peripheral surface that is threadedly engaged with the threaded portion 41a of the screw shaft.
, and a threaded portion 42b is formed on the outer peripheral surface. Then, a cap 45 is fitted to the upper end, and this cap 4
5 is rotatably supported by a bearing 46 provided on the cross plate 35.

The nut member 43 is attached to the screw pipe 4.
Threaded portion 4 that is screwed into threaded portion 42b formed on the outer peripheral surface of No.2.
3a, and this nut member 43 has a connecting shaft 4.
The holding body 5 is attached via a shaft 7, and a roller 48 that comes into contact with the guide rail 34 is rotatably provided around the connecting shaft 47.

Here, FIG. 5(a) shows an inner threaded portion consisting of a threaded portion 41a formed on the outer peripheral surface of the screw shaft 41 and a threaded portion 42a formed on the inner peripheral surface of the screw pipe 42. FIG. 5(b) is a developed view of the threaded portion showing the relationship between the lead angle θ1 and the pitch t1. It is a developed view of the threaded part showing the relationship between the lead angle θ2 of the outer threaded part and the pitch t1, and when the pitch t1 of the threads of the inner threaded part and the outer threaded part are made equal, Since the thread diameter of the outer threaded part is smaller than the thread diameter of the outer threaded part, the lead angle is θ1>
It becomes θ2.

If θ1 is larger than θ2, slippage is more likely to occur between the screw pipe 42 and the nut member 43 than slippage (rotation) between the screw shaft 41 and the screw pipe 42. The screw shaft 41 and the screw pipe 42 rotate integrally, and this rotation causes the nut member 43, the holder 5 and the fork 6 connected to the nut member 43 to rise.

After that, when the nut member 43 hits the lower surface of the cross plate 35, no rotation occurs between the screw pipe 42 and the nut member 43, so only the screw shaft 41 rotates, and this rotation causes the screw pipe to rotate. 42, the nut member 43, and further the nut member 4
The fork 6 connected to the fork 3 also rises.

The above operations are carried out continuously, and similarly in the retraction operation, first only the nut member 43 is lowered, and then the screw shaft 42 is lowered. In other words, if we focus on the fork 6, the fork 6 will expand and contract in two stages.

FIGS. 6 to 9 show the procedure for mounting the above-described forklift on the bed of a truck. First, the legs 7 are folded from the normal state shown in FIG. 6. At this time, the forklift is supported by auxiliary wheels 10 and drive wheels 11. Next, adjust the height of the fork 6 to the truck bed 50.
After aligning the height with the groove of the attachment 51 installed in advance, move the forklift forward, close the left and right forks 6, and insert the fork 6 into the groove of the attachment 51 from the side as shown in FIG. engage. Next, as shown in FIG. 8, a driving force is applied in a direction to lower the fork 6. Then, since the position of the fork 6 is fixed by the attachment 51, the entire forklift other than the fork 6 is pulled up by its own driving force. When the lower end of the drive wheel 11 becomes higher than the top surface of the loading platform, move the forklift to the attachment 51.
At the same time, the forklift is rotated 180° in a horizontal plane and the forklift is mounted on the loading platform as shown in FIG. Thereafter, the forks 6, 6 are spread laterally and pulled out from the groove of the attachment 51, completing the transfer work to the loading platform of the forklift.

As mentioned above, the forklift mentioned in this embodiment can easily get on and off the loading platform of a truck or the like by using its own driving force, but this can be done by applying the spiral mechanism of the present invention. It can be said that this has made it possible to achieve this easily. In other words, if a cylinder unit were used instead of a screw mechanism, it would be necessary to use a unit that can exert a large driving force in the contraction direction, resulting in an increase in the size of the device.Additionally, a winding mechanism using wires and pulleys would have a relatively large cannot generate force in the downward direction of the fork.

In the embodiment, an example was shown in which the screw mechanism according to the present invention was applied to a fork lifting mechanism, but the application of the screw mechanism according to the present invention is not limited to this. Furthermore, although one screw pipe is shown in the illustrated example, a plurality of screw pipes may be arranged coaxially so as to be screwed together. In this way, the stroke can be further extended. However, in this case, the lead angle of the threaded part formed between the screw pipes is made different from the lead angle of other threaded parts to specify the order of the members to be threaded. Further, in the embodiment, the pitches of the inner threaded portion and the outer threaded portion are made equal and the thread diameters are different, thereby making the lead angle different, but the lead angle may be made different by other means. .

[0021]

[Effects of the Invention] As explained above, according to the present invention,
A threaded portion formed on the inner circumferential surface of the screw pipe is screwed into a threaded portion formed on the outer circumferential surface of the screw shaft, and a threaded portion formed on the nut member is screwed into the threaded portion formed on the outer circumferential surface of the screw pipe. Therefore, the spiral stroke can be increased. The lead angle of the inner threaded part, which is composed of the threaded part formed on the outer circumferential surface of the screw shaft and the threaded part formed on the inner circumferential surface of the screw pipe, and the threaded part formed on the outer circumferential surface of the screw pipe. Since the lead angle of the outer threaded part made up of the threaded part formed on the nut member is different, it is possible to decide which member is screwed in first, and prevents unexpected movement of the member. This can be prevented.

[Brief explanation of the drawing]

[Fig. 1] Side view of a forklift truck to which a screw mechanism according to the present invention is applied

[Figure 2] Cross-sectional view of the mast of the forklift seen from the front

[Fig. 3] Enlarged sectional view of the screw mechanism according to the present invention

[Fig. 4] An enlarged perspective view of the main parts of the screw mechanism according to the present invention.

[Figure 5] Developed view of threaded part

[Figure 6] Diagram for explaining the procedure for loading a forklift onto the truck bed

[Figure 7] Diagram for explaining the procedure for loading a forklift onto the truck bed

[Figure 8] Diagram for explaining the procedure for loading a forklift onto the truck bed

[Figure 9] Diagram for explaining the procedure for loading a forklift onto the truck bed

[Explanation of symbols]

3... Mast, 4... Spiral mechanism, 6... Fork, 41... Screw shaft, 42... Screw pipe, 43... Nut member, 41a, 42a, 42b, 43a... Threaded portion.

Claims (4)

[Claims] [Claim 1] A screw mechanism in which the rotation of one member screwed together is restricted and the other member is rotated to cause these members to move linearly relative to each other, comprising:
This screw mechanism includes a screw shaft having a threaded portion formed on the outer circumferential surface, a threaded portion formed on the inner circumferential surface and the outer circumferential surface, and the threaded portion formed on the inner circumferential surface forming a threaded portion formed on the outer circumferential surface of the screw shaft. It consists of a screw pipe that is screwed together, and a nut member that is screwed into a threaded part formed on the outer peripheral surface of the screw pipe, and the threaded part formed on the outer peripheral surface of the screw shaft and the threaded part formed on the inner peripheral surface of the screw pipe. The threaded portion formed on the outer peripheral surface of the screw pipe and the threaded portion formed on the nut member constitute an outer threaded portion, and the lead angle of the inner threaded portion and the threaded portion formed on the nut member constitute an inner threaded portion. A screw mechanism characterized in that the lead angle of the outer threaded portion is different. 2. The screw mechanism according to claim 1, wherein the inner threaded portion and the outer threaded portion have equal pitches and different thread diameters, thereby making the lead angles different. . 3. A plurality of screw pipes interposed between the screw shaft and the nut member are arranged coaxially, and the lead angle of the threaded portion formed between these screw pipes is also the same as that of the other threaded portions. The screw mechanism according to claim 1 or 2, characterized in that the lead angle is different from the lead angle. 4. The screw mechanism according to claim 1, wherein the screw mechanism is provided in a mast of a forklift.