JP3496808B2 - Ram cylinder - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ram cylinder for elevating and lowering a work lifting fork of a lift truck or an elevating mast for supporting the fork.

[0002]

2. Description of the Related Art Conventionally, as a lift truck of this type, there is one disclosed in Japanese Patent Application Laid-Open No. 5-170315, and an example thereof will be described with reference to FIGS. 8 and 9. A vehicle body 2 having a drive tire 1 will be described. A lift device 3 is provided at the front part of the vehicle body, and a pair of straddle legs 4 extend forward from both sides of the lower part of the vehicle body 2. A pair of front and rear urethane rubber road wheels 5 are provided at the tips of the straddle legs 4.
Are provided, and guide rollers 7 and 8 are attached outward at the front end of each straddle leg 4 and the rear ends of both side surfaces of the vehicle body 2.

The lift device 3 is provided with a plurality of stages (two stages in this embodiment) of masts 10 and 11, an elevating body 12 which is vertically movable on the elevating mast 11, and a front face of the elevating body 12. A horizontal moving body 14 horizontally moved by a pair of upper and lower racks 13, a swinging body 16 that can swing around a vertical axis 15 provided at the tip of the horizontal moving body 14, and the swinging body 1
6 has a pair of fork 17 for lifting the work, and the direction of the fork 17 is 3 in the forward and leftward directions.
The direction can be changed (see FIG. 9).

As shown in FIG. 10 (a), a ram cylinder 19 for raising and lowering the fork 17 and the lifting mast 11 is provided, which has a hydraulic port 21 on one end plate portion 20a of the cylinder 20. A through hole 22 is provided in the other end plate portion 20b, and a piston rod 24 integrally connected to a piston 23 in the cylinder 20 is inserted into the through hole 22 so as to be extendable and contractible. The cylinder 20 of the fork-side ram cylinder 19 is connected to the lifting mast 11, and the piston rod 24 thereof is connected to the rotating body 26 that engages with the cord 25 that connects the lifting mast 11 and the fork 17, and the lifting The cylinder 20 of the mast-side ram cylinder 19 is connected to the fixed mast 10, and its piston rod 24 is connected via a connecting body 27. And it is connected to the lifting mast 11.

In the above structure, as shown in FIG. 10 (a), the hydraulic pump 28 is driven from the state where the fork 17 and the lifting mast 11 are lowered, and each ram is moved from the hydraulic tank 29 through the switching valve 30. Cylinder 2 of cylinder 19
By supplying pressure oil to the inside of the fork 1, the piston rod 24 is extended as shown in FIG.
7 and the lifting mast 11 are raised (see the phantom line in FIG. 8),
On the contrary, by switching the switching valve 30 and returning the pressure oil in the cylinder 20 of each ram cylinder 19 into the hydraulic tank 29, the fork 17 and the lifting mast 11 can be lowered.

[0006]

SUMMARY OF THE INVENTION In the above conventional configuration,
When the piston rod 24 is fully extended, the piston 2
3 impacts the other end plate 20b.

Therefore, it is considered that when an air reservoir is formed in the cylinder 20 and the piston rod 24 is fully extended, the air in the air reservoir is compressed and cushioned by the cushioning action generated thereby. However, in this case, it is difficult to adjust the air filling amount to properly set the cushioning action, and the structure becomes complicated, resulting in high manufacturing cost.

In view of the above-mentioned conventional drawbacks, an object of the present invention is to provide a ram cylinder which has a simple structure and can reliably absorb the impact when the piston rod is fully extended.

[0009]

To achieve the above object, the invention according to claim 1 is such that a hydraulic port is provided in one end plate of the cylinder and a through hole is provided in the other end plate. , A piston rod integrally connected to a piston in the cylinder is inserted into the through hole so as to be capable of expanding and contracting, and by supplying pressure oil into the cylinder from the hydraulic port, the piston rod is extendedly moved. In the ram cylinder described above, a communication passage that connects a first hydraulic chamber between the piston and the one end plate portion to a second hydraulic chamber between the piston and the other end plate portion is formed in the piston rod. An orifice connecting from the second hydraulic chamber to the through hole is formed in the other end plate portion, and the piston rod is extended to move the piston to the other end plate portion. When approached, the other end plate portion closes the communication passage to seal the second hydraulic chamber, and the pressure oil in the sealed second hydraulic chamber passes through the orifice to the first hydraulic chamber side. The feature is that he tried to return it.

In the above structure, by supplying pressure oil from the hydraulic port into the first hydraulic chamber of the cylinder,
Pressure oil is also supplied from the hydraulic chamber to the second hydraulic chamber through the communication passage, and the piston rod is extended and moved via the piston by the hydraulic pressure of the hydraulic oil supplied to the first hydraulic chamber. Immediately before being fully extended, the other end plate of the cylinder closes the communication passage to seal the second hydraulic chamber,
The pressure oil in the sealed second hydraulic chamber is gradually returned to the first hydraulic chamber side through the orifice to generate a cushioning action, and the cushioning action cushions the impact when the piston rod is fully extended. To do.

In this case, the cushion rod ensures the shock when the piston rod is fully extended with a simple structure in which the communicating passage is formed in the piston rod and the orifice is formed in the other end plate of the cylinder. Can be relaxed.

According to a second aspect of the present invention, in the first aspect of the present invention, the sealing material disposed on the inner peripheral surface of the through hole has a lip that elastically adheres to the outer peripheral surface of the piston rod. A second hydraulic chamber side opening of the communication passage facing the lip is opened in an annular groove formed on the outer peripheral surface of the piston rod.

According to the above construction, when the piston rod is expanded and contracted so that the second hydraulic chamber side opening of the communication passage faces the lip, the entire lip elastically deforms and enters the annular groove, Since the lip does not partly enter the second hydraulic chamber side opening and is not damaged, the sealing effect can be reliably maintained for a long period of time.

According to a third aspect of the present invention, in the second aspect of the invention, the outer peripheral edge portion of the annular groove is chamfered to form a tapered surface on the outer peripheral edge portion.

According to the above construction, the lip is elastically deformed smoothly along the tapered surface formed on the outer peripheral edge of the annular groove, so that the elastic force of the lip can be maintained for a long period of time.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the inner peripheral surface of the seal material disposed on the inner peripheral surface of the through hole is a flat seal surface parallel to the outer peripheral surface of the piston rod. A pressing member for pressing the sealing surface against the outer peripheral surface of the piston rod is externally fitted to the sealing material.

According to the above construction, since the inner peripheral surface of the seal member is a flat seal surface parallel to the outer peripheral surface of the piston rod, the seal surface is damaged by the second hydraulic chamber side opening of the communication passage. Moreover, since the sealing surface is pressed against the outer peripheral surface of the piston rod by the pressing member, the sealing effect can be reliably maintained.

According to a fifth aspect of the present invention, in the fourth aspect of the invention, the pressing member is an O-ring.

According to the above construction, since the existing O-ring is used as the pressing member, the manufacturing cost can be reduced.

According to a sixth aspect of the present invention, in the invention according to any one of the first to fifth aspects, the cylinder is arranged on a lift truck, and the piston rod is connected to a work lifting fork of the lift truck. It is characterized by

According to the above construction, the shock when the fork of the lift truck is lifted to the maximum can be alleviated by the cushion effect.

According to a seventh aspect of the invention, in the invention according to any one of the first to sixth aspects, the cylinder is arranged on a lift truck, and the piston rod is connected to a lift mast of the lift truck. It is characterized by that.

According to the above construction, the shock when the lifting mast of the lift truck is lifted to the maximum can be alleviated by the cushioning action.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 show a ram cylinder which is an embodiment of the present invention, in which a piston 2
3 is formed in the piston rod 24 from the first hydraulic chamber 32 between the one end plate portion 20a and the second hydraulic chamber 33 between the piston 23 and the other end plate portion 20b.
Orifice 3 connecting from second hydraulic chamber 33 to through hole 22
5 is formed on the other end plate portion 20b.

As shown in FIG. 1, the piston rod 24 has a rod body 24 a having a diameter slightly smaller than the through hole 22 of the cylinder 20, a rod small diameter portion 24 b hanging from the lower surface of the rod body 24 a, and a piston 23. The boss 24c is integrally formed and externally fitted and fixed to the rod small diameter portion 24b. The boss 24c has the same diameter as the rod body 24a.

As shown in FIGS. 1 and 3, the communication passage 34 has a plurality of vertical holes 34a penetrating the boss 24c at predetermined circumferential intervals, and a predetermined circumferential interval at the upper end of the boss 24c. And a plurality of lateral grooves 34b which are formed radially and communicate with each vertical hole 34a.

As shown in FIGS. 1 and 2, the other end plate portion 20b is composed of an annular body 37 screwed into the end portion of the cylinder 20 and a support ring 39 for supporting a sealing material 38. The support ring 39 is interposed between the annular body 37 and the concave step portion formed on the inner surface of the cylinder 20.

As shown in FIGS. 1 and 2, the orifice 35 has a diameter of, for example, 1 which penetrates the support ring 39 vertically.
It is formed by a vertical hole 35a of about mm and a horizontal hole 35b penetrating the supporting ring 39 in the radial direction and communicating with the vertical hole 35a.

In the above-mentioned structure, as shown in FIG. 1, the piston rod 24 is contracted to supply pressure oil from the hydraulic port 21 into the first hydraulic chamber 32 of the cylinder 20 so that the first hydraulic chamber Pressure oil is also supplied from 32 to the second hydraulic chamber 33 through the communication passage 34, and the piston rod 24 is extended and moved via the piston 23 by the hydraulic pressure of the pressure oil supplied to the first hydraulic chamber 32. Piston rod 2
4, the communication passage 34 is closed by the support ring 39 of the other end plate portion 20b, and the second hydraulic chamber 33 is hermetically closed immediately before the fourth hydraulic fluid is fully extended. The pressure oil in the chamber 33 gradually returns to the first hydraulic chamber 32 side from the communication passage 34 through the orifice 35 to generate a cushioning action, and the cushioning action causes an impact when the piston rod 24 is extended most. Alleviate.

In this case, the piston rod 24 is connected to the communication passage 3
4 is formed, and the other end plate portion 20b of the cylinder 20 is formed.
With a simple structure in which the orifice 35 is simply formed, the impact when the piston rod 24 is fully extended can be reliably mitigated.

Therefore, by using the ram cylinder 19 as a lifting drive source for the fork 17 and the lifting mast 11 of the lift truck shown in FIGS.
The shock when the 7 and the lifting mast 11 are raised to the maximum can be alleviated by the cushioning action.

As shown in FIGS. 5 and 6, the seal member 38 has a groove 39a formed in the inner peripheral surface of the support ring 39.
Has a lip 38a that is fitted into the piston rod 24 and elastically adheres to the outer peripheral surface of the piston rod 24, and the lateral groove (second hydraulic chamber side opening) 34b of the communication passage 34 facing the lip 38a is a boss of the piston rod 24. It is opened in an annular groove 40 formed on the outer peripheral surface of 24c (see FIG. 3).

According to the above construction, the piston rod 24 is expanded and contracted to move the lateral groove 34b of the communication passage 34 into the lip 38a.
, The entire lip 38a elastically deforms and enters the annular groove 40, and the lip 38a does not partially enter the lateral groove 34b and is damaged, so that the sealing effect is maintained for a long time. It can be maintained reliably.

As shown in FIG. 5, the outer peripheral edge of the annular groove 40 is chamfered to form a tapered surface 41 on the outer peripheral edge.

According to the above construction, the lip 38a is elastically deformed smoothly along the tapered surface 41, so that the elastic force of the lip 38a can be maintained for a long period of time.

FIG. 7 shows a main part of a ram cylinder 19 according to another embodiment of the present invention, in which a sealing material 38 is used.
Is formed into a rectangular cross section, and the inner peripheral surface of the seal member 38 is a flat seal surface 38b parallel to the outer peripheral surface of the piston rod 24, and the seal surface 38b is pressed against the outer peripheral surface of the piston rod 24. O-ring (pressing member) 42
Is externally fitted to the sealing material 38. Since the configuration other than the above is almost the same as that of the embodiment shown in FIGS. 1 to 4, the same parts are designated by the same reference numerals and the description thereof will be omitted.

According to the above structure, since the inner peripheral surface of the seal member 38 is the flat seal surface 38b parallel to the outer peripheral surface of the piston rod 24, the seal surface 38b is damaged by the lateral groove 34b of the communication passage 34. According to the test results, the durability of the sealing material 38 is better in the embodiment shown in FIG. 7 than in the embodiment shown in FIG. Moreover, since the sealing surface 38b is pressed against the outer peripheral surface of the piston rod 24 by the O-ring 42, the sealing effect can be reliably maintained. Moreover, since the existing O-ring 42 is used as the pressing member, the manufacturing cost can be reduced.

In the above structure, the O-ring 42 is used to press the sealing material 38. However, the O-ring 42 is not limited to this, and for example, an annular coil spring may be used.

In the above-described embodiment, it is preferable that the outer peripheral surface of the piston rod 23 which comes into contact with the seal member 38 is embossed to form a large number of smooth and extremely small recesses. Thereby, the durability of the sealing material 38 can be improved.

[0040]

According to the first aspect of the invention, the piston rod is maximally extended with a simple structure in which the communicating passage is formed in the piston rod and the orifice is formed in the other end plate of the cylinder. It is possible to reliably absorb the impact at the time by the cushion effect.

According to the second aspect of the invention, when the piston rod is expanded and contracted so that the second hydraulic chamber side opening of the communication passage faces the lip, the entire lip is elastically deformed and the annular groove is formed. Since the lip does not enter the inside of the second hydraulic chamber side opening and is not damaged,
The sealing effect can be reliably maintained for a long period of time.

According to the third aspect of the present invention, since the lip is elastically deformed smoothly along the tapered surface formed on the outer peripheral edge of the annular groove, the elastic force of the lip can be maintained for a long period of time. .

According to the invention as set forth in claim 4, since the inner peripheral surface of the seal member is a flat seal surface parallel to the outer peripheral surface of the piston rod, the seal surface is on the second hydraulic chamber side of the communication passage. There is no danger of being damaged by the opening,
Since the sealing surface is pressed against the outer peripheral surface of the piston rod by the pressing member, the sealing effect can be reliably maintained.

According to the fifth aspect of the invention, since the existing O-ring is used as the pressing member, the manufacturing cost can be reduced.

According to the sixth aspect of the present invention, the shock when the fork of the lift truck is fully raised can be alleviated by the cushioning action.

According to the seventh aspect of the invention, it is possible to absorb the shock when the lifting mast of the lift truck is maximally raised by the cushioning action.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a ram cylinder according to an embodiment of the present invention in a contracted state.

FIG. 2 is a view on arrow AA of FIG.

FIG. 3 is a view taken along the line BB of FIG.

FIG. 4 is a longitudinal sectional view of the ram cylinder in an extended state.

FIG. 5 is an enlarged vertical sectional view of the main part.

FIG. 6 is a view on arrow CC of FIG.

FIG. 7 is an enlarged vertical sectional view of a main part of a ram cylinder which is another embodiment of the present invention.

FIG. 8 is a side view of a lift truck using a ram cylinder.

FIG. 9 is a plan view of the same.

10A is a schematic explanatory view of a lift truck with a fork and a lifting mast lowered, and FIG. 10B is a schematic illustration of a lift truck with a fork and a lifting mast raised.

[Explanation of symbols]

11 Lifting mast 17 Work lifting fork 19 Ram cylinder 20 cylinders 20a One end plate of cylinder 20b The other end plate of the cylinder 21 Hydraulic port 22 Through hole 23 pistons 24 piston rod 32 First hydraulic chamber 33 Second hydraulic chamber 34 communication passage 34b Lateral groove of communication passage (second hydraulic chamber side opening) 35 Orifice 38 Seal material 38a Sealing material lip 38b Sealing surface of sealing material 40 annular groove 41 Tapered surface 42 O-ring (pressing member)

Claims (7)

(57) [Claims] 1. A hydraulic port is provided in one end plate of the cylinder, and a through hole is provided in the other end plate,
A piston rod integrally connected to a piston in the cylinder is inserted into the through hole so as to be capable of expanding and contracting, and by supplying pressure oil into the cylinder from the hydraulic port, the piston rod is extended and moved. In the ram cylinder, a communication passage is formed in the piston rod from the first hydraulic chamber between the piston and the one end plate portion to the second hydraulic chamber between the piston and the other end plate portion, An orifice connecting from the second hydraulic chamber to the through hole is formed in the other end plate portion, and when the piston rod is extended and moved to bring the piston closer to the other end plate portion, the other end plate is formed. Part closes the communication passage to seal the second hydraulic chamber, and returns the pressure oil in the sealed second hydraulic chamber to the first hydraulic chamber side through the orifice. Ram cylinder, characterized in that there was Unishi. 2. A second hydraulic chamber side opening of the communication passage facing the lip, in which a sealing material disposed on the inner peripheral surface of the through hole has a lip that elastically adheres to the outer peripheral surface of the piston rod. The ram cylinder according to claim 1, wherein the portion is opened in an annular groove formed on the outer peripheral surface of the piston rod. 3. The ram cylinder according to claim 2, wherein the outer peripheral edge portion of the annular groove is chamfered to form a taper surface on the outer peripheral edge portion. 4. An inner peripheral surface of a seal material arranged on the inner peripheral surface of the through hole is a flat seal surface parallel to the outer peripheral surface of the piston rod, and the seal surface is pressed against the outer peripheral surface of the piston rod. The ram cylinder according to claim 1, wherein a member is fitted on the sealing material. 5. The ram cylinder according to claim 4, wherein the pressing member is an O-ring. 6. The ram cylinder according to claim 1, wherein the cylinder is arranged on a lift truck, and the piston rod is connected to a work lifting fork of the lift truck. . 7. The ram cylinder according to claim 1, wherein the cylinder is arranged on a lift truck, and the piston rod is connected to a lifting mast of the lift truck.