Electropneumatic Impact Machines

P. M. Alabuzhev

One of the methods of processing materials—impact—has been used by humanity since remote antiquity. Prof. S. V. Poretsky, in the introduction to a course on forging [22], gives a brief history of forging from primitive man to the present day. In his extensive monograph on impact, Jules Marey [37] shows the use by people of the simplest impact tools: stone, bone, hoe, club, hammer for everyday work; the battering ram for breaking down enemy walls; various forms of pile drivers for driving piles; drop hammers for obtaining a large impact force; and a number of other impact machines. G. V. Rodionov gives a fairly detailed historical survey of the development of impact machines [24] and, in raising the question of their classification for discussion, writes: “The principal features selected for classification reflect the most essential technological and fundamental design characteristics of a given machine” [25, p. 72]. One cannot agree with this. Prof. E. A. Satel notes that “the development of modern machines is characterized by an ever-increasing tendency to replace mechanical connections between individual parts of a machine with other types of connections, first of all electrical, and also hydraulic and pneumatic” [26, p. 36].

At the present time, impact machines of the hammer and hand-hammer type, according to the nature of the working process and their dynamics, are divided into mechanical, steam-air, pneumatic, and electric. Mechanized impact tools [27], or more precisely machine-tools [24], were created mainly on the basis of the use of compressed-air energy. The high cost of pneumatic energy and the limited possibilities for its broad application directed the thought of inventors and designers toward the creation of electric impact machines, the field of application of which may be exceptionally broad and varied (work on metal, stone, concrete, wood).

The main principles in the development of electric impact machines are the solenoid principle and the electromechanical principle. According to the first principle, one part moves inside the solenoid—an iron striker—which receives reciprocating motion due to electromagnetic forces. There are prerequisites for creating a simple, compact, and economical impact machine. Work in this direction was carried out by Ya. S. Yampolsky [36], A. I. Moskvitin [21], K. N. Shmargunov [33], M. M. Tarashchansky [29], and G. I. Shturman [34]. There is still no industrial model of impact machines operating on the solenoid principle, since there are a number of difficulties that have not yet been overcome; these difficulties are: the complexity and high cost of auxiliary equipment, rapid burning of switch contacts, considerable heating of the hand hammer and a low overall efficiency of the machine, the complexity of the theory of electrodynamic processes and the difficulty of calculation. Electromechanical hand hammers are impact machines in which energy from a rotating electric motor through

...one or another transmission (linkage) system is converted into the energy of the striker, which performs reciprocating motion. Here we have a theoretically well-developed and practically implemented electric motor with a relatively high efficiency and with the possibility of regulating the number of blows of the striker.

It should be noted here that the transmission of energy from the electric motor to the striker is complex and varied. Soviet scientists and inventors K. N. Shmargunov [33], B. V. Sudnishnikov [28], P. S. Kucherov [17–18], and N. M. Batyuev [7, 8] worked on the development of this field.

“Electric jackhammers are of exceptionally great practical interest not only for the mining industry, but also for a whole range of other branches of the national economy. This determines the need for their comprehensive theoretical study, to which due attention has not been given in the literature,” writes Corresponding Member of the Academy of Sciences of the Ukrainian SSR P. S. Kucherov [18, p. 66].

From the point of view of energy utilization, electromechanical hammers are more economical than pneumatic ones. According to Academician A. M. Terpigorev, “the cost of electric energy per unit of extracted product is 3–4 times less than that of pneumatic energy” [30, p. 21]. But electromechanical hand hammers also have a number of significant shortcomings, namely: low impact work (on the order of $1\ \mathrm{kg/m}$), great weight (up to $15\ \mathrm{kg}$), considerable heating, and rapid wear of the steel springs. In addition, electric hammers cannot be used in mines not classified by gas category. Spring electric hammers of the KNSh type were proposed by K. N. Shmargunov and were mass-produced by TEMZ. “However, the severe operating conditions of the impact spring of KNSh electric hammers and their insufficient productivity in comparison with pneumatic hammers were the main reasons for the discontinuation of production of these electric hammers” [7, p. 11].

In the mining industry there is an acute need for a satisfactory design of an electric jackhammer and drill. Breakage and rapid wear of steel springs lead designers to attempts to use air as the elastic material. The “air spring” is an ideal (nonbreaking) “part.” The absence of “breakages” makes electropneumatic hammers more reliable in operation; but it should also be noted here that the efficiency of an air “spring” is lower than that of a steel spring. In addition, more precise machining of parts is necessary, which somewhat increases the cost of manufacturing the hammer. Finally, while carrying out the “air spring” itself presents no special difficulties, the calculation of an elastic nonlinear (air) linkage presents significant difficulties for the designer, and most often the problem is solved empirically.

In the present work we consider impact-action machines with a crank-and-connecting-rod transmission, as the most reliable and having a high efficiency (on the order of $\sim 95\%$). According to the nature of the elastic linkage between the piston and the striker, we consider:

1) impact-action machines with a one-sided air linkage, or hammers with an air-vacuum mechanism according to the classification of N. M. Batyuev [7, p. 12]. This includes designs of simple-action forging hammers by Arps, Massey, electropneumatic hammers by Berner, Grigoriev, and “Fein”;

2) impact-action machines with a two-sided air linkage, hammers with an air impact mechanism [7, p. 12]. This includes designs of double-action forging hammers of the Bêché type, electropneumatic hammers by Maleev and KNSh;

3) impact-action machines with a combined linkage between the striker and piston—an air-pneumatic impact mechanism [7, p. 14]. This includes...

include impact machines of the “Blake and Decker” type and the OMB type. In this work we consider not only “midget” machines, but also “giant” machines, since in a number of cases their basic scheme is one and the same, and the difference lies only in the purpose and in the structural design of the machine. Despite the specific character and special features, there exists to a certain degree a continuity and connection in the methods of investigation and calculation of these machines (at least as a first approximation). In addition, we wished to compare the values of certain quantities (for example, the work of a unit impact machine with an area of \(1\ \text{cm}^2\)).

Let us consider in somewhat greater detail the schemes and designs of electropneumatic impact machines.

Impact machines with one-sided air coupling between the piston and the striker

In the book by engineer V. A. Kel’dyshev [15, p. 111] a scheme is given for a pneumatic single-cylinder hammer of single action with air coupling (Arns hammer). As is seen from Fig. 1a, from the motor, through a crank-and-connecting-rod mechanism (1—2), piston 4, moving in a stationary cylinder, produces compression and rarefaction of the air in space 5, as a result of which the hammer tup, in the form of a second piston 3, is now pushed downward, now sucked upward. Cock 7 serves to regulate the force of the hammer blow on the forging (tool) 6. Through the cock, air enters from the atmosphere to compensate for leakage from the cylinder. From the scheme presented, the principle of operation of hammers of this group is clear.

In the literature on compressors [19], when selecting parameters, the following ratio is recommended from the standpoint of the best cylinder volume: \(s_{\text{p}} : D = 1\). In examining reference material on compressors, it turned out that the variation of the piston stroke with the cylinder diameter lies within the limits

\[ \frac{s_{\text{p}}}{D} = 0.5 \div 2.0 \quad [19,\ \text{p.}\ 396]. \]

Knowledge of the absolute value of the impact energy is still insufficient for judging the degree of efficiency of the given hammer. It is necessary to know at the expense of what the energy has been obtained: by increasing the mass of the tup, or by increasing its velocity. For different values of impact energy, a to some extent generalized indicator from the standpoint of impact efficiency is the specific weight of the striking part \(Q_b\), referred to a unit of stroke \(s\), that is,

\[ k_{\text{eff}} = \frac{Q_b}{s}. \]

A higher value of the indicator \(k_{\text{eff}}\) is more advantageous from the standpoint of the efficiency of the impact itself, since an increase in the speed of motion of the tup in a number of cases is associated with undesirable destruction and losses to deformation. This is especially the case, as I. I. Valutskii points out, when driving reinforced-concrete piles [10, p. 131].

The scheme of an electropneumatic single-action hammer, presented in Fig. 1b, preserves the principal features and the operating principle of the hammer described above. For the case when the diameter of piston 4 is equal to the diameter of striker 3, with a cylinder having double walls, we have the design of a ZERT hammer (“for the electrification of manual labor”), proposed by engineers E. A. Berner and N. I. Zhadaev. The hammer operates as follows. The electric motor, through a reducer by means of crank 1 and connecting rod 2, sets piston 4 into reciprocating motion. When the piston moves upward, a rarefaction is created between it and striker 3, and under the excess air pressure the striker also moves upward. During the downward stroke of the piston, compression of the air begins; the striker changes direc-

Subfigures: a), g), zh), b), d), z), v), e), i).

In subfigure i): electric motor; pump.

Conventional designations:

1 -- crank
2 -- connecting rod
3 -- striker
4 -- piston
5 -- air cushion
6 -- tool
7 -- compensating opening

... of motion and, at the end of its stroke, having acquired a certain velocity, delivers a blow to tool 6. To maintain stable operation at the moment of impact, the air in the hammer cylinder is brought into contact with atmospheric air through special compensating openings 7, which are a distinctive feature of the design. The hammer is switched off (goes to idle stroke) when pressure on the tool ceases. Despite the many designs of electric hammers of the ZERT type that have been produced, it has not yet been possible to solve the problem of constancy of the dynamic regime of their impact mechanism. During prolonged operation, heating of the air cushion (and of the crankcase air) does not allow the necessary rarefaction and filling to be created. Refinement of the design of electric hammers of this type continues, with the aim of enabling their stable operation on rocks possessing different physico-mechanical properties. Theoretical and experimental investigation of individual questions concerning the operation of electropneumatic hammers of this scheme has been presented in our works [1—5].

Designers select parameter values by feel, the order of which differs little from the following values:

\[ \begin{array}{lll} R=3\ \text{cm}, & Q_{\sigma}=0.8—1.0\ \text{kg}, & A_{\sigma}=2\ \text{kg m},\\ l_0=6\ \text{cm}, & q=40\ \text{g}/\text{cm}^2, & Z=900\ \text{blows/min},\\ D=5\ \text{cm}, & Q_m=14\ \text{kg}, & N=0.8\ \text{kW},\\ L=10\ \text{cm}, & & \end{array} \]

Scheme of an Air-Vacuum Hammer (OMG)

The Pneumatika plant has developed the design of an electric hammer with an air-vacuum impact mechanism, proposed by engineer L. Ya. Grigor’ev. This design is free from some shortcomings of hammers of the ZERT type, for example, instability of operation due to disruption of compensation. As can be seen from Fig. 1b, according to the OMG scheme it is possible to implement two types of designs: 1) when piston 4, connected with the connecting-rod-and-crank mechanism, is the hammer cylinder, inside which, owing to the available air connection 5, striker 3 moves, delivering blows to tool 6; 2) when striker 3 is the cylinder, connected through the air with piston 4 of the connecting-rod-and-crank mechanism. In the design of an OMG-type hammer, the air between the striker and the piston can be partially replaced by fresh air through special openings 7 in the piston and striker.

The electric OMG hammer manufactured by VUGI, according to the author’s data (L. Ya. Grigor’ev), has a single-blow work \(A_{\sigma}=4\ \text{kg m}\) and a blow frequency \(z=1250\ \text{blows/min}\) [2], p. 14, with a hammer weight \(Q_m=10.5\ \text{kg}\). The hammer passed tests and was tried out in the timber industry for cutting off branches (up to 12 cm in diameter) on felled trees. According to S. A. Bryukhov [9], the single-blow work is \(A_{\sigma}=2\ \text{kg m}\); the number of blows \(z=2000\); the light weight of the hammer \(Q_m=5.8\ \text{kg}\) was obtained by placing the electric motor separately from the hammer. The power of the electric motor is \(N=1\ \text{kW}\), at a current frequency of 200 hertz and a voltage of 220 volts.

The principle of placing the electric motor separately from the hammer and connecting it to the hammer by means of a flexible shaft was applied in designs by engineer N. I. Komarov, produced as models K—1, K—2, K—3 with a spring-kinematic impact mechanism, with a screw cocking device, \(A_{\text{eff}}=2.25\ \text{kg m}\), \(z=950\ \text{blows/min}\). Electric hammers of the “K” type proved to be unpromising designs owing to the inadequacy of the elastic link, unreliability in operation, and the great weight of the design as a whole (\(Q_m=15.5\ \text{kg}\)). Detailed...

A description of the operation of Komarov’s hammer is given in the work of M. M. Protod’yakonov [23].

Electropneumatic Impact Machines of Double Action with Pneumatic Coupling

The desire to use increased air pressures with a smaller cylinder (and ram) area led designers to the idea of using, in electropneumatic impact-action machines with an individual drive, the double-action principle employed in steam hammers. The group of hammers having an individual electric drive includes the well-known double-action hammers of the Beché type and a number of domestically produced models, data on which are given in the literature [13, 15, 35]. A diagram of a double-action hammer is shown in Fig. 1 g. Both cylinders, the compressor cylinder and the working cylinder, are connected by air channels. In the first cylinder moves piston 4, connected to a crank-and-connecting-rod mechanism driven through a system of transmissions from an electric motor. The air pressure created in the cylinder by the operation of piston 4 acts, through slide valves and connecting channels, on the lower and upper surfaces of the piston of the hammer ram 3. A design with two valves makes it possible to use short and straight channels, considerably reducing the influence of harmful space. The presence of valve air distribution makes it possible to lower the ram onto the forging at the required speed, i.e., makes it possible to obtain any impact force and to use a hammer of this type for the most varied work. To avoid damage to the cover of the working cylinder, an air cushion is provided. To reduce energy losses during idle running, the hammer is equipped with a special slide valve, upon the opening of which the hammer operates without load.

An air hammer can be installed wherever there is an electric-power supply, and it is always ready for operation. The direct drive from electric motors of hammers of this group is the most expedient (especially under partial loading on night shifts). Here there is no boiler plant and no steam-piping system. “Without touching upon economic calculations in comparing the operation of steam and air hammers, it should be said that the operating advantages of hammers using the energy of compressed air are of decisive importance” [14]. Where cheap electric power is available, air hammers are expedient for small and large forgings, and also for high-power perforators. The efficiency of the air double-action hammer of the most widespread models is approximately \(60\%\).

Electropneumatic Hammers of Double Action (with Two-Sided Excess Air Pressure on the Ram)

The desire to use increased air pressures with a smaller cylinder diameter led designers to the idea of electro-impact machines of double action, analogous to pneumatic double-action hammers with pneumatic coupling, but with one cylinder. A diagram of the design of a hammer of this type is shown in Fig. 1 d. G. I. Maleev [20] proposed the design and calculation of an electropneumatic hammer with two-sided pneumatic coupling (Fig. 1 e). This hammer, according to the author’s data, has single-blow work \(A_b = 3.0\ \text{kg/m}\) with piston diameter \(D = 3.2\ \text{cm}\) and lengths of the “air springs” \(l_1 = 3.6\ \text{cm}\) and \(l_2 = 5.8\ \text{cm}\). The entire calculation is performed under the assumption that the process of expansion and compression of the air is adiabatic and that the angular velocity of the motor is a constant quantity.

The author of a well-known design of a spring hammer, K. N. Shmargunov [33], in seeking a more reliable hammer design with a stronger blow, proposed a modified KNSh-3 hammer, in which air springs operate instead of the impact steel spring. Here the air cushion 5, during both strokes of the piston, works only in compression; as a result, according to the calculations of the designer, constancy of impact should occur during operation. The difference between this hammer and the hammer of G. N. Maleev lies in the structural design and, chiefly, in the way air compensation is accomplished.

Pulsator Diagram (Fein–Werner Hammer)

In Fein–Werner electric hammers [17], used mainly as riveting and chipping hammers, piston 1 is driven by an electric motor located separately from the hammer body. As can be seen from the diagram shown in Fig. 1zh, piston 4 creates vacuum and compression of air in the vacuum pump. The pulsation of the air, by means of a flexible hose connected to the hammer body, acts on striker 3, which performs reciprocating motion, delivering blows to tool 6. Air compensation is carried out through ports 7. The working stroke of the striker occurs under the action of the excess pressure of the compressed air, and the return stroke—by virtue of the excess atmospheric pressure resulting from the vacuum formed in the hammer cylinder. The disadvantages of hammers of this type are a comparatively low efficiency (on the order of 30%), the bulkiness of the system as a whole, and the possibility of using only a short air hose (about 2.5 m). Corresponding Member of the Academy of Sciences of the Ukrainian SSR P. S. Kucherov showed [17] that this design also offers possibilities for maneuverability and for a better choice of parameters.

Hammers with a Combined Elastic Coupling between the Piston and the Striker

In a number of foreign designs a mixed type of spring-pneumatic cushion is used. The literature [7, 21] gives a description of electric hammers with a spring-vacuum impact mechanism, manufactured by the Black and Decker company (USA), differing only in their power and weight. The acceleration of the striker, which, as in the OMG hammer, has the shape of a cup, during the working stroke occurs under the action of a precompressed spring fastened at one end to the moving piston, and under the action of vacuum. It should be said that here, too, the steel spring is placed under unfavorable operating conditions. In comparative tests of these hammers with hammers of Soviet designs, it was found that the overall efficiency of the Black and Decker hammers is very low [7]. Soviet engineer N. M. Batuev proposed an original design of a direct-drive electropneumatic hammer with a rigid coupling on the return stroke. The presence of a rigid coupling between the striker and the piston on the return stroke, thanks to an automatic coupling mechanism, guarantees the stability of the impact energy. We took a direct part in the study of the working process and in the selection of the parameters of hammers of this scheme [6]. Let us consider the design of the direct-drive electropneumatic hammer OM-5 (Fig. 13).

The problem of the electric chipping hammer is, in the final analysis, the problem of the weight of the design as a whole, the problem of the strength of parts at reduced weight. Existing non-chipping hammers for special purposes, for example KM-1, MPT-5, are not limited in weight and can without difficulty be designed in accordance with the customer’s requirements. The disadvant-

The disadvantages of the ZERT-type hammer as a chipping hammer, as already noted above, are the low impact energy at the striker and the variability of the cycle depending on operating conditions. In the KNSH hammers the impact energy at the striker is insufficient, and breakages of the steel springs often occur. To reduce the weight of the structure, high-speed electric motors have to be used. At a given motor power, the productivity of the hammer depends to a greater extent on the impact energy than on the impact frequency. The use of the usual method of reduction—for example, by using a gear transmission to reduce the impact frequency relative to the number of revolutions of the electric-motor rotor—leads to an increase in its dimensions, that is, to an increase in the weight of the hammer. N. M. Batuev proposed reduction without the use of ordinary gear transmissions, the so-called principle of skipping impacts. The constructive implementation of the proposed idea took shape in the gearless hammers “MEI,” MB-1, MB-2, and MB-3. In the first two machines there was a rigid connection between piston 4 and striker 3 during the working and return strokes. In the latter case this connection was effected by means of a special coupling part called a “grip.” The latter is a massive body eccentrically mounted on an axle in the piston. The operation of the grip is based on the action of inertial forces caused by the motion of the piston of the crank-and-connecting-rod mechanism. The specified skipping of impacts was ensured by the corresponding kinematic adjustment of the coupling. A substantial disadvantage of the first designs was the presence of internal impacts; and since the springs had not justified themselves in the designs of their predecessors, in order to eliminate internal impacts between the piston and the striker, air is used as the elastic medium. In the MB-2 and MB-3 designs a new, more perfect working process of the machine was implemented; moreover, the possibility of using dynamic skipping of impacts was demonstrated. For the fastest possible damping of the striker, and also in order to pick up the striker from the extreme left position, it is possible either to precompress the air between the striker and the piston or to insert a comparatively weak damping spring between the striker and the mechanism housing. After the working impact and damping of the striker, its return stroke is carried out with the aid of an inertial grip. Separation of the striker from the piston will occur after relative motion has arisen between them. In this case the rigid connection between them is replaced by an elastic (air) connection, which exists until the very moment of the working impact.

In light and high-speed electric motors, under the influence of the load during one working stroke of the striker, at proper productivity determined by the operation of the impact unit, a considerable drop in angular velocity occurs. In the case of an inelastic impact and in the absence of a skipping mechanism, the whole cycle is repeated, but with an even lower average angular velocity; and after several revolutions the working process would be disrupted because of an excessively large drop in the angular velocity of the motor. If, however, one proceeds only from the normal operation of a light and high-speed electric motor, a large number of low-productivity impacts on the striker will be obtained. In reality there is a rebound of the striker, as a result of which phenomena of internal impact or of “increased” air pressure between the striker and the piston are possible. Consequently, for stable operation of this mechanism, time is required for damping the striker and for the motor and crank-and-connecting-rod mechanism to replenish the expended energy. The reduction in the number of working strokes in comparison with the number of revolutions of the motor is carried out by skipping the coupling of the piston with the striker, which can be effected kinematically and dynamically.

Comparative tests of hammers of various designs were carried out by the author of the OMB hammer design [7], and in his opinion gearless hammers are more progressive than foreign-

designs, and have broad possibilities for further improvement. It should be noted that this design is promising as a pick-type electric hammer and a light electric rock drill¹.

Coal Plane with an Active Edge

The effectiveness of impact is used not only in hand-operated mechanized tools for cutting, but also in heavy mechanization—in mining combines and coal planes. This question has been covered in sufficient detail in the works of Academician A. M. Terpigorev [30] and in the collection of papers of VUGI [11]. Works [31, 32] discuss questions of the effectiveness of using coal planes.

The coal plane (U.S.) has as its prototype the ordinary plow, the theory of whose operation was given as early as by Academician V. P. Goryachkin [12]. A coal plane with a simple cutting edge gives good productivity on soft coals. It is moved by winches at a speed of 5 m/min with a cutting depth of 30 cm, and with a tractive effort of 10–20 tons. On hard coals it is necessary to increase the tractive effort to \(\simeq 30\) tons, which to a considerable extent limits the possibilities of applying the coal plane. In order to reduce the magnitude of the tractive effort, it is necessary to replace the cutting forces with chipping forces, i.e., to use an active plane which not only must plane the coal while moving along the longwall, but also exert an impact action on it (in this case tractive efforts of the order of 7 tons arise).

Coal cutting can be carried out by using pneumatic and electric pick hammers. In connection with the general tendency toward electrification of the national economy and the convenience of using electric energy, it is more expedient to use electric hammers in gas-safe mines. Here there is the possibility of convenient and direct use of electric energy (without additional expenditures on a compressor, pipelines, etc.). In addition, the designer, not being limited by the weight and overall dimensions of the machine, has the possibility of easily providing the required impact energy; all the more so because here heating of the hammer is not of such decisive significance as in hand work, and can be considerably reduced by the use of cooling.

Figure 1u shows the breaking part of the UDS-1 coal plane. Here “the active part of the impact plane has two blocks with four powerful electropneumatic pick hammers and with 4 chipping massive knives, located in a vertical plane on both sides of the plane” [16, p. 46]. The electropneumatic hammers are taken of the air-vacuum type OMG.

Conclusions

1. The desire to create a productive, economical, and reliable electropneumatic hammer in operation compels one, to a certain extent, to pay attention to the operation of air hammers with individual electric drive and to compare the values of the indicators of certain characteristic quantities.

2. As can be seen from the table compiled by us on the basis of literature sources, the ratio of the weight of the moving parts to the weight of the stationary parts, \(k_n\), in light electropneumatic hammers is somewhat higher than in heavy electropneumatic hammers.

1. The weight of the moving parts per unit area of the cylinder, or per unit of their stroke \(s_b\), is considerably greater in stationary hammers than in hand hammers.

2. In light impact machines, as compared with heavy ones, there is a relatively large number of blows per minute; greater energy saturation per unit weight of the striker; higher effective power of a unit hammer with a conventional cylinder area of \(1\ \mathrm{cm}^2\); considerably higher specific power, equal to the ratio of the energy capacity of the machine to its metal consumption, \(\mathrm{W/kg}\); and the role of the air coupling is increased, the index of whose operation is the ratio of the impact energy \(A_b\) to the product of the striker weight \(Q_b\) and the length of its stroke \(s_b\).

3. The overall efficiency of stationary impact machines is considerably higher than that of hand electropneumatic hammers. Evidently, along with a high concentration of energy, there is also greater dissipation of energy during its transmission and transformation through a series of links of the machine.

At present, electropneumatic impact machines, in terms of their productivity and reliability in operation, are still not competitors of pneumatic hammers. However, questions of the development of the coal and, chiefly, the mining-ore industry on the basis of the application

Table of performance indicators of electropneumatic hammers and hammer tools

of electrical energy set the task of an in-depth study of the operation of these machines and of identifying the principal connections and regularities, as well as the task

development and improvement of methods for calculating and selecting optimal parameters, with the ultimate aim of creating and introducing into industry an economical, productive, and reliable electric impact machine.

LITERATURE

1. Alabuzhev P. M. Investigation of the working process of an electric breaking hammer with an elastic (air) connection. Izvestiya TPI, vol. 61, no. 1, 1947.

2. Alabuzhev P. M., Yudin I. P. Experimental investigation of the working process of an electropneumatic hammer. Trudy GGI ZSФAN, vol. 8, Novosibirsk, 1950.

3. Alabuzhev P. M. Application of the theory of similarity and dimensional analysis to the investigation (modeling) of impact machines. Izvestiya TPI, vol. 73, 1952.

4. Alabuzhev P. M., Medlyna E. K., Nevstruev E. N. On a method for indicating indicator diagrams of electropneumatic impact machines. Izvestiya TPI, vol. 76, 1953.

5. Alabuzhev P. M. Some results of an experimental investigation of electric impact machines. Izvestiya TPI, vol. 78, 1954.

6. Alabuzhev P. M. Dynamics and working process of a gearless hammer with an elastic connection during the return stroke. Izvestiya TPI, vol. 78, 1954.

7. Batuev N. M. Electric hammers, VNIIstroydormash. Investigation of Machines and Mechanisms for Construction and Road Works, 1. Mashgiz, 1950.

8. Batuev N. M. The energy of electric hammers and ways of increasing their productivity. Investigation of Vibrators and Electric Hammers, VI, VNIIstroydormash. Mashgiz, 1951.

9. Bryukhov S. A. Experimental models of new machines and mechanisms for timber harvesting. Journal Mechanization of Labor-Intensive and Heavy Work, no. 11, 1950.

10. Valutskii I. I. Pile drivers and pile hammers. Mashgiz, 1950.

11. Coal extraction by cutter-planers, Ministry of Coal Industry. Bureau of Technical Information, issue 24, Ugletekhizdat. Moscow, 1949.

12. Goryachkin V. P. Theory of the plow. Promizdat, Moscow, 1927.

13. Zimin A. I. Calculation and design of forging machines, part 1. Steam-air hammers. Mashgiz, 1940.

14. Karabin A. I. The energy performance of steam and air hammers in forges. Ukrmashgiz, Moscow—Kharkov, 1939.

15. Keldyushev V. A. Pneumatics. ONTI, Moscow, 1938.

16. Koval P. V. Coal cutter-planers. In: Scientific Works of Students. Moscow Mining Institute, 1952.

17. Kucherov P. S. Investigation of the parameters of an electropneumatic hammer of the “Fayn” type. Proceedings of the Institute of Mining Mechanics, Academy of Sciences of the USSR, issue V, Kiev, 1947.

18. Kucherov P. S. Theoretical investigation and a method for calculating the parameters of electromechanical breaking hammers with a crank-and-connecting-rod drive. Proceedings of the Institute of Mining Mechanics, Academy of Sciences of the Ukrainian SSR, issue V, 1947.

19. Lisichkin V. E. and Gorshkov D. M. Compressor machines. Gossenergoizdat, Moscow—Leningrad, 1948.

20. Maleev G. I. Electropneumatic hammer. Journal Mining Machinery Construction, no. 4–5, 1939.

21. Moskvitin A. I. Electric reciprocating machines. Academy of Sciences of the USSR, Moscow, 1950.

22. Poretskii S. V. Course in forging practice, vol. II, Machines of forging production. ONTI, Moscow—Leningrad, 1935.

23. Protodyakonov M. M. Electric breaking hammer of the K-2 system of N. I. Komarev. MUP, Bureau of Technical Conferences, Moscow, 1949.

24. Rodionov G. V. Impact machines. In: Impact Machines, ZSФAN USSR, Novosibirsk, 1953.

25. Rodionov G. V. On the classification of impact machines. In: Impact Machines, ZSФAN USSR, 1953.

26. Satel E. A. Technical progress and the Higher School. Bulletin of the Higher School, no. 11, 1952.

27. Sudakevich D. N., Bernadskii G. I. Handbook of mechanized hand tools. Mashgiz, 1954.

28. Sudyushnikov B. V. Some questions in the theory of impact machines. Published by ZSФAN USSR, Novosibirsk, 1949.

29. Tarashchanskii M. M. Experimental investigation of a magnetofugal generator. In: Collected Works of KhETI, issue 7. Kharkov, 1948.

30. Terpigorev A. M., Demidov P. N., Protodyakonov M. M. Mining machines for excavating bedded minerals. Moscow, 1949.

1. Topchiev A. V. Creation of new working members for coal-mining machines and tasks for scientific research in this field. Izvestiya AN SSSR, Department of Technical Sciences, No. 1, 1953.

2. Turich A. L. and Balinov I. M. The US-4 coal plow in the mines of the Donbass. Journal Mechanization of Labor-Intensive and Heavy Work, No. 5, 1949.

3. Shmargunov K. N. Electric Hammers. Mashgiz, 1950.

4. Shturman G. I. A magnetofugal synchronous generator in the drive of impact mechanisms. Collection of KhETI, issue 7, 1943.

5. Encyclopedic Reference Book “Mechanical Engineering”, vol. 8. Mashgiz, 1949.

6. Yampolsky Ya. S. Magnetofugal impact machines. Electricity, No. 7, 1925.

7. Jules Marey, Le Marteau. Le choc. Le Marteau pneumatique. Études Expérimentales de Technologie Industrielle, 64e mémoire, Paris.

1. At present, work is being carried out to master this design as a pile-driving hammer (with \(A_{\sigma} = 100\ \text{kg·m}\)) for road construction. ↩