Electrically powered stapler

Stapler (1) which in the course of a reciprocating working stroke (V) staples a workpiece (4), preferably a sheaf of papers, which stapler is powered by an electric motor which, via a transmission arrangement (5) drives the stapler during the working stroke, whereby the motor is activated and initiates the working stroke from a certain starting region as a result of the workpiece moving a trigger (32,33) which forms part of a trigger device (6) to a position at which a circuit-breaker (7), which forms part of the same electrical circuit (8) as the motor is connected to, is closed by the trigger, and whereby a release arrangement (9) connected to, and operatively acted upon, by a rotating means (11) which forms part of the transmission arrangement moves the trigger during the return phase of the working stroke to a non-closing position at which the circuit-breaker returns to an open position, thereby breaking the electric circuit and deactivating the motor, with the result that the working stroke ends in the starting region, whereby the trigger (32,33), when it has been moved to close the circuit-breaker (7) and the working stroke has been initiated by the force from a first elastic means (21), remains in the position at which it closes the circuit-breaker.

TECHNICAL FIELD

The present invention relates to a stapler which in the course of a reciprocating working stroke staples a workpiece, preferably a sheaf of papers, which stapler is powered by an electric motor which, via a transmission arrangement, drives the stapler during the working stroke, whereby the motor is activated and initiates the working stroke from a certain starting region as a result of the workpiece moving a trigger which forms part of a trigger device to a position at which a circuit-breaker, which forms part of an electrical circuit to which the motor is connected, is closed by the trigger, and whereby a release arrangement connected to and operatively acted upon by a rotating means forming part of the transmission arrangement moves the trigger, during the return phase of the working stroke, to a non-closing position at which the circuit-breaker returns to an open position, thereby breaking the electrical circuit and deactivating the motor, so that the working stroke ends in the starting region.

STATE OF THE ART

Staplers of the kind indicated above are previously known and one such is disclosed in all essentials in U.S. Pat. No. 6,135,337. However, the stapler therein described has a trigger device which comprises a circle segment disc supported for rotation about a shaft which forms part of the transmission arrangement, which disc, during parts of a revolution, is caused by a shaft wheel attached to the shaft to rotate with the shaft such a distance and to such a point that it is thereafter brought by gravity and the rotatable bearing to a position from which, when the workpiece is removed, it is brought to its initial position at which it can be activated and commence a new working stroke.

The disadvantage of that previous solution, however, is that for the trigger device to function the circle segment disc needs to be brought by gravity to the initial position, which in certain cases does not happen if the slidable bearing is for any reason blocked or the stapler is in such a position that gravity acts in an opposite direction. The situation of the disc being blocked may occur where the stapler is used for a long period in a dirty environment, e.g. in a workshop environment, and the situation of the stapler being in a position in which gravity acts in an opposite direction may occur where the stapler is built into a copier or printer and has for space reasons to be fitted facing upside down.

Problem

There is thus a need for a stapler of the kind indicated in the introduction which has a trigger device so disposed as to be unaffected by the environment in which the stapler is used and the position in which the stapler is fitted.

Proposed Solution

The present invention overcomes the disadvantages indicated above with a stapler of the kind indicated in the introduction which is characterised in that the trigger, when it has been caused to close the circuit-breaker and the working stroke has been initiated by the force from a first elastic means, is held in that position.

The present invention is further characterised in that the trigger comprises a first trigger arm and a second trigger arm, that the first arm is struck by the workpiece, that the second arm is situated between the first aim and the circuit-breaker and that the release arrangement, during the return phase of the working stroke, moves the second arm from a first position at which it is in contact with the circuit-breaker to a second position at which it is not in contact with the circuit-breaker, with the result that the circuit-breaker returns to an open position.

The present invention is still further characterised in that the second trigger arm comprises a second trigger plate which itself comprises a locking element which, when the trigger arm has moved to the second position, is itself brought to locking engagement with a recess in a first trigger plate attached to the first trigger arm and is held in that position by the force from a third elastic means, thereby preventing the second trigger arm from returning to the first position until the release arrangement has blocked the force from the first elastic means in such a way that the first trigger arm can be caused by the force from a second elastic means to return to the non-closed position, after which the second trigger arm is returned to the first position by the force from the third elastic means.

The present invention is also characterised in that the first elastic means takes the form of a helical spring.

Finally, the present invention is characterised in that the second elastic means takes the form of a helical spring.

PREFERRED EMBODIMENT EXAMPLE

FIGS. 1 and 2are general views of a stapler1which accommodates the present invention. They show that the stapler comprises a base element2and a stapling head3. A workpiece4for stapling is placed on the base element. The drawings also show a transmission arrangement5driven by an undepicted electric motor. The transmission arrangement in a known manner drives the base element and the stapling head relative to one another in a reciprocating working stroke which is indicated by the double arrow V and which has a starting region position in which the stapling head and the base element are at a distance from one another. During this working stroke, stapling of the workpiece is effected in a known manner by a staple being driven, by a driver connected to driving arms (which staple driver and driving arms are not depicted in the drawings), into the workpiece and this driving takes place, as is obvious to one skilled in the art, when the stapling head is driven down towards the base element, after which the stapling head, having reached a reversing position of the transmission arrangement, is driven in an opposite direction from the base element in order to return to its starting region position. InFIG. 1the stapler is in its starting region position in which the stapling head is at a distance from the base element, and inFIG. 2the stapling head is at the reversing position and in contact with the workpiece placed on the base element. The stapling head and the base element are thus driven by the transmission arrangement5, which is itself driven by an electric motor not depicted in the drawings, in a reciprocating working stroke indicated by the double arrow V, during which working stroke a staple in a known manner is driven into, and staples, the workpiece. The drawings also show a trigger device6which, when stapling is to take place, is struck by the workpiece4and thereby caused to close an electric circuit-breaker7, which circuit-breaker is in a known manner connected to and forms part of an electric circuit8very schematically depicted inFIG. 2, which circuit the electrically powered motor also forms part of, and, as will be obvious to one skilled in the art, the motor is started by the circuit-breaker being closed, with the result that the stapler performs its working stroke until the circuit-breaker and the circuit open, whereupon the working stroke ends. The drawings also show a release arrangement9which during the working stroke, in a manner which will be described below, releases the trigger from contact with the circuit-breaker, thereby breaking the electric circuit.

The construction of the trigger device6and the release arrangement9will now be explained in detail with reference toFIGS. 3 and 4. These drawings show a frame portion10which forms part of the stapling head3. A driving wheel11forming part of the transmission arrangement is supported for rotation relative to the frame portion by means of a shaft12. The driving wheel is provided with a first cam curve13and a second cam curve14. A first link arm15is supported relative to the shaft12in that the shaft extends through an oblong first aperture16disposed in the link arm. The aperture16is so disposed relative to the shaft that the shaft can move along the aperture, thereby making it possible for the link arm to move in a radial direction relative to the shaft12. Outside the first link arm15, a second link arm17is supported by means of an oblong second aperture18and this support is also such that the arm can move in a radial direction relative to the shaft12. The first link arm is provided with a first spigot19and the second link aim with a second spigot20. An elastic means21is disposed between the spigots19and20, in the form of a helical spring which connects the first and second link arms in that each of the spigots extends into the helical spring from its respective side. The first link arm15has at its front edge a first flange22which itself has a slide surface23whose function will be indicated in the description below. The second link arm has at its front edge an abutment shoulder24whose function will likewise be indicated in the description below. Each of the link alms also has at its front edge an oblong slot25,26respectively, which are each coupled to a spigot27attached to the frame10and are so disposed that the slots slide along the spigot when, as will be described below, the link arms move in a radial direction relative to, and along, the shaft spigot12. The second link arm17is provided at the rear edge with a notch28which has a first contact surface29which, in a manner which will be described below, cooperates with the second cam curve14.FIG. 5shows the first link aim15provided with a flange30which has a second contact surface31which cooperates with the first cam curve13, which cooperation will be described below.FIGS. 3 and 4also show a first trigger arm32and a second trigger aim33. The first trigger arm comprises an elongate member34provided with a hole35by means of which the member is supported for pivoting relative to the spigot27, and the fact that the hole35is somewhat larger than the spigot27means that the trigger aim can pivot about the spigot27in the direction indicated by the arcuate double arrow P. A first trigger plate36is disposed at the lower edge of the member and a contact link37is disposed at the upper edge of the member. The trigger plate36is provided with a hook means38to which is connected a first end39of a second elastic means40in the form of a helical spring which has its second end41connected to a pin42disposed in the frame when the trigger arm32is fitted to the spigot27. The trigger plate36is further provided with a recess43whose function will be indicated in the description below. The second trigger arm33comprises a second elongate member44provided with a third oblong aperture45which extends in the longitudinal direction of the member. The trigger aim33is fitted to the spigot27by the oblong aperture45being moved onto the spigot27. The trigger arm can move up and down on the spigot27in the direction indicated by the double arrow U and in the direction indicated by the double arrow P. The upper portion of the trigger arm is provided with an extension46which has a sliding plane47which, as will be indicated below, cooperates with the slide surface23. The lower portion of the second trigger aim33is provided with a second trigger plate48which has a locking element49. The second trigger arm is also provided with a peg50. A third elastic means51in the form of a helical spring is connected by a first loop52to the hook means38and by a second loop53to the peg50when the second trigger arm is fitted to the spigot27. The trigger plate48is provided with a thrust spigot54which, when the trigger arm is fitted to the spigot27, is in contact with a breaker arm55forming part of the electric circuit-breaker7which in a known manner is fitted to the frame10.

The function of the trigger device and the release arrangement are described below in detail with reference toFIGS. 5-13. InFIG. 6the trigger device6and the arrangement9are in the position at which they are when the stapler is in its starting region. In this situation the first trigger arm32is moved by the second elastic means40in the direction indicated by the arrow F. The second trigger arm33is also moved by the third elastic means in the direction indicated by the arrow F. In this situation the thrust spigot54is in such a position that the breaker arm55is not applied (this is not depicted in the drawings), so the circuit-breaker is in an open position whereby there is no power supply to the electric motor. The second link arm17of the release arrangement is in contact via the contact surface29with the second cam curve14(which is depicted in broken lines), thereby preventing the link arm17from moving in the direction indicated by the arrow N. The first link arm15is in contact via the flange30with the first cam curve13(cam and flange both depicted in broken lines), thereby preventing the first elastic means21, which in this situation is tensioned and in contact with a first seat56on the first link arm and a second seat57on the second link arm, from moving the first link arm in the direction M, which is the opposite direction to the direction N. This arrangement results in the means21endeavouring to move the arms15and17away from one another. A workpiece which is to be stapled strikes the first trigger plate36, as indicated by the arrow A, and the trigger plate moves, together with the second trigger plate48, in the direction A, thereby causing the thrust spigot54to move the breaker arm55to close the circuit-breaker, as illustrated inFIG. 12, with the result that the motor starts and, via the transmission arrangement, rotates the driving wheel11in the direction indicated by the arrow R. At the same time, the second elastic means40is tensioned. When the wheel rotates, the cam curve14moves and the contact between the cam curve and the contact surface29ceases, with the result that the means21moves the arm17in the direction N so that the abutment shoulder24comes into contact with the contact link37, and the fact that the tensile force with which the means21is loaded is greater in that direction than the force with which the means40, when tensioned, is loaded in an opposite direction results in the trigger arms being held in the position in which the circuit-breaker is closed. When the motor has driven the stapler in the course of the working stroke to the situation in which the wheel has rotated to the position depicted inFIG. 8, the working stroke is in its return phase and the first cam curve13pushes the flange30on the first link arm15in the direction N. When the link arm15moves in the direction N, the slide surface23comes into contact with the slide plane47of the second trigger arm33and the trigger arm33moves upwards, thereby taking the thrust spigot54out of engagement with the breaker arm55(as illustrated inFIG. 13) and hence bringing the circuit-breaker7to an open position and breaking the electric circuit8, with the result that the motor stops. When the trigger arm has moved up, the third elastic means51is tensioned and pulls the second trigger arm33towards the first trigger arm32, with the result that the locking element49is inserted in the recess43as depicted inFIGS. 9 and 11, thereby securing the second trigger arm33in this raised position. Owing to the rotational torque which the motor has at the time when the electric current is disconnected, the motor continues to rotate and the working stroke returns to the starting region as depicted inFIG. 10, in which region the cam curve14returns to engagement with the contact surface29, with the result that the second link arm17returns to its starting position and at the same time the first cam curve13reaches the position at which the means21can push the first link arm15in the direction M, thereby causing the trigger arms to cease to be acted upon by the link arms15and17respectively, with the result that the second elastic means40moves the first trigger arm32to its original position while at the same time the third elastic means51moves the second trigger arm33to its original position.

The trigger being acted upon and held in the position at which the circuit-breaker is closed by an elastic means provides assurance that the trigger will hold the circuit-breaker in a closed position irrespective of the orientation of the stapler.

The fact that the release arrangement moves the trigger device to a position such that the circuit-breaker is brought to an open position despite the workpiece holding the trigger plates in a pushed-in position provides assurance that the stapler will not perform more than one stroke when the workpiece moves the trigger to the position at which the circuit-breaker closes.