V. I. BABUROV, V. F. GORBUNOV

ON THE METHODOLOGY FOR CALCULATING THE MAIN PARAMETERS OF CHIPPING AND RIVETING HAMMERS

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

Studies of the working processes and designs of pneumatic drilling \[2, 4\], breaker \[5, 6\], and chipping-and-riveting hammers \[3\] have made it possible to compile a number of basic relationships for selecting and calculating their parameters.

This article presents a nomogram reflecting the relationships between the main parameters of chipping-and-riveting hammers, the principle of its construction, and the rules for working with it.

Use of the nomogram will help designers quickly select the main parameters of chipping-and-riveting hammers as a function of their design dimensions. This is especially important for designers at plants that manufacture hammers. Often, when manufacturing hammers of their own designs for chipping and riveting, production workers do not know even their approximate parameters.

It is proposed that calculation of the parameters be based on the known relationships \[1, 2, 6\]

\[ A = k_1 p F S_{\text{con}}, \ \text{kgf}\cdot\text{m} \tag{1} \]

\[ n = \frac{k_2 \cdot 60}{1+\gamma}\sqrt{\frac{pF}{mS_{\text{con}}}}, \ \text{blows/min}, \tag{2} \]

\[ N = \frac{An}{60 \cdot 75}, \ \text{h.p.}, \tag{3} \]

where \(k_1\) is the coefficient of energy losses, taking into account the degree of filling of the cylinder with compressed air and mechanical losses under optimum operating conditions of the hammers. For chipping-and-riveting hammers \(k_1 = 0.5\text{–}0.55\);

\(p\) is the air pressure in the network, atm;

\(F\) is the cross-sectional area of the hammer barrel cavity, cm\(^2\);

\(S_{\text{con}}\) is the design stroke of the striker, representing the difference between the length of the cavity (minus the length of the tool shank) and the length of the striker, m;

\(k_2\) is a coefficient accounting for the reduction in blow frequency due to mechanical losses and the degree of filling of the cavities with compressed air. For chipping-and-riveting hammers \(k_2 = 0.75\);

\(\gamma\) is the ratio of the time of the return and forward strokes of the striker, \(\gamma = 1.6\);

\[ m=\frac{Q}{g} \]
— mass of the striker, kg·sec²/m;

\(A\) — impact energy, kgf·m;

\(n\) — frequency of blows per minute;

\(N\) — impact power, hp.

Figure 1 presents a nomogram compiled on the basis of formulas (1–3). The nomogram has four quadrants. The first quadrant shows the graphical dependence of the impact energy on the length of the design stroke of the striker at various values of the useful cross-sectional area of the hammer cylinder. This dependence is constructed on the basis of formula (1). The loss coefficient is taken as \(k_1 = 0.52\).

Fig. 1. Nomogram for calculating the main parameters of pneumatic chipping-and-riveting hammers.

For similar hammers with the same barrel (striker) diameter, the values \(k_1\), \(p\), and \(F\) will be constant. Consequently, the impact energy as a function of the length of the design stroke of the tup will vary-

according to a linear law. This proposition is also confirmed by experiments.

The frequency of blows per minute is determined from dependencies II and III of the fourth nomogram (Fig. 1), constructed on the basis of formula (2). In this case an intermediate quantity was introduced

\[ \alpha = \frac{k_2 \cdot 60}{1+\gamma}\sqrt{\frac{pF}{S_{\mathrm{end}}}} . \tag{4} \]

For different values of the cross-sectional area of the cavity of the hammer barrel, we construct the dependencies between the constructive stroke of the striker and the intermediate quantity \(\alpha\) (quadrant II, Fig. 1), and then find the frequency of blows per minute as a function of \(\alpha\) for different values of the weight (mass) of the striker \(m\) (quadrant III, Fig. 1).

In the fourth quadrant, the dependencies of the frequency and energy of blows are constructed according to formula (3).

The nomogram is constructed for an air pressure in the network equal to \(5\) atm.

To calculate the parameters of pneumatic chipping-and-riveting hammers, it is necessary to know the length of the constructive stroke, the weight of the striker, and the cross-sectional area of the cylinder. In this case the calculation begins from the \(+Y\) axis (Fig. 1), where the stroke length is laid off. The intersection of a horizontal line with the ray representing the striker cross-sectional area in the first quadrant gives point \(A\), whose projection onto the \(+X\) axis cuts off on the axis the value of the hammer blow energy.

In the second quadrant, from the known stroke length and striker area, the intermediate quantity \(\alpha\), entering into the formula for the number of hammer blows (2), is determined on the \(-X\) axis. Continuing the vertical line from point \(B\) into the third quadrant until it intersects the ray representing the weight of the striker (piston), point \(V\) is obtained, and by projecting it onto the \(-Y\) axis, the hammer blow frequency is found.

In the fourth quadrant, the intersection of the perpendiculars to the \(-Y\) and \(+X\) axes from the found values \(n\) and \(A\) gives point \(G\), denoting the value of the hammer impact power.

To determine the dimensions of the hammers being designed, it is necessary to specify certain desired characteristics. For example, one may specify a definite value of the blow energy and the cross-sectional area of the striker and, using the nomogram, find the other parameters of the future hammer. From the specified parameters of blow energy and blow frequency, it is possible to determine several design variants of the impact unit and choose the best of them.

The calculation of the main dimensions of pneumatic drilling hammers by nomograms with logarithmic scales [1] can also be applied to the calculation of riveting hammers, but the coefficients must first be corrected.

Table 1 gives the technical characteristics of chipping and riveting hammers and their parameters found from the nomograms. Deviations in the parameter values range from 0% to 20%. As can be seen from Table 1, the difference between the parameter values found from the nomogram and those found experimentally is somewhat smaller than the deviations of the calculated data from the factory characteristics. Attention should be paid to the fact that there are also data from factory laboratory tests, as a result of which, for riveting hammers, for example, the following parameter values were obtained:

1) KE-32  \(A = 4.24\ \mathrm{kgm},\)  \(n = 920\ \text{blows/min};\)

2) KE-28  \(A = 3.3\ \mathrm{kgm},\)  \(n = 1075\ \text{blows/min};\)

3) KE-16  \(A = 1.3\ \mathrm{kgm},\)  \(n = 1950\ \text{blows/min}.\)

Table 1

*) In the numerator—the deviation of the values of the parameters found from the nomogram from the factory data; in the denominator—the deviation of the same parameters from the experimental data.

From the examples presented it is evident that the average deviations of the parameters found by means of the proposed nomogram do not, in general, exceed 10%, and the calculation results lie within the range of values obtained by various experimental methods.

REFERENCES

1. O. D. Alimov, A. A. Alimova, V. F. Gorbunov. On a methodology for calculating the basic parameters of pneumatic drilling hammers. Interuniversity collection of papers, Mechanisms and machines of impact, rotary, and rotary-impact action. Novosibirsk, 1963.

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

3. V. I. Baburov, V. F. Gorbunov. Investigation of the internal processes and parameters of chipping and riveting hammers. Proceedings of TPI, vol. 123, Publishing House of Tomsk University, 1963.

4. V. F. Gorbunov. Experimental investigations of the working process of pneumatic drilling hammers. Candidate dissertation, Tomsk, 1958.

5. B. V. Sudnishnikov. Certain relationships arising from the features of indicator diagrams of pneumatic hammers. Collection Impact-Action Machines, Novosibirsk, 1953.

6. B. V. Sudnishnikov and L. I. Semenov. Calculation of a pneumatic breaker hammer. Collection Impact-Action Machines, Novosibirsk, 1953.