US patent 5 558 285 describes an apparatus of the above mentioned kind, where the coupling is hydraulic. At its upper end, the hammer head is provided with an upward tapering coupling part interacting with the hydraulic connecting coupling which is operated by means of a hydraulic hose, which via a tension mechanism with separate hose drums runs in parallel with the lifting wire.

This prior art apparatus is, however, connected with several drawbacks, one of which is the construction of the hammer head as well as the hydraulic connecting coupling and the associated tension system for the hydraulic hose. Features making the appara- tus too sensitive to disturbances and too slow to work with.

This apparatus utilises a hammer head which, besides a rounded lower end, has ap- proximately uniform cross-section over all its length, which is particularly disadvanta- geous because the lower end of the hammer head cannot avoid being deformed at the impact with the item to be crushed, by forming so-called beard and a thickening of the outer diameter to be removed from time to time, a cumbersome and time-consuming work.

The invention has the purpose of indicating an improved apparatus of the kind men- tioned in the introduction and which by means of simple measures enables attaining a more reliable and rapid working apparatus which does not have the drawbacks con- nected with the prior art apparatus.

The apparatus according to the invention is peculiar in that the hammer head consists of several parts which are coupled together by fastening means. By simple measures it is hereby possible to achieve an apparatus of the kind mentioned in the introduction where the previously mentioned disadvantages are avoided.

By constructing the hammer head so that the hammer head substantially has shape of a body of revolution, and which is peculiar in that the hammer head consists of several parts which are clamped together by means of a number of longitudinal stay bolts, a much improved hammer head construction is achieved, as will be explained below.

Preferably, the hammer head according to the invention is designed so that it consists of a lower wear part which downwardly has a smaller diameter than the rest of the hammer head and of at least one further, substantially cylindric part with an upper substantially flat end part arranged to interact with the electromagnetic coupling.

Suitably, the hammer head according to the invention is thus designed so that the stay bolts are threaded at both ends as one end part of each stay bolt is arranged to be fas- tend in threaded holes of a connecting part of the lower wear part, and that opposite end part of the said stay bolt at the opposite end of the hammer head is arranged to interact with countersunk nuts.

By virtue of this arrangement is achieved that the hammer head's effect in use is maintained, but at the same time"down-time"for replacing the wear part of the ham- mer head is minimised and economised as only the lower wear part of the hammer head needs to be replaced. This part is lighter and therefore easier to transport and handle which means cheaper and faster replacement.

In comparison to the prior art device as described above, the inventive hammer head according to one embodiment of the invention is made of extremely hard steel. When the prior art hammer head becomes worn, it is necessary to stop the hammer and cut the bulging material off the hammer head in order to be able to lift the hammer head in

the device. Furthermore, by cutting material of the hammer head the effective blow of the hammer is seriously reduced. When the effective blow of the hammer head is re- duced to a certain level, i. e. the effect of the hammer has reached a low level, it is nec- essary to replace the entire hammer head. In contrast to this, the inventive hammer head according to one embodiment of the invention is made from a hard steel which deforms less upon impact and by giving the wear part of the hammer head a tapered shape, a certain degree of bulging can be allowed without having to cut the bulging portion off. An effective blow can, therefore, be maintained longer than with prior art devices. When, finally, the head needs to be replaced it is only the wear part which needs to be replaced. The waste is, therefore, considerably less than with traditional hammer heads.

With the purpose of optimising the hammer head according to the invention, it is pref- erably provided with a number of external sliding bodies or"piston rings"consisting of a wear resistant plastic material with small friction, e. g. PEHD.

The hammer head according to the invention is further thus designed in that the sliding bodies or"piston rings"are divided into ring segments shaped with an internal dove- tail profile which is intended for being received in annular, countersunk dovetail grooves in the outer side wall of the hammer head as an inlet opening is formed at at least one location along the periphery of the dovetail grooves, and that a ring segment, preferably the last inserted, is fastened in the inlet opening, e. g. by means of bolts. I. e. all ring segments are thereby prevented from falling out.

In a further advantageous embodiment the connecting coupling is constituted by an electromagnetic coupling comprising an electromagnet arranged to be moved towards an upper end of the hammer head and to be coupled with it by actuating the electro- magnet, and that electric cables for supplying the electromagnet are woven into the wire or otherwise integrated in the wire. It is to be emphasised that the mechanical simplification of the connecting coupling, which may be completely without any mov- able coupling parts, also implies a much improved efficiency and a considerable easier operation.

Furthermore, a significant advantage is achieved in that the lifting movement of the hammer head and release of the same may occur automatically, i. e. the control system of the apparatus may be set either for manual operation with manual release of the hammer head when in top position or for automatic operation where the hammer head is automatically released each time it reaches the top position.

Preferably, the apparatus according to the invention is thus designed so that the elec- tromagnet is formed with a central, throughgoing boring for accommodating a dis- placeable guide pin consisting of a non-magnetic material, e. g. plastic, and which has a lower end part projecting down under the boring, the guide pin having an upper end part preferably interacting with a shock absorber, being connected with a marker dis- posed in a recess in the side wall of the central boring, and which interacts with a sen- sor, e. g. an inductive sensor situated at the upper side of the electromagnet.

Preferably, the apparatus according to the invention is further designed so that the guide pin is made of a wear-resistant plastic material, and that the guide pin has an exchangeable lower wear part consisting of a wear resistant plastic material with small friction, e. g. PEHD.

In order to protect the electromagnet in an optimal way, it may advantageously be sur- rounded by a jacket consisting of a number of ring segments which are clamped to- gether by means of steel wires and shroud screws situated in peripheral recesses, the jacket consisting of a wear resistant plastic material with little friction, e. g. PEHD.

The invention is now explained more closely in connection with the drawing, in which: Fig. 1 shows a side view, partly in section, of an embodiment of an apparatus ac- cording to the invention,

Fig. 2 shows a view from the left of the embodiment in Fig. 1, partly in section, and where a hammer head according to the invention is shown, Fig. 3 shows a side view, partly in section, of an embodiment of a electromagnetic coupling for the apparatus according to the invention, Fig. 4 shows a side view of the suspension for the electromagnetic coupling shown in Fig. 3, Fig. 5 shows a top view of the electromagnetic coupling for the apparatus according to the invention, and Fig. 6 shows a view of a lower wear part of a hammer head according to the inven- tion.

The apparatus 2 shown in Figs. 1 and 2 have socket holes 5 arranged at a lateral fitting 4 for being mounted at the outer end of a jib arm of a large digging machine used in conjunction with the apparatus 2, i. e. hydraulic pressure and electric power for operat- ing the apparatus 2 is provided by the digging machine.

The apparatus 2 comprises a tubular housing 6 which in use is disposed in vertical position and has a lift console section 8 at the top with wire wheels 10 for downward running lifting wires 12, which below the wire wheels 10 are connected with an elec- tromagnetic coupling 14, and which at the other side of the wire wheels 10 are driv- ingly connected with a hydraulic lifting device 16 in the form of a double cut pulley with a hydraulic lifting cylinder 18 that is disposed"floatingly"between blocks 20,22 comprising an upper stationary block 20 and a lower displaceably suspended block 22, respectively.

The block 22 is displacingly suspended in a longitudinal U-section by means of so- called"nonfric"material which in practice consists of a wear resistant plastic material, e. g. PEHD plastic, and substitutes the otherwise common ball bearings. With the ob- ject of minimising wear on the wires, the respective wire wheels are disposed mutually "inline". The said floating suspension of the hydraulic cylinder 18 ensures that this may be dismounted as a single unit for service. The entire U-section, including end

parts, is embedded in shock absorbing material, e. g. rubber, which is secured by frame sections 76 at the outer side of the apparatus housing 6.

The tubular housing 6 is reinforced at the bottom with a number of external, radial ribs 24,26, of which ribs 26 facing the digging machine, i. e. to the same side as the lateral fitting 4, are furthermore provided with lower reinforcements 28 and which special teeth 30 of hardened steel. These steel teeth 30 are intended for gripping behind large stones or rocks for bringing these into position under the apparatus housing 6. The latter may furthermore be provided downwards with an annular collar of wear resistant and shock absorbing plastic material, e. g. PUR.

At the bottom of Fig. 2 is seen a special hammer head 32 consisting of several parts which are clamped together by means of a number of throughgoing stay bolts. The shown hammer head 32 consists of a lower wear part 34 having less diameter that an upper main part 36 and a lower rounded, blunt shape. The wear part 34, also shown in Fig. 6, is made of special steel of high quality and with particularly long service life.

At the top, the wear part 34 has a collar 35 with same outer diameter as the upper main part 36. The collar 35 is made with six threaded holes for a corresponding number of stay bolts extending longitudinally through the main part 36 which by means of the stay bolts and countersunk nuts is clamped together with the wear part 34 in such a way that the main part 36 uppermost has a largely flat, smooth end part 38 arranged for interacting with the electromagnetic coupling 14.

The hammer head 32 is provided with two external, annular"piston rings"or sliding bodies 40 consisting of wear resistant plastic material with small friction, e. g. PEHD.

The sliding bodies 40 are divided into ring segments which in a way not shown are designed with an internal dovetail profile intended for being received in annular, countersunk dovetail grooves in the external side wall of the hammer head 32 as an inlet opening is provided at least at one location along the periphery of the dovetail groove so that the ring segments may be introduced into the dovetail groove one by one and displaced around the periphery of the hammer head, and where the last ring

segment is secured by screws in the inlet opening and thereby ensures all segments against falling out. Alternatively,"piston rings"of mild steel may be used.

The electromagnetic coupling 14 shown in Figs. 3-5 consists of a very powerful electromagnet 42 with a number of not shown annular magnetic coils (indicated in Figs. 1 and 2) which, as something quite novel, has a central throughgoing boring 44 for accommodating a sliding guide pin 46 consisting of non-magnetic material, e. g. plastic, and which has a lower exchangeable end or wear part 48 of wear resistant ma- terial, e. g. PEHD. The lower end part 48 of the guide pin 46 extends below under the 44 while an upper, thicker end part 50 of the guide pin 46, preferably interacting with a shock absorber 52, is connected with a marker 54 situated in a recess 56 in the side wall of an upper part of the central boring 44. Like the end part of the guide pin 46, this upper part of the boring 44 has enlarged diameter.

When the lower end part of the guide pin 46, by the impact of the electromagnetic coupling against the upper side of the hammer head 32, is displaced upwards against the spring action of the shock absorber 52, the marker 54, which is made of a suitable metal, becomes displaced upwards and actuates an inductive sensor 58 placed upon the electromagnetic coupling 14 and connected with the electronic control system (represented by an electric control box 59 which is also placed upon the electromag- netic coupling) for the apparatus 2, i. e. the impact between the hammer head 32 and the electromagnetic coupling 14 is registered so that the electromagnetic coupling 14 may be automatically activated afterwards. This signal may then be used for activating the hydraulic lifting device 16 so that the hammer head 32 is lifted up to its top posi- tion in the tubular housing 6.

In the top position, the top side of the electromagnetic coupling 14 hits a number of shock absorbers 60 (Fig. 4) which in way known per se can comprise sensors, e. g. in- ductive sensors, which by compression of the shock absorbers gives an electronic sig- nal to the control system of the apparatus, where the signal possibly may be used for automatic deactivating the electromagnetic coupling 14 for releasing the hammer head 32.

Furthermore, in Fig. 3 is seen that the electromagnetic coupling is surrounded by a jacket 62 consisting of a number of annular segments 64 engaging around an upper annular thickening 66 of the magnet coupling 14 as well as a lower ring part 68 thereof, where the annular segments 64, consisting of a wear resistant plastic material with small friction, e. g. PEHD, are clamped together around the electromagnetic coupling 14 by means of surrounding wires 70 and shroud screws placed in external peripheral recesses 72 in the segments 64.

Figs. 4 shows inter alia how both lift wires 12 preferably have interwoven electric ca- bles which preferably are providing electric power for the electromagnetic coupling 14 as well as for transferring the necessary electric control signals between the movable parts of the apparatus, e. g. the control signals to and from the sensors. Fig. 5 shows how lifting eyelets 74 for the lift wires 12 are disposed upon the electromagnetic coupling 14.

The apparatus according to the invention may either be driven manually, i. e. with manual release of the hammer head 32, when this is in the top position. Erroneous operation should not be possible as the hammer head 32 can only be released when this, i. e. the electromagnetic coupling 14, is in its top position, or the apparatus may be operated automatically, where the hammer head 32 is automatically released when it reaches the top position, followed by the electromagnetic coupling 14 being sent down immediately after the hammer head 32 and automatically coupling itself to the head 32 in the bottom position for immediate lifting the hammer head 32 upwards again to the top position, and so on. Such automatic operation may e. g. be relevant when using the apparatus for crushing slag in steel works or when using the apparatus for breaking down rock walls.