GB2050229A - Sheet stapling machine - Google Patents

Abstract

A sheet stapling machine (1) for forming cartons comprises a stapling belt (2) driven with an operating speed related to the pitch between directly consecutive staples (27) and a stapling head (5) effective to be periodically oscillated to staple the sheet (17) transported at the operating speed past the stapling belt (2). When photoelectric sensor (9) detects a sheet the speed of belt 2 is reduced from a feed speed to the operating speed. <IMAGE>

Description

SPECIFICATION Sheet stapling machine This invention relates to a sheet stapling machine, in particular for forming cartons, and to a method of stapling such sheets.

As is known, cartons and the like containers are formed from flat sheets which are die-cut, folded over, stapled along their overlapping edges, and finally submitted to finishing and assembling steps.

These operations are mostly automated, there being already available machines for performing them, often with high efficiency.

In particular, the operations upstream and downstream of the stapling step are carried out by machines capable of ensuring a high output rate. The stapling operation, however, is still the currently most time-consuming operational step, in the above processing line, and is accordingly the step which conditions all the others.

The cartons are stapled, in current practice, in the following manner: a conveyor belt takes a sheet under a stationary stapling unit, and stops such as to position the sheet in a predetermined position for the insertion of the first staple; it is then restarted to take the sheet to a suitable position for the following staple application, stops again, and the sheet is given its second staple; thereafter, the conveyor is started once again, and so forth, through all of the staples to be applied.

It is apparent how this procedure is comparatively slow, owing to the frequent stops required and the stopping and starting downtimes. Nevertheless, this practice has been considered heretofore as necessary for an accurate insertion of the staples and changing as required both the location and pitch of the staples.

Another drawback connected with this procedure is that the mechanical members which actuate the continued stopping and starting of the conveyor belt, namely a stop and start for each staple application, are subjected to considerable stresses and wear. This is further aggravated by that, in order to achieve the highest possible production rate, the conveyor belt is started each time at the highest velocity allowed by a given set of conditions.

In the light of the situation outlined hereinabove, and considering the important role played by stapling machines in the processing lines that result in the formation of cartons and the like, this invention sets out to provide novel stapling method and a novel stapling machine, which afford a much higher production rate than conventional ones, by solving the technical problem of eliminating any downtime due to stops.

Within that general aim, it is possible to arrange that the stapling machine of this invention be equipped with a staple feeding device which is commensurate, as to speed and accuracy, to the machine output rate capacity.

It is further possible to arrange that the machine acording to this invention operates in as simplified and straightforward a mode as is possible, with a minimal amount of discontinuities in operation and the utmost degree of reliability.

According to one aspect of this invention, there is provided a sheet stapling machine, in particular for forming cartons, comprising: a stapling unit consisting essentially of a stapling head and mating anvil plate, belt conveying means for transporting the sheets to be stapled to said stapling unit, and control members for said stapling unit and belt conveying means, said sheet stapling machine being characterized in that at said stapling unit, said belt conveying means include a stapling belt driven by actuating means adapted for imparting thereto an operating speed related to the pitch distance between directly consecutive staples, and in that said stapling head can be oscillated periodically to staple the travelling sheets being transported at said operating speed past said stapling belt.

Further features and advantages will be more clearly apparent from the following description of a preferred, though not restrictive, embodiment of the invention, illustrated by way of example only in the accompanying drawings, where: Figure 1 illustrates schematically a series of operations being performed to form a carton from a die-cut sheet, the last whereof is the sheet stapling operation proper; Figure 2 shows how a die-cut, folded and stapled sheet,as per the preceding figure, can be opened to a carton configuration; Figure 3 is a side view of the machine according to the invention; Figure 4 is a plan view of the machine of the preceding figure; Figure 5 shows one element of the machine; Figure 6 shows how the element of Fig. 5 is inserted into a folded sheet, preparatory to stapling; Figure 7 is a schematical view of a stapling unit according to the invention;; Figure 8 is a plan view, with parts removed for clarity, of the preceding figure; Figure 9 is a detail view of a variation of that portion of the stapling machine whereto the staple feeding device is attached; Figure 10 is a sectional view taken along the line X-X of Fig. 9; Figure 11 is a detail view of one portion of the wire feeding device, as viewed partly from above and partly in section; and Figure 12 is a general view of both the device portion shown in Fig. 11 and the guide wherealong the wire is caused to slide.

With reference to the drawing figures, a novel method of stapling cardboard sheets is provided by the invention having, as an actual example of its implementation, the following features.

The cardboard sheets are transported by a conveyor belt which, at the stapling unit, instead of bringing them to a stop moves on at a strictly preset operational speed which is a function of the staple pitch. The stapling unit is then set, preferably and advantageously, to the highest possible constant processing rate compatible with the machine capacity. The pitch distance between two successive staples on a given sheet thus becomes directly proportional to said conveyor belt travel speed, or operational speed.

Another feature of this stapling method is the following: in order to enable the stapling unit to work on constantly moving sheets, as dictated by said belt travelling at operational speed, the stapling unit itself is advantageously set to oscillate such as to accompany periodically the sheet movement, every time that a staple is to be applied.

The tangential velocity of the stapling unit adjacently the sheets is varied such as to be practically equal to that of the sheets. This is possible even by holding constant the preset maximum working rate and hence the stapling unit oscillation period. For example, this can be obtained as follows: if the amplitude of the oscillations is varied while holding the period thereof constant, then said tangential velocity will vary acordingly.

According to a further feature of the inventive method, the conveyor belt is driven at said operational or working speed only while at said stapling unit the portions to be stapled in said sheets are moving past. By contrast, as portions not to be stapled move past it, or before the sheets have reached the stapling unit or after they have left it, the belt is driven at a higher speed than the operational one, and specifically at the highest possible travel speed compatible with the operation rate of the equipment located upstream and downstream of the stapling unit.

Several important advantages are thus secured by this novel method of stapling.

First and foremost, the overall output rate is maximized, compatibly with the capabilities of the equipment employed. In fact, the downtime is completely eliminated because: (a) the operation or working rate of the stapling unit is held at the highest possible level; (b) the sheets are never stopped, not even for stapling, and they keep on travelling at the speed dictated by the pitch selected for the application of the staples and by the operation rate of the stapling unit; (c) when the stapling unit is not required to operate, the sheets are conveyed at the highest convenient speed.

Thus, it has been ascertained that the operation times of a stapling machine can be better than halved with respect to the most advanced of conventional techniques.

The method just described is advantageously implemented by a stapling machine according to the invention, shown in Figs. 3 and 4, for what concerns the general structure thereof, and in Figs. 5 to 8, for what concerns some structural componenst thereof.

The stapling machine, being generally indicated at 1 in the drawings, comprises essentially belt conveying means, with a stapling belt 2 being interposed between a feeding belt 3 and output belt 4, a stapling unit 5 having a stapling head 6 and a mating anvil plate 7, control members 8 for the stapling belt 2, and sensor members 9 which actuate said control members 8.

More specifically, the stapling belt 2 is driven by control members 8 comprising a variable speed motor 10, connected to a drive shaft 11 for the belt 2 through a first drive belt 12, stretched between a first and a second pulley, respectively 1 0a and 1 1 a, mounted coaxially to said motor and drive shaft, respectively. The second pulley 11 a can be engaged for rotation with the drive shaft 11 through a first friction clutch 1 3a.

The control members 8 further include a second motor, not shown, which may be of any known type and is capable of driving at a high travel speed, called herein transport speed, the feeding belt 3 and output belt 4 which, as shown in Fig. 4, are interconnected by belt means 14. Said second motor can also drive the stapling belt 2 through a second drive belt 15, attached at one end to the output belt 14, and at the other end passed around a third pulley 11 b, mounted coaxial to the drive shaft 11 of the stapling belt 2.

The third pulley 11 b can in turn be rigidly connected to the shaft 11 through a second friction clutch 1 3b, set to operate alternately with the first clutch 1 3a.

Both the first and second clutches, 1 3a and 1 3b, are controlled by sensor members 9 comprising, in practice and according to this embodiment, a photocell which can be positioned along a guide 16 extending parallel to the travel direction of the belt 2 and beginning on one side of the stapling unit 5, i.e. on the same side thereof which faces the output belt 4.

It is contemplated that, if the photocell 9 detects the passing by of a sheet 17 to be stapled, then the first clutch 1 3a is actuated to make the second pulley 11 a, and accordingly the variable speed motor 10, rigid with the drive shaft 11. Also contemplated is the concurrent actuation of the stapling unit 5.

The stapling machine comprises, in addition to a control for adjusting the speed of the motor 10, a staple counter whereby the number of staples 27 that the stapling unit is to apply when operated can be set. And it is this staple counter, of any known construction, that controls the stopping of the stapling unit 5 to restore the transport speed of the stapling belt 2, after the preset number of staples have been delivered. In other words, the staple counter controls in practice, after the stapling step, disengagement of the first clutch 13a from the second pulley 11 a and concurrent re-engagement of the second clutch 13b with the third pulley 11 b, connected to the output belt 4, as driven by said second motor.

As mentioned hereinabove, the stapling unit 5 comprises a stapling head 6 and anvil plate 7, as shown particularly in Figs. 5 to 8. The stapling head 5 is mounted for oscillation about a pivot 18 extending substantially horizontal and perpendicular to the direction of advance of the sheets 17. The oscillation movements can be imparted by any known means, as shown for example in dotted lines in Fig. 7, which illustrates a connecting rod 19 swivel connected, at one end, to the stapling head 6, and associated at the other end with a rotary crank or shaft 20, with an arm or eccentricity which can be adjusted at will along a groove 21.

Advantageously, said rotary shaft 20 is rotated at a constant angular velocity, thereby said oscillation movements have constant period, which is selected to be the maximum possible and compatible with the accelerations and decelerations, and thus the efforts, applied to the mechanical components.The speed of the delivery tip 22 of the head 6, tangentially to the sheet 17, is then varied independently of the oscillation period such as to be substantially identical with the sheet travel speed. This is accomplished by varying the eccentricity of the engagement of the connecting rod 19 along the groove 21; thus the amplitude of the head oscillations is changed, thereby the instantaneous velocities are varied, the period being held constant.

The anvil plate 7 is associated by means of an articulated parallelogram type of linkage with the stapling head 6. It is, in fact, carried by an upright 23 one end whereof is pivoted to a stationary cross-member 24, and engaging at an intermediate position a rod 25 connected to the head 6. The anvil plate 7 is shown more clearly in Fig. 5 and has a construction known per se, i.e. similar to that of stationary anvil plates in non-oscillating stapling units. Specifically, it has seat 26 whereon the head 6 is made to act for bending the staples 27, and defines in crosssection two discrete runways overlying each other intended for guiding the sliding movement of the flaps 17a and 1 7b of a sheet 17 to be stapled (Fig. 6).

Fig. 8 shows that the staples 27 are delivered obliquely with respect to the travel direction of the sheet 17, such as to require less room crosswise. the stapling head 6, then, is also set correspondingly oblique (Fig. 4), as is the seat 26 (Fig. 5).

The operation of the machine as a whole, and as described with reference to Figs. 1 to 8, is self-evident.

Initially, the stapling belt 2 is caused to move forward at the highest possible transport speed, in connection relationship with the output belt 4 and feeding belt 3.

The photocell 9 is positioned such that as the leading flap, in the travel direction, of a sheet to be stapled interferes therewith, the stapling head 6 is positioned, with a minimal prearranged advance, at the rearmost area where the first staple 27 is to be inserted.

Also initially, moreover, the operating speed of the belt 2 is set by adjusting the speed of the variable speed motor 10 to suit the staple pitch. Similarly, the position of the connecting rod 19 in the groove 21 is adjusted to proportionate the oscillation velocity of the delivery tip 22 to the operating speed of the belt 2.

The oscillation period is not adjusted, it being fixed and only related to the maximum machine capacity.

By way of illustration, the following values are given herein. It is possible to set for the stapling head 6 and anvil plate 7 a period of one thousand oscillations per minute. The transport speed of the belt 2, which is selected according to the requirements and capacities of the apparatus located upstream and downstream of the stapling machine, can be of 100 meters per minute. The operating speed, when the distance between the staples is selected in the 0.02 to 0.1 meters range, should then vary from 20 to 100 meters per minute. The variable speed motor 10 and the second motor, not shown, which drives the feeding belt 3, output belt 4, and stapling belt 2 at said transport speed, can be left to operate continuously, the transition from transport speed to operating speed or working speed being controlled by the photocell 9 through the clutches 13a and 13b.The opposite transition is instead controlled, through those same clutches, by said staple counter after the stapling unit 5 has applied all of the required staples. In general, with the sheets 17 shown in the drawings, the operating speed is only resorted to over short lengths, the portions to be stapled having but a very limited length.

With reference to Figs. 9 to 12, there will be described next, in detail, a variation of a portion of the stapling machine generally discussed hereinabove, and also in detail, a device for feeding wire which exhibits peculiar features making it particularly suitable for use in the instant stapling machine.

In Fig. 9, the reference numeral 101 denotes said stapling head, as engaging a portion 102 of the stapling machine and being controlled to oscillate by control members 103. These same control members 103, as shown in Fig. 9, also oscillate the anvil plate 104, originally supported by the portion 102 of the stapling machine through an articulated parallelogram 105, set to oscillate by a small bar 106 which is pivoted directly to the stapling head 101.

More specifically, the control members 103 comprise for the oscillating head 101 and anvil plate 104, additionally to the articulated parallelogram 105 and bar 106, a main shaft 107 driven by a motor and rotating at a constant angular velocity in one direction, wherewith an eccentric unit 108 is engaged which is mounted pivotally to a pin 109 rigid with the main shaft 107 but offset with respect to the axis of the shaft. To the eccentric unit 108 a plurality of small connecting rods 110, 111, 112 are engaged pivotally.

The conrod 110 and conrod 111 drive, respectively, a first lever 113 and a second lever 114 which, through swivel joints 115 and 116, move rods 117 and 118 vertically, in turn controlling the shearing of the wire in the stapling head 101 and the formation and application of the staples. The conrod 11 2 operates instead, with the interposition of an auxiliary connecting rod 119, a crank 120 which carries mounted thereon for variable eccentricity a bar 121 directly connected to the stapling head 101. The adjustable eccentricity of the crank 120 affords the possibility of changing the oscillation velocity of the stapling head 101 while maintaining the oscillation period constant. Fig. 9 also shows schematically the paths of the pivot points of the various elements so far described.

The stapling head 101 oscillates at a constant frequency and at a speed related to the engagement position of the bar 121 with the crank 120 about the axis of a pin 122, shown in Figs. 10 and 11. The stapling head 101 includes, in fact, a shaped body 123 which, from the active end 123a adjacent the anvil plate 104, extends vertically to engage itself rigidly with the pin 122, at its top end 123b, e.g. by means of screw fasteners.

The pin 122 is mounted pivotally to the portion 102 of the stapling machine by means of bearings 124. Furthermore, the pin 122, as shown in Figs. 10 and 11, is made rigid, e.g. through a key 125, with an oscillating body 126 which constitutes the housing for a feeding member generally indicated at 127.

In accordance with the invention, the feeding member 127, rigid with the stapling head 101, is adapted for supplying the wire for the stapling head 101. In Figs. 9,10,11, the wire is schematically shown as a dash and dot line at 128, and enters the stapling head 101 at the active or working end 123a thereof.

The feeding member 127 comprises, additionally to the oscillating body 126 rigid with the pin 122 and accordingly with the shaped body 123 of the stapling head 101, a driven gear 129 rotatably carried through bearings on the oscillating body 126 and made rigid, through a small shaft 130, with a driving wheel 131 which contacts the wire 128 directly.

The driven gear 129 meshes with a drive gear 132 wherewith it forms a bevel gear pair, said drive gear being rotatably mounted to the pin 122 and set to rotate by a pulley 133, rigid and coaxial therewith.

As shown more clearly in Figs. 10 and 11, the pulley 133 is associated with a drive belt 134 passed around a drive pulley 135 keyed to the main shaft 107 which originates all the movements of the control members 103 shown in Fig. 9. The drive pulley 135 is locked on the main shift 107 by means of a key, and the drive which from the drive pulley 135 leads, through the belt 134, to the pulley 133 and thus to the drive gear 132 and driven gear 129, is so dimensioned as to gradually reduce the rpm of the main shaft 107.

The drive wheel 131 acts on the wire 128 against an auxiliary wheel 136, more clearly shown in Figs. 11 and 12. To prevent mutual slippage between the wheels 131 and 136, there are provided gear wheels 137 and 138, respectively arranged beside the drive wheel 131 and auxiliary wheel 136 and meshing with each other.

Fig. 12 evidences how the oscillating body 126 is made in two portions: a base portion 139 which is attached to the pin 122 and engages the shaft 130, driven gear 129, drive wheel 131, and gear wheel 137 pivotally, and a cover portion 140 which can be tilted about a pivot pin 141 projecting from the base portion 139 and parallel to the shaft 130. The cover portion 140, in particular, carries the auxiliary wheel 136 and related gear wheel 138, and is held in position by a compression spring 142, which acts at one end on the cover portion 140 itself, and at the other end against a lug 143 on the base portion 139 of the oscillating body.

There are further provided, at the termination of the oscillating body 126, idle-mounted rollers 144, 145, and 146, arranged at the vertices of a triangle with respect to one another, at adjustable positions through an adjusting screw 147 adapted for causing a support 146 of the rollers to slide.

From the oscillating body 126, there extends a substantially rigid guide 148 containing the wire being fed to the stapling head 101. More in detail, the guide 148 is defined by a substantially flattened strip 149 which extends along the whole stretch leading from the oscillating body 126 to the active or working end 123a of the stapling head 101, and by a plurality of shaped stringers 150, laid opposite the strip 149 and serially arranged with respect to one another such as to substantially overlay the strip 149 throughout its length. The shaped stringers 150 have a bridge-like configuration in cross-section such as to define, together with the strip 149 a runway or sliding channel 1 51 for the wire 128.The shaped stringers 1 50 are substantially rigid and engage with the strip 149 through screw means 162 located sideways with respect to the channel 1 51 for the wire 128.

The operation of the parts involved in the feeding of the wire 128, as described in detail with reference to Figures 9 to 12, is the following.

The main shalt 1 O7 of the stapling machine, when rotated at constant speed, pro duces four simultaneous effects: oscillation of the stapling head 101 and anvil plate 104; the operative movements which results, within the stapling head 101, in the formation and application of the metal staples; feeding of the wire 128; and oscillation of the feeding member 127 for the wire 1 28, rigidly with the stapling head 101.

The latter effect, in particular, is achieved by securing the body 1 26 of the feeding member, which supports those means which are materially effective to move the wire forward, fi,tedly to the pin 122, the axis whereof also defines the oscillation center of the stapling head 101 and one end whereof is affixed to the stapling head itself. Inside this oscillating body 126, the wire feeding action is obtained through linkages and gears which are driven by a drive gear 132 coaxial with the pin 1 22 and rotatable with respect thereto.The drive gear 132 is driven in turn by the main shaR 107 through a pulley 133 rigid with the drive gear itself, a drive belt 134, and a drive pulley 1 35 keyed to the main shaR 107.

The oscillating body 126, being rigidly connected to the stapling head 101, can be connected to the active end 1 23a of the head through a substantially rigid guide 1 48 the ends whereof remain at all times strictly equidistant from each other.

The invention achieves its objects.

In fact, a method has been proposed which in practice, and as already mentioned, at least halves the operating times, thus doubling the output potential of the whole processing line which leads from the formation of cartons or the like from die-cut sheets, which line had its weakest point at the very sheet stapling station.

Any downtime has been eliminated: the sheets are no longer stopped for stapling but rather stapled "on the fly", the stapling speed being proportionated to the stapling member highest possible rate or frequency, and each time the stapling unit remains inoperative, the sheets are moved forward at the maximum useful travel speed.

But further advantages can be secured, which are peculiar to the machine as well as the method according to this invention. In fact, on the machine of this invention, the staple pitch changes can be carried out, at any moment with the utmost ease and accuracy, by simply changing the operating speed of the conveyor belt, end concurrently therewith, the oscillation velocity of the delivery tip 22. Even the adaptability of the machine to different size sheets is ensured by the adjustable posi tion of the photocell 9. The accuracy of the staple insertion step and the correct formation whereof is then ensured by the anvil plate 7 oscillating synchronously with the head 6.

Specially advantageous, however, is the fact that the stapling machine of this invention is subjected to minimal oscillations and shaking, as due to operation discontinuities. The stapling belt 2 is never sipped, but only slowed down, and the change of speed does not occur at each staple, as would be the case if stopping were resorted to, but only once for each sheet, at the portion to be stapled.

Moreover, with reference to Figs. 9 to 12, a feeding system is provided which completely eliminates all causes of improper feeding of the wire to the stapling head. This because the guide 1 48 is no longer subjected to stretching, nor flexing, orces which could make the forward movement of the wire inaccurate or even partly hinder it.

Furthermore, by providing a feeding mem- ber which oscillates together with the stapling head and a guide which is not required to consequently accommodate position changes between the stapling head and feeding mem- ber, as would be the case heretofore, an additional advantage has been afforded: namely, a construction for the guide 148 which has only to take into account the re quirement for as smooth a sliding movement of the wire 1 28 as possible. Thus, shaped stringers 1 50 may be provided which can be thick and rigid as required to define a channel 151 of great dimensional accuracy, as well as having treated surfaces and radii of curvature selected with special care and constant in time.

The invention as described is susceptible to many modifications and variations, all of which fall within the scope of the instant inventive concept. Moreover, all of the details can be replaced with other technically equivalent elements.

In practicing the invention, the materials employed and the dimensions may be any ones, to suit individual requirements.

Claims (16)

1. A sheet stapling machine, in particular for forming cartons, comprising: a stapling unit consisting essentially of a stapling head and mating anvil plate, belt conveying means for transporting the sheets to he stapled to said stapling unit, and control members for said stapling unit and belt conveying means, said sheet stapling machine being character- fixed in the SS S 5rr '':lig unit, said belt conveyi mo-ar O.%c::- J stapling at driven by actuating means adapted for imparting thereto an operating speed related to the pitch distance between directly consecutive staples, and in that said stapling head can be oscillated periodically to staple the travelling sheets being transported at said. operating speed past said stapling belt.

2. A sheet stapling machine according to Claim 1, characterized in that said stapling belt is operatively connected to control members adapted to impart thereto a varyingspeed feeding movement, said varying-speed varying alternately from a transport speed to said operating speed, lower than said transport speed, sensor members being provided for sensing the introduction of a sheet to be stapled between said stapling head and said anvil plate, and for concurrently controlling the transition from said transport speed to said operating speed.

3. A sheet stapling machine according to Claim 2, characterized in that said sensor members comprise a photocell the position whereof is adjustable along said stapling belt, said photocell being darkenable by the leading end of a sheet as the cardboard portion to be stapled locates between said stapling head and said anvil plate.

4. A sheet stapling machine according to Claim 2, characterized in that said control members effective to impart to said stapling belt an alternately varying speed feeding movement comprise a variable speed motor adapted for imparting to said belt said operating speed based on the pitch selected for the staples, a second motor adapted for imparting to said belt said transport speed, and friction clutches adapted for alternately engaging, under control by said sensor members, either said first motor or second motor with said stapling belt.

5. A sheet stapling machine according to Claim 1, characterized in that said stapling head is caused to oscillate with a constant frequency or periodicity, the pitch distance between any two successive staples being varied by changing said operating speed of said stapling belt, the velocity of said stapling head tangentially to the sheets to be stapled being adjusted independently of said frequency.

6. A sheet stapling machine according to Claim 1, characterized in that said anvil plate is set to oscillate synchronously with said stapling head, with a constant frequency or periodicity at said feeding speed, in the direction of travel of said stapling belt, equivalent to said operating speed.

7. A sheet stapling machine according to Claim 1, characterized in that the wire fed to said stapling head for forming staples is inserted through a substantially rigid guide fixed at one end to said stapling head and at the opposite end to a feeding member operative to impart a forward movement to said wire, and in that said feeding member is rigid with said stapling head and set to oscillate therewith such as to keep the distance between and mutual positions of the ends of said guide constant.

8. A sheet stapling machine according to Claim 7, characterized in that said feeding member comprises an oscillating body, whereinto are pivotally inserted devices effective to feed said wire, said body being rigid with a pin supporting said stapling head pivotally, whereto it is fixed at one end.

9. A sheet stapling machine according to Claim 8, characterized in that, internally to said oscillating body, there are provided a drive wheel and auxiliary wheel adapted for nipping said wire therebetween, and in that said drive wheel is mounted rigid, through a small shaft, with a driven gear directly meshing with a drive gear located externally to said oscillating body and coaxial with said pin.

10. A sheet stapling machine according to Claim 9, characterized in that the drive gear, transmitting the feeding movement of the wire to the inside of said oscillating body, is rotatable about said pin, whereon it is inserted coaxially, and is driven, through pulleys and drive belts, by said main shaft controlling the oscillation of said stapling head and the formation and application of the staples.

11. A sheet stapling machine according to Claim 7, characterized in that said substantially rigid guide comprises a substantially flattened strip extending over the entire length of said guide, and a plurality of shaped stringers arranged consecutively to one another on said strip, wherewith said stringers are engaged detachably, said stringers being shaped substantially bridge-like, as viewed in cross-section, and defining, in cooperation with said flattened strip, a channel for the sliding of said wire therethrough.

12. A method of stapling sheets, particularly for forming cartons, characterized in that it comprises the steps of: feeding the sheets, at the time of stapling them, at a selected operating speed, and applying the staples by means of a stapling unit set to oscillate such as to have a velocity, tangentially to the sheets, similar to said operating speed, and a frequency of oscillation fixed and selected to be the highest possible, said operating speed of said belt being directly proportional to the pitch distance between consecutive staples.

13. A method according to Claim 12, characterized in that said sheets are caused to move forward at said operating speed while being stapled, before and after the stapling said stapling belt being caused to move forward at a transport speed higher than said operating speed.

14. A sheet stapling machine, in particular for forming cartons, substantially as herein described with reference to the accompanying drawings.

15. A method of stapling sheets, particularly for forming cartons, substantially as herein described with reference to the accompanying drawings.

16. Any novel element, or combination of elements, herein described and/or shown in the accompanying drawings, irrespective of whether the present claim is within the scope of, or relates to the same invention as, any of the preceding claims.