JP3980344B2 - Concrete mixer shaft seal structure - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a seal for a rotating shaft of a concrete mixer for kneading ready-mixed concrete.
[0002]
[Prior art]
For the mixing of ready-mixed concrete, a gravity type in which a kneading tank rotates or a forced type having a kneading blade rotating in a fixed kneading tank is used. Some of these mixers have a structure in which a rotating shaft having kneading blades is inserted into a kneading tank, and various proposals have been made for sealing the rotating shaft portion of ready-mixed concrete in the kneading tank. In particular, in recent years, a gland packing is used instead of securing a sealing effect by grease.
For example, there is JP-A-8-25341. According to this, a lantern ring is arranged between two gland packings, air is supplied to the lantern ring, and the length of the inner and outer seal portions is changed so that the air is directed toward the kneading tank. It was intended to achieve a stronger sealing effect by facilitating the flow and suppressing outward leakage.
[0003]
[Problems to be solved by the invention]
On the other hand, in the present invention, the air supplied to the gland packing part is slightly ejected from the gap between the inner gland packing and the rotating shaft into the mixer to prevent the intrusion of concrete and to prevent the leakage to the outside. An object is to change the amount of deformation of the gland packing at the location so that the gap between the inner side gland packing and the rotating shaft is larger than that on the outer side, thereby ensuring the sealing action of the kneading tank.
[0004]
[Means for Solving the Problems]
The present invention comprises a shaft seal structure for a concrete mixer, comprising a rotating shaft having kneading blades in a kneading tank, wherein the rotating shaft is sealed by a gland packing and air pressure as follows.
(A) Two gland packings are arranged in the axial direction of the rotating shaft,
(A) Two pressing members for pressing the two gland packings are provided,
(C) a pressing source for providing an axial force to the two pressing members is provided;
(D) Air supply means for supplying air is provided between the two gland packings in the axial direction;
(E) the rotating shaft is formed in a stepped portion, and two gland packings are inserted into different diameter portions,
(F) The rotating shaft formed in the stepped portion is formed with a large diameter on the kneading tank side ,
(G) The deformation amount of the inner gland packing inserted into the large diameter portion having a large diameter is made smaller than the deformation amount of the outer gland packing inserted into the small diameter portion having a small diameter .
[0005]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, the main purpose is to make the gap between the outer gland packing provided on the outer side from the kneading tank and the rotating shaft smaller than the gap of the inner gland packing by changing the deformation amount of the two gland packings.
For this purpose, a step portion is formed on the rotating shaft, and the difference in deformation amount when the two gland packings are pressed with equal force, or the difference in deformation amount of the gland packing caused by the difference in pressing force is utilized. Is.
[0006]
【Example】
The embodiment will be described with reference to the drawings.
FIG. 1 is a partial cross-sectional view of a first embodiment showing a seal portion of a rotating shaft 2 penetrating a kneading tank 1 of a concrete biaxial mixer.
[0007]
The seal part of the rotary shaft 2 is equipped with a bush 3 that is easy to replace in consideration of wear and the like. The bush 3 has a large diameter part 4 with a large diameter on the kneading tank 1 side and a small diameter on the outside. It is formed on the step portion 22 of the small diameter portion 5. A seal wall 6 that forms the side wall of the kneading tank 1 is attached to the outer diameter of the large-diameter portion 4, and an inner gland packing 7 is inserted therebetween, and this inner gland packing is supported by an inner seal presser 8. It is pressed toward the kneading tank 1 in the axial direction of the rotating shaft 2. On the other hand, an outer gland packing 9 is inserted between the outer diameter of the small-diameter portion 5 and the inner seal presser 8 and is pressed in the same direction as the inner gland packing 7 by the outer seal presser 10. .
It is desirable that the two seal retainers 8 and 10 have a structure that can be disassembled into two parts in consideration of maintenance such as replacement of the gland packing.
[0008]
The force acting on the two seal retainers 8.10 is generated by a pressure source 11 fixed to the seal wall 6. The pressing source 11 includes three studs 12 that are attached to the seal wall 6 at three equal circumferential positions, a spring 13 that is inserted into the stud 12 and generates a constant spring pressure, and a pressing force. It consists of an adjustment nut 14 to be adjusted.
[0009]
An air supply means 15 for supplying air to the air chamber 17 between the two gland packings is connected to the inner seal presser 8 via an air pipe 16 from a compressor (not shown), and rotation of the two gland packings is performed. It is guided between the axial directions of the shaft 2.
[0010]
Next, the operation will be described.
The outer seal presser 10 directly receives the axial acting force of the pressing source 11 and presses the outer gland packing 9. At this time, the outer seal retainer 10, the outer gland packing 9, the inner seal retainer 8, and the inner gland packing 7 are arranged in series in the axial direction of the rotary shaft 2. An equal pressing force is applied. However, the two gland packings are inserted into portions having different diameters, the circumferential packing lengths of the gland packings are different, and the pressing force acting per unit length is different. For this reason, a difference arises in the deformation amount of the two gland packings which received the equal pressing force. That is, the deformation amount of the inner gland packing 7 inserted into the large diameter portion 4 having a large diameter is smaller than the deformation amount of the outer gland packing 9 inserted into the small diameter portion 5 having a small diameter, and the resulting bush 3 And the gap of the inner gland packing 7 becomes larger.
Therefore, if the pressure source 11 is adjusted to such an extent that air leakage from the outer gland packing 9 does not occur, the air supplied to the air chamber 17 between the two gland packings is released from a slight gap in the inner gland packing 7. It can be ejected into the kneading tank 1. This prevents the intrusion of concrete from the inner gland packing 7.
[0011]
FIG. 2 is a partial cross-sectional view showing a second embodiment.
In this embodiment, the pressing source 11 in the first embodiment is formed in one fluid pressure cylinder, and air is used as the fluid pressure. The cylinder 18 is configured such that the axial direction of the rotary shaft 2 is restricted by the stud 12 and the piston 19 that also serves as an outer seal presser always presses the two gland packings.
Since a cylinder is used as the pressing source, a constant pressing force is always applied to the gland packing, and adjustment work such as retightening due to wear of the gland packing can be saved greatly.
In consideration of maintenance, the cylinders are not formed as one as in the present embodiment, but can be provided with a plurality of three or four.
[0012]
FIG. 3 is a partial sectional view showing the third embodiment.
In this embodiment, an air chamber provided between the two gland packings in the above-described embodiment is formed in the cylinder chamber 21, and the two gland packings are deformed by the air pressure supplied to the cylinder chamber 21. .
[0013]
The feature of this embodiment is that it also serves as an inner seal presser by inserting two gland packings into portions having different diameters of the rotary shaft 2 and making the step portion 22 of the rotary shaft 2 a part of the cylinder chamber 21. The difference in the amount of deformation is caused by changing the pressing force of the two gland packings depending on the area difference between the piston area S1 of the inner piston 23 and the piston area S2 of the outer piston 24 that also serves as an outer seal holder.
[0014]
The acting force for pressing the inner gland packing 7 inserted into the large diameter portion 4 is smaller than the outer gland packing 9 inserted into the small diameter portion 5 by an amount corresponding to the area S3 of the step portion 22, The deformation amount of the inner gland packing 7 is smaller than that of the outer gland packing 9, and the gap of the inner gland packing 7 becomes larger when the gap with the rotating shaft 2 is compared.
Further, as described in the first embodiment, the circumferential length of the inner gland packing 7 is long, so that a difference in gap is further generated in combination with a difference in acting force. In other words, even if the gap between the outer gland packings 9 is made small enough to rotate, the gap between the inner gland packings 7 can be set to such an extent that minute air can be ejected.
[0015]
Another embodiment.
In the above embodiment, the two gland packings having the same axial length are used, but by increasing the length of the outer gland packing, a minute gap can be secured long and air leakage can be prevented. .
Further, although the gland packings having the same cross-sectional area in the circumferential direction are used, a gland packing having a larger cross-sectional area is effective for reducing the deformation amount with the same acting force.
【The invention's effect】
The seal of the rotating shaft part in the concrete mixer can be made perfect without leaking the concrete, and the structure can be made excellent in durability.
[Brief description of the drawings]
FIG. 1 is a partial sectional view showing a first embodiment of the present invention.
FIG. 2 is a partial sectional view showing a second embodiment of the present invention.
FIG. 3 is a partial sectional view showing a third embodiment of the present invention.
[Explanation of symbols]
1 Kneading tank 2 Rotary shaft 7-way gland packing 8 Inner seal presser (pressing member)
9 Outer gland packing 10 Outer seal presser (pressing member)
11 Press source 13 Spring 15 Air supply means 18 Cylinder (Press source)
21 Cylinder chamber 22 Step

Claims (5)

A shaft seal structure for a concrete mixer comprising a rotating shaft having a kneading blade in a kneading tank, and a sealing structure in which the rotating shaft is performed by gland packing and air pressure as follows:
(A) Two gland packings are arranged in the axial direction of the rotating shaft,
(A) Two pressing members for pressing the two gland packings are provided,
(C) a pressing source for providing an axial force to the two pressing members is provided;
(D) Air supply means for supplying air is provided between the two gland packings in the axial direction;
(E) the rotating shaft is formed in a stepped portion, and two gland packings are inserted into different diameter portions,
(F) The rotating shaft formed in the stepped portion is formed with a large diameter on the kneading tank side ,
(G) The deformation amount of the inner gland packing inserted into the large diameter portion having a large diameter is made smaller than the deformation amount of the outer gland packing inserted into the small diameter portion having a small diameter.  2. The concrete mixer shaft seal structure according to claim 1, wherein the pressing source is configured to generate an axial force by a spring pressure.  2. The concrete mixer shaft seal structure according to claim 1, wherein the pressing source is configured to generate an axial force by a fluid pressure cylinder.  2. The shaft seal structure for a concrete mixer according to claim 1, wherein the gland packing has an equal cross-sectional area in the circumferential direction.  The shaft seal structure for a concrete mixer according to claim 1, wherein the axial lengths of the two gland packings are equal.

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