US2906898A - Electric reciprocating hammer - Google Patents

Description

Sept. 29, 1959 E. J. Mxsslr-:N

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A IN1/EN TOR. fm1/440 J. ,wss/fn' MM United States Patent ELECTRIC RECIPROCATING HAMlVlER Edward J. Mission, Indiana, Pa., assigner to Syntron Company, Homer City, Pa., a corporation of Delaware Application March 29, 1954, Serial No. '419,551

4 Claims. (Cl. B10-30) This invention relates generally to electric hammers and more particularly to improvements in the construction and the operating parts of electric hammers with free reciprocating pistons.

The electric hammer comprising this invention is large, weighing substantially seven hundred pounds. It operates on intermittent current pulsations which energize alternate coils to reciprocate an electromagnetic piston through a stroke of approximately one inch at a frequency of 1800 cycles per minute to deliver a striking force of thirty thousand pounds'.

This improved electric hammer may be used for mining coal by providing a bit, the at or blunt face of which is transverse to the bit axis and penetrates the coal by powdering the area ahead of it and driving this powdered coal in ahead of the bit, causing the coal to fracture, expand and break out from the mine face. By first undercutting the coal it is more readily broken out in the face immediately above the undercut.

The structure of this reciprocating electric hammer has been improved to make it explosion-proof. The piston is provided with oppositely extending stems which are journaled in long oil-sealed bearings that seal the piston chamber. This tool or bit is similarly sealed. These sealing bearings are mounted under spring pressure.

Another object is the reaction coil springs for the piston and the tool which are provided with a variable clearance that changes its natural period of operation to one that is different from the period of the operating magnetic piston.

The ratio of the diameters of both stems and the body of the integral magnetic piston are selected within a range that does not interfere with the operation and transmission of power. This piston provides for the transfer of atmosphere to opposite ends of the piston chambers.

Increased performance is obtained from this improved hammer by providing wire of square cross section. This not only permits an increase in the circular mills, but it also provides a mode of locking and sealing the coils on the barrel to completely enclose the electromagnetic piston chamber.

Another object is the provision of an improved outer casing which encloses and seals the coils, providing an explosion-proof housing.

Another object is the provision of an oiling system for a completely sealed-in electric hammer wherein the oil functions in maintaining the seal of the piston chamber.

Another object is the provision of an improved magnet coupling plate between the spaced coils of the electric hammer.

Other objects and advantages of this invention appear hereinafter in the following description and claims.

The accompanying drawing shows, for the purpose of exemplication, Without limiting the invention or claims thereto, certain practical embodiments of the invention wherein:

Fig. l is a view in horizontal section of the electric hammer comprising this invention.

Fig. 2 is a view in side elevation of the end casting.

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Fig. 3 is a top plan view of the end casting as taken along the line III-III of Fig. 2.

Referring to the drawing, the electric hammer is constructed on the stainless steel barrel 1 which has a cylindrical bore 2 that forms the magnetic piston chamber 3. The exterior of the barrel 1 has hexagonal faces that are provided with Windows 4 to receive the pole ends 5 of the iaminated core 6. The ends 7 and 8 of the barrel 1 are cylindrical externally as well as internally. l

Each of the six faces on the barrel 1 is provided with three sets of laminations, two L-shaped 10 and one straight dual section 11. The straight dual sections 11 are connected with a heavy center plate 12 which stops short of the barrel as shown at 13 and does not extend to the outer surface as indicated in Fig. l. Each L-shaped lamination 10 is connected to one of the dual sections 11 by a straight outer lamination member 14 to close the outer magnetic circuit over the coils 15 and 16. This avoids excessive magnetic losses in the outer steel cylindrical casing 17 Each of the six sets of laminations 10 and 11 are welded along only one side and at their ends to the exterior of the barrel, as indicated at 18. This breaks the path of the eddy currents by having the laminations welded only on one side and at the ends and is an important object of this invention.

Each circular set of the laminations 10 and 11 has high temperature insulating cord 20 wound between the insulating ends 21 to lill up the interlocking notches in the laininations at the magnetic gap 22 and thus provide a base for the coil. Each coil is wound of square wire which aids in locking the coil in place where wire of circular cross section may shift. Again a number of circular mils may be obtained for a given length and number or" turns of wire. The coil leads 23 are brought out between the coils and are provided with expansion loops 24, to avoid destruction of the coil due to expansion and contraction due to heat, as these coils are not ventilated but are completely enclosed.

The end castings 25 and 26 are mounted on the cylindrical ends 7 and 8 of the barrel 1 which seat on shoulders and prevent these end castings from engaging the coil laminations. These end castings are made of magnesium bronze and each is provided with a cylindrical seat 27 of material width which terminates in the sharp groove 28. The ends of the casing 17 have a. beveled sharp edge that lits into the sharp grooves 28 and their inner surfaces are machined to tightly iit on the seats 27 to provide a gastight seal of the coil chamber 30 within the case 17.

Tie rods 31 are pinned to corners in the front end casting 25 and extend over the casing 17 to similar ears 32 of the rear end casting 26 Where they are held by the nuts 33. Thus the tie rods 31 cause the ends of the casing 17 to bite into the V-shaped grooves 28 of the end castings and hold the latter castings in assembled relation with the barrel 1 and the outer casing 17.

The cylindrical bore` of the barrel 1 has the shoulders 34 and 3S for receiving the complemental shoulders on the bearings 36 and 37 which are accurately formed and positioned to provide aligned bores in which to receive the stems 38 of the free electromagnetic piston 40. The piston 40 must be of magnetic material. It must be integral, made of one piece, and it must be strong. It is therefore constructed as a forging. The diameter of each stem of the hammer shown is 1.246 inches, whereas the diameter of the body of the piston 40 is 3.130. Thus the ratio of these diameters is l to 2.5 and they are connected with a fillet having approximately a half inch radius. If the diameter of the stems is increased to over a ratio of l to 4, then the stems rob the magnetic force from the body of the piston and decrease its efficiency as a reciprocating member. Thus any ratio of l to 4 or less provides good operating characteristics.' However any stem and piston ratio materially greater than the above mechanically weakens the stems and thus the best average is 1 to 2.5 as shown.

The ends of the piston stems 38 have the contact surfaces capped with Stellite by welding the same thereto, as indicated at 41.

The body of the piston 40 is fluted longitudinally by eight slots 42 which are cut approximately one quarter of an inch deep. These slots serve two purposes of equal importance. One, they reduce the eddy currents by interrupting their paths of flow. Secondly, they provide channels through which the atmosphere in the piston chamber 3 may be quickly forced from one end of the chamber to the other and avoid the generation of excessive pressure and rarefication zones.

'Ihe bearings 36 and 37 provide for only a few thousandths of an inch for sliding clearance between the stems and bores of these bearings. Each bearing has an annular external groove 43 which has an annular Wick 44 and radial wicks 45 which conducts the oil to the surface of the stems. These oil reservoirs 43 are lubricated through passages that extend from the bearings 36 and 37 into the end castings 25 and 26 where they extend to the surface and are provided with ball check oil seal fittings.

The front end casting 25 has the tool bushing assembly mounted in its inner end and which comprises the housing 46 which is bored from its inner end to receive the tool bushing 47 that slidably supports the tool shank 48 that is lubricated from the passage 49.

The shoulder 50 of the tool is approximately threefourths of an inch thick and the fillets to the tool shank 48 and the tool bits 51 are three-eighths of an inch.

The shank 48 is ground to one and one-half inches,

whereas the tool 51 is ground to 1.875 inches for a distance of thirteen inches from the shoulder edge. This is larger than the shank and extends to the end of the nose casting 52. The tool is thirty inches over-all, the shank is six inches, thus the balance of the bit is approximately ten and one-quarter of an inch long and this length tapers from 1.875 inches to 1.5 inches and the end of the bit is a flat transverse face 53. These dimensions are important owing to the manner that the tool is supported. i

The end casting 25 extends forwardly and has an internal shoulder 54 to receive the inner end of the nose casting which is bolted thereto by the bolts 55 which also bolt on the roof trimming blade 56 which has a sharpened tooth' to chip the roof smooth as the whole hammer is reciprocated. rThe nose casting 52 is bored to receive the bearing 57 which rests on the shoulder 53, leaving space for the circular ring packing 6G. Another ring packing 61 is mounted in a groove adjacent the other end of the bearing 57. Thus the bearings 47 and 57 suspend the tool and one is mounted in the housing 46 and the other in the nose casting 52, both of which are aligned in coaxial bores in the end casting 25. Lubrieating passageway `62 .is provided to lubricate the tool bit 51 through the nose casting between the ring seals.

A lock sleeve 63 is provided in the bore of the end casting 2S and abuts the nose casting at one end but is spaced from the housing 46 at its other end. This space provides room for the continuous circular spring washer 64.

The interior of the nose casting has a seat 65 to receive one end of the coil spring 66, the other end of which engages the spring seat 67. This spring seat 67 has clearance with the tool bit l and the bore of the lock sleeve 63.

A `bell opening is provided in the bores ofthe housing 46 and the spring seat 67 to receive the lleted sides of the tool shoulder 50 which engages both of these parts, the rst as a rebound from the coal o r due to the spring and secondly at the end of the power stroke when the piston stem 38 engages the shank 48 of the tool.

The end casting 26 has the rear spring support 70 bolted thereto by the bolts 71. The support 70 is open and has an end cap 72 which seats the outer end of the spring 73 and is secured by the bolts 68. The springs 66 and 73 are the same in size and shape. The other end of the spring 73 engages the solid core stop 74 which has a projection 75 that reciprocates in the bore of the core stop seat 76 which is retained by the plate 77 bolted between the end casting 26 and the spring support casting 70. Adequate lubrication is provided by the passage 78 to the exterior.

The springs 66 and 73 also have another novel characteristic. The outer adjacent turns of these spring coils engage each other and each successive turn is spaced progressively wider and wider until the greatest spacing is between adjacent turns at the inner ends of these springs. This progressive tapering of the spacing between the coils of the spring provides a variable period of vibration. When the smaller gaps at the outer ends of the spring are closed the effective length of the spring changes and thus the natural period of vibration changes progressively. Since the springs are helical this variation of spacing is uniformly progressive. Thus the period of the piston cannot equal the period of the springs which results in the smooth constant following by the piston of the current impulses in traveling its stroke which is approximately one inch.

As shown in Figs. 2 and 3 the terminals of the coils 15 and 16 pass between the laminations to the junction box 80 which is shown open in Fig. 3 but closed with the cap 81 in Fig. 2. Terminals 82 and S4 come from coil 15 and terminals 83 and 85 come from coil 16. Terminals 84 and 85 continue independently through the triconductor cable 86. Terminals 82 and 83 are connected together and to conductor 87. This cable passes through the packing 88 compressed by the gland or follower 89. The opposite end of the follower has a threaded end 90 which is for receiving the ends of a flexible hose 94 that acts as a shield for the cable 86. The hose 94 is held by the clamp 92. The opposite side of the junction box 80 has a cap 93 for the purpose of bringing the cable 86 out that side to produce right and left hand hammers.

I claim:

l. An explosion proof electromagnetic reciprocating hammer comprising a cylinder of nonmagnetic material, a nose casting at one end and a head casting at the other end of said cylinder, a magnetic core reciprocally mounted in said cylinder and made from a single piece of magnetizable material having a body portion with a stem extending from each end to strike a tool shank carried by said nose casting and a core stop carried by said head casting, an electromagnetic eld means mounted on the cylinder between said castings to reciprocate said magnetic core when energized to strike the tool shank and core stop, a casing enclosing said iield means and sealing with said castings, a sleeve bearing sealing each end of said cylinder and for slidably receiving each stem to support said core, annular oil groove means in said bearings, lubricating passages to said 'groove means and extending exteriorly of said castings to 'receive lubricant for same stems in said bearings and to seal the same against flame due to failure of said electromagnetic ield, and oil check means in said passages adjacent the outer end thereof.

2. The structure of claim l characterized inthat said groove means includes a plurality of oil grooves in each bearing served by one passage, wicking in said passage to carry the oil to said grooves and seal said passage against transmission of flame.

3.Y The structure of claim l characterized in that said tool shank and core stop are positioned to be engaged by .their respective stems to stop the movement of said core before the body thereof strikes said bearings.

4. An explosion proof electromagnetic reciprocating hammer comprising a barrel, a magnetic core means mounted around the exterior of said barrel, eld means Wound on and enclosed by said core means, a piston made of a single piece of magnetic material and having a body with a stem at each end and reciprocable in said barrel when said eld means is energized by alternate pulsating currents, a casting attached to each end of said barrel, a cover enclosing said core and field means and sealing with said castings, a bearing mounted in each end of said barrel to slidably receive said stems to carry said piston, an enclosed and sealed resilient stop carried by one casting to be engaged by a stem, a bushing carried by the other casting, a tool slidable in said bushing and engageable by said other stem, lubricating passages to said bearings and bushings, and lubricant check means in said passages to retain the lubrication in said bearings and bushings to seal the same.

References Cited in the le of this patent UNITED STATES PATENTS Van Depoele Sept. 1, 1891 Dumas Apr. 11, 1905 Paulero Dec. 9, 1924 Weyandt Aug. 14, 1928 Dominguez Aug, 6, 1929 Weyandt Apr. 8, 1930 Nandillon et al. Aug. 18, 1931 Gartin Oct. 25, 1932 Herrick Feb. 23, 1937 Wieseman May 21, 1940 Craig et a1. May 9, 1944 Weyandt et al. Apr. 6, 1948 Ellmann Jan. 18, 1949 FOREIGN PATENTS Italy Mar. 29, 1926

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