A spring energized stapler includes a “high start” design wherein a striker has a rest position above the staple track. A handle is pressed to energize a power spring while the striker remains stationary. At a predetermined position of the handle, the striker is released to eject a staple. A subassembly of a cage and the power spring provides a preload to the power spring in the rest position. The subassembly is separately movable from the handle to allow a handle pressing end to move farther than the striker's distance of travel. The handle includes a movable pivot location to enable enhanced motion of the handle pressing end. Alternatively, an optional lever links the striker to the power spring to provide leverage upon the power spring. A release latch may be mounted in front of the striker to be engaged by the lever or the handle.

FIELD OF THE INVENTION

The present invention relates to spring powered desktop staplers. More precisely, the present invention relates to improvements to a spring-actuated stapler with a striker having an initial “high start” position.

BACKGROUND OF THE INVENTION

Spring powered staplers and staple guns operate by driving a striker with a power spring. The striker ejects a staple by impact blow. In a desktop stapler, the staple is ejected into an anvil of a pivotably attached base. Two general principles are used. In the first design, the striker has an initial position in front of a staple track. The striker is lifted against the force of the power spring to a position above the staple track. The striker is released to impact and eject the staple. This design may be referred to as a “low start” stapler. A second design uses a “high start” position. That is, the striker has an initial position above the staples loaded on the staple feed track. The power spring is deflected while the striker does not move. At a predetermined position of the power spring deflection, the striker is released to accelerate into and eject a staple. Typical desktop staplers use a high start design. However, in such conventional high start designs, the striker is driven directly by the handle with no power spring to store energy that could be used to drive the striker. There is further no release mechanism for the striker since the striker simply presses the staples directly under handle pressure.

In conventional high start designs that do use a power spring, the power spring is either unloaded or preloaded in the rest position. Different methods are used to reset the mechanism. U.S. Pat. No. 4,463,890 (Ruskin) shows a desktop stapler with a preloaded spring. Restrainer 42cis an element of the handle and moves directly with the handle. U.S. Pat. No. 5,356,063 (Perez) shows lever 53 with tips 48 engaging striker 24. At a predetermined position of handle 30, lever 53 is forced to rotate out of engagement from striker 24 and power spring 40 forces the striker downward. Swiss Patent No. CH 255,111 (Comorga A G) shows a high start staple gun with the handle linked to the power spring through a lever. There is no preload restrainer for the power spring so the spring stores minimal energy through the start of the handle stroke. Both references use a releasable link or release latch that is positioned behind the striker and de-linked by a direct pressing force from the handle. British Patent No. GB 2,229,129 (Chang) appears to show a high start stapler design. However, no functional mechanism to reset the striker is disclosed. Specifically, no linkage is described to lift the striker with the handle in a reset stroke. The lever 3 resembles a lever used in a low start stapler, but the lever does not lift the striker in any way. Instead, the striker is somehow lifted by a very stiff reset spring, yet no linkage is described to enable a reset spring to lift the striker against the force of the power spring.

SUMMARY OF THE INVENTION

In a preferred embodiment of the present invention, a high start, spring actuated stapler provides a compact stapler that combines enhanced handle travel for greater leverage with a separately movable spring/cage subassembly to preload the power spring. The cage may be pivotably attached to the housing at a location separate from the pivotable attachment of the handle. A striker alternates between an initial position above a staple track and a lower-most position in front of the staple track. A power spring is deflected to store energy by the motion of the handle. At a predetermined position of the handle, the striker is released to accelerate to the lower-most position by urging of the power spring.

The striker moves a minimum vertical distance required to drive staples while the handle, at a handle pressing area, moves substantially farther than the striker to achieve increased leverage and lower actuation force. According to various embodiments, a lever links the handle to a power spring or a spring/cage subassembly to provide the added leverage for the handle, and for added leverage in moving a release latch. According to a further embodiment, the handle includes a movable or slotted pivot attachment near a rear of the housing to provide enhanced travel at the front pressing area of the handle.

In various alternative embodiments, release mechanisms include a lever pivotably and slidably attached in the housing. The lever pivots out of engagement with the striker and slides rearward in a reset action. Further release mechanisms use separately movable latches. For example, a release latch is movably fitted in the housing and is moved out of engagement with the striker or power spring by urging from the lever. The lever does not directly contact the striker. A further embodiment release latch is urged out of engagement by contact with the handle. The various embodiment release latches may be mounted in front of or behind the striker. With the release latch in front of the striker, the power spring may pass behind the latch as the spring moves. The shape of the latch may thus be less constrained by a requirement to clear the power spring and possibly an associated lever. With the latch to the rear of the striker, the power spring can normally pass through a slot of the latch or beside the latch as the spring moves.

A reverse cantilevered reset spring may be integrated as part of a power spring. In one embodiment, the cantilevered reset spring is partially cut out of and formed integrally with the flat beam or bar type power spring. A benefit of this arrangement is that the high stiffness reset spring needs only a short leverage distance to provide a gentle reset force without distorting the main portion of the power spring.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 to 5show one preferred embodiment of a high start stapler. In the side elevational views ofFIGS. 1 and 2, one half of the body has been removed to expose the internal workings. In the some of the drawing figures, the base has been omitted for simplicity and clarity.

An upper body of the stapler including housing10is pressed against base50. Base50includes a staple forming anvil (not shown) to fold staples behind a stack of sheet media to be stapled, such as papers (not shown). Any of the staplers of the present invention may also be used as a tacker to install staples into a work surface if the base is rotated away or not used. Lever20provides a link between handle30and power spring80. Lever20is preferably an elongated U-channel having a rounded back end and an angled leading edge, but a simple flat plate may also be used. Handle30has an elongated ergonomic shape and is hinged at its back end against housing10at handle pivot29, considered the rear pivot location. Handle30also features handle pressing area33near its front end, which is the area where the user is expected to press down on the handle to operate the stapler most efficiently.

InFIGS. 1A and 5, a sharply angled release tip23at the end of lever20extends through striker100into slot109under edge102. Striker100is vertically movable through a striker travel path in striker slot11between an initial position at upper slot end11band a post-release, lower-most position at lower slot end11a. An upper end of striker100need not extend fully up to upper slot end11b. Release tip23therefore serves as a latch that holds striker100in the raised position against the downward bias of power spring80.

InFIG. 1, the initial position of striker100preferably locates lower edge106above track150and staples400. Pusher147under spring power urges staples400toward the front of the stapler. Tab or edge104, shown inFIGS. 1A,2A and5, engages spring tip82whereby power spring80biases striker100downward toward staples400. Lever20rotates within housing10about pivot15, which may be a rounded peg extending from the inside wall of housing10. Handle30includes handle link31pressing lever link26. In the preferred embodiment, handle link31is a curved, smooth surface attached or formed into the underside of handle30while opposing lever link26is a like curved, smooth surface formed into lever20. The opposed curved surfaces of links36,21engage each other and undergo rolling and sliding actions during movement of the respective handle30and lever20. The smooth and curved engagement surfaces ensure low friction therebetween. This area is considered the lever-handle link location. It is preferable that handle30and handle link31be made from a polymer such as nylon, Delrin, or polyolefin for their low friction and strength properties. Optionally, the interface may include a roller or lubricant. For example, one or both of links31and26may also be in the form of a low friction structure such as a roller.

As lever20rotates counterclockwise about pivot15from handle pressure, release tip23disengages from striker100as it moves from its position inFIGS. 1 and 1Atoward its position shown inFIGS. 2 and 2A. The release action occurs by the direct pivoting motion of lever20around pivot15, and is thus indirectly actuated by the downward motion of handle30. The area at pivot15is considered the front pivot location. The travel at the release area of tip23is small compared to the handle travel due to the proximity of tip23to pivot15versus the much greater distance from lever link26to pivot15. The latter distance directly affects the handle travel distance. Consequently, the frictional resistance encountered due to power spring pressure on striker100when release tip23slides out from under edge102is easily overcome by this mechanical advantage; i.e., handle30has great leverage to move tip23out from engagement. The added friction from the disengagement action is thus minimal.

This advantage contrasts with typical prior art high start releases where an element of the handle directly presses a restraining device used to hold the striker against spring bias. A large pressing effort on the handle is required to move the restraining device to release the striker when the element of the handle first contacts the restraining device.

Lever20preferably includes upper and lower tabs24that essentially pinch or confine a middle portion of power spring80to energize and deflect power spring80when lever20and power spring80move generally in unison in the substantially vertical direction and include any rotational component as well. Pinching tabs24further enable relative sliding or lateral movement between lever20and power spring80. Moreover, opposed central tabs24have a slight curvature to accommodate any bowing in the power spring during its deflection. The bowing in power spring80inFIG. 2is in the opposite direction as compared toFIG. 1, where potential energy is stored in power spring80inFIG. 2creating a strong downward bias via tip82upon striker100. The area of tabs24is considered the lever-power spring link location.

In the preferred embodiment, power spring80takes the form of a flat bar spring that has a generally uniform cross-section and overall rectangular shape. In various alternative embodiments, the bar spring may have varying cross-sectional shapes, sizes, and/or thicknesses in order to achieve the desired overall spring rate or stiffness k, a local spring stiffness in the section from between tabs24and release tip23, or a local spring stiffness in the section between tabs24and fulcrum16. Further, the power spring in an alternative embodiment may include, in a profile view, a kink or local bend to affect the spring rate at various positions of the handle travel. In yet another alternative embodiment, a coiled torsion spring may be used as the power spring wherein its helical coils are located near central tabs24or equivalent structure with its arms extending frontward and rearward.

With pinching tabs24, lever20can thereby move power spring80both downward and upward via pressing or lifting, respectively, at about spring tip82and flexing power spring80at tabs24. Other structures may of course be used to link lever20to power spring80. For example, the tabs may be replaced with pins or pegs sandwiching the power spring therebetween, or the power spring may include a tiny, laterally-extending ear that fits into a notch or hole formed in the lever. Through these structures, the up and down movement and any rotational action of lever20are transferred to power spring80. In the exemplary embodiment, as lever20rotates toward the position ofFIG. 2, power spring80bends or bows downward at the center as shown. Power spring80is supported at the rear end by fulcrum16and at the front end at spring tip82by edge104of striker100. InFIG. 2, power spring80is energized and striker100has been released to accelerate downward under urging of the power spring. Power spring80pivots at its rear on fulcrum16. Striker100accelerates down to its lower, post-release position shown inFIG. 3as power spring80re-assumes its rest shape in its generally lower position ofFIG. 3.

Optional absorber17limits the lower-most travel position of striker100and power spring80. Absorber17is preferably made from a resilient material such as rubber, polyurethane, nylon, felt, foam, or the like. Absorber17as shown receives the remaining striker inertia and energy from power spring80after the staple has already been expelled by the striker blow, or particularly when no staple is present. In various alternative embodiments, absorber17may be positioned in front of striker100engaging spring tip82or a tab of striker100instead.

Lever20is in substantially the same position inFIGS. 2 and 3. InFIG. 3, striker lower edge106has come to a stop proximate to lower slot end11a, while striker100is now located in front of track150in the striker lower-most position. Still inFIG. 3, the front-most staple400has already been expelled and driven into the sheet media as a result of the impact blow by striker100. Other staples400remain situated on track150.

Reset spring70biases the back end of lever20upward. In particular, the upper end of an arm of reset spring70presses on hole27or like anchor in lever20to pivot lever20clockwise inFIG. 3about pivot15. Reset spring70is preferably a single or multiple coil torsion spring with outstretched arms at each end. A compression spring or a bar spring may also be used in place of or in combination with the coiled torsion spring.

Lever20interacts with its surrounding components such that handle30has enhanced leverage upon spring80. For example, the location where handle30presses lever20, at respective links26and31(the lever-handle link location), is preferably located between tabs24(the lever-power spring link location) and handle pivot29(the rear pivot location). Handle pressing area33may move generally vertically through a handle travel distance that is substantially greater than the distance tabs24or handle link31moves during deflection of power spring80. Handle30, when pressed near pressing area33, therefore has enhanced leverage to move lever20and to energize power spring80. This provides great work advantage over the prior art.

In an alternative embodiment inFIG. 11, reset spring70may press upon power spring80or cage90to bias the front of the cage and/or spring upward, discussed later. In still another alternative embodiment (not shown), reset spring70may press handle30upward. In this embodiment, handle link31may have a tensile connection to lever20so that handle30can pull lever20, and any items linked to the lever, upward. Also, more than one reset spring70may be used in the assembly. For example, a first reset spring may bias handle30while an optional, second reset spring may bias lever20, power spring80, and/or cage90upward.

FIG. 4shows a reset position of the assembly. In this view, power spring80pivots upward, counterclockwise about fulcrum16. Through its link to power spring80, striker100moves up to contact release tip23and lever20generally slides rearward along elongated slot22containing pin15. Once lever20has moved away from the path of striker100, striker100has room to be translated upward to its initial, high-start position in front of lever20. Reset spring70, or the alternative structures discussed above, provides the bias for the upward reset action of lever20and power spring80. At the end of the reset action, the assembly assumes the configuration shown inFIG. 1.

In the reset action ofFIG. 4, angled rib18formed from or attached to housing10presses lever20to urge release tip23of lever20toward striker100. Angled rib18may contact lever20directly or a portion of the upper end of reset spring70near hole27. Release tip23then moves under edge102of striker100as shown inFIG. 1A. Slot109inFIG. 5is preferably shaped like an inverted “U.” This shape corresponds to a preferably U-channel shaped lever as shown inFIG. 5. Slot109extends down to lower edge103, as seenFIGS. 1A and 5. This extension space in slot109provides clearance for the extended, angled, front edge of the U-channel-shaped lever20. The angled, front edge of lever20forms a cam to allow striker100in its upward movement simultaneously to force lever20rearward during the reset stroke, as depicted in the change fromFIG. 3toFIG. 4. Alternatively, striker100may include a forward, angled segment (not shown) to slide along the front of lever20. Other shapes may be used for lever20and slot109, including a flat formed lever and linear slot.

FIGS. 6 to 10show a further embodiment of the present invention. InFIGS. 6 and 7, a front area detail of a stapler is shown. The remaining structures not appearing in theFIGS. 6 and 7are comparable to the embodiment shown inFIGS. 1-4. Release latch60holds striker500in the raised initial position as seen inFIGS. 6 and 6A. Release latch60, as best seen inFIG. 9, is preferably a separate, discrete part from lever20a. Release latch60pivots about outstretched wing-like tabs65, where wing-like tabs65are pivotably supported in housing10by means known in the art. Hooked tabs67of release latch60extend through respective slots502of striker500, as best seen inFIG. 8. Hooked tab67includes flat shelf61transitioning into chamfer62.

Release latch60is lightly biased toward striker100by a resilient member such as a spring, rubber or polyurethane foam padding, felt strip, spring clip, rubber bumper, etc. (not shown) positioned in front of latch60. In the case that housing10is constructed of a plastic material, the resilient member is preferably a cantilevered post extending from the interior of housing10pressing release latch60near the free distal end of the post. According to this embodiment, there is no need for an additional component to bias latch60.

InFIGS. 6 and 6A, the stapler is in an initial position. As handle30is pressed downward, lever20arotates about pivot15a. Pinching tabs24aforce power spring80to bow downward at the tabs while becoming angled upward near the tip as shown inFIG. 7. Power spring80presses striker500at slot508. Striker500in turn presses shelf61of release latch60at slot502. As lever20arotates counterclockwise about pivot15ainFIG. 6, bottom corner21of lever20amoves toward hooked tabs67, engages hooked tabs67, and pushes hooked tabs67out of slots502of striker500. This instantly releases striker500for its downward travel for an impact blow with a staple. In an alternative embodiment, lever20amay continuously engage hooked tabs67of release latch60through the motion of lever20aincluding the release action. More precisely, at a predetermined position as seen inFIG. 7A, shelf61of release latch60shifts out of striker slot502and striker slot502then presses chamfer62. The unstable angled engagement of striker slot502against chamfer62causes the downward biased striker500to force hooked tab67entirely out from slot502. Striker500is then released for its downward travel for an impact blow with a staple.

The striker release point is therefore when shelf61of release latch60just exits slot502in striker500and chamfer62makes contact with striker500. Thus, the location of hooked tab67where chamfer62meets shelf61is a release area of the latch. According to this structure, lever20aand release latch60can be on opposites sides of striker500, while lever20acan disengage latch60from striker500without lever20aextending into the thickness of striker500or into the striker travel path defined by slot11.

On the other hand, if chamfer62is omitted, then shelf61forms a simple corner on hooked tab67. Then lever20aat bottom corner21must pass into slot502to force shelf61to exit striker slot502. This structure could function if lever20awere slidable in housing10, but could cause lever20ato interfere with the downward movement of striker500. Also, release latch60may optionally be oriented oppositely where tabs65are at a bottom area below tab67. Other pivotable or movable mountings may be used in place of release latch60. Furthermore, release latch60has a U-channel shape as shown inFIG. 9, or may have a flat bar shape engaging a central portion of striker500or like configurations. For example, a flat latch may resemble one of the sides of latch60, wherein a bar includes a hook extending from the bar. To create hooked tab67of release latch60, the structure may be a lanced, bent or angled, or tab punched from a flat metal blank.

The features of chamfer62and shelf61need not be immediately proximate. Rather, they may be at separate locations of latch60. For example, a tab including only chamfer62may extend through a slot of striker500, while a tab including shelf61extends through a separate slot of striker500.

Bottom corner21of lever20amay push release latch60entirely out of striker slot502. In one embodiment (not shown), the release latch may extend around striker500, in the side direction inFIG. 8rather than through slots502. The release latch would be wider. Then lever20acould press the release latch out of engagement with the striker by passing to the side of striker500. Striker500can translate downward without interference from lever20a. In this example, a tab that is pressed by lever20ais remotely positioned from the feature that holds striker500in its upper position.

In yet another alternative embodiment, lever20amay include a slot (although not shown inFIG. 6) containing pivot15atherein, similar to the elongated slot22containing pivot15inFIG. 4. Lever20acan then slide rearward out of the way under the force of the spring biased striker500. Release latch60may be mounted behind striker500whereby pivoting lever20acauses latch60to disengage striker500. In this instance, pivot15amay be located near a bottom, front of lever20aso that the top corner of the lever can pull the release latch out from engaging striker500. Other like structures may be used to release a latch that is behind striker500.

InFIG. 10, striker500has been released and is depicted in its lowest position. Release latch60is angled away from striker500with hooked tab67gently pressing striker500. During a reset stroke, a reset spring operates similar to reset spring70inFIGS. 1-4, or according to the other options discussed herein, to return the components back to their initial positions. In the reset stroke, striker500moves upward and slides gently against hooked tab67. Striker slot502moves up with striker500and eventually aligns with hooked tab67. At this moment, hooked tab67becomes trapped within striker slot502and holds striker500in its initial position. The reset position of the stapler is generally precise as hooked tabs67can be precisely located within housing10.

FIGS. 11 to 13show stapler structures that provide a preload to power spring80. A striker latching mechanism to hold striker500in the pre-release position ofFIG. 12is not shown for simplicity. Various latch designs as disclosed may be used. In the previous drawing figures, power spring80is unloaded or unstressed in its upper rest position or shape. It is also substantially unstressed in the post release rest position. Yet there may be some load upon the power spring if the handle continues to move after release, or other geometries are intentionally selected to provide such additional deflection. It is desirable, however, to preload the power spring so that it can store energy through the full stroke of handle30.

FIGS. 11 and 12show a subassembly of power spring80and cage90used with representative components from the embodiment ofFIGS. 1-5by adding cage90. Cage90confines power spring80so that the power spring cannot relax to its free position. More precisely, cage90holds power spring80to pre-stressed upper and lower rest positions. InFIG. 13, handle30and lever20have been omitted for simplicity. Cage90includes rear tab91, center tab93, and front tab92; rear tab91and front tab92support the front and rear ends of power spring80from the bottom while center tab93presses down in a middle area of power spring80. These confining tabs91,92,93thus pre-stress power spring80without any input from handle30or lever20. Tabs91,92,93may have other geometries or surfaces of cage90near the respective rear, front, and center locations of power spring80.

To further enhance pre-stressing of the power spring, it is contemplated in an alternative embodiment (not shown) to provide a flat, elongated power spring similar to that shown inFIGS. 11-13, but which already has a bowed profile in its free state. Thus, placing the bowed power spring into the confining tabs91,92,93in a state of bending opposite to the natural, bowed shape increases the amount of pre-stress in the power spring. Moreover, the flat spring may have different thicknesses along its length to change its local spring rate k, for example, to decrease spring stiffness near striker500by decreasing thickness or width in that area, and/or to increase thickness and spring rate k near a center section so the spring may more efficiently store energy along its entire length. In this example, the spring stiffness corresponds to the bending stress upon the spring at the different locations of the spring.

Tabs24press the cage/spring subassembly to deflect power spring80to an energized position. Tabs24may be part of lever20, or optionally tabs24may be part of handle30where tabs24are instead non-tab-like structures such as flat portions, recesses, etc. Accordingly, lever20or handle30may press power spring80directly as shown or indirectly via cage90. Either pressing method provides generally equivalent deflection and energizing of power spring80.

In the initial position shown inFIG. 11, both cage90and power spring80are in an uppermost position at their respective front ends. In the pre-release position ofFIG. 12, power spring80is deflected and energized remaining in the upper position at tip82while cage90pivots or angles downward at tab92. This corresponds to the position ofFIG. 2orFIG. 7without the cage element. In the released position ofFIG. 13, power spring80at tip82, cage front at tab92, and the cage/spring subassembly are in their lowest post-release rest positions. InFIG. 13, the front of cage90has pivoted to cause the cage to be angled downward with respect to the cage position ofFIG. 11.FIG. 13corresponds toFIG. 3or10. In the context of preloading the power spring, the rest position is the shape of the spring when the spring has not been deflected or energized from its pre-loaded shape against cage90. The upper and lower rest position or shape may also describe the position or shape of a subassembly of the power spring and the cage when the power spring is not deflected.

When lever20or handle30presses power spring80directly, cage90becomes loosely fitted in the assembly. For example,FIGS. 16-19show a further embodiment with a handle optionally pressing the power spring directly.

Returning toFIGS. 11-13, cage90can pivot near the rear end at contact94located optionally near tab91, to swing the front end. Pivoting contact94is separate from handle pivot29to provide one method that cage90is separately movable from handle30. Optionally, cage90may be translatable in the housing rather than pivotably mounted as shown. If lever20or handle30presses cage90rather than power spring80, then the cage is more confined from moving. In either case, cage90can move separately from handle30since cage90is not an attached element of handle30.

Pressing area38of handle30is positioned generally above striker500. In the example ofFIGS. 11 and 12, pressing area38moves downward through a “handle travel” about twice the distance of what the front end of cage90moves down near tab92and striker500. Handle travel is the distance the pressing area moves as the power spring is deflected. According to this feature of the present embodiment, a high start spring powered stapler is very compact in its height since the “striker travel” is the minimum necessary from just above the staple track to in front of the staple track. At the same time, the handle is not rigidly fixed to the preloading features of cage90, tab92in this example, and lower post191in the example ofFIG. 14. Described another way, neither tab92nor lower post191is an element or component of handle30or130in the preferred embodiments. Therefore, handle movement can be enhanced through linkages as disclosed herein for increased leverage and lower pressing force while the restraining device of the cage moves minimally to follow the compact striker action.

In prior art designs, a restraining device preloads a power spring near the striker. Typically, the restraining device is rigidly linked to the handle, being a part of the handle assembly. For example, U.S. Pat. No. 4,463,890 (Ruskin) at column 4, line 15, discloses a restrainer end portion 42c′ that pre-biases the power spring44. Restrainer 42cdepends from inside the handle as part of an inner frame or shell 42 and moves directly with the handle. Because of this rigid connection, the handle of Ruskin '890 cannot travel more than the travel of restrainer 42cand beneficial leverage is lost.

In typical light duty desktop staplers, the striker needs to move not more than about 0.5 inch to clear and eject staples. Any more vertical motion requires a housing or body to be taller than necessary to fit the highest striker position. Therefore, with a handle-linked restrainer as shown in Ruskin '890, the handle cannot move more than 0.5 inch and still be contained in a compact design near the front end or pressing area of the handle. Such limited handle travel thus restricts prior art designs to a lower leverage, higher actuation force operation. Heavier duty staplers have proportionately even greater minimum striker travel to clear the taller staples. On the other hand, the increased handle travel with respect to the striker and cage of the present invention allows a compact housing with no restriction on the available handle leverage.

FIGS. 14 and 15show, in simplified schematics, an alternative embodiment cage and torsion spring subassembly. Power spring185has a helical coil configuration and includes parallel, forward-extending arms. Handle130is pivotably attached to housing110at pivot139. Pivot139is separate from pivot194about which cage190rotates. Handle130links to power spring185through lever120at tab or link121. Specifically, the transfer of applied force starts from the user's hand to handle130to lever120to link121to cage190to power spring185. As seen inFIG. 15, release latch160is actuated directly by force from handle130applied at cam132against latch surface162rather than by lever120. Release latch160is movably supported at its bottom at recess161, and near its top holds striker150in place by latch tab163extending into slot153of striker150to resist the downward pressure applied by power spring arm189on striker150. The downward bias is produced by lower spring arm189acting downward on slot152of striker150. In an alternative embodiment, a tab of the striker may engage a slot in latch160. Optionally, lever120may actuate latch160by methods discussed above.

Lever120rotates about point122. Cage190rotates about point194. Upper post192and lower post191confine upper spring arm187and lower spring arm189respectively in the upper rest position ofFIG. 14. On the other hand, in the pre-release position ofFIG. 15, lower post191moves down away from lower spring arm189which is still trapped in slot152of striker150. After release, striker150and lower spring arm189accelerate downward until lower spring arm189contacts or is near to lower post191. Power spring185is at this moment confined again by cage190in a lower rest position of the power spring. Posts191and192may take other forms aside from the pegs as shown, such as tabs, slots, holes that the spring arms may hook into, etc.

In both embodiments disclosed above, cage90for use with elongated spring80inFIGS. 11-13, and cage190for use with torsion power spring185inFIGS. 14-15, the cage is indirectly moved by the handle. A lever provides an intermediate linkage so that the cage front end, adjacent to the striker, moves less than a pressing area of the handle immediately above the striker. The effect of this structure is that the handle can travel more than the amount of striker travel through a stroke that deflects the power spring. A vertically compact housing10or110fits the minimally moving striker, while the handle travel is larger for greater leverage and thus lower actuation force than a handle that is restricted to moving the same distance during spring deflection as the striker moves upon ejecting staples.

FIGS. 16 to 19show a still further embodiment. As in some of the foregoing drawings, the stapler base is not shown for simplicity. Handle230moves separately from cage190a. The handle travel at pressing end235is enhanced without the use of an intermediate lever to link striker140to handle230. Handle230links directly to the subassembly of cage190aand power spring180.

A modified pivot design between handle230and housing110provides the enhanced leverage of handle230. A power spring and cage subassembly are shown inFIG. 19. InFIG. 16, the stapler is shown in an initial position. Power spring180is in an upper rest position pre-stressed against cage190a. Handle230is in its high or highest position. Cage190apivots about fulcrum or mount16of housing110and is angled upward toward the front. In an alternative embodiment, cage190amay be loosely attached (not shown) at its rear end while power spring180is pivotably held in housing110. Spring front tip182of power spring180extends through slot143of striker140. Spring front tip182further extends through slot263of release latch260. Slot263may equivalently take the form of a top edge of latch263. Release latch260is pivotably attached at recess261in front of striker140, and is gently biased by a resilient member (not shown) to engage spring front tip182. Release latch260may optionally be located behind striker140as seen in the plan view ofFIG. 19a. In the embodiment ofFIG. 19a, release latch260at slot263′ moves rearward to disengage from shoulders184of spring front tip182. In yet another alternative embodiment (not shown), release latch260extends through an opening of power spring180and releases from an edge of the opening rather than the outer shoulders184.

In theFIG. 17embodiment, when handle230is rotated downward to the end of its handle travel, power spring180is deflected to its energized state. Cam232extends from underneath handle230and has a sloped leading edge. After a predetermined amount of handle travel, the sloped leading edge of cam232engages and forces release latch260out of contact with spring180, preferably by pressing lead-in surface262, which is a curved extension of release latch260. Once front tip182of power spring180disengages from release latch260, which has now been pushed away by cam232inFIG. 17, power spring180is free to press down on striker slot143and accelerate striker140downward into staples400below. The impact blow of striker140against staple400ejects the staple from the stapler.

Cage190aflips or angles downward inFIG. 17from its initial position inFIG. 16, rotating near rear end191aabout fulcrum16. In an alternative but functionally equivalent embodiment, cage190amay move downward at both ends (not shown) to become loose at both ends in the pre-release condition ofFIG. 17. If power spring180is pivoted within housing110near rear end191a, the effect is comparable to a pivoted cage rear end since the cage rises up after release back to the position ofFIG. 18by pivoting about fulcrum231. Handle fulcrum231is preferably a projection extending from underneath handle230and terminating in a rounded, pivot point. In the exemplary structures ofFIGS. 16-18, there is minimal space under rear end191aof the cage, so any vertical movement at the rear end would be negligible.

InFIGS. 16-18, the pivot point of handle fulcrum231presses directly upon power spring180; the rounded tip allows handle230to rock and slide laterally on power spring180. Cage190ais loosely contained inFIG. 17. Front end192aof cage190acan freely move up until a top edge of the cage touches power spring180. Optionally, handle fulcrum231may press upon cage190a, on or near tab193aor other location of cage190a. In either case, cage190amoves separately from handle230thus improving leverage as discussed earlier.

InFIG. 18, power spring180has moved down to cause the cage/spring subassembly to assume its lower rest position. A front-most staple400has been ejected. In a desktop stapler, the ejected staple would have pierced and be bent behind a stack of papers after being deformed on an anvil (not shown). In the reset stroke, the cage/spring subassembly, along with striker140, moves back to the position ofFIG. 16. The advantage of the separate movement of the handle and cage are apparent from previous discussions, and are further dramatized in the following description.

In the embodiment depicted inFIGS. 16-18, handle230at its back end has a pivot location that moves relative to housing110. Specifically, handle230has a guide slot233that is captured by guide post13extending from housing110. Of course, the slot may be formed in the housing while the post is part of the handle. Guide slot234has a generally linear shape and is located proximate to post116. As handle230rotates downward toward the position ofFIG. 17, the curved-shape guide slot233enables the rear end of handle230, proximate to slot233, to move upward and forward with respect to housing110. InFIG. 17, curved guide slot233has guided handle movement at its rear end upward and forward via cam action at guide post13as the handle rotated. FromFIG. 16toFIG. 17, handle230at straight guide slot234has translated upward around post116.

For comparison of handle movement, handle230′ is shown in phantom inFIG. 17. Handle230′ represents the position of the handle if there were no cam action—that is, if guide post13were not present and straight guide slot234were a simple hole. Then handle230′ would pivot about guide post116at the fixed pivot location ofFIG. 16. InFIG. 17, it is seen that pressing area235on handle230moves farther with the cam action than pressing area235′ (phantom) on handle235′ without the cam action. In both instances, the cage/spring subassembly and the power spring deflection are in the same position and are pressed by fulcrum231,231′ extending from handle230,230′.

It follows then that handle230, at pressing area235, moves farther thus creating increased leverage when the cam action enables the rear end of handle230to rise. Under common physical principles, leverage is directly proportionate to the handle travel, all other things equal. Because of the greater handle travel at the pressing area in the embodiment ofFIG. 17, a lower pressing force therefore results with the cam action. Optionally, one or both of posts13and116may be roller linkages or other low friction engagements including recesses to fit extensions of handle230. Furthermore, handle230may include posts or recesses to engage cam slots or ribs of housing110. Other intermediate structures may provide a movable pivot linkage at the rear of handle230.

Cage190aand power spring180move in direct relation to striker140since power spring180is directly linked to striker140. In an alternative embodiment, handle230may be pressed even farther inFIG. 18to move cage front end192adown past the lower rest position, for example, to contact the housing rib shown just below cage front end192ainFIG. 18. By such extreme travel, the cage front area has even greater clearance from power spring180. A minimal amount of such clearance may be desired to prevent impact upon cage190aby power spring180. However, this clearance should be minimal since the handle is only forced slightly back up under the bias of the power spring to return the cage/spring subassembly back to the rest condition. This extra deflection of the power spring requires energy input to the power spring that is lost upon rebound of the handle and does not provide useful staple driving power.

In describing the movement of the cage/spring subassembly and the pivotably-slidably-linked striker140, it is intended to include the distance between the upper rest position ofFIG. 16, or equivalent rest position inFIG. 11, and the lower rest position ofFIG. 18, or equivalent position inFIG. 13. These distances are also considered as the striker travel.

According to an earlier example, striker140moves a striker travel of about 0.5 inch from its initial position above track150inFIG. 16to the lower-most position in front of track150inFIG. 18in an exemplary, compact desktop stapler. The cage/spring subassembly travels about the same distance near striker140between upper and lower rest positions. Handle230, at pressing area235, moves about twice that distance or about 1 inch. This is a 2-to-1 leverage ratio of handle travel to power spring/cage subassembly front end motion, or striker travel. Other leverage ratios may be achieved depending on the configuration of the cam action, or the sizing of the levers of the previous embodiments. As discussed earlier, the levers shown in many of theFIGS. 1 to 15provide an enhanced handle-travel-to-striker-travel relationship similar to that ofFIGS. 16 to 18by allowing the spring/cage to move separately from the handle.

FIGS. 16-18depict one exemplary embodiment of a power spring/cage subassembly. Staples400are held in a track chamber and supported on a feed track (not shown).FIG. 19is a plan view of the power spring/cage subassembly. In this exemplary embodiment, a reset spring is integrally formed from the same material as power spring180. Specifically, resilient spring arm183acting as the reset spring is formed as a partial cut-out at the back end of power spring180. Resilient spring arm183presses anchoring rib12extending from housing110. Spring arm183is part of a rearward extension of power spring180beyond fulcrum16.

As seen inFIG. 19, spring arm183is cantilevered from a base formed in power spring180and located well to the rear of rib12. Spring arm183extends toward fulcrum16and is spaced from the fulcrum post16by the distance denoted as “Re-set Spring Leverage” inFIG. 19. The inherently high spring force of the stiff spring material selected for power spring180operates over a short distance to produce a low reset torque. When spring arm183is preloaded to press upon rib12in the upper rest position ofFIG. 16, spring arm183does not move greatly as the central portion of power spring180is deflected to the position ofFIG. 17, so the reset torque does not change greatly. It can be seen that spring arm183is only slightly different in shape betweenFIGS. 16 and 17, and that spring arm183has no substantial effect on the overall shape or profile of power spring180. The result of this structure is that spring arm183provides a gentle bias to move front end182of power spring180upward toward the initial power spring position ofFIG. 16to reset the mechanism of the stapler.

FIG. 20shows an alternative embodiment torsion power spring180ahaving a helical coil with oppositely extending arms. Front end182aof power spring180aengages the striker (not shown inFIG. 20). Fulcrum16supports the rear end of power spring180a. Rib12presses forward-extending distal end183ato provide the reset function as described above with respect to spring arm183ofFIG. 19. A cage (not shown) similar in design to cage90ofFIG. 11may preload torsion spring180aby supporting the central coil and the front and rear ends. Therefore, a torsion spring such as that shown inFIG. 20may be used in any of the embodiments disclosed herein. In various alternative embodiments, the torsion spring may have arms extending in various directions, including parallel to each other as inFIG. 14or opposite to each other as inFIG. 20. The cage design can be configured by those skilled in the art to accommodate the particular power spring design, whether bending or torsion, to provide a preload upon the power spring and allow further deflection of the power spring.

InFIG. 19, fulcrum231is optionally pressing directly on power spring180as discussed earlier. Power spring180is a flat spring that optionally includes varying cross-sections for efficient function. Central cage tab193aextends from under power spring180through the opening shown inFIG. 19to hook the power spring from above. Rear end191aand front end192aof cage190apress against power spring180from below. With this arrangement, power spring180and cage190acan be readily assembled to form the preloaded spring/cage subassembly. The subassembly is separate from handle230and does not exert any preload force upon the handle. As a result, the subassembly can be easily inserted into the main stapler assembly including housing110before or after handle230is installed.

The resilience of power spring180, or any other similar power spring, is preferably stiff to provide staple driving power. In the preferred embodiment, the flat bar power spring180should provide a peak force acting on the striker of between about 10 to 20 lbs. for a standard desktop stapler. Heavy duty staplers or staple guns require substantially more force, up to about 50 lbs. for example. Such stiff material is normally not compatible with the light force required for a reset spring since the reset spring serves only to reposition and restore the moving parts within the stapler to their pre-fire condition.

For instance, in Swiss Patent No. CH 255,111 (Comorga A G), a rear distal end of a power spring provides a reset function. However, the main portion of the power spring is greatly deflected in the process as seen by the shape of the spring near post5ofFIG. 1. This large deflection is caused by the rear distal end of the spring moving a large distance as the central operating portion is also deflected. The reset spring thus behaves with much greater stiffness than is needed, effectively acting as two power springs that are deflected while only one provides useful driving power. The exemplary embodiment ofFIGS. 16-18avoids this problem.

InFIGS. 16-18, release latch260disengages from front end182of power spring180. As seen inFIG. 17, front end182is angled upward in the pre-release position as compared to the upper rest position ofFIG. 16. This increased angle provides a bias in front end182that urges disengagement from release latch260at slot263. The angle of front end182may be selected so that there is just enough friction to prevent release latch260from being unstable and accidentally sliding off of front end182. From empirical observations, the angle of front end182ranges preferably from about 2° to about 15° from the horizontal, inclusive of the outside limits. Then a light force applied by cam232forces release latch260to disengage. Accordingly, the extra force required to actively disengage release latch260is reduced as compared to a conventional, non-angled spring end.

In an alternative embodiment (not shown), a passive release mechanism may purposely provide that the angle of spring end182is large enough that release latch260is unstable and tends to slide out from under power spring180in the pre-release position ofFIG. 17. Then cam232extends farther downward (not shown) and, under normal operation, abuts release latch260to prevent it from moving. At the pre-release position ofFIG. 17, the extended cam232moves out of engagement with release latch260allowing the unstable release latch to disengage from power spring180and/or striker140.

In yet another alternative embodiment, a lever (not shown) may normally engage release latch260and upon urging by handle230, the lever disengages from release latch260at the pre-release position of the handle to allow the release latch to slide out from under power spring180when the release latch engagement against power spring180or striker140becomes unstable. The foregoing passive release designs may be applied to a release latch fitted behind the striker wherein the release latch may move toward the striker for release.

FIGS. 21 to 23show a further embodiment of a passive release design according to the two preceding paragraphs. The components are shown schematically in a detail of the front portion. Further operating elements may function as shown inFIGS. 11-20or equivalently. Cage190aincludes front end192ain an example as shown using these parts fromFIGS. 16-18, although other mechanisms may be incorporated to actuate a power spring and striker. Power spring180includes front tip182at which the power spring is pivotably linked to striker140, for example, through an opening in striker140. Striker140is slidably fitted in housing112at guide111. Latch360is pivotably or movably mounted in the housing at mount261.

In the rest position ofFIG. 21, latch360is tilted toward striker140whereby spring tip182extends through opening363of latch360to form a releasable engagement between latch360and striker140. Latch360may engage power spring180or striker140by other engagements as discussed earlier. For example, inFIGS. 14 and 15the latch releasably engages the striker directly. As handle330is pressed toward housing112, power spring180is deflected to bend as inFIG. 22, in a manner similar to that described forFIG. 17. In the present case, spring tip182becomes angled enough that the engagement to latch360is unstable. Specifically, inFIG. 22, latch360moves forward as shown under the angle and bias of power spring tip182. Near to the start of the pressing stroke from the rest position, spring tip182is less angled so latch360is inherently stably engaged to striker140. Alternatively, the latch-to-striker engagement may be unstable for all positions. For example, latch tab163ofFIG. 14may be angled to urge latch160forward as striker150is forced downward.

To hold unstable latch360to striker140and power spring180, cam505selectively or releasably obstructs motion of latch360. Cam505extends into opening113of housing112. Stop face503of the cam presses or contacts latch360to prevent the latch from moving out of engagement with striker140. As discussed earlier, latch360or equivalent structure may be positioned behind striker140. Then cam505may also be behind the striker. Cam505is movable in housing112against bias of resilient tab115. Optionally, cam505may include an internal resilient portion between a fixed lower portion and a movable upper portion. The resilient action biases cam505toward the rest position ofFIG. 21. Cam505is exposed at opening113whereby handle330can press upon cam505at cam actuating surface504.

As seen inFIG. 22, cam505has been pressed into housing112by extension332of the handle until the cam aligns with shelf114. Cam505is then free to move forward into a recess of the housing. Latch360is likewise free to move forward and disengage spring tip182. Striker140and power spring180move to the lower position ofFIG. 23to eject a staple400. Cam505includes chamfered or angled face501to provide a light bias for cam505to move downward as the cam is pressed against a corner of shelf114by latch360. The angle allows cam505to move very slightly forward or away from latch360as the cam is pressed downward while the motion is not enough to cause a release action. The angle is great enough to assist handle330in pressing cam505, but shallow enough that friction between the cam and surrounding parts does not allow the cam to spontaneously move. Cam505is preferably made from a low friction material such as acetal plastic, or otherwise lubricated.

Other structures or variations upon cam505may be used to hold latch360selectively or releasably engaged with striker140/power spring180. As described earlier, a passive release design may hold a latch engaged with the striker/power spring assembly through an attached part of handle330, for example, an elongated cam or extension332that normally contacts latch360to hold the latch engaged. Or a separately movable part such as cam505or other equivalent lever structure may provide an intermediate link between handle330and latch360, with the intermediate structure selectively held in a rest position by slight friction, detent or other holding action against the surrounding components. The cam or lever may include sliding, translating, and/or pivoting motions in housing112. As shown inFIGS. 21-23, cam505includes various such motions.

The actuating force required upon handle330is primarily determined by the stiffness of spring180as long as frictional losses are minimized. As described above, the force required to move cam505is minimal. The embodiment according toFIGS. 21 to 23has minimal sliding between components, and minimal disengagement force. There are generally few sliding movements in the action as power spring180is energized. For instance, cage190amoves within housing112but does not rub or significantly slidably press other elements as it moves.

When the handle directly, or through an intermediate link, causes the release of the striker by an action of the handle near the distal end of the handle, as shown inFIGS. 14 to 23, the release is relatively precise with respect to handle position. Specifically, the release can be controlled to be precisely near the lower most travel position of the handle since the release is directly tied to the handle position. The latest possible release provides improved performance since the housing has no opportunity to bounce up in a kick-back action.

It is understood that various changes and modifications of the preferred embodiments described above are apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present invention. It is therefore intended that such changes and modifications be covered by the following claims.