RESULTS OF A STUDY OF THE LIFTING MECHANISM OF A PMM-2-TYPE MANIPULATOR

N. S. Kolodyazhnyi, L. T. Dvornikov

(Presented by the Department of Mining Machines and Mine Transport)

In modern designs of removable manipulators of the MBI-5u and MBM types, used for installing drilling machines, raising and lowering the manipulator boom is carried out by a manual drive and is a labor-intensive operation.

To mechanize this operation, the Department of Mining Machines and Mine Transport of the Tomsk Polytechnic Institute, in cooperation with the Tomsk Electromechanical Plant, created the PMM-1 lifting mechanism with an electric drive [2], and, on the basis of the results of its laboratory and industrial tests [1], the PMM-2-type lifting mechanism.

Laboratory studies of the PMM-2 were carried out in order to determine the dependence of the power consumption and the efficiency of the mechanism on the weight of the drilling machines raised on the manipulator boom, with the aim of refining its actual parameters. Analysis of the results of these studies and comparison with the data from studies of the PMM-1 made it possible to draw conclusions about the effectiveness of the changes introduced into the design of the PMM-2 and to give recommendations for its further improvement.

The PMM-2 lifting mechanism (Fig. 1) is of explosion-proof design and consists of an electric motor and a reducer.

Screw 8 of the lifting mechanism, connected to the manipulator boom, receives translational motion from worm wheel 7 (Fig. 1, b), the hub of which has an internal thread. Motion to worm wheel 7 from electric motor 1 is transmitted through cylindrical gear wheels 2—3, bevel pair 4—5, and worm 6. In order that, when necessary, lifting or lowering of the drilling machine could be carried out manually, the free end of worm shaft 9 has a square section for a handle. The electric motor and the reducer of the lifting mechanism have a flanged connection. In creating the experimental batch of PMM-2 lifting mechanisms, all sliding bearings [1] were replaced by rolling bearings, and the worm pair by a two-stage gear reducer.

Technical characteristics of the PMM-2

Type of electric motor — ED-1M
Power of electric motor, kW — 1.0

Voltage, V — 127
Electric-motor rotational speed, rpm — 2800.
Worm-wheel rotational speed, rpm — 20.3.
Maximum weight of the mechanisms lifted together with the manipulator boom and swivel, kg — 500.
Lifting speed of the manipulator boom, mm/min — 2450.
Reduction-gear ratio — 138.
Weight, kg — 17.

Laboratory tests of the PMM-2 lifting mechanism were carried out on an MBM-2-type manipulator installed on a UMP-1 rock-loading machine. During the tests, the power consumed by the motor and the lifting speed were determined for drilling machines of various weights mounted on the manipulator boom.

Fig. 1. Lifting mechanism of the PMM-2 manipulator
a) general view; b) kinematic diagram: 1—motor; 2—3—4—5—gear reducer; 6—7—worm reducer; 8—lifting screw; 9—shaft for fastening the handle.

The results of the study of the PMM-2 lifting mechanism, in comparison with the test results for the PMM-1 drive, are given in Fig. 2.

A comparison of the results of the study of the PMM-2 mechanism and the PMM-1 drive shows that, when lifting machines of the same weight, the PMM-1 drive, while providing a lower lifting speed, consumes considerably greater power. Thus, with a load on the manipulator of 300 kg and a lifting speed of 1 m/min, the PMM-1 drive consumes 0.78–0.97 kW, whereas at the same load the PMM-2, at a speed of 2.75 m/min, consumes 0.5–0.7 kW.

The maximum efficiency of the PMM-2 lifting mechanism is 0.15–0.21 (depending on the position of the manipulator boom), while that of the PMM-1 drive together with the manipulator lifting mechanism is 0.04–0.05.

When lifting drilling machines with a total weight of 400–500 kg, the motor of the PMM-2 mechanism consumes 600–900 W, i.e., it is loaded to 60–90%. Taking into account the short duration of PMM-2 operation in the course of the face-drilling cycle, the power of the PMM-2 motor can be reduced to 0.3–0.4 kW, which in turn will make it possible to create a more compact and lighter lifting mechanism.

As already stated, the design of the lifting mechanism of the currently produced removable manipulators MBM-2 and MBM-5u provides for plain bearings. Therefore, in order to determine the effectiveness of replacing plain bearings with rolling bearings, comparative lifting tests were carried out on the manipulator for drilling machines of different weights using a manual drive.

The forces applied to the handle were measured with a dynamometer. The experiments were conducted at boom inclination angles of 50° and 110°.

Fig. 2. Dependence of power and efficiency on the load on the manipulator for the lifting mechanism PMM-2 (1) and PMM-1 (2).
⊙—boom inclination angle 50°; □—boom inclination angle 110°.

The results of the studies (Fig. 3) show that replacing sliding bearings with roller bearings reduces the force on the handle of the lifting mechanism by a factor of 4–5.

Thus, to raise a drilling machine weighing 400 kg, a force of 5–11 kg must be applied to a handle with a 25 cm lever arm when rolling bearings are used in the lifting mechanism (depending on the position of the manipulator boom), whereas when sliding bearings are used the force is 32–45 kg. The efficiency of these mechanisms is, respectively, 0.3–0.33 and 0.07–0.08.

Consequently, it is advisable to manufacture the lifting mechanisms of the MBM-2 and MBI-5u manipulators with rolling bearings. This will significantly ease the working conditions of the workers.

In July–August 1961, at mine No. 12 of the Kiselevskugol trust in Kuzbass, industrial tests were conducted on a long-travel electric drill with hydraulic feed of the ESDGP-1 type, used together with a PMM-2 lifting mechanism.

As a result of the tests it was established that the PMM-2 provides the required rates of raising and lowering the manipulator boom when a drill weighing 250 kg is mounted on it, significantly eases the working conditions of the workers, and is a reliable, serviceable design.

This provided grounds for recommending the PMM-2 for series production.

Conclusions

1. Mastering the series production of PMM-2 lifting mechanisms together with manipulators of the MBI-5u and MBM-2 types and introducing them into

in mines: (a) it will reduce the time required for auxiliary operations in raising and lowering drilling machines as compared with a manual drive; (b) it will make it possible to use high-capacity, long-stroke drilling machines weighing 250–300 kg in a set with removable manipulators; (c) it will reduce the labor input of operations for raising drilling machines.

Fig. 3. Dependence of the efficiency and the force on the handle of the lifting mechanism on the load on the manipulator for a mechanism on rolling bearings (1), and for a mechanism on sliding bearings (2), at boom inclination angles: ⊙ — 50°; □ — 110°.

1. Until the serial production of PMM-2 lifting mechanisms has been mastered, the lifting mechanisms of the MBM-2 and MBI-5u manipulators should be manufactured on rolling bearings.

2. It is advisable to reduce the power of the PMM-2 electric motor to 0.3–0.4 kW.

REFERENCES

1. O. D. Alimov, I. G. Basov, N. S. Kolodyazhnyi, “Electric drive of the manipulator lifting mechanism,” Izvestiya VUZov, Gornyi zhurnal, No. 12, 1960.

2. O. D. Alimov, I. G. Basov, V. F. Gorbunov, D. N. Machikov, Drilling Machines, Gosgortekhizdat, 1960.