The present invention relates to powered staplers of the type which use a powering means to drive a striker to strike and eject staples. Particularly, but not exclusively, the invention relates to spring loaded staplers. In such staplers a striker is moved against a biasing force, usually provided by a spring, and then suddenly released to strike a staple located in a staple track and eject the staple. In normal use the striker urges the staple through an item that is to be stapled, and against an anvil which bends the arms of the staple to secure it in place. However, if the stapler is opened up so that the anvil is moved away from the firing mechanism, for example to load the stapler, the striker may eject the staple from the stapler as a projectile. Such staplers eject staples at higher speeds than conventional staplers which rely on a user pushing a staple to eject it and not on the biasing force which powers the staple striker. Due to the higher speeds at which a staple is ejected from such a stapler, they can be dangerous if accidentally fired towards a person for example.

According to the present invention, there is provided a powered stapler comprising a body movable relative to a base, a staple firing mechanism operable to fire a staple from the body along a staple firing path, wherein the stapler comprises restricting means arranged to prevent the staple firing mechanism from firing a staple when the base does not intercept the firing path.

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which:

Figure 1 shows components of a stapler according to a first embodiment of the invention;

Figure 2 shows a view of components of the stapler of Figure 1 from a front end of the stapler;

Figure 3 shows a close up view of part of the stapler of Figure 1 ;

Figure 4 shows a sectional view through the stapler of Figure 1 ;

Figure 5 shows a view through the stapler of Figure 1 with part of its casing removed in a working position; and

Figure 6 shows the stapler of Figure 1 with part of its casing removed in an open condition.

Referring to the Figures, a powered stapler in the form of a spring loaded stapler 10 has an elongate handle 12, an elongate body 14 and an elongate base 16. The handle has a front end 18 and rear end 20. The body has a front end 22 and a rear end 24. The base has a front end 26 and a rear end 28 which is hinged to the rear end 20 of the handle and the rear end 24 of the body.

The handle 12 has an upper wall 30, downwardly extending sidewalls 32,34 and a downwardly extending front wall 36. At the rear end 20 of the handle 12, sidewalls 32,34 have elongate oversized slots 42,44 respectively. Each oversized slot 42, 44 has a front end 421 , 441 and a rear end 422, 442 respectively. The sidewalls 32,34 are parallel and the oversized slots 42,44 are co-axially formed. The rear end 20 of each side wall 32, 34 of the handle is curved and forms a cam surface. The elongate slots 42, 44 are aligned to have one end point towards an apex of the cam shaped end 20.

The base 16 has an elongate, rectangular lower part 46 and upwardly extending sidewalls 48,50 at its rear end 28. The rear end 28 of each sidewall 48, 50 has a stop projection 38, 40 respectively. Each stop projection 38, 40 extends outwardly from the sidewall 48, 50 by a distance greater than the thickness of the sidewalls 32, 34 of the handle 12. The lower part 46 comprises a flat upper surface 460 having an anvil 462 embedded therein at the front end. The anvil is generally oval shaped and formed of metal. The anvil 462 has an anvil slot 464 where a staple is intended to enter an object (such as a stack of papers) being stapled. At spaced intervals, graduating marks 466 are provided to indicate to a user how far they should insert an edge of the object being stapled e.g. 6mm, 12.5mm, 19mm, 25mm. The lower part 46 also has integrally formed plastic ribs 468 to strengthen the base - especially against the shock/impact of a staple being fired into the anvil 462. A closure strip 470 covers the underside of the base 16 and is formed to be friction fit into a lower surface of the lower part 46 to allow the stapler to be conveniently rested on a flat surface. Inner surfaces 52,54 of the parallel upwardly extending sidewalls 48,50 have co-axially formed circular recesses 56,58. Outer surfaces 60,62 of the sidewalls 48,50 have co-axially formed circular projections 64,66 - the projections 64,66 are received in the oversized slots 42,44 on the handle 12 i.e. the diameter of the projections 64, 66 is slightly less than the width of the slots 42, 44, such that the handle 12 is slidably and pivotally mounted relative to the base 16.

On each side, the distance between the stop projection 38, 40 and the respective circular projection 64, 66 is slightly greater than the distance

• between the apex of the handle 12 and the closest end of the oversized slot 42, 44. When the projections 64, 66 are located at the rear ends 421 , 441 of the slots 42, 44, the handle is in a first, forward, working position relative to the body 14 as shown in Figure 5 in which movement of the

handle 12 relative to the body 14 is able to cause firing of a staple. When the projections 64, 66 are located at the front ends 422, 442 of the slots 42, 44, the handle 12 is in a second, rearward, restricted position relative to the body as shown in Figure 6 in which movement of the handle 12 relative to the body 14 is prevented from causing firing of a staple.

The body 14 has an upper wall 68, a lower wall 70, sidewalls 72,74, a front-end wall 76 and a rear end wall 78. At its rear end 24, the body 14 has two co-axial circular projections 80,82 extending outwards from the sidewalls 72,74 respectively. The circular projections 80,82 are arranged to fit into the circular recesses 56,58 of the base 16 such that the body 40 is pivotally mounted to the base 16 by engagement of the projections 80,82 in the recesses 56,58.

All of the projections 64,66,80,82 and recesses/slots 42,44,56,58 are co- axially formed. In addition, the body 14 is narrower than the base 16 which is narrower than the handle 12 (see figure 2) so that the three components 12, 14,16 can be rotatably mounted relative to each other.

Within the body 14, adjacent the lower wall 70, which is the closest part of the body 14 to the base 16, there is a staple channel 83 in which is located an elongate staple track 84. The staple channel 83 is arranged to store a row of staples in an upright configuration. The staple track 84 comprises an elongate, uniform cross-section rail 180 along which the staples can slide. Also slidably mounted on the rail 180 is a staple pusher 86 which is arranged to push staples towards a front end 88 of the staple track 84. The pusher 86 is urged by a compression spring 90 fixed to the front end 88 of the staple track 84. The staple pusher 86 is sized to be able to push staples located in the channel 83 - the staples are also slidably moveable through the channel 83 under the influence of the pusher 86. The staple pusher is of generally U-shaped cross-section with

inturned ends to retain it slidably on the rail 180 which is of generally inverted U-shaped cross-section. At a rear end 89 of the staple track 84, there is a resilient track retaining clip 91. The clip 91 has a retaining extension 910 which abuts against an internal wall 911 of the body 14 to retain the track 84 within the channel 83. The extension 910 is linked to a depressible button 912 which, when pressed, causes the extension 910 to be flexed out of engagement with the wall 911 and allows removal of the staple track 84 from the channel 83. Rows of staples can be loaded into the channel 83 directly through an elongate aperture in the lower wall 70 of the body 14.

A striker channel 92 is formed substantially vertically through the front end of the body 14. The striker channel 92 is formed by two longitudinal grooves 94,96 defined by pairs of parallel spaced ribs extending inwardly from the side walls 72,7 '4 respectively (see figure 4) . The striker channel 92 has an upper end 98 and a lower end 100. A staple ejection aperture 102 is formed in the lower wall 70 of the body 14 where the striker channel 92 meets the lower wall 70. The striker channel 92 is arranged to slidably locate a generally rectangular thin metal striker 104. Each side of the striker 104 is located in a respective one of the longitudinal grooves 94, 96. The striker 104 has a lower rectangular slot 106 near its centre and a higher rectangular aperture 108 near its upper end. The striker 104 also has a forwardly sloped extension 110, which is a small rectangular piece sloping forwardly from an upper edge of the striker 104.

A closed horizontal channel 112 is formed in the body 14 to tightly locate the rear end of a planar rectangular spring 114. The spring 114 has an upper surface 116, a lower surface 118, a front end 120 and a rear end 122. The rear end 122 of the spring 114 is tightly located in the channel 112. In its unstressed condition, the spring 114 is substantially flat and

lies horizontally. The front end 120 of the spring is located in the slot 106 of the striker 104.

Between the front 120 and rear 122 ends of the spring 114, the upper surface 116 of the spring is arranged to contact a circular cross section projection 124 which extends inwardly from the sidewall 74 of the body

14. Since the projection 124 has a circular cross section, it provides a low stress pivot point for the spring 114 to flex about when it is deformed i.e. when the front end 120 of the spring 114 is raised under the influence of a force.

When the spring 114 is in its undeformed position i.e. in line with the channel 112, the striker 104 is located at its lowest point in the striker channel 92 and the bottom of the striker 104 extends flush with the staple ejection aperture 102.

The upper wall 68 of the body 14 has an aperture 126 formed in it. Lifting means in the form of a lever 128 comprises parallel, rigidly connected walls 130, 132 and has a front end 134 and a rear end 136. Towards the front end 134, an oversized slot is provided and located over a further circular projection 140 extending from the sidewall 74 of the body 14. The lever 128 is pivotally mounted on the projection 140. The width of the slot is slightly greater than the diameter of the projection 140 and the length of the slot is significantly greater than the diameter of the projection 140 such that the lever 128 can slide longitudinally relative to the body 14 as well as rotating about the projection 140.

At the front end 134 of the lever 128, a striker engaging formation in the form of a pointed end 142 is provided. The pointed end 142 is arranged to engage the striker 104 by locating in the upper aperture 108 by

abutting against a surface of the striker 104 which defines an upper end of that aperture 108.

At the rear end 136 of the lever 128, an axle 144 extends between the parallel walls 130, 132 to rotatably mount a roller 146 thereon. The roller 146 is arranged to engage with a pair of parallel sloped tracks 147 extending from the upper wall 30 of the handle. The tracks 147 are sloped such that depression of the handle 12 relative to the body 14 causes a desired amount of movement of the lever 128 and hence the striker 104. If the sloped tracks 147 are too steep, the rolling movement of the roller 146 will not be smooth. If the tracks 147 are too shallow, there will not be enough movement of the striker 104 for a predetermined amount of movement of the handle 12.

The tracks 147 extend from a first, lower, rear end 1471 towards the rear of the stapler where they project further downwards from the top of the handle to a second, higher, front end 1472 where they project less far downwards from the top of the handle. Adjacent the front end 1472 is the upper wall 30 of the handle 12. The angle of the upper wall 30 is significantly less than the angle of the sloped tracks 147 so that when the handle 12 is pressed against the roller 146, the lever moves in a desired generally downward vertical direction more when the roller 146 rolls rearwardly along the sloped tracks 147 instead of along the upper wall 30 of the handle 12.

A coiled return spring 148 is mounted on the projection 140 and bears against the other projection 124 and an upper wall 150 of the lever 128, which extends between the parallel walls 130,132 of the lever 128 rearwardly of the pivot 140. This spring 148 biases the lever 128 such that the front end 134 of the lever 128 is urged forwards.

The body 14 also comprises a storage cavity 200 which is closable by a cap 202. Spare staples or a staple remover in the form of an elongate metal member can be stored in the cavity 200. The cap is selectively removable by pulling on a notch 204 formed on the cap 202, which is a friction fit in the cavity opening.

Advantageously the body 14 is formed of two plastic halves held together by screw attachments - this has been found to be stronger than a welded or glued attachment. Significant impact forces are experienced when a staple is fired and screw attachments prolong the life of the stapler compared to a welded/glued attachments which tend to come apart after few staple firings. Screw attachments 400 are provided at the points indicated in Figure 4 at four positions .

Referring to Figures 4 and 5, when the stapler is in a normal operative condition and the body 14 is positioned so that the base 16 intercepts the staple firing path, the stapler 10 can be fired by pressing down on the upper surface 30 of the handle 12, which bears against the roller 146. As the handle 12 is pressed down by a user the sloped tracks 147 engage the roller 146. When the firing path is intercepted by the base 16, the body 14 is in such a position that when the handle 12 engages it, the oversized slots 42, 44 are generally pointed towards the stop projections 38, 40 provided on the base 16. Therefore the projections 64, 66 of the base 16 are located at the rear ends 422, 442 of the over sized slots 42, 44 and the handle is in the working position. This is because, the distance between the stop projections 38, 40 and the respective circular projections 64, 66 is only slightly greater than the distance between the apex of the handle 12 and the rear ends 422, 442 of the over sized slots 42, 44. Therefore, the stop projections 38, 40 prevent the handle 12 from sliding back relative to the projections 64, 66 into the restricted position. The handle 12 is urged back when it is pressed towards the body 14 because the lever

128 is arranged to move the striker 104 against the action of the spring 114 and the stiffness of the spring 114 is sufficient to urge the handle 12 backwards as the tracks 147 move backwards over the roller 146 before any movement of the lever 128 occurs.

When the handle 12 is in its working position but not pressed towards the body 14, the roller 146 is initially in contact with the tracks 147 at a point approximately half way between their front and rear ends. As the handle is further pressed towards the body the roller 146 rolls rearwards along the sloped tracks 147 towards the rear end 1471 and the rear end 136 of the lever 128 is pushed downwards. In turn this raises the striker 104 in the striker channel 92 against the action of the spring 114 which becomes more and more deformed as the striker 104 is raised. As previously stated, the front end 142 of the lever 128 engages the higher aperture 108 of the striker 104. Eventually, the front end 142 of the lever 128 begins to come out of engagement with the striker 104 as the handle 12 is pressed and the end 142 is further raised. At a certain point, the front end 142 disengages the striker 104. The striker 104 then moves downwardly through the striker channel 92 with great force under the action of the spring 114. The striker 104 strikes a staple which is located in a loaded position at the front of the staple track and urged into alignment with the striker channel 92 by the biased staple pusher 86. The striker pushes the staple downwards from its loaded position in the direction of travel of the striker. As the staple moves along this path it passes through the article to be stapled and its legs engage with the anvil and are bent inwards to secure the staple. Across the entire movement of the handle 12 relative to the body 14 the stop projections 38, 40 retain the handle 12 in its working position. Also across this entire range of movement, the roller 146 rolls along the sloped tracks 147. Therefore, depression of the handle relative to the body 14 causes greater vertical movement of the rear end 136 of the lever 128 than if the roller 146 was

merely rolling along the upper wall 30 of the handle 12. Since the roller 146 rolls along the sloped tracks 147 across the entire range of movement of the handle 12 relative to the body 14, sufficient vertical movement of the rear end 136 of the lever 128 is effected to allow the striker 104 to be raised a sufficient distance in the striker channel 92 (i.e. to the point where the end 142 of the lever 128 disengages the striker 104) for a staple to be fired. If this is done the staple will be ejected from its loaded position at high speed from the bottom of the body, in the direction of downward movement of the striker 104. It will be ejected along a firing path that is an extension of the path along which it is pushed by the striker. It will be appreciated that, as the body 14 is rotated away from the base 16 the point at which the firing path intercepts the base moves towards the front end of the base 16. For relative angles of the body and the base above a certain limiting angle, the firing path no longer intercepts the base 16 and passes its front end. If the stapler is allowed to be fired with the body and base at angles above this limiting angle, a staple could be fired from the stapler as a projectile.

After a staple has been fired, the handle 12 is released and the return spring 148 urges the lever 128 forwards and also urges the front end 134 of the lever downwards. The front end 142 of the lever 128 comes into contact with the forwardly sloped extension 110 of the striker 104 and is thus guided by being pushed rearwards (i.e. the projection 140 slides relatively forwardly in relation to the oversized slot) and the front end 142of the lever 128 passes once more below the level of the striker surface which defines the upper end of the higher aperture 108.

Therefore, when a staple is next required to be fired and the handle 12 is pressed again, it will once again cause engagement of the upper aperture

108 by the front end 134 of the lever 128.

The body 14 is rotatably mounted relative to the base 16 so that when reloading staples the body 14 and base 16 can be separated by increasing the angle between them to allow easy access to the staple track 84. During this operation, the body 14 and handle 12 are pivotally separated from the base 16. Since the staple firing mechanism of the present invention is powered by the spring 114, staples are ejected along the staple firing path with great force and are potentially dangerous. Therefore, when the body 14 has been separated from the base 16 to an extent such that the staple firing path is no longer intercepted by the base 16, restricting means is arranged to prevent a staple being fired by relative movement between the handle 12 and the body 14. Referring to Figure 6, in this position, when a user attempts to fire a staple by pressing the handle 12 against the body 14, the handle 12 is urged rearwards into its restricted position. When the user attempts to press the handle 12 against the roller 146, the handle 12 is pushed back by the action of the roller 146 on the tracks 147 such that the projections 64, 66 on the base 16 are located on the front ends 421, 441 of the over sized slots 42, 44. This is possible because the apexes of the side walls 32, 34 of the handle are not obstructed from sliding back by the stop projections 38, 40 when the base 16 does not intercept the staple firing path in contrast with the situation when the base does intercept the staple firing path. The stop projections 38, 40 are arranged to retain the handle 12 in its working position only when the staple firing path is intercepted by the base 16.

If the user attempts to fire a staple in the excessively open position (Figure 6) by pressing the handle 12 towards the body 14, the roller 146 starts off in contact with the sloped tracks 147 near the front end 1472. As the handle is further pressed, the roller 146 rolls rearwards towards the rear end 1471 causing the rear end 136 of the lever 128 to be pushed downwards. This raises the striker 104 in the striker channel 92 against

the action of the spring 114. However the striker is not raised sufficiently for the lever 128 to become disengaged from it. When the handle 12 is fully depressed relative to the body 14, the roller 146 only reaches the mid point of the tracks 147, and is not pushed downwards far enough to cause disengagement with the striker 104 and firing of a staple.

Therefore, advantageously a safety feature of the present invention is to not allow firing of a staple when the relative separation or angle between the body 14 and the base 16 is such that the staple ejection path is not intercepted by the base 16. A staple which is fired by the relative movement between the handle 12 and the body 14 will always hit some part of the base 16. There is thus no possibility of a staple being fired accidentally eg during loading/unloading of staples from the staple track, or indeed on purpose at a person, for example.

In some embodiments, an extended length base may be provided e.g. 1.25, 1.5 or even more times the length of the body. This is longer than a base of a conventional stapler and allows a greater separation between the body and base whilst retaining the feature of this invention that the staple firing path is always intercepted by the base when a staple can be fired.

In some embodiments, a limiting projection may be provided extending downwardly from the upper wall of the handle for example so that relative movement between the handle and the body is restricted when the handle is in its restricted position but not when the handle is in its working position. Such a limiting projection may be used to prevent engagement of the handle with the staple firing mechanism altogether or it may simply be used to limit the extent of engagement. A front wall of the handle may be used as the limiting projection such that in the restricted position of the handle, when the user attempts to press the

handle against the body, the front wall of the handle hits the body to limit movement between the body and the handle.

In other embodiments, alternative reinforcing means may be provided for the base. For example, the base is not ribbed but includes a metal plate placed in the lower part of the base to strengthen the base against impact/shock when a staple is fired.

In further embodiments, the staple striker may be powered by another powering means instead of being spring loaded. For example, pneumatic powering means may be used to power the striker.

Various modifications may be made to the present invention without departing from its scope. Any other mechanism may be used to move the handle between a working position and a restricted position depending upon whether or not the staple firing path is intercepted by the base.

Any other means may be provided to prevent firing of a staple when the staple firing path is not intercepted by the base. For example, the restricting means may be provided between the body and the base instead of the handle and the base .