US2547079A - Transmission for drilling machines - Google Patents

Description

April 3, l951 I J. GERENTES 2,547,079

TRANSMISSION FOR DRILLING MACHINES Filed April 17, 1948 f', m m\ Patented Apr. 3, 1951 TRANSMSSION FOR DRLLING MACHINES .lean Gerentes, Saint-Etienne, France, assigner to Constructions Electro-Mecaniques de Saint- Etienne, Saint-Etienne, France, a French com- Dany Application April 17, 1948, Serial No. 21,649 In France May 5, 1947 7 Claims.

The present invention relates to drilling-machines which have to bore holes in hard and heterogeneous materials, especially minerals.

The portable ele'tric drilling-machines used up to the present mine*- and quarries, are of two types. In onel the dr is fed to the work by the workman through pushing axially on the machine; in the other, the drill is fed to the work by a step-up gear device, the machine being mounted on a head-frame.

The second type of drilling-machine mentioned above, is more suitable especially in the case of work in hard or heterogeneous ores and for which a heavy feed pressure is necessary so that the drill can normally carry out the perforating.

This feed pressure is obtained in different ways either by assembling' the drilling-machine on an arm and by feeding it to the work by screw or rack-or else by keeping the drilling-machine xed, and in making the drill-piece move forward at the same time as the rotary motion is produced.

With the last manner of procedure, the feed movement is given by the driving shaft which at the same time causes the rotary motion of the drill-piece. The feed mechanism is often friotionally-furnished, but the characteristic of this device is to give a fixed travel per turn, whatever be the hardness of the rocks drilled, until the elements of the friction device Slips the one on the other or the motor stalls. The axial force to be applied on the drill can become considerable in certain rocks and this fact compels to increase the size and consequently the `weight of the members of the machine-so that said machine becomes very uneasy to handle.

The invention has for its object to provide an electric rotary drilling-machine, with variable automatic feed movement, light therefore easily handled, more particularly intended for mines and quarries.

The invention has more especially for its object to provide a drilling machine which comprises two independent mechanisms, one for the feed movement, and the other for the rotation of the drill-piece, these mechanisms being driven by two separate electric motors, the motor for the *eed movement being a motor having a high rotor slip so that the speed of said motor varies with the hardness of the material cored and said mechanisms being combined so that the feed speed is a direct function of the difference between the speeds of said motors.

Owing to these features, the feel-,1L of the drillpiece is automatically variable, according to the hardness of the material bored, for said hardness modifies automatically the speed of the corespcnding motor; said fact is very important for machines which, having to bore holes which may exceed a depth of two metres, meet with different strata of material of quite different hardness.

Other features of the invention will be apparent from the following description.

On the accompanying drawing, given merely as an example:

Fig. i shows a longitudinal section of a drillingmachine according to the invention;

Fig. 2 is a front view thereof;

Fig. 3 is, in section, a detail of embodiment of the nut, causing the displacement of the drillpiece;

Fig. l is an electric wiring diagram.

According to the example shown, the machine comprises a casing formed of two parts l and 2, joined through the medium of a cheek or crosspiece 3.

In the casing l is housed a main electric motor, of which the shaft 5 rotates in ball-bearings 6 and l; it is provided at the back with a fan 8 intended to create a current of cold air along the sides of the casing of the motor in order to cool them.

In the front, the shaft 5 extends through the cross-piece and ends in the form of a toothed part 5l. Said toothed part 9 engages, through the medium of an idle pinion l0, with a toothed crown ll. The pinion i!! is freely centered, on the one hand oy means of a ball-bearing lll on a trunnion ll integral with the cross-piece 3, and on the other hand by means of another trunnion 42 integral with said pinion l@ in a ball-bearing 43 carried the part 2 of thev casing. The crown l l comprises a hub, centred by bearings l2 and l2-- in said cross-piece 3 and in a bush 2l. In this hub is keyed slidingly, according to the axis XX, a screw $3, by grooves Ita which give to this screw the rotary movement conveyed by the gear train.

On the endv of the screw 53 is secured the drivdevioe lll of t1 e drill-piece. A housing Lia is provided inside the screw for the centring of the said drill-piece.

The longitudinal displacements of the screw i3 in the direction of the arrow fr in reverse direction, are given to independently of the above described mechanism which ensures its rotation, by the following mechanism.

In the casing 2 is placed a Second electric auxiliary motor l5. t is constituted by a reversible motor of a well known type enabling a high rotor slip, that is to say, a motor in which the rotary speed of the rotor can decrease in very big proportions when the resisting torque increases. This motor may be for instance an asynchron motor having a particularly solid squirrel-cage rotor. The shaft it of said motor rotates in the casing 2 and in a cover Il secured to this casing, drives, through the medium of a pinion it keyed on it, and of an intermediary idle pinion lil centered on the trunnion ft2, a toothed crown 26. This crown is keyed on the bushing 2l. rlhis bushing, concentric to the screw i3, is centered by the ball- bearings 22 and 23 in the casing 2. These bearings are locked longitudinally by a nut 24.

In the bushing 2l is mounted a nut 25 driven by lugs 2li (Fig. 3) engaging in the notches of the said bushing 2l; this nut is locked on the bushing by a check-nut Eea. 'In this nut 2li is screwed the screw i3.

Fig. 4 shows the electric devices and their connections in the case of feeding by alternating current.

The current collector 2t is a live-plugged one 2e, corresponding to three feeding leads 3Q and to two `pilot leads 3l serving to control the relays which open or cut olf the main current (usual relays, not shown, placed in a cabinet apart from the drilling-machine). A control switch 32 placed in the circuit of these leads 3i therefore allows the putting under tension or out of tension of the main leads Sii.

The main motor i driving in rotation the Vscrew i3, is connected directly to the three leads 3e.

On the contrary, the feeding motor l is connected to the three leads 3i? by a reversible switch of a conventional type with twin keys 33 and contact-studs 3d and 35. In a certain position (keys 33 on the contact-studs 3d for example), the motor l5 turns in the same direction as the main motor and this corresponds to .the feeding movement of the tool in the direction of the arrow f1; in another position, the motor l5 turns in the reverse direction to the main motor and this corresponds to the backward return of the tool.

The machine operates as follows: by closing the control switch 32, the lead Sil is put under tension. The main motor fl, fed, drives in rotary motion the screw i3 through the gear trains il, i, Il and as a result, the drill-piece.

By closing the switch twin keys 33 on the contact-studs 34, the auxiliary motor i5 is fed so that this motor l5 turns in the same direction .as the motor il. The nut is therefore driven in rotation around the axis XX in the same direction as the screw le, and this at a higher speed than that of the screw, the ratio of the train I8, I9, 2@ being lower than the ratio of the train El, il), i I. The screw i3 therefore undergoes towards the front a longitudinal displacement whose value depends on the difference between the speeds of the nut and of the screw.

progressively with the feed movement of the drill-piece in the direction of the arrow f1, if the Ymaterials met with have a variable hardness, there results a corresponding variation of the resistance to the feeding movements and an increase of the resisting torque on the motor l5. This motor, by reason of its high-rotor slip coeicient, slows up, and it is the same with the lfeeding movement which finds itself stopped when the nut turns at the same speed as the screw. The feeding thus remains constantly proportional to the difficulty of boring. The pressure on the drill-piece is therefore adjusted automatically, according to the hardness of the rock.

By reversing the switch twin keys 32 on the contact-studs 35, the rotary direction of the auxiliary motor is changed and, as then no resistance is offered to the displacement towards the rear of the screw iii, the motor turns at its highest speed, and there is obtained, by addition of the reverse speeds of the screw i3 and the nut 25, a very quick return axial travel of the drill-piece.

lt is advisable to note, moreover, that the arrangement described, in which the members situated around the screw it forming a pilingup between the ball-bearingi2 and the nut iii, permits an easy and very quick dismantling and assembly of the different devices.

The nut 25 is easily interchangeable through simply unscrewing the check-nut 2da; this allows an easy adapting of the machine according to the nature of the ground or other heterogeneous material to be drilled, by replacement of the nut 25 and the screw I3 by another set having a different thread.

The invention is natu-rally not limited to the embodiment shown and described, which has been chosen merely as an example.

Having now described my invention what I claim as new and desire to secure by Letters Patent is:

l. In an electric drilling machine a casing, a screw-threaded shaft projecting at least by one of its ends from said casing in the walls of which it is mounted so as to be able to rotate around and to slide along its own axis, a tool-holder carried by said end outside said casing, a first .electro-mechanical driving device located in said casing and comprising a gear member rotatably mounted in said casing and in which said shaft is slidingly keyed and. an electric motor secured in said casing for imparting to said gear member a rotation and a second electro-mechanical. driving device located inside said casing and comprising a nut which is rotatably mounted in said casing so as to be unable to move longitudinally and in which said shaft is screwed and an auxiliary motor having a high rotor slip for driving positively said nut, so that the feeding axial speed and the return axial speed of said shaft are direct functions of the difference between the speeds of rotation imparted by said motors respectively to said shaft and to said nut.

2. An electric drilling machine according t0 claim l wherein said auxiliary motor is a reversible motor and is combined with a control switch disposed in its feeding circuit.

3. An electric drilling machine according to claim 1 wherein said first electro-mechanical driving device comprises said main motor, a pinion secured on the shaft of said motor, an idle intermediate pinion mounted in said casing to rotate freely around its axis which is stationary and said gear member in which the screw shaft is slidingly keyed, said idle pinion meshing with said pinion secured on the shaft of said motor and with said gear member.

4. An electric drilling machine according to claim l wherein said second electro-mechanical driving device comprises between said auxiliary electric motor and said nut a gear transmission comprising a pinion secured on the shaft of said auxiliary motor, an intermediate idle pinion mounted in said casing to rotate freely around its axis which is stationary and a toothed bushing rotatably mounted in said casing and in which is keyed said nut, said intermediate idle pinion meshing with said pinion secured on said shaft of the auxiliary motor and with said bushing.

5. An electric drilling machine comprising in combination a casing, a screw-threaded shaft projecting at least by one of its ends from said casing in the walls of which it is mounted so as to be able to rotate around and to slide along its own axis, a tool-holder secured to said end of said shaft, a first electro-mechanical driving device which is located in said casing and comprises a crowned gear member rotatably7 mounted in said casing and in which said shaft is slidingly keyed, a main electric motor secured to said casing and a first gear train connecting said motor to said crowned gear member, a second electromechanical driving device situated inside said casing and comprising a toothed bushing rotatably mounted in said casing so as to be unable to move longitudinally, a nut which is keyed in said bushing and in which said shaft is screwed, an auxiliary reversible electric motor having a high rotor slip and a second gear train connecting said auxiliary motor to said bushing, and a control switch placed in the feeding circuit of said auxiliary motor.

6. An electric drilling machine according to claim 5 wherein the ratio of said rst gear train is lower than the ratio of said second gear train and said switch is so arranged that for the feeding drive said nut turns in the same direction as said screw-threaded shaft but quicker than it.

7. An electric drilling machine which comprises in combination a casing formed by a front wall, an intermediate wall and a rear part, assembled together so as to form a front compartment and a rear compartment, said front wall being provided with an aperture and said intermediate wall being provided in said front compartment with a bearing recess, a rst ball-bearing centered in said bearing recess, a crowned gear member having a hollow hub formed by axial projections from both faces of said member, one of said projections being centered in said rst ball-bearing, a screw-threaded shaft the longitudinal axis of which coincides with the axis of said hub in which said shaft is slidingly keyed, said shaft projecting at least by one extremity which forms a part of a tool-holder, from said casing through said aperture of said front Wall of said casing in the intermediate wall and rear part of which said shaft is mounted so as to be able to rotate around and to slide along its own axis, a second ball-bearing centered on the other projection of said hub, at least a third ball-bearing coaxial to said first and second ball-bearings and secured in said casing in said front compartment, a bushing provided with outer teeth and centered on said rst and third ball-bearings, a nut keyed in said bushing uand in which said screw-threaded shaft is screwed, a check-nut screwed on said bushing in said aperture of said front wall and abutting said nut to keep said latter in position longitudinally with respect to said bushing, a main electric motor located and secured in said rear compartment, the shaft of said motor protruding into said front compartment through said intermediate wall, a first gear transmission in said front compartment between the front end of said shaft of said main motor and said crowned gear in order to rotate the screw-threaded shaft around its own longitudinal axis, an auxiliary reversible electric motor having a high rotor slip, located and secured in said front compartment, a second transmission gear between said auxiliary motor and said bushing to rotate said nut, and control electric switch placed in the feeding circuit of said auxiliary motor.

JEAN GRENTS.

REFEREN CES CITED The following references are of record in the 4le of this patent:

UNITED STATES PATENTS Number Name Date 1,221,391 Thullen Apr. 3, 1917 2,023,841 Kingsbury Dec. 10, 1935 2,333,341 Scrivener Nov. 2, 1943 2,434,120 Paget Jan. 6, 1948

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