JP2003190755A - Shaft sealing device for mixer - Google Patents

Abstract

(57) [Summary] (Modification) [PROBLEMS] A shaft sealing device of a mixing shaft in a mixing machine such as a concrete mixer for mixing a material in a mixing tank by rotating a mixing shaft with a plurality of mixing blades attached thereto. Automatic adjustment of the pressing force of the gland packing according to the size of the gap between the gland packing forming the external seal and the rotating sliding surface of the mixing shaft. A shaft seal of a mixing shaft for preventing leakage from a mixing tank includes an inner seal and an outer seal each formed of a gland packing, and a seal for each shaft.
Two seal holders 22 and 26 for pressing the first and second seals 23, pressing means 50 for applying a pressing force to the two seal holders 22 and 26, and an axial direction between the inner seal 21 and the outer seal 23 are formed. The compressed fluid chamber 31 and the outer seal 2
A detecting means 32 for detecting the size of the gap between the mixing shaft 3 and the mixing shaft 11; and a pressing force control means 60 for adjusting the pressing force of the pressing means 50 in accordance with the detection value of the detecting means 32.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shaft sealing device for a mixing shaft in a mixer such as a concrete mixer which mixes materials in a mixing tank by rotating a mixing shaft having a plurality of mixing blades.

[0002]

2. Description of the Related Art In sealing a shaft portion between a rotating mixing shaft and a tank wall of a mixing tank, a structure is adopted in which a compressed fluid is supplied to the sealing portion to prevent a material to be mixed from entering. For example,
There is JP-A-9-85730. According to this, a flow rate detector for detecting the flow rate of the compressed air to be supplied or a pressure detector for detecting the pressure of the compressed air to be supplied is arranged in the compressed air supply pipe for supplying the compressed air to the sealing mechanism. Installed to monitor the condition of compressed air sent to the seal mechanism and immediately issue an alarm if there is an abnormality such as a stop of compressed air supply or leakage to the outside, which facilitates maintenance management of the mixer. Is.

[0003]

However, it is merely to monitor the state of compressed air sent to the seal mechanism, and to accurately monitor whether the sent compressed air is performing the sealing function in a normal state. It was not possible, and there was a problem that the mortar had already penetrated into the seal when the abnormal alarm was issued. Furthermore, when an alarm is issued, it is necessary to inspect the abnormal part each time and re-tighten the gland packing. The present invention detects the size of the gap between the gland packing forming the external seal and the rotary sliding surface of the mixing shaft, and adjusts the pressing force of the gland packing according to the change in the size of the gap. To aim.

[0004]

In a mixer in which a mixing shaft having a plurality of mixing blades attached thereto is supported by penetrating through the wall of the mixing tank, a shaft seal of the mixing shaft for preventing leakage from the mixing tank is provided. An inner seal and an outer seal each formed of a gland packing, two seal retainers that press the respective seals, a pressing means that applies a pressing force to the two seal retainers, and an axial direction of the inner seal and the outer seal. And a detection means for detecting the size of the gap between the external seal and the mixing shaft, and a pressing force for adjusting the pressing force of the pressing means in accordance with the detection value of the detection means. It is characterized by comprising a control means.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the shaft seal device for a mixer according to claim 1 of the present invention, the size of the gap between the external seal and the mixing shaft is detected, and if the gap increases due to use, the value is dealt with. The inner and outer seals are adjusted to increase the pressure to reduce the gap, and if the gap becomes too small, the pressure to the inner and outer seals is weakened to adjust to the optimum gap. It As a result, the optimum gap is always maintained, and the compressed air supplied to the compressed fluid chamber is jetted toward the inside of the mixing tank without leaking to the outside to reliably prevent the intrusion into the seal portion. Further, the internal pressure of the compressed fluid chamber is maintained at a predetermined pressure to completely prevent invasion from the outside. The shaft seal device for a mixer according to claim 2 has a structure in which the amount of deformation of the outer seal due to the pressing force from the pressing means is always larger than the amount of deformation of the inner seal by providing a step on the mixing shaft. Then, the pressing force of the pressing means is adjusted.

According to a third aspect of the present invention, there is provided a shaft seal device for a mixer, which detects the size of the gap between the outer seal and the mixing shaft by the pressure of the compressed fluid chamber formed between the inner seal and the outer seal in the axial direction. Is. According to a fourth aspect of the present invention, the shaft seal device for a mixer detects the size of the gap between the outer seal and the mixing shaft by the load amount of the mixing shaft drive source. According to a fifth aspect of the present invention, in the shaft seal device of the mixer, the size of the gap between the external seal and the mixing shaft is detected by the temperature change near the external seal.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a shaft seal portion of a concrete mixer which supports a mixing shaft having a plurality of mixing blades penetrating a tank wall of a mixing tank, and a collar 12 is fixed to a rotating mixing shaft 11 to rotate the shaft. A housing 14 and a seal plate 15 are fixed to the side wall 13 of the stationary mixing tank through the housing. Collar 12 and seal plate 15 are 0.5 mm
There are some gaps. Two rows of gland packings forming an inner seal 21 are inserted inside the mixing tank of the collar 12, and an inner seal retainer 22 having a structure for pressing the gland packings against the end surface of the seal plate 15 is provided. . Two rows of gland packings that form the outer seals 23 are attached to the outer side of the mixing tank of the collar 12, and a fixing member 24 that fixes the gland packings is mixed via fixing bolts 25 at the outer end of the gland packings. An external seal retainer 26 is provided which is supported on the side wall of the tank and has a structure for pressing the gland packing against the end surface of the fixing member 24. Further, between the inner seal 21 and the outer seal 23, a compressed fluid chamber 31 formed by the collar 12, the inner seal retainer 22 and the outer seal retainer 26 is formed, and the compressed fluid supply pipe is provided via the inner seal retainer 22. 41 is connected, and a pressure adjusting valve 42 and a flow rate adjusting valve 43 are arranged in the middle of the piping. In the present embodiment, the case where the compressed fluid source is compressed air is described. Therefore, in the middle of the supply pipe, the positive level 44 for dropping oil to the compressed air to be supplied and supplying it to the gland packing is provided.
Are installed. Further, a pressure gauge is arranged in the compressed fluid chamber 31 as a pressure detector 32 for detecting the internal pressure of the compressed fluid chamber. Whether the compressed fluid supplied to the compressed fluid chamber is gas or fluid is selected according to the materials to be mixed.

The inner seal retainer 22 and the outer seal retainer 26 form an air chamber 51 sealed by an O-ring and are formed in a cylinder structure that slides in the axial direction, and compressed air is supplied to the air chamber. A supply pipe 52 for connecting the inner seal retainer and the outer seal retainer is pressed by the air pressure of the compressed air.
Further, the supply pipe 52 is provided with a pressure adjusting valve 53 and a discharge pressure valve 54 for adjusting the supply pressure. Therefore, the pressing means can change the thrust of the cylinder by changing the pressure of the supplied air, and can always adjust the pressing force of the two seal retainers. Further, there is provided a pressing force control means 60 for adjusting the pressing force of the inner seal and the outer seal in response to the fluctuation of the internal pressure of the compressed fluid chamber 31,
The pressing force control means is a pressure gauge that is a pressure detector 32, a calculator 72 that calculates the air pressure to be supplied to the pressing means from the amount of change in the pressure signal from the pressure gauge, and the pressure of compressed air that is supplied to the pressing means. Adjusting valve 53 and exhaust pressure valve 54 for adjusting
Consists of.

When the gap between the outer seal 23 and the collar 12 becomes large, the compressed fluid in the compressed fluid chamber leaks to the outside through the sliding surface of the outer seal and the internal pressure of the compressed fluid chamber 31 decreases, so that the pressure gauge The pressure value drops. The calculator 72 calculates the air pressure to be supplied to the pressing means from the degree of decrease from the preset set pressure, operates the pressure adjusting valve 53 to increase the air pressure supplied to the air chamber 51 of the pressing means, and the internal seal and The amount of deformation is increased by increasing the pressing force on the outer seal. If the pressing force becomes excessive and the gap becomes too small, the internal pressure of the compressed fluid chamber 31 rises and the pressure gauge detects a pressure value higher than the set pressure. The degree of decrease in the air pressure supplied to the pressing means is calculated, and the pressure adjusting valve 53 is operated according to the degree of increase in the internal pressure to reduce the supply pressure and the exhaust pressure valve 54.
Is operated to lower the air pressure in the air chamber 51 and weaken the pressing force of the inner seal and the outer seal to maintain the optimum gap.

In this embodiment, the collar 12 is provided with a step portion 70 having a small diameter on the outer seal side, and an inner seal is attached to the rotary sliding surface of the large diameter portion so that the rotary sliding surface of the small diameter portion can be mounted. An external seal is attached to form the compressed fluid chamber 31. This is because the gland packing forming the outer seal has a smaller circumferential cross-sectional area than the gland packing forming the inner seal, and the pressure of the air chamber 51, which is the pressing source of the pressing means 50, causes the external seal presser 26 to pass through. This is because the surface pressure of the acting outer seal is always higher than the surface pressure of the inner seal acting through the inner seal retainer 22. Due to this surface pressure difference, the gap of the outer seal 23 is always smaller than the gap of the inner seal 21, and the compressed fluid in the compressed fluid chamber 31 flowing out through the outer seal becomes extremely small. On the other hand, when the mixing shaft is not provided with a stepped portion, the axial cross-sectional area of the gland packing forming the outer seal is made smaller than that of the gland packing forming the inner seal, and the same pressing force acts on both seals. In addition, the surface pressure of the outer seal is made larger than the surface pressure of the inner seal. Therefore, similar to the above, due to this surface pressure difference, the gap of the outer seal is always smaller than the gap of the inner seal, and the compressed fluid in the compressed fluid chamber flowing out through the outer seal becomes extremely small.

Next, a second embodiment will be described with reference to FIG. In the present embodiment, the change in the gap of the external seal in the first embodiment is detected by the load amount of the mixed shaft drive source when there is no load. The pressing means 50 of the present embodiment is composed of an inner seal retainer 22, an outer seal retainer 26, and three air cylinders 55 arranged between the respective seal retainers, and has a structure in which the respective seal retainers are pressed against each other. Has been done. Then, the pressing force control means 60 includes an ammeter provided as a load detector 33 in a drive source (not shown) that applies a rotational force to the mixing shaft 11, a no-load current value from the ammeter, and a preset current value set in advance. And a pressure adjustment valve 53 and a discharge pressure valve 54 for adjusting the pressure of the compressed air supplied to the air cylinder. If the gap between the outer seal 23 and the collar 12 is increased, the sliding resistance of the sliding portion is reduced and the load current value of the drive source is reduced. On the contrary, when the gap becomes smaller, the sliding resistance increases and the load current value increases. From the current value and the set value that fluctuate depending on the size of this gap, the air cylinder 5
The air pressure supplied to 5 is calculated, the supply pressure is increased / decreased to adjust the pressing force of the internal seal and the external seal, and the optimum gap is maintained to maintain the internal pressure of the compressed fluid chamber.

A third embodiment will be described with reference to FIG. In this embodiment, the change in the gap between the inner seal and the outer seal in the first embodiment is detected by the temperature change in the vicinity of the outer seal. The pressing means 50 of this embodiment has a structure in which a turnbuckle 56 is disposed between the inner seal retainer 22 and the outer seal retainer 26, and the two seal retainers are moved in the axial direction by the rotation of the nut. A motor 57 for applying a rotational force to the nut of the buckle and a rotation controller 53 for the motor are provided. And the external seal holder 2
In the vicinity of the outer seal 6 is provided a thermometer as a temperature detector 34 for detecting the temperature change of the outer seal.
The pressing force control means 60 calculates the rotational speed of the nut of the turnbuckle 56 by comparing and calculating the thermometer, the temperature signal from the thermometer and a preset temperature.
2 and a rotation controller 53 that drives the motor 57 based on a command from the arithmetic unit.

Then, the thermometer detects the temperature in the vicinity of the external seal and sends a temperature signal to the arithmetic unit, and the arithmetic unit sends an electric signal, which is a rotation command of the motor 57, to the rotation controller 53 according to the degree of variation of the temperature. The feed motor 57 is rotated normally and reversely to increase or decrease the pressing force of the pressing means, and the pressing forces of the inner seal and the outer seal are adjusted to maintain the optimum gap. That is, if the gap between the gland packing and the sliding surface is too small, the sliding resistance increases and high frictional heat is generated to raise the temperature near the gland packing. Conversely, if the gap is too large, the sliding resistance decreases. The frictional heat is reduced and the temperature rise in the vicinity of the gland packing is reduced. In response to this temperature variation, the pressing force control means 60 drives the motor 57 to rotate the nut of the turnbuckle forward and backward to rotate the nut. The pressing force of the seal retainer is controlled to maintain the gap and maintain the internal pressure of the compressed fluid chamber. Naturally, the frictional heat is generated during the operation of the mixer and is transferred to the external seal holder by heat conduction and is radiated to the outside air. Therefore, the pressing force control means is operated once a day after the operation for a certain time. It is preferably activated to check the gap. Further, it is preferable that the temperature change takes into consideration the outside air temperature and the temperature of the immediately preceding outer seal holder.

[0014]

According to the shaft seal device of the mixer of the first aspect, the increase of the compressed fluid ejected toward the inside of the mixing tank is automatically suppressed and the internal pressure of the compressed fluid chamber is kept constant. Therefore, the sealing performance is surely exhibited. Moreover, since the pressing force can be automatically adjusted by the pressing means, maintenance such as retightening is unnecessary. Furthermore, the useless amount of compressed fluid supplied is eliminated, and energy consumption can be reduced. Further, since the excessive surface pressure on the sealing material can be avoided, the durability of the sealing material is significantly improved. According to the shaft seal device of the mixer of claim 2, since the gap of the outer seal is always smaller than the gap of the inner seal, the amount of leakage to the outside is reduced and the sealing performance is further improved. You can According to the shaft seal device for a mixer of claim 3, when the fluid is supplied to the compressed fluid chamber, the size of the gap can always be detected, so that the internal pressure of the compressed fluid chamber can always be kept constant. . According to the shaft seal device of the mixer of claims 4 and 5,
Since the sliding resistance between the sealing material and the mixed shaft can be maintained, excessive surface pressure on the sealing material can be avoided, and the durability of the sealing material is further improved.

[Brief description of 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]

11 ・ ・ ・ Mixed axis 13 ... Side wall of mixing tank 21 ・ ・ ・ Internal seal 22 ・ ・ ・ Internal seal holder 23 ... External seal 26 ・ ・ ・ External seal holder 31 ... Compressed fluid chamber 32 ... Pressure detecting means (detecting means) 33 ・ ・ ・ Load detection means (detection means) 34 Temperature detecting means (detecting means) 50 ... Pressing means 60 ... Pressing force control means 70 ... Step

Continued front page    F-term (reference) 4G037 DA03 EA03                 4G078 AA13 AB02 BA01 CA01 CA05                       CA15 CA17 DA00 EA03

Claims (5)

[Claims] 1. In a mixer in which a mixing shaft having a plurality of mixing blades attached thereto is supported by penetrating through a tank wall of the mixing tank, each shaft seal of the mixing shaft for preventing leakage from the mixing tank has a gland packing. An inner seal and an outer seal formed by, and two seal retainers that press each seal,
A pressing unit that applies a pressing force to the two seal retainers, a compressed fluid chamber formed between the inner seal and the outer seal in the axial direction, and a detection unit that detects the size of the gap between the outer seal and the mixing shaft. A shaft seal device for a mixer, comprising: a pressing force control unit that adjusts the pressing force of the pressing unit according to the detection value of the detection unit. 2. The mixing shaft is provided with an internal seal attached to a large diameter portion and an external seal attached to a small diameter portion, the step portion having a large diameter on the mixing tank side. A shaft seal device for a mixer according to claim 1. 3. The shaft seal device for a mixer according to claim 1, wherein the detecting means is formed in a pressure detector for detecting the pressure in the compressed fluid chamber. 4. A shaft seal device for a mixer according to claim 1, wherein said detection means is formed in a load detector for detecting a load of a drive source for the mixing shaft. 5. A shaft seal device for a mixer according to claim 1, wherein said detection means is formed in a temperature detector for detecting a temperature change near the outer seal.